& SPLEEN

Color index: Slides.. Important ..Notes ..Extra.. Objectives: By the end of this lecture, the student should be able to describe: 1. The histological structure of liver with special emphasis on: . Classical hepatic (liver) lobule. . . . Portal tract (portal area). . Hepatic (liver) blood sinusoids. . Space of Disse (perisinusoidal space of Disse) . Bile canalculi. 2. The histological structure of spleen with special emphasis on: . White pulp. . Red Pulp. LIVER 1-Stroma; 2-Parenchyma; mainly C.T, but not in humans. Classical liver (hepatic) lobules It is formed of a polygonal mass of a- Capsule: Glisson’s Capsule. liver tissue, bounded by b- Septa (absent in human) interlobular septa with portal areas & Portal areas (Portal tracts) at the periphery & central Portal area: surrounded by (centrolobular) vein in the center. other structures. Central vein: surrounded by c- Network of reticular fibers. hepatocytes LIVER Contents of the Classic Liver Lobule: Borders of the Classical Liver Lobule the rows of hepatocytes should be next to each other; 1- Septa: C.T. septa (e.g. in pigs). remember canaliculi 2- Portal areas (Portal tracts): 1- Anastomosing plates of hepatocytes. Are located in the corners of the classical hepatic 2- Liver blood sinusoids (hepatic blood lobule (usually 3 in No.). sinusoids): between the plates. Contents of portal area: 3- Spaces of Disse (perisinusoidal spaces of a- C.T. b- Bile ducts (). Disse) between the hepatocytes and sinusoids c- Venule (Branch of portal vein). 4- Central vein. d- Arteriole (Branch of hepatic artery). 5- Bile canaliculi. Hepatic artery: surrounded by smooth muscles while the is not. Hepatocytes (LM) IMPORTANT: *the hepatocytes have two surfaces: one facing another , the other facing the sinusoids *Are grouped in interconnected plates. *Liver sinusoids are located in the spaces between these plates. Shape: polyhedral Nucleus: 1 or 2, vesicular with prominent nucleoli. Cytoplasm: acidophilic. The area facing the hepatocyte has tight Organelles: junctions which increase surface area and 1- Mitochondria: ++++ desmosomes to fix these junctions in 2- ER (sER & rER): abundant. place. 3- Golgi complex. The area facing the sinusoids have microvilli for absorption and secretion of 4- Lysosomes. metabolites to/from the hepatocytes, but 5- Peroxisomes. these microvilli do not reach the blood. Inclusions (Deposits): 1- Glycogen 2- Lipid (few droplets). 3- Lipofuscin (old age) Space of Disse Liver Blood Sinusoids (Perisinusoidal Space)

(1) Endothelial Cells: Contents: Fenestrated & discontinuous → free passage of 1- -storing cells (Ito cells) (Hepatic stellate cells): plasma. contain vitamin A-rich lipid. Basal lamina is absent. form reticulin. (2) Kupffer Cells: produce lysosomes 2- Reticular fibers: formed by reticulin (type III collagen). Normally present in small Are macrophages. amounts, an increase = liver fibrosis Are found on the luminal surface of the endothelial 3- Plasma of blood. NOT cells! , cells found in the cells. blood are NOT filtered ! Function: phagocytosis. 4- Microvilli of hepatocytes. Spleen

Stroma of Spleen Parenchyma of Spleen 1- Capsule: A. White pulp.  Is covered by visceral layer of B. Red pulp (around white pulp) peritoneum; mesothelium.  Is formed of fibromuscular C.T. N.B. to differentiate the spleen from (Dense fibrous C.T. + smooth the lymph nodes muscle cells). • No cortex, Muscles for contraction in case of loss of blood • No medulla, 2- Trabeculae: • No afferent lymphatic vessel.  Are irregular, incomplete, divide the spleen into intercommunicating compartments (lobules). 3- Reticular C.T. Parenchyma of Spleen Cells of parenchyma of (A) White Pulp (B) Red pulp Spleen 1. Periarterial lymphatic 1. Splenic (pulp) cords: 1. Lymphocytes B + T sheaths (PALS): Extravasated blood cells, plasma 2. Plasma cells. housing T lymphocytes. cells, macrophages & reticular cells 3. Macrophages for the filtration of blood 2. Lymphoid follicles (with and fibers. 4. Blood elements (RBCs, leucocytes germinal centers): 2. Splenic blood sinusoids: and blood platelets). housing B lymphocytes. Surrounded by the pulp Are lined with elongated fusiform Splenic Microcirculation N.B. Both 1&2 have the endothelial cells with large IMPORTANT: The PALS (blue area surrounding acentrically located central intercellular spaces & supported the artery) have T-Cells PURELY artery (central arteriole) by discontinuous, circular (follicular arteriole). basement membrane. MCQs 1\ Glisson’s Capsules are found in: 5\Fat-storing cells in liver are called: A-parenchyma. a.Endothelial cells. B-stroma. b.kupffer cells C-Both A&B. c.Ito cells.

2\ the shape of hepatocyte is: 6\ Which of the following is part of the a.polyhedral. spleen’s Parenchyma? b.spherical. a. Cortex. c.spiral. b. Red Pulp. c. Medulla. 3\ What is the space between the liver sinusoids 7\one of The differences between and the hepatocytes called? the spleen and the lymph nodes is: a. Space of Disse. a.spleen has no white pulp. b. Space of Mall. b.Spleen has cortex. c. Vacuole. c.Spleen has No medulla. 4\what is the function of Kupffer Cells:

a.Regeneration.

c -

7 b.Phagocytosis.

b -

6 c.nutrtion.

c - 5

b - 4

a - 3

a - 2

b - 1 Thank you & good luck - Histology team Done by:  Amal AlQarni  Do’aa AlWalid Team leaders:  Heba AlNasser  Rana Barasain  Shahad AlAnzan  Faisal Alrabaii  We’am Babaier

References:  Females’ and Males’ slides.  Doctors’ notes