For part I of this entry, I'll briefly go over the anatomy of the liver and the pathophysiology of liver disease. Let's get started!
BASIC ANATOMY OF THE LIVER
The human liver is the 2nd largest organ in the body; weighing in at about 3 pounds. It is located in the right upper abdomen, and is mostly protected by the rib cage. The liver is made up of 5 lobes; the right lobe is much larger than the left. A membrane called the falciform ligament separates the two lobes. The gallbladder lies just under the right lobe.
Vasculature of the Liver
The liver is a very vascular organ; which gives the healthy liver it's smooth, reddish-brown color. The portal vein supplies 2/3's of the liver's blood supply; the blood delivered through the portal vein is very nutrient rich. The other 1/3 of the liver's blood supply is delivered via the hepatic artery; the arterial blood is very oxygen rich.
FUNCTION OF THE LIVER
There are many vital functions performed by the liver. It has digestive, endocrine, excretory, and hematologic function; we'll go over each of them. . .
The liver synthesizes the important blood proteins, including the plasma protein albumin. Albumin helps maintain osmotic pressure in the blood; it prevents fluid from leaking out of the blood vessels and into body tissues. Albumin maintains blood volume. Albumin also helps transport fatty acids, bilirubin, some drugs, and certain hormones through out the body. Chronic liver disease, such as cirrhosis, can lead to fluid build up in the lungs (pulmonary edema [causing shortness of breath, difficulty breathing, and impaired gas exchange]), ankles (peripheral edema [walking or any weight bearing activity causes pain), and peritoneum (also known as ascites). All this displaced fluid will cause also cause extreme fatigue and disrupt a person's normal daily functioning.
Another very important set of blood proteins synthesized by the liver are the vitamin K-dependent coagulation proteins: factors II (prothrombin), VII, IX, & X. The anticoagulant drug, Coumadin (Warfarin) blocks the vitamin K pathway that produces these clotting factors within the liver.
Next, we’ll discuss the digestive functions of the liver… the liver produces bile salts which are vital in the digestion and breakdown of lipids. The liver also processes and stores fat, carbohydrates, protein, minerals, and fat soluble vitamins (such as vitamins A, E, & K). The liver synthesizes cholesterol, which is the precursor to steroid hormones, such as testosterone and estrogen, and is an important part of the phospholipid bilayer of the cell. Lastly, the liver produces triglycerides, which is a type of fat located in the blood and body tissues. Statin drugs reduce cholesterol at the hepatic level by inhibiting the enzyme HMG-CoA reductase, which is vital in the metabolic pathway that produces cholesterol.
The endocrine function of the liver are as follows: regulates the metabolism of carbohydrates, fats, and proteins, metabolizes hormones such as mineralocorticoids, glucocorticoids, and sex hormones. The liver regulates the amount of glucose in the body through glycogenesis (the formation of a glucose polymer, which is a chain called glycogen; this occurs when excessive amounts of glucose are ingested and rapidly taken up by the liver), glycogenolysis (the breakdown of glycogen stored in the liver to glucose, which is then released into the blood stream for cellular uptake) and gluconeogenesis (the enzymatic pathway of synthesizing glucose from non-carbohydrate sources such as amino acids & glycerol; occurs when glycogen stores are depleted).
Here’s a helpful video to help you understand the liver’s role in glucose levels:
The excretory functions of the liver include the excretion of bile and cholesterol, the conversion of ammonia to urea, and the detoxification of drugs, hormones, and other foreign substances. Bile is an aqueous mixture of conjugated bilirubin, bile acids, phospholipids, cholesterol, and electrolytes. Bile is essential to the breakdown of fat in the small intestine and also serves as a repository for heme breakdown products. When the liver is failing, levels of ammonia and other toxins can build up in the blood stream, where they travel to the brain and affect brain function. Since the liver is unable to effectively break down the excess ammonia, a condition called hepatic encephalopathy can occur. Symptoms can range anywhere from confusion to coma. This is why nurses must assess mentation and level of consciousness in a patient with liver failure and treat HE as vigilantly as possible.
This informative video gives an in depth description of the stages of hepatic encephalopathy:
As you can see the liver is such an important organ that serves around 500 individual functions to the human body... In the next parts of this series, we'll go over the modes of treatment for liver failure, what kind of assessment data you can expect to find in a patient with liver failure, and the many causes of liver failure.
Thanks for reading! I hope you found this entry helpful... =)
