Esophagus-Stomach Microanatomy Notes 2024-25 PDF

Microanatomy of the Esophagus and Stomach Rod D. Braun Page 1 of 30 MICROANATOMY OF THE ESOPHAGUS AND STOMACH Lecture Learning Objectives: 1. Describe the histological layers (and sublayers) of th...

Microanatomy of the Esophagus and Stomach Rod D. Braun Page 1 of 30 MICROANATOMY OF THE ESOPHAGUS AND STOMACH Lecture Learning Objectives: 1. Describe the histological layers (and sublayers) of the alimentary canal of the digestive system (gastrointestinal or GI system), including their usual contents. Describe the contents and functions of the enteric nervous system. 2. Describe the microanatomy and functions of the esophagus. Describe the histological layers of the esophagus. Describe the transitional change that occurs in the muscularis externa of the esophagus. 3. Describe the microanatomy and functions of the stomach. Describe the histological organization of the transition region between the esophagus and stomach. Describe the 3 gross regions of the stomach as distinguished by histology. Describe the characteristic features of the mucosa of the stomach. Describe the layers of the stomach mucosa, including the features of the epithelium and gastric pits. Compare and contrast the organization of the muscularis externa of the stomach with that from most other parts of the gastrointestinal tract. 4. Describe the mucosal glands of the stomach. Describe the gastric (fundic) glands of the stomach. Describe the cell types found in the gastric (fundic) glands and the location of these cells. Describe the exocrine products secreted by cells in the gastric glands. Describe the endocrine products secreted by cells in the gastric glands and the mechanisms of secretion. Distinguish among the secretory cell types in gastric glands at the LM (H&E) and EM levels. Describe the features of enteroendocrine cells. List common types of enteroendocrine cells found along the alimentary canal. Describe the function of gastrin released by G cells. Describe the cardiac glands of the stomach. Describe the pyloric glands of the stomach. Compare and contrast the three types of mucosal glands in the stomach. Distinguish among the three types of stomach mucosal glands histologically. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 2 of 30 Lecture Content Outline I. Alimentary canal of digestive system A. Components B. Layers C. Enteric nervous system II. Esophagus A. Function of esophagus B. Layers of esophagus III. Stomach A. Function B. Esophagogastric (gastroesophageal) junction C. Histological regions D. Characteristics of mucosa E. Layers of wall IV. Mucosal glands of stomach A. Types B. Gastric glands: cell types 1. Mucous neck cells 2. Parietal cells 3. Chief cells 4. Enteroendocrine cells 5. Undifferentiated stem cells C. Cardiac glands D. Pyloric glands E. Distinguishing characteristics of 3 types of mucosal glands Microanatomy of the Esophagus and Stomach Rod D. Braun Page 3 of 30 MICROANATOMY OF ESOPHAGUS AND STOMACH I. GASTROINTESTINAL (GI, DIGESTIVE) SYSTEM A. COMPONENTS 1. Alimentary canal: Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, and anal canal 2. Principal organs associated with alimentary canal: tongue, teeth, salivary glands, pancreas, liver, and gallbladder B. LAYERS: the wall of the digestive tract from the esophagus to the anal canal is made up of four layers (Figures 1 and 2; Table at end of notes). From the lumen outward, they are: 1. Mucosa a. Epithelium i. Epithelium may serve as a protective, secretory, or absorptive layer. ii. Epithelium is either stratified squamous nonkeratinized or simple columnar. b. Lamina propria i. Loose connective tissue with many capillaries. ii. Frequently contains diffuse or nodular lymphatic tissue referred to as gut- associated lymphatic tissue (GALT). iii. May contain glands continuous with epithelium (mucosal glands). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 4 of 30 Figure 1. Diagram of digestive tract, showing relationships among organs and the differences in the layers of the wall. Figure th 17.1 from Histology: A Text and Atlas (Ross & Pawlina, 6 ed., 2011). Figure 2. Layers of the digestive tract wall. Modified from Human Histology: A Microfiche Atlas, Erlandsen & Magney (1985). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 5 of 30 c. Muscularis mucosae i. Thin layer of smooth muscle ii. Depending on location, it contains inner circular and outer longitudinal components. iii. Contractile properties cause a change in the surface area for secretion and absorption. 2. Submucosa a. Coarse, collagenous connective tissue (dense irregular connective tissue) with blood vessels, lymphatic vessels, and nerves. b. Contains ganglion cells of submucosal (Meissner's) plexus. c. Contains glands in esophagus and duodenum only. 3. Muscularis externa (muscularis propria) a. Usually two muscle layers: inner circular and outer longitudinal a. Circular: Contraction leads to constriction of a ring of smooth muscle and a decrease in diameter of that segment of the GI tract. b. Longitudinal: Contraction leads to a decrease in length as well as increase in diameter of that segment of the GI tract. b. In stomach: 3 layers (inner oblique layer added). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 6 of 30 c. Throughout most of the tract, the muscularis externa is composed of smooth muscle. At the beginning of the esophagus and the end of the anal canal, there is skeletal muscle present. d. Ganglia of myenteric (Auerbach's) plexus are found between the layers. i. This plexus and the submucosal plexus (see above) belong to the intrinsic enteric component of the autonomic nervous system (see Section I.C). ii. These integrated networks regulate peristaltic muscular contractions and secretory functions of mucosal and submucosal glands. 4. Serosa or Adventitia (Fibrosa): outermost layer is either a serosa or an adventitia (fibrosa) a. Serosa i. If the organ is an intraperitoneal organ (see Dr. Goebel’s “Peritoneal Cavity” lecture), it will be covered by a serosa. ii. Outer layer of connective tissue covered by a simple squamous epithelium called mesothelium. iii. Also called the visceral peritoneum. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 7 of 30 b. Adventitia (Fibrosa) i. If the organ is a retroperitoneal organ (see Dr. Goebel’s “Peritoneal Cavity” lecture), it will be covered by an adventitia (fibrosa). ii. Outer layer of connective tissue that blends in with surrounding tissues; there is no mesothelial covering. Figure 3. Neural control of the gut wall. Black fibers: myenteric and submucosal plexuses; Red fibers: sympathetic and parasympathetic nervous systems that exert extrinsic control of the plexuses; Green fibers: sensory fibers passing from the luminal epithelium and gut wall to the enteric plexuses, then to the spinal cord or brain stem. Modified from Figure 63-4 from Guyton and Hall Textbook of Medical Physiology (Hall, 13th ed., 2016). C. ENTERIC NERVOUS SYSTEM (Figure 3) 1. Situated within the walls of the GI tract, extending from the esophagus to the anus. 2. Consists of two neural plexuses: a. Submucosal plexus (Meissner’s plexus): primarily involved in the control of secretion and blood flow. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 8 of 30 b. Myenteric plexus (Auerbach’s plexus): primarily involved in the control of the motility of the GI smooth muscle. 3. Major role in integration and coordination of the motility, secretory, and endocrine functions of the GI tract. a. Coordinates and relays information from the parasympathetic and sympathetic nervous systems to the GI tract. b. Uses local reflexes to relay information within the GI tract. c. Controls most function of the GI tract, especially motility and secretion, even in the absence of extrinsic innervation. 4. The enteric nervous system receives sensory information from chemoreceptors and mechanoreceptors in the GI tract. II. ESOPHAGUS A. FUNCTION OF ESOPHAGUS: Muscular tube that delivers food and liquid from pharynx to stomach. B. LAYERS OF ESOPHAGUS (Figure 4) 1. Mucosa a. Epithelium: stratified squamous non-keratinized epithelium (Figure 5). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 9 of 30 th Figure 4. Cross-section through esophagus, showing layers. Figure 17.2 from Histology: A Text and Atlas (Ross & Pawlina, 7 ed., 2016). Figure 6. Mucosal or cardiac glands (b) in lamina propria of esophagus. a: epithelium, c: muscularis mucosae, d: submucosa, e: inner layer of muscularis externa, f: lymphatic nodule. From A Visual Approach to Histology, Wismar & Ackerman (1970). Figure 5. Mucosa of esophagus; epithelium with underlying lamina propria and muscularis mucosae. Figure 17.3 from th Histology: A Text and Atlas (Ross & Pawlina, 7 ed., 2016). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 10 of 30 b. Lamina propria i. Loose connective tissue underlying epithelium. ii. Mucosal or cardiac glands may be present near ends of esophagus (Figure 6). They are simple branched tubular glands similar to those in the upper or cardiac region of the stomach (see Section IVC). c. Muscularis mucosae: a well-developed single layer of longitudinally oriented smooth muscle (Figures 5 and 7). Figure 7. Wall of esophagus, showing inner and outer layers of muscularis externa at right. Lumen at left. Note distinct muscularis mucosae, and underlying submucosa with 2. Submucosa (Figures 7 and 8) esophageal glands. From Human Histology: A Microfiche Atlas, Erlandsen & Magney (1985). a. Coarse, collagenous connective tissue (dense irregular connective tissue). b. Submucosal glands (esophageal glands proper) i. Compound tubuloalveolar glands with variable Figure 8. Submucosal glands or esophageal glands proper in submucosa of esophagus. Excretory duct is also shown. Lumen and mucosa are at top. Figure 17.4 from Histology: distribution. th A Text and Atlas (Ross & Pawlina, 7 ed., 2016). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 11 of 30 ii. Mostly mucous cells, but some serous cells producing lysozyme. 3. Muscularis externa (Figure 7) a. Inner circular and outer longitudinal layers. b. Transition from skeletal muscle (upper third) to smooth muscle (lower third) reflects transition from voluntary to involuntary swallowing. 4. Adventitia (fibrosa): loose connective tissue that blends with adjacent structures. III. STOMACH A. FUNCTION: Expanded muscular portion of digestive tube that mixes and partially digests food, producing a pulpy fluid mix called chyme. B. ESOPHAGOGASTRIC (GASTROESOPHAGEAL) JUNCTION 1. Junction of esophagus and initial region of stomach Figure 9. Longitudinal section through cardia of stomach (right), (cardiac stomach). showing junction with the esophagus (left). Note gastric pits in cardia. From Histology by Sobotta and Hammersen (1980). 2. An abrupt change in the epithelial lining occurs at the esophagogastric junction. 3. Epithelium changes from stratified squamous nonkeratinized to simple columnar (Figure 9). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 12 of 30 Figure 10. Histological regions of the stomach. Lower right: Cellular details of gastric glands found in fundic stomach (fundus and body). Modified from Human Histology: A Microfiche Atlas, Erlandsen & Magney (1985). C. HISTOLOGICAL REGIONS: The stomach has three separate histological regions, distinguished by the nature of their mucosal glands (Figure 10): 1. Cardia (near the esophagus), which has cardiac glands: cardiac stomach 2. Body and fundus, which have gastric (fundic, oxyntic) glands: fundic stomach 3. Pylorus (near the duodenal opening), which has pyloric glands: pyloric stomach a. Pyloric antrum: transition from body to pyloric canal. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 13 of 30 b. Pyloric canal: Terminal part of stomach that ends as the pyloric sphincter. D. CHARACTERISTICS OF MUCOSA 1. Rugae a. Temporary longitudinal submucosal folds (rugae) are present (Figure 11). b. Accommodate expansion and filling of the stomach. c. Note: Since the submucosa folds, the Figure 11. SEM of stomach wall showing temporary overlying mucosa submucosal folds or rugae (Ru) and layers of the wall. Smaller raised, undulating regions are mammilated areas. temporarily folds as well. Mu: mucosa, MM: muscularis mucosae, Su: submucosa, ML: muscularis externa, Se: serosa. From Tissues and Organs, Kessel and Kardon (1979). 2. Mammillated or gastric areas a. Mucosa has small, bulging mammillated or gastric areas that represent regions with thickened mucosa (Figure 11). b. They provide increased surface area for secretion. 3. Gastric pits a. Mucosa characterized by indentations (holes) formed by openings of gastric pits (Figures 11 and 12). b. Mucosal glands empty into the gastric pits. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 14 of 30 E. LAYERS OF WALL (Figures 11 and 13) 1. Mucosa a. Surface epithelium: simple columnar epithelium i. The Figure 12. SEM of stomach surface showing apical surfaces of surface mucous cells (foveolar cells) in epithelium and gastric pits. surface and gastric pits are lined with surface mucous (foveolar) cells (Figures 12 and 14), which produce a thick, cloudy mucus. ii. Thick mucous Figure 13. Low magnification LM of wall of body of film has a high stomach, showing 4 layers, with lumen at top. Note two- tone staining appearance in lamina propria due to bicarbonate presence of gastric glands. From Meyer (1970). content and protects the epithelium from the acidity of the gastric contents. b. Lamina propria: loose connective tissue crowded with mucosal glands (see Section IV). i. Glands empty into gastric pits, lined by surface mucous (foveolar) cells (Figures 12 and 13). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 15 of 30 ii. Between the glands is loose connective tissue, containing blood vessels, lymphocytes, plasma cells, eosinophils, mast cells, and macrophages (Figure 15). c. Muscularis mucosae i. Two thin layers of Figure 14. TEM of surface mucous cell (or foveolar cell) in stomach. 1: lumen, 4: mucous granules, 5: junctional complexes. From Histology: A Text and smooth muscle Atlas, Rhodin (1974). (inner circular and outer longitudinal) deep to mucosal glands (Figure 13). ii. Smooth muscle cells extend up between the glands (Figure 15). iii. Contraction of the Figure 15. Gastric glands in lamina propria of body of smooth muscle stomach. Note smooth muscle cells from muscularis mucosae between the glands. From Human Histology: A aids in emptying Microfiche Atlas, Erlandsen & Magney (1985). the glands. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 16 of 30 2. Submucosa (Figures 11 and 13) a. No glands b. Dense irregular connective tissue c. Nerves and ganglion cells of submucosal (Meissner's) plexus. 3. Muscularis externa (Figures 11 and 13) a. Three layers of smooth muscle: inner oblique, middle circular, outer longitudinal. b. Contractions churn and homogenize food as gastric secretions are added. c. Myenteric Figure 16. Ganglion cells in myenteric (Auerbach’s) plexus (center) between layers of muscularis externa of fundic stomach. From (Auerbach’s) virtual slide OkSt053 (20x). plexus is found between circular and longitudinal layers (Figure 16). 4. Serosa: a. Since the stomach is an intraperitoneal organ, it is covered by a serosa (visceral peritoneum). b. Loose connective tissue covered with a mesothelium (simple squamous epithelium). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 17 of 30 Figure 17. Mucosal glands of the stomach, showing cell types. Left: Gastric (fundic, oxyntic) glands found in fundus and body of stomach. Right: Cardiac or pyloric glands found in cardia or pylorus of stomach. IV. MUCOSAL GLANDS OF STOMACH A. TYPES (Figures 10 and 17) 1. Cardiac glands (see Section IVC): a. Located in cardiac region. b. Contain primarily mucous cells. 2. Gastric (fundic, oxyntic) glands (see Section IVB) a. Major type of mucosal gland. b. Also called fundic glands or oxyntic glands. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 18 of 30 c. Found in fundic stomach. d. Have a characteristic two-tone staining appearance (Figure 13) due to distribution of multiple cell types (Figure 17, left). e. Produce gastric juice. 3. Pyloric glands (see Section IVD) a. Located in pyloric region. b. Contain primarily mucous cells. B. GASTRIC GLANDS: CELL TYPES As noted above, the gastric (fundic, oxyntic) glands contain different cell types that give the mucosa a two-tone staining appearance in the fundic stomach: upper portion is eosinophilic and lower portion is basophilic (Figures 17 and 18). The cell types are as follows: 1. Mucous neck cells (Figure 17) a. Located in upper part (neck) of glands. b. Different cells than surface mucous (foveolar) Figure 18. LM of mucosa in body of stomach. Note clear surface mucous cells of epithelium cells. and in gastric pits. Also note two-tone staining of gastric glands in lamina propria. From Human Histology: A Microfiche Atlas, Erlandsen & Magney (1985). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 19 of 30 c. Produce a more soluble mucinogen, which results in a mucus that is thinner and less alkaline than the mucus produced by the surface mucous cells. 