HIStology ..Esophagus intestine stom engl


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HIStology ..Esophagus intestine stom engl

  1. 1. DIGESTIVE TRACT Department of Histology, Cytology and Embryology Tatiana Globa State University of Medicine and Pharmacy “Nicolae Testemitanu”
  2. 2. BASIC PLAN OF THE DIGESTIVE TUBE Four functional layers:  Tunica mucosa: This layer is composed of epithelium, connective tissue and muscle. These tissues can usually be found in distinct layers as follows:  lamina epithelialis mucosae: consists only of epithelium  lamina propria mucosae: consists of either loose areolar or reticular connective tissue  lamina muscularis mucosae: consists of smooth muscle  Tunica submucosa: consists of loose connective tissue, nerves, blood vessels, and glands in some organs  Tunica muscularis: consists of at least two layers, an inner circular and an outer longitudinal with parasympathetic ganglia located between the layers  Tunica adventitia or tunica serosa: consists of loose connective tissue.
  3. 3. Esophagus:  The esophagus connects the oral cavity with the stomach allowing and aiding in the movement of food particles to the stomach.  It is a muscular tube having the layers described above for the typical tubular organ.  In the esophagus the layers are specialized for the function of further fragmenting food particles.
  4. 4. Layers of the esophagus  Tunica mucosa: epithelium: consists of stratified squamous epithelium that can be highly folded in an empty organ; lamina propria: consists of loose connective tissue, contains esophageal cardiac glands that are simple branched tubular glands, they produce mucus, mucin, chlorides and some biologically active substances. lamina muscularis mucosae: consists of longitudinally oriented smooth muscle fibers that form 1 layer (can be 2)  Tunica submucosa: consists of loose connective tissue that is very elastic allowing for expansion when food is present; contains esophageal glands proper; they are compound tubuloalveolar glands, which produce mucous.
  5. 5. Layers of the esophagus  Tunica muscularis: consists of smooth and/or skeletal muscle; Proximal end – skeletal muscle cells Middle region – skeletal plus smooth muscle Distal end – smooth muscle cells inner circular layer outer longitudinal layer  Tunica adventitia/serosa: consist of typical loose connective tissue that blends into the connective tissue of surrounding tissues. Serosa: only at distal end that enters peritoneal cavity.
  6. 6. Esophageal wall
  8. 8. Esophageal glands proper (submucosal, tubuloalveolar glands; acidic mucus secretion) Esophageal cardiac glands not shown Present in lower portion; tubular mucosal glands produce mucus with neutral pH
  9. 9. Gastro-Esophageal junction
  10. 10. Comparative characteristic of the wall structure of esophagus and stomach Esophagus Stomach Mucosa Epithelium Stratified squamous nonkeratinized Simple columnar glandular Lamina propria of mucosa Contains esophageal cardiac glands that are simple branched tubular glands. They produce mucus, mucin, chlorides and some biologically active substances. Contains gastric glands that are simple branched tubular. Differ 3 groups of glands: 1. cardiac glands in the cardiac region 2. pyloric glands in the pyloric region 3. fundic or gastric glands in the fundic region. Muscularis mucosae Consists of longitudinally oriented smooth muscle fibers that form 1 layer (can be 2) Consists of 3 layers of smooth muscle: Inner – circular Middle – longitudinal Outer – circular
  11. 11. Submucosa Contains esophageal glands proper. They are compound tubuloalveolar glands, which produce mucous. Glands are absent. Muscularis externa In the upper one-third – is striated muscle. In the middle one-third – is striated and smooth muscle. In the distal third – is smooth as in rest of the digestive tract. It forms 2 layers: inner – circular; outer – longitudinal Present only smooth muscle that forms 3 layers: Inner – obligue; Middle – circular; Outer – longitudinal. Between the muscle layers is present Auerbach’s plexus Superficial tunica In the thoracic cavity is adventitia. After entering the abdominal cavity is serosa. Serosa is present.
