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172 Cards in this Set
- Front
- Back
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What are the various functions of the digestive system?
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Ingest foodstuffs & fluids
Digest Absorb nutrients and water Excrete waste products |
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What are the various histological features of the tongue?
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Bundles of skeletal m. in many different orientations
Mixed (serous, mucous) submucosal glands Stratified epithelium Papillae (filiform, fungiform, foliate, circumvallate) |
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What kind of epithelium is present in the oral cavity?
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Cornified stratified squamous epithelium (between food & a hard place, e.g. bone -- hard palate)
Non-cornified stratified squamous epithelium (between food & a soft place -- e.g. buccal cheek) |
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What kind of papillae are present? ?What kind of epithelium? ?Tastebuds?
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Filiform papillae (cornified epithelium). ?NO TASTEBUDS.
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What kind of papillae are present? ?What else is shown?
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Foliate papillae (sides of tongue). ?Ducts, taste glands, etc. Ducts irrigate spaces around papillae to keep path clear for new tastes. ?Can see differently oriented SM near bottom.
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What papilla type is shown? What else is present?
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Circumvallate papilla. ?Serous glands - lipase-containing secretions?flush taste buds & allow continual sampling by taste bud receptors.?
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How are tastebuds structured? ?Where do you find them?
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Associated with all papillae except?filiform (cat's tongue papillae). ?TRC = taste receptor cell. ?Taste pore on exterior surface to the right.
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What taste modalities are mediated by G-protein coupled receptors?
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Umami, sweet, & bitter
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What taste modalities are mediated by ion channel TRCs?
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Sour & salty.
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What is cementum? ?What are peridontal ligaments?
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Bone-like material covering tooth roots (like primary bone).
Anchor point for peridontal ligaments?- highly vascular connective tissue that links the tooth root (via cementum) to the alveolar bone of the tooth socket. |
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What is enamel? ?How is it formed?
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Hardest substance in the body due to high concentration of hydroxyapatite.
Secreted by ameloblasts?(from ectoderm) as many small rods or columns cemented together with additional enamel secretion. ?When tooth erupts through oral epithelium, ameloblasts are lost & no more enamel is made. Also contains enamalin & amelogenin. ?Does NOT contain collagen. |
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What are some distinctive features of the esophagus?
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Muscularis externa transitions from skeletal to SM.
Glands in submucosa/lamina propia. |
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What are some distinctive features of the stomach?
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Epithelial layer -- gastric glands
Muscularis externa layer has extra layer of m. b/c moving food around. Ruggae = folds inside of stomach |
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What different types of glands do you find in different parts of the stomach (cardia; fundus/body; pyloric antrum)?
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Cardia: mucous secreting; simple tubular coiled
Fundus/body: heterogenous cellular content; multiple simple straight tubular branched glands open to a common pit through a narrowed neck. Pyloric antrum: mucous-secreting cells; simple tubular branched glands (central pit/fovea projects deep into lamina propria before branching); enteroendocrine cells secrete gastrin |
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What is the general structure of the gastric glands of the body of the stomach? ?What cells are present/what are their functions?
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1) Surface mucous cells - protective mucous traps bicarbonate, Na+, Cl-, K+ ions to generate local alkaline environment?-- around gastric pit
2) Mucous neck cells, w/ stem cells 3) Parietal cells: pump H+ & Cl- ions --> secrete hydrochloric acid;? secrete?intrinsic factor?- binds vitamin B12 to enhance absorption by intestinal epithelial cells secretory activity regulated by gastrin released in glands of pylorus strongly eosinophilic;? look like little fried eggs; 4) Chief cells/peptic cells: ?basophilic, secrete pepsinogen?- cleaved to liberate pepsin (potent proteolytic enzyme) in acidic environment of gastric fluid |
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What cells are present in this picture? ?What regulates their secretions?
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Chief cells/parietal cells. ?Regulated by gastrin, released by enteroendocrine cells in glands of pyloric antrum of stomach.
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What are distinctive features of the pyloric region of the stomach?
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Thick m. layer w/ oblique layer modification -- forms the pyloric sphincter (separates stomach from duodenum). ?Makes gastin, but we can only see mucous it makes histologically. ?Can also see serosa in pic (as artifact of separation)
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What are the three strategies of the small intestine to increase surface area?
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Plica circulares?- folds of mucosa prominent in distal duodenum & jejunum
Villi?- "fingers" of epithelium Microvilli?- brush border on absorptive cells |
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What is the major connective tissue ECM component of submucosa and lamina propria?
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Hyaluronic acid = hyaluronan (stains green in pic)
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What are the four types of epithelial cells in the small intestine? ?What other features tell you where you are?
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Gastroendocrine/enteroendocrine cells - scattered; produce hormones to regulate activity of a number of dig. system tissues; collectively, largest endocrine organ in the body! DNES?- diffuse neuroendocrine system
Goblet cells - mucous; variable throughout sm intestine Enterocytes/absorbtive cells - most abundant (contain microvilli) Paneth cell - produces lysozyme?- bactericidal/static enzyme Also presence of lymph lacteal |
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What enzymes are associated with microvilli?
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Glycosidases, peptidases, and enzymes that break down lipids.
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How are fatty acids taken up?
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Enzymes associated with microvili break down lipids
Microvili take up fatty acids, tri-glycerides & lipids, and secrete them complexed with a carrier protein.? These chylomicrons?enter the circulation via lymphatic lacteals?in the villi. Smaller triglycerides secreted by enterocytes can enter the blood dirrectly (don't have to go through lymphatic lacteals) |
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How is the epithelium turned over in the gut? ?What is the significance of its high turnover rate?
