The Digestive System

3 Functions of the digestive system

• DIGESTION

• ABSORPTION

• ELIMINATION

Digestion

• Starts in the mouth

• Ends in the anus

• Food can be broken down mechanically (chewing) and chemically (with enzymes) to be digested (broken down).

Absorption

• Digested food enters into the bloodstream through the walls of the small intestine.

• Cells burn the energy (sugar, fatty acids, and amino acids) in the presence of oxygen to release stored energy within the food.

Elimination

• The digestive system eliminates materials that cannot be used in the body via elimination.

• The large intestine concentrates these solid wastes, called FECES, and finally the waste passes out of the body through the anus.

Inside the Oral Cavity

• The gastrointestinal tract (GI tract) begins with the oral cavity.

• Oral (or/o = pertaining to the mouth)• The cheeks form the walls of the oval

shaped oral cavity, and the lips surround the opening of the cavity.

• The hard palate form the anterior portion of the roof of the mouth.

• The soft palate consists of the muscular membrane that lies posterior to it.

The Oral Cavity

The Oral Cavity

• The uvula is the small tissue projection that hangs from the soft palate (hangy ball)

• The uvula helps with the production of the sounds of speech.

• The tongue covers the floor of the oral cavity, aids in moving the food during mastication (chewing) and deglutition (swallowing).

•Ruage are the bumps on the top of the hard palate.

The Oral Cavity

• Papillae, small raised bumps on the tongue, contains taste buds.

• Taste buds are sensitive to food chemicals and allow discrimination of different tastes as the food moves across the tongue.

Papillae

• Some people think that every bump on their tongue is, itself, a taste bud, but that is NOT true.  – Each papillae has many taste buds within it.  – In addition, we have taste buds that are not

even on our tongues.  – Some taste buds are found in our throats,

cheeks, and in the roof of our mouths.

Papillae

Taste Regions

Tonsillitis

The Oral Cavity

• The gums are fleshy tissue that surrounds the sockets of the teeth.

• The adult human has 32 teeth (16 permanent teeth top/16 bottom arch).

Central incisor (1)

Lateral incisor (2)

Canine (3)

First premolar (4)

Second premolar (5)

First molar (7)

Third Molar (wisdom tooth) (8)

Salivary Glands

• 3 pairs in the oral cavity• Produce saliva, that

contain digestive enzymes.

• Saliva is released from the parotid gland, submandibular gland and sublingual gland on EACH side of the mouth.

• Narrow ducts carry saliva into the oral cavity.

The Oral Cavity

• Together the teeth and saliva breakdown food in the oral cavity.

Components of the Digestive System

• Esophagus

• Stomach

• Small Intestine

• Large Intestine

• Gall bladder

• Liver

• Pancreas

Esophagus

• Muscular tube that connects your mouth to your stomach.

• 9-10 inches from the pharynx to the stomach.

• Peristalsis is the involuntary, progressive, rhythmic contraction of muscles in the walls of the esophagus (and other gastrointestinal organs) propelling a bolus (mass of food) toward the stomach.

Stomach

• A stretchy bag that holds your food after you eat

• Helps to break food into smaller pieces so your body can use it for energy and nutrition

Stomach

Esophagus

The Stomach3 parts: Fundus (upper portion)

Body (middle section)

Antrum (lower portion)

FUNDUS

BODY

ANTRUM

Inside the Stomach

• Folds in the lining of the stomach are called rugae.

• The rugae contain digestive glands that produce the enzyme pepsin (to begin digestion of proteins) and hydrochloric acid.

• Food leaves the stomach in 1 to 4 hrs or longer, depending on the type/amount of food eaten.

Sphincters• Rings of muscles • Control the opening and

closing of the stomach• Lower esophageal

sphincter (cardiac sphincter) relaxes and contracts to move food from the esophagus to the stomach.

• Pyloric sphincter allows food to move from the stomach to the intestine.

Small Intestine

• Tube that is 20 feet long.

• Continues to digest food

• Food stays in your small intestine for 4 to 8 hours

Small Intestine

Small Intestine

• 20 feet from the pyloric sphincter to the first part of the large intestine.

