Digestive (GI) System (Gastrointestinal System) Gastro = stomach 1

Digestive (GI) System Digestive (GI) System (Gastrointestinal System)(Gastrointestinal System)

Gastro = stomachGastro = stomach

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FunctionsFunctions

– INGESTIONINGESTION Taking food in by mouth Taking food in by mouth– DIGESTIONDIGESTION to break food down into simple to break food down into simple

moleculesmoleculesMechanical: Mechanical: churning of food in the stomach, churning of food in the stomach, manipulation of food with tongue, tearing and manipulation of food with tongue, tearing and grinding with teeth.grinding with teeth.

Chemical: Chemical: breakdown of food with hydrochloric breakdown of food with hydrochloric acidacid

– ABSORPTIONABSORPTION nutrients enter capillaries nutrients enter capillaries – DEFECATION DEFECATION to eliminate solid waste to eliminate solid waste

products products 22

Digestive Digestive OrgansOrgans

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Regional TermsRegional Terms

Upper GIUpper GI– Stomach and areas superiorStomach and areas superior

Lower GILower GI– Areas inferior to the stomachAreas inferior to the stomach

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Abdominal Quadrants

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Peritoneum and MesenteriesPeritoneum and Mesenteries

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Peritoneum and MesenteriesPeritoneum and Mesenteries

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OMENTAOMENTA

The liver is suspended by a mesentery The liver is suspended by a mesentery called the OMENTUM.called the OMENTUM.There are two omenta: greater and There are two omenta: greater and lesser.lesser.GREATER OMENTUM is flat, and is in GREATER OMENTUM is flat, and is in front of the intestines like an apron. Its front of the intestines like an apron. Its function is to store fat, especially in function is to store fat, especially in men. men. LESSER OMENTUM is smaller.LESSER OMENTUM is smaller.

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Mesenteries

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PERITONEAL CAVITYPERITONEAL CAVITY

Why is this important? The peritoneum Why is this important? The peritoneum divides the abdominal cavity into three divides the abdominal cavity into three distinct regions:distinct regions:


INFRAPERITONEAL CAVITYINFRAPERITONEAL CAVITY (inferior to (inferior to peritoneum)peritoneum)

RETROPERITONEAL CAVITYRETROPERITONEAL CAVITY (posterior (posterior to it)to it)

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This is clinically important because if you tear This is clinically important because if you tear something in the GI tract (ruptured appendix), something in the GI tract (ruptured appendix), bacteria go out into the peritoneal cavity, affects bacteria go out into the peritoneal cavity, affects all the organs there, which is the entire GI tract.all the organs there, which is the entire GI tract.

Bleeding in the kidney will accumulate in the Bleeding in the kidney will accumulate in the retroperitoneal cavity. retroperitoneal cavity.

Infection in the urinary bladder doesn’t affect the Infection in the urinary bladder doesn’t affect the peritoneal cavity. peritoneal cavity.

Bleeding and infection are confined to one Bleeding and infection are confined to one compartment.compartment.

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MouthMouth

Oral CavityOral Cavity– Hard and Soft PalateHard and Soft Palate

TongueTongue– Lingual FrenulumLingual Frenulum

Salivary GlandsSalivary Glands– Parotid, Submandibular, SublingualParotid, Submandibular, Sublingual

TeethTeeth

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ORAL CAVITYORAL CAVITY

Lined by non-keratinized stratified Lined by non-keratinized stratified squamous epithelium. The transition squamous epithelium. The transition between the skin (keratinized) and the between the skin (keratinized) and the non-keratinized area is the LIPS. You non-keratinized area is the LIPS. You can see what happens when they dry can see what happens when they dry out; becomes cracked.out; becomes cracked.

– PALATEPALATE (ROOF of mouth) (ROOF of mouth)HARD PALATEHARD PALATE: bone: boneSOFT PALATESOFT PALATE: soft tissue (can feel with tongue : soft tissue (can feel with tongue on roof)on roof)

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Mouth

Figure 22.8a15

TONGUETONGUE

Your tongue is the only muscle in your body that is attached at only one end.

The tongue is all muscle, but it is different than all ll muscle, but it is different than all other muscles of the body, where the fascicles other muscles of the body, where the fascicles are arranged in a particular order. are arranged in a particular order.

The fibers of the tongue go in all directions, and have The fibers of the tongue go in all directions, and have no fascicles no fascicles good ROM. good ROM.

Some people can curl tongue, others can’t. Some people can curl tongue, others can’t. The The LINGUAL FRENULUM LINGUAL FRENULUM is the flap of skin under is the flap of skin under

the tongue at the midline. If it is too short, it limits the tongue at the midline. If it is too short, it limits mobility, called tongue-tied. Treatment is to cut it.mobility, called tongue-tied. Treatment is to cut it.

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Figure 22.8b1717

SALIVARY GLANDSSALIVARY GLANDS

Produce salivaProduce saliva– Names of some salivary glands:Names of some salivary glands:

Parotid (largest). Mumps is a virus that attacks here.Parotid (largest). Mumps is a virus that attacks here.

SubmandibularSubmandibular

SublingualSublingual

– Functions of salivary glandsFunctions of salivary glandsTo moisten food so you can swallow, especially crackers. To moisten food so you can swallow, especially crackers. The mucus in the saliva is what moistens the food.The mucus in the saliva is what moistens the food.

To inhibit growth of bacteria (which like dark, warm, moist To inhibit growth of bacteria (which like dark, warm, moist areas). What does this are the antibodies, enzymes, and areas). What does this are the antibodies, enzymes, and

macrophages in the saliva.macrophages in the saliva.

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SalivaSaliva

Saliva is not used for digestion of food. There is Saliva is not used for digestion of food. There is an enzyme in saliva that breaks down starch, an enzyme in saliva that breaks down starch, but it takes hours. It is used to break down food but it takes hours. It is used to break down food stuck between the teeth so the bacteria can’t eat stuck between the teeth so the bacteria can’t eat it and cause cavities.it and cause cavities.

Saliva contains bactericidal enzymes that initiate Saliva contains bactericidal enzymes that initiate the digestion of carbohydrates, and bicarbonate the digestion of carbohydrates, and bicarbonate buffer. However, it does not contain enzymes buffer. However, it does not contain enzymes that begin the digestion of proteins; chemical that begin the digestion of proteins; chemical digestion begins in the stomach.digestion begins in the stomach.

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TEETHTEETHHow many teeth does the average adult have? 32 How many teeth does the average adult have? 32 How manyHow many DECIDUOUS TEETH DECIDUOUS TEETH (baby teeth that (baby teeth that fall out)? fall out)? 2020How many How many INCISORSINCISORS (most anterior)? 8: for (most anterior)? 8: for cutting like scissorscutting like scissorsHow many How many CANINESCANINES? 4: for tearing? 4: for tearingHow many How many PRE-MOLARSPRE-MOLARS((BICUSPIDSBICUSPIDS = 2 roots)? = 2 roots)? 8:For chewing, some tearing8:For chewing, some tearingHow many How many MOLARS (TRICUSPIDS = 3 roots)MOLARS (TRICUSPIDS = 3 roots)? ? They are the most posterior; 12: For chewing, They are the most posterior; 12: For chewing, some tearing. The 4 most posterior ones are called some tearing. The 4 most posterior ones are called WISDOM TEETH, which sometimes grow crooked, WISDOM TEETH, which sometimes grow crooked, called “impacted”called “impacted”

