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Digestive Sys tem Digestive Glan ds

Digestive System Digestive Glands

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Digestive System Digestive Glands. Components of Digestive Glands. Salivary glands Pancreas Liver. Small digestive glands: found in the wall of digestive tract Accessory glands (large digestive glands). General structure of Digestive Glands. Parenchyma: (functional portion of an organ ) - PowerPoint PPT Presentation

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Page 1: Digestive System Digestive Glands

Digestive System

Digestive Glands

Page 2: Digestive System Digestive Glands

Components of Digestive Glands

• Small digestive glands:

found in the wall of digestive tract

• Accessory glands (large digestive glands)

Salivary glands

Pancreas

Liver

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General structure of Digestive Glands

• Parenchyma:(functional portion of an organ)

acini/gland cells

ducts

• Stroma: (non-functional portion of an organ)

capsule

CT inside the organ

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Salivary Glands

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Salivary GlandsGeneral structure of the large salivary glands

Parenchyma

acinus

duct

Serous acinus

Mucous acinus

Seromucous/mixed acinus

Intercalated duct

Striated/secretory duct

Interlobular duct

Excretory duct

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Model (structure of the large salivary glands)

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Salivary GlandsStructural characteristic of gland cell:

Serous acinus: comprised by serous cells.

﹡zymogen granules in apical cytoplasm.

Mucous acinus: comprised by mucous cells.

﹡mucinogen granules in cytoplasm.

Seromucous acinus: comprised by both cells.

/mixed acinus demilume ﹡

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Serous acinus ﹡zymogen granules in apical cytoplasm.

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Serous cell:

Basal lamina(bl);

Connective tissue (ct);

Desmosome (d);

Endothelium (en);

Golgi comples (g);

Intercellular space (is);

Lumen (l);

Microvilli (mi);

Mitochondria (m);

Nucleus (nu);

RER (re);

Secretion granule (sg).

10.000x

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Mucous acinus: ﹡mucinogen granules in cytoplasm.

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Detail of mucous cells:

mucous cell (sc);

Golgi complex (gc);

Intercellular space (is);

Secretion granule (sg);

Lumen (l);

Nucleus (n);

RER (re).

10000x.

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Seromucous acinus

/mixed acinus

demilume

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Salivary GlandsAcinus

Duct

Intercalated duct:

Simple squamous/cuboidal epith.

Striated/secretory ducts:

simple tall columnar epith.

Interlobular duct:

pseudostratified columnar epith.

Excretory ducts:

stratified squamous epith.

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Salivary Glands

Intercalated duct:

Simple squamous

or cuboidal epith.

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Salivary GlandsIntercalated duct: simple squamous or cuboidal epith.

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Detail of intercalated duct cell

Basal laminar (bl);

Desmosome (d);

Nerve fibers (nf);

Golgi complex (g);

Intercellular space (is);

Mitochondria (m);

Nucleus (nu);

RER (re).

13.000x

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Salivary Glands

Striated/secretory duct: simple tall columnar epith.

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Salivary GlandsStriated /secretory duct

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Salivary Glands

Striated/secretory duct

The secretory ducts, which are continuous with intercalated ducts, are wider and lined with a simple columnar epithelium. As the secretion from the acini passed through the secretory ducts, the epithlium can re-absorb sodium (Na+) and water from the lumen to the interstitium and transport potassium (K+) into the saliva, thus changing the consistency of the saliva. The secretory ducts drain into interlobar ducts which run between lobules.

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Salivary GlandsInterlobular duct: excretory duct:

Pseudostratified columnar epith. Stratified squamous epith.

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Salivary glands

Include

﹡Parotid G.

﹡Submandibular G.

﹡Sublingual G.

Function:

﹡Moistening food.

﹡Carbohydrate digestion.

﹡Secrete IgA.

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Pancreas

The pancreas is a lobular organ.

The pancreas has both exocrine functions (releases digestive enzyme secretions into the intestines) and endocrine functions (releases hormones into the blood).

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Pancreas

Parenchyma

exocrine gland endocrine gland

produces produces

pancreatic juice hormones

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Parenchyma

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Parenchyma

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Pancreas

Exocrine pancreas

Acini Ducts

Wholly consists of serous acini.

Small centroacinar cells in the lumen

Intercalated ducts

Interlobular ducts

Main pancreatic ducts

Major duodenal papilla

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Exocrine Pancreas

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Exocrine Pancreas

It releases the pancreatic juice.

Pancreatic juice contain many kinds of enzyme:

﹡amylase: hydrolyses starch & glycogen.

