Histology 2nd Semester D.A.T.W Esophagus 5th picture • • •
(1) Neuron cells (2) smooth muscle in cross section (3) smooth muscle in longitudinal section
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Histology 2nd Semester D.A.T.W Part II – Theory • • • •
Esophagus is 25cm long tube which connects the oral cavity to the stomach 102 Within the mediastinum it is covered by connective tissue of the tunica adventitia but upon entering of the abdominal cavity, the last 2cm are free of it On histological slides in cross section the esophagus appears collapsed and has a star shaped lumen during life it can extend once the bolus passes through without any damage to the mucosa Characteristics of the layers o Mucosa Epithelial lining: stratified squamous non-keratinizing epithelium can withstand the physical stress when the bolus is passing through (!! Occasionally keratohyalin granules can be found, but keratinization does not occur) Lamina propria: contains diffuse lymphatic tissue + lymphatic nodules (the nodules often lie in proximity to ducts of the mucous glands located in submucosa) –> lamina propria also is very thin The muscuarlis mucosa begins below the cricoids cartilage and is very strong believed to aid in swallowing (deglutition) o Submucosa Dense irregular connective tissue Larger blood vessels Lymphatic vessels Nerve fibers Ganglion cells Mucous glands (Esophageal glands proper) • Small, compound tubuloalveolar glands • Excretory duct has stratified squamous epithelium • Mucus produced by those glands is slightly acidic and serves to lubricate the inner wall of the tube o Muscularis Inner layer circular Outer layer longitudinal if you don’t believe me check ross book edition 5, p.521 first paragraph) !! Upper third of it is striated muscle which is a continuation of the muscle of the pharynx o Serosa + Subserosa not present o Adventitia present until entering the abdominal cavity
Histology 2nd Semester D.A.T.W
Question 24 – Cardia HE Part I – Histological appearance
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104 Cardia 2nd picture • • • • • •
(1) Cardioesophageal junction (2) Stratified squamous non-keratinizing epithelium (3) Connective tissue papilla (cross section) (4) Secretory epithelium (simple columnar ep.) (5) Lymphatic follicle (6) Muscularis Mucosae (smooth muscle)
Histology 2nd Semester D.A.T.W Cardia 3rd picture PAS • • • •
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(1) Epithelium of Esophagus (slightly PAS positive due to storage of carbohydrates) (2) Secretory epithelium of cardia (strongly PAS positive due to mucinogen granules) (3) Gastric pits (4) Cardiac glands (PAS positive due to mucous secreting cells) some are found in submucosa because the “break through the muscularis mucosae at the junction” (5) Muscularis Mucosae (6) Cardioesophageal junction (7) Salivary glands of esophagus
Histology 2nd Semester D.A.T.W Cardia 4th picture – PAS • • • • • •
(1) Epithelium of esophagus (2) PAS positive carbohydrate stores (3) Cardioesophageal junction (4) Secretory epithelium of cardia (5) Part of cardiac gland (6) gastric pit
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Part II – Theory • • •
Histology 2nd Semester D.A.T.W
Cardia forms a small portion of the stomach surrounding the area where the esophagus opens into the lumen of the stomach It contains the cardioesophageal junction at which a very distinct border is formed between the two epithelia Cardiac glands o Tubular, branched glands o Limited to the cardiac region o Mucous secreting cells (sometimes enteroendocrine cells can be found) o Appearance is similar to that of the esophageal glands o Flattened basal nucleus o Apical cytoplasm filled with mucin granules o Function Contribute to gastric juice Protect esophageal epithelium from acidic reflux
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Question 25 – Corpus Ventriculi HE Part I – Histological appearance • • • • • •
(1) Lamina Propria (2) Muscularis Mucosae (3) Submucosa (4) Muscularis (5) Gastric Pits (6) Gastric (fundic) glands
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Histology 2nd Semester D.A.T.W Fundus 2nd picture • • • •
(1) Gastric pits (2) Upper 1/3 of mucosa (gastric pits) (3) Middle 1/3 (roughly) of mucosa (gastric or fundic glands with mostly parietal + mucous glands) (4) Lower 1/3 of mucosa with chief cells, enteroendocrine cells and parietal cells
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Histology 2nd Semester D.A.T.W Fundus 3rd picture • • • • •
(1) Lumen of gastric gland (2) Parietal cells (3) Mucous secreting cells (4) Connective tissue of lamina propria (5) Chief cells
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Histology 2nd Semester D.A.T.W Fundus 4th picture – CONGO-H
111 DEMONSTRATION ONLY • The histological structure is the same as in the pictures above • 3 parts of mucosa can be seen with gastric pits and the two main types of the gastric glands
Histology 2nd Semester D.A.T.W Fundus 5th picture – CONGO-H
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Part II – Theory • •
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Histology 2nd Semester D.A.T.W
The fundus contains the gastric glands which secrete the main components of the gastric juice (components and mechanisms mentioned above) The mucosa can be divided into three parts 113 o Upper 1/3 gastric pits Ramified tubular ducts open into the gastric pits 2-5 gastric glands open into one pit o Middle 1/3 upper part of gastric glands NECK PORTION (or ISTHMUS) Parietal cells dominate (large eosinophilic cells with a round nucleus) let the middle third of the mucosa appear mainly eosinophilic Inbetween them you also find mucous secreting cells (remember that they appear different then from the secretory epithelium!) REMEMBER that the mucous secreting cells are only active during digestion o Lower 1/3 lower part of gastric glands BASE PORTION Chief cells dominate here (basophilic cells due to rER, with nucleus at basal part of cell) let lower part of mucosa appear basophilic secrete pepsinogen Interspersed you can also find enteroendocrine cells (apical nucleus) secrete VIP, Gastrin, Substance P etc. into the bloodstream of the underlying capillaries you don’t have to recognize those in your exam Sometimes you can see parietal cells which sit behind the chief cells and communicate with the lumen of the gland only by a very small apical surface protrusion inbetween the chief cells Below the last 1/3 of the gland you see the muscularis mucosae and below that the submucosa starts
Histology 2nd Semester D.A.T.W
Question 27 – Pylorus HE Part I – Histological appearance • • • • • •
(1) Mucosa (2) Gastric Pits (3) Gastric Glands (4) Muscularis Mucosae (5) Submucosa (6) Tunica Muscularis
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Histology 2nd Semester D.A.T.W Pylorus 2nd picture • • • • •
(1) Secretory epithelium (2) Gastric Pits (3) Gastric Glands (4) Muscularis Mucosae (5) Submucosa
