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Digestive gland Dr. Maria Zahiri
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Digestive Glands Digestive glands are consist of: Salivary glands
Pancreas Liver Gall bladder Dr. Maria Zahiri
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Salivary Glands minor (Accessory) salivary glands
pairs of major (main) salivary glands Three pairs of major salivary glands are: Submandibular glands Sublingual glands Parotid glands Dr. Maria Zahiri
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Salivary Glands capsule and septa
that organize the glands into lobes and lobules Dr. Maria Zahiri
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Salivary Gland Cells Serous cells produce proteins pyramidal cells
spherical euchromatic nucleus Cytoplasm is basophilic (RER, Golgi apparatus) Apically located granules that are usually eosinophilic Many basal mitochondria Dr. Maria Zahiri
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heterochromatic basal flattened nucleus Apical cytoplasm is pale
Mucous cells cuboidal or pyramidal heterochromatic basal flattened nucleus Apical cytoplasm is pale They have less RER, fewer mitochondria but greater GA Dr. Maria Zahiri
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MIXED GLAND Organized as acinus or demilune that secrete proteins, polysaccharides and ptyalin Dr. Maria Zahiri
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Ducts system : Intercalated ducts diameter: thinnest
wall: simple low cuboidal epithelium
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Striated duct (secretory duct)
wall: simple columnar epithelium; the nucleus is near the cell apex cytoplasm is acidpphilic; has basal striations EM: the basal striations created by membrane infolding and mitochondia reabsorbing sodium and excreting potassium; transport water and ions
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Intercalated ducts and striated ducts
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intralobular ducts: Striated ducts join each other and forming intralobular ducts that are invested by more CT elements Dr. Maria Zahiri
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interlobular ducts (excretory ducts):
intralobular ducts join each other and forming larger caliber ducts known as interlobular ducts (excretory ducts) Excretory duct have large diameter, large lumen, cuboidal or columnar cells, located outside of lobules Dr. Maria Zahiri
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Myoepithelial cells (Basket cells)
have large processes which form desmosomal contact with acini and ducts cells, Their processes are rich in actin and myosin have a common basal lamina with acinar cells They attach to basal lamina by hemidesmosome Dr. Maria Zahiri
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Parotid Gland The largest salivary gland produce 30% of saliva
capsule & many septa divided the glands into lobes and lobules serous cells After 40 year of age adipose tissue invaded the gland Dr. Maria Zahiri
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Submandibular Gland produce 60% of saliva
Mucous and serous acini; mucous acini with limited number of serous demilunes About 80% of cells are serous (basophilic) Dr. Maria Zahiri
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Sublingual Gland It is very small that produce 5% of total saliva
Mostly mucous cells in acini with some serous demilunes Produce mix saliva but mostly mucous saliva Dr. Maria Zahiri
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Saliva Saliva includes water, enzymes, IgA, mucous, ions
Moisten and lubricate food for swallowing Enzymes like amylase and lipase to begin digestion Saliva has protective effect on oral cavity tissues Participate in taste sensation IgA, lactoferrin, lysozyme have different role against antigens and microorganisms Dr. Maria Zahiri
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Pancreas is a mixed exocrine and endocrine gland
Thin capsule with septa between lobules Exocrine part organized similar to parotid gland Endocrine part are islets of Langerhans scattered among the excretory units Centroacinar cells occupy the lumen of the acini, these cells are beginning of the duct system Centroacinar cells are pale, low cuboidal intercalated ducts, Intralobular ducts, and interlobular ducts no striated duct Dr. Maria Zahiri
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The functions of exocrine portion
Secret abundant trypsinogen, chymotrypsinogen, amylase, lipase, sodium bicarbonate and trypsin inhibitor
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Endocrine portion (pancreatic islet):
rounded clusters of cells embedded within exocrine pancreatic tissue are divided into three kinds of cells: A, B, and D cells fenestrated capillaries are among the cells
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Pancreas (show pancreatic islet)
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Endocrine portion Size number Distribution Function A cells large 20%
Peripheral glucagon B cells small 75% center insulin D cells 5% Among A and B cells somatostatin PP cells: pancreatic polypeptide G cells: gastrin Other cells
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A cells B cells D cells
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Liver largest gland in the body (1500 gr)
has endocrine and exocrine functions Receives portal blood from intestine via portal vein and oxygenated blood from hepatic arteries Dr. Maria Zahiri
