Lecture 1 - GIT Structure and Function Flashcards
What are the jobs of the GIT (7)
Motility
Secretion
Digestion
Absorption
Communication
Immune system
Detoxification/modification via metabolism
What is secreted by the GIT
Electrolytes, water, digestive enzymes, bile salts, acid, base
Why is GIT motility important
Mixes digesta to be maximally exposed to epithelial cells
Moves digesta down GIT with muscles
What does GIT breakdown do
Breakdown foods into simpler chemical compounds
What does GIT absorption do
Transfer nutrients to circulation
Role of GIT communication
With the nervous system, endocrine system, etc
Full? Hungry? Nauseous?
What are the major components of the GI tract
Mouth, pharynx, esophagus, forestomach (ruminants), stomach, small intestine, cecum & large intestine
What are the sections of the forestomach
Rumen, reticulum, omasum
Parts of the small intestine
Duodenum -> jejunum -> ileum
Major players of a birds GIT
Crop -> pro-ventriculus -> gizzard -> SI -> LI
How does body size affect transit time in fully mature dogs
Once GIT fully mature, transit time is similar despite size differences in breeds
The esophagus has stratified squamous intestinal arrangement… why?
Many layers because we are not trying to absorb anything, but they need to be protective
The mucosa layer contains
The epithelial cell layer
Connective tissue
Lamina propria
Muscle layer
Four different microscopic layers of the small intestine
Mucosa
Submucosa
Muscularis externa
Serosa
The muscularis externa includes what kinds of muscle.
Circular muscle, longitudinal muscle
The serosa includes…
Connective tissue
Periotneum
Lamina propria is includes..
Capillaries, nerve fibers, smooth muscle, immune cells, arteriole, venuole, lymphatic
The submucosa contains…
Nerves, glands (if present)
What are the types of epithelial cells**
Columnar absorptive cells
Mucous (goblet) cells
Enteroendocrine cells
Paneth cells
Intestinal stem cells
What do enteroendocrine and paneth cells do
Enteroendocrine = releases hormones into blood circulation to communicate locally and systemically
Paneth = secrete antimicrobial molecules to provide host defense against gut
Which type of cell gives rise to the other types of epithelial cells
Intestinal stem cells
How often do cells replace
Every 3-5 days
What happens to the villi of germ free cells
They elongate, have narrow lamina properia
Where do cells replicate? Which cells replicate?
Intestinal stem cells replicate in the crypt
Why do SI epithelial cells have a lot of mitochondria/rough endoplasmic reticulum?
Mitochondria bc they need a lot of ATP
RER because they produce a lot of proteins
What keeps harmful agents out of absorption
Tight junctions between cells
What proteins form a tight junction
Occludin, claudin, zona occludin
What damages tight junctions causing impairment
Inflammatory cytokines
Reactive oxygens
Pathogenic bacteria
Stress
Microvilli increase…
Surface area/absorptive surface
What kind of intestinal arrangement does the esophagus have
Stratified squamous
