anatomy of GI mod 5 Flashcards
Structure:
Consists of the GI tract and the related solid organs of digestion
7 continuous meters from mouth to anus
Begins to form as early as 4th week of gestation
Functions
Provide nutrients for the body with propulsive and mixing movements
Secretion of digestive juices
Absorption of nutrients
function of esophagus?
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
function of esophageal sphincter
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
functions of stomach
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
layers of stomach
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
what are the gastric cells in the mucosa?
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
parts of the small intestine
Approximately 5-6 meters long
Duodenum
First 22 cm
Jejunum
Next 2 meters
Ileum
Forms the remainder
function of small intestine
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
cells of the small intestine
Crypts of Lieberkühn
Intestinal 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
small intestine sphincter
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
large intestine description
- 5 meters long; muscular tube that forms a frame around the small intestine
- 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
cells of large intestine
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 mucous
Endocrine cells are present and produce hormones, but their function is not really understood
The turnover of large intestine cells is 3-8 days
2 types of GI motility?
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
