Histology                                                                                                                     Stanley Shostak
BioSc 1450                                                                                                                  Spring 05

Lecture 13. Esophagus, Stomach, Intestine and Colon

Bolus reaching stomach through esophagus is reduced to liquid chyme and injected into intestine in small amounts.

microscopic anatomy enteric system (gut):

tunica = layers

Mucosa (tunica mucosa): innermost 3 layers surrounding lumen
epithelium (wet surface epithelia): mucous type of stratified squamous epithelium or simple columnar epithelium
lamina propria: underlying loose ct; glands
muscularis mucosae: thin layer smooth muscle may run up into villi; movement in mucosa Submucosa: regular/irregular (coarse) fibroelastic ct; glands (in some regions); submucosal (Meissner) nervous plexuses (pre- and post-ganglionic parasympathetic fibers; nonmyelinated preganglionic fibers from vagus).

Muscularis externa: two or more muscle layers (inner circular [tight helix; may be modified in sphincters and valves]; outer longitudinal [loose helix]); myenteric (Auberbach) plexuses between muscle layers; peristaltic action independent

Serosa (Adventitia): irregular dense ct surrounded by mesothelium (serosa) or bound to body wall (adventitia)

 Esophagus: from cricoid cartilage through diaphragm to opening of stomach; lumen compressed except when passing bolus from pharynx
Mucosa:
epithelium: stratified squamous mucous (nonkeratinized) type epithelium
lamina propria: cardiac glands (compound, submucosal tubular or tubuloacinar mucus-producing) mainly in lower thirds muscularis mucosae: Submucosa: regular/irregular (coarse) ct;
glands (esophageal glands proper) =  submucosal tubuloalveolar mucous glands; submucosal nerve plexuses
Muscularis externa: skeletal in upper third; mixed with smooth muscle in middle third; smooth in lower third; conspicuously; pharyngoesophageal and esophagastric sphincters

Adventitia: irregular dense ct blends with surrounding ct; becomes serosa after esophagus passes through diaphragm.

esophagastric junction: abrupt trasition of epithelium; cardiac glands of esophagus may extend into cardiac regions of stomach; muscularis externa thickens but no sphincter

 Stomach: [note: external = toward lumen; internal = toward serosa] greater and lesser curvature; flat surface (no villi) punctured by foveolae or gastric pits; four (or three when fundic and corpus are combined usually as body): most easily distinguished by shape of pits (foveolae) and glands, and types of cells in gastric glands; rugae (longitudinal folds) of wall molded by submucosa (i.e., not by lamina propria as in villi) cardiac (ring around entrance of esophagus)
fundus (bulge above),
corpus (= body below fundus),
pyloric (entrance to intestine)

Mucosa (tunica mucosa)

epithelium (wet surface epithelia): simple columnar epithelium; mucous type (mucocytes = epitheliocytes); absorptive: salts, water, glucose, alcohol and some drugs
lamina propria: underlying loose ct; glands; limited diffuse lymphocytes; highly vascularized cardiac: pits wide, deep; gastric glands short and slightly coiled: mainly mucous cells (no chief cells); may produce lysozyme

fundus (sling): pits shallow and narrow; gastric glands bifurcate (2 to 4), narrow, straight, numerous: mainly chief (zymogenic [produces pepsin, rennin, and lipase]) cells in base with some parietal (oxyntic = fried egg) cells

corpus (body) = main gastric region
pyloric: pits wide and deep (compared to pits in cardiac region) coiled; abundant ct between loosely packed glands; gastric glands short, coiled and branched: mucous cells (parietal cell rare; no chief cells), and endocrinocyte; pyloric antrum > pyloric canal > pyloric sphincter
gastric glands pits narrow; bifurcate, narrow, straight: chief (zymogenic) cells in wall and base of + parietal (oxyntic = fried egg) cells; isthmus (immature cells) > neck (neck mucocytes; site of mitotic activity) > base (extends to muscularis mucosae)
glands (extend from mucous epithelia of pits; embedded in lamina propria)
regenerative (= undifferentiated = stem) cells in neck of glands and isthmus (narrow zone)
exocrinocytes
in all regions
mucous cells (mucocytes), mainly in upper third of gastric glands
in gastric glands; some in cardiac glands
parietal (oxyntic = fried egg) cells, produce hydrochloric acid (secretion stimulated by alcohol and caffeine) and intrinsic factor (glycoprotein binds vitamine B12)
only in gastric glands
chief (principal = zymogenic = peptic) in lower portion of glands; cells, secrete pepsinogen, renin, lipase
gastric endocrinocytes or enteroendocrinocytes = diffuse neuroendocrine system; paracrine hormones
APUD cells (secrete gastrin, somatostatin, secretin, cholecystokinin (argyrophils, argentaffins, enterochromaffins)

 muscularis mucosae: thin layer smooth muscle; movement in mucosa


Submucosa: regular/irregular (coarse) fibroelastic ct; submucosal (Meissner) nervous plexuses (pre- and post-ganglionic parasympathetic fibers).