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Histology 2nd Semester D.A.T.W Pylorus 3rd picture • • • • •
(1) Gastric Pit (2) Lamina Propria (3) 2+4 = Mucosa (4) Muscularis Mucosae (5) Pyloric Mucous glands
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Histology 2nd Semester D.A.T.W Pylorus 4th picture • • • • • •
(1) Lamina Propria (2) Muscularis Mucosae (3) Gastric Pit (4) Pyloric mucous glands (5) Submucosa (6) Blood Vessels
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Histology 2nd Semester D.A.T.W Pylorus 5th picture
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Histology 2nd Semester D.A.T.W Pylorus 6th picture
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Histology 2nd Semester D.A.T.W Pylorus 7th picture
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Part II – Theory • • • • •
Histology 2nd Semester D.A.T.W
The pyloric part of the stomach is the part which borders the opening into the duodenum The gastric pits here go deeper span about 1/2 of the mucosa Pyloric glands are branched, coiled, tubular glands Mucous cells similar to the secretory surface epithelium secrete viscous mucus into a relative wide lumen The tunica muscularis in the pyloric part is very thick presence of sphincter muscle which can close the entrance of the duodenum o in newborns this muscle can be hypertrophied closure of stomach exit strong vomitting
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Question 28 – Pylorus PAS-H
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Part I – Histological appearance • • • •
(1) Border between gastric pits and glands (2) Gastric pits (3) Gastric glands (4) Muscularis Mucosae NOTE the PAS positive secretory epithelium and the PAS positive gastric glands as well as the positive stained mucous secreting cells within the gastric pits
Histology 2nd Semester D.A.T.W Pylorus PAS-H 2nd picture Here you can see the same in higher123 magnification The marks of the department are sufficient • (lp) Lamina Propria • (fg) Gastric Pit • (gl) Gastric Glands • (mm) Muscularis Mucosae Again note the PAS positive structures
Histology 2nd Semester D.A.T.W Pylorus PAS-H 3rd picture Same as 1st picture now in even higher 124 magnification • (fg) gastric pit • (lp) lamina propria • (gl) gastric gland • (mm) muscularis mucosae AGAIN NOTE PAS POSITIVE STRUCTURES
Histology 2nd Semester D.A.T.W Pylorus PAS-H 4th picture Very nice PAS staining You can disctinctly see the mucous125 secreting cells located on the inner side of the gastric pits (mucinogen granules stain PAS positive due to carbohydrate content)
Histology 2nd Semester D.A.T.W Part II – Theory • •
PAS (once again mofos..) Periodic Acid Schiff reagent stains carbohydrates with a distinct reddish-pink colour PAS positive structures here are all structures which contain mucinogen granules o Secretory epithelium of stomach o Mucous secreting cells located on inner wall of gastric pits in pylorus they secrete a very viscous mucous and are similar to the secretory epithelium cells (NOTE that in cardia and fundus they are smaller and secrete a more fluid mucous) o Mucous secreting cells of gastric glands same as in the pits
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7th week: Intestines 127 (NOTE: only CHANGES in the normal morphology of the alimentary canal are mentioned here otherwise look Part 6) 1) Small intestine longest portion of digestive tract (6m) and dividided into three anatomical portions • Duodenum shortest and widest part, begins at pylorus and ends at duodenojejunal junction • Jejunum gradually changes its characteristics and finally becomes ileum • Ileum ends at ileocecal junction • Small intestine is principal site for absorption of nutrients chyme from stomach enters duodenum via pyloric sphincter relaxation mixes with pancreatic juice, bile and enzymes of the enterocytes break down sugars to monosaccharides and proteins to amino acids absorption • distal portion of small intestine absorbs water and electrolytes •
Characteristical changes of morphology of the alimentary canal layers: (for the general layers look general theory part 6!) o Absorptive surface area of small intestine is increased by tissue and cell specifications of mucosa and submucosa Plicae circulares (or circular folds) • protrude into the lumen of the small intestine and contain core of submucosa • most numerous in distal duodenum, reduce in number towards jejunum/ileum Villi • Fingerlike protrusion extending into the lumen from the mucosa completely cover surface of small intestine inner lining • 0.5-1mm • Each villus contains in its core (made up of loose C.T. lamina propria of tunica mucosa) o White blood cells o Fenestrated capillaries o Lacteal (in midline) lymphatic capillary which drains into lymph nodes in the mesentery o Smooth muscle cells derived from muscularis mucosae contraction forces lymph into lymphatic network around muscularis mucosae o Intestinal glands (or Lieberkühn crypts) Tubular glands epithelium (simple columnar) continuous with surface epithelium of mucosa Extend from muscularis mucosae through the lamina propria and open at the base of the villi into the lumen
Histology 2nd Semester D.A.T.W Microvilli Cells of lining (enterocytes) each also possess their “own” villi which therefore are tiny microvilli Each cell possesses several thousands are the main surface increasing factor o GALT (Gut Associated Lymphatic Tissue) In the lamina propria of the small intestine vast amounts of lymphocytes can be found aggregated in nodules called “peyer`s patches” Lymphocytes are also located between the epithelial cells this GALT serves as immunologic barrier In cooperation with M-cells, the lymphocytes monitor entering molecules and microorganisms for antigens Characteristic cell types found in small intestine o Enterocytes absorptive function Columnar cells with basal nucleus Apical membrane contains microvilli increase surface area 600x (form striated border) • Contain vertically running actin filaments, anchored in terminal web (horizontal running network of contractile microfilaments) contraction increases surface area if needed Are bound to each other by tight junctions (remember from biology!) establish impermeable barrier between intestinal lumen and intercellular compartment of enterocytes all substances that want to enter the bloodstream have to go “through” the enterocytes by selective transport systems Pump out Na+ into the intercellular space beneath the tight junction osmotic pressure pulls water out of the cell water enters the cell together with sodium down their concentration gradient at the apical membrane Additionally lateral plications are present but not described here (for nerds: ross edition 5 p.539, have fun) o Goblet cells produce mucus Increase in number from duodenum to terminal part of ileum Middle and apical portion are occupied by mucinogen granules (LOST DURING HE STAINING) Basal part contains heterochromatic nucleus, rER and free ribosomes stains basophilic o Paneth cells secrete antimicrobial substances regulate bacterial flora of small intestine Found in bases of intestinal glands Basophilic cytoplasm and large, eosinophilic granules (makes them easy to recognize with HE) Granules contain lysozyme, a-defensins (function as mediators of Cytotoxic CD8+ T-cells), zinc and others Phagocytotic activity o
