== Tongue ==
[[File:HistologicChapter11Tongue-anatomy.jpg|thumb|200px|Tongue Anatomy]]
The tongue is divided anatomically into an anterior 2/3 or body, and a posterior 1/3 or root by a posteriorly oriented V-shaped groove, the sulcus terminalis. A pit, the foramen caecum, is located at the apex of the sulcus terminalis. It represents the embryonic point of origin of the thyroid gland.
== Salivary Glands ==
[[File:HistologicChapter11SalivaryGlands.jpg|thumb|200px|Salivary Glands]]
The salivary glands are divided into two main divisions. The intramural or minor salivary glands (labial, buccal, and palatine) lie within the submucosal connective tissue of the oral cavity. These intrinsic glands secrete continuously to moisten the oral cavity. Three pairs of extrinsic or major salivary glands, the parotid, the submandibular, and the sublingual, lie outside the walls of the oral cavity and must convey their secretions to the mouth by means of excretory ducts which pass through the mucosa. The major glands secrete intermittently in response to specific stimuli. The major salivary glands are classified as compound tubuloalveolar, exocrine glands. The secretory alveoli of the parotid glands are wholly serous, producing a watery secretion; those of the submandibular glands are mixed, although preponderantly serous, and those of the sublingual glands are mixed but preponderantly mucous.
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== Pancreas ==
[[File:HistologicChapter11Pancreas.jpg|thumb|200px|Pancreas]]
The pancreas is both an exocrine and an endocrine gland. The exocrine pancreas is a compound tubuloacinar gland consisting of serous secretory cells arranged in acini. As a gland of external secretion, the serozymogenic products of the acini are conveyed to the lumen of the duodenum by means of a main excretory duct, the main pancreatic duct, and by an accessory pancreatic duct which in some individuals opens into the main duct before reaching the duodenum. The main duct extends the entire length of the gland receiving branches, interlobular ducts, from the individual lobules. Striated ducts are lacking in the pancreas. The only intralobular ducts are long narrow intercalated ducts with a low simple cuboidal epithelium, which open directly into interlobular ducts .
The endocrine pancreas secretes insulin and glucagon directly into the blood stream (capillaries) from irregularly dispersed aggregates of cells forming the pancreatic islets (of Langerhans). The islets are composed of anastomosing cords of cells, numerous capillaries and a fine framework of reticular fibers. They are usually directly surrounded by pancreatic acini, but islets can occur in the interlobular connective tissue. The islets range in size from only a few cells to islets containing thousands of cells. In the latter instance they are large enough to see with the unaided eye. The islets are more numerous in the tail than in any other portion of the pancreas.
== Esophagus ==
[[File:HistologicChapter11DigestiveSystemDiagram.png|thumb|200px|Digestive System Diagram]]
=== Slide 131, Middle Esophagus (H&E) ===
== Stomach ==
[[File:HistologicChapter11Stomach.jpg|thumb|200px|Stomach]]
The gross subdivisions of the stomach are the cardia, the fundus, the corpus (main body) and the pyloric region consisting of a pyloric antrum, a pyloric canal and the pylorus. Only three distinct histological regions are present since the microanatomy of the fundus and corpus is similar. In all regions of the stomach, the surface epithelium consists of tall, columnar mucus-secreting cells. The muscular coat consists of three layers of irregularly arranged smooth muscle.
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== Small Imtestine Intestine ==[[File:HistologicChapter11Intestine.jpg|thumb|200px|Small and Large Intestines]]
The three subdivisions of the small intestine are the duodenum, the jejunum and the ileum. The general microscopic structure is similar in all three parts. In the 21 to 23 feet of small intestine, digestion of food materials continues after leaving the stomach, and its selective absorption occurs.
The serosa is typical, being a layer of mesothelial cells covering a thin loose connective tissue layer.
== Pylorus-Duodenal Junction ==
== Duodenum ==
On slide === Slide 140, Duodenum (PASH):=== Observe the plicae circulares at lowest power.
1. Observe Examine the plicae circulares at lowest powerslide to note the numerous villi and occasional solitary lymphatic nodules.
2With high power, study the epithelium of the villi. Examine Observe the slide to note PAS-positive goblet cells and the numerous columnar intestinal absorptive cells with their striated border. The glycoproteins and mucopolysaccharides of the glycocalyx (surface coat) associated with the microvilli (striated border) accounts for the PAS-positive nature of the striated border. The villi and occasional solitary lymphatic nodulescontain a connective tissue core, the lamina propria, as described previously.