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STRUCTURE OF TOOTHSTRUCTURE OF TOOTHGINGIVAGINGIVA are the gums are the gumsCROWNCROWN is the area above the gingiva is the area above the gingivaROOTROOT is embedded in a socket in the bone. In the is embedded in a socket in the bone. In the maxilla, the root can extend into the maxillary sinus. maxilla, the root can extend into the maxillary sinus. Damage to the sinus can be a lot of problems.Damage to the sinus can be a lot of problems.ENAMELENAMEL is the external layer of the tooth. It is stronger is the external layer of the tooth. It is stronger than bone, but does wear out. It is suppose to be ivory than bone, but does wear out. It is suppose to be ivory color, not white. Whitening procedures scrape away color, not white. Whitening procedures scrape away outer oxidized layer, to expose the layer underneath, outer oxidized layer, to expose the layer underneath, which is white, but it will oxidize, too.which is white, but it will oxidize, too.DENTINDENTIN is deep to the enamel. It is like bone, with living is deep to the enamel. It is like bone, with living tissues and cells.tissues and cells.PULP CAVITYPULP CAVITY with with PULPPULP is deep to the dentin. It has is deep to the dentin. It has blood vessels and nerves. blood vessels and nerves. PERIODONTAL LIGAMENTPERIODONTAL LIGAMENT attaches the tooth to the attaches the tooth to the bone. It’s like periosteum. Disease of this structure is bone. It’s like periosteum. Disease of this structure is the most common cause of tooth loss in adults.the most common cause of tooth loss in adults. 2121

Tooth Tooth StructureStructure

Figure 22.112222

Tooth ProblemsTooth Problems

When bacteria eat away at the enamel, what’s it called? When bacteria eat away at the enamel, what’s it called? CARY (CARY (CAVITY)CAVITY)The dentist removes a larger area than where the The dentist removes a larger area than where the bacteria destroyed, and fills it in.bacteria destroyed, and fills it in.If the cavity extends into the pulp cavity, there is no way If the cavity extends into the pulp cavity, there is no way to clean it up. The treatment is to make a bigto clean it up. The treatment is to make a big hole, hole, scrape out the pulp, and fill up the whole thing = scrape out the pulp, and fill up the whole thing = ROOT ROOT CANAL.CANAL. This is a dead tooth, but still there. This is a dead tooth, but still there.Bacteria between the gingiva and tooth causes Bacteria between the gingiva and tooth causes inflammation of the gingiva = inflammation of the gingiva = GINGIVITISGINGIVITIS..When it gets worse, the gingiva pulls away from the When it gets worse, the gingiva pulls away from the tooth and the bacteria extends down to the periodontal tooth and the bacteria extends down to the periodontal ligament =ligament = PERIODONTITIS PERIODONTITIS. This is the major cause of . This is the major cause of tooth loss. The tooth loosens and falls out. That’s why tooth loss. The tooth loosens and falls out. That’s why you need to floss.you need to floss.

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Cavity (called a “cary”)Cavity (called a “cary”)

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Plaque on ToothPlaque on Tooth

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X-ray of Teeth

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X-ray of Teeth

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Fun FactsFun Facts

--Your teeth start growing 6 months --Your teeth start growing 6 months before you are born.before you are born.

If you are right handed, you will tend to chew your food on the right side of your mouth. If you are left handed, you will tend to chew your food on the left side of your mouth.

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GI TractGI Tract

This is a tube through the body, forming This is a tube through the body, forming the esophagus, stomach, small and large the esophagus, stomach, small and large intestine. The GI tract functions to digest intestine. The GI tract functions to digest and absorb.and absorb.– EsophagusEsophagus– StomachStomach– Small IntestineSmall Intestine– Large IntestineLarge Intestine

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NOTENOTE

When you are referring to a structure that has a cavity (stomach, esophagus, uterus, eye, etc), the layer that touches the lumen is considered the superficial layer, even though from the outside of the body it would be considered deeper.

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Layers of GI TubeLayers of GI Tube

There are four layers:There are four layers:1. MUCOSA1. MUCOSA (inner layer). The lining varies from region to (inner layer). The lining varies from region to region.region.– EpitheliumEpithelium– Lamina Propria: Loose connective tissueLamina Propria: Loose connective tissue– Muscularis mucosae: very thin smooth muscle, causes little Muscularis mucosae: very thin smooth muscle, causes little

twitches within the mucosa.twitches within the mucosa.

2. SUBMUCOSA2. SUBMUCOSA (moderate dense connective tissue). (moderate dense connective tissue). Lots of elastic fibers, blood vessels, and lymphatic vessels.Lots of elastic fibers, blood vessels, and lymphatic vessels.3. MUSCULARIS EXTERNA 3. MUSCULARIS EXTERNA (smooth muscle layer with (smooth muscle layer with two parts:two parts:– Circular Layer (inner)Circular Layer (inner)– Longitudinal layer (outer)Longitudinal layer (outer)

4. Serosa4. Serosa

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Mucosa

Submucosa

Muscularis Externa

Serosa

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3. Muscularis Externa3. Muscularis Externa

Muscularis Externa is extremely important for Muscularis Externa is extremely important for digestion. digestion. It allows for 2 types of actions:It allows for 2 types of actions:

a. a. PERISTALSIS PERISTALSIS: a rhythmic contraction to push : a rhythmic contraction to push something along. This pushes food down by smooth something along. This pushes food down by smooth muscle contraction. muscle contraction.

b. b. SEGMENTATIONSEGMENTATION: A back-and-forth : A back-and-forth squeezing of the muscle to grind up food. Food moves squeezing of the muscle to grind up food. Food moves forward then backward a little, then forward again. forward then backward a little, then forward again. Function is to churn up the food inside. Function is to churn up the food inside. Some areas have thicker smooth muscle = Some areas have thicker smooth muscle = SPHINCTERSPHINCTER. . Circular muscles open and closes an opening. Circular muscles open and closes an opening. – Controls the flow of food from one region to another.Controls the flow of food from one region to another.

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Layers of GI TubeLayers of GI Tube

4. SEROSA4. SEROSA is not in all regions (none in is not in all regions (none in esophagus).esophagus).

– Simple squamous epithelium Simple squamous epithelium – Loose connective tissueLoose connective tissue

– From internal to external, the layers of From internal to external, the layers of this tube are the mucosa, submucosa, this tube are the mucosa, submucosa, muscularis, serosa.muscularis, serosa.

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EsophagusEsophagus

Extends from the oropharynx to the stomach, Extends from the oropharynx to the stomach, about 25 cm long. The things that are about 25 cm long. The things that are specialized in the esophagus are:specialized in the esophagus are:1. 1. MUCOSAL EPITHELIUMMUCOSAL EPITHELIUM (non-keratinized (non-keratinized stratified squamous epithelium). stratified squamous epithelium).

Why? It protects against things you swallow; Why? It protects against things you swallow; pointy potato chips, etc. Cuboidal would slough.pointy potato chips, etc. Cuboidal would slough.2. 2. MUSCULARIS EXTERNUMMUSCULARIS EXTERNUM in upper half = in upper half = skeletal muscle, is under voluntary control. skeletal muscle, is under voluntary control. Lower half = smooth muscle, not voluntary. Lower half = smooth muscle, not voluntary. Food gets caught in the lower half because it Food gets caught in the lower half because it hasn’t started peristalsis.hasn’t started peristalsis.

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Cardiac SphincterCardiac Sphincter

The esophagus goes through the thoracic The esophagus goes through the thoracic cavity.cavity.

It needs to go through the diaphragm’s It needs to go through the diaphragm’s opening (esophageal hiatus).opening (esophageal hiatus).

It empties to the stomach through a It empties to the stomach through a CARDIAC SPHINCTERCARDIAC SPHINCTER = a thickening of = a thickening of the muscularis externa. This is NOT A the muscularis externa. This is NOT A TRUE SPHINCTER.TRUE SPHINCTER.

