GIT 3, 7, 10 Physiology

Question 1

Bolus

Answer 1

The ball of chewed food and saliva that is swallowed, and travels down the esophagus to the stomach for digestion. Once the bolus reaches the stomach, it mixes with gastric juices and becomes chyme.

Question 2

Chyme

Answer 2

Chyme is the semifluid mass of partly digested food that is expelled by the stomach, through the pyloric valve, into the duodenum.

Question 3

Pyloric sphincter

Answer 3

The pyloric sphincter is the furthest part of the stomach. It lets small amounts of chyme pass from the stomach to the duodenum.

Question 4

Duodenum

Answer 4

The duodenum is the first section of the small intestine. It precedes the jejunum and ileum and is the shortest part of the small intestine, where most chemical digestion takes place. It is C-shaped, sits adjacent to the stomach, and is mostly retroperitoneal.

It is into the duodenum that the liver and gall bladder release bile and the pancreas releases bicarbonate and digestive enzymes such as trypsin, lipase and amylase.

Question 5

Histamine

Answer 5

Secreted by mast cells. Stimulates HCL secretion.

Question 6

Gastrin

Answer 6

Gastrin is a peptide hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach. It is released by G cells in the pyloric area of the stomach, duodenum, and the pancreas.

Question 7

Vagus nerve

Answer 7

The vagus nerve interfaces with parasympathetic control of the heart, lungs and digestive tract. It is the longest nerve of the autonomic nervous system in the human body. Besides giving some output to various organs, the vagus nerve comprises between 80-90% of afferent nerves conveying sensory information about the organs to the central nervous system.

Question 8

Amylase

Answer 8

Amylase is an enzyme, made by the pancreas and salivary glands, that hydrolyzes starch into di and trisaccharides. It is present in saliva where it begins the chemical process of digestion and in the stomach until it is deactivated by the stomach’s acidity.

Question 9

Pepsin

Answer 9

Pepsin is an enzyme that breaks down proteins into smaller peptides. It is produced in the stomach and its activation from pepsinogen is triggered by acid secretion.

Question 10

Lumen

Answer 10

Lumen is the inside space of a tubular structure, such as an artery, intestine, or stomach.

Question 11

Drugs that inhibit stomach acid secretion

Answer 11

Proton pump inhibitors
Prostaglandins
Histamine H2 inhibitors

Question 12

Helicobacter Pylori (H Pylori)

Answer 12

A common bacteria found in the stomach. A major risk factor for peptic ulcers. Treat by 2 antibiotics and a PPI.

Question 13

Parietal proton pump is activated by:

Answer 13

Stomach distension
Histamine
Gastrin
Acetylcholine

Question 14

Peptic ulcer

Answer 14

Peptic ulcers are break in the lining of the stomach, first part of the small intestine, or occasionally the lower esophagus. Common causes include excess acid secretion, poor mucous secretion, H pylori and non-steroidal anti-inflammatory drugs (NSAIDs).

Question 15

Zollinger-Ellison syndrome

Answer 15

Excess acid cause by gastrin secreting tumor of the pancreas.

Question 16

Exocrine gland

Answer 16

Exocrine glands produce and secrete substances onto an epithelial surface by way of a duct, while endocrine glands secrete into the bloodstream. Examples of exocrine glands include sweat, salivary, mammary, and mucous. The liver and pancreas are both exocrine and endocrine glands.

Question 17

Enteroendocrine cells

Answer 17

Enteroendocrine cells are specialized cells of the gastrointestinal tract and pancreas with endocrine function. They produce gastrointestinal hormones or peptides in response and release them into the bloodstream for systemic effect, diffuse them as local messengers, or transmit them to the enteric nervous system to activate nervous responses. Enteroendocrine cells are located in the stomach, in the intestine and in the pancreas. Include K, L G, I, N, S cells.

Question 18

G cells

Answer 18

Stomach (antrum) enteroendocrine cells, which release gastrin.

Insulin stimulates gastrin release.
Somatostatin & secretin suppress gastrin release.

Gastrin stimulates HCL production.

Question 19

S cells

Answer 19

S cells secrete secretin from the duodenum and jejunum.

Question 20

Secretin

Answer 20

Secretin is a hormone that helps regulate the pH of the duodenum by (1) inhibiting the secretion of gastric acid from the parietal cells of the stomach and (2) stimulating the production of bicarbonate.

It is a peptide hormone produced in the S cells of the duodenum.

Question 21

I cells

Answer 21

I cells secrete cholecystokinin (CCK), and are located in the duodenum and jejunum.

Question 22

Cholecystokinin (CCK)

Answer 22

Cholecystokinin is synthesized and secreted by enteroendocrine I cells in the duodenum. Its presence causes the release of digestive enzymes and bile from the pancreas and gallbladder. It also inhibits acid secretion and also acts as a hunger suppressant.

