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46 Cards in this Set
- Front
- Back
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4 ways to increase surface area in SI
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plicae circularis
villi MV glycocalyx |
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Stomach General Features
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no absorption, except H2O and some salts
produces chyme by mixing and partial digestion mucosa, submucosa, muscularis externa, and serosa layers |
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3 Regions of Stomach
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Cardiac: near esophagus, contains cardiac glands
Pyloric: near pyloric sphincter, contains pyloric glands Fundic: b/t cardiac and Pyloric, contains fundic or gastric glands |
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Gastric Mucosa
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Rugae: longitudinal folds of mucosa and submucosa, does NOT alter surface area
Gastric Pits: opening in mucosal surface, glands open into bottom of pits |
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Stomach Epithelium
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Simple columnar
called "surface mucous cells" stains intensely with toluidine blue or PAS mucous secretion forms thick coat that adheres to epithelial surface Function: absorption of water, salts, and lipids |
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Gastric Glands
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composed of mucous neck cells, chief cells, parietal cells, enteroendocrine cells, and undifferentiated cells
Isthmus- site of cell replication Secrete: HCL, Pepsin, Mucus, and Intrinsic Factor |
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Gastric Gland Isthmus
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site of cell replication in gastric glands
migrate upwards to become surface mucus cells migrate downwards to become chief, parietal, mucus neck and enteroendocrine cells |
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Stomach Pepsin
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produced by chief cells
converted from pepsinogen by HCL |
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Stomach Mucus
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secreted from several cells
traps bicarbonate--> maintains neutral pH and contributes to physical barrier |
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Stomach Intrinsic Factor
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Vitamin B-12 glycoprotein, essential for absorption of B-12
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Stomach Mucus Neck Cells
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neck region of gastric gland, has parietal cells dispersed around
secrete soluble mucus upon stimulation by the VAGUS does NOT secrete while resting |
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Stomach Chief Cells
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basophilic, found in basal 1/3 of mucosa
secrete Pepsinogen and Weak Lipase contain secretory granules called zymogen |
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Stomach Parietal
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secrete HCL and Intrinsic Factor
found in neck of gastric glands large, traingular shape and acidophilic |
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Activation of HCL Secretion
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Gastrin: stimulates gastric acid secretion, release of gastrin inhibited by H+ in stomach (negative feedback)
Histamine H2 Acetylcholine M3 |
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Steps of HCL Production
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H2O (H + OH), CO2 enter cell
CO2 + 2OH --> H2CO3 H2CO3 --> H + HCO3 H+ ions transported by H+/K+ ATPase into lumen K+ and Cl- transported into lumen by uniporters Formation of HCL by H+ and Cl- in lumen |
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Stomach Enteroendocrine Cells
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Basal Secretion
Sample contents of gland lumen and release hormones based on findings clear cytoplasm, near chief and parietal stained Salts, Silver, and Chromium |
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Cardiac Glands of Stomach
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found in cardiac stomach
secrete Mucus (protects against gastric reflux) have short ducts w/ elongated nuclei b/t secretory portion of gland and shallow pits which glands secrete (site of cell renewal) |
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Pyloric Glands of Stomach
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found in Pyloric Antrum (b/t fundus and pylorus)
branched, coiled glands w/ wide lumen secretory cells similar to surface mucus cells, produce viscous secretion parietal and enteroendocrine cells pits 1/2 of mucosa thickness |
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Muscularis Mucosae of Stomach
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2 thin layers (inner circular and outer longitudinal)
3rd circular layer present sometimes |
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Submucosa of Stomach
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Dense irregular CT and adipose
blood vessels Meissner's Plexus-innervates vessels and SM in mucosa |
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Muscularis Externa of Stomach
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3 layers: inner oblique
Middle Circular Outer Longitudinal Function: mixing of chyme and movement into SI Myenteric (Auerbach's) plexus- b/t muscle layers, innervate SM |
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Serosa of Stomach
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Mesothelium and underlying CT
continuous w/ Parietal Peritoneum of abdominal cavity |
