Human Anatomy Physiology Chapter 5 The Digestive System and Body Metabolism

Human Anatomy & Physiology

Chapter 5The Digestive System and Body Metabolism

The Digestive System and Body The Digestive System and Body MetabolismMetabolism

Slide 14.1Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

DigestionBreakdown of ingested food

Absorption Passage of nutrients into the blood

Metabolism Production of cellular energy (ATP)

Organs of the Digestive SystemOrgans of the Digestive System

Slide 14.2a

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Two main groups Alimentary canal – continuous coiled hollow

tube Accessory digestive organs

Organs of the Digestive SystemOrgans of the Digestive System

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Figure 14.1

Organs of the Alimentary CanalOrgans of the Alimentary Canal


Mouth Pharynx Esophagus Stomach Small intestine Large intestine Anus

Mouth (Oral Cavity) AnatomyMouth (Oral Cavity) Anatomy


Lips (labia) – protect the anterior opening

Cheeks – form the lateral walls

Hard palate – forms the anterior roof

Soft palate – forms the posterior roof

Uvula – fleshy projection of the soft palate

Figure 14.2a



Vestibule – space between lips externally and teeth and gums internally

Oral cavity – area contained by the teeth

Tongue- used for swallowing and taste

Figure 14.2a



Tonsils Palatine tonsils Lingual tonsil

Figure 14.2a

Processes of the MouthProcesses of the Mouth


Mastication (chewing) of food Mixing masticated food with saliva

Saliva begins digestion of carbohydrates

Initiation of swallowing by the tongue Allowing for the sense of taste

Pharynx AnatomyPharynx Anatomy


Nasopharynx – not part of the digestive system

Oropharynx – posterior to oral cavity

Laryngopharynx – below the oropharynx and connected to the esophagus

Figure 14.2a

Pharynx FunctionPharynx Function


Food movement is by alternating contractions of the muscle layers (peristalsis)

Serves as a passageway for air and food

Food is propelled to the esophagus by two muscle layers

It’s like pushing a pea down a straw

EsophagusEsophagus

Slide 14.10


Connects the mouth to the stomach Runs from pharynx to stomach through

the diaphragm Conducts food by peristalsis

(slow rhythmic squeezing) Passageway for food only

Layers of Alimentary Canal OrgansLayers of Alimentary Canal Organs

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Mucosa Innermost layer Moist membrane

Surface epithelium Small amount of connective tissue

(lamina propria) Small smooth muscle layer


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Submucosa Just beneath the mucosa Soft connective tissue with blood vessels,

nerve endings, and lymphatics


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Muscularis externa – smooth muscle Inner circular layer Outer longitudinal layer

Serosa Outermost layer – visceral peritoneum Layer of serous fluid-producing cells


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Figure 14.3

Stomach AnatomyStomach Anatomy

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Located on the left side of the abdominal cavity

About the size of a fist Food enters at the cardioesophageal

sphincter Connects the

Esophagus to the

Stomach


Slide 14.15b


Regions of the stomach Cardiac region – near the heart Fundus- top “bubble” area Body- majority/mass of the organ Pylorus – funnel-shaped terminal end

Food empties into the small intestine at the pyloric sphincter


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Rugae – internal folds of the mucosa External regions

Lesser curvature Greater curvature


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Layers of connenctive tissue attached to the stomach Lesser omentum – attaches the liver to the

lesser curvature Greater omentum – attaches the greater

curvature to the posterior body wall Contains fat to insulate, cushion, and

protect abdominal organs


Slide 14.17


Figure 14.4a

Stomach FunctionsStomach Functions

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Acts as a storage tank for food Chemical breakdown of protein begins Mucus protects the cells from chemical

digestion Delivers chyme (processed food) to the

small intestine

Specialized Mucosa of the Specialized Mucosa of the StomachStomach

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Simple columnar epithelium Mucous neck cells – produce a sticky

alkaline mucus Gastric glands – secrete gastric juice Chief cells – produce protein-digesting

enzymes (pepsinogens) Parietal cells – produce hydrochloric acid Endocrine cells – produce gastrin

Structure of the Stomach MucosaStructure of the Stomach Mucosa

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Figure 14.4b, c

Small IntestineSmall Intestine

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Functions include: Neutralizes acids from stomach Uses enzymes to break down

carbohydrates, fats and proteins Site of nutrient absorption into the

blood

Subdivisions of the Small IntestineSubdivisions of the Small Intestine““Dogs Just Itch!Dogs Just Itch!