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Stomach AnatomyStomach Anatomy

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Stomach: FunctionsStomach: FunctionsStore FoodStore Food

Mechanically churns food into a paste called Mechanically churns food into a paste called CHYMECHYME

Kill bacteriaKill bacteria

Some digestion: of proteinsSome digestion: of proteins

Some absorption: of water, alcoholSome absorption: of water, alcohol

Gastric emptying is the release of food from the stomach into the duodenum; the process is tightly controlled with liquids being emptied much more quickly than solids..

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STOMACH FUNCTIONSSTOMACH FUNCTIONS

1. 1. Store Food,Store Food, so it can be slowly released into a small so it can be slowly released into a small intestine. Your whole Thanksgiving dinner can take your intestine. Your whole Thanksgiving dinner can take your stomach diameter from 2” to 8” diameter.stomach diameter from 2” to 8” diameter.22. Mechanically Churns food.. Mechanically Churns food. Secretions from the Secretions from the stomach is added, turns everything into a gooey paste. stomach is added, turns everything into a gooey paste. When you throw up, you can see the enzyme secretions When you throw up, you can see the enzyme secretions = = CHYMECHYME..3. 3. Kill bacteria.Kill bacteria. The stomach is very acidic (pH 1) like The stomach is very acidic (pH 1) like battery acid. Chyme will even eat through clothing.battery acid. Chyme will even eat through clothing.4. 4. Some digestion: of proteins.Some digestion: of proteins.5. 5. Some absorptionSome absorption: of water, alcohol (alcohol is : of water, alcohol (alcohol is absorbed in the mouth, too!)absorbed in the mouth, too!)Food takes four hours to completely leave the stomach.Food takes four hours to completely leave the stomach.

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FUN FACTSFUN FACTSBody measurements Body measurements

for food portionsfor food portions

1 oz = a handful1 oz = a handful

3 oz = palm size (meat)3 oz = palm size (meat)

cup = fistcup = fist

teaspoon = tip of thumbteaspoon = tip of thumb

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REGIONS OF THE STOMACHREGIONS OF THE STOMACH

1. Cardiac region (near heart)1. Cardiac region (near heart)2. Fundus (above the cardiac sphincter)2. Fundus (above the cardiac sphincter)3. Body3. Body4. Pyloric region4. Pyloric region5. 5. PYLORIC SPHINCTER PYLORIC SPHINCTER (a true sphincter)(a true sphincter)

The lining of the stomach is folded over into The lining of the stomach is folded over into RUGAERUGAE, to allow for expansion of the stomach., to allow for expansion of the stomach.

When the stomach is full, the rugae flatten out.When the stomach is full, the rugae flatten out.

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The StomachThe Stomach

Figure 22.14a4242


Figure 22.14b4343

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HISTOLOGY OF THE STOMACHHISTOLOGY OF THE STOMACH

Epithelium: simple columnar epithelium.Epithelium: simple columnar epithelium.– Its function is for secretion and absorption.Its function is for secretion and absorption.

Lamina Propria: contains gastric pits. Lamina Propria: contains gastric pits.

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Figure 22.15a-c4646

Stomach CellsStomach Cells

CHIEF CELLSCHIEF CELLS secrete an enzyme called secrete an enzyme called pepsinogen. When pepsinogen is exposed to pepsinogen. When pepsinogen is exposed to hydrochloric acid (HCl), it is cleaved into pepsin, hydrochloric acid (HCl), it is cleaved into pepsin, its active form. Pepsin digests proteins.its active form. Pepsin digests proteins.

PARIETAL CELLSPARIETAL CELLS in the stomach secrete in the stomach secrete hydrochloric acid. hydrochloric acid.

They also secrete intrinsic factor, which is They also secrete intrinsic factor, which is needed to absorb vitamin B12, which is needed to absorb vitamin B12, which is needed to make red blood cells.needed to make red blood cells.

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Intrinsic FactorIntrinsic Factor

A person who lacks intrinsic factor (such A person who lacks intrinsic factor (such as those who have a stomach stapling as those who have a stomach stapling procedure or gastric bypass) will not be procedure or gastric bypass) will not be able to absorb vitamin B12 and they will able to absorb vitamin B12 and they will get a type of anemia called pernicious get a type of anemia called pernicious anemia. anemia. Treatment is injectable B12 shots monthly Treatment is injectable B12 shots monthly for the rest of their lives. They also have a for the rest of their lives. They also have a new dissolvable oral form of vitamin B12 new dissolvable oral form of vitamin B12

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Gastric Gastric glandgland

Figure 22.15a-c4949

PARTICULARS OF STOMACHPARTICULARS OF STOMACH

Has a third layer of the muscularis Has a third layer of the muscularis externum: an externum: an OBLIQUE LAYEROBLIQUE LAYER to churn to churn food.food.

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Figure 22.14b5151

Problems with the stomachProblems with the stomach

There are lots of goblet cells in the stomach which make mucus to There are lots of goblet cells in the stomach which make mucus to prevent the stomach from digesting itself. Bacterial infection can prevent the stomach from digesting itself. Bacterial infection can erode this area = erode this area = GASTRIC (or Peptic) ULCERGASTRIC (or Peptic) ULCER..

Acid RefluxAcid Reflux– The acid in your stomach is strong enough to dissolve razor The acid in your stomach is strong enough to dissolve razor

blades.blades. The acid can creep up the esophagus and erode the The acid can creep up the esophagus and erode the lining there, causing heartburn.lining there, causing heartburn.

– The acid can stay in the stomach and cause an ulcer. In severe The acid can stay in the stomach and cause an ulcer. In severe cases, the ulcers are so deep, they bleed, and the person might cases, the ulcers are so deep, they bleed, and the person might even vomit blood.even vomit blood.

– Tends to occur more when a person is under a lot of stress Tends to occur more when a person is under a lot of stress because more acid is produced.because more acid is produced.

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Two major causes Two major causes of Peptic (stomach and of Peptic (stomach and

duodenum) Ulcers:duodenum) Ulcers:1) 60% of gastric and up to 90% of duodenal ulcers are 1) 60% of gastric and up to 90% of duodenal ulcers are due to a bacterium called due to a bacterium called Helicobacter pyloriHelicobacter pylori..– The body responds by increasing gastrin secretion, The body responds by increasing gastrin secretion,

and enzyme which causes HCl to be secreted, which and enzyme which causes HCl to be secreted, which erodes the stomach lining.erodes the stomach lining.

2) NSAIDs (non-steroidal anti-inflammatory drugs, such 2) NSAIDs (non-steroidal anti-inflammatory drugs, such as aspirin) block prostaglandin synthesis. as aspirin) block prostaglandin synthesis. – Prostaglandins promote the inflammatory reaction. Prostaglandins promote the inflammatory reaction.

They also are found in the stomach, protecting it from They also are found in the stomach, protecting it from erosion.erosion.

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Stomach (gastric) ulcerStomach (gastric) ulcer

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Risk and TransmissionRisk and Transmission

The lifetime risk for developing a peptic ulcer is The lifetime risk for developing a peptic ulcer is approximately 10%.approximately 10%.

In Western countries the prevalence of Helicobacter In Western countries the prevalence of Helicobacter pylori infections roughly matches age (i.e., 20% at age pylori infections roughly matches age (i.e., 20% at age 20, 30% at age 30, 80% at age 80 etc.). 20, 30% at age 30, 80% at age 80 etc.).

Prevalence is higher in third world countries. Prevalence is higher in third world countries.

Transmission is by food, contaminated groundwater, and Transmission is by food, contaminated groundwater, and through human saliva (such as from kissing or sharing through human saliva (such as from kissing or sharing toothbrushes or food utensils)toothbrushes or food utensils)

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Problems With the StomachProblems With the Stomach

The cardiac sphincter doesn’t close well, since it The cardiac sphincter doesn’t close well, since it is not a true sphincter; consequences:is not a true sphincter; consequences:– You can throw up (reverse peristalsis). Rats do have You can throw up (reverse peristalsis). Rats do have

a true cardiac sphincter, and can’t vomit! a true cardiac sphincter, and can’t vomit! – That’s why rat poison won’t kill people or dogs; they That’s why rat poison won’t kill people or dogs; they

can throw it up.can throw it up.