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Histology 2nd Semester D.A.T.W Enteroendocrine cells (also found in stomach) produce para- and endocrine hormones Endocrine • CCK increases pancreatic + gallbladder secretion; stops gastric secretion and motility • Secretin same effect as CCK • GIP stimulates insulin release in the pancreas • Motilin initiates gastric and intestinal motility Paracrine • Histamine • Somatostatin o M-cells modified type which overlie peyer´s patches in lamina propria Have microfolds instead of microvilli on their surface Take up microorganisms and macromolecules from the lumen in endocytotic vesicles transported to basolateral membrane discharged close to CD4+ T-cells in case of antigens immune reaction o Intermediate cells Make up most of the cells in lower half of intestinal gland Capable of cell division before they differentiate into either enterocyte or goblet cell Duodenum o Submucosal glands are present (only in this part of small intestine) also called “Brunner`s glands” Branched, tubular glands Secrete zymogens (general name for inactive precursor enzymes) and mucus Secretion has alkalic pH due to HCO3- ions and glycoproteins protects proximal part of small intestine from gastric acids + creates optimal pH for pancreatic enzymes Ileum Contains massive aggregations of lymphatic tissue in the lamina propria (usually found at the site of the small intestine which is o oppositely to the mesenteric attachment) Called aggregated nodules OR Peyer`s patches Contractions: o Local contractions (circular layer of smooth muscle) which push chyme in both directions within the small intestine (sphincters closed) and let it flow back upon relaxation mixing of chyme with digestive juices o Peristalsis moves chyme towards large intestine (coordinated action of longitudinal and circular smooth muscle) o
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• •
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Histology 2nd Semester D.A.T.W •
All mature cells of intestinal epithelium derive from one single stem cell population o Stem cells are located at the base of the intestinal gland
2) Large intestine
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• •
The layers of the alimentary canal are present throughout the large intestine but they exhibit a different formation than in small intestine Special characteristics o EXCEPT for rectum, anal canal and vermiform appendix outer longitudinal layer of Tunic muscularis shows three thickened bands TENIAE COLI o External surface of cecum and colon show saculations known as “haustrae” no plicae (circular folds) or intestinal villi are present o Omental appendices (fatty cysts) are present on outer surface Function o Reabsorption of water and electrolytes Cells o Contains same cells as small intestine EXCEPT Paneth cells (absent in human)
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Histology 2nd Semester D.A.T.W
Question 29 – Duodenum HE
Part I – Histological appearance • • • • • • • •
(lp) Lamina propria (Br) Brunner`s gland (mm) muscularis mucosae (sm) submucosa (tm) tunica muscularis (circular part) (ly) lymphatic nodule (kr) intestinal glands (yellow line) borderline between villi and the intestinal glands
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Histology 2nd Semester D.A.T.W Duodenum 2nd picture • • • • •
133 (1) Borderline between villi and intestinal glands (2) lamina propria (3) muscularis mucosae (4) Intestinal gland (5) Brunner´s gland
Histology 2nd Semester D.A.T.W Duodenum 3rd picture • • • • •
134 (1) Intestinal gland (2) Paneth cell (3) enteroendocrine cells (4) muscularis mucosae (5) part of Brunner´s gland
Histology 2nd Semester D.A.T.W Duodenum 4th picture
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Histology 2nd Semester D.A.T.W Duodenum 5th picture
136 Nothing around something intestinal villus Something around nothing gastric gland with inner lumen
Histology 2nd Semester D.A.T.W
Duodenum 6th picture
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Histology 2nd Semester D.A.T.W Part II – Theory
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Histology 2nd Semester D.A.T.W
Question 30 – Jejunum HE
Part I – Histological appearance • • • •
(1) Plicus or „circular fold of kerkring“ made by submucosa (2) Intestinal villus (NOT TO MIX WITH MICROVILLUS) made by lamina propria mucosae (3) Tunica muscularis inner layer (4) Tunica muscularis outer layer
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Histology 2nd Semester D.A.T.W
Jejunum 2nd picture • • • • •
(1) Villus (2) Circular fold and submucosa (3) Tunica muscularis (4) Enterocytes (5) Crypts of lieberkühn (intestinal glands)
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Histology 2nd Semester D.A.T.W Jejunum 3rd picture
141 • • • • •
(1) Central lacteal (2) Endothelial cells (3) Goblet cells (4) Microvilli brush border (5) Nuclei of enterocytes This slide shows 2 intestinal Villi at high magnification The lamina propria forming the core of the villus contains o Smooth muscle cells o Capillary plexus o Central lactal (lymphatic vessel) in the middle usually not seen as good as here
Histology 2nd Semester D.A.T.W
Jejunum 4th picture • • • •
(1) Lieberkühn crypt (2) Paneth cells (3) Goblet cells (4) Lamina propria
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Jejunum 5th picture (PAS-H) • • • • • • •
(1) Enterocytes (2) Goblet cells (3) Brush border (4) Paneth cells (5) Lieberkühn crypt (6) Muscularis mucosae (7) Lamina propria
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Histology 2nd Semester D.A.T.W Part II – Theory •
In the jejunum the submucosal glands form the duodenum cannot be found anymore
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Histology 2nd Semester D.A.T.W
Question 31 – Ileum HE
Part I – Histological appearance • • • • • • •
(1) Peyers patches (located in submucosa) (2) lymphatic tissue (peyer`s patch) invading the lamina propria (3) Intestinal villus with lamina propria core (4) Muscularis mucosae (5) Submucosa (6) Tunica muscularis circular layer (7) Tunica muscularis longitudinal layer
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Histology 2nd Semester D.A.T.W
146 Ileum 2nd picture • • • • •
(1) Tunica muscularis inner circular layer (2) Tunica muscularis outer longitudinal layer (3) Peyer`s Patches (4) Intestinal villus (5) Plica (circular fold)
Histology 2nd Semester D.A.T.W Ileum Theory • •