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Duodenum Attached to the stomach Curves around the head of the pancreas

Jejunum Attaches anteriorly to the duodenum

Ileum Extends from jejunum to large intestine

Digestion in the Duodenum Digestion in the Duodenum

Slide 14.57a


Enzymes do the following: Break double sugars into simple sugars Complete some protein digestion

Pancreatic enzymes play the major digestive function Help complete digestion of starch

(pancreatic amylase) Carry out about half of all protein digestion

Digestion in the Duodenum Digestion in the Duodenum

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Pancreatic enzymes play the major digestive function (continued) Responsible for fat digestion (lipase) Digest nucleic acids (nucleases)

Chemical Digestion in the Small Chemical Digestion in the Small IntestineIntestine

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Figure 14.6

Digestion in the Jejunum/Ileum Digestion in the Jejunum/Ileum

Majority of the nutrients are absorbed in the lining of the small intestine where they are transported to the liver for processing

Specialized structures, called villi aid in the absorption by increasing surface area

Villi of the Small IntestineVilli of the Small Intestine

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Fingerlike structures formed by the mucosa

Give the small intestine more surface area

Figure 14.7a

Microvilli of the Small IntestineMicrovilli of the Small Intestine

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Small projections of the plasma membrane of each cell in the villi

Found on absorptive cells

Figure 14.7c

Structures Involved in Absorption Structures Involved in Absorption of Nutrientsof Nutrients

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Absorptive cells Blood capillaries

Figure 14.7b

Absorption in the Small IntestineAbsorption in the Small Intestine

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Some water is absorbed along the length of the small intestine

End products of digestion Most substances are absorbed by active

transport through cell membranes Lipids are absorbed by diffusion

Propulsion in the Small IntestinePropulsion in the Small Intestine

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Peristalsis is the major means of moving food

Segmental movements Mix chyme with digestive juices Aid in propelling food

Large IntestineLarge Intestine

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Larger in diameter, but shorter than the small intestine

Frames the internal abdomen

Large IntestineLarge Intestine

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Figure 14.8

Functions of the Large IntestineFunctions of the Large Intestine

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Absorption of water Eliminates indigestible food from the

body as feces Does not participate in digestion of food Goblet cells produce mucus to act as a

lubricant

Structures of the Large IntestineStructures of the Large Intestine

Slide 14.30a


Cecum – saclike first part of the large intestine

AppendixAccumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis)

Hangs from the cecum


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Colon Ascending- upward region Transverse-across region Descending- downward region S-shaped sigmoidal- near the end

Rectum- stores feces for removal Anus – external body opening


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Colon Ascending Transverse Descending S-shaped sigmoidal

Rectum Anus – external body opening

Food Breakdown and Absorption in Food Breakdown and Absorption in the Large Intestinethe Large Intestine

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No digestive enzymes are produced Resident bacteria digest remaining

nutrients Produce some vitamin K and B Release gases

Water and vitamins K and B are absorbed Remaining materials are eliminated via

feces

Propulsion in the Large IntestinePropulsion in the Large Intestine

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Sluggish peristalsis causes defecation Mass movements

Slow, powerful movements Occur three to four times per day

Presence of feces in the rectum causes a defecation reflex Internal anal sphincter is relaxed Defecation occurs with relaxation of the

voluntary (external) anal sphincter

What are feces made up of?What are feces made up of?

Slide 14.32


1. Bilirubin from dead blood cells (which gives it a brown hue)

2. 75% water3. 1/3 of the remaining is dead bacteria that

help digest food4. Remaining portion is indigestible food

(fiber,) fats, proteins, cholesterol, phosphate salts, and mucus from the intestines

Fecal matterFecal matter

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The seven types of stool are:1.Separate hard lumps, like nuts (hard to pass) 2.Sausage-shaped but lumpy 3.Like a sausage but with cracks on its surface 4.Like a sausage or snake, smooth and soft 5.Soft blobs with clear cut edges (passed easily) 6.Fluffy pieces with ragged edges, a mushy stool 7.Watery stool, entirely liquid.

http://upload.wikimedia.org/wikipedia/commons/b/b4/Bristol_Stool_Chart.png

What do the different colors mean?What do the different colors mean?

