1. Digestion part II

2. Stomach Anatomy
The stomach is located on the left side of the abdominal cavity and is about 10 inches long
Cardioesophageal sphincter – smooth muscle that opens to allow food into the stomach from the esophagus
Regions of the stomach
Cardiac region – superior; near the heart; entrance from esophagus
Fundus – superior region of stomach
Body – middle region of stomach
Pylorus – funnel-shaped terminal end; inferior region of stomach
Pyloric sphincter – Ring of smooth muscle that opens to allow small amounts of food into the small intestine

3. Stomach Anatomy
Rugae – internal folds of the mucosa; can expand to hold about a gallon of food
External regions 1) Lesser curvature – concave medial surface
2) Greater curvature – convex lateral surface
Oblique Muscle Layer - an additional third layer of muscle under the longitudinal and circular muscle layers of the muscularis externa
Allows the stomach to churn, mix, and pummel the food (besides moving it along)

4. Stomach Anatomy
Figure 14.4a

5. Stomach Anatomy Layers of peritoneum attached to the stomach
Lesser omentum – attaches the liver to the lesser curvature
Greater omentum – attaches the greater curvature to the posterior body wall
Contains fat to insulate, cushion, and protect abdominal organs

6. Stomach Anatomy

7. Stomach Functions 1) Acts as a storage tank for food
2) Site of food breakdown
3) Chemical breakdown of protein begins
4) Chyme (processed food) is delivered to the small intestine

8. Structure of the Stomach Mucosa
Figure 14.4b–c

9. Structure of the Stomach Mucosa
Gastric pits formed by folded mucosa
Glands and specialized cells are in the gastric gland region

10. Specialized Mucosa of the Stomach
Simple columnar epithelium
Mucous neck cells – produce a sticky alkaline mucus (what is up with that spelling Mucous or mucus???)
Gastric glands – secrete gastric juice with 3 types of cells
1) Chief cells – produce protein-digesting enzymes (pepsinogens)
2) Parietal cells – produce hydrochloric acid
3) Enteroendocrine cells – produce gastrin d

11. Small Intestine
The body’s major digestive organ; approximately 20 ft in length.
Site of nutrient absorption into the blood
Muscular tube extending form the pyloric sphincter to the ileocecal valve
Mesentery – shiny connective tissue that suspends the small intestine from the posterior abdominal wall

12. Subdivisions of the Small Intestine
Duodenum
1) Attached to the stomach
2) Curves around the head of the pancreas
3) First 10 – 12 inches
Jejunum
1) Attaches anteriorly to the duodenum
2) About 8 ft.
Ileum
1) Extends from jejunum to large intestine and attaches at the ileocecal valve
2) Last 12 ft (approx)

13. Villi of the Small Intestine
Villi are fingerlike structures formed by the mucosa
Villi give the small intestine more surface area
Figure 14.7a

14. Microvilli of the Small Intestine
Microvilli - Small projections of the plasma membrane
Further increases the surface layer for absorption of nutrients
Figure 14.7c

15. Structures Involved in Absorption of Nutrients
1) simple columnar epithelium – make up the Absorptive cells of the small intestine
2) Blood capillaries
3) Lacteals (specialized lymphatic capillaries)
Figure 14.7b

16. Chemical Digestion in the Small Intestine
Figure 14.6

17. Chemical Digestion in the Small Intestine
Source of enzymes that are mixed with chyme
Pancreas - Produces a wide spectrum of digestive enzymes that break down all categories of food
Enzymes are secreted into the duodenum
Alkaline fluid introduced with enzymes neutralizes acidic chyme
Endocrine products of pancreas – Homeostatic Mechanism
Insulin – carries blood sugar (glucose) into cells. Also stimulates the storage of glucose as glycogen in the liver.
Produced by Beta Cells in Pancreatic Islets
If a person lacks Beta Cells or “Burns them out” by eating too much sugar Diabetes results.

18. Chemical Digestion in the Small Intestine
Glucagons – stimulate the breakdown of glycogen into glucose when sugar levels are low – releases glucose
Produced by Alpha Cells in Pancreatic Islets
Mainly happens in the Liver
One molecule of glucagon can release 100 million molecules glucose!

19. Liver Largest gland in the body – about 3 lbs
Located on the right side of the body under the diaphragm
Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament
Connected to the gall bladder via the common hepatic duct
Diseases
Cirrhosis – chronic inflammation of the liver usually due to alcohol abuse – causes “beer gut”
Hepatitis – inflammation of the liver due to viral infection.
Hepatitis B – transmitted by needles/sexual contact much like AIDS. Can easily lead to Liver Cancer

21. Bile Produced by cells in the liver Made up of: 1) Bile salts
2) Bile pigment (mostly bilirubin from the breakdown of hemoglobin)
3) Cholesterol, Phospholipids, Electrolytes

22. Chemical Digestion in the Small Intestine
Figure 14.6

23. Gall Bladder Sac found in hollow fossa of liver
Stores bile from the liver by way of the cystic duct – much more concentrated in gall bladder
Bile is introduced into the duodenum in the presence of fatty food
Bile emulsifies fats – makes them watery
Gallstones can cause blockages which are caused by the crystallization of cholesterol

24. Large Intestine
Larger in diameter, but shorter than the small intestine
Frames the internal abdomen

25. Structures of the Large Intestine
Cecum – saclike first part of the large intestine
Ileocecal Valve – structure that allows undigested food into the large intestine (works like the sphincters)
Appendix
Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis) pain in the right side of your body
Hangs from the cecum
Colon
Ascending (up)
Transverse (across)
Descending (down)
S-shaped sigmoid (between descending colon and rectum)
Rectum
Anus – external body opening
Internal anal sphincter – smooth muscle and involuntary
External anal sphincter – skeletal muscle and voluntary; gives some control

26. Large Intestine
Larger in diameter, but shorter than the small intestine
Frames the internal abdomen

27. Modifications to the Muscularis Externa in the Large Intestine
Smooth muscle is reduced to three bands (teniae coli)
Muscle bands have some degree of tone
Haustra - pocketlike sacs that form the walls of the large intestine.

28. Functions of the Large Intestine
1) Absorption of water to “dry out” indigestible food
2) Eliminates indigestible food from the body as feces
Fiber is extremely important in this phase of the digestion process
Fiber helps increase the movement of feces through the L. Intestine so that carcinogens don’t have a chance to “sit around”
Should be eliminating feces at least once a day.
Foods high in fiber: whole grains (like oatmeal etc.), fruit, vegetables)
3) Does not participate in digestion of food
4) Goblet cells produce mucus to act as a lubricant