3 parts of the small intestine:

1. DUODENUM2. JEJENUM3. ILEUM

The Small Intestine

• Lined with VILLI• Tiny microscopic

projections • Microscopic blood

vessels in the villi absorb the digested nutrients into the bloodstream and lymph vessels.

Duodenum

• 1 foot long• Receives food from the stomach • Bile from the gallbladder• Pancreatic juice from the pancreas

• Enzymes and bile help digest food before it passes to the second part of the small intestine.

Large Intestine

• Tube that is 5 feet long

• Gets waste from small intestine

• Waste stays for 10 to 12 hours

The Large Intestine

• Receives the fluid waste from digestion (the material that is unable to pass into the bloodstream).

• It stores the waste until they can be released from the body.

Large Intestine

Large Intestine

• The appendix hangs from the large intestine.

• The appendix has no clear function but can become inflamed and infected when clogged or blocked.

• Thought to be involved with breakdown of plants during primitive life.

Large Intestine Sections

The Large Intestine

• Absorbs water within the waste material allowing the body to expel solid feces (stools).

• Defecation is the expulsion or passage of feces from the body through the anus.

• Diarrhea, or watery stools, results from reduced water absorption into the bloodstream through the walls of the large intestine.

Gall Bladder

• Storage tank for bile (a greenish-yellow liquid) that helps your body break down and use fats

• Located under your liver and is shaped like a pear

• After you eat the gallbladder contracts, forcing the bile into the cystic duct into the common bile duct.

Gall Bladder

Liver

1. Maintain proper sugar levels (glucose)

2. Manufacture blood proteins (blood clotting)

3. Releasing Bilirubin, a pigment in bile

4. Remove Poisons (toxins) from the blood.

Liver

The Liver

• Produces BILE • Bile contains cholesterol

(a fatty substance), bile acid, and bile pigments.

• Bilirubin – produced from the breakdown of RBCs in normal RBC destruction.

• Bilirubin travels to the liver through the bloodstream, where it is conjugated with another substance and added to bile.

• Bilirubin enters the intestine with bile.• Bacteria in the colon breakdown bilirubin into pigments that gives feces its brown color.• Bilirubin and bile leave the body in feces.

Jaundice

• Occurs when bilirubin can’t leave the body.

• Causes a yellowish discoloration of the skin, whites of the eyes, and mucous membranes.

Pancreas

• Helps you digest food by breaking down carbohydrates, fats and proteins.

Recap..can you

remember the food

path?

Hernia

• A hernia is the protrusion of an organ through a wall that normally contains it.

• There are many different types of hernias and several involve organs in the digestive system.

• An inguinal hernia for example is when part of the intestine protrude through the abdominal wall. It appears as a bulge in the skin and can be very painful.

Hernia• A hiatal hernia occurs when the upper

part of the stomach protrudes upward through the diaphragm. This condition can lead to GERD (gastroesophageal reflux disease).

Heartburn• Has nothing to do with the heart - it is a

digestive problem • Heartburn is a pain behind the breast bone,

often described as ‘burning’ in quality. • Acid is present in the stomach to digest food.

Heartburn occurs when small amounts of this acid rise up into the esophagus - the tube which carries food from the mouth to the stomach. This is called reflux.

• The gullet, unlike the stomach, does not have a protective lining. So when it is exposed to the acid, it can become inflamed and painful.

Anorexia• Anorexia is an eating disorder classified as a refusal to

maintain a minimally normal body weight. • Lack of appetite (-orexia = appetite)• A sign of malignancy or liver disease.• It is a loss of appetite caused by emotional problems such as

anger, anxiety, and fear.• The individual is intensely afraid of gaining weight and has a

disturbance in the perception of the shape or size of his/her body.

• Predominantly affects adolescent females, and its principal symptom is a conscious, relentless attempt to diet along with excessive, compulsive over activity, such as exercise, running, or gymnastics.

• Most postmenarchal females with this disorder are amenorrheic.

Bulimia• Bulimia Nervosa is an eating disorder

that is characterized by binge eating (uncontrolled indulgence in food) followed by purging (eliminating food from the body).

• Individuals maintain normal or nearly normal weight because after binging they engage in inappropriate purging. – E.g. self-induced vomiting and the misuse of

laxatives or enemas.