Peyer´s patches are found in the submucosa of the ileum can sometimes invade the lamina propria of the mucosa Above these lymphatic nodules the enterocytes of the epithelium change for M-cells which have less microvilli and are responsible for transporting antigens to the lymphatic nodules
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Question 32 – Colon HE Part I – Histological appearance • • • • • •
(1) Tunica muscularis circular layer (2) Tunica muscularis longitudinal layer (3) Submucosa (4) Lamina propria (5) Muscularis mucosae (6) Crypt of Lieberkühn
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Colon 2nd picture • • • • • • •
(1) Lamina Propria (2) Lieberkühn crypt (3) Goblet cells (4) Muscularis Mucosae (5) Submucosa (6) Blood vessel (7) Submucosal plexus
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Histology 2nd Semester D.A.T.W Colon 4th picture Something around nothing crypts of lieberkühn in cross section
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Histology 2nd Semester D.A.T.W Large intestine theory • • •
Obviously the department has massive amounts of slides about the large intestine try not to memorize individual slides look for intestinal villi and submucosal folds and PANETH cells if they are present it is a slide from the small intestine and NOT from the colon In slides taken from an area of a tenia the external layer of the tunica muscularis is especially thick
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Question 32 – Appendix HE Part I – Histological appearance Ist shortly before the exam and i dont want to mark anymor pictures so i just describe what you see Appendix in cross section Layers 1) Epithelium mucosae – simple columnar 2) Lamina propria lieberkühn crypts 3) Muscularis mucosae 4) Submucosa 5) Tunica muscularis inner circular (cut longitudinally to its axis) 6) Outer longitudinal layer cut transverse to its axis NOTE the lymphatic follicles invading the lamina propria GALT Also called tonsil of the intestines 7) Appendix is intraperitoneal outer layer serosa with mesothelial cells
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Histology 2nd Semester D.A.T.W Part II – Theory •
The appendix is usually surgically removed in case of acute appendicitis i dont know if you can but then on the slides you should see neutrophil granulocytes invading the mucosa (additionally tot he 2ndary lymphatic follicles everywhere)
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Question 34 – Rectum HE
Part I - Histological appearance • • • •
(1) Border between intestinal and anal part (2) Intestinal part (3) Border between Columnar zone (above) and hemorrhoidal zone (below (4) Border between hemorrhoidal zone (above) and cutaneus zone (below)
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156 Rectum 2nd picture • • •
(1) Border between intestinal zone and columnar zone (2) Intestinal zone (3) Columnar zone
Histology 2nd Semester D.A.T.W
157 Transition of columnar zone (left) and hemorrhoidal zone (right, covered with stratified squamous non-keratinizing epithelium). See the stratified columnar epithelium in the zona columnaris (next to the epithelial transition is very regular). (In younger individuals it is usual that the simple columnar epithelium does not change directly to str. squamous epithelium.)
Histology 2nd Semester D.A.T.W
158 Transition of the hemorrhoidal zone (right upper half of the photo, covered with stratified squamous non-keratinizing epithelium) and cutaneous zone (right - lower half of the photo, covered with stratified squamous keratinizing epithelium). External to the submucosa the thickened lowest part of the inner circular muscle layer, the sphincter ani internus muscle is recognizable (middle of photo). On the left of the photo the immature skeletal muscle (myotubules) of the external sphicter is seen.
Histology 2nd Semester D.A.T.W
Developing skeletal muscle fibers in the sphicter ani externus, high power. Since the slide is from a newborn, the muscle in not fully mature yet (paler cross sections intermingle with the mature, more eosinophilic fibers)
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Histology 2nd Semester D.A.T.W Part II – Theory • • • •
Rectum slide is divided into four parts 1) the colorectal zone which looks alike with the large intestine epithelial covering is simple columnar cells with microvilli 2) Anal transitional zone epithelial covering changes from simple columnar to stratified squamous non keratinized epithelium 3) Squamous zone
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9th week: Liver,gall bladder,pancreas 1)
Liver • Function o Uptake and storage of nutrients and vitamins from bloodstream Vitamin A Vitamin D Vitamin K Vitamin B12 o Storage of glucagon and maintenance of blood glucose levels o Regulation of very low density lipoproteins (VLDLs) o Production of plasma proteins Albumins Alpha and beta globulins Glycoproteins (haptoglobin, transferring, hemopexin are important for iron transport and storage) Prothrombin, fibrinogen o Storage of Iron o Degradation of toxins and drugs makes them soluble in two phases 1) Oxidation hydroxylation or carboxylation performed in SER of Hepatocytes by Cytochrome P450 complex 2) Conjugation with glucuronic acid, glycine, taurine makes the educts even more soluble now they can dissolve in water and be cleared by the kidneys o Endocrine function (not described here) can modify hormones o Exocrine function produces and secretes bile • Blood supply o Receives blood from two sources Portal vein rich in nutrients, low in oxygen content interlobar veins interlobular veins circumlobular veins Proper hepatic artery low in nutrients, rich in oxygen content interlobar arteries interlobular arteries circuml. Artery • After this the blood enters the hepatic sinusoids (described below) and enters the central vein • sublobular vein hepatic veins inferior vena cava
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Histology 2nd Semester D.A.T.W •
Structural organization of the liver o Liver is organized in functional units lobules (based on what you focus on concerning liver function, the border of the lobules is different) Classic lobule • each lobule is a segment of hepatocytes, inbetween which hepatic sinusoids run towards the central vein (located in the center of the lobule ☺) • the lobules are bordered by connective tissue in that the border forms a hexagonal lobule within the connective tissue three vessels are running open into the portal triad (three vessels usually seen in cross section at the meeting point of three hexagonal corners) o bile duct o Interlobular vein o interlobular artery • sinusoids are fenestrated capillaries which run inbetween the strands of hepatocytes • spaces of disse inbetween the endothelium of the sinusoids and the hepatocytes (basal surface) is a space from the basal surface of the hepatocytes small microvilli extend increase surface area for absorption OR secretion • Classic lobule corresponds to the described hexagone with connective tissue borders Portal lobule corresponds to the area of adjacent lobules