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Color variation is normal; however certain persistent changes in stool color are characteristic for specific conditions:black, foul-smelling stool: intestinal bleeding (typically from the stomach and upper small intestine) due to ulcers, tumors; ingestion of iron or bismuth maroon stool: intestinal bleeding (from the middle intestine or proximal colon) due to ulcers, tumors, Crohn's disease, ulcerative colitis clay-colored stool: lack of bile due to blockage of the main bile duct pale yellow, greasy, foul-smelling stool: malabsorption of fat due to pancreatic insufficiency, as seen with pancreatitis, pancreatic cancer, cystic fibrosis, celiac disease

Accessory Digestive OrgansAccessory Digestive Organs

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Salivary glands Teeth Pancreas Liver Gall bladder

Salivary GlandsSalivary Glands

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Saliva-producing glands Parotid glands – located anterior to ears Submandibular glands Sublingual glands

SalivaSaliva

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Mixture of mucus and serous fluids Helps to form a food bolus

Contains salivary amylase to begin starch digestion

Dissolves chemicals so they can be tasted

TeethTeeth

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The role is to masticate (chew) food Humans have two sets of teeth

Deciduous (baby or milk) teeth 20 teeth are fully formed by age two

TeethTeeth

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Permanent teeth Replace deciduous teeth beginning

between the ages of 6 to 12 A full set is 32 teeth, but some people do

not have wisdom teeth

Classification of TeethClassification of Teeth

Slide 14.36a


Incisors Canines Premolars Molars

Classification of TeethClassification of Teeth

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Figure 14.9

Regions of a ToothRegions of a Tooth

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Crown – exposed part Outer enamel Dentin Pulp cavity

Neck Region in contact

with the gum Connects crown to

rootFigure 14.10

Regions of a ToothRegions of a Tooth

Slide 14.37b


Root Periodontal

membrane attached to the bone

Root canal carrying blood vessels and nerves

Figure 14.10

PancreasPancreas

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Produces a wide spectrum of digestive enzymes that break down all categories of food

Enzymes are secreted into the duodenum Alkaline fluid introduced with enzymes

neutralizes acidic chyme Endocrine products of pancreas

Insulin Glucagons

LiverLiver

Slide 14.39


Largest gland in the body Located on the right side of the body

under the diaphragm Consists of four lobes suspended from

the diaphragm and abdominal wall by the falciform ligament

Connected to the gall bladder via the common hepatic duct

BileBile

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Produced by cells in the liver Composition

Bile salts Bile pigment (mostly bilirubin from the

breakdown of hemoglobin) Cholesterol Phospholipids Electrolytes

Role of the Liver in MetabolismRole of the Liver in Metabolism

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Several roles in digestion Detoxifies drugs and alcohol Degrades hormones Produce cholesterol, blood proteins

(albumin and clotting proteins) Plays a central role in metabolism

Gall BladderGall Bladder

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Sac found in hollow fossa of liver Stores bile from the liver by way of the

cystic duct Bile is introduced into the duodenum in

the presence of fatty food Gallstones can cause blockages

Processes of the Digestive SystemProcesses of the Digestive System

Slide 14.42a


Ingestion – getting food into the mouth Propulsion – moving foods from one

region of the digestive system to another


Slide 14.42b


Peristalsis – alternating waves of contraction

Segmentation – moving materials back and forth to aid in mixing

Figure 14.12


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Mechanical digestion Mixing of food in the mouth by the tongue Churning of food in the stomach Segmentation in the small intestine


Slide 14.44


Chemical Digestion Enzymes break down food molecules into

their building blocks Each major food group uses different

enzymes Carbohydrates are broken to simple sugars Proteins are broken to amino acids Fats are broken to fatty acids and alcohols


Slide 14.45


Absorption End products of digestion are absorbed in

the blood or lymph Food must enter mucosal cells and then

into blood or lymph capillaries

Defecation Elimination of indigestible substances as

feces

Control of Digestive ActivityControl of Digestive Activity

Slide 14.47a


Mostly controlled by reflexes via the parasympathetic division

Chemical and mechanical receptors are located in organ walls that trigger reflexes

