anatomyphysiologyblog - HEPATOBILIARY APPARATUS: HISTOLOGY OF LIVER AND GALL BLADDER

Structure of the liver

The histological features of the liver are summarized below.

• Structural constituent of liver include

– Connective tissue stroma

– Parenchyma

– Portal triad

– Sinusoids

– Bile canaliculi

• There are 3 agency to depict the construction of liver

– The classic lobule

– The portal lobule

– Portal acinus

Classical lobule

• Connective tissue stroma

– liver is covered yesteryear a sparse connector tissue capsule (Glisson's capsule) as well as extends into its interior equally numerous branching septa.

– Blood vessels, nerves, lymphatic vessels as well as bile ducts move inside these septa.

• Parenchyma

– In cross section, the heart as well as somebody of liver appears to last made upward of hexagonal areas that constitute the hepatic lobules. In for sure animals (eg, pigs micrograph b inwards side yesteryear side figure), the lobules are separated yesteryear connector tissue septa (C). But inwards human (micrograph c inwards side yesteryear side figure) the septa are non distinct as well as the lobules look to merge amongst each other making it hard to institute the exact limits betwixt dissimilar lobules.

– Each lobule consists of interconnected plate of liver cells (hepatocytes). These plates are i prison theater cellphone thick that branch as well as anastomose amongst each other to cast network.

– The centre of the lobule is occupied yesteryear a central vein (V) which is a tributary of hepatic vein

– Along the periphery of each lobule at that spot are angular intervals filled yesteryear connector tissue. These intervals are called portal canal/tract (T). Each portal tract contains a venule (a branch of the portal vein), an arteriole (a branch of the hepatic artery), a duct (part of the bile duct system).These 3 structures collectively cast a portal triad.

• venule contains blood coming from the superior as well as inferior mesenteric as well as splenic veins.

• The arteriole contains oxygen-rich blood coming from the celiac torso of the abdominal aorta.

• The duct, carries bile synthesized yesteryear the hepatocytes as well as eventually empties into the hepatic duct

Bile canaliculi

– Each liver prison theater cellphone is cuboidal presenting half dozen surfaces, out of which 2 surfaces are related to the sinusoids as well as the remaining surface are inwards contact amongst the wall of side yesteryear side hepatocyte. Wherever 2 hepatocytes are inwards contact, they brand a tubular infinite betwixt them known equally the bile canaliculus

– Bile is synthesised yesteryear hepatocytes as well as secreted into bile canaliculi

– Bile canaliculi of side yesteryear side hepatocyte plates merge to cast canals of Hering or bile ductules which latter in conclusion drain into the bile duct inwards the portal canal

Portal lobule

• The portal lobule emphasizes the exocrine functions of the liver

• The portal lobule includes the territory of liver tissue centered only about a portal triad, as well as is drawn yesteryear joining the key veins of the 3 side yesteryear side liver lobules

• The territory of portal lobule includes those part of 3 classic lobules that secrete the bile that drains into its axial bile duct.

Liver acinus

• Liver acinus is the structural unit of measurement that provides the best correlation betwixt blood perfusion as well as metabolic activeness

• It consists of the expanse of liver tissue supplied yesteryear i hepatic arteriole running along the business of junction of 2 hepatic lobule. Two key veins prevarication at the ends of the acinus.

Structure of Gall Bladder

The histological features of the gallbladder are summarized below.

• consists of a mucosa composed of uncomplicated columnar epithelium as well as lamina propria, fibromuscular layer, as well as a serous membrane

• Mucous membrane:

– lined yesteryear is a unmarried layer of tall columnar absorptive cells bearing numerous brusk irregular microvilli . Goblet cells are absent.

– Mucosa is highly folded, as well as the folds are called rugae.The submucosa (S) is relatively loose.

• The fibromuscular coat: is composed of fibrous tissue (A) mixed amongst shine musculus cells (M) which are arranged loosely inwards longitudinal, round down as well as oblique bundles but create non cast distinct layers.

References
Gray's Anatomy
K. L. Moore's Clinically Oriented Anatomy
R. Snell's Clinical Anatomy
Wheater's Functional Histology