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Mitosis occurs in stem cells (actually at base of crypt -- pic is incorrect). ?As they divide they push the daughter cells up the villus. ?Eventually sloughed off into lumen of gut. ?
High turnover rate -> reason why gut ends up being an unintented target of chemotherapy. |
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What are the distinctive features of the duodenal region of the sm intestine?
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1) Villi/crypts
2) presence of brunner's glands?in submucosa of glandular tissue -- secrete alkaline bicarbonate to neutralize acidic material from stomach. |
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What is the role of cholecystokinin (CCK)? ?Where is it synthesized & what triggers its release?
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Synthesized by I-cells in the mucosal epithelium of the sm intestine & secreted in the duodenum.
Causes release of digestive/degradative enzymes from the pancreas & bile (detergent axn helps break down fat) from the gallbladder Release triggered by presence of fat/protein ingestion. |
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What is the role of?secretin? ?Where is it synthesized & what triggers its release?
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Produced by S cells of duodenum when luminal pH of duodenum <4.5 (too acidic).
Actions: 1) Stimulates bicarbonate secretion by Brunner's glands & by exocrine portion of pancreas. 2) Reduces acid secretion of parietal cells in stomach. |
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What is the role of?gastrin? ?Where is it synthesized & what triggers its release?
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Produced by "g-cells"?in the pyloric region of the stomach. ?
Stimulates production of acid by parietal cells. |
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What are the distinctive features of the jejunal region of the sm intestine?
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Same basic organization as duodenum (villi, crypts), but no Brunner's glands in submucosa!
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What are the distinctive features of the ilial region of the sm intestine?
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Increase in the amount of diffuse lymphatic tissue from jejunum (but this can be variable). Specialized epithelium (M-cells) overlie diffuse lymphoid tissue in gut. ?Also slightly different shape of villi (won't really go into this distinction).
Villi & crypts like all sm intestine parts. |
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What is the specialization of epithelium overlying diffuse lymphoid tissue in the gut?
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M-cells = microlateral cells.
Found in the follicle-associated epithelium of the?Peyer's patch. They transport organisms and particles from the gut lumen to immune cells across the epithelial barrier, and thus are important in stimulating?mucosal immunity. Unlike their neighbouring cells, they have the unique ability to take up?antigen?from the?lumen?of the?small intestine?via?endocytosis?or?phagocytosis, and then deliver it via?transcytosis?to?dendritic cells?(an?antigen presenting cell) and?lymphocytes?(namely?T cells) located in a unique pocket-like structure on their?basolateral?side. Lack microvilli on apical surface!; far less abundant than enterocytes. ? CXCR4 tropic HIV binds to these to transport across intestinal epithelium! |
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What are the distinctive features of the large intestine?
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Only pits - no villi. ?
Many goblet cells (lubrication) Teniae coli - chords of smoth m.? Myenteric plexi critical for peristalsis (poor/no peristalsis= megacolon). ?Babies don't go home w/o passing stool when first born, b/c is proof that myenteric plexus is intact. ?If not = Hirshprung's disease. ? |
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In what layer of the GI tract do vessels/nerves run?
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Run in submucosa.
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What are the main functions of mucous produced by GI epithelium?
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Lubrication
Protection of wall from acid? Efficient mechanical barrier to bacteria (pic) |
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What are the distinctive features of the appendix?
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Massive amount of lymphoid tissue, often w/ many primary and secondary follicles. ?
May be a sampling bias too (who would take out their nice non-inflammed appendix just to donate it to medical students?) |
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What epithelial transition is made at the anorectal junction?
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Glandular epithelium (lots of crypts/mucous producing cells) inside GI tract --> stratified squamous epithelium outside. ?Becomes cornified and continuous with epidermis once you get to the end of the tube.
Internal anal sphincter (m.) below in pic. |
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What structures are located at a-f? ?What tissue is this?
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Esophagus.
a) epithelium b) muscularis mucosa c) submucosa d) internal (circumfrential) m. e) external (longitudinal) m. f) serosa |
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What tissue component is circled? ?Asterisks? ?What does this information indicate about location in this GI-tract tissue?
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Circled = SM
Asterisks = skeletal m. Presence of both -> middle third of esophagus. |
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The organization & morphology of this epithelium is unique for this tissue. ?What is at A-C & what are their products? ?What regulates the activity of B&C?
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A: Mucous cells (bicarbonate-rich mucous)
B: Parietal cells (HCl, intrinsic factor) C: Chief cells (pepsinogen) Parietal cells & chief cells upregulated by: stomach distention presence of peptides (gastrin) histamine Parietal cells & chief cells down regulated by: Low pH Secretin |
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What regulates the activity of parietal cells & chief cells?
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Parietal cells & chief cells?upregulated?by:
stomach distention presence of peptides (gastrin) histamine Parietal cells & chief cells?down regulated?by: Low pH Secretin |
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What is at A-D? ?What is indicated by the arrows? ?By the asterisks? ?What is this tissue?
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A: villi
B: crypts C: submucosa D: muscularis externa (both layers) arrow: muscularis mucosa asterisks: brunner's glands tissue: duodenum (villi & crypts = small intestine; brunner's glands = duodenum) |
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What is at A-D? ?What is indicatd by the arrow? ?By the asterisks? ?What is this tissue?
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A: villi
B: crypts C: submucosa D: muscularis externa (both layers) arrow: muscularis mucosa asterists: brunner's glands tissue = duodenum |
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What is at A-D? ?What is indicated by black arrows? ?By asterisks? ?By red arrows? ?What is this an image of?