Muscularis externa: 3 poorly defined layers: inner oblique (loops; well developed in cardiac region); middle circular (continuous with layer in esophagus; forms pyloric sphincter); outer longitudinal (developed along curvatures; continuous with layer in esophagus); myenteric (Auerbach) plexus between longitudinal and circular layers.

Serosa: irregular dense ct surrounded by mesothelium; continuous with greater and lesser mesenteries (omenta) at greater and lesser curvatures.

Small Intestine: 3 regions: duodenum, jejunum, and ileum

Mucosa (tunica mucosa): villi (supported by lamina propria) + glands (open into intervillar spaces; embedded in lamina propria) epithelium: wet surface epithelia + goblet (oligomucous) cells (produce mucinogen > mucus) villi: simple columnar; surface absorptive cells with with microvilli forming brush (striated) border and glycocalyx (rich in disaccharidases and dipeptidases); manufacture secretory protein and protein J binding IgA
glands: simple tubular (= crypts of Lieberkühn)
epithelium: simple columnar (resemble surface absorptive cells)
basal exocrinocytes (Paneth) cells (apical eosinophilic granules): probably secrete lysozyme
APUD cells (endocrinocytes; clear cytoplasm; vesicular basal nuclei): Amino Precursor Uptake and Decarboxylation: peptide or amine-secreting cells of gastrointestinal tract and other endocrine organs
lamina propria: underlying loose ct: lacteals take up lipids; capillaries take up amino acids and carbohydrates;
Gut-Associated Lymphoid Tissue (GALT): lymphoid elements (scattered B and T cells, plasma cells, mast cells, macrophages), indivual lymphnodules and aggregated lymnodules in ilium.

 muscularis mucosae: thin layer smooth muscle may run up into villi; movement in mucosa

Submucosa: regular/irregular (coarse) fibroelastic ct; spiral plicae circulares (= folds) especially in jejunum; glands (in duodenum); submucosal (Meissner) nervous plexuses (small parasympathetic ganglia)

Muscularis Externa: two muscle layers (inner circular [tight helix; may be modified in sphincters and valves]; outer longitudinal [loose helix]); (Auberbach) myenteric plexuses between muscle layers; peristaltic action independent

Serosa: irregular dense ct surrounded by mesothelium (serosa) or bound to body wall (adventitia)

  Duodenum absorption of monosaccharides and amino acids via active transport; bile salts emulsify fatty acids and monoglycerides forming micelles which along with glycerol move through sER of surface cells where they are reesterified to triglycerides and coated with protein to form chylomicrons (lipoprotein droplets) that exit cells and are taken up in lacteals (= chyle)

Mucosa (tunica mucosa): villi foliate (leaf-like); glands simple tubular (= crypts of Liberkühn); base of glands reaches muscularis mucosae; glands empty into lumen between villi

epithelium (wet surface epithelia): surface absorptive cells simple column epithelium with brush (striated) border above terminal bars (web); glands (= crypts of Liberkühn): columnar and goblet cells; APUD cells; exocrinocytes (Paneth) cells in base; stem cells (mitotic)

lamina propria: underlying loose ct; GALT

muscularis mucosae: thin layer smooth muscle; inner circular layer runs up into villi; movement in mucosa

 Submucosa: regular/irregular (coarse) fibroelastic ct; duodenal (Brunner's) glands produce mucin and urogastrone (polypeptice that inhibits HCL production in stomach and enhances cell division); submucosal (Meissner) nervous plexuses of parasympathetic nerves and fibers

Muscularis externa: two muscle layers (inner circular, outer longitudinal); (Auberbach) myenteric plexuses between muscle layers; peristaltic action independent

Serosa (Adventitia): irregular dense ct surrounded by mesothelium (serosa facing peritoneal cavity) or bound to body wall (adventitia)

