Digestive Organs

Overview

Digestive System

Overview

Digestive System

• Alimentary Canal (Gastrointestinal Tract)

The continuous tube that carries food from the mouth to the anus.

Overview

Digestive System

• Alimentary Canal (Gastrointestinal Tract)

The continuous tube that carries food from the mouth to the anus.

• Accessory Digestive Organs

Organs that contribute to the digestionof food even though food does not passdirectly through these organs.

OverviewDigestive Processes

OverviewDigestive Processes

Mechanical Digestion: The physical breakdown of food.Ex: Grinding of the teeth or churning of the stomach.

OverviewDigestive Processes

Mechanical Digestion: The physical breakdown of food.Ex: Grinding of the teeth or churning of the stomach.

Chemical Digestion: The catabolic breakdown of food usingenzymes and acids.

OverviewDigestive Processes

Mechanical Digestion: The physical breakdown of food.Ex: Grinding of the teeth or churning of the stomach.

Chemical Digestion: The catabolic breakdown of food usingenzymes and acids.

Absorption: The passage of digested food from the lumen ofthe GI Tract into the blood or lymph.

Structures andFunctions of the Digestive System

Mouth

Mouth

• Tongue: Mixes food.

Mouth

Mouth

• Teeth: Tear and grind food.

Mouth

Teeth: Tear and grind food.

LayersEnamel

Dentin

Pulp

Mouth

Teeth: Tear and grind food.

Types

Mouth

Teeth: Tear and grind food.

Types

Incisors - chisel-shaped - cutting

Mouth

Teeth: Tear and grind food.

Types

Canines - “eye-teeth” - tearing

Mouth

Teeth: Tear and grind food.

Types

PremolarsMolars

- Broad crowns- grinding

Mouth

• Salivary Glands: Moisten food and contain enzymes for the breakdown of starchy foods.

Salivary Glands

• Three pairs of major salivary glands (parotid, submandibular, and sublingual glands) and numerous smaller ones secrete saliva into the oral cavity, where it is mixed with food during mastication. Saliva contains water, mucus, and enzyme amylase.

Functions of saliva include the following:• It has a cleansing action on the teeth. • It moistens and lubricates food during mastication and

swallowing. • It dissolves certain molecules so that food can be tasted. • It begins the chemical digestion of starches through the action

of amylase, which breaks down polysaccharides into disaccharides

PharynxCommon passageway for food and air.

Pharynx

Esophagus

Propels food to the stomach via “peristalsis.”

Esophagus

Stomach

Storage of food and digestion of protein.

Stomach

Stomach (in detail)Curvatures

GreaterCurvature

LesserCurvature

Stomach (in detail)

Sphincters GastroesophagealSphincter

PyloricSphincter

Stomach (in detail)

Regions

Fundus

Body

PyloricAntrum

Stomach (in detail)

Rugae

Rugae: Large, longitudinal folds of the mucosa

Small IntestineMajority of digestion and absorption occurs here.

Small Intestine - SectionsDuodenum

• First 10 inches of the small intestine.• Collects bile from the liver.• Collects pancreatic juices from the pancreas.• “Sphincter of Oddi” controls entry of the bile and juices.

Small Intestine - Sections

Jejunum - Next 8 feet.

Ileum - Final 12 feet.

Ileocecal Valve - The small intestine joinsthe cecum of the large intestine.

Large Intestine

Large Intestine (“Colon”)Absorbs water and some nutrients.

Large Intestine - Sections

1. Cecum

2. Ascending Colon

3. Transverse Colon

4. Descending Colon

5. Sigmoid Colon

6. Rectum7. Anus

Large Intestine - cont.

Taniae coli: Smoothmuscle that causes thecolon to “pucker.”

Haustra: Pocket-like sacs.

Appendix: Containslymphoid tissue that aidsthe immune system.

Accessory Organs of Digestion

Liver: Produces bile to aidin the digestion of lipids.

Accessory Organs of Digestion

Gallbladder: Stores bile untilit is released into the smallintestine.

• The liver is stimulated by the hormones “secretin” and “cholecystokinin” (CCK) to produce bile.• The bile enters the right and left hepatic ducts and travels to thecommon hepatic duct. The bile is stored in the gallbladder.• The gallbladder is stimulatedto release the bile by thevagal nerve and CCK.• The bile enters the duodenum via thebile duct.