  12. 12. STOMACH
  13. 13. STOMACH  Structure - 4 Regions  Cardia  Fundus  Body  Pylorus  Functions:  Continue digestion of carbohydrates started in mouth  Add acidic fluid  Transform food into chyme (mechanical & chemical breakdown)  – Promote initial digestion of proteins (via pepsin) and triglycerides (via lipase)
  14. 14. STOMACH  Cardiac region – surrounds the cardiac orifice  Fundus – dome-shaped region beneath the diaphragm  Body – midportion of the stomach  Pyloric region – made up of the antrum and canal which terminates at the pylorus The pylorus is continuous with the duodenum through the pyloric sphincter
  15. 15. The inner surface of the stomach is irregular. There are: • Rugae – are longitudinally oriented folds • Gastric (mamillated) areas – are bulging irregular areas • Gastric pits – funnel- shaped depressions. Gastric glands empty into the bottom of the gastric pits
  16. 16. GASTRIC PITS
  17. 17. Layers of the TUNICA MUCOSA  Epithelium: consists of simple columnar epithelium that forms branched, tubular glands; organized into gastric pits that open onto the lumen and gastric glands that empty into the base of the gastric pits  Lamina propria: consists of loose areolar connective tissue that in the glandular stomach is minimal between gastric glands and difficult to see in sections; highly vascular containing many blood and lymphatic capillaries  Lamina muscularis mucosae: consists of several layers of smooth muscle oriented both longitudinally and circularly; usually not very thick
  18. 18. STOMACH  Tunica submucosa: typical loose connective tissue contains submucosal plexuses also known as Meissner's plexuses  Tunica muscularis: 3 layers of smooth muscle  Outer longitudinal  Middle circular  Inner oblique  between the muscle layers is located the myenteric or Auerbach's plexus  Tunica serosa: small amount of loose connective tissue with overlying simple squamous epithelium or mesothelium
  19. 19. Epithelium simple columnar glandular of the stomach mucosae Gastric glands simple tubular few branched
  20. 20. Glands of the Stomach Fundus and Body  Mucous neck cells – found dispersed between the parietal cells; secrets a mucus that is thinner than that secreted by the surface mucous cells; mucus protects other glandular cells from action of proteases and HCl.  Parietal cells (oxyntic cells) – found throughout the gastric gland; round cells that contain distinct eosinophilic (pink) cytoplasm and round, prominent nucleus; Secrete HCl and intrinsic factor, needed for absorption of vitamin B12 in the ileum.  Chief cells (zymogenic cells) – found mostly near the base of the gastric glands; very basophilic (purple) containing basally positioned nucleus and prominent basophilic apical cytoplasm filled with many ribosomes; secrete pepsinogen, which is activated to pepsin by HCl in the stomach. Pepsin is an enzyme which is able to break down proteins.  Endocrine cells – difficult to distinguish by conventional light microscopy; Several types are present; some secrete gastrin, glucagon and somatostatin, histamine, endorphins, serotonin, cholecystokinin (CCK) among other hormones.  Undifferentiated cells – located primarily in the neck region; difficult to identify in routine H&E sections; undergo mitosis to form more cells then differentiate into the other cell types present in the gland
  21. 21. Chief cells (basophilic)
  22. 22. Chief cell Pepsinogen on the apical part of the cell
  23. 23. Parietal cells (red color)
  24. 24. Parietal cell Intracellular canalicular system Mitochondria
  25. 25. Endocrine cells Type: G-cells – gastrin – is the principal agent for stimulating the secretion of HCl and pepsinogen D-cells produce somatostatin. They inhibit G-cells EC-cells produce serotonin and substance Р which increase stomach activity. ECL-cells produce histamine which regulate gastric secretion
  26. 26. Cardiac glands Cardiac glands are tubular, occasionally branched glands (similar to the cardiac glands of the esophagus), which contain mainly mucus-producing cells. A few of the secretory cells characteristic for the corpus-fundic glands (chief and parietal cells) may be present.
  27. 27. Pyloric glands Pyloric glands are more coiled than corpus- fundic glands, and they may be more branched. The lumen is relatively wide. A few parietal cells may be present but chief cells are usually absent.