﹡lipase: hydrolyzes triglycerides

into fatty acids and mono-glycerides

﹡cholesterol esterase: breaks down

﹡trypsin and chymotrypsin:

hydrolyze proteins.

﹡ribonuclease & deoxyribonuclease:

split nucleic acids.

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PancreasEndocrine pancreas

﹡Islets of Langerhans

Scatter throughout the exocrine pancreas.

﹡Three types of cells:

A-cells (20%) glucagon (glycogen→ glucose)

B-cells (75%) insulin

D-cells (5%) somatostatin

﹡Capillaries: each islet is richly supplied with blood vessels.

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PancreasEndocrine pancreas

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GlucagonPurpose: Assist insulin in regulating blood glucose (sugar) in the normal rangeAction:    Forces many cells of the body to release (or produce) glucose (increasing blood sugar)Secreted in response to:     Low blood glucoseSecretion inhibited by:     High blood glucoseDisease due to deficient action: Some times nothing, sometimes hypoglycemiaDisease due to excess action: HyperglycemiaTumor called: Glucagonoma

InsulinPurpose: Regulate blood glucose (sugar) in the normal range Action: Forces many cells of the body to absorb and use glucose thereby decreasing blood sugar levelsSecreted in response to: High blood glucoseSecretion inhibited by: Low blood glucoseDisease due to deficient action: Diabetes   Disease due to excess action: HypoglycemiaTumor called: Insulinoma. 

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Liver

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Liver

General Introduction

﹡The largest gland (--2% of body weight in adult).

﹡respectively receives both venous & arterial blood through the portal v. (--75%) & hepatic A (--25%).

﹡CT of capsule extended into the parenchyma, forming “classical” liver lobules.

﹡Functions as an exocrine gland (secreting bile) and other very important roles.

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Liver

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LiverStructrues of Liver lobule

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LiverStructures of Liver lobule

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Model of Liver Lobule

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LiverStructures of Liver lobule

﹡six-sided prism

with a central V. at its center.

﹡sheets of hepatocytes (or hepatic plates)

extend radially from the central V.

﹡sinusoids between hepatic plates.

Portal triads (or portal area):

In the corner of lobules.

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Structures of Liver lobule

Liver

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Portal Triads (or Portal Area)

Liver

﹡Definition:

The area of CT found in the angles where adjacent hepatic lobules meet.

﹡Components:

CT.+portal triad

interlobular A

interlobular V

interlobular bile duct

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Portal Triads (or Portal Area)

Liver

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Portal Triads (or Portal Area)

Liver

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Sinusoids

Liver

﹡Dilated anastomosing venules between the hepatic plates.

﹡Blood pathway: periphery→central V.

﹡Kupffer cells line in the wall of sinusoids.

﹡EM (endothelium of sinusoid)

significant gaps;

numerous fenestration;

incomplete basal lamina.

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Sinusoids

Liver

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TEM

Sinusoids

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Sinusoids

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HepatocyteLiver

﹡typically large polyhedral cells with large round centrally located nucleus.

﹡abundance of organelles relates to its functions:

Mitochondria: provide energy

RER: protein synthesis

SER: bile formation/ metabolism of lipids and hormones/detoxification.

Lysosome: defence

Microbody: detoxification

Inclusions: glcogen particles, lipid droplets and pigments.

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Hepatocyte

Liver

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Functions of Hepatocyte

Liver

﹡Produce bile.

﹡Degrade glycogen to glucose under regulation of hormones.

﹡Involve the blood lipid metabolism.

﹡Synthesize the blood plasma proteins: albumin;fibrinogen, and so on

﹡Detoxification

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Bile Canaliculus

Liver

Definition:

the tubular space limited by plasma membrane of two adjacent hepatocytes.

Structure:

LM: network-like structures are seen by silver impregnation.

EM: plasma membrane of adjacent ﹡hepatocytes

forms the wall of bile canaliculi.

﹡tight junctions form seals.

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Bile Canaliculus

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Bile Canaliculus

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Perisinusoidal space (Disse’s Spaces)

Liver

A space between endothelium & hepatocyte.

﹡Be visible under EM.

﹡Occupy by numerous microvilli of hepatocytes.

﹡Fill with blood plasma.

﹡have fat-storing cells (storing fat & vitamin A)

﹡A site for substance exchange

Between the blood & the hepatocytes.

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Perisinusoidal space (Disse’s Space)

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Perisinusoidal space (Disse’s Space)

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Sinusoids

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LiverThree functional surface on the surface of hepatocyte

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LiverBlood Supply

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Liver

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Liver

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Liver

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Liver

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