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A: crypts
B: submucosa C: muscularis externa (both layers) D: serosa black arrows: muscularis mucosa asterisks: Payer's patches/diffuse lymphatic tissue red arrows: secondary follicles (antigen-stimulated expansion of B cells) Image = large intestine, possibly appendix |
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Identify structures indicated by a-g
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a: mucosa (epithelium + lamina propria)
b: muscularis mucosa c: submucosa d: internal (circumfrential) m. layer e: external (longitudinal) m. layer f: serosa g: Myenteric (Auerbach) plexus |
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In what layer are Meissner's plexuses (myenteric plexuses) located?
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Submucosal. ?Variable location w/in submucosa - by circular layer or by muscularis mucosae.
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In what layer are Auerbach's plexuses (myenteric plexuses) located?
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In muscularis externa layer, between circumferential & longitudinal layers of m.
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What is indicated at A-G? ?What tissue is this?
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a: mucosa (crypts & villi, no Brunner's glands --> jejunum or ilium).
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What are the major digestive glands?
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Major salivary glands (parotid, submandibular/submaxillary, sublingual)
Exocrine pancreas Liver Gallbladder |
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How are glands characterized?
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simple = single unbranched duct
compound = branching duct system |
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What are the three functions of saliva?
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1) Lubricate mucosa of oral cavity (dissolve food for taste bud fxn, moisten food for swallowing)
2) Digest carbohydrates (amylase) and lipids (lipase) 3) Host defense functions: bacteriocidal proline-rich proteins lysozyme?- targets bacterial cell wall lactoferrin?- limits availability of iron to bacteria IgA?- produced by resident B cells and plasma cells; transported by epithelium into secreted fluid. |
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What are the different locations of salivary glands?
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Isolated glands in the oral cavity
Glands associated with papillae of tongue (eg serous glands of circumvallate papillae) Formal salivary glands (parotid, submandibular/submaxillary, sublingual) |
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What is the gland structure of salivary glands?
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Compound tubuloalveolar glands w/ ducts emptying into the oral cavity.
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What type of product does the parotid gland secrete?
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Serous gland with serous tissue.
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What type of product does the submaxillary/submandibular gland secrete?
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Mixed glands with serous > mucous
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What type of product does the sublingual gland secrete?
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Mixed glands with mucous?> serous tissue.
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What are serous demilunes?
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Mucous cells capped with serous cells
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What is the duct system of salivary glands? ?In what order do different types of ducts appear?
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Glands (mucous serous) -> intercalated ducts (cuboidal epithelium) -> striated ducts (plump epithelium; prominent in parotid, present in submandibular, and not common in sublingual glands) -> interlobar ducts
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What are striated ducts? ?What is their function/where are they found?
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Plump epithelial cells w/ baso-lateral infoldings of cell membrane & many mitochondria.?
Fxn: regulate ion and water content of saliva (extensive ion transport). ?Regulated by hormone aldosterone?- affects composition of secretion. parotid (lots), submandibular (some), sublingual (few) Tend to be eosinophilic (lots of mitochondria). ?May appear to be striated in basal part of cell. |
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What is the function of pancreatic secretions? ?What do they contain?
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Rich in bicarbonate (helps neutralize gastric acid) & digestive enzymes:
amylase (carbs) trypsin, chymotrypsin, carboxypeptidase (protein) lipase, cholesterol esterase, phospholipase (lipids) Enzymes mostly stored in zymogen granules?in pancreatic acinar cells cytoplasma. ? |
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What are zymogen granules/where are they found?
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Found in cytoplasm of pancreatic acinar cells. ?Stores pancreatic pro-enzymes used in digestion of carbs, proteins, & lipids (eg amylase, trypsin, chymotrypsin, lipase, etc.)
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How can you distinguish the exocrine pancrease from the parotid gland in a histological sample?
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pancreas has:
no striated ducts islets = clusters of pancreatic cells epithelium of centroacinar cells?(have smal pale-staining cytoplasm) projects into lumen of acinus |
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How are pancreatic exocrine secretions regulated?
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products of duodenal enteroendocrine cells:
secretin?- targets ductular epithelium to secrete bicarbonate to neutralize acidic gut contents cholecystokinin (CCK)?- calls for lipases to break down lipids ?2) parasympathetic innervation (vagus)?stimulates acinar secretion 3) Insulin synthesized in the endocrine-insular-acinar portal system stimulates amylase?synthesis/secretion. |
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What are the various functions of the liver?
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Organization of the liver reflects intimate association of hepatocytes with blood.
hepatocytes --> both endocrine & exocrine fxn carbohydrate metabolism: gluconeogenesis?(glucose from a non-carb carbon source) & glucogenesis?(interconversion of glycogen & glucose) Lipid metabolism: synthesis of cholesterol and triglycerides Protein synthesis: albumin, coagulation factors, bile, Igf1, thrombopoietin, angiogensinogen Modification of substances: ammonia-> urea, hemoglobin metabolism, chem modification of drugs Vitamin storage: A, D, B12 Exocrine function: components of bile act as detergents to break down ingested lipids Endocrine function: Igf1, thrombopoietin, angiotensin |
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What is a lobule in the liver? ?How is it organized?
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Organizational unit of hepatocytes -- around a central vessel w/ vessels at the edges.
Chords or plates of hepatocytes separated by delicate vascular sinusoids. ?Radial branches of each hepatic artery and portal vein partially surround the lobule & give off tributaries that supply the vascular sinusoid. Sinusoids drain -> central vein Bile drains outwards away from center of lobule. |
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What are hepatocytes (parynchemal cells)?
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Arranged as plates/sheets of cells (cords) running radially out from central vein of lobule.
Well endowed with RER & SER. May be binucleated. Retain proliferative potential! -> can regenerate liver tissue |
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What are hepatic stellate (Ito) cells?
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Store lipids & vitamin A.
Responsible for ECM deposit (scarring) in response to hepatic injury cirrhosis In pic: Ito cells demonstrated by staining for lipids |
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What are oval cells?