Question 23

Factors that inhibit acid secretion

Answer 23

Distension of the small intestine. 
Secretin
Somatostatin
Prostaglandins
Cholecystokinin (CCK)

Question 24

Somatostatin

Answer 24

Somatostatin is a peptide hormone that regulates the endocrine system. It inhibits insulin and glucagon secretion and can also indirectly decrease stomach acid production by preventing the release of gastrin and histamine. It effectively slows down the digestive process.

Question 25

Prostaglandin (in regards to GI)

Answer 25

Prostaglandin acts on parietal cells in the stomach wall to inhibit acid secretion. NSAIDs inhibit the production of prostaglandin, causing excessive acid production.

Question 26

Mastication

Answer 26

Chewing; mixes food and amylase, mechanically breaks up food, increases surface area.

Question 27

Salivary glands (3 x 2)

Answer 27

Sublingual
Parotid
Submandibular

Question 28

Parotid glands

Answer 28

The parotid gland is a major salivary gland. Two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. They secrete saliva through the parotid duct into the mouth to facilitate mastication and swallowing and to begin the digestion of starches.

Question 29

Sublingual glands

Answer 29

The paired sublingual glands are the smallest salivary glands. They provide only 5% of the total salivary volume.

Question 30

Submandibular

Answer 30

The paired submandibular glands are major salivary glands located beneath the floor of the mouth. They contribute some 50-60% of saliva volume. Mostly for non-stimulated lubrication.

Question 31

Saliva

Answer 31

Saliva is a watery substance secreted by the salivary glands to the mouth. Saliva comprises 99.5% water, plus electrolytes, mucus, WBCs, enzymes (amylase & lingual lipase), antimicrobial agents such as secretory IgA and lysozyme. The enzymes begin the process of digestion of starches and fats. Saliva also lubricates for swallowing.

Question 32

Dysphagia

Answer 32

Dysphagia is the medical term for the symptom of difficulty in swallowing.

Question 33

Deglutition

Answer 33

Swallowing; the process passing bolus from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis.

Question 34

Parietal Cells

Answer 34

Parietal cells are in the stomach’s gastric glands. They secrete gastric acid; HCl, pepsin, and intrinsic factor.

Parietal cells are stimulated by histamine, acetylcholine and gastrin.

Question 35

Chief Cells

Answer 35

Chief Cells are also in the stomach’s gastric glands. They are responsible for production of pepsinogen and gastric lipase, an inactive precursor of pepsin, which degrades proteins.

Question 36

Goblet Cells

Answer 36

Goblet cells are located at the top of the gastric glands. They produce the mucous that help protect the stomach from self-digestion.

They also exist in small intestine.

Question 37

Muscular layers of stomach

Answer 37

The stomach is made of 3 layers of smooth muscle. The innermost layer is oblique is not seen in other parts of GI and responsible for the churning motion. The next layers are the circular and longitudinal.

Question 38

Epithelium of the stomach

Answer 38

The stomach epithelium forms deep pits, called gastric glands, which contain chief, parietal, and goblet cells. They produce gastric acid, pepsinogen, and mucous.

Question 39

2 Digestive enzymes of the stomach:

Answer 39

Pepsinogen (breaks proteins into peptide chains) and Gastric Lipase (begins breakdown of fats).

Question 40

Intrinsic factor

Answer 40

Secreted by parietal cells. Essential for B12 absorption in the ilium.

Question 41

Pancreatic enzyme secretions

Answer 41

Pancreatic Proteases: Trypsinogen, chymotrypsinogen, proelastase.

Pancreatic Amylase

Pancreatic Lipase.

Question 42

Brush border enzymes

Answer 42

Surface enzymes of the small intestine that finalize digestion into absorbable monomers.

Maltase, Sucrase, isomaltase, lactase.

Question 43

Microcytic anemia

Answer 43

Less than normal MCV. Iron deficiency is the most common cause of microcytic anemia

Question 44

Normocytic anemia

Answer 44

MCV within range. However, the hematocrit and hemoglobin is decreased. Normally cause by a decrease in RBC production (could be a B vitamin deficiency) or blood loss.

Question 45

Macrocytic anemia

Answer 45

Cells are larger because they cannot produce DNA quickly enough to divide at the right time as they grow. Causes of the DNA synthetic problem range from lack of certain vitamins needed to produce DNA (folate and B12), to poisons or inhibitors of DNA replication, such as an antiviral drug and chemotherapeutic agents

Question 46

Hypochromic anemia

Answer 46

A normal red blood cell will have an area of pallor in the center of it. In hypochromic cells, this area of central pallor is increased. This decrease in redness is due to a disproportionate reduction of red cell hemoglobin.

Hypochromic is normally coupled with microcytic anemia.