Digestive gland

Dr. Zahiri

In the name of God

Dr. Maria Zahiri

Digestive GlandsDigestive glands are consist of:

Salivary glands

Pancreas

Liver

Gall bladder

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Salivary Glands

• minor (Accessory) salivary glands • pairs of major (main) salivary glands

Three pairs of major salivary glands are:Submandibular glandsSublingual glandsParotid glands

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Salivary Glands

capsule and septa that organize the glands into lobes and lobules

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Dr. Maria ZahiriSalivary 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

Dr. Maria Zahiri

Mucous cells

cuboidal or pyramidalheterochromatic basal flattened nucleusApical cytoplasm is paleThey have less RER, fewer mitochondria but greater GA

Dr. Maria Zahiri

Dr. Maria Zahiri

• Organized as acinus or demilune that secrete proteins, polysaccharides and ptyalin

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Ducts system

Intercalated duct smallest branches short, cuboidal or squamous cells and myoepithelial cells

Striated duct Larger diameter cuboidal to low columnar cells which are eosinophilic, and secrete fluid

and ions basolateral membrane folded with Na – ATPase pump, elongated

mitochondria

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intralobular ducts:Striated ducts join each other and forming intralobular ducts that are

invested by more CT elements

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

Dr. Maria Zahiri

Dr. Maria Zahiri

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 ZahiriParotid 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 adiposetissue invaded the gland

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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)

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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 ZahiriSaliva

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 tissuesParticipate in taste sensation

IgA, lactoferrin, lysozyme have different role against antigens and microorganisms

Dr. Maria ZahiriPancreas 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, intercalated ducts, Intralobular ducts, and interlobular ducts

Dr. Maria Zahiri

Dr. Maria Zahiri

Dr. Maria Zahiri

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

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Liver hepatocytes Liver has a lobular organization Classical lobule:

hepatocytes arranged as an hexagon

Portal area (triad): is where three classical lobules are in contact with each other, more

CT elements present, houses branches of hepatic artery, tributaries of portal vein, interlobular bile ducts, and lymph vessels

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classical lobule blood flow from periphery to center of lobuleBile flow in opposite direction in small intercellular spaces known as bile canaliculi

Portal lobuleIs a triangular region that portal area is located in its center and central veins form apices of the triangle

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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Liver 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

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)

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,

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

Cells

LiverSinunosoidal 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

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

Gall Bladder

Mucosa : simple columnar epithelium Epithelial layer is highly folded lamina propria: loose CT

Smooth muscle layer is composed of thin obliquely oriented fibers with perimuscular connective tissue

Serosal and adventitial membrane Stores and concentrates 30-50 ml bile Cholecystokinin and acetylcholine stimulates contraction to force

bile into small intestine

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