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Progenitor cell thought to give rise to both duct epithelium & hepatocytes. ?Contribute to liver regeneration.
Reside in the portal triad area (arrows). |
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What is the classic (anatomic) model of liver lobule organization?
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Central vein and portal triads ring the lobule.
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What is the portal lobule model of liver lobule organization?
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Liver as exocrine gland: lobules organized around a central bile duct that drains ductules or tributaries from 3 adjacent lobules.
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What are Kupfer cells?
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Scattered fixed/resident macrophages studding the venous sinusoids. ?In pic: ingested something dark.
Remove senescent RBCs - share phagocytic blood "filtration" activity with spleen. |
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What is the acinar/Rappaport model of liver lobule organization?
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Based on blood perfusion of lobule. ?Periphery of lobule will experience material absorbed from gut/spleen first (and in highest concentration).
Zone 1: High oxygen tension; high metabolic activity?(protein synthesis & glycogen metabolism) Zone 2: Intermediate region Zone 3: Low oxygen tension: lower metabolic activity. ?Hepatocyte products/metabolites at highest concentration. Explains patterns of hepato-toxicity/glycogen metabolism. |
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What is this a picture of?
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Biliary cirrhosis: cells that will get the most alcohol poisoning will be the cells at the edge: most acutely poisoned.
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What is this a pic of?
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Centrilobar necrosis.
This is what happens when initial substance isn't toxic, but modified form created by hepatocytes is toxic. ?Pathology happens closer to center of lobule. |
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What are some symptoms of liver failure?
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Increased bruising & slower blood clotting times (clotting factors (eg thrombopoin) made by hepatocytes)
Abdominal swelling (not making as much albumin) Jaundice (changes in handling of bilurubin) Pale stool (" ") Dark urine (" ") General fatigue. |
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What is the gall bladder? ?What is its function?
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Receives & stores bile secretion from liver. ?Epithelium concentrates bile 10x-50x by water reomval.
Secretion of gall bladder contents into the duodenum is stimulated by release of CCK by enteroendocrine cells of small intestine. ?Secretion of CCK is stimulated by the presence of dietary fats/lipids in the small intestine. |
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How can you tell when a histological sample is from a gallbladder?
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Simple columnar epithelium w/ microvilli. ?Projections of epithelium are?folds?in the epithelium,?not villi.
Lacks the layered organization of the gut (no submucosa, etc.) Epithelium lacks goblet cells or crypts! |
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What are the two types of gallstones?
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Cholesterol stones?
Pigment stones (bilirubin & Ca2+) |
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Where is bile produced and how does it get to the sm intestine?
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Bile fluid = bile acids, cholesterol, bilirubin, ions
1) Bile produced by hepatocytes 2) Excreted into canaliculi that drain into bile ducts?surrounding the lobule (bile flow is toward periphery of lobule) 3) drains to gall bladder, excreted into gut lumen |
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What is bilirubin? ?Where is it formed?
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A poorly soluble breakdown metabolite of hemoglobulin. ?
Toxic for CNS tissue. 1) Forms complexes with blood albumin in spleen (increases bilirubin solubility). ? 2) Hepatocytes take up albumin-bilirubin complex --> bilirubin glycuronide 3) bilirubin glycuronide enters bile canaliculi and drains to the gall bladder 4) conjugated bilirubin is excreted into gut lumen. 5) most is excreted in feces; a small portion is further metabolized by bacteria & resorbed by gut epithelium |
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What are hepatic sinusoids formed from?
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Fenestrated endothelium w/ scanty basement membrane. ?Light areas in pic on R.
Space between endothelium & hepatocytes = space of Disse |
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What are bile canaliculi (arrows in pics)?
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Formed by basolateral specialization of adjacent hepatocytes (green in pic)
Carry bile material secreted by hepatocytes to bile duccts. |
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What do the red arrows point to?
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Bile canaliculi.
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What do the arrows point to in the picture?
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Bile duct has nice cuboidal epithelium.
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What are the structures at A-D?
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A: Bile duct (notice epithelium)
B: Hepatic artery (SM) C: Portal vein D: Hepatic sinusoids -- mostly hepatocytes & endothelial cells, some Kupfer cells |
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What is indicated by the asterisk? ?The arrow? ?What is the source of material contained by the structure at the arrow?
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Asterisk = central vein of lobule
Arrow = hepatic sinusoid, source: hepatic artery and portal vein |
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What are A-D? ?What tissue?
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A: adipocytes
B: striated ducts C: intercalated ducts D: serous acinar cells Parotid gland |
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What is at A? ?What tissue is this?
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A = ducts
Tissue = sublingual salivary gland |
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Identify A-D. ?What tissue is this?
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A: Adipose
B: serous acini C: mucous acini D: duct Submaxillary/submandibular gland (both mucous and serous acini) |
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Based on the organization of this tissue, what do you think it is and why?
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Liver. ?Repeating lobules, radial organization of tissue, vessels repeating at both center and periphery of lobule.
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What is this tissue and what cells have taken up carbon received intravenously?
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Liver. ?Kupfer cells of hepatic sinusoids ingested carbon.
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What is the direction of blood flow in this region?
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Liver. ?Blood flows toward the center of the liver lobule, toward the central vein.
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What is this tissue?
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Gall bladder. ?Epithelial surface has irregular folds, no crypts, no goblet cells, no villi, and lacks layering characteristic of gut tube --> not lg intestine.
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What is this tissue?
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Jejunum! ?Crypts, villi, layers of gut tube.
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What are the major products of the outlined cells?
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Islets of Langerhans (pancreas). ?
Endocrine - insulin, glucagon, somatostatin. ?Also other minor hormones. |
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What tissue is this? ?How/where are secretions delivered?
