Bio104 - MCCC



Bio104 Lecture Outline - Digestive System 1/05

[Martini, 1st ed. Chapters 22 & 23] L. Falkow, Course Coordinator

I. Introduction

A. Components of Digestive system

1. Digestive tract (GI tract) -

2. Accessory organs -

B. Functions

1. Ingestion

2. Mechanical processing

3. Digestion

4. Secretion

5. Absorption

6. Excretion

C. Membranes

1. Peritoneum

parietal

visceral

retroperitoneal

2. Mesenteries

3. Omenta:

lesser omentum

greater omentum

4. Disorders:

ascites - accumulation of fluid in abdominal cavity

Symptoms:

peritonitis

II. Overview of the Digestive Tract

A. Histological Organization

[Mucosa, Submucosa, Muscularis externa, Serosa]

1. Mucosa

a. epithelial layer:

- stratified squamous (wear and tear)

or

- simple columnar (absorption)

enteroendocrine cells

plicae (transverse folds)

b. lamina propria

c. muscularis mucosae

2. Submucosa

a. dense irregular CT

submucosal plexus (Meissner’s plexus)

3. Muscularis externa

a. SMC

inner circular

outer longitudinal

myenteric plexus (Auerbach plexus)

4. Serosa

a. serous membrane

adventitia -

B. Movement of Digested Substances

1. Peristalsis -

bolus

2. Segmentation - in small intestines & part of L.I.

C. Regulation of Digestion

1. Neural

- myenteric

2. Hormonal

III. Oral (buccal) Cavity

A. Components: tongue, salivary glands, teeth

oral mucosa

cheeks - lateral

- buccinator muscles

vestibule

gingiva

soft palate

uvula

palatoglossal arch - anterior

palatopharyngeal arch - posterior

fauces

hard palate

bones -

B. Functions

1. analysis

2. mechanical processing

3. lubrication

4. digestion (limited)

C. Tongue

1. lingual lipase

2. papillae

- filiform

- fungiform

- circumvallate

3. lingual frenulum

ankyloglossia

D. Salivary glands

1. Three pairs:

a. Parotid salivary glands

parotid duct (Stensen's duct)

b. Sublingual salivary glands

sublingual ducts (Rivinus' ducts)

c. Submandibular salivary glands

submandibular ducts (Wharton's ducts)

2. Saliva

a. Components:

Salivary amylase (ptyalin)

b. Functions:

3. Disorder:

Mumps

E. Teeth

enamel

dentin

pulp cavity

dentition formula: 3 2 1 4 1 2 3

4 - incisors

1 - cuspids (canines)

2 - bicuspids (premolars)

3 - tricuspids (molars)

IV. Pharynx

- common passageway for 2 systems

A. Divisions

nasopharynx

oropharynx

laryngopharynx

B. Tonsils

palatine tonsils -

lingual tonsils -

pharyngeal tonsil -

V. Esophagus

A. Anatomy

25 cm long (extends from level of C6 to T7)

esophageal hiatus

upper esophageal sphincter

lower esophageal sphincter (cardiac sphincter)

B. Histology

mucosa -

submucosa -

muscularis - upper 1/3

middle 1/3

lower 1/3

adventitia

C. Deglutition

1. buccal phase

2. pharyngeal phase

3. esophageal phase

D. Disorders

achalasia

esophagitis

reflux (GERD)

VI. Stomach

A. Functions

1. storage

2. mechanical breakdown

3. chemical digestion

4. produces intrinsic factor

chyme-

B. Anatomy

1. Features

lesser curvature (medial surface)

greater curvature (lateral surface)

4 regions:

cardia

fundus

body

pylorus

pyloric sphincter

rugae

2. Muscularis externa

- inner oblique

- middle circular

- outer longitudinal

3. Histology

simple columnar epithelium

gastric pits

gastric glands:

- parietal cells

---> intrinsic factor

---> HCl

- chief cells

---> pepsinogen --> pepsin

---> rennin

---> gastric lipase

- mucous cells --> mucus

pyloric glands:

G cells ---> gastrin

D cells ---> somatostatin

4. Regulation of Gastric Activity

neural

hormonal

- gastrin

- CCK

- GIP

- secretin

local response

C. Digestion and Absorption

VII. Small Intestines

6 meters long

90% of absorption

A. Divisions

1. duodenum

- submucosal glands (Brunner's glands)

2. jejunum

- absorption

3. ileum

ileocecal valve

aggregate lymphoid nodules (Peyer's patches)

B. Histology

1. plicae

2. mucosa

intestinal villi

lacteal

chylomicrons

3. intestinal crypts (or glands)

[crypts of Lieberkuhn]

C. Intestinal Juice

1. Functions:

- moistens chyme

- buffers acids

- liquifies enzymes (from pancreas) and products of digestion

2. Enzymes (brush border)

enterokinase (enteropeptidase)

3. Hormones (from enteroendocrine cells)

gastrin

CCK

secretin

VIII. Accessory Glands

[Pancreas, Liver, and Gall Bladder]

A. Pancreas

1. Anatomy

head

body

tail

pancreatic duct (duct of Wirsung)

accessory duct (duct of Santorini)

2. Histology

pancreatic acini

pancreatic islets (Islets of Langerhans)

alpha cells ----->

beta cells ------>

3. Physiology

Enzymes

- pancreatic amylase (carbohydrase)

- pancreatic lipase

- nucleases

- proteolytic enzymes (proteases, peptidases)

Proenzymes:

- trypsinogen ---> _________

- chymotrypsinogen —> __________

- procarboxypeptidase —> __________

B. Liver

1. Anatomy

lobes: right, left, quadrate, caudate

ligaments: falciform

round

2. Histology

liver lobule

hepatocytes

central vein

Kuppfer cells ( stellate reticuloendothelial cells)

sinusoids

3. Bile Secretion and Transport

hepatocytes -

bile canaliculi ---> bile ductules ---> right & left hepatic ducts

---> common hepatic duct ---> common bile duct

4. Physiology

Functions:

a) Regulation of metabolism

1) CHO metabolism

2) Lipid metabolism

3) Amino acid metabolism

4) Removal of wastes

5) Vit. and mineral storage

6) Drug breakdown

b) Hematologic functions

1) Phagocytosis of damaged/old RBCs

2) Synthesis of plasma proteins

3) Removal of hormones and antibodies and toxins

4) Synthesis of bile

C. Gallbladder

Stores and concentrates bile

Releases bile into cystic duct

Stimulated by CCK (cholecystokinin):

- between meals: hepatopancreatic sphincter (sphincter of Oddi)

around the duodenal ampulla closes

- after a meal: CCK is released (from duodenum) and causes

*

*

Disorders:

cholelithiasis

D. Hormonal Regulation

1. CCK

2. Secretin

3. Gastric Inhibitory Peptide (GIP)

4. Gastrin

IX. Large Intestines

[cecum; ascending, transverse, descending, sigmoid colon, rectum, anus]

1.5 m

A. Cecum

ileocecal valve

vermiform appendix

B. Colon

haustra

taenia coli

epiploic appendages

ascending, transverse, descending, sigmoid colon

C. Rectum

last 15 cm of GI tract

rectal columns

anus (anal orifice)

internal anal sphincter

external anal sphincter

Disorders:

hemorrhoids

colon cancer

D. Histology

- lack of villi

- lots of goblet cells

- intestinal glands

E. Physiology of Large Intestine

1. reabsorption of water

2. vitamin synthesis -

3. formation of feces

4. storage of waste material

F. Disorders

diarrhea vs. constipation

diverticula/ diverticulosis/ diverticulitis

inflammatory bowel disease

Crohn’s disease

X. Digestion and Absorption

A. CHO digestion

B. Lipid Digestion

C. Protein Digestion

D. Water Absorption

[pic]

Histological Structure of Digestive Tract

[pic]

Salivary Glands

[pic]

Stomach

[pic][pic]

Plica and Villi Villus

[pic]

Liver

[pic]

Gallbladder and Duodenum

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