3. With high power, study The intestinal glands (= crypts of Lieberkuhn) open between the epithelium bases of the villi. Observe The glands extend to the PAS-positive muscularis mucosae. Only a few goblet cells and are present in the columnar intestinal absorptive cells with their striated border. The glycoproteins and mucopolysaccharides lower region of the glycocalyx (surface coat) associated with the microvilli (striated border) accounts for the PAS-positive nature glands. Cells of the striated borderPaneth are not easily identified; their secretion has been liberated and few or no granules remain. The villi contain a connective tissue core, the lamina propria, as described previously(See slide 139 below.)
4. The intestinal Beneath the muscularis mucosae the submucosa contains the mucus-secreting, highly branched tubular duodenal glands (= crypts Brunner’s glands, = submucosal glands of Lieberkuhnthe duodenum) open between . The cells of these glands are PAS-positive but the mucin stains less intensely than does the bases mucin of the villigoblet cells. The ducts of these glands extend to empty into crypts of Lieberkuhn after they penetrate the muscularis mucosae. Only a few goblet cells are present in the lower region of the glands. Cells of Paneth are not easily identified; their secretion has been liberated and few or no granules remain. (See slide 139 below.)
5. Beneath the muscularis mucosae the submucosa contains the mucus<peir-secreting, highly branched tubular duodenal glands (= Brunner’s glands, = submucosal glands of the duodenum). The cells of these glands are PASvm>UAB-positive but the mucin stains less intensely than does the mucin of the goblet cells. The ducts of these glands empty into crypts of Lieberkuhn after they penetrate the muscularis mucosae.Histology-00140</peir-vm>
Study slide === Slide 139, Duodenum (H&E). (The mucosa is disrupted from post-mortem changes, villi may not be present.)===
1(The mucosa is disrupted from post-mortem changes, villi may not be present. ) Observe in favorable areas the straight tubular crypts with the large pyramidal or columnar cells of Paneth at their blind ends. Paneth cells are easily identified by the large acidophilic granules in the apical regions of the cells. The round or oval nucleus is located at the base of the cell.
2. By diligent searching, find an enteroendocrine cell (argentaffin cell) with the orange-staining granules located in an infra-nuclear position, i.e., between the nucleus and the base of the cell. These cells are smaller than Paneth cells and their granules are less coarse. A variety of enzymes are secreted into capillaries by such cells.
3. This slide is excellent for studying duodenal (Brunner’s) glands. Note especially how the ducts open into the crypts.
4. In the connective tissue between the two muscle layers of the muscularis externa find ganglion cells which belong to the myenteric plexus.
JEJUNUM.<peir-vm>UAB-Histology-00139</peir-vm>
1. The jejunum lacks the submucosal glands of Brunner.== Jejunum ==
2. On slide 142, Jejunum (PASH) identify with medium power The jejunum lacks the villi on the plicae circulares, the villi located in between the plicae circulares, the lamina propria, the intestinal submucosal glands (crypts of Lieberkuhn), the submucosa and the muscularis externaBrunner.
3. The villi of the human jejunum are said to have rounded ends=== Slide 142, but they appear somewhat variable according to the plane of sectioning.Jejunum (PASH) ===
4. Observe the goblet cells Identify with high medium power. The nuclei the villi on the plicae circulares, the villi located in between the plicae circulares, the lamina propria, the intestinal glands (crypts of these cells often stain more darkly than Lieberkuhn), the nuclei of adjacent absorptive cells. They are also usually narrower or more triangular in shape than in submucosa and the absorptive cellsmuscularis externa.
5. In favorable regions one can locate The villi of the PAS-stained basement membrane on which human jejunum are said to have rounded ends, but they appear somewhat variable according to the epithelial cells restplane of sectioning.
6. Identify Observe the striated border and note its reduction or absence on goblet cells at the bases with high power. The nuclei of these cells often stain more darkly than the crypts nuclei of Lieberkuhn. Small apical granules in the gland adjacent absorptive cells may form a somewhat uniform PAS stained border, but do not confuse this with a striated border. The gland cells They are shorter also usually narrower or less columnar more triangular in shape than in the absorptive cells lining the villi.