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Pancreas.
Exocrine portion delivered via a duct system (large duct upper right) Endocrine portion from islets, delivered via the blood. |
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What is this tissue and what do these cells produce?
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Acini = exocrine.
Lighter staining centro-acinar cells --> pancreatic acini. ? Exocrine part of pancreas (acini) secretes a spectrum of degredative enzymes, eg proteinases, RNAse, etc. |
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Describe the cells & their likely tissue of origin.
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Mostly mucous cells, presence of duct (center bottom) -- sublingual gland.
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Identify cellular elements at A-C. ?What is their likely origin? ?What are two functions of the structures indicated by asterisks?
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A: Mucous-producing acini
B: Serous acini C: Striated ducts; convey products to oral cavity, regulate water content of salivary gland secretion (striations are for ion transport across basement membrane). Submaxillary/submandibular gland (mixed serous & mucous) |
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What do the lightly stained channels represent in this tissue? ?What is separating the channels?
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Light staining channels = hepatic sinusoids
Dark staining separations = cords of hepatocytes |
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What is this? ?What's the tissue?
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Pancreas. ?Islet in lower right corner. ?Arrow is Pacinian corpuscle -- same fxn as skin (coarse touch), different location.
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How can endocrine/exocrine tissues be distinguished?
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Endocrine glands lack ducts b/c they secrete straight into the blood stream. ?Endocrine glands are thus also richly vascular (each cell sits next to a fenestrated capillary or sinusoid).
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In what three ways are endocrine tissues organized?
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Separate organs: thyroid, adrenal, pituitary
Clusters of cells in parenchyma of other organs (pancreatic islets, interstitial cells of testes) Isolated single cells (gut endocrine cells). |
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Where are the secretory products of endocrine organs released?
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Released into interstitial space, then into capillaries. ?Circulate in blood to influence target tissues.
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What are the three types of endocrine secretion?
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Through interstitial space to fenestrated capillaries to target cell (classic)
Via interstitial spaces over short distances (Paracrine) To own cell receptor (autocrine) Through neurons associated with capillaries that carry neural hormones (eg vasopressin & oxytocin) into the blood (neuroendocrine) |
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What are the three classes of hormones?
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Proteins, peptides, glycoproteins (hypothalamus, pituitary; insulin, PTH, etc)
Amino acid derivatives (thyroxine, catecholamines (biogenic amines) Steroids (sex hormones, adrenal cortical hormones - cholesterol base) |
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How are hormones stored intracelluarly?
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proteins/polypeptides/glycoproteins/biogenic amines -- secretion granules
modified amino acids -- bound to protein in an extracellular sac of colloid steroids are released as they are made (not stored, but often do need to be carried by lipophilic proteins in the blood) |
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Where are the different types of hormones synthesized in the cell?
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rER/Golgi: proteins, polypeptides
rER: amino acids sER/mitochondria w/ tubular cristae (distinctive): steroids |
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What is the mechanism of action of protein & peptide hormones?
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membrane receptor
second messanger (eg cAMP) signal transduction (eg kinase cascade) transcription factors (membrane receptor -> intercell signaling) |
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What is the mechanism of action of steroid hormones?
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Diffuse through plasma membrane
Cytoplasmic receptor = nuclear binding protein |
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What is the hypophysis?
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The pituitary gland. ?Major regulator of the endocrine system.
Two lobes of tissue (one CNS neural ectoderm, one epithelial glandular tissue from oral ectoderm) bound together by connective tissue. In sella turcica of sphenoid bone. |
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What is the neurohypophysis?
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The neural portion of the pituitary. ?Downgrowth of CNS neural ectoderm. ?Remains connected to brain by neurohypophyseal stalk in adult.
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What is the adenohypophysis?
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The "anterior lobe" -- epithelial portion of the pituitary. ?Arises as an outpocketing (Rathke's pouch) of oral ectoderm in roof of primitive mouth.
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Describe the embryologic origin of the pituitary.
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Come together during development. ?Downgrowth of diencephalon & upgrowth of oral cavity toward this downgrowth of neural tissue. ?
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How is the neurohypophysis (pars nervosa) structured?
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Really boring histologically. ?Basically just axons and glial support cells (pituicytes). ?Cell bodies all the way up in hypothalamus. ?Long axons make hormone product. ?Product transported down axon to terminal of axon (Herring bodies?- axon terminals where hormones stored)?down in posterior pituitary. ?When neurons stimulated, release hormones into fenestrated capillary bed surrounding axons in pars nervosa.
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What do the arrows point to in the neurohypophysis?
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Axons don't have arrows. ?Glial cells here = pituicytes
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What are Herring bodies? ?Where are they found?
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Neurosecretory bodies found in the posterior pituitary (neurohypophysis/pars nervosa). ?Represent the terminal end of the axons from the hypothalamus; hormones (oxytocin, vasopressin/ADH) are temporarily stored in these locations
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What hormones does the pars nervosa/neurohypophysis produce and what are their functions?
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Oxytocin:
stimulates SM contraction of vessels (BP) stimulates lactation (SM) in reponse to suckling uterine contraction during childbirth relates to emotional state & sexuality Vasopressin/ADH: Stimulates vasoconstriction of arterioles Regulates water resorption in kidney (porins) |
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What is the general arrangement of cells in the adenohypophysis?
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Cells are arranged as plates and clumps of cells surrounded by an extensive capillary network.
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What are the various cell types found in the adenohypophysis?
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acidophils?- stain with acidic dyes?
basophils?- stain with basic dyes chromophobes?- poorly stained; structural cells in colloid |
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How is pituitary function regulated?
