Accessory Digestive Glands

ACCESSORY DIGESTIVE GLANDS

LIVER, GALLBLADDER, AND PANCREAS

Pancreas

Pancreas is a mixed exocrine and endocrine gland
Thin capsule with septa between lobules
Exocrine part organized as a compound tubuloacinar glands 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 with receptors for secretin and acetylcholin
Intercalated ducts, Intralobular ducts, and interlobular ducts

Pancreas

Serous cells are truncated pyramidal in shape basophilic,with a round nucleus that is located basally, RER, GA, and secretory granules
Zymogen granules contain: trypsinogen, chymotrypsinogen, carboxypeptidase, ribonuclease, DNAase, lipase, elastase, amylase
Secretion controlled by secretin and CCK from duodenum and vagus nerve
Centroacinar cells and intercalated ducts manufacture a serous, bicarbonate-rich alkaline fluid
Main pancreatic duct goes to duodenum

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 1) EXOCRINE PORTION
2) ENDOCRINE PORTION

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 1) EXOCRINE PORTION
2) ENDOCRINE PORTION
- synthesizes and secretes enzymes via a system of ducts that are essential for digestion in the intestine
- synthesizes and secretes hormones into the bloodstream to regulate glucose, lipid, and protein metabolism

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 1) EXOCRINE PORTION
- COMPOUND ACINOUS GLAND
- EACH ACINI CONSIST OF 5-8 PYRAMIDAL CELLS THAT SIT ON A BASAL LAMINA AND SURROUND A CENTRAL LUMEN
ACINAR CELLS
- BASALLY LOCATED NUCLEI & RER
- SUPRANUCLEAR GOLGI ZONE
- ZYMOGENIC GRANULES CONTAINING DIGESTIVE ENZYMES IN APICAL REGION
CENTROACINAR CELLS
- LINE LUMEN OF ACINUS
- SECRETE LARGE AMOUNTS OF BICARBONATE

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 1) EXOCRINE PORTION
INTERCALATED DUCTS
INTRALOBULAR DUCTS
INTERLOBULAR DUCTS
MAIN DUCTS
PANCREAS H&E

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 1) EXOCRINE PORTION
INTERCALATED DUCTS
- lined with simple squamous epithelium
INTRALOBULAR DUCTS
- lined with simple cuboidal epithelium
- size on the order of magnitude of acini
INTERLOBULAR DUCTS
- lined with simple columnar epithelium
- found in fibroconnective tissue septa

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 1) EXOCRINE PORTION
ACINAR CELLS
- BASALLY LOCATED NUCLEI & RER
- SUPRANUCLEAR GOLGI ZONE
- ZYMOGENIC GRANULES CONTAINING DIGESTIVE ENZYMES IN APICAL REGION
CENTROACINAR CELLS
- LINE LUMEN OF ACINUS
- SECRETE LARGE AMOUNTS OF BICARBONATE
trypsinogen, amylase, lipase

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 1) EXOCRINE PORTION
INTERCALATED DUCTS
PANCREAS H&E

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 1) EXOCRINE PORTION
PANCREAS H&E
EXO-
ENDO-
2) ENDOCRINE PORTION

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 2) ENDOCRINE PORTION
- PRINCIPLE FUNCTION IS TO SECRETE HORMONES THAT REGULATE BLOOD GLUCOSE LEVELS
ISLETS OF LANGERHANS
- MASSES OF RICHLY VASCULARIZED ENDOCRINE CELLS SCATTERED THROUGHOUT THE PANCREAS
- SEPARATED FROM SURROUNDING ACINAR CELLS BY THIN CAPSULE OF RETICULAR FIBERS
- 3 CELL TYPES IN ISLET DISTINGUISHED ONLY VIA SPECIAL STAINS

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 2) ENDOCRINE PORTION

ACCESSORY DIGESTIVE GLANDS

 PANCREAS 2) ENDOCRINE PORTION
CELL TYPES:
1) ALPHA CELLS (20%)
2) BETA CELLS (75%)
3) DELTA CELLS (5%)
- SECRETE GLUCAGON; RAISES BLOOD GLUCOSE LEVELS
- SECRETE INSULIN; LOWERS BLOOD GLUCOSE LEVELS
- SECRETE SOMATOSTATIN; INHIBITS GLUCAGON AND INSULIN SECRETION

ACCESSORY DIGESTIVE GLANDS

 LIVER 1) EXOCRINE PORTION
2) ENDOCRINE PORTION
- synthesizes and secretes bile via a system of ducts that is essential for digestion in the intestine
- synthesizes and secretes numerous plasma proteins into the bloodstream: (albumin, fibrinogen, prothrombin, lipoproteins, etc.)


