01b Normal GI structure and function Flashcards
Site of bile salt and B12 absorption
Ileum
Site of nutrient absorption
Jejunum
Lamina propria and contents
Loose connective tissue with lymph and capillaries just below and supporting epithelium. Contains lymphocytes and plasma cells. ALSO CONTAINS HISTAMINE SECRETING ECL CELLS
Submucosa
loose collagenous and adipose tissue supporting the mucosa- contains larger blood vessels and lymphatics
*innervated by meissners plexus- mucosal mvmt, BLOOD FLOW, and gland SECRETION
Adventitia
Outer layer of connective tissue surrounding GI tract outside of peritoneum
Serosa
Simple squamous epithelium (mesothelium) covers tissues within the peritoneal cavity
Langerhans cells
Dendritics in skin and mucosa
Gland layers in esophagus
Superficial mucosal glands in lamina propria- lubricating mucous
Submucosal seromucous glands– Pepsinogen, Lysozyme, mucous
Gastric juice contents
Hydrochloric acid, pepsin, rennin, gastric lipase
Gastric pit
Invagination of epithelium with connection to up to 7 Gastric glands
Contain surface mucous cells (thick protective electron dense mucous)
Gastric Glands
secrete HCL and enzymes
3parts:
Isthmus- meeting of glands parietal and surface mucous cells
Neck- Neck mucous cells (thin lubricating mucous), parietal (IF and HCL), stem cells
Base- Cheif (pepsinogen), parietal, neck mucous, ECL(histamine), Gastrin and D cells(somatostatin)
Parietal cell
Pyramidal cell secreting HCL and IF for B12 absorpton
*Secretory canaliculus - lots of mitochondria and microvilli invaginations
*Tubovesicular network (more of this means less HCL)
*Rich in Mito
“Fried egg appearance”
Chief cells
Pepsinogen, rennin, gastric lipase in apical secretory granules (secretion stimulated by secretin)
base of fastric glands
Basophilic from rER, Golgi
ECL cells
Histamine secretion (responsive to ACH) Located in Lamina propria below gastric glands
Auerbach’s plexus
Between the inner circular layer and outer longitudinal layer of muscle
Controls parastalsis
ENS
- Independent ANS modulated by brain, but works on its own
* ACH, Norepi, seritonin
Esophageal glands
Abundant in submucosal layers (like in duodenum) Mucous cells(mucous) and Serous cells (pepsinogen, lysozyme)
Esophageal muscularis propria
upper 1/3 skeletal-voluntary
Middle 1/3- mixed
Lower 1/3 - smooth, involuntary
Stomach epithelium
Simple columnar with surface mucous cells and pits
- Thick electron dense mucous that traps bicarbonate ions
- Gastric glands off of pits that dive into lamina propria
EC cells
Secrete serotonin- located in gastric glands
A cells
Secrete enteroglucagon
Enteroendocrine cells
SECRETE INTO LAMINA PROPRIA
- G cells- gastrin
- EC cells- Serotonin
- D cells- somatostatin
- A cells- Enteroglucagon
- ECL cells- Histamine
Secretin
- Stimulates secretion of pepsinogen, rennin, and gastric lipase
- Suppresses gastrin
- Suppresses GI motility
Gastric mucosa turn around
3 days