Another consequence: hiatal hernia.Another consequence: hiatal hernia.

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HIATAL HERNIAHIATAL HERNIA

Part of the stomach, protrudes through Part of the stomach, protrudes through esophageal hiatus, causing pain and esophageal hiatus, causing pain and difficulty swallowing.difficulty swallowing.It is the most common of all hernias.It is the most common of all hernias. There is a great amount of acid reflux; There is a great amount of acid reflux; erodes walls of esophagus, causing erodes walls of esophagus, causing ulcerations of esophagus. ulcerations of esophagus. Treatment is surgical; pull down the Treatment is surgical; pull down the stomach, and tighten the hernia in a stomach, and tighten the hernia in a laparoscopic procedure.laparoscopic procedure.

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Fun FactFun Fact

Astronauts can't belch - there is no gravity to separate liquid from gas in their stomachs.

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SMALL INTESTINESMALL INTESTINE (Small bowels) (Small bowels)

These are the longest part of the GI tract These are the longest part of the GI tract (9-15 feet long, 1” diameter)(9-15 feet long, 1” diameter)

In a cadaver, they are even longer, In a cadaver, they are even longer, because the muscles relax.because the muscles relax.

The small intestine is the most important The small intestine is the most important region of the GI tract because almost all of region of the GI tract because almost all of the digestion and absorption takes place the digestion and absorption takes place here.here.

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Small Intestine StructureSmall Intestine Structure

The small intestine needs a lot of surface area: The small intestine needs a lot of surface area: 200 square meters, which is the floor space of a 200 square meters, which is the floor space of a typical house. typical house. How do you get such a lot of surface area? How do you get such a lot of surface area? There are lots of folds called There are lots of folds called PLICAE PLICAE CIRCULARISCIRCULARIS. . Each of these folds also has folds, called Each of these folds also has folds, called VILLI. VILLI. If you take velvet and fold it, the fold is theIf you take velvet and fold it, the fold is the plicae, plicae, and the velvet hairs areand the velvet hairs are villi. villi.Each of the villi has epithelial cells calledEach of the villi has epithelial cells called MICROVILLI, MICROVILLI, which make awhich make a BRUSH BORDER. BRUSH BORDER.

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The Small IntestineThe Small Intestine

Figure 22.17a-c

Crypt of Lieberkuhn

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Small Intestine RegionsSmall Intestine Regions

Duodenum “12 finger widths long”Duodenum “12 finger widths long”

Jejunum “hungry when empty”Jejunum “hungry when empty”

Ileum “twisted”Ileum “twisted”

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DUODENUMDUODENUM

This is the shortest region, only one foot This is the shortest region, only one foot long. long. It receives chyme from the stomach. This It receives chyme from the stomach. This is where digestion begins. There are two is where digestion begins. There are two ducts at the beginning of the duodenum ducts at the beginning of the duodenum from the pancreas and gallbladder. It is from the pancreas and gallbladder. It is the site of action of liver and pancreas the site of action of liver and pancreas secretions.secretions.

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The DuodenumThe Duodenum

Figure 22.166767

PancreasPancreas

PANCREASPANCREAS is an endocrine gland, and also is an endocrine gland, and also participates in digestion. Most of the digestive participates in digestion. Most of the digestive enzymes are made here. They go out the enzymes are made here. They go out the PANCREATIC DUCTPANCREATIC DUCT to enter the small to enter the small intestine. intestine.

It also produces It also produces BICARBONATEBICARBONATE (from a (from a hormone called hormone called SECRETINSECRETIN) to increase the pH ) to increase the pH (decrease the acidity) of the chyme coming from (decrease the acidity) of the chyme coming from the stomach. If there is too much acid there, get the stomach. If there is too much acid there, get a a DUODENAL ULCERDUODENAL ULCER..

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PANCREASPANCREAS

ACINAR CELLS: ACINAR CELLS: secretes digestive secretes digestive enzymesenzymes

ISLETS OF LANGERHANS: ISLETS OF LANGERHANS: secretes secretes insulin insulin

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Pancreas HistologyPancreas Histology

Figure 22.25a7070

PancreasPancreas

Acinar cells (secrete enzymes)

Islet of Langerhans (secretes insulin)

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Gall BladderGall Bladder

GALL BLADDERGALL BLADDER stores and concentrates bile, stores and concentrates bile, which emulsifies fat: It breaks down the fat into which emulsifies fat: It breaks down the fat into microscopic droplets which can be broken down microscopic droplets which can be broken down by pancreatic enzymes. by pancreatic enzymes.

Fat doesn’t dissolve in water, so when you go to Fat doesn’t dissolve in water, so when you go to McDonalds and order the Big Mac, fries, and McDonalds and order the Big Mac, fries, and shake, you get 200 grams of fat (one week shake, you get 200 grams of fat (one week supply), which globs together in the intestine, supply), which globs together in the intestine, and that much more bile is needed to break it and that much more bile is needed to break it down.down.

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What Ronald McDonald is doing What Ronald McDonald is doing to your arteriesto your arteries

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GALL BLADDERGALL BLADDERThis is located inferior to the liver, and its function This is located inferior to the liver, and its function is to store and concentrate bile.is to store and concentrate bile.Bile is a detergent/soap (not an enzyme) which Bile is a detergent/soap (not an enzyme) which emulsifies fat: It breaks down the fat into emulsifies fat: It breaks down the fat into microscopic droplets which can be broken down microscopic droplets which can be broken down by pancreatic enzymes. by pancreatic enzymes. It does NOT make or secrete bile; that is done by It does NOT make or secrete bile; that is done by the liver.the liver.Bile is made in the liver from Hemoglobin (Hgb), Bile is made in the liver from Hemoglobin (Hgb), and also contains cholesterol and other things.and also contains cholesterol and other things.The function of bile is to break down lipids (fats) so The function of bile is to break down lipids (fats) so they can be digested.they can be digested.

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Gallbladder and PancreasGallbladder and Pancreas

Figure 22.167575

Gall BladderGall Bladder

As the liver produces bile, if there is no As the liver produces bile, if there is no food in the duodenum, the sphincter food in the duodenum, the sphincter closes and bile backs up into the gall closes and bile backs up into the gall bladder. When there is food, the sphincter bladder. When there is food, the sphincter releases the bile.releases the bile.The gall bladder is similar to the stomach. The gall bladder is similar to the stomach. It is lined with It is lined with RUGAERUGAE (allows organ (allows organ expansion). Has muscles around it to expansion). Has muscles around it to push bile out.push bile out.

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Gall StonesGall Stones

One function of the gall bladder is to One function of the gall bladder is to concentrate the concentrate the BILEBILE, but if the bile salts , but if the bile salts crystallize, crystallize, GALL STONESGALL STONES can form. can form. The stones block the cystic duct, and The stones block the cystic duct, and causes a lot of pain as the bile backs up.causes a lot of pain as the bile backs up.Treatment is to cut the cystic duct and Treatment is to cut the cystic duct and remove the gall bladder. remove the gall bladder. Now that person can only eat small Now that person can only eat small amounts of fats at a time.amounts of fats at a time.

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Types of Gall StonesTypes of Gall Stones

Stones made out of cholesterol (most Stones made out of cholesterol (most common type). It has nothing to do with common type). It has nothing to do with the cholesterol levels in the blood.the cholesterol levels in the blood.

Stones made from too much bilirubin in Stones made from too much bilirubin in the bile. the bile.

