Digestive SystemDigestive System

GlandsGlands

Zukesti Effendi

ZulhamDepartment of Histology

Faculty of Medicine USU

histologi.usu.ac.id

GlandsGlands

• Salivary Glands

• Liver

• Gall Bladder• Gall Bladder

• Pancreas

Salivary GlandsSalivary Glands

• Salivary glands

– Minor

– Major– Major

• Sublingual glands

• Submandibular glands

• Parotid glans

• Regions of salivary glands

– Secretory portions

– Duct portions

Secretory PortionsSecretory Portions

• Serous cells– Truncated pyramids; single, round, basally located nuclei– Well developed RER, Golgi complex, basal mitochondria, →

abundant apically situated secretory granules rich in ptyalin (amilase)– Basal aspects o/t lateral cell membranes form tight junctions– Intercellular canaliculi– Interdigitation process– Interdigitation process

• Mucous cells– Truncated pyramids; single, flattened, basally located nuclei– Less extensive RER, fewer mitochondria but greater Golgi

complex → >> carbohydrate component, abundant apically situated secretory granules

• Myoepithelial cells (basket cells)– Share the basal laminae o/t acinar cells– Envelop acinus and intercalated ducts– Cytoplasmic process are rich in actin and myosin → resemble smooth

muscle → contract → facilitating release o/t secretory product

Mucous Cell

Serous Cell

Duct PortionsDuct Portions

• Secretory potions → intercalated ducts → striated ducts → intralobular ducts → interlobular ducts → intralobar ducts → interlobar ducts → terminal (principal) duct

• Intercalated ducts: simple cuboidal ep + myoepithelial cell• Striated duct:

– simple cuboidal to low columnar ep– Basolateral membrane are highly folded, subdividing into longitudinal – Basolateral membrane are highly folded, subdividing into longitudinal

compartment that occupied by elongated mitochondria– Na – ATPase pumps Na out o/t cell into CT → conserving sodium

• Salivon– functional unit of a salivary gland– Acinus + intercalated duct + striated duct

• Secretory activity is stimulated via parasympathetic and sympathetic innervation

Sublingual glandsSublingual glands

• The gland is composed of mucous tubular secretory units capped by serous serous demilunes.

• Produced mixed, but mostly mucous, salivamucous, saliva

• EM: apical accumulations of secretory vesicles

• Scant CT, and its duct system doesn’t form terminal duct, Instead, several ducts open into the floor o/t mouth and into the duct of the submandibular gland

• A. EM of mucous acini of the Sublingual Gland. C, capillary; I, Intercalated Duct; L, lumen of Acinus; arrows, Myoepithelial Cell. 1,850 X

• Figure B. Mixed acini of same Sublingual Gland shown in Figure A. C, capillary; M, Figure A. C, capillary; M, Mucous Cells; Mi, Mitochondria; S, serous demilune; SD, Secretory Duct. 1,000 X

• C. EM of serous AcinusSublingual Gland. C, capillary; G, Golgi Complex; L, lumen; N, nerve; Nu, Nucleus; RER, rough Endoplasmic Reticulum; V, secretory vesicles. 5,200 X

Submandibular GlandsSubmandibular Glands

• Produces mixed, but mostly serous, saliva

• Electron-dense core product (secretory granules) of unknown composition

• The number of serous demilunes is • The number of serous demilunes is limited.

• The striated ducts of the submandibular gland are much longer than those of parotid or sublingual gland → display many cross sectional profiles of striated duct (characteristic feature)

• CT capsule o/t submandibular gland is extensive and forms abundant septa, which subdivide the gland into lobe and lobules.

Parotid GlandsParotid Glands

• Produced serous saliva → ptyalin

• Electron-dense core product (secretory granules) of unknown composition.

• CT capsule forms numerous • CT capsule forms numerous septa → subdivide the gland into lobes and lobules

LiverLiver

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

• Is enveloped by peritoneum– Simple squamous epithelium

– Dense irregular CT capsule (Glisson’s capsule)– 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 Classic Lobules Lobules

(pigs)(pigs)

3 Concepts of Liver lobules3 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– 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 3 Concepts of Liver Lobulesof Liver Lobules

Hepatic Sinusoids andHepatic Sinusoids and

Perisinusoidal Space of DissePerisinusoidal Space of Disse

• Hepatic sinusoids: the space between the plates of hepatocytes – Sinusoidal lining cells (endothel)– Fenestrated 0.5 µm– Macrophage → Kupfer Cells– 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

fenestra

sinusoid

Ito Cell

Space of Disse

Kupfer CellsKupfer Cells

Hepatic DuctHepatic Duct

• Bile canaliculi → labyrinthine tunnels → cholangioles → canals of Hering → interlobular bile ducts → right and left hepatic duct

• Cholangioles– At the periphery of classic lobules– 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

HepatocytesHepatocytes

• 2 domains: lateral and sinusoidal• Lateral domains

– Form bile canaliculi – Fascia occludentes prevent leakage of bile from bile

canaliculicanaliculi– 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

Bile CanaliculiBile Canaliculi

Gall BladderGall 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

HistophysiologyHistophysiology

• Store, concentrate, and release bile

• Epithelium

– Luminal surface display short microvili – Luminal surface display short microvili

coated by a thin layer of glycocalyx

– Supranuclear: secretory granules

containing mucinogen

– Basal region is rich in mitochondria

PancreasPancreas

• Produced exocrine and endocrine secretions

• CT capsule forms septa → sudivide the • CT capsule forms septa → sudivide the gland into lobules

Exocrine PancreasExocrine 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– 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

Exocrine PancreasExocrine Pancreas

• Duct System

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

• Centroacinar cells: pale, simple low cuboidal ep

Endocrine PancreasEndocrine Pancreas

• Islet of Langerhans

– Richly vascularized spherical conglomeration of + 300 cells

• Cells: β, α, δ, PP, G• 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.

Thank You