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Posterior/neurohypophysis: neuronal control
Anterior/adenohypophysis: by CNS through elaboration of small signaling peptides. ? ? ? ? ?-- neurons in hypothalamus (not?those assoc. with neurohypophysis) have axons ending in the median eminence?(beginning of pituitary). ? ? ? ? -- release small peptides/factors/hormones exerting +/- control on the epithelial cells of the anterior pituitary into the median eminence capillary beds ? ? ? ? -- hormones travel via a portal system to a secondary capillary bed in the adenohypophysis to exert control |
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What hormones are produced by acidophils? ?Fill out the table.
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"GPA" growth hormone, prolactin --> acidophils
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What hormones are produced by basophils? ?Fill out the table.
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"B-FLAT": Basophils --> FSH, LH, ACTH, TSH
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What is the big picture regulation of adenohypophysis function?
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Involves both direct and indirect feedback, from primary or secondary target tissues respectively.
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Where is the thyroid derived from? ?HOw is it organized?
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Derived from outpocketing of oropharyngeal endoderm. ?
Series of very characteristic follicles. ?Squamous epithelium. No ducts. ?Pretty homogenous appearance. |
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What is the structure of thyroid follicles?
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spheres
lined by cuboidal epithelium joined by junctional complexes --> polarized?(basement membrane outside, apicle side toward follicle enter) -->: colloid?fills hollow space = protein (thyroglobulin) secretion. Endocrine tissue --> extensive fenestrated capillary network between follicles |
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How is thyroid hormone production controlled?
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Neuronal release of thyroid releasing hormone (TRH) in response to cold
TRH stimulates production of thyroid stimulating hormone (TSH) by basophils in adenohypophysis (anterior pituitary) TSH fires up thyroid follicle cells to produce T3 & T4 in three ways: ? ? ? ?---stimulates cells to take up iodide from circulation (from basal surface of cells) (pinocytosis) &? ? ? ? ?---to make protinaceous component of thyroglobulin & ? ? ? ---to make thyroid peroxidase T3 & T4 alter metabolic level of multiple tissues to generate heat Elevated levels of T3 in blood is sensed by hypothalamic neurons, as is heat production, leading to reduced release of TRH from neurons |
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What are the various steps of thyroid hormone synthesis?
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Thyroid releasing hormone from basophils in anteior pituitary cause Thyroid stimulating hormone (TSH) to stimulate?iodide uptake and synthesis of thyroid peroxidase & thyroglobulin=colloid
Thyroid peroxidase catalyzes two sequential reactions: (a) iodination of tyrosines on thyroglobulin; (b) synthesis of tyroxine (T4) or triiodothyronine (T3) from two iodotyrosines Thyroid hormones accumulate in colloid, tied up in molecules or thyroglobulin Thyroid hormones are exised from thyroglobulin scaffold by digestion in lysosomes of thyroid epithelial cells;? Free thyroid hormones (T3, T4) diffuse out of lysosomes through basal plasma membrane into blood where they quickly bind to carrier proteins for transport to target cells; recycling of thyroglobulin, MIT, DIT |
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What disease does this picture indicate? ?How is it caused?
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Hypothyroid goiter. ?Lack of dietary iodine --> still high TSH & colloid formation, but no T4 formed --> no feedback inhibition of activity
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What disease does this picture indicate? ?How is it caused?
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Hashimoto's disease. ?Hypothyroidism from thyroiditis (autoimmune disease against thyroid hormone & thyroglobulin). ?
Low T4 but high TSH. ?Small thyroid follicles & follicle/epithelium destruction. ?Lymphocyte infiltration & B-cell follicles formed.? |
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What are the various ways that hypothyroidism is caused? ?What are its symptoms?
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Iodine deficiency
Hashimoto's disease Hypothalamic/pituitary origin (low thyroid release hormone (TRH) or thyroid stimulating hormone (TSH)) Deficient growth, mental slowness/retardation, rough dry skin, coarse scalp hair, sleepy, cold sensitive, low basal metabolism rate (obesity?), muscle weakness |
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What is Grave's disease? ?How is it caused?
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Diffuse thyrotoxic goiter: auto-immune anti-thyroid disease. ?Mimics effects of hormone and makes cell think it's being stimulated by TSH to make more thyroid hormone!
Long-acting thyroid stimulator (LATS) = activate-TSH receptor. ?Stimulates thyroid over long-term. Doesn't really respond to regular signals, since pathway is short-circuited.?Causes hypeRthyroidism. ? Sx: exophthalmus (protrusion of eyes), nervousness, restless, irritable, tremors, high basal metabolism rate & tachycardia (elevated heart rate), muscle weakness, decreased body weight. |
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What are the main causes of hyperthyroidism?
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Grave's disease
Adenoma of thyroid? Adenoma of pituitary In pic: can make out a few follicles in R but cells are so flat out stimulated to make T4 that thyroglobulin doesn't accumulate. ?Follicles pretty much exhausted. |
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What tissue is this? ?Identify A-C. ?What products are produced by each?
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Adenohypophysis/anterior pituitary.
A: acidophil (GH/STH = growth hormone/somatotropic hormone (same thing), PRL=prolactin) B: basophil (FSH, LH, ACTH, TSH, MSH) C: chromophobe (none) |
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What tissue is this? ?Identify A-B. ?What products are secreted here? ?What are the sources of these products?
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Neurohypophysis. ?Secretes oxytocin (paraventricular nucleus) & ADH (supraoptic nucleus).
A: pituicyte B: Hassel's body (end of axon of neurosecretory neuron where products stored/secreted) |
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What tissue is this? ?What are the areas A-C? ?What are their embryologic origins?
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Pituitary gland.