ILEUMIn favorable regions one can locate the PAS-stained basement membrane on which the epithelial cells rest. Identify the striated border and note its reduction or absence on cells at the bases of the crypts of Lieberkuhn. Small apical granules in the gland cells may form a somewhat uniform PAS stained border, but do not confuse this with a striated border. The gland cells are shorter or less columnar than the cells lining the villi. <peir-vm>UAB-Histology-00142</peir-vm> == Ileum ==
This is the longest part of the small intestine. As in the jejunum, submucosal glands of Brunner are lacking.
Aggregated nodules (Peyer’s patches) form a characteristic feature of the ileum.
1. === Slide 168, Ileum (H&E). === This is probably from a rhesus monkey; its structure is generally similar to human, but it is small enough in diameter so that a complete cross section can be obtained for study. *Observe most of the features described for duodenum and jejunum. Note especially the several plicae circulares with the core of submucosa extending into them and the muscularis mucosae forming the boundary between mucosa and submucosa as usual. *Paneth cells are not conspicuous (will be seen better in slide 172 below). *Aggregated nodules (Peyer’s patches) form a prominent feature of the ileum. These are aggregates of lymphatic nodules, present in the anti- mesenteric wall of the ileum. They originate in the lamina propria, may extend through the muscularis mucosae into the submucosa. If they reach the lumen of the ileum, they are covered by a layer of cells (called M-cells), not villi. <peir-vm>UAB-Histology-00168</peir-vm> === Slide 172, Ileum, human (H&E) === This was removed during surgery and is therefore free of postmortem changes. *Identify all features of the ileum. Note, only a small part of a Peyer’s patch is present. *Study the villi that show typical normal structure. The striated border is prominent. *Note especially the Paneth cells, whose granules stain a brilliant pink. Also, in the lamina propria, observe eosinophils containing reddish granules. *Look for submucosal plexuses (Meissner’s) as well as for myenteric plexuses. <peir-vm>UAB-Histology-00172</peir-vm> == Appendix == As a blind diverticulum of the cecum, the appendix has a small and generally irregular lumen. The appendix often exhibits inflammation accompanied by infiltration of large numbers of neutrophils. A constant feature of the appendix is the vast amount of lymphatic tissue present.
a. Observe most of the features described for duodenum and jejunum. Note especially the several plicae circulares with the core of submucosa extending into them and the muscularis mucosae forming the boundary between mucosa and submucosa as usual.=== Slide 145, Appendix (H&E) ===
b. Paneth cells are not conspicuous Scan slide 145, Appendix (will be seen better in slide 172 belowH&E)to find the 4 layers: mucosa, submucosa, muscularis externa, and serosa. The tissue may show postmortem changes and artifacts of preparation.
cNote that the appendix lacks villi and plica circulares. Aggregated nodules (Peyer’s patches) form a prominent feature The crypts of Lieberkuhn appear similar to the ileum. These are aggregates glands of lymphatic nodulesthe large intestine, present although they may be more variable in the anti- mesenteric wall length and less numerous per given area. The crypts contain absorptive columnar cells, goblet cells, and occasional cells of Paneth and enteroendocrine cells. Find a favorable crypt for study to identify these cell types. The striated border of the ileumsimple columnar surface cell is thin. They originate The enteroendocrine cells are difficult to identify on our preparations but they are perhaps more numerous in the lamina propria, may extend through the muscularis mucosae into appendix (5 to 10 per gland) than in the submucosasmall intestine. If they reach Mitotic figures are easily found in the lumen lower ends of the ileum, they are covered by a layer of cells (called M-cells), not villiglands.
2The lamina propria is completely infiltrated by lymphocytes. Slide 172, Ileum, human (H&E). This was removed during surgery and is therefore free of postmortem changesNote how lymphatic nodules may interrupt the somewhat poorly developed muscularis mucosae.
aOther prominent cells present here are active macrophages. Identify all features The “foamy” granulated or vacuolated cytoplasm of the ileum. Note, only these cells stains a small part darker red than that in other cells of a Peyer’s patch is present.b. Study the villi that show typical normal structurelamina propria. The striated border is prominentsmaller cells with bilobed nuclei and reddish cytoplasm are eosinophils.
c. Note especially the Paneth cells, whose granules stain a brilliant pink. Also, in the lamina propria, observe eosinophils containing reddish granules.<peir-vm>UAB-Histology-00145</peir-vm>
d. Look for submucosal plexuses === Slide 146, Appendix (Meissner’sMasson’s stain) as well as for myenteric plexuses.===
APPENDIXNo special features are present, but note the blue-stained connective tissue, the myenteric plexus with ganglion cells, and the lymphatic nodules. The granules in the cells of Paneth are darkly stained. Observe that the circular layer of smooth muscle is thicker and better developed than the longitudinal layer.