Gallstones are more common in women, Gallstones are more common in women, Native Americans and other ethnic groups, Native Americans and other ethnic groups, and people over age 40. Gallstones may and people over age 40. Gallstones may also run in families.also run in families.

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JejunumJejunum

JEJUNUMJEJUNUM (“empty”) (“empty”)

This is the part of the small intestine where This is the part of the small intestine where most digestion and absorption occurs. most digestion and absorption occurs.

It is 3 feet long. It is 3 feet long.

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IleumIleum

ILEUMILEUM (“twisted”) is 5-10 feet long. It is (“twisted”) is 5-10 feet long. It is the terminal portion of the small intestine.the terminal portion of the small intestine.

Much of the absorption takes place here. Much of the absorption takes place here.

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Histology of Small IntestineHistology of Small Intestine

The intestines are lined with simple columnar The intestines are lined with simple columnar epithelium with lots of goblet cells that make epithelium with lots of goblet cells that make mucus for protection. mucus for protection. However, the pancreatic enzymes can digest the However, the pancreatic enzymes can digest the mucus and the epithelial cells, so the lining of mucus and the epithelial cells, so the lining of the small intestine is replaced every day. the small intestine is replaced every day. The basic functions of this epithelium are The basic functions of this epithelium are secretion and absorption.secretion and absorption.Absorption is a digestive process in which Absorption is a digestive process in which nutrients enter the capillaries.nutrients enter the capillaries.

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Crypt of LieberkuhnCrypt of Lieberkuhn

The The INTESTINAL CRYPT (CRYPT OF INTESTINAL CRYPT (CRYPT OF LIEBERKUHN)LIEBERKUHN) is where the new epithelial is where the new epithelial cells come from, and they are pushed cells come from, and they are pushed upwards into the villi to replace the upwards into the villi to replace the digested cells. digested cells.

Also in this crypt are cells that produce Also in this crypt are cells that produce enzymes and hormones.enzymes and hormones.

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Lacteal

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Figure 22.17a-c8585

Absorption in Small IntestineAbsorption in Small Intestine

In the villis is a fenestrated capillary bed, which In the villis is a fenestrated capillary bed, which needs to absorb a lot of material.needs to absorb a lot of material.

The small intestine absorbs carbohydrates, fats, The small intestine absorbs carbohydrates, fats, and proteins (although protein enzymes have and proteins (although protein enzymes have already begun working earlier in the digestive already begun working earlier in the digestive tract in the stomach). tract in the stomach).

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Intestinal VilliIntestinal Villi

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Lymphatics of Small IntestineLymphatics of Small Intestine

There are also large lymphatic capillaries There are also large lymphatic capillaries in each villis called in each villis called LACTEALSLACTEALS, whose , whose function is to absorb breakdown products function is to absorb breakdown products of fat.of fat. The vessel is large so it won’t get The vessel is large so it won’t get clogged up. clogged up.

Under all this are the Under all this are the MUSCULARIS MUSCULARIS MUCOSAMUCOSA muscles which can twitch to muscles which can twitch to move the villa so food does not get stuck. move the villa so food does not get stuck.

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Inguinal HerniaInguinal HerniaThe inguinal canal is open in the male to allow for passage of the The inguinal canal is open in the male to allow for passage of the spermatic cord. In the female, the area is closed, but weak.spermatic cord. In the female, the area is closed, but weak.

When there is abdominal pressure (lifting a weight), a piece of small When there is abdominal pressure (lifting a weight), a piece of small intestine can push out of this canal, causing pain.intestine can push out of this canal, causing pain.

Symptoms and warning signs:Symptoms and warning signs:http://www.symptomfind.com/diseases-conditions/hernia-symptoms-warning-signs/

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http://www.symptomfind.com/diseases-conditions/hernia-symptoms-warning-signs/

Problem with Small IntestineProblem with Small Intestine

Crohn’s DiseaseCrohn’s Disease– Autoimmune disease of the GI tractAutoimmune disease of the GI tract– Most common area affected is small intestineMost common area affected is small intestine– Inflammation causes pain and diarrhea (may Inflammation causes pain and diarrhea (may

be bloody)be bloody)– Genetic cause (high risk if siblings have it)Genetic cause (high risk if siblings have it)– Usually occurs in males in their 20’sUsually occurs in males in their 20’s– No cure; just treatment of symptomsNo cure; just treatment of symptoms

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Celiac disease Celiac disease (Sprue; gluten intolerance)(Sprue; gluten intolerance)

Genetic autoimmune disorder of the small intestine, Genetic autoimmune disorder of the small intestine, causing chronic diarrhea. The person is allergic to causing chronic diarrhea. The person is allergic to gluten. Causes destruction of microvilli and villi.gluten. Causes destruction of microvilli and villi.

It is characterized by having pale, loose and greasy It is characterized by having pale, loose and greasy stools (steatorrhoea) which are voluminous and stools (steatorrhoea) which are voluminous and malodorous. malodorous.

It often presents with abdominal pain and cramping, It often presents with abdominal pain and cramping, abdominal distension, and sometimes mouth ulcers.abdominal distension, and sometimes mouth ulcers.

Without adjusting the diet, coeliac disease leads to an Without adjusting the diet, coeliac disease leads to an increased risk of adenocarcinoma (small intestine increased risk of adenocarcinoma (small intestine cancer). cancer).

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They may develop ulcerative jejunitis and stricturing (narrowing as a result They may develop ulcerative jejunitis and stricturing (narrowing as a result of scarring with obstruction of the bowel).of scarring with obstruction of the bowel).

The changes in the bowel make it less able to absorb carbohydrates, fats, The changes in the bowel make it less able to absorb carbohydrates, fats, minerals (calcium and iron), and the fat-soluble vitamins A, D, E, and K.minerals (calcium and iron), and the fat-soluble vitamins A, D, E, and K.

Anemia may develop in several ways: iron malabsorption may cause iron Anemia may develop in several ways: iron malabsorption may cause iron deficiency anemia, and folic acid and vitamin B12 malabsorption may give deficiency anemia, and folic acid and vitamin B12 malabsorption may give rise to megaloblastic anemia.rise to megaloblastic anemia.

Calcium and vitamin D malabsorption may cause osteopenia (decreased Calcium and vitamin D malabsorption may cause osteopenia (decreased mineral content of the bone) or osteoporosis (bone weakening and risk of mineral content of the bone) or osteoporosis (bone weakening and risk of fragility fractures).fragility fractures).

A small proportion have abnormal coagulation due to vitamin K deficiency A small proportion have abnormal coagulation due to vitamin K deficiency and are slightly at risk for abnormal bleeding.and are slightly at risk for abnormal bleeding.

Coeliac disease is also associated with bacterial overgrowth of the small Coeliac disease is also associated with bacterial overgrowth of the small intestine, which can worsen malabsorption or cause malabsorption despite intestine, which can worsen malabsorption or cause malabsorption despite adherence to treatment.adherence to treatment.

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Celiac disease is caused by an allergy to gluten.Celiac disease is caused by an allergy to gluten.

Gluten is present in Wheat subspecies (such as spelt, semolina and Gluten is present in Wheat subspecies (such as spelt, semolina and durum) and related species such as barley, rye, triticale and Kamut. durum) and related species such as barley, rye, triticale and Kamut. A small minority of coeliac patients also react to oats. It is most A small minority of coeliac patients also react to oats. It is most probable that oats produce symptoms due to cross contamination probable that oats produce symptoms due to cross contamination with other grains in the fields or in the distribution channels. with other grains in the fields or in the distribution channels. Generally, oats are therefore not recommended.Generally, oats are therefore not recommended.