2. Parietal cells (Figures 17 and 18) a. Large, acidophilic cells primarily located in upper half of the glands (Figures 15, 17, Figure 19. H&E-stained section of body and base portions of 18, and 19). gastric glands. Note predominance of parietal cells (light gray, central nucleus) in body and larger number of basophilic chief cells (darker staining) in base of gland. Note smooth muscle cells between glands. The right half of this b. Contain slide is shown at higher magnification in Figure 15. From Human Histology: A Microfiche Atlas, Erlandsen & Magney intracellular canaliculi (deep plasma membrane invaginations) and abundant mitochondria that give cells their acidophilic appearance (Figure 20). Figure 20. TEM of parietal cell in gastric gland. Go: Golgi, Nu: nucleus, Fc: fibroblast, m: mitochondria, Ly: lysosomes, Ld: lipid droplet, Jc: junctional complex, Cc: chief cell. From Human Histology: A Microfiche c. Produce hydrogen ions Atlas, Erlandsen & Magney (1985). (H+) through the action of carbonic anhydrase, an enzyme that converts carbonic acid (formed from water and CO2) into H+ and bicarbonate ion (HCO3-) (Figure 21). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 20 of 30 d. In active cells (Figure 21), tubulovesicular membranes containing H+, K+- ATPase fuse with the plasma membrane, increasing the intracellular canaliculi. i. H+ and Cl- are released into Figure 21. Schematic of parietal cell showing mechanisms the gland involved in formation of HCl. Figure 17.3 from Histology: A th Text and Atlas (Ross & Pawlina, 6 ed., 2011). lumen. ii. HCO3- and K+ are released concurrently into the underlying lamina propria. e. Inactive cells exhibit an increase in the cytoplasmic tubulovesicular membrane system, as canaliculi are retracted back into the cytoplasm (Figure 22). Figure 22. Schematic of active (left) and inactive (right) parietal cell showing differences in configuration of intracellular canaliculi and amount of tubulovesicular membranes between the two states. Figure 29.3 from Berne and Levy Physiology th (Koeppen & Stanton, 7 ed., 2018). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 21 of 30 f. Parietal cells also produce gastric intrinsic factor (GIF, Figure 23), a glycoprotein which complexes with vitamin B12, a necessary step for the vitamin to be absorbed in the small intestine (see Digestion and Absorption lecture). 3. Chief cells (Figures 17 and 18) a. Basophilic cells located primarily in the lower part (base) of the glands (Figures Figure 23. TEM immunocytochemical location of intrinsic factor (arrows) within vesicles in 15, 17, 18, and 19). parietal cell. From Human Histology: A Microfiche Atlas, Erlandsen & Magney (1985). b. These have the typical appearance of protein secretory cells. They contain secretory granules, a lot of rER (responsible Figure 24. TEM of chief cells showing zymogen granules (Zg), containing pepsinogen. Gland lumen at top. for basophilia), and prominent Golgi complexes (Figure 24). c. They produce pepsinogen granules, which are concentrated apically (Figure 24), since they are released into the gland lumen. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 22 of 30 d. Pepsinogen is activated from the zymogen (inactive) form by the acidic gastric juice to form pepsin, which initiates protein digestion (see Digestion and Absorption lecture). 4. Enteroendocrine cells a. Enteroendocrine cells are typically found singly throughout the gland (Figure 17). b. Exhibit basal granules, polarized for release toward the lamina propria (Figure 25). c. Although dispersed, the Figure 25. Gastrin-producing cell (open type) from total number of cells in pyloric gland. Mg; mucous granule, Glu: gland lumen, Mv: microvilli, Go: Golgi. From Human Histology: A Microfiche Atlas, Erlandsen & Magney (1985). the alimentary canal makes this the largest of the endocrine organs. d. Hormones, released by enteroendocrine cells via merocrine secretion, may act in the following ways (Figure 26): i. Endocrine: Hormone carried through bloodstream to act on a distant target cell. ii. Paracrine: Hormone locally diffuses to act on a neighboring target cell. iii. Autocrine: Hormone binds to and affects the cell that released it. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 23 of 30 iv. Note: Hormones are also synthesized by neurons in the GI tract (neurocrines). The actions of all these hormones Figure 26. Endocrine, paracrine, and autocrine (endocrine, activities of an enteroendocrine cell. Modified from Figure 5.38 in Histology: A Text and Atlas paracrine, and th (Ross & Pawlina, 7 ed., 2016). neurocrine) will be addressed in the Regulation of the Alimentary Canal lecture. e. All enteroendocrine cells rest on the basal lamina, but not all contact the lumen (Figure 27). i. Closed type: Do not contact the lumen. ii. Open type: have access to the lumen. f. Cells may respond to pressure, luminal content, or neuroendocrine stimulation. Figure 27. Closed (left) and open (right) types of enteroendocrine cells. Note that closed cells do not contact the lumen, while open cells have access to the gland lumen. Figures 17.12b and c from Histology: A Text and Atlas (Ross & Pawlina, 7th ed., 2016). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 24 of 30 g. Enteroendocrine cells can be classified by secretory product and granule morphology. More than a dozen different types are found in the GI tract (Table 1). These will be discussed in more detail in the Regulation of the Alimentary Canal lecture. Enteroendocrine Primary Type of Hormone Cell Action Gastrin G cell Endocrine Cholecytsokinin (CCK) I cell Endocrine Secretin S cell Endocrine Glucose-dependent K cell Endocrine insulinotropic peptide (GIP) Motilin M cell Endocrine Ghrelin P/D1 cell Endocrine Somatostatin D (delta) cell Paracrine Table 1. Common hormones produced by enteroendocrine cells. h. Although enteroendocrine cells are present in the mucosa of gastrointestinal tract from the cardiac stomach through the upper anal canal, the distribution of specific enteroendocrine cell types varies along the length of Figure 28. Distribution of different types of enteroendocrine the alimentary cells along the alimentary canal. canal (Figure 28). i. Gastrin cells are the primary type in the stomach. i. They are concentrated in the pyloric region (antrum). Microanatomy of the Esophagus and Stomach Rod D. Braun Page 25 of 30 ii. Main function is to stimulate the production of HCl by parietal cells (Figure 29). iii. The gastrin cells are inhibited by somatostatin (Figure 29), which also inhibits the release of most of the other gastrointestinal hormones. Figure 29. Enteroendocrine hormone control of HCL secretion by parietal cells in the stomach. Modified from Fig 16-10 in Histology and Cell Biology st (Kierszenbaum, 1 ed., 2002). 5. Undifferentiated stem cells a. Located at base of gastric pits and in neck of glands (Figure 17). b. Provide for renewal of the surface epithelium every 3-5 days. c. Cells in the glands are renewed much less frequently (about every 180 days), but from the same stem cell population. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 26 of 30 C. CARDIAC GLANDS 1. Located in cardiac region of stomach (Figures 9 and 10). 2. Contain primarily mucous cells that secrete mucus to help protect esophageal epithelium from gastric reflux (Figures 17 and 30). 3. Also contain enteroendocrine cells, mucous neck cells, and undifferentiated stem cells. 4. Empty into short gastric pits in an Figure 30. LM of wall of cardiac stomach, showing cardiac glands. Modified from overall shallow (thin) mucosa (Figures Michigan Medical Histology. D.K. MacCallum (2000). 9 and 30). D. PYLORIC GLANDS 1. Located in pyloric region (pyloric antrum) of stomach (Figure 10). 2. Empty into long gastric pits (Figure 31). 3. Glands contain primarily mucous cells that secrete: a. Mucus to protect pyloric mucosa Figure 31. H&E LM of mucosa from pyloric b. Lysozyme, an anti-bacterial region of stomach. Note long gastric pits. From Meyer (1970). enzyme Microanatomy of the Esophagus and Stomach Rod D. Braun Page 27 of 30 4. Also contain enteroendocrine cells, mucous neck cells, and undifferentiated stem cells. 5. Gastrin-producing enteroendocrine cells (G cells) are concentrated here and Figure 32. TEM of cells in pyloric gland. 1: nucleus provide feedback to upper of mucous cell, 2: nucleus of gastrin-secreting cell, 3: lumen, 7: secretory granules, 8: mucous granules. region of stomach (Figure 32). From Histology: A Text and Atlas, Rhodin (1974). 