GI 01 & 02: GROSS ANATOMY AND BASIC PHYSIOLOGY Flashcards
What are the 4 main functions of the GI tract (and what is the fifth that textbooks often leave out)?
Motility, digestion, absorption, secretion, and excretion
What causes motility?
Contractions of smooth muscle in the gut lining
With regard to food particle size, what does motility contribute?
Helps reduce the size of the particles (helps in the breakdown process of food size). This allows for increased contact of area of food with chemicals and the mixing of those chemicals with food
With regard to motility, what do we think of as its main main function
Propels food in the caudad direction
Is the rate of mobility important?
Yes, it is going to happen at a rate that is best for full breakdown (digestion) and absorption of ingested food (ex. apples down to fructose)
What is secretion
The release of enzymes from cells in the GI lumen
What kinds of cells participate in secretion?
Epithelial cells lining the GI tract and associated glandular organs
What are the major associated glandular organs that participate in secretion
Gall bladder, pancreas, salivary glands, liver
What is the digestion process?
The process by which large macromolecules are broken down into smaller micromolecules
Why is digestion critical?
A whole apple isn’t useful to us but individual fructose is- therefore digestion is required to get things to absorbable levels of size
What are the two aspects of digestion?
Physical and chemical breakdown (mixing via strong muscles and enzymes)
What is the process of absorption?
Nutrients and water are moved from GI lumen into the blood
What are the reasons we need to absorb nutrients
Energy
Building blocks for other shit
parts of metabolic pathways
Regulation of all physiological activitie
What is the process of excretion
Waste –> bye bye
This includes storage and excretion of ingested food that goes through, but also products from the liver such as steroids, drug metabolites, and cholesterol
Why is it important that the GI tract has an immunocological function?
It’s exposed to the external environment - we can consider the GI tract the largest immune organ in the body
Connection between gut microbiome and immunity
They’re linked (as gut microbiome increases so does immunity and this tracks with age)
What are the major functional segments of the GI tract
- mouth and pharynx
- esophagus
- stomach
- small intestine (duodenum, jejunum, ileum)
- large intestine (colons)
- rectum
- anus
Associated glandular organs of Gi tract
- salivary glands
- pancreas
- liver
- gall bladder
- associated endocrine glands in gastric walls
What are sphincters
specialized circular smooth muscle
What are the sphincters of the GI tract
- Upper esophageal
- lower esophageal
- Pyloric
- sphincter of oddi (the one at the GB/pancreas/small intestine junction)
- ileocecal
- internal (involuntary) and external (voluntary) anal sphincter
Layers of gut wall
- mucosa
- submucosa
- muscularis externa
- serosa
What is the mucosa
Innermost layer of gut wall, made of epithelium, lamina propria, and muscularis mucosae
What is gut epithelium?
Single layer of continuous cells linked by tight junctions - can consist of many specialized groups
absorptive enterocytes
Most abundant epithelial cell in gut, play vital role in digestion and absorption