Other cereals such as maize (corn), millet, sorghum, teff, rice, and Other cereals such as maize (corn), millet, sorghum, teff, rice, and wild rice are safe for patients to consume, as well as non cereals wild rice are safe for patients to consume, as well as non cereals such as amaranth, quinoa or buckwheat. Non-cereal carbohydrate-such as amaranth, quinoa or buckwheat. Non-cereal carbohydrate-rich foods such as potatoes and bananas do not contain gluten and rich foods such as potatoes and bananas do not contain gluten and do not trigger symptoms.do not trigger symptoms.

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Gluten-free dietGluten-free diet

Gluten is used in foods in some unexpected ways, for example as a Gluten is used in foods in some unexpected ways, for example as a stabilizing agent or thickener in products like ice-cream and stabilizing agent or thickener in products like ice-cream and ketchup.ketchup.

People wishing to follow a completely gluten free diet must also take People wishing to follow a completely gluten free diet must also take into consideration the ingredients of any over-the-counter or into consideration the ingredients of any over-the-counter or prescription medications and vitamins. Also, cosmetics such as prescription medications and vitamins. Also, cosmetics such as lipstick, lip balms, and lip gloss may contain gluten and need to be lipstick, lip balms, and lip gloss may contain gluten and need to be investigated before use. Glues used on envelopes may also contain investigated before use. Glues used on envelopes may also contain gluten.gluten.

Most products manufactured for Passover are gluten free. Most products manufactured for Passover are gluten free. Exceptions are foods that list matzah as an ingredient, usually in the Exceptions are foods that list matzah as an ingredient, usually in the form of cake meal.form of cake meal.

A blood test for IgA antiendomysial antibodies can detect coeliac A blood test for IgA antiendomysial antibodies can detect coeliac disease.disease.

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Large Intestine Large Intestine (Colon, or large bowel) (Colon, or large bowel)

This is about 5 feet long, diameter of 4”.This is about 5 feet long, diameter of 4”.Absorbs a LOT of water and saltsAbsorbs a LOT of water and salts

Absorbs electrolytes (Na, K, etc)Absorbs electrolytes (Na, K, etc)

Stores feces for defecation (terminal portion)Stores feces for defecation (terminal portion)

Contains abundant bacteria (E. coli):Contains abundant bacteria (E. coli):– Make vitamins (B5, K, biotin)Make vitamins (B5, K, biotin)– Allow material to move through large intestine easierAllow material to move through large intestine easier– Keep out harmful bacteriaKeep out harmful bacteria– They eat things you can’t digestThey eat things you can’t digest

FiberFiber

Some sugars that we don’t have enzymes forSome sugars that we don’t have enzymes for 9595

Intestinal GasIntestinal Gas

When these bacteria are happy and dividing, they When these bacteria are happy and dividing, they produce gas. If you are lactose intolerant, your are produce gas. If you are lactose intolerant, your are missing the enzyme for lactose so the bacteria gets missing the enzyme for lactose so the bacteria gets more sugar and you get more gas! Beans also have more sugar and you get more gas! Beans also have these sugars, so they give you gas. these sugars, so they give you gas. Mexico has different strains of E. coli in their water; the Mexico has different strains of E. coli in their water; the two strains battle it out and you get diarrhea. two strains battle it out and you get diarrhea. Diarrhea is when the large intestine does not absorb Diarrhea is when the large intestine does not absorb water water dehydration and electrolyte imbalance. dehydration and electrolyte imbalance. Cholera is a disease which attacks the large intestine, Cholera is a disease which attacks the large intestine, preventing water absorption, and can be fatal in 24-48 preventing water absorption, and can be fatal in 24-48 hours. hours. The difference between diarrhea and constipation is the The difference between diarrhea and constipation is the amount of water absorbed from the large intestine.amount of water absorbed from the large intestine.

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Regions of the Large IntestineRegions of the Large Intestine

CecumCecum

Ascending colonAscending colon

Transverse colonTransverse colon

Descending colonDescending colon

Sigmoid colonSigmoid colon

RectumRectum

AnusAnus

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Figure 22.18a

Large IntestineLarge Intestine

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Gross Anatomy of the Large Gross Anatomy of the Large IntestineIntestine

The large intestine is divided into regions, but The large intestine is divided into regions, but they function the same. they function the same.

The ileum enters into the first region of the large The ileum enters into the first region of the large intestine called the intestine called the CECUM.CECUM.

The ileo-cecal valve separates these and The ileo-cecal valve separates these and controls the amount of chyme that enters into controls the amount of chyme that enters into the large intestine. the large intestine.

It also prevents the E. coli from leaving the large It also prevents the E. coli from leaving the large intestine and getting into the small intestine, intestine and getting into the small intestine, where they would cause disease.where they would cause disease.

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AppendixAppendix

Below the cecum is the Below the cecum is the APPENDIX, which is a APPENDIX, which is a lymph node, but ilymph node, but it contains E coli as well. t contains E coli as well. It might become inflamed, which closes off the It might become inflamed, which closes off the opening: opening: APPENDICITISAPPENDICITISThis is dangerous because It can rupture. Need This is dangerous because It can rupture. Need antibiotics and surgery or can be fatal.antibiotics and surgery or can be fatal.Most common age for this is late teens to early Most common age for this is late teens to early 20’s because a child has a larger opening which 20’s because a child has a larger opening which shrinks with age. When you’re done growing, shrinks with age. When you’re done growing, it’s done shrinking, so if you haven’t had a it’s done shrinking, so if you haven’t had a problem by then, you might be ok.problem by then, you might be ok.

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Large IntestineLarge Intestine

Up from the cecum is the Up from the cecum is the ASCENDING ASCENDING COLON, TRANSVERSE COLON,COLON, TRANSVERSE COLON, and and DESCENDING COLONDESCENDING COLON. .

Then there is an “S” shaped section called Then there is an “S” shaped section called the the SIGMOID COLON,SIGMOID COLON, which leads to the which leads to the RECTUMRECTUM, and out the, and out the ANUS ANUS. .

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SIGMOID COLONSIGMOID COLON

This area allows for the passage of gas without passage This area allows for the passage of gas without passage of feces. The of feces. The LEVATOR ANI MUSCLELEVATOR ANI MUSCLE, when relaxed, , when relaxed, allows only gas to pas. When contracted, the feces can allows only gas to pas. When contracted, the feces can pass. pass. Therefore, this muscle controls defecation by lifting Therefore, this muscle controls defecation by lifting the anal canal superiorly around the feces.the anal canal superiorly around the feces. Another thing that controls defecation is the Another thing that controls defecation is the INTERNALINTERNAL and and EXTERNAL ANAL SPHINCTEREXTERNAL ANAL SPHINCTER. The internal one . The internal one is smooth muscle, and the external is skeletal muscle is smooth muscle, and the external is skeletal muscle (voluntary control). (voluntary control). The smooth muscles which line the large intestine work The smooth muscles which line the large intestine work in coordinated fashion to move the feces out.in coordinated fashion to move the feces out.It takes about 24 hours for food to be processed through It takes about 24 hours for food to be processed through the entire digestive tract.the entire digestive tract.

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Sigmoid Colon

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Problems with Large IntestineProblems with Large Intestine

DIVERTICULITITSDIVERTICULITITS

INFLAMMATORY BOWEL DISEASEINFLAMMATORY BOWEL DISEASE– Crohn’s Disease Crohn’s Disease – Ulcerative colitisUlcerative colitis

IRRITABLE BOWEL SYNDROMEIRRITABLE BOWEL SYNDROME

COLON CANCERCOLON CANCER– SIGMOIDOSCOPYSIGMOIDOSCOPY or a or a COLONOSCOPYCOLONOSCOPY

POLYPSPOLYPS

HEMORRHOIDSHEMORRHOIDS 107107

DIVERTICULITITSDIVERTICULITITS

DIVERTICULUM DIVERTICULUM (Diverticula is plural) can (Diverticula is plural) can form, a small pouch in the large intestine.form, a small pouch in the large intestine.

