Digestion Chapter 23

A. Two types of digestion 1. Chemical accomplished by enzymatic

breakage of chemical bonds, resulting in carbs, lipids, proteins becoming monomers again.

2. Mechanical happens as food is physically broken into smaller and smaller pieces

B. Function is to ingest, break down foodstuffs into monomers, absorb nutrients, water and eliminate the undigestible or harmful.

A. Alimentary canal, GI tract is hollow tube (30 feet) located in abdominopelvic cavity

B. 1-6 = path of food 1. Mouth 2. Pharynx 3. Esophagus 4. Stomach 5. Small & Large

Intestine 6. Rectum & Anus

C. There are Four tunics esophagus to anus.

a. mucosa secretes, absorbs and protects (has 3 layers)

b. submucosa dense connective w/ elastin, protects & nourishes

c. muscularis externa (1)inner layer is circular

muscle = peristalsis (2)outer layer is

longitudinal = segmentation

d. adventia or serosa is visceral peritoneum

1. Entry for digestive system.

2. Accessory organs are gums, teeth, tongue (lingual frenulum), uvula, soft and hard palate, salivary glands (parotid) tonsils (lingual, palantine, pharyngeal) lips and cheeks

a. Propels food toward esophagus

b. Nasopharynx, oropharynx and laryngopharynx

a. Food tube (10 inches located behind trachea) moves food by peristalsis. Esophagus is stratified squamous epithelial interspersed w/ goblet cells = mucus to help bolus slide down and a double layer of muscle.

a. Function(1) Mechanical/chemical digestion(2) Secretes enzymes, mucus and

hormones(3) Protein digestion(4) Food storageb. Anatomy (1) greater/lesser curvature(2) Fundus(3) Cardiac/pyloric regions and

sphincters (superior is gastroesophageal)

(4) Rugae(5) 3rd layers of muscle is oblique(6) Greater omentum can get quite

large

(1) mucous neck cells- acidic mucus, (2) parietal cells (red) secrete HCl

(3) chief cells (blue) secrete pepsinogen

(4) enteroendocrine cells- release hormones gastrin, CCK, histamine

a. 3 parts = 6 feet

(1) Duodenum 10 inches for absorption and final stages of digestion

(2) Jejunum 8 feet

(3) Ileum 12 feet

(4) ileocecal valve

(5)Sphincter of Oddi controls entry of brush border enzymes, while the bile duct controls entry of bile into Sl.

(6) Microvilli (on villi) increase surface area of

mucosa. They become less as distance from duodenum increases.

(7) Incidence of preyer’s patches increase as distance from duodenum increases.

(8) Brunner’s glands in submucosa = mucus

6.Plicae circulares are deep, permanent folds of mucosa and submucosa that force chyme to spiral thru the lumen, slowing its movement so that absorption can take place

(1) Duodenum (crypts)

(a)Duodenum with bile duct from the liver & pancreatic duct from pancreas, is exposed to a plethora of digestive enzymes.

(2) Jejunum

(3) Ileum (preyer’s patches)

3 parts

a. Ascending

b. Transverse

c. Descending

d. Anatomy

(1)Hepatic flexure

(2)Splenic Flexure

(3)Colon 3 inches in diameter and 5 feet long. It becomes the sigmoid colon which ends at the rectum (final 6 inches) as feces pass out anus

e. Functions

(1) to absorb water, BP, creation & elimination of feces

1. Teeth 2. Tongue3. Liver*4. Gall Bladder5. Pancreas*6. Salivary* and other *glands

a. Dental formula

Tongue ?

a. Moves food, which is now bolus

b. Initiates swallowing

c. Sensory = Taste buds

a. Liver is most versatile organ in the body w/ over 200 functions- stores glycogen, makes bile, detoxifies.

1.Right lobe of liver

2.Left lobe of liver

4. Round ligament

8. Common bile duct

9. Hepatic artery

10.Portal vein

11.Cystic duct

12.Hepatic duct

13.Gallbladder

Arranged in 4 lobules

Stores bile which emulsifies lipids

a. Located between stomach and small intestine.

b. Alpha cells synthesize & secrete pancreatic juice containing digestive enzymes and hormone glucagon.

.

a. Secrete salivary amylase starts digestion of starch

b. Helps bolus stick together