A: neurohypophysis/pars nervosa (neural ectoderm) B: pars intermedia (oral ectoderm) C: pars distalis (oral ectoderm) |
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What are parafollicular/"C" cells? ?Where are they found? Where are they derived from?
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Cells producing calcitonin?(regulates activity of osteoclasts) - lowers levels of calcium in blood & inhibits bone resorption.
? ? ?Works with PTH & Vit D3?derivatives to control plasma calcium levels Found in connective tissue between follicles and in follicle wall (underneath epithelium). Derived from endoderm of 4th pharyngeal pouch? |
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What are the pics of? How is this tissue structured? From where is it derived?
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Parathyroid glands. ?Derived from endoderm of 3rd & 4th pharyngeal pouches
Cords of epithelial cells invested by an extensive fenestrated capillary network. ?Supported by delicate reticular connective tissue framework & a capsule of dense irreg connective tissue. ?Note that has no lymph node structure/layering. |
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What are the two types of epithelial cells found in the parathyroid? ?What are their functions?
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Chief cells - dominant type. ?Produce parathyroid hormone. ?Cuboidal cells, round nuclei, less cytoplasm.?
Oxyphil cells - initially a minor pop that increases in frequency with advancing age. Larger cells w/ same size nucleus as chief cells. ?Many mitochondria. Unknown fxn. |
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Where is parathyroid hormone made/how is it regulated? ?When is it released?
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Released by chief cells in parathyroid. ?
Released in response to?low plasma levels of calcium ions (not the other way around!!!). Stimulates production & activity of osteoclasts, resulting in inc bone resorption & release of ca2+ ions into circulation. ? Stimulates enhanced retention of ca2+ ions by kidney Indirectly enhances ca2+ aborption in the gut (vit D3) Antagonized by the action of calcitonin (from C cells/parafollicular cells) |
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What gland is this? ?What type of hormones does it produce?
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Adrenal/suprarenal. ?Produces steroid hormones.
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Where are the adrenal cortex/medulla derived from?
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Cortex: genital ridge mesoderm
Medulla: neural crest |
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What are the three zones of the adrenal cortex?
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Fascicles - cells lining up (similar to in m. fibers)
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Where is the zona glomerulosa found? ?What is its function and how are its products regulated?
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Most outer layer of cortex of adrenal gland. ?
Secretes mineralocorticoids (aldosterone) which regulates the body's concentration of electrolytes (mostly Na & K) by acting on distal convoluted tubule of kidney nephrons: ?--- ?inc. Na resorption ?--- ?inc. K secretion, water resorption Regulated by kidney & lung. ?Renin-angiotensin system. ?Not v. dependent on ACTH (from adenohypophysis). |
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Where is the zona fasciculata found? ?What is its function and how are its products regulated?
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Middle layer of adrenal cortex. ?
Secretes glucocorticoids (cortisol, corticosterone): ?--- accelerates glucose metabolism, glycogen formation, release & use of amino acids/fatty acids, esp in times of stress; immunosuppresant; influences?adrenalin production Main target of?ACTH?(from ant pituitary/adenohypophysis) -> stimulation; also inc. with stress (which inc. ACTH) |
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Where is the zona reticularis found? ?What is its function and how are its products regulated?
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Adrenal cortex layer closest to medulla.
Secretes weak androgens (DHEA; androstenedione) Slight stimulation by ACTH |
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How are steroid hormones produced by the adrenal gland?
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Lipid based (pic stained for lipids (brown)). ?Using acetate as a starting material, synthesize cholesterol & modify cholesterol enzymatically to generate adrenal steroid hormones.
Prominent sER - cytoplasmic membranous structure containing the enzymes to process & modify cholesterol. do not store steroids - synthesis & secretion on demand. |
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How is adrenal cortex function (synthesis of steroid hormones) regulated?
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Regulated by the hypothalamic/adenohypophysis axis. ?
Hypothalamus releases corticotropin-releasing hormone (CRH) which causes anterior pituitary to release ACTH, which stimulates adrenal cortex to make glucocorticoids. ?Glucocorticoids participate in feedback inhibition of anterior pituitary and hypothalamus. |
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How is the adrenal medulla organized?
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Cords of cells surrounded by an extensive network of fenestrated capillaries that drain into the adrenal vein. ?Medullary cells (which are modified post-ganglionic sympathetic neurons with no axon or dendrite) store catecholamines within granules.
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What is the function of the adrenal medulla? ?How is it regulated?
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Produces catecholamines?(epinephrine & norepinephrin); ~80% of catecholamine output is epinephrine. ?Mimic sympathetic nervous system's "fight or flight" response.
Adrenal medulla cells are modified post-ganglionic sympathetic neurons?with no axon or dendrite. ?From neural crest (duh). Under neural and hormonal control. ?Hormones from part of dual blood supply that is conditioned through travel in cortex to carry catecholamines (products of zona fasciculata) that influence conversion of norepinephrine to epinephrine. |
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What is this picture of?
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A medullary arteriole -- dual blood supply of adrenal medulla --> one part conditioned by hormones in cortex, other part (this pic?) bypasses cortical influence.
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What are the whitish spots in this picture?
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Islets of langerhans in the endocrine pancreas. ?
Notice no ducts in this area because it is endocrine, unlike ducts in acinar area which is exocrine portion of pancreas. |
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What structures are indicated by asterisks? ?What is their embryological origin?
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Islets of Langerhans. ?
Derived from endoderm (along with exocrine portion of pancreas). |
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What is the structure of Islets of Langerhans?
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Roughly spherical. ?Over 1 million per pancreas!
Cords of epithelial cells supported by delicate reticular fibers (blue fibers) which are assoc. with capillaries. Surrounded by serous acini of exocrine pancreas. |
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What four types of cells exist in Islets of Langerhans? ?How are they arranged?