1. As a blind diverticulum of the cecum, the appendix has a small and generally irregular lumen. The appendix often exhibits inflammation accompanied by infiltration of large numbers of neutrophils. A constant feature of the appendix is the vast amount of lymphatic tissue present.<peir-vm>UAB-Histology-00146</peir-vm>
2. Scan slide 145, Appendix (H&E) to find the 4 layers: mucosa, submucosa, muscularis externa, and serosa. The tissue may show postmortem changes and artifacts of preparation.== Colon ==
3. Note that In the appendix lacks villi and plica circulares. The crypts of Lieberkuhn appear similar to colon, the glands 4 layers of the large intestinealimentary tract are present, although they may be more variable in length and less numerous per given area. The crypts contain absorptive columnar cells, goblet cells, and occasional cells but the longitudinal layer of Paneth and enteroendocrine cells. Find a favorable crypt for study the muscularis externa is modified to identify these cell types. The striated border form 3 separate thick longitudinal bands of muscle called the simple columnar surface cell taeniae coli, between which is a thin. The enteroendocrine cells are difficult to identify on our preparations but they are perhaps more numerous in the appendix (5 to 10 per gland) than in the small intestine. Mitotic figures are easily found in the lower ends layer of the glandsmuscle.
4The straight tubular intestinal glands (crypts of Lieberkuhn) are longer and more numerous than in the small intestine, and they contain more numerous mucous goblet cells. Some glands almost appear to consist of goblet cells only. Plicae circulares, villi and Paneth cells are lacking. The lamina propria is completely infiltrated by lymphocytesmucosa of the human colon therefore has a rather smooth surface. Note how lymphatic nodules may interrupt the somewhat poorly developed muscularis mucosaeThe simple columnar epithelial cells still exhibit a thin absorptive striated border.
5. Other prominent cells present here are active macrophages. The “foamy” granulated or vacuolated cytoplasm lamina propria of these cells stains a darker red than that in other cells the colon is similar to the lamina propria of the small intestine. Lymphocytes are abundant with scattered lymphatic nodules either limited to the lamina propriaor extending through the muscularis mucosae into the submucosa. Peyer’s patches are absent. The smaller cells with bilobed nuclei muscularis mucosae presents two layers of smooth muscle, an inner circular layer, and reddish cytoplasm are eosinophilsan outer longitudinal layer.
6. Examine slide 146=== Slide 144 Colon, Appendix (Masson’s stain). No special features are presentPASH, rhesus monkey, but note the bluecomplete cross-stained connective tissuesection, the myenteric plexus with ganglion cells, and the lymphatic nodules. The granules in the cells of Paneth are darkly stained. Observe that the circular layer of smooth muscle is thicker and better developed than the longitudinal layer.COLONshows three taeniae coli) ===
1Scan the slide to see these three taeniae. Mucigen of the goblet cells is very well demonstrated. In Study this slide for the features noted above. Find an area where the glands are cut longitudinally to see that they are straight and extend almost to the muscularis mucosae. Study the surface epithelium to see that in some areas more goblet cells appear in the colon, glands than on the 4 layers of luminal surface between glands. Large blood vessels occur in the alimentary tract submucosa. Temporary folds are present, but . Note that the longitudinal layer surface of the muscularis externa mucosa is modified to form 3 separate thick longitudinal bands of muscle called smooth; the taeniae coli, between which is a thin layer of musclecolon lacks villi.
