GI: Functional Anatomy Flashcards
What comprises the GI tract?
- alimentary tract
- accessory glands
List the main functions of the GI tract.
- motility
- secretion
- digestion
- absorption
- excretion
- immunological functions
Describe the motility function of the GI tract. What are the outcomes?
- smooth muscle contractions of the GI tract propel food through the tract
- reduces food particle sizes => increased surface area for chemical enzymatic digestion
- mixes foods with enzymes
- rate of motility is optimized for digestion and absorption
Describe the secretion function of the GI tract.
GI tract and glands release enzymes, mucus, water, and ions to aid in digestion and absorption
Describe the digestion function of the GI tract.
Since macromolecules can’t be absorbed, the GI tract breaks them down into smaller molecules (carbs, amino acids, lipids)
Describe the absorption function of the GI tract.
absorbed particles = nutrients, electrolytes, water function = energy, catabolism, reactions, metabolism
What does the GI tract excrete?
- food waste
- liver waste
Describe the immunological functions of the GI tract.
- largest immune system because constantly exposed to external environment
Track the segments of the GI tract.
mouth => pharynx => esophagus => stomach => duodenum => jejunum => ileum => colon => rectum => anus
List the accessory glandular organs.
- salivary
- pancreas
- liver
- gallbladder
- endocrine cells
List the sphincters in order.
- upper esophageal (between pharynx and esophagus)
- lower esophageal (between esophagus and stomach)
- pyloric (between stomach and duodenum)
- sphincter of Oddi (connects liver/gallbladder, pancreas, and duodenum)
- ileocecal
- external and internal anal sphincters
How much of CO enters splanchnic circulation?
25%
List the major splanchnic arteries and what organs they supply.
- celiac = stomach, liver, spleen
- superior mesenteric = pancreas, small intestine, ascending/transverse colon
- inferior mesenteric = descending colon
Describe portal circulation.
venous blood goes first to the liver via the portal vein and then to the heart via the hepatic vein => IVC
Describe lymphatic drainage
- important for lipid soluble molecules that are too large for systemic circulation
- enter the lymph vessels => thoracic duct => systemic
List the layers of the GI tract.
- mucosa
- submucosa
- muscularis externa
- serosa
List the layers of the mucosal lining.
- epithelium
- lamina propria
- muscularis mucosae
Describe the following cells of the epithelial lining:
- absortive enterocytes
- enteroendocrine cells
- gastric mucosal cells
- mucin-producing cells
- absorptive enterocytes - vital for digestion and absorption
- enteroendocrine cells - regulation of GI tract via peptides and amines
- gastric mucosal cells - produce protons
- produce mucin
Compare esophageal vs intestinal epithelium.
- esophageal = no absorptive cells; peristalsis movement
- intestinal = villi and crypts for absorption
Describe GI lining renewal.
- proliferative stem cells reside in the crypts (bottom of villus)
- they travel along the villus as they grow and mature
- at the tip of the villus, they die and slough off after 3-5 days
Describe the structure of a villus
crypts
microvilli brush border
What happens if you have an impaired surface area of the villi?
malabsorption
ex: celiac’s disease
Describe the lamina propria.
- just below epithelium
- rich in connective tissue
- contains glands: nerves, vessels, lymph
Describe the muscular mucosae.
- below the lamina propria
- contraction aids in movement