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Alpha cells (produce and store glucagon) = ~20%
Beta cells (produce insulin) = ~70% Delta cells (produce somatostatin which inhibits release of glucagon, insulin, GH, and TSH) = <5% F cells (secrete pancreatic polypeptide (PPP) which blocks secretion of somatostatin & exocrine pancreatic enzymes) = rare Characteristic distribution: Alpha, delta, and Fcells predominate in peripheral regions; Beta cells predominate in core. ? Blood reaching beta cells in the core of the islet carry hormones produced by the others --> regulation of beta cell function. ?Eg somatostatin released by delta cells can inhibit activity of beta cells in the same islet, and then later on (because blood from islets drains into exocrine pancreas) can influence eg creation of amylase. |
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What are alpha cells? ?Where are they found?
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Found in pancreatic endocrine Islets of Langerhans. ?Produce glucagon?(Stimulates conversion of glycogen to glucose in liver)?& store it in cytoplasmic granules. ?Responsible for ~40% of glucagon production (rest made by enteroendocrine cells in gut).
Secreted in response to low blood glucose levels |
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What are beta cells? ?Where are they found?
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Predominant cell (~70%) in pancreatic endocrine Islets of Langerhans.
Produce insulin?(stimulates glucose uptake?by many cell types; conversion of glucose to glycogen in liver; conversion of glucose to triglycerides in adipose cells)?and store it in cytoplasmic granules. |
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How is diabetes mellitus (DM) caused?
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Type I: Juvenile onset; insulent-dependent (IDDM). ?Autoimmune destruction of beta cells.
Type II: Non-insulin dependent (NIDDM). ?Related to insensitive target cells. ? Leads to chronic elevated plasma glucose levels because beta cells not producing insulin --> circulatory problems, tissue ischemia, neuropathies. |
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What is the blood supply to the adrenal medulla?
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Dual blood supply:
Arterial blood entering directly via medullary arteries that do not supply the adrenal cortex Arterial blood that first supplies the adrenal cortex. ?This blood is conditioned by its travel through the cortex - has elevated levels of glucocorticoid?from the zona fasciculata, which determines the relative abundance of norepinephrine (by regulating levels of an enzyme that converts norepinephrine into epinephrine) |
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What tissue is this? ?Identify A-C. ?What products are produced by each?
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Thyroid gland.
A: Follicle cells, produce T3, T4 B: Colloid, produces thyroglobulin C: Parafollicular/C cells, produce calcitonin |
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Identify both tissues. ?What are their major products.
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At A = parathyroid (parathyroid hormone).
At B = thyroid gland (T3, T4) Also parafollicular cells produce calcitonin. |
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What tissue is this? ?Identify cell types at A-B. ?What products are secreted/how is secretion controlled?
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Parathyroid hormone.
A= oxyphil (no known fxn) B= chief cell (PTH) Regulated by blood calcium level. |
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What are the cells at A & B? ?What is produced by them/how is their activity regulated?
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Parathyroid hormone.
A=chief cells (PTH) B=oxyphil cells (none) Regulated by blood calcium level. |
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What is the embryologic origin of the tissue at A & B? ?What are the products of these two tissue compartments? ?How does the activity of tissue at A impact tissue B?
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A- adrenal cortex, mesoderm; minerocorticoids (aldosterone), glucocorticoids (cortisol), weak androgens (DHEA)
B- adrenal medulla, neural crest; norepinephrine, epinephrine Venous ?blood from the adrenal cortex carries hormones into the medulla. ?Relative amounts of norepinephrine/epinephrine are determined by glucocorticoid secretions from zona fasciculata |
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What tissue is this? ?Identify A-B. ?What products are secreted here? ?What controls secretion?
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Adrenal cortex.
A-zona glomerulosa (mineralocorticoids (aldosterone)) reg by BP, sodium via kidney, and renin-angiotensin system. B-zona fasciculata (glucocorticoids (cortisol)) reg by ACTH (stress, sugar) |
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What organ is this? Identify A. ?What product is secreted here/what regulates secretion?
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Adrenal cortex/medulla transition.
A: zona reticularis of cortex. Weak androgens, reg by ACTH or unknown |
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What tissue is this? ?What is this cell type? ?What products is secreted/how is it regulated? ?What is the blood supply of this region?
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Adrenal medulla. ?A: chromaffin. ?secretes epinephrine/norepinephrine. ?Controlled by sympathetic nervous system, stress, glucocorticoids. ?Sources of blood are corticol arterioles and capillaries (one supplies cortex and gets conditioned on the way, the other comes directly through)
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What tissue is this? ?What cell types are present? ?What products are secreted/what regulates secretion?
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Pancreatic islets of langerhans.
Alpha (glucagon), Beta (insulin), Delta (somatostatin), F-cells (PP). Regulated by blood sugar levels, nervous system, paracrine regulation (eg insulin in one islet reg alpha cell secretions?) |
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What tissue is this and what are three major structures you can see?
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Pancreas. ?Pancreatic islet lower left; exocrine acini above and to R inc duct
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What tissue is this?
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Adrenal gland. ?Medulla above, cortex (zona reticularis & zona fasciculata) below.
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What tissue is this? What layer can you see?
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Adrenal gland. ?Capsule on top, then cortex: zona glomerulosa, fasciculata, reticularis; adrenal medulla.
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What two tissue types are seen?
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Top = parathyroid
Bottom = thyroid |
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What tissue is this? ?How can you tell?
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Parathyroid.
Cords of epithelial cells (too regular and too much cytoplasm to be lymphocyte). ?Variable size -- oxyphil cells have more cytoplasm:nucleus ratio; no acinar organization/no ducts. |
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What tissue is this?
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Thyroid follicles.
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