Alimentary Canal Flashcards
What hormones are responsible for acid secretion of the stomach? What effect does one have on the others?
Acetylcholine, Histamine and Gastrin are responsible for stomach growling and acid secretion. The presence of one synergistically activates the others to have a greater effect.
What are the 6 types of cells that are found in the stomach? Briefly describe each of their functions.
- Surface mucous cells - secrete mucous
- Neck mucous cells - lie within gastric pits
- Stem cells
- Parietal cells - secrete HCl in gastric pit and HCO3- that supports mucous
- Chief cells - produce pepsinogen and gastric lipase
- DNES cells - communicate stomach with nervous/endocrine systems
Name 5 of the stomach’s protective features against its contents.
- Mucous cells secrete mucous and HCO3-
- Pepsin is made in proform
- Tight junctions prevent leakage into tissue below
- Prostaglandins increase blood flow and HCO3- secretion
- Stem cells replenish eroded cells
List 3 things that are destructive to the stomach.
- HCl and active pepsin
- Stress, aspirin or NSAIDS that reduce prostaglandins
- Helicobacter pylori - ulcers and inflammation of stomach wall
What is the function of DNES cells in the stomach? What are the 2 types?
They communicate the stomach with the nervous and endocrine systems. These produce hormones that influence stomach motility and digestion. the 2 types are open (spread across lumen) and closed on basal surface).
Describe the 4 levels of folding to which the small intestines increase surface area.
- The long intestines are coiled within the body abdomen.
- Evaginations (villi) and invaginations (Crypts of Lieberkuhn) of mucosal surface
- Plicae circularies = pleated sheets of mucosa
- Microvilli on cell surfaces
List and briefly describe the 6 types of cells of the small intestines.
- Enterocytes - absorb and digest
- Goblet cells - mucous
- Paneth cells - antibacterial lysozyme, defensins
- Immune cells
- Stem cells
- DNES cells - communication
What type of tissue does the small intestine have to fight off antigens? Describe it.
Gut-associaed Lymphoid tissue (GALT) located throughout the gut contains B and T lymphocytes, mast cells, macrophages as part of the immune system. They contain Peyer’s patches which are aggregated nodules in lower parts of the intestine. M-cells take antigens and transport them into underlying cells.
What is the function of Immunoglobulin A? Describe the significance in immune response.
IgA which can be produced by active plasma cells within lymph nodes reduce adherence of antigens to epithelium and neutralize viruses/ bacterial toxins. This can go to the lamina propria of several systems (respiratory, genitals, breast milk) for an effective immune response.
Describe the levels of folding in the large intestine.
- Invaginated Crypts (no villi this time)
2. Plicae Semilunaris (half-moons)
What are the 5 cell types of the large intestine? Briefly describe each.
- Absorptive cells - ions, Vitamin K and water
- Goblet cells - increase in # going deeper
- Immune cells - [same as above]
- Stem cells - @ base
- DNES cells
What are the 2 distinguishing features of the large intestines that has it differ from the small?
- No evaginations (only invagination crypts)
2. taenia coli (modified longitudinal muscle coat)
Describe 2 ways in which the anal canal differs from the rectum.
- Stratified squamous epithelium as opposed to simple columnar.
- internal anal sphincter (circular layer of SM) and external anal sphincter (skeletal muscle)
How would a lack of functioning parietal cells affect RBC count?
Lack of parietal cells means less intrinsic factor that is needed for vitamin B12 absorption. Absence of B12 can result in Pernicious or Megaloblastic Anemia.
What is the function of Paneth Cells?
Paneth cells found at the bottom of small intestinal crypts produce lysozymes, antibacterial enzymes and factors that defend GI against bad bacteria.
