1. I. BASIC FUNCTIONS OF THE DIGESTIVE TRACT
A. Digestion—process of altering the physical state and chemical composition of food so that the body’s cells can use it B. Absorption—process by which small digested molecules pass through the cells of the intestinal tract, entering the blood and lymph

2. II. ANATOMY OF DIGESTIVE SYSTEM
A. Components
1. Alimentary Canal
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
2. Accessory Organs
Salivary glands
Liver
Gallbladder
Pancreas

3. Alimentary Canal

5. B. Wall Structure of Alimentary Canal
1. Alimentary canal is a muscular tube, 30 feet long, and located in the ventral body cavity.
Has the same four layers throughout:
a. Mucosa
Innermost layer
b. Submucosa
Loose CT with blood vessels, glands, lymph vessels, and nerves
c. Muscularis mucosa
2 layers of smooth muscle
d. Serosa
Outermost layer (visceral peritoneum)

6. Wall of the Alimentary Canal

7. C. Movement of the tube
2 Basic Movements:
1. Mixing—mixes food with juices secreted by the mucosa of the stomach
2. Propelling movements—peristalsis (wavelike contractions that force food along the digestive tube)
Mixing Peristalsis

8. 1. Mouth D. Oral Cavity Receives food
Prepares food for digestion (breaks food into small particles and mixes it with saliva)
2. Tongue
Mostly muscle
Anchored to midline of the floor of the mouth by the frenulum
Covered with papillae which contain taste buds
Movement aids in mixing food and saliva and moving food toward the rear of the mouth

9. 3. Palate
Forms roof of the mouth
Consist of hard anterior part (hard palate) and soft posterior part (soft palate)
Uvula—cone-shaped projection that hangs down from soft palate and pulls upward when swallowing to prevent food from entering the nasal cavity
4. Tonsils
Masses of lymphatic tissue
3 tonsil masses:
a. palatine
b. pharyngeal (adenoids)
c. lingual

10. Oral Cavity

11. Tonsils

12. 5. Teeth
2 sets
a. primary (deciduous)—20
b. secondary (permanent)—32
F(x): mastication (chewing)
4 types of teeth:
a. incisors—front teeth for biting
b. canine—cone-shaped for tearing food
c. bicuspids—for grinding food particles
d. molars—for grinding food particles

13. 4 Types of Teeth

15. Consists of:
crown—part above gum
root—anchored to bone by cementum and periodontal ligament
enamel—covers crown
--hardest substance in body
d. dentin—under enamel
--like very hard bone
e. pulp cavity—under dentin
--contains blood vessels, nerves, and CT

16. Tooth

17. E. Salivary Glands
1. F(x):
To secrete saliva which moisten food and begins carbohydrate digestion
Cleanses mouth and teeth
Dissolves food for taste
2. Consists of serous cells which produce amylase (enzyme that breaks down starch and glycogen) and mucous cells which secrete mucus for lubrication
3. 3 major pairs of salivary glands
a. parotids—in front of and below each ear
b. submandibular—in floor of mouth
c. sublingual—on floor of mouth under tongue

18. Salivary Glands

19. F. Pharynx
1. Common to digestive and respiratory tracts
2. Divided into 3 areas:
a. nasopharynx—passage for air during breathing
b. oropharynx—passageway for food and air
c. laryngopharynx—opens into larynx and esophagus
3. F(x):
Swallowing (deglutition)
-Voluntary but becomes involuntary as swallowing reflex is initiated
-Involves chewing and bolus (ball of partially digested food) formation

20. Pharynx

21. G. Esophagus
1. Collapsed tube about 10 inches long that connects pharynx and stomach
2. Mucous glands keep it moist and lubricated
H. Stomach
1. Anatomy
“J” shaped pouch-like organ just under the diaphragm in the upper left portion of abdominal cavity
Inner mucosa forms folds called rugae

22. 2. F(x):
Receive food
Mix food with gastric juice
Initiate protein digestion
Limited absorption
Transport partially digested food to small intestine
3. Divided into 4 regions:
a. cardiac—near esophageal opening
b. fundus—temporary storage area
c. body
d. pylorus—enters small intestine

23. Stomach

24. 4. Mucosa is thick with many gastric glands.
5. Gastric glands contain 3 types of secretory cells:
a. goblet cells—secrete mucus
b. chief cells—secrete digestive enzyme pepsinogen (inactive form of pepsin which digest proteins)
c. parietal cells—secrete hydrochloric acid (HCl) and intrinsic factor