around a portal triad which is bordered by three lines drawn between the three central veins forming a triangle with the portal triad in the center this lobule “focuses” on the bile secretion and marks the area of the three classic lobules which secrete bile that drains into this central portal triad (look at a picture in the book and you will understand Liver acinus • Partial areas of two classic lobule adjacent to each other diamond shaped • From each central vein, 2 line are drawn, each one towards one of the two portal triads lying inbetween the two central veins • The area marked by that is divided into three zones o Zone 1 closes to connective tissue septum and the vessels running between the two portal triads Receives oxygen and toxics first from the vessels consequences for cells • First to show morphologic changes upon contact with high amount of toxins (E.g. due to bile duct occlusion) • Last to die if circulation does not provide enough oxygen o Zone 2 intermediate zone o Zone 3 closes to the central veins First to die from hypoxia First to show fat accumulation Last to react to increased accumulations of toxins or bile duct occlusion
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Cells of the liver o Hepatocytes Cuboidal shaped cells (following our teacher, book says polygonal) 20-30µm diameter Round nuclei often binucleated TETRAPLOID (contain four homologous chromosomes) two or more nucleoli present Pale eosinophilic cytoplasm contain lysosomes and lots of glycogen Long life span five months Inbetween to hepatocytes a bile canaliculus is present, above and beneath the membranes of the two cells are attached by occluding junctions (these canaliculi can only be seen in special AgNO3 preparations) Contain high amounts of peroxisomes Contain extensive smooth endoplasmatic reticulum o Ito cells Found in perisinusoidal space Primary storage site for Vitamin A (in form of retinyl esters within cytoplasmic droplets) During cirrhosis lose their storage capability and differentiate into myofibroblasts secrete collagen (play also a role in restoring extracellular matrix after liver injury) o Kupffer cells Macrophages derived from monocytes Sit in space of disse Send processes into the sinusoids monitoring them for antigens Are a member of the mononuclear phagocytotic system you have to know all members for the exam: • Kupffer cells (liver) • Langerhans cells (skin) !! do not mix up with the islets in the pancreas) • Histiocytes (connective tissue) • Osteoclasts (bone) • Chondroclasts (cartilage) • Alveolar macrophages (lungs)
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Histology 2nd Semester D.A.T.W •
Bile formation and secretion o Bile is formed in hepatocytes (about 1L per day in average human) o Contains bile salts (90%), cholesterol and bilirubin (responsible for green color of bile) !! in case of bilirubin entering the blood (due to high pressure in bile duct after occlusion OR insufficient liver function due to problem with hepatocytes) jaundice (yellowish color of the skin) o From there it flows into the gallbladder via the biliary tree from hepatocyte towards gallbladder: Bile canaliculi inbetween hepatocytes 0.5µm in diameter Intrahepatic ductule (canal of Hering) several bile canaliculi join together within the classical lobule, close to the portal triad • Canal of hering is lined by simple cuboidal epitheliar cells cholangiocytes • 1.0-1.5µm diameter Interlobular bile duct (located in portal triad) • 15-40µm diameter • Their cholangiocytes initially is cuboidal but with increase in diameter it becomes columnar Right and left hepatic ducts (interlobular ducts join together in the right and left lobe of liver) Common hepatic duct (from r+l ducts) • This duct is extrahepatic contains all layers of alimentary canal (look Q. 6) except the muscularis mucosae Cystic duct • Connects common hepatic duct to gallbladder • Carries bile in and out of gallbladder Common bile duct (junction of common hepatic and cystic duct) • Carries bile towards the duodenum • Opens into duodenum at ampulla of vater forming major papilla on inside of duodenum • The opening is surrounded by the sphincter of oddi which regulates the inflow of bile into the duodenum
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165 Question 36 – Liver (hog) AZAN Part I – Histological appearance • • •
(1) Central vein (2) connective tissue border (3) portal triad Picture shows classic lobule In human the border between the lobules is not so visible
Histology 2nd Semester D.A.T.W Liver azan 2nd picture • • • • •
(1) Interlobular artery (2) Interlobular vein (3) Interlobular bile duct (4) connective tissue border (5) Hepatocytes
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Question 37 – Liver (human) AZAN Part I – Histological appearance • • • • • •
(1) Central Vein (2) Hepaocytes (3) hepatic sinusoids (4) Interlobular vein (5) Interlobular artery (6) Interlobular bile duct Note the blueish covering on the hepatocytes space of disse
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Liver azan 2nd picture • • • • •
(1) Central vein (2) Opening into sinusoids (3) Sinusoid (4) Nuclei of Hepatocytes (5) Kupffer cells
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Histology 2nd Semester D.A.T.W Liver azan 3rd picture • • • •
(1) Interlobular vein (2) Interlobular artery (3) Interlobular bile duct note the cuboidal cholangiocytes lining the bile duct
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Histology 2nd Semester D.A.T.W Part II – Theory • • •
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AZAN Azocarmine blue stains connective tissue The space of disse is stained blue here due to the presence of ,, can be well seen inbetween sinusoid endothelium and basal surface of hepatocytes Hepatocytes form chord like structures (also called “plates”) from the central vein towards the border of the classical lobule inbetween them run the hepatic sinusoids
Interlobular veins have a much larger lumen then the other two vessels of the portal triad Interlobular arteries are one of the two smaller vessels in the portal triad have layer of eosinophilic smooth muscle in their wall (can be seen under higher magnifications) Interlobular bile ducts are lined by well distinguishable epithelium (either cuboidal or columnar)
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Histology 2nd Semester D.A.T.W
Question 38 – Liver (human) HE Part I – Histological appearance • • •
(1) Central vein (2) Connective tissue border (3) Portal triad
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Histology 2nd Semester D.A.T.W Liver HE 2nd picture • • •
(1) Sublobular vein (no sinusoid openings) (2) Interlobular vein (3) Portal triad
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Histology 2nd Semester D.A.T.W
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Liver HE 3rd picture • • •
(1) Interlobular vein (2) Interlobular artery (3) Interlobular bile duct
