anaphysio hepatobiliary system

8/2/2019 Anaphysio Hepatobiliary System

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HEPATOBILIARYSYSTEM ANATOMY & PHYSIOLOGY

MARGARET XAIRA R. MERCADO RN



GROSS ANATOMY

The liver is the largest gland in the body (Weight 1.36kg) . It is located on the right side of the upper abdomen.

It is a soft, "wedge-shaped" organ, reddish-brown incolor because of the rich supply of blood flowing through it.

Liver is made of two lobes.

The right lobe is the larger, measuring 6 to 7 inches inlength. The left lobe is approx 3 inches in length.



The liver is covered entirely by visceral peritoneum,

except for a small area where it connects to thediaphragm The peritoneum folds back on itself to form the

falciform ligament and the right and left triangular

ligaments. The falciform ligament divides the liver into a left

lobe, and a right lobe. If seen from visceral side, twomore lobes are visible : the caudate lobe and belowthis the quadrate lobe.

From behind, ligamentum venosum divides these lobesand ligamentum teres divides the caudate from thequadrate lobe.



How does Liver look when seenthrough microscope? When viewed under a microscope, theliver is seen as large number of hepatic

lobules. The hepatic lobule looks like a six-sided

cylinder. A central vein runs through the center

of the lobe. Liver cells are arranged in the form of

cords.

Between these cords lies thin-walledblood vessels called sinusoids.



BLOOD SUPPLY OF LIVER

Two major blood vessels supply liver. Hepatic artery Portal vein

The hepatic artery comes off the celiac trunk which inturn comes from aorta. The venous blood from the digestive tract is collected

by the portal vein, which then supplies blood to liver.

The hepatic veins drain blood from liver into theinferior vena cava.



BILIARY SYSTEM

Liver produces bile. Bile is then collected in bile capillaries, which merge to

form bile ducts. Bile duct drain into right and left hepatic ducts, which

combine to form common hepatic duct. The bile is stored and concentrated in gall bladder

during fasting state. When person takes food, Gall bladder contracts, emptying

bile into cystic duct, which combines with common hepaticduct to form common bile duct. Common bile duct drains bile into duodenum through

ampulla of vater, a sphincter which controls bile flowinto duodenum.



PHYSIOLOGY OF THE LIVER



REGULATIONS, SYNTHESIS, AND SECRETION

Hepatocytes are metabolically active cells They are involved in regulation of various biochemical

and metabolic functions and are involved in synthesisof various substances in the body.

They take up glucose, minerals, and vitamins fromportal and systemic blood and store them.

Many important substances such as blood clotting

factors, transporter proteins, cholesterol, and bilecomponents are synthesized by the hepatocytes. The hepatocytes also regulate blood levels of

substances such as cholesterol and glucose, the liver helps maintain body homeostasis.



Glucose The liver store glucose when it is in excess after the person

has food and release glucose in the blood when he isstarving.

This is an important function which when impaired during liver disease, result in hypoglycemia (low blood glucose).



Proteins Most blood proteins (except for antibodies) are

synthesized and secreted by the liver. One of the most abundant serum proteins is albumin. Impaired liver function results in decreased serum albumin

level. The liver also produces most of the proteins responsible

for blood clotting, called coagulation or clotting factors.

Hence in severe liver disease, excessive bleeding may resultdue to lack of these factors.



Bile Hepatocyte synthesize bile.

Bile is a greenish fluid containing cholesterol,phospholipids, bilirubin (a metabolite of red blood cellhemoglobin), and bile salts.

It is secreted into biliary ducts. It then leaves the liver tobe temporarily stored in the gallbladder before

emptying into the small intestine. Bile salts act as "detergents" that aid in the digestion

and absorption of dietary fats. Liver damage or obstruction of a bile duct (e.g.,

gallstone) can lead to cholestasis, (the blockage of bileflow, which causes the malabsorption of dietary fats),steatorrhea (foul-smelling diarrhea caused by non-absorbed fats), and jaundice.