25. Gastric Gland (Lining of Stomach)

26. 6. F(x) of gastric gland secretions:
a. mucus—protection
b. HCl—converts pepsinogen to pepsin
c. intrinsic factor—aids in absorption of vitamin B12 in small intestine
7. Regulation of Gastric Secretion
Under nerve and hormone control
Gastrin (stomach hormone) increases release of gastric juices
8. Substances absorbed in stomach:
water
glucose
alcohol
aspirin
lipid-soluble drugs

27. 9. Mixing and Emptying of Stomach
Mixing produces chyme (semisolid paste) and peristalsis moves it to the pylorus
Rate of emptying depends on the type of food present
Liquids pass through rapidly
Solids remain until well mixed with gastric juices
Fatty food remains the longest
Carbohydrates pass through the fastest

28. PANCREAS A. Structure Elongated, flattened organ
Extends horizontally across the posterior abdominal wall in the C-shaped curve of the duodenum
Pancreatic secretions enter the duodenum(small intestine) through the pancreatic duct
4. Heterocrine Gland (endocrine and exocrine)
5. Exocrine Component functions in digestion
Pancreatic acinar cells
-make up most of the pancreas
-produce pancreatic juice

29. Pancreas

30. LIVER A. Structure 1. Macroscopic Reddish-brown in color
Enclosed in a fibrous capsule
Well supplied with blood vessels
Located in the upper right side of the abdominal cavity inferior to the diaphragm
Divided into 2 lobes (large right lobe and smaller left lobe)
2. Microscopic
Each lobe is separated into many tiny hepatic lobules (functional unit of liver)
Each lobule has many hepatic (cuboidal) cells radiating outward from a central vein

31. Liver

32. Functions of the Liver
Carries out the metabolism of carbohydrates, lipids, and proteins
Storage
Stores glycogen (animal starch), iron, blood, and vitamins A, D, B12
3. Blood filtering
Removal of damaged red blood cells and foreign substances

33. III. GALLBLADDER A. Structure
1. Pear-shaped sac on the inferior surface of the liver
2. Lined with epithelial cells
3. Wall contains a strong, muscular layer
4. Connects to cystic duct which joins with the common hepatic duct to form the common bile duct which empties into the duodenum
B. Functions
Store bile
Concentrate bile by reabsorbing water
Release bile into small intestine

34. Gallstones
1. Crystals formed from cholesterol in bile
2. Can block bile flow, cause pain, and result removal of gallbladder

35. SMALL INTESTINE A. Structure Tubular organ about 20 feet long
Joins the stomach at the pyloric sphincter
Joins the large intestine at the ileocecal junction
3 Divisions:
duodenum~10 inches long and 2 in. in diameter (fixed)
jejunum~8 feet long
ileum~12 feet long
5. Jejunum and ileum are suspended by the mesentery (tissue containing blood vessels, nerves, and lymphatic vessels that supply the intestinal wall)

38. Functions of the Small Intestine
1. Completes digestion
2. Absorbs products of digestion
3. Receives secretions from pancreas and liver
4. Transports residues to large intestine

39. V. LARGE INTESTINE 5 feet long 4 Divisions of Large Intestine
A. Structure
5 feet long
4 Divisions of Large Intestine
a. Cecum
First 2-3 inches
Blind pouch to which is attached the vermiform appendix (lymphatic tissue which has no digestive function)
Opening between ileum and cecum controlled by ileocecal valve

40. Ascending (right side) Transverse (longest part)
b. Colon (4 parts)
Ascending (right side)
Transverse (longest part)
Descending (left side)
Sigmoid (S-shaped)

41. From colon to anal canal Last 1-2 inches of large intestine Anus
c. Rectum
From colon to anal canal
d. Anal Canal
Last 1-2 inches of large intestine
Anus
-opening on distal end of anal canal
-controlled by 2 sphincter muscles:
internal anal sphincter involuntary
external anal sphincter voluntary

42. Large Intestine

43. reabsorb water and electrolytes store and eliminate waste
B. Functions of the Large Intestine
secrete mucus
reabsorb water and electrolytes
store and eliminate waste

44. Undigested or unabsorbed material 75% water Color due to bile pigments
C. Feces
Solid waste
Undigested or unabsorbed material
75% water
Color due to bile pigments
Odor from bacterial activity