They can become inflamed, usually from a They can become inflamed, usually from a small, hard piece of feces, causes the small, hard piece of feces, causes the condition known as condition known as DIVERTICULITITS.DIVERTICULITITS.

These are painful and often need to be These are painful and often need to be surgically removed. surgically removed.

May be caused by lack of fiber, causing May be caused by lack of fiber, causing increased pressure in the colon.increased pressure in the colon.

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Inflammatory Bowel Disease (IBD)Inflammatory Bowel Disease (IBD)

IBD is a group of inflammatory conditions IBD is a group of inflammatory conditions of the colon and small intestine. of the colon and small intestine.

The major types of IBD are Crohn's The major types of IBD are Crohn's disease and ulcerative colitisdisease and ulcerative colitis

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Ulcerative ColitisUlcerative Colitis

The main symptom is constant diarrhea mixed with blood, of The main symptom is constant diarrhea mixed with blood, of gradual onset. gradual onset.

An intermittent disease, with periods of exacerbated An intermittent disease, with periods of exacerbated symptoms, and periods that are relatively symptom-freesymptoms, and periods that are relatively symptom-free

No known cause, but may be geneticNo known cause, but may be genetic

May be triggered by environmental factorsMay be triggered by environmental factors

Dietary modification may reduce the discomfort Dietary modification may reduce the discomfort

It is treated as though it were an autoimmune disease (anti-It is treated as though it were an autoimmune disease (anti-inflammatory drugs, immunosuppression)inflammatory drugs, immunosuppression)

Colectomy (partial or total removal of the large bowel Colectomy (partial or total removal of the large bowel through surgery) is occasionally necessary, and is through surgery) is occasionally necessary, and is considered to be a cure for the diseaseconsidered to be a cure for the disease ..

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Ulcerative Colitis

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IRRITABLE BOWEL SYNDROME (IBS)IRRITABLE BOWEL SYNDROME (IBS)

IBS is a diagnosis of exclusion.IBS is a diagnosis of exclusion.

Symptoms are chronic abdominal pain, bloating, Symptoms are chronic abdominal pain, bloating, and alteration of bowel habits in the absence of and alteration of bowel habits in the absence of any detectable organic cause.any detectable organic cause.

May manifest as diarrhea or constipation or may May manifest as diarrhea or constipation or may alternate between the two.alternate between the two.

May be caused by infection, stress, or onset of May be caused by infection, stress, or onset of maturitymaturity

No cure; treatments attempt to relieve symptoms, No cure; treatments attempt to relieve symptoms, including dietary adjustments, medication and including dietary adjustments, medication and psychological interventions. psychological interventions.

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COLON CANCERCOLON CANCERThis is the #1 most deadly cancer (kills more This is the #1 most deadly cancer (kills more people) because it metastasizes and there are people) because it metastasizes and there are no symptoms. It can be suspected by seeing no symptoms. It can be suspected by seeing blood in the stool; this is an easy test, but not blood in the stool; this is an easy test, but not very accurate. very accurate. A more accurate test is a A more accurate test is a SIGMOIDOSCOPYSIGMOIDOSCOPY. A . A tube is inserted into the sigmoid colon, done in tube is inserted into the sigmoid colon, done in the doctor’s office. The tube has a light, and the doctor’s office. The tube has a light, and they look for growths on the walls of the intestine they look for growths on the walls of the intestine == POLYPS POLYPS, which are pre-cancerous growths. , which are pre-cancerous growths. A colonoscopy is done under general anesthesia A colonoscopy is done under general anesthesia since the tube has to go through the entire since the tube has to go through the entire colon, but it’s more effective. colon, but it’s more effective.

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Colonoscopy Photos

Ileo-cecal valve

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HEMORRHOIDSHEMORRHOIDS

HEMORRHOIDSHEMORRHOIDS are varicose veins in the are varicose veins in the rectum. rectum.

There are large veins along the rectum, There are large veins along the rectum, with nothing constricting them. with nothing constricting them.

They are common in pregnant women and They are common in pregnant women and in fighter pilots from the g-forces they pull.in fighter pilots from the g-forces they pull.

They can be surgically removed. They can be surgically removed.

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Hepatic Portal SystemHepatic Portal System

Almost all of the blood coming from the digestive Almost all of the blood coming from the digestive system drains into a special venous circulation system drains into a special venous circulation called the portal circulation. called the portal circulation. This is because it contains all the nutrients and This is because it contains all the nutrients and toxins that have been absorbed along the toxins that have been absorbed along the digestive tract from ingested food. digestive tract from ingested food. Before these absorbed substances can go into Before these absorbed substances can go into the systemic circulation (the main blood the systemic circulation (the main blood circulation in the body), it must be filtered first to circulation in the body), it must be filtered first to remove or detoxify toxic substances first. remove or detoxify toxic substances first. This filtering and detoxification is one of the 500+ This filtering and detoxification is one of the 500+ functions of the liver.functions of the liver.

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Hepatic Portal SystemHepatic Portal System

Many drugs that are absorbed through the GI tract Many drugs that are absorbed through the GI tract are substantially metabolized by the liver before are substantially metabolized by the liver before reaching general circulation. As a consequence, reaching general circulation. As a consequence, certain drugs can only be taken via certain routes. certain drugs can only be taken via certain routes.

For example, nitroglycerin cannot be swallowed For example, nitroglycerin cannot be swallowed because the liver would inactivate the medication, because the liver would inactivate the medication, but it can be taken under the tongue or but it can be taken under the tongue or transdermal (through the skin) and thus is transdermal (through the skin) and thus is absorbed in a way that bypasses the portal absorbed in a way that bypasses the portal venous system.venous system.

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A portal system is one that has two separate A portal system is one that has two separate capillary beds between the arterial supply capillary beds between the arterial supply and the final venous drainage.and the final venous drainage.

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LIVERLIVER

This is the largest internal organ of the This is the largest internal organ of the body, located on the right side, below the body, located on the right side, below the diaphragm, and extends below the costal diaphragm, and extends below the costal margin (can palpate). margin (can palpate).

It has many functions and is the most It has many functions and is the most complex organ except the brain. complex organ except the brain.

The liver has 500+ known functions.The liver has 500+ known functions.

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LiverLiver

Makes bloodMakes bloodMakes blood proteins (clotting factors)Makes blood proteins (clotting factors)Makes bileMakes bileRegulates glucose levelsRegulates glucose levelsProcesses fats Processes fats Makes cholesterolMakes cholesterolProcesses amino acidsProcesses amino acidsDetoxifies chemicals Detoxifies chemicals

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LiverLiver

With only 1/6th of your liver present your With only 1/6th of your liver present your body could continue to function. body could continue to function.

As much as 80% of your liver could be cut As much as 80% of your liver could be cut away and it would grow back to a full size away and it would grow back to a full size in approximately three months. in approximately three months.

It is usually hard to determine if the liver is It is usually hard to determine if the liver is damaged until the damage is quite damaged until the damage is quite advanced.advanced.

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LiverLiver

It has a right and left lobe, separated by It has a right and left lobe, separated by the the FALCIFORM LIGAMENTFALCIFORM LIGAMENT..The liver gets blood from 2 sources:The liver gets blood from 2 sources:Artery = Hepatic arteryArtery = Hepatic arteryVein = Hepatic portal system = Blood from Vein = Hepatic portal system = Blood from the spleen, stomach, pancreas, small and the spleen, stomach, pancreas, small and large intestines which all go through the large intestines which all go through the liver. The nutrients that are absorbed by liver. The nutrients that are absorbed by the GI tract go to the liver first for the GI tract go to the liver first for processing, then to the rest of the body.processing, then to the rest of the body.