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Liver Hepatic plates Sinusoid Central vein Liver lobule
Interlobular arteries Interlobular veins Interlobular bile ducts Portal area
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classical lobule blood flow from periphery to center of lobule Bile flow in opposite direction in small intercellular spaces known as bile canaliculi
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Portal lobule Is a triangular region that portal area is located in its center and central veins form apices of the triangle
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Hepatic acinus (acinus of Rappaport)
is diamond-shaped, a distributing artery located in center of acinus, three regions of parenchyma surrounding the artery(zone I, II, III)
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The space between the anastomosing plates of hepatocytes are occupied by hepatic sinusoids
Sinosuidal lining cells are fenestrated are not in contact with each other They prevent direct contact between blood and hepatocytes Resident macrophages known as Kupffer cells associated with lining cells
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The space that separates sinusoidal lining cells from hepatocytes is called perisinusoidal space (space of Disse) Microvilli of hepatocytes occupy much of the space Type III collagen that is present in space support lining cells(no basal lamina)
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Cells Fat storing cells ( known as Ito cells or Stellate cells) may present in Disse space and store vitamin A Pit cells which are natural killer cells also may be seen in space of Disse Hepatocytes are polygonal forming anastomosing plates of one to two thickness cells, eosinophilic with 1 or 2 spherical nuclei,
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Cells In lateral domain bile canaliculi form between two cells, microvilli, Na-K ATPase and gap junctions are common characteristics of lateral domain Bile canaliculi between hepatocytes leading to hepatic ducts with simple cuboidal epithelium
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Hepatic cords
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Liver Sinunosoidal domains of cell membrane have many microvilli protrude to perisinusoidal space (of Disse), endocrine secretion of hepatocytes release here Bile secreted from hepatocytes into bile canaliculi contains water, ions, bile salts and acids, phospholipids, cholesterol, & bilirubin
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Liver Functions Glycogen storage Lipid metabolism
Vitamin storage (A, D, B12 ) Bile production (Bile acids solubilize lipids and aid digestion) Detoxification of drugs and toxins in SER Synthesis of plasma proteins (albumin) Metabolism of lipid, carbohydrate, proteins Erythrocyte breakdown (Bilirubin formed in breakdown of RBC) Complex IgA with secretory component
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Mitochondria provide the energy for the hepatocytes Rough endoplasmic reticulum synthesize some plasma proteins Golgi apparatus participate in the formation of bile and lipoprotein
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Smooth endoplasmic reticulum
synthesize bile, triglyceride and LDL metabolism of the lipid, hormones inactivate steroid hormone biotransformation of some materials detoxification of Toxic substances
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Lysosomes actively participate the metabolism of hepatocyte and renewal of organelles play a role in metabolism storage of iron
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Microbodies detoxification: catalase and peroxidase; reduce the hydrogen peroxide into H2O Inclusions include glycogen, lipid droplets, pigment etc; These contents vary according to physiologic state of human body
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Bile canaliculi between two adjacent hepatocytes
the membrane of hepatocyte projects to the lumen, forming many microvilli the cell membranes near the bile canaliculi are firmly bound by junctional complexes
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Liver sinusoid spaces between the hepatic plates irregular in shape
composed of only one discontinuous layer of fenestrated endothelial cells, no diaphragm, no basement membrane Kupffer cells are located within the sinusoid cavities
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Blood circulation: (functional vessel) (nutrient vessel) portal V.
interlobular V. (functional vessel) sinusoids central V. hepatic A. interlobular A. sublobular V. (nutrient vessel) hepatic V.
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Discharge way of bile: Bile canaliculi Hering’s canals
Interlobular bile ducts Gallbladder Hepatic duct Common bile duct Cystic duct duodenum
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Gallbladder Simple columnar Epi. , no Goblet cells
Laminar propria: C.T. mucosa muscle layer: composed of an inner circular, an outer longitudinal layers of smooth muscle adventitia: most are fibrosa, some are serosa
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Gallbladder
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Stores and concentrates 30-50 ml bile
Cholecystokinin and acetylcholine stimulates contraction to force bile into small intestine
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