Histology 2nd Semester D.A.T.W Liver HE 4th picture • •
174 (1) Sublobular vein (2) Central vein
Histology 2nd Semester D.A.T.W
Liver HE 5th picture • • • • •
(1) Hepatocyte Nucleus (2) Hepatocyte nucleolus (3) Sinusoid (4) Kupffer cell (5) Ito cell
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Histology 2nd Semester D.A.T.W Part II – Theory • •
176 In the human, the connective tissue border between the classic lobules is not very visible The Central veins can be distinguished from the sublobular veins in that the central veins are fenestrated and the hepatic sinusoids open into them, while the sublobular veins have a continuous endothelial lining
Histology 2nd Semester D.A.T.W
Question 39 – Liver Indian-ink Part I – Histological appearance • •
(1) Central vein (2) Interlobular veins
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Histology 2nd Semester D.A.T.W Part II – Theory • • •
The portal vein draining into the liver has been injected with indian ink perfuses into the liver via the veins The central vein is good visible as it is filled with ink AND you can see ink filled sinusoids draining into it The interlobular veins are the only structure visible in the portal triad! They are small and not surrounded by distinct sinusoids! (Higher magnification would help here )
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Histology 2nd Semester D.A.T.W
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Question 40 – Bile Capillaries (AGNO3) Part I – Histological appearance Vessel: Central vein Fine black lines bile canliculi Underlying wider yellow areas hepatic sinusoids White area hepatocytes
Histology 2nd Semester D.A.T.W
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Histology 2nd Semester D.A.T.W Part II – Theory
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Bile canaliculi or capillaries are small bile vessels that run inbetween hepatocytes In this preparation silver nitrate solution filled the bile canliculi and then the slide was exposed to UV light silver precipitates as black substance within the canaliculi and therefore they are well visible
Histology 2nd Semester D.A.T.W
Question 41 – Vesica fellae HE Part I – Histological appearance (Vesica fellae = Gallbladder) • • • • • •
(1) Simple columnar epithelium with microvilli (2) Fold of the lamina propria meet in between the arrows (3) Rokitansky-Aschoff sinus (4) Tunica Mucosa (5) Tunica Muscularis (6) Tunica adventitia
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Histology 2nd Semester D.A.T.W Part II – Theory -> GALLBLADDER
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The gallbladder does not contain o Muscularis Mucosae o Tunica Submucosa BUT it contains a very THICK Tunica Muscularis The Lamina propria creates surface folds which bend laterally and can meet this can create deep surface invaginations (Rokitansky-Aschoff sinuses) in which bacteria can accumulate [these invaginations can appear below the surface due to slide sections (although they are actually in contact with the surface] THESE ARE NOT DUCTS OF LUSCHKA (no slide in POTE contains these ducts) which are aberrated bile ducts, seen externally to the Tunica muscularis Dependent on contact to Liver surface or not Outermost layer is Tunica Serosa OR Tunica adventitia (if in contact with peritoneum of liver) Function o Stores and concentrates the bile secreted by the liver (enters the gallbladder through the cystic duct) o Upon contraction of the Tunica Muscularis, the content of the gallbladder is squeezed into the cystic and further down into the common bile duct Bile concentration o Na+ and Cl- ATPases present in the epithelial cells pump those ions into the intercellular space creation of osmotic gradient water moves from lumen and cytoplasm into the intercellular space concentration of bile located in the lumen by removal of water o water is forced into lamina propria by hydrostatic pressure and passes into fenestrated capillaries
Histology 2nd Semester D.A.T.W
Question 42 – Pancreas HE
Part I – Histological appearance • • • •
(1) Islet of Langerhans (endocrine pancreas) (2) acinar cells (exocrine pancreas (3) Neuroinsular cells (4) Connective Tissue septum
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Histology 2nd Semester D.A.T.W
185 Pancreas 2nd picture • • •
(1) Centroacinar cells (2) Eosinophilic apex of acinar cells (3) Acinus Note the white spaces inbetween the acini which are due to the fixation method the acini shrink and pull away from their connective tissue
Histology 2nd Semester D.A.T.W
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Pancreas 3rd picture • • •
(1) Islet of Langerhans (2) Pancreatic sinusoids (3) Acini NOTE that you cannot tell the difference between the alpha, beta and delta cells of the islet with common stainings but only with immunohistochemistry
Histology 2nd Semester D.A.T.W
187 Pancreas 4th picture (LIGHTGREEN- azocarmine-Gömöri basic fuchsin staining) • • • • • •
DEMONSTRATION ONLY (1) Islet of Langerhans (2)Beta cells (dark purple cells) (3)Alpha cells (pale cells) (4) oops (5) Acini (6) Blood vessels
This staining is oldschool since the development of immunohistochemistry and probably in here since Gömöri sounds Hungarian ☺
Histology 2nd Semester D.A.T.W
188 Pancreas 5th picture (Immunohistochemistry) Demonstration only brown cells are islets of langerhans
Histology 2nd Semester D.A.T.W Part II – Theory PANCREAS •
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189 Structure o Lobulated organ (although the connective tissue septa inbetween the lobules are minor) BUT no connective tissue capsule surrounding it o Head, body and tail o Main pancreatic duct extends through the length of the organ and empties together with the common bile duct into the duodenum Function o 90% exocrine organ synthesizes and secretes digestive enzymes into the duodenum Serous gland (!! Closely resembles the parotid gland can be differentiated by a) Langerhans islets; b) Presence of Centroacinar cells; c) Stronger capillarisation; d) less fat than parotid gland) Acinar cells • pyramidal shaped wide base, small apex facing the lumen • basophilic base RER, Mitochondria • eosinophilic apex zymogen granules (most numerous in fasting individuals) Acinus • The intercalated duct extends into the acinus in cross section its flat squamous epithelial cells can be seen surrounded by the acinar cells these squamous cells are “centroacinar cells” Secretion pathway • Enzymes are synthesized in the RER of the acinar cells and packed into zymogen granules these are released into the lumen of the acinus (Merocrine secretion via exocytosis) • Intercalated ducts intralobular collecting ducts larger intralobular ducts (lined by low columnar epithelium directly into main pancreatic duct Secreted pancreatic enzymes are in inactive form to prevent self digestion of the tissues • Trypsinogen is activated by phosphorylation by enterokinase located in the glycocalix of the intestinal villi • Active trypsin activates the other enzymes AND enhances the activation of trypsinogen (positive feedback effect) o 10% endocrine organ synthesizes and secretes insulin and glucagon into the bloodstream Consists of the “islets of Langerhans” embedded as islands within the exocrine pancreas (most numerous in the tail) • Polygonal cells that stain pale in HE sections • Cells are surrounded by fenestrated capillaries (pancreatic sinusoids) • Three principal cell types o Alpha cells (A-cells) 15-20% of islet population; secrete glucagon o Beta cells (B-cells ) 70% of islet population; secrete insulin o Delta cells (D-cells) 5-10% of islet population; secrete somatostatin