  28. 28. Shallow gastric pits, with simple or branched tubular glands Shallow gastric pits, with branched tubular glands Deep gastric pits, with branched tubular glands
  29. 29. SMALL INTESTINE  Is the longest component of the digestive tract  Is divided into three anatomic segments: duodenum, jejunum, and ileum  Functionally, it is the principal site for the digestion of food & for absorption of the products of digestion  Endocrine Secretion  The bile duct and main pancreatic duct:  Join the duodenum at the hepatopancreatic ampulla  Are controlled by the sphincter of Oddi
  30. 30. SMALL INTESTINE Specializations of intestinal surface  Plicae circulares: deep circular folds of the mucosa and submucosa, most abundant in jejunum  Villi – finger-like projections of the mucosa that extend into the intestinal lumen (epithelium plus lamina propria)  Intestinal crypts (glands of Lieberkühn) – are simple tubular glands between villi  Microvilli – numerous projections of apical plasma membranes of absorptive mucosal cells and give the apical region of the cell a striated appearance, called striated border (brush border)
  31. 31. Plicae circularis
  32. 32. Crypts Villi
  33. 33. Villi • Finger-like projections of mucosa • Contain: - fenestrated capillary network - a central, blind- ending lymphatic capillary (lacteal) - few smooth muscle cells derived from muscularis mucosae - myofibroblasts • Are covered by intestinal epithelium – simple columnar
  34. 34. SMALL INTESTINE Layers of the Small Intestine  Tunica mucosa:  Epithelium - simple columnar  Lamina propria - loose connective tissue rich in blood and lymphatic vessels present in the core of the villi and between crypts  Lamina muscularis mucosae - thin layer of smooth muscle located at the base of the crypts  Tunica submucosa: This layer blends with the lamina propria and is typical. In the duodenum it has coiled branched glands known as Brunner's glands, the ducts of which open into the base of the crypts.  Tunica muscularis: typical consisting of an inner circular layer and an outer longitudinal layer  Tunica serosa: typical
  35. 35. The epithelium of the villus  Enterocytes (absorptive cells)  Goblet cells – unicellular mucin- secreting glands, increase in number from the proximal to the distal small intestine  Enteroendocrine cells resemble those described in the stomach
  36. 36. Epithelium lining the small intestine – simple columnar
  37. 37. The epithelium of the crypt  Enterocytes (absorptive cells)  Goblet cells  Enteroendocrine cells  Paneth cells – are found in the bases of the glands. They have a basophilic basal cytoplasm & large, intensely acidophilic apical secretory granules. These granules contain: the antibacterial enzyme lysozyme (digests the cell walls of certain groups of bacteria), glycoproteins, an arginine-rich protein & zinc. The antibacterial action & the phagocytosis of certain bacteria & protozoa by Paneth cells suggest that they have a role in regulating the normal bacterial flora of the small intestine.  Undifferentiated cells
  38. 38. Goblet cell
  39. 39. Gut-Associated Lymphatic Tissue  Lymphatic nodules  Lymphocytes  Macrophages  Plasma cells  Eosinophils  GALT serves as an immunologic barrier
  40. 40. Regional variations in the small intestine: DUODENUM  presence of Brunner's glands in the submucosa - compound tubuloalveolar branched glands, mixed glands  presence of chyme in the small intestine induces cells of Brunner's glands to secrete alkaline mucus that neutralizes gastric acid and pepsin and further promotes digestion  no plicae circulares
  41. 41. Regional variations in the small intestine: JEJUNUM  no glands in the submucosa  longest villi of all three regions  no lymphoid nodules
  42. 42. Regional variations in the small intestine: ILEUM  permanent aggregated lymphoid nodules in the submucosa  shortest villi  highest number of goblet cells
  43. 43. LARGE INTESTINE  Regions  Cecum – Appendix  Colon  Ascending  Transverse  Descending  Rectum  Anal canal  Functions:  Reabsorption of electrolytes & water  Formation of waste  B vitamins & vitamin K synthesized
  44. 44. LARGE INTESTINE Unlike the small intestine, there are no plicae circulares or villi in the large intestine so the surface of the tunica mucosa is more uniform and flatter than that of the small intestine.  Tunica mucosa:  epithelium - simple columnar epithelium that forms straight tubular glands (crypts)  lamina propria- loose connective tissue that contains numerous blood and lymphatic vessels, collagen, lymphocytes and plasma cells  lamina muscualris mucosae- present beneath the base of the crypts and prominent; undergoes rhythmic contractions  Tunica submucosa: typical, contains Peyer’s patches which are aggregations of solitary follicles or groups of lymph nodules. Each pach contains from 10 to 70 nodules
  45. 45. The epithelium of the crypt  Goblet cells – are more numerous than in the small intestine  Enterocytes (absorptive cells) - few  Enteroendocrine cells  Undifferentiated cells
  46. 46. Colon crypts
  47. 47. LARGE INTESTINE  Tunica muscularis: inner circular and outer longitudinal layers; outer longitudinal layer is organized into three separate bands known as taenia coli; movement of more solid waste to the rectum  Tunica serosa is typical. Commensal bacteria reside in the large intestine and play a role in the continued digestion of food.
  48. 48. Appendix
  49. 49. Colorectal Zone (simple columnar epithelium, crypts) Anal Transition Zone (stratified columnar/cuboidal epithelium) Squamous Zone Pectinate line