Bile Secretion in Detail

Common hepatic duct

Right and left hepatic ducts

Gallbladder Bile duct

Duodenum

Accessory Organs of Digestion

Pancreas: Produces many typesof enzymes used in the small intestine to digest food.

Pancreatic Juice Secretion in Detail

Pancreas

DuodenumMain pancreatic duct

• The hormones cholecystokinin and secretin stimulate the release ofpancreatic juices by the pancreas.• The juices travel through the pancreatic ducts to enter theduodenum.

Control of Digestion - Nervous System

Two Phases:

• “Cephalic Phase” - Triggered by the site,smell, and taste of food. This stimulates thestomach to prepare for the entry of food.

Control of Digestion - Nervous System

Two Phases:

• “Cephalic Phase” - Triggered by the site,smell, and taste of food. This stimulates thestomach to prepare for the entry of food.

• “Gastric Phase” - Stomach distension by foodstimulates the release of gastric juices.

Control of Digestion - Hormones

• Gastrin - Produced by the stomach; stimulatesthe release of gastric juices.

Control of Digestion - Hormones

• Gastrin - Produced by the stomach; stimulatesthe release of gastric juices.

• Secretin - Produced by the small intestine; stimulates the pancreas and gall bladder to releasepancreatic juices and bile.

Control of Digestion - Hormones

• Gastrin - Produced by the stomach; stimulatesthe release of gastric juices.

• Secretin - Produced by the small intestine; stimulates the pancreas and gall bladder to releasepancreatic juices and bile.

• Cholecystokinin (CCK) - Produced by the smallintestine; stimulates the pancreas and gall bladder to release pancreatic juices and bile.

Digestive Tract

Digestive Disorders

Peptic Ulcer

•Lesions in the wall of the stomachor duodenum.•Primarily caused by bacteria.•Treated with antacids AND antibiotics.

Digestive Disorders

Appendicitis

•Usually caused by fecal obstructionor anatomical “kinking” of the appendix.•A rupture leads to peritonitis (ouch)

Digestive Disorders

Peritonitis

(Inflammation of the Peritoneum)

• Usually results from an infection caused by a external or internal penetrating wound.• Bacteria from intestinesenter the sterile areas of the body

surrounding the digestive system.• May cause death if not treated with highdoses of antibiotics.

Digestive Disorders

Hepatitis

(Inflammation of the liver)•Caused by drugs, chemicals, viruses,alcohol, etc.•Viral “Hepatitis A” is usually causedby the ingestion of food.•Viral “Hepatitis B” and “Hepatitis C”are “blood-borne” pathogens.

Digestive Disorders

Diverticulitis

•Small bulges (herniations) of the mucosa in The large intestine.•These areas can become inflamed andpossibly rupture.•Prevention is the treatment of choice. Adiet high in fiber will help prevent diverticulitis.

Diverticulitis

Digestive Disorders

Emesis(Vomiting)

•Can be caused by microbes, allergies,gluttony, poisons, etc.

Digestive Disorders

Diarrhea

•Movement of fecal material throughthe GI Tract too rapidly.•May be caused by microbes, spicyfoods, stress, etc.

Digestive Disorders

Constipation

•Infrequent defecation of fecal

material.•Usually caused by a diet low in

fiber and water.

Digestive Disorders

Cirrhosis of the Liver

•Condition where liver cells are

destroyed and replaced by fibrousconnective tissue.•Alcoholism is a common cause of

cirrhosis.

Digestive Disorders

Gall Stones(Biliary Calculi)

•Crystalization of cholesterol and bile salts.•Blocks the bile duct or fills the gallbladder.

Gallstones: MRI showing transverse section of abdomen

Digestive Disorders

Jaundice

•Build-up of bile in the skin causinga yellowing of the skin.•May be caused by damage to the liver,gall bladder, or any of the ducts thatservice these organs.

Jaundice

Digestive Disorders

Buliemia Nervosa

•Condition where a patient binges onfood and then purges with either laxatives or vomiting.•Considered a psychological disorderwhere the patient has a fear of gainingweight.•Treated with psychotherapy.

Digestive Disorders

Anorexia Nervosa

• Psychological disorder where the patienthas a false perception of their own weight.• Patient denies their own appetite.• Patients are usually 15 - 20 % below normalbody weight.• Extreme cases are lethal.• Closely associated with bulimia nervosa.

False perception

of my weight.

It can affect

men and women

It should never be considered

“fashionable”

Digestive Disorders

Flatulence

•Excessive intestinal gas resultingfrom bacteria in the intestines, diet,or swallowing air.