•12/2/2010

•1

Digestive SystemGlands

Zulham, Radita, Feby

Department of Histology

Faculty of Medicine USU

histologi.usu.ac.id

histo_fkusu@yahoo.com

SALIVARY GLANDS• There are 3 pairs of major salivary glands:

– Parotid (25%)

– Submandibular (70%)

– Sublingual

• Saliva is a hypotonic watery secretion containing mucus, enzymes, antibodies and inorganics ions

• Two types of secretory cells are found in the salivary glands : serous cells and mucous cells

•12/2/2010

•2

Parotid gland

• The largest salivary gland

• Branched tubuloalveolar gland

• Surrounded by a connective tissue capsule with septa

• In stroma : adipose cells

• Formed by acini containing exclusively serous cells with a basal nucleus and an apical cytoplasm with secretory granules

• Has the longest intercalated ducts

•12/2/2010

•3

Submandibular Gland

• Mixed serous and mucous tubuloacinar glands.

• Often found in the form of mixed seromucous secretory

• The serous cells are predominant component

• Mucous cell-containing acini are capped by serous demilunes

•12/2/2010

•4

Sublingual Gland• Does not have a defined capsule

• Mixed serous and mucous tubuloacinar glands in which mucous cells predominate

• The intercalated and striated ducts are poorly developed

•12/2/2010

•5

Liver

• Has both exocrine (bile) and endocrine functions (by hepatocytes)

• Is enveloped by peritoneum

– Simple squamous epithelium

– Dense irregular CT capsule (Glisson’s capsule)

• Hepatocytes are arranged in hexagon-shaped lobules (classical lobules)

– In human, boundaries of the classical lobules can only be approximated

– Longitudinal axis is occupied by central vein

– Portal areas (triads): where 3 classical lobules are in contact each other

• CT elements are increased; hepatic artery, portal vein; interlobular bile ducts; lymph vessels

Classic Lobules (pigs)

•12/2/2010

•6

3 Concepts of Liver lobules• Classical liver lobules

– Concept: Blood flows from the periphery to the center of the lobule (central vein)

– Bile enters into bile canaliculi and flows to the periphery of the lobule to the interlobular bile ducts of the portal areas

• Portal lobules– Concept: exocrine secretion (bile) flows to central lumen of acinus

– Triangular region whose center is the portal area and whose periphery is bounded by imaginary straight line connecting the three surrounding central veins that form the three apices of the triangle

• Hepatic acinus (acinus of Rappaport)– Concept: blood flow from distributing arterioles → on the order in

which hepatocytes degenerate subsequent to toxic or hypoxic insults

– 3 concentric regions of hepatic parenchyma surrounding a distributing artery in the center.

3 Concepts of Liver Lobules

•12/2/2010

•7

Hepatic Sinusoids andPerisinusoidal Space of Disse

• Hepatic sinusoids: the space between the plates of hepatocytes

– Sinusoidal lining cells (endothel)

– Fenestrated 0.5 µm

– Macrophage → Kupfer Cells

• Endothels are separated from hepatocytes by perisinusoidal space (Space of Disse)

– Collagen III; No basal lamina

– Nonmyelinated nerve fibers

– Fat storing cells (Ito Cells/Stellate cells)

– Pit cells → NK cells

•12/2/2010

•8

•12/2/2010

•9

Kupfer Cells

•Space of Disse

•12/2/2010

•10

Hepatic Duct• Bile canaliculi → labyrinthine tunnels →

cholangioles → canals of Hering → interlobular bile ducts → right and left hepatic duct

• Cholangioles

– At the periphery of classic lobules

– Short tubules composed of a combination of hepatocytes, low cuboidal cells, and occasional oval cells

• Canals of Hering

– Slender branches of interlobular bile ducts

– Composed of low cuboidal cells and some ovoid cells

• Cuboidal cells secrete a bicarbonate-rich fluid under influenced of hormon secretin of DNES cells

Hepatocytes

• 2 domains: lateral and sinusoidal

• Lateral domains

– Form bile canaliculi

– Fascia occludentes prevent leakage of bile from bile canaliculi

– Short, blunt microvili project into bile canaliculi (exocrine secretion)

– High levels of Na-K ATPase and adenylate cyclase

– Isolated gap junctions

• Sinusoidal domains

– Microvili projects into space of Disse

– Endocrine secretion

•12/2/2010

•11

Bile Canaliculi

•12/2/2010

•12

Gall Bladder

• Mucosa

– Empty gallbladder is highly folded into tall, parallel ridges; bile distended gallbladder reduces the plications to a few short folds → smooth mucosa

– Simple columnar epithelium

• Clear cells

• Brush cells

– Lamina propria is a vascularized loose CT

• Simple tubuloalveolar glands

• Smooth muscles are oriented oblique and longitudinal

• Adventitia

– Glisson’s capsule of Liver

– peritoneum

•12/2/2010

•13

Histophysiology

• Store, concentrate, and release bile

• Epithelium

– Luminal surface display short microvili

coated by a thin layer of glycocalyx

– Supranuclear: secretory granules containing

mucinogen

– Basal region is rich in mitochondria

•12/2/2010

•14

Pancreas

• Produced exocrine and endocrine secretions

• CT capsule forms septa → sudivide the gland into lobules

Exocrine Pancreas• Tubuloacinar gland

• 40 – 50 acinar cells form a round to oval acinus

• 3 – 4 centroaciner cells occupied acinar lumen → beginning of the duct system

• Acinar cell

– Truncated pyramid; round nucleus; basally located; basophilic cytoplasm

– Apex, facing the lumen, is filled with zymogen granules. Number of secretory granules diminished after meal.

– Basal cell membranes have receptors for cholecystokinin and acethylcholine

• The Golgi complex varies in size in inverse relation to the zymogen granule concentration

– Smaller when zymogen granules are numerous

– Larger after the granules release their content

• Zymogen granules may release their contents individually or several granules may fuse each other, forming a channel to the lumen

•12/2/2010

•15

•12/2/2010

•16

Exocrine Pancreas

• Duct System

• Centroacinar cells of terminus intercalated duct → intralobular ducts → interlobular ducts → main pancreatic duct → common bile duct → papilla of Vater

• Centroacinar cells: pale, simple low cuboidal ep

•12/2/2010

•17

Endocrine Pancreas

• Islet of Langerhans

– Richly vascularized spherical conglomeration of + 300 cells

• Cells: β, α, δ, PP, G

– Cannot be differentiated by routine examination → IHC, EM

• Each islet is surrounded by reticular fibers, which also enter the islet to encircle the capillaries that pervade it.

•12/2/2010

•18

Thank You