gi anatomy

Question 1

function of esophagus?

Answer 1

Tube-shaped muscular conduit for food and fluids
Connects the throat to the stomach
Movement of food is facilitated by:
Secretion of mucus
Very strong muscle movement to propel food towards the stomach

Question 2

function of esophageal sphincter

Answer 2

Food is prevented from movement backwards by 2 sphincters (bundles of muscle)

**Normally closed at rest
The upper esophageal sphincter prevents food and fluids from being aspirated into the lungs.
The lower esophageal sphincter (LES)
- AKA Cardiac Sphincter
- Separates the esophagus from the stomach
- Prevents acidic contents of the stomach from entering back into the esophagus

Question 3

functions of stomach

Answer 3

Elastic reservoir for food, mixing, and initial digestion of proteins
Normal capacity is 1000-1500 ml
Lined with columnar epithelium containing millions of gastric glands
These glands contain special cells that secrete HCl, intrinsic factor, and gastrin

Question 4

layers of stomach

Answer 4

Mucosa layer- Inner layer made up of special cells:
G-cells, parietal, chief, and epithelial cells

• Also contains blood vessels

Two muscle layers
- Help propel food from stomach to small intestine

Serosa- Outer layer- Acts as covering for inner layers

Question 5

what are the gastric cells in the mucosa?

Answer 5

G-cells
Produce gastrin, a hormone that facilitates production of HCL

Parietal cells
Produce Hydrochloric acid (HCl) to help break down food
Produce Intrinsic factor (IF) to protect mucosa

Chief cells
Secrete pepsin

Epithelial cells
Secrete bicarbonate-rich solution to coat and protect mucosa

Question 6

parts of the small intestine

Answer 6

Approximately 5-6 meters long
Duodenum
First 22 cm

Jejunum
Next 2 meters

Ileum
Forms the remainder

Question 7

function of small intestine

Answer 7

The entire inner wall has circular folds of a mucous membrane called plicae circulares
The plicae circulares are permanent ridges that contain millions of fingerlike projections called intestinal villi
Each villus has its own microscopic projections called microvilli
The combined effect of circular folds, villi, and microvilli increases the surface area for digestion x600

Question 8

cells of the small intestine

Answer 8

Crypts of LieberkühnIntestinal glands that secrete about 2 L of fluid/day into lumen of intestine
Fluid quickly reabsorbed by villi

Goblet cells and Brunner glands
Secrete large amounts of mucus to protect small intestine from damage of acidic gastric juices
Small intestine cells have a rapid turnover (48-72 hours), one of the fastest turnover rates in the body

Question 9

small intestine sphincter

Answer 9

The ileocecal sphincter is the area where food passes from the small into the large intestine
Distention of terminal ileum causes relaxation to allow contents to enter large intestine
Distention of cecum prevents reflux back into ileum

Question 10

large intestine description

Answer 10

1.5 meters long; muscular tube that forms a frame around the small intestine 6.5 cm in diameter (greater than the diameter of the small intestine, hence its name)

Includes the appendix, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum

Question 11

cells of large intestine

Answer 11

The mucosa of the large intestine does not have villi and does not produce digestive enzymes

Absorptive cells absorb water and electrolytes

Goblet cells produce mucousEndocrine cells are present and produce hormones, but their function is not really understood

The turnover of large intestine cells is 3-8 days

Question 12

2 types of GI motility?

Answer 12

Motility is due to contraction of 2 layers of smooth muscle (longitudinal and circular)

There are 2 types of GI motility:
Propulsive (peristalsis)
Mixing (segmental)

GI motility is regulated by the enteric nervous system, autonomic nervous system, and hormones