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LiverLiver

Figure 22.22123123

INTERNAL STRUCTURE OF INTERNAL STRUCTURE OF LIVERLIVER

The liver is made of hundreds of The liver is made of hundreds of thousands of thousands of LIVER LOBULESLIVER LOBULES; each one ; each one is the size of a sesame seed, giving the is the size of a sesame seed, giving the liver a grainy texture when you eat it.liver a grainy texture when you eat it.

Each lobule carries out all of the functions Each lobule carries out all of the functions of the liver.of the liver.

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LIVER LOBULELIVER LOBULE

It has a hexagonal shape, at each corner It has a hexagonal shape, at each corner are some vessels = are some vessels = HEPATIC TRIADHEPATIC TRIAD::– ARTERIOLEARTERIOLE from the hepatic artery from the hepatic artery– VENUOLEVENUOLE from the hepatic portal vein from the hepatic portal vein– BILE DUCT, BILE DUCT, which goes to the gall bladder. which goes to the gall bladder.

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(Kupffer cells)

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LiverLiver

Figure 22.23a, c, d

Hepatic Triad: Vein, Artery, Bile Duct

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Liver Lobules

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Liver: Central vein and sinusoids

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Sinusoids Sinusoids

LIVER SINUSOIDSLIVER SINUSOIDS are channels that blood can are channels that blood can flow through. Cells that line the sinusoids are flow through. Cells that line the sinusoids are calledcalled HEPATOCYTES HEPATOCYTES, and each one faces the , and each one faces the sinusoid and is in contact with blood. sinusoid and is in contact with blood.

The hepatocytes are what carries out all of the The hepatocytes are what carries out all of the functions of the liver. functions of the liver.

If you made a machine to do the work of the If you made a machine to do the work of the liver, it would have to be the size of a large oil liver, it would have to be the size of a large oil refinery.refinery.

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Liver: sinusoids and hepatocytes

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Function of HepatocytesFunction of Hepatocytes

Detoxification of poisonsDetoxification of poisons

Picking up and processing of nutrients Picking up and processing of nutrients from the portal bloodfrom the portal blood– This includes picking up glucose from the nutrient-This includes picking up glucose from the nutrient-

rich blood coming from the small intestine and rich blood coming from the small intestine and stores it as glycogen (the storage form of glucose) stores it as glycogen (the storage form of glucose) for when the body needs it later.for when the body needs it later.

Storage of some vitaminsStorage of some vitamins

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Kupffer CellsKupffer Cells

Within the sinusoids are Within the sinusoids are KUPFFER CELLSKUPFFER CELLS, , which are macrophages. As blood flows through which are macrophages. As blood flows through the sinusoids, they phagocytize old erythrocytes. the sinusoids, they phagocytize old erythrocytes. The released Hgb is given to the hepatocytes, The released Hgb is given to the hepatocytes, which convert it to bilirubin, one of the main which convert it to bilirubin, one of the main components of BILE.components of BILE.

Bile flows through a series of channels called Bile flows through a series of channels called the the BILE CANNICULI BILE CANNICULI to the bile duct.to the bile duct.

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The Liver Destroys The Liver Destroys Old Red Blood CellsOld Red Blood Cells

By the way, when you have dark circles By the way, when you have dark circles under your eyes, it is from hemoglobin and under your eyes, it is from hemoglobin and iron deposits from broken RBC’s that iron deposits from broken RBC’s that leaked out of the delicate capillaries under leaked out of the delicate capillaries under the thin skin there.the thin skin there.

Will skin creams remove this?Will skin creams remove this?

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Problems with the LiverProblems with the Liver

HEPATITISHEPATITIS

CIRRHOSISCIRRHOSIS

JAUNDICEJAUNDICE

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Liver ProblemsLiver Problems

Infection of the liver = Infection of the liver = HEPATITISHEPATITIS (can be (can be deadly)deadly)

CIRRHOSISCIRRHOSIS is when the hepatocytes die is when the hepatocytes die and are replaced by connective tissue. and are replaced by connective tissue. This is often from alcoholism, which kills This is often from alcoholism, which kills the hepatocytes.the hepatocytes.

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JaundiceJaundice

One of the symptoms from any liver One of the symptoms from any liver disorder is a connection of the bile disorder is a connection of the bile canaliculi and the sinusoid so some canaliculi and the sinusoid so some bilirubin can enter the blood. bilirubin can enter the blood.

Bilirubin is yellow-green (later in its Bilirubin is yellow-green (later in its degradation it will turn brown and that is degradation it will turn brown and that is what gives the feces its color). what gives the feces its color).

The yellow color of bilirubin in the skin is The yellow color of bilirubin in the skin is known as known as JAUNDICEJAUNDICE. .

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JaundiceJaundice

Jaundice is not a disease; it is a symptom of Jaundice is not a disease; it is a symptom of liver disorder. liver disorder. It first shows up in the sclera because it is white It first shows up in the sclera because it is white there. The skin has other pigments, so yellow there. The skin has other pigments, so yellow doesn’t show up as well. doesn’t show up as well. Newborns get jaundice from a lot of erythrocytes Newborns get jaundice from a lot of erythrocytes being broken down, and the liver gets being broken down, and the liver gets overloaded, but it’s harmless. overloaded, but it’s harmless. The treatment is UV light or sunlight, goes away The treatment is UV light or sunlight, goes away in a few days.in a few days.

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Liver TransplantLiver Transplant

Adult-to-adult liver transplantation has Adult-to-adult liver transplantation has been done using the donor's right hepatic been done using the donor's right hepatic lobe which amounts to 60% of the liver. lobe which amounts to 60% of the liver.

Due to the ability of the liver to regenerate, Due to the ability of the liver to regenerate, both the donor and recipient end up with both the donor and recipient end up with normal liver function if all goes well. normal liver function if all goes well.

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Situs InversusSitus Inversus

Congenital condition in which the major visceral organs Congenital condition in which the major visceral organs in the thorax and abdomen are reversed or mirrored from in the thorax and abdomen are reversed or mirrored from their normal positions. their normal positions.

The heart is located on the right side of the thorax, the The heart is located on the right side of the thorax, the stomach and spleen on the right side of the abdomen stomach and spleen on the right side of the abdomen and the liver and gall bladder on the left side. and the liver and gall bladder on the left side.

The left lung is trilobed and the right lung bilobed, and The left lung is trilobed and the right lung bilobed, and blood vessels, nerves, lymphatics and the intestines are blood vessels, nerves, lymphatics and the intestines are also transposed.also transposed.

Situs inversus is generally an autosomal recessive Situs inversus is generally an autosomal recessive genetic condition, although it can be X-linked or found in genetic condition, although it can be X-linked or found in identical "mirror" twins.identical "mirror" twins.

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Situs InversusSitus Inversus

As long as there are no heart defects, the person has no As long as there are no heart defects, the person has no health issues.health issues.

However, donating an organ is more complicated, since However, donating an organ is more complicated, since the connecting blood vessels are not in the same place!the connecting blood vessels are not in the same place!

People are not aware of their condition until an unrelated People are not aware of their condition until an unrelated health issue arises, such as appendicitis, presenting on health issue arises, such as appendicitis, presenting on the left side instead of the right side. The doctor cannot the left side instead of the right side. The doctor cannot find the heart sounds in the proper location, either.find the heart sounds in the proper location, either.

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40 lb Abdominal Tumor40 lb Abdominal Tumor

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Warning!Warning!

The Government has issued a health The Government has issued a health warning not to swallow chewing gum. The warning not to swallow chewing gum. The following is a photo of what can happen:following is a photo of what can happen:

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Documents

Digestive (GI) System (Gastrointestinal System) Gastro = stomach 1