6. The lamina propria surrounding the pyloric glands usually contains more lymphatic tissue than seen in the lamina propria of the other stomach regions (Figure 31). E. DISTINGUISHING CHARACTERISTICS OF 3 TYPES OF MUCOSAL GLANDS (Figure 33) 1. Gastric glands (Figure 33, center panel): striped staining appearance of mucosa, not present in cardiac and pyloric glands. 2. Cardiac glands (Figure 33, top panel) a. Compared to gastric glands: mainly mucous cells – no striped staining appearance b. Compared to pyloric glands: shorter gastric pits in a thinner mucosa 3. Pyloric glands (Figure 33, bottom panel) a. Compared to gastric glands: mainly mucous cells – no striped staining appearance Microanatomy of the Esophagus and Stomach Rod D. Braun Page 28 of 30 b. Compared to cardiac glands: much longer gastric pits and overall thicker mucosa. c. Usually has a large amount of lymphatic tissue in lamina propria. Figure 33. LM of mucosa from different stomach regions, showing mucosal glands. Lines indicate levels at which the gastric pits end. Modified from Michigan Medical Histology. D.K. MacCallum (2000). References: Erlandsen, S.L. and Magney, J.E., Human Histology: A Microfiche Atlas, University of Minnesota Press: Minneapolis, 1985. Gartner, L.P. and Hiatt, J.L., Color Atlas of Histology, 3rd ed., Lippincott Williams & Wilkins: Philadelphia, 2000, Ch. 14. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 29 of 30 Kessel, R.G. and Kardon, R.H., Tissues and Organs: A Text-Atlas of Scanning Electron Microscopy, 1979. Kierszenbaum, A.L., Histology and Cell Biology: An Introduction to Pathology, 1st ed., Mosby: St. Louis, 2002, Ch. 15 and 16. Kierszenbaum, A.L and Tres, L.L. Histology and Cell Biology: An Introduction to Pathology, 5th ed., Elsevier-Saunders, Philadelphia, 2020, Ch. 15. Koeppen, B.M. and Stanton, B.A., Berne and Levy Physiology, 7th ed., Elsevier: Philadelphia, 2018, Ch. 29. MacCallum, D.K., Michigan Medical Histology, University of Michigan, Ann Arbor, 2000. Meyer, D.L., Unpublished histology slide atlas, Department of Anatomy, Wayne State University School of Medicine, Detroit, 1970. Rhodin, J.A.G., Histology: A Text and Atlas, Oxford University Press: New York, 1974, Ch. 28. Ross, M.H. and Pawlina, W., Histology: A Text and Atlas, 6th ed., Lippincott Williams & Wilkins: Philadelphia, 2011, Ch. 17. Ross, M.H. and Pawlina, W., Histology: A Text and Atlas, 7th ed., Lippincott, Williams, & Wilkins, WoltersKluwer Health: Philadelphia, 2016, Ch. 17. (major source) Wismar, B.L. and Ackerman, G.A., A Visual Approach to Histology, F.A. Davis: Philadelphia, 1970. See next page for summary table and diagram. Microanatomy of the Esophagus and Stomach Rod D. Braun Page 30 of 30 Layers in GI Tract Muscularis Fibrosa or Mucosa Submucosa Externa Serosa Portion of GI Muscularis Epithelium Glands Glands Layers Tract Mucosae Deep Mucosal or cardiac esophageal or IC/OL Esophagus SSNK Yes Fibrosa glands near ends esophageal Skeletal → Smooth proper Stomach - Simple columnar Cardiac Glands Yes None IO/MC/OL Serosa Cardia (surface mucous cells) Stomach - Simple columnar Fundic (Gastric, Yes None IO/MC/OL Serosa Fundus (surface mucous cells) Oxyntic) Glands Stomach - Simple columnar Pyloric Glands Yes None IO/MC/OL Serosa Pylorus (surface mucous cells) Small Intestine Simple columnar Intestinal (Crypts of Brunner’s Yes IC/OL Serosa - Duodenum (enterocytes + Goblet) Lieberkűhn) Glands Small Intestine Simple columnar Intestinal (Crypts of Yes None IC/OL Serosa - Jejunum (enterocytes + Goblet) Lieberkűhn) Small Intestine Simple columnar Intestinal (Crypts of Yes None IC/OL Serosa - Ileum (enterocytes + Goblet) Lieberkűhn) Simple columnar Intestinal (Crypts of IC/OL + Taenia Serosa or Large Intestine Yes None (enterocytes + Goblet) Lieberkűhn) Coli Fibrosa Upper Anal Upper: Simple columnar Intestinal (Crypts of IC → IAS (smooth) Yes None Fibrosa Canal (enterocytes + Goblet) Lieberkűhn) OL (stays smooth) IAS (smooth) → Lower Anal Stratified columnar → None Lost (No) None EAS (skeletal) Fibrosa Canal SSNK → SSK OL terminates Key: IC = inner circumferential IAS = internal anal sphincter OL = outer longitudinal EAS = external anal sphincter IO = inner oblique MC = middle circumferential Features of Mucosa in GI Tract (not to scale) RDB: 9/28/2024