Lipids Liver synthesizes cholesterol. It is then packaged and distributed to the body or excreted

into bile for removal from the body. Increased cholesterol concentrations in bile may

predispose to gallstone formation.

The liver also synthesizes lipoproteins. These are made up of cholesterol, triglycerides

phospholipids, and proteins. Lipoproteins transfers cholesterol between the liver and

body tissues. Most liver diseases do not significantly affect serum lipid

levels. However, cholestatic diseases, may be associatedwith increased levels.

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Storage As mentioned earlier, the liver store important substances

eg glucose (in the form of glycogen). The fat-soluble vitamins (vitamins A, D, E and K), folate,

vitamin B 12 , and minerals such as copper and iron.



PURIFICATION, TRANSFORMATION,AND CLEARANCE

The liver removes harmful substances (such as ammonia,toxins, various drugs) from the blood and then breaksthem down or transforms them into less harmfulcompounds.

Ammonia The liver converts ammonia to urea. Urea is then excreted into the urine by the kidneys. In the

presence of severe liver disease, ammonia accumulates in

the blood because of both decreased blood clearance anddecreased ability to form urea. Elevated ammonia levels can be toxic, especially to the

brain, and may lead to the development of hepaticencephalopathy.



Bilirubin Bilirubin is a yellow pigment. It is formed as a breakdown product of red blood cell

hemoglobin. The spleen, which destroys old red cells, releases

ünconjugated" bilirubin into the blood, where it circulates inthe blood bound to albumin.

The liver takes up bilirubin and "conjugates" it with

glucuronic acid to form "water-soluble" bilirubin that can beexcreted into bile. Increased production or decreased clearance of bilirubin

results in jaundice.



Hormones Liver plays important roles in hormonal modification and

inactivation. Chronic liver disease may cause hormonal imbalances. For example, the masculinizing hormone testosterone and

the feminizing hormone estrogen are metabolized andinactivated by the liver.

Men with cirrhosis, have increased circulating estrogens

relative to testosterone derivatives. This may result intesticular atrophy and gynaecomastia.



Drugs Most drugs are metabolized by the liver. Oral drugs are absorbed in the intestine and then in the

liver, drugs may undergo first-pass metabolism, a process in

which they are modified, activated, or inactivated beforethey enter the systemic circulation, or they may be leftunchanged.

In patients with liver disease, drug detoxification andexcretion may be dangerously altered, resulting in drug concentrations that are too low or too high or theproduction of toxic drug metabolites.



Toxins The liver is responsible for detoxifying many chemical

agents and poisons including alcohol. Liver disease may inhibit or alter detoxification processes

and thus increase the toxic effects of these agents. Additionally, exposure to chemicals or toxins such as

alcohol may directly affect the liver, ranging from milddysfunction to severe and life-threatening damage.



ANATOMY OF THE BILIARY SYSTEM

The biliary system consists of the organs and ducts (bile ducts,

gallbladder, and associated structures) that are involved in theproduction and transportation of bile. The transportation of bilefollows this sequence:

When the liver cells secrete bile, it is collected by a system of ducts that flow from the liver through the right and left hepaticducts.

These ducts ultimately drain into the common hepatic duct. The common hepatic duct then joins with the cystic duct from the

gallbladder to form the common bile duct, which runs from the liver to the duodenum (the first section of the small intestine).

However, not all bile runs directly into the duodenum. About 50percent of the bile produced by the liver is first stored in the

gallbladder, a pear-shaped organ located directly below the liver. Then, when food is eaten, the gallbladder contracts and releases

stored bile into the duodenum to help break down the fats.



FUNCTIONS OF THE BILIARY SYSTEM

The biliary system's main function includes the following: To drain waste products from the liver into the duodenum To help in digestion with the controlled release of bile Bile is the greenish-yellow fluid (consisting of waste

products, cholesterol, and bile salts) that is secreted by theliver cells to perform two primary functions, including thefollowing: To carry away waste

To break down fats during digestion Bile salt is the actual component which helps break down

and absorb fats. Bile, which is excreted from the body inthe form of feces, is what gives feces its dark brown color.

anaphysio hepatobiliary system

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