Liver
Liver is the largest gland in the body, weighing about 1500 gr , it has endocrine and exocrine functions
Dense irregular connective tissue capsule of liver is loosely attached to liver except at porta hepatis where blood and lymph vessels and bile ducts enter or exit the gland
Receives portal blood (75%) from small intestine via portal vein and oxygenated blood from hepatic arteries (25%)
CT elements are sparse, bulk of liver is composed of hepatocytes
Liver has a lobular organization
Classical lobule in which 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

ACCESSORY DIGESTIVE GLANDS

 LIVER PORTA HEPATIS
PORTAL TRIAD

ACCESSORY DIGESTIVE GLANDS

 LIVER Classical Liver Lobule
- basic functional unit of liver

ACCESSORY DIGESTIVE GLANDS

 LIVER CLASSIC LOBULE
PORTAL LOBULE
LIVER ACINUS
- central vein at center
- hexagonal in shape
- portal triad at corners
- portal triad at center
- triangular in shape
- central vein at corners
- short axis: branches of portal triad between 2 classic lobules
- long axis: between 2 central veins


Liver
Central vein terminates in sublobular vein, these veins also join each other forming collecting veins which in turn form hepatic veins
In classical lobule concept blood flow from periphery to center of lobule
Bile manufactured by hepatocytes flow in opposite direction in small intercellular spaces known as bile canaliculi
Portal lobule is 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)

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)

Liver
Sinunosoidal domains of cell membrane have many microvilli protrude to perisinusoidal space (of Disse), endocrine secretion of hepatocytes release here
Hepatocytes are large cells which are contain RER, free ribosomes, several sets of Golgi apparatuses, SER, mitochondria, lipid droplets, glycogen
Bile secreted from hepatocytes into bile canaliculi contains water, ions, bile salts and acids, phospholipids, cholesterol, & bilirubin

ACCESSORY DIGESTIVE GLANDS

ACCESSORY DIGESTIVE GLANDS
 LIVER 1 HEPATOCYTES 2 SINUSOIDS 3 SPACE OF DISSE 4 BILE CANALICULI

ACCESSORY DIGESTIVE GLANDS

 LIVER 1 HEPATOCYTES 2 SINUSOIDS 3 SPACE OF DISSE 4 BILE CANALICULI - perisinusoidal space between basal surfaces of the endothelial cells and the surfaces of the hepatocytes
- small canal beginning the biliary tree formed by apposed grooves in adjacent hepatocytes


LIVER

ACCESSORY DIGESTIVE GLANDS

 LIVER

LIVER H&E

PV
HA
BD

ACCESSORY DIGESTIVE GLANDS

 LIVER BILE DUCTS
- lined with simple cuboidal epithelium

ACCESSORY DIGESTIVE GLANDS

 LIVER LIVER H&E
1 HEPATOCYTES 2 SINUSOIDS

ACCESSORY DIGESTIVE GLANDS

 LIVER LIVER
RETICULAR FIBER MESHWORK

ACCESSORY DIGESTIVE GLANDS

 LIVER RETICULAR FIBER MESHWORK
KUPFFER CELLS
- phagocytic cell, liver macrophage

ACCESSORY DIGESTIVE GLANDS

 LIVER KUPFFER CELLS
CV
LIVER H&E

ACCESSORY DIGESTIVE GLANDS

 LIVER KUPFFER CELLS
LIVER H&E

ACCESSORY DIGESTIVE GLANDS

 LIVER 3-D APPRECIATION FOR HISTOLOGICAL STRUCTURE OBSERVED IN 2-D

ACCESSORY DIGESTIVE GLANDS

 LIVER 3-D LOOK AT THE BILIARY SYSTEM

ACCESSORY DIGESTIVE GLANDS

 GALLBLADDER ROUTE OF BILE
HEPATOCYTE
BILE CANALICULI
RT & LT HEPATIC DUCTS
COMMON BILE DUCT
FILLING OF GALLBLADDER
- LOCATION FOR CONCENTRATION AND STORAGE OF BILE

ACCESSORY DIGESTIVE GLANDS

 GALLBLADDER THREE LAYERS:
1) MUCOSA
- lined with tall columnar epithelium and underlying basal lamina & lamina propria
- mucosa highly folded and irregular
2) MUSCULARIS EXTERNA
- layers of smooth muscle with irregular orientation
3) ADVENTITIA or SEROSA
- NO MUSCULARIS MUCOSA OR SUBMUCOSA -

ACCESSORY DIGESTIVE GLANDS

 GALLBLADDER EPITHELIUM:
- tall columnar epithelium and underlying basal lamina & lamina propria
- basally located nuclei
- fine microvilli border