Histology 2nd Semester D.A.T.W
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Secretes hormones which regulate blood glucose level • Insulin o Secreted by beta cells of Islet of Langerhans o Has multiple actions on individual tissues o General functions Uptake of glucose from circulation Storage of glucose by activation of glycogen synthase glycogen is produced Phosphorylation and use of glucose stimulates glycolysis • Glucagon o Opposite function of insulin o Stimulates release of glucose into bloodstream o Stimulates gluconeogenesis synthesis of glucose de novo from amino acids and metabolites o Stimulates glycogenolysis breakdown of glycogen into glucose o Stimulates hepatic lipase • Somatostatin o Inhibits insulin and glucagon secretion (it’s a major inhibitory hormone of the gastric system) Pancreatic enzymes (secreted by exocrine pancreas) o Proteolytic endopeptidases Trypsinogen, chymotrypsin o Proteolytic exopeptidases Procarboxypeptidase Proaminopeptidase o Alpha –amylase Cleaves polysaccharides into mono and disaccharides by attacking the glycosidic bond o Lipase Only fat digesting enzyme in the body o Nucleotic enzymes DNAse cleaves DNA strands into nucleotides RNAse cleaves RNA strands into nucleotides
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Histology 2nd Semester D.A.T.W
10th week: Kidney,ureter,urinary bladder 191 1) Kidneys • Conserve body fluid and electrolytes and remove metabolic waste they receive 25% of the cardiac output and produce urine from it (initial an ultrafiltrate from the bood which will be modified by selective resorption and specific secretion of substances by the cells of the tubules) • The final urine produced within the kidneys contains water, electrolytes, waste products [urea, uric acid, creatinine] and breakdown products of various substances • General structure of the kidney o Medial border is concave and contains hilum renal vessels and nerves enter here and the renal pelvis exits in form of the ureter o Capsule Kidney surface is covered by dense C.T. capsule which consists of two distinct layers outer layer of fibroblasts and collagen fibers and inner layer with cellular component of myofibroblasts (contractility of those resist volume and pressure variations which can accompany variations in kidney function) The capsule turns inward at the hilum becomes continuous with the connective tissue forming the walls of the calyces and renal pelvis o Interstitial tissue connective tissue of kidney parenchyma made up of fibroblasts and myofibroblasts o Cortex Is the tissue aside of the pelvis and the medullary pyramids fills spaces inbetween (renal column) and above (cortex corticis) the renal pyramids Consists of renal corpuscles (or malphigian corpuscles), the convoluted (coiled) tubular system and an extensive vascular supply The nephron is the functional unit of the kidney and is described in detail below o Medullary pyramids (Medulla) The medulla is made of the straight tubular system and is less vascularized therefore it has a different appearance in section of a fresh kidney Due to the parallel arrangement of the straight tubules the medulla portions appear as pyramids 8-18 present per human kidney Base of pyramid faces the cortex and the apex (known as renal papilla) the renal pelvis Each pyramid opens into a minor calyx which unite to major calices which in turn form the ureter, leaving the kidney at the hilum and going to the bladder Medullary pyramids are lobes in the functional view of a kidney although they are not separated by connective tissue o Medullary rays Appear as vertical striations to the naked eye, which sit on top of the renal pyramids extending into the cortex BUT not touching the capsule Each medullary ray is an aggregation of straight tubules and collecting tubules One medullary ray forms the midline of a cortical labyrinth or cortical lobule o Cortical lobule Contains malphigian corpuscles, convoluted tubules of the nephrons and the collecting tubules Is a functional segment between two interlobular arteries which run perpendicular to the base of the pyramid upwards Center of it is a medullary ray
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Nephron Histology 2nd Semester D.A.T.W o Functional unit of the kidney o 2mio/kidney in humans o Responsible for urine production (details below) 192 o Cortical Nephron renal corpuscle is located in outer part of cortex have short loops of Henle extending only in the outer medulla o Juxtamedullary nephrons 1/8 of total nephron count renal corpuscle in close proximity to the base of the pyramid long loops of Henle and long ascending thin segments extend far into inner region of the pyramid General organization of Nephron o Renal or Malphigian Corpuscle Capillary tuft (10 to 20 capillary loops) which is supplied by afferent arteriole and drained by efferent arteriole Glomerulus The efferent arteriole branches into the peritubular capillary network which supplies the tubules with blood and takes up substances which have been reabsorbed from the tubular fluid The capillary tuft is surrounded by a cup like structure formed of a double layer of epithelium with an empty space inbetween the layers which is continuous with the proximal tubule bowman´s capsule containing bowman´s space Vascular pole: location on malphigian corpuscle at which the afferent arteriole “enters the glomerulus” and the efferent arteriole “leaves the glomerulus” Urinary pole: opposite to vascular pole here the proximal tubule begins as a continuation of bowman´s space o Filtration apparatus consists of three components 1) Fenestrations of glomerular capillaries (larger and more numerous than in normal fenestrated capillaries) 2) Glomerular basement membrane (300-350nm) product of endothelium and pododytes (below) main component of filtration barrier 3) Visceral layer of bowman´s capsule contains podocytes o Special cell types of the renal corpuscle Podocytes • Lie in apposition to capillary network and their processes (pedicles) surround the capillaries and interdigitate with processes of neighboring podocytes (NOTE that the parietal layer of bowman´s space is made by simple squamous epithelium) • Elongated slit like spaces left open between the pedicles are filtration slits through which the ultrafiltrate from the capillaries can enter bowman´s space Mesangial cells • Cells + extracellular matrix mesangium most obvious at vascular pole • Cells are enclosed by the basal lamina of the glomerular capillaries • Functions o Phagocytosis remove trapped residues and aggregated proteins from glomerular basement membrane cleaning the glomerular filter o Structural support for podocytes o Secretion of molecules in response to glomerular injury (Interleukin 1, PDGF)