2. The straight tubular intestinal glands (crypts of Lieberkuhn) are longer and more numerous than in the small intestine, and they contain more numerous mucous goblet cells. Some glands almost appear to consist of goblet cells only. Plicae circulares, villi and Paneth cells are lacking. The mucosa of the human colon therefore has a rather smooth surface. The simple columnar epithelial cells still exhibit a thin absorptive striated border.<peir-vm>UAB-Histology-00144</peir-vm>
3. The lamina propria of the colon is similar to the lamina propria of the small intestine. Lymphocytes are abundant with scattered lymphatic nodules either limited to the lamina propria or extending through the muscularis mucosae into the submucosa. Peyer’s patches are absent. The muscularis mucosae presents two layers of smooth muscle=== Slide 180 Colon, an inner circular layer(H&E, and an outer longitudinal layer.human, surgical specimen) ===
4. Slide 144 180 Colon, (PASHH&E, rhesus monkeyhuman, complete surgical specimen) is part of a cross-section, shows three taeniae spread open. One taenia coli). Scan the slide to see these three taeniae. Mucigen is present at one end of the goblet cells is very well demonstratedsection. Study this slide for the features noted aboveNo postmortem changes are present. Find an area where Again study the glands are cut longitudinally to see that they are straight ; in longitudinal sections, note their openings into the lumen of the colon and extend almost to the muscularis mucosae. Study continuity of their epithelium with the intact surface epithelium to see that in some areas more goblet cells appear in the glands than on the luminal surface between glands. Large blood vessels occur in the submucosa. Temporary folds are present Study other features as above. Note that Serosa (visceral peritoneum) covers the surface of the mucosa is smooth; the colon lacks villisection.
5. <peir-vm>UAB-Histology-00180</peir-vm> === Slide 180 173 Colon, (H&E, human, surgical specimen) is part of a cross-section spread open. One taenia coli is present at one end of the section. No postmortem changes are present. Again study the glands; in longitudinal sections, note their openings into the lumen of the colon and the continuity of their epithelium with the intact surface epithelium. Study other features as above. Serosa (visceral peritoneum) covers the section.=== 6. Slide 173 Colon, (H&E, human), is also a cross-section of the colon spread open. Much of the surface epithelium and outer parts of glands are missing, but aside from this, identify features that are listed above. Look for cell bodies of neurons in the submucosal plexuses (of Meissner). Determine if a band of the taenia coli has been sectioned and is present on your slide.RECTUM<peir-vm>UAB-Histology-00173</peir-vm> == Rectum == === Slide 170, Upper Rectum (H&E) === Scan the slide to observe that the longitudinal layer of the muscularis externa forms a continuous layer. Taenia coli are no longer present. Observe that the structure of the upper rectum is similar to that of the colon except for the taenia coli. Identify the layers of the wall and the structures within each layer as in the colon.
1. Slide 170, Upper Rectum (H&E).<peir-vm>UAB-Histology-00170</peir-vm>
a. Scan the slide to observe that the longitudinal layer of the muscularis externa forms a continuous layer. Taenia coli are no longer present.== Anal Canal ==
b. Observe that the structure of the upper rectum is similar to that of the colon except No slides are available for the taenia coli. Identify the layers study, but you should be aware of the wall and the structures within each layer as some modifications in structure which occur in the colon.lower rectum (upper anal canal)
ANAL CANAL*The outer layer of smooth muscle is replaced by skeletal muscle that serves as the external anal sphincter.
1. No slides are available for study, but you should be aware *The circular layer of some modifications in structure which occur in smooth muscle becomes thickened to form the lower rectum (upper anal canal)involuntary internal sphincter.
a*Longitudinal (vertical) ridges appear which form the rectal columns (columns of Morgagni or anal columns). They usually overlie small veins that contribute to the formation of internal hemorrhoids. The outer layer Anal valves are transverse folds of smooth muscle is replaced by skeletal muscle that serves as the external anal sphinctermucosa which connect the rectal columns at their bases.
b*The intestinal glands (crypts) become shorter and disappear at the level of the anal valves. Here an abrupt transition leads into the lower anal canal. The circular layer of smooth muscle epithelium becomes thickened to form noncornified, stratified squamous. Near the involuntary internal sphincteranal orifice, the epithelium becomes cornified, highly pigmented and it contains hairs, sebaceous glands and sweat glands.
c. Longitudinal (vertical) ridges appear which form the rectal columns (columns of Morgagni or anal columns). They usually overlie small veins that contribute to the formation of internal hemorrhoids. Anal valves are transverse folds of the mucosa which connect the rectal columns at their bases.{{Template:Histologic}}
d. The intestinal glands (crypts) become shorter and disappear at the level of the anal valves. Here an abrupt transition leads into the lower anal canal. The epithelium becomes noncornified, stratified squamous. Near the anal orifice, the epithelium becomes cornified, highly pigmented and it contains hairs, sebaceous glands and sweat glands.[[Category:Histologic]]