Body Energy BalanceBody Energy Balance

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Energy intake = total energy output (heat + work + energy storage) Energy intake is liberated during food

oxidation Energy output

Heat is usually about 60% Storage energy is in the form of fat or

glycogen

Cirrhosis of the Cirrhosis of the liverliver Cirrhosis is a condition in which

the liver slowly deteriorates and malfunctions due to chronic injury. Scar tissue replaces healthy liver tissue, partially blocking the flow of blood through the liver

Caused by alcohol and drug abuse,

Hepatitis C, B, D Obesity Cystic fibrosis and other

inherited diseases Infection

Stenosing web of Stenosing web of the esophagusthe esophagus

Esophageal stenosis is a condition where there is a narrowing of the esophagus.

With an esophageal stenosis, an abnormal change or injury may have caused inflammation (swelling) and damage to the esophagus.

When the damaged areas heal, scar tissue forms and make the affected area of the esophagus hard.

This narrows the esophagus and causes problems for foods and liquids to pass through.

Causes: Acid reflux (most common,) cancer, allergies and trauma

Gall Gall Stones Stones Small, pebble-like objects in the

gall bladder made of bile salts and cholesterol.

The cause of gallstones varies. There are two main types of gallstones:

Stones made of cholesterol, which are by far the most common type. Cholesterol gallstones have nothing to do with cholesterol levels in the blood.

Stones made of bilirubin, which can occur when red blood cells are being destroyed. This leads to too much bilirubin in the bile. These stones are called pigment stones.

Inflammatory Bowel Inflammatory Bowel DiseaseDisease

Inflammatory bowel disease (which is not the same thing as irritable bowel syndrome, or IBS) refers to two chronic diseases that cause inflammation of the intestines: ulcerative colitis and Crohn's disease.

Current evidence suggests that a genetic defect affects how the immune system works and how inflammation is triggered in response to an offending agent, like bacteria, a virus, or a protein in food.

Duodenal ulcerDuodenal ulcer A duodenal ulcer is a type of

peptic ulcer that occurs in the duodenum, the beginning of the small intestine.

Peptic ulcers are eroded areas in the lining of stomach and duodenum, which result in abdominal pain, possible bleeding, and other gastrointestinal symptoms.

The most common cause of duodenal ulcer is a stomach infection associated with the Helicobacter pylori (H pylori) bacteria.

Intussusception Intussusception caused by polypcaused by polyp

Intussusception (in-tuh-suh-SEP-shun) is a serious disorder in which part of the intestine — either the small intestine or colon — slides into another part of the intestine.

This "telescoping" often blocks the intestine, preventing food or fluid from passing through. Intussusception also cuts off the blood supply to the part of the intestine that's affected.

Intussusception is the most common cause of intestinal obstruction in children but it is rare in adults.

Most cases of adult intussusception are the result of an underlying medical condition. In contrast, most cases of intussusception in children have no demonstrable cause.

Stomach Ulcers Stomach Ulcers Over 25 million Americans will have a peptic ulcer once in their lifetime

Peptic ulcer is an area of damage to the inner lining of the stomach,

Peptic ulcers were formerly thought to be caused by stress, coffee consumption, or spicy foods.

60% of peptic ulcers are caused by a bacterial infection

Another 20% are caused by nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen another 20% have miscellaneous causes such as cigarettes

Diverticulitis is small, bulging sacs or pouches of the inner lining of the intestine (diverticulosis) that become inflamed or infected.

No one knows exactly what causes the sacs, or pouches of diverticulosis to form. Eating a low-fiber diet is one of the most likely causes.

People who eat mostly processed food, as many Americans eat, do not get enough fiber in their diet. Processed foods include white rice, white bread, most breakfast cereals, crackers, and pretzels.◦ As a result, constipation and hard stools are more likely to occur - causing people to strain

when passing stools. This increases the pressure in the colon or intestines and may cause these pouches to form.

Diverticulosis is very common. It is found in more than half of Americans over age 60.

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Human Anatomy Physiology Chapter 5 The Digestive System and Body Metabolism