Histology 2nd Semester D.A.T.W
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Tubular System o Tubular segments of nephron are named according to their course (convoluted or straight), location (proximal or distal) and wall thickness (thin or narvebraten) o Chronological order from bowman´s capsule to bladder o Proximal convoluted tube Originates from urinary pole follows tortuous path until it enters the medullary ray from here it continues as straight tubule Lined by single layer of cuboidal cells characteristics: Brush border (we learned that only columnar cells can exert surface modifications BUT we were misleaded) Tight junctions inbetween the cells “polarizes” the cells in that they have an apical and basolateral membrane which are permeable for different substances Plicae folds in the lateral membranes of the cells allow surface distension in case of volume rise in the exctracellular fluid (ECF) Basal striations due to elongated mitochondria which are vertically oriented to basal surface are necessary for ATP production which is needed for all the active transport processes across the cell membrane Transporters: • Na+K+ ATPase reabsorption of Na+ which creates osmotic gradient necessary for the reabsorption of water • Aquaporin I molecular water channel water diffuses down the osmotic gradient through these channels • Several other cotransporters (look in your physio notes) • Proteins and large peptides are endocytosed in the proximal tubule o Thick descending limb of Henle´s loop Descends into the medulla Cells are shorter and have the same characteristics as the cells of the proximal convoluted tube BUT not so well expressed o Thin descending limb of Henle´s loop The length of the thin segments depends on the type of nephron (look above) Continuation of thick descending limb Contains various cell types (check p.663 in ross book ed. 5) but we simply memorize it is lined by simple squamous epithelium The thin descending limb is permeable to water and takes part in the countercurrent balance (look in your physio notes) It has low permeability for solutes o Thin ascending limb of Henle`s loop Is the continuation of the thin descending limb AFTER the hairpin loop Is highly permeable to solutes allows passive diffusion of NaCl into the interstitium No active transport takes place Impermeable to water part of countercurrent balance system
Histology 2nd Semester D.A.T.W
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Thick ascending limb of Henle´s loop Ascends through the medulla and enters cortex in medullary ray to reach its renal corpuscle here it leaves the medullary ray and makes contact with the vascular pole of the renal corpuscle Juxtaglomerular apparatus • at this point the epithelial cells of the tubule form the macula densa cells contain chemoreceptors which monitor ion concentration in the tubular fluid • If necessary the juxtaglomerular cells activate the renin-angiotensin-aldosterone system (physio notes important to know!!) Low permeability for water Transporters • Na+/K+/2Cl- Cotransporter in apical membrane • transports ions from the lumen into the interstitium Simple cuboidal epithelium • cells are big and nucleus sometimes is more located in the apical part • extensive basolateral plications • basal folds • low brush border Distal convoluted tubule Less tortuous than the proximal convoluted tubule thats why in the slides you see way more proximal tubule profiles than distal tubules Transporters reabsorb Na+ and secrete K+, NH3; ADH regulated concentrations of Aquaporin 2 (physiology) Collecting tubules + Collecting ducts Simple cuboidal epithelium (in the beginning it can be squamous) Boundaries between the cells can be seen clearly (which makes them distinguishable from proximal convoluted tubules) Cells • Light cells pale staining cells with true basal infoldings and a single kinocilium (monocilium) + relatively short microvilli • Dark cells also called intercalated cells, have many mitochondria and their cytoplasm appears denser o Do not contain basal infoldings but have basally located interdigitations with neighboring cells o Numerous vesicles are present o Are able to secrete H+ (alpha IC) or HCO3- (beta IC) dependent on the needs of the kidneys • The cells become gradually taller as the ducts approach the renal papilla and the number of dark cells decreases until none are present in the ducts close to the papilla
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Histology 2nd Semester D.A.T.W
Question 43 – Kidney HE
Part I – Histological appearance • • • •
(1) Capsule of dense C.T. (2) Medullary ray (or pars radiata) in longitudinal section (3) Interlobular artery in cross section (4) cross sectional part of cortical lobule
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Histology 2nd Semester D.A.T.W
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Kidney 2nd picture • • • • •
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(1) Medullary ray with longitudinal sections through the renal tubule (2) thick descending limb of Henle`s loop (3) thick ascending limb of Henle´s loop (4) Interlobular arteries (5) Cortical lobule marked by green line (area inbetween to interlobular arteries with a medullary ray in its midline) (6) interlobular vein (beneath the green line) (7) collecting duct (8) proximal tubule (makes up majority of structures in the picture) (9) (white marking) glomerulus or malphigian corpuscle (10) bowman´s space (11) distal tubule
Histology 2nd Semester D.A.T.W
197 Kidney 3rd picture • • • • • • • • •
(1) Proximal tubule (2) Distal tubule (3) Glomerulus (malphigian corpuscle) (4) bowman´s space (5) Parietal wall (simple squamous epithelium) (6) [blue] Visceral wall (6) [green] podocyte (7) Endothelial cell also mesangial cells are present but not well distinguishable
Histology 2nd Semester D.A.T.W Kidney 4th picture • • • • •
(1) Interlobular artery (2) Interlobular vein (3) Malphigian corpuscles (4) Distal convoluted tubules (5) ½ cortical lobule
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Histology 2nd Semester D.A.T.W
Kidney 5th picture • •
(1) Minor calix (2) Urothelium This picture was made from the border of the slide showing the minor calix which is lined by urothelium
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Histology 2nd Semester D.A.T.W Kidney 6th picture • • • • •
(1) Distal tubule (2) Collecting duct (3) Proximal tubule (4) Bowman´s space (5) Malphigian corpuscle
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