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SI General Features
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Longest component of GI
3 regions: Duodenum: first, shortest and widest part Jejunum: 2nd, constitutes upper 2/5 Ileum: continuation jejunum, lower 3/5 |
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SI Function
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principle site for digestion and absorption
delivery site for Pancreatic Enzymes and Bile Enterocytes- intestinal absorptive cells site of water and electrolyte reabsorption |
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SI Enterocytes
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apically located, contain MV
enzymes localized to glycocalyx-complete breakdown of sugars and proteins to monosaccharides and amino acids |
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Plicae Circulares of SI
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circular folds that increase absorptive surface
core of Submucosa |
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Villi of SI
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finger/leaflike projections of mucosa
completely cover surface of SI increase Surface Area of SI Lacteal: blind ending lympathic capillary found only in SI |
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MV of SI
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surface of enterocytes
increase SA |
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Mucosa of SI
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5 cell types: enterocytes-absorption
Goblet cells: mucus secretion Paneth cells: antimicrobial secretion Enteroendocrine cells: paracrine/endocrine hormones M (microfold) cells: cover lymphatic nodules |
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Glands of SI
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"crypts of Lieberkuhn"
stem cells located at base of gland -upward migration gives Enterocytes and Goblet cells -Enteroendocrine cells divide and migrate w/ goblet cells but slower -Paneth cells dont migrate, DONT DIVIDE, remain near base |
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Enterocytes of SI
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columnar, basally located nucleus
Supranuclear golgi Tight jxns b/t: active transport to move water, electrolytes ect. lateral Plications separate during active absorptions, enlarging intercellular space Secrete glycoprotein enzymes absorption of fluid by villus enterocyte balanced by secretion of fluid by gland enterocytre |
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Goblet Cells of SI
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produce Mucus
increase in number as travel along GI EM&LM: mucinogen granules in apical region, pushes sides outwards -cup shaped golgi at base of granules |
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Paneth Cells of SI
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found at base of intestinal glands
LM&EM: eosinophilic, refractile apical Secretory Granules Granules (secretions): Lysozyme-antibacterial, digests cell walls -a-defensins -Glycoproteins role in regulating normal bacterial flora (defense cells) |
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Enteroendocrine Cells of SI
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Secretions: CCK
Secretin Glucose-dependent insulinotropic peptide (GIP) Motilin Somatostatin Histamine |
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CCK
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increase pancreatic and gallbladder activity and HCO3 secretion by pancreas
inhibits gastric secretory function |
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Secretin
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same as CCK
inhibits H+ secretion by parietal cells |
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GIP (Glucose-dependent insulinotropic peptide)
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stimulates insulin release in pancreas
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Motilin
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initiates gastric and intestinal motility
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Somatostatin
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Paracrine hormone (local affect)
response to H+ inhibits gastrin release, gastric acid secretion and other GI hormones |
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Histamine
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Paracrine hormone
stimulates gastric acid secretion |
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Vasoactive intestinal peptide (VIP) (neurocrine hormone)
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stimulates pancreatic enzyme secretion (HCO3)
inhibits SM and sphincter contraction inhibits H+ secretions |
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Bombesin (neurocrine hormone)
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stimulates gastrin release
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Enkephalins (neurocrine hormone)
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stimulates SM contraction
inhibits intestinal secretion |
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M (microfold) Cells of SI
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Epithelial cells over Peyer's Patches and other lymphatic nodules
contain apical microfolds instead of MV Antigen-Transporting Cell |
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Submucosa of SI
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distinguishing feature of deodenum- Brunner's Glands
-secrete HCO3 |
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Muscularis Externa of SI
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2 kinds of contraction:
Segmentation- circulates chyme and mixes digestive juices Peristalsis: contraction of both muscle layers, moves contents distally |