  Jejunum Mucosa (tunica mucosa): villi finger-like; glands simple tubular (= crypts of Liberkühn); base of glands reaches muscularis mucosae; glands empty into lumen between villi; spiral plicae circulares (= folds) prominent
 epithelium (wet surface epithelia): mucous type; more goblet cells than in duodenum; glands (= crypts of Liberkühn): columnar and goblet cells; APUD cells; exocrinocytes (Paneth) cells in base; stem cells (mitotic)

lamina propria: underlying loose ct with numerous plasma cells; glands contain columnar cells; GALT

muscularis mucosae: thin layer smooth muscle may run up into villi; movement in mucosa

 Submucosa: regular/irregular (coarse) fibroelastic ct; glands (in some regions); submucosal (Meissner) nervous plexuses (pre- and post-ganglionic parasympathetic fibers; nonmyelinated preganglionic fibers from vagus).

Muscularis externa: two or more muscle layers (inner circular [tight helix; may be modified in sphincters and valves]; outer longitudinal [loose helix]); (Auberbach) myenteric plexuses of sympathetic neurons and fibers between muscle layers; peristaltic action independent

Serosa (Adventitia): irregular dense ct surrounded by mesothelium (serosa) or bound to body wall (adventitia)

  Ileum Mucosa ( tunica mucosa): numerous villi, short-finger-like; glands simple tubular (= crypts of Liberkühn); base of glands reaches muscularis mucosae; glands empty into lumen between villi epithelium (wet surface epithelia): simple columnar absorptive epithelium + numerous (even more so than in jejunum) goblet cells; glands (= crypts of Liberkühn): columnar and goblet cells; APUD cells; exocrinocytes (Paneth) cells in base; stem cells (mitotic); aggregated lymph nodules covered by simple cuboidal epithelium containing microfold (M) cells and no goblet cells

lamina propria: underlying loose ct; glands; numerous plasma cells; aggregated lymph nodules

muscularis mucosae: thin layer smooth muscle may run up into villi; movement in mucosa

 Submucosa: regular/irregular (coarse) fibroelastic ct; submucosal (Meissner) nervous plexuses (pre- and post-ganglionic parasympathetic fibers; nonmyelinated preganglionic fibers from vagus).

Muscularis externa: two or more muscle layers (inner circular [tight helix]; outer longitudinal [loose helix]); (Auberbach) myenteric plexuses sympathetic neurons and fibers between muscle layers; peristaltic action independent

Serosa (Adventitia): irregular dense ct surrounded by mesothelium (serosa)

 Colon: no pitts or villi; divided into cecum, appendix, ascending, transverse, descending, and sigmoid colons, rectum, and anal canal. Functions in absorption of water, electrolytes, some vitamins, remaining amino acids, lipids, and carbohydrates; compacts feces. Mucosa  (tunica mucosa): epithelium (wet surface epithelia): simple (surface epithelial cell) columnar absorptive epithelium with abundant goblet (oligomucous) cells,

lamina propria: underlying loose ct; glands (= crypts of Lieberkühn)m simple columnar epithelium, regenerative cells, and APUD (enteroendocrinocytes) cells in base release paracrine hormones

muscularis mucosae: thin layer smooth muscle

 Submucosa: regular/irregular (coarse) fibroelastic ct; submucosal (Meissners) nervous plexuses (pre- and post-ganglionic parasympathetic fibers; nonmyelinated preganglionic fibers from vagus).

Muscularis externa:two muscle layers (inner circular [tight helix; modified in anal sphincters]; outer longitudinal [loose helix]) modified as taniae coli: 3 thickening separate haustra coli (Roman device for hauling water; sacculations); (Auberbachs) myenteric plexuses; sympathetic ganglia and fibers between muscle layers; peristaltic action independent;

Serosa (Adventitia): irregular dense ct surrounded by mesothelium (serosa) or bound to body wall (adventitia); appendices epiploicae = small fat-filled pouches

 Appendix: surface epithelium with many goblet cells; glands relatively shallow; lamina propria infiltrated with lymphoid cells; lymph nodules in submucosa

Anorectal junction: abrupt change at anal valves from simple columnar of rectum to stratified squameous epithelium (keratinizing type) of anal canal; rectal glands short; lamina propria infiltrated by lmypohoid cells.

Anal Canal: anal columns = longitudinal folds joined at orifice to form anal valves and anal sinuses. Circumanal glands, hair follicles, and sebaceous glands. Spinincters formed by muscularis externa.

last revised: 02-28-05