GI and Hepatics

Question 1

Retroperitoneal Organs (GI Tract)

Answer 1

Esophagus
Some of the duodenum
Ascending and descending colon,
Pancreas (except for tail end)
Rectum

Question 2

Histological organization of the digestive tract

Answer 2

Mucosa
Submucosa
Muscularis externa
Serosa

Question 3

Mucosa of digestive tract

Answer 3

1. Stratisfied squamous (oral cavity, pharynx, esophagus, anal canal)
2. Areolar connective tissue
3. Muscularis mucosae (internal circular and external longitudinal smooth muscles)

Question 4

Submucosa of digestive tract

Answer 4

Dense, irregular connective tissue with many blood and lymph vessels; some with submucosal glands

Question 5

Muscularis externa of digestive tract

Answer 5

Layer of smooth muscles; circular on the inside and longitudinal on the outside.
Myenteric plexus lies between to too smooth muscle layers.

Question 6

Serosa of digestive tract

Answer 6

Loose connective tissue with blood and lymphatic vessels. Adventitia connects digestive tract to surrounding structrues.

Question 7

Movement of digestive materials through GI tract

Answer 7

1. Peristalsis (contractions of circular smooth muscle layer followed by contractions of longitudinal smooth muscle layer)
2. Segmentation (churning and fragmentation to mix bolus with intestinal secretion)

Question 8

Histology of the Esophagus

Answer 8

Nonkeratinized, stratisfied squamous epithelium

Upper 1/3 is skeletal, middle 1/3 is skeletal and smooth, lower 1/3 is smooth muscle.

Question 9

Histology and anatomy of the Stomach

Answer 9

Simple columnar epithelium
Rugae - folds within to allow for expansion
Gastric pits and glands (mucus and gastrin production)

Question 10

Histology of Small Intestines

Answer 10

Simple columnar epithelium
Circular folds with microvilli increases surface area for 90% of reabsorption of nutrients (brush borders)
Lacteals absorbs materials not able to enter capillaries

Question 11

Anatomy of Large Intestines

Answer 11

Large diameter but thinner walls than small intestines.

Abundant in goblet cells to produce mucus which houses intestinal bacteria.

Question 12

Gastric glands and their secretions

Answer 12

1. Parietal cells (intrinsic factor and H+/Cl- via ATPase and alkaline tide respectively)
2. G-cells (gastrin; stimulates parietal and chief cell secretion, and motility)
3. Chief cells (pepsinogen which is converted to the enzyme pepsin for protein digestion)
4. D cells (somatostatin; opposes gastrin)
5. P/D1 cells (ghrelin - inducing hunger; antagonist to leptin)

Question 13

Sections of the small intestines

Answer 13

Duodenum, jejunum and ileum

Question 14

Function of the Duodenum

Answer 14

Receives chyme and neutralizes acids
Absorption of nutrients
Receives secretion from gallbladder and pancreas
Produce hormones

Question 15

Hormones secreted in the duodenum

Answer 15

1. Gastrin - G cells (increase gastric motility and acids/enzymes)
2. Secretin - cells in small intestines (increase buffer secretion by pancreas and bile from by liver; reduces motility and secretory rates)
3. Cholecystokinin - cells in the duodenum and jejunum (stimulates gallbladder contraction to release bile and pancreatic enzymes)
4. Gastric inhibitory peptide
5. Vasoactive intestinal peptide (stimulates secretion of intestinal glands, dilates regional capillaries, inhibits gastric acid production)
6. Enterocrinin (alkaline mucus production)

Question 16

Function of the Jejunum

Answer 16

Majority of absorption is in the duodenum and jejunum

Question 17

Function of the Ileum

Answer 17

Absorbs bile salt and vitamin B12

Ileocecal valve controls chyme entering the cecum / large intestines

Question 18

Anatomy and division of Large Intestines

Answer 18

1. Cecum (begin compaction of chyme)
2. Ascending, transverse, descending, sigmoid (H20 reabsorption, propelling chyme through to anus and producing Vitamin K and B5 and biotin)
3. Rectum (stores feces, stretch receptors stimulation induces defecation)

Question 19

Function of the Pancreas

Answer 19

1. Endocrine - pancreatic acini; simple cuboidal
   - – secretes H20, bicarbonate and phosphate buffer to neutralize acidic chyme (stimulated by secretin)
   - – secretes digestive enzymes (stimulated by cholecystokinin)
2. Exocrine - islet of Langerhans
   - – alpha cells - glucagon (breakdown of glycogen)
   - – beta cells - insulin (build glycogen, metabolize glucose into fat storage or ATP synthesis)

Question 20

Anatomy of Liver

Answer 20

Upper right quadrant

Right and left lobe separated by falciform ligament

Question 21

Blood supply of Liver

Answer 21

Portal vein and hepatic artery enters the portal triad.

Question 22

Histology of Liver

Answer 22

Consist of hepatic lobules (basic functional unit)
Hepatocytes line the lobules like spokes on a wheel
Sinusoids runs between lines of hepatocytes to central vein.

Question 23

Role of Liver

Answer 23

1. Metabolic regulation: carbohydrates, lipid, amino acid, waste removal, vitamin storage (A, D, E, K, B12), mineral storage, drug inactivation)
2. Hematologic regulation: phagocytosis and antigen presentation, synthesis of plasma proteins (albumin), removal of circulating hormones, antibodies and toxins
3. Bile production: by hepatic cells into bile salts via cholesterol, digests lipids

Question 24

Biliary system and its digestive function

Answer 24

Helps in lipid digestion through emulsification or breakdown of fat droplets by bile salts which then promotes lipid absorption through the intestinal epithelium.
Bile / bile salts are produced in the liver and stored in the gallbladder.

Question 25

Vitamin B12 Deficiency

Answer 25

Intrinsic factor (produced by parietal cells) binds to vitamin B12 for absorption in the terminal ileum. No intrinsic factor reduces vitamin B12 absorption leading to pernicious anemia.

Question 26

Gastroesophageal reflux disease (GERD)

Answer 26

Lower esophageal sphincter only opens to let chyme pass; in GERD the LES does not close completely

Question 27

Lactose intolerance

Answer 27

Inability to digest lactose due to the inability to produce enough lactase.