What type of gland is the liver

Therefore, the fenestrations permit blood plasma to wash freely over the exposed surfaces of the hepatocytes in the space of Disse. The space between the endothelium and the cords is named the space of Disse.

Its location is that of connective tissue, and it does contain a network of reticular fibers collagen type III which hold the hepatocytes together. More significantly, since the fenestrations of the endothelium permit free movement of blood plasma, the "interstitial fluid" of the space of Disse is blood plasma. Hence, for all practical purposes, hepatocytes reside in direct contact with blood. Bile canaliculi , formed by apical surfaces of adjacent hepatocytes , form a network of tiny passages contained within each cord.

The microscopic appearance of cords and sinusoids can vary markedly depending on quality of histologic preparation. In some specimens, sinusoidal spaces are quite evident as in the image at left. In other specimens, sinusoidal spaces are obliterated by swollen hepatocytes as at right. Blood from both portal vein and hepatic artery the liver's dual blood supply mixes together in the hepatic sinusoids and then drains out of the lobule through the central vein , a branch of the hepatic vein.

The large sinusoidal volume permits sinusoidal blood to "percolate" comparatively slowly through the liver parenchyma, thereby associating intimately with hepatocytes. This, in turn, provides time for efficient transfer of substances across the hepatocyte membrane. Associated with the sinusoids are stellate Kupffer cells -- liver macrophages which effectively catch and destroy bacteria which entered the blood in the intestine.

The endothelium which lines liver sinusoids is fenestrated i. The fenestrations permit blood plasma to wash freely over the exposed surfaces of the hepatocytes through the space of Disse. The space between the fenestrated endothelium and the cords is named the space of Disse. Historical note : In , long before electron microscopy had resolved sinusoidal endothelium with its fenestrations, Joseph Disse had experimentally demonstrated the presence of the eponymous underlying plasma-filled space.

Stellate Ito cells named after Toshio Ito , located at intervals within the space of Disse, store fat and vitamin A. The location for the space of Disse is that of connective tissue, and, as one might thus expect, this space does contain scattered reticular collagen fibers and fibroblasts.

Liver Pathology Please review the general note about pathologic histology in year one. Because the body depends on so many various liver functions , the liver is also involved in a variety of pathological processes.

As a result, many diseases give rise to characteristic changes in the appearance of the liver. The microscopic appearance of the liver can therefore be extremely useful for diagnosis. Even advancing age can be estimated by the accumulation of lipofuscin pigment in hepatocytes.

Fortunately, the liver is easily accessible for needle biopsy directly through the abdominal wall. It also heals readily. So microscopic examination of liver biopsy is a fairly routine clinical procedure. Failure of adequate venous drainage from the liver leads to chronic passive congestion , with blood backing up in centrilobular areas.

This gives rise to a gross appearance picturesquely labelled "nutmeg liver". A high concentration of leukocytes in portal connective tissue is a sign of inflammation , or hepatitis. Because blood flows from the periphery toward the center of each liver lobule , hepatocytes in the periphery respond first to whatever demands are placed upon them by incoming blood. Peripheral cells are therefore most vulnerable and first to be damaged by incoming insults, such as alcohol or other toxins.

With sufficient liver damage, many portal areas may collapse together portal collapse , WebPath. Although hepatocytes are capable of considerable regeneration, chronic damage can lead to scarring as the missing hepatocytes are replaced by fibrous connective tissue.

If the damaged hepatocytes are located peripherally a common pattern, as noted above , the resulting scar expands out from and portal areas. In human liver, the appearance of connective tissue extending out from portal areas is pathological, the defining characteristic of cirrhosis.

Cirrhosis is a non-specific descriptive term, equivalent to "sclerosis", "fibrosis", or simply "scarring".

It is indicative of a past history of tissue destruction. The associated presence of inflammatory cells suggests an ongoing process of damage.

Lobules , Acini , Portal Areas. Cords , Sinusoids. The liver is classed as a gland and associated with many functions. It is difficult to give a precise number, as the organ is still being explored, but it is thought that the liver carries out distinct roles. Because of the importance of the liver and its functions, evolution has ensured that it can regrow rapidly as long as it is kept healthy. This ability is seen in all vertebrates from fish to humans.

The liver is the only visceral organ that can regenerate. It can regenerate completely, as long as a minimum of 25 percent of the tissue remains. One of the most impressive aspects of this feat is that the liver can regrow to its previous size and ability without any loss of function during the growth process. In mice, if two-thirds of the liver is removed, the remaining liver tissue can regrow to its original size within 5 to 7 days.

In humans, the process takes slightly longer, but regeneration can still occur in 8 to 15 days — an incredible achievement, given the size and complexity of the organ. Over the following few weeks, the new liver tissue becomes indistinguishable from the original tissue.

This regeneration is helped by a number of compounds, including growth factors and cytokines. Some of the most important compounds in the process appear to be:. An organ as complex as the liver can experience a range of problems. A healthy liver functions very efficiently. However, in a diseased or malfunctioning liver, the consequences can be dangerous or even fatal. Fascioliasis: This is caused by the parasitic invasion of a parasitic worm known as a liver fluke, which can lie dormant in the liver for months or even years.

Fascioliasis is considered a tropical disease. Cirrhosis: This sees scar tissue replace liver cells in a process known as fibrosis. This condition can be caused by a number of factors, including toxins, alcohol, and hepatitis. Eventually, fibrosis can lead to liver failure as the functionality of the liver cells is destroyed.

Hepatitis: Hepatitis is the name given to a general infection of the liver, and viruses, toxins, or an autoimmune response can cause it. It is characterized by an inflamed liver.

In many cases, the liver can heal itself, but liver failure can occur in severe cases. Alcoholic liver disease: Drinking too much alcohol over long periods of time can cause liver damage. It is the most common cause of cirrhosis in the world. Primary sclerosing cholangitis PSC : PSC is a serious inflammatory disease of the bile ducts that results in their destruction.

There is currently no cure, and the cause is currently unknown, although the condition is thought to be autoimmune. Hanley Rd, Suite St. Louis, MO We are open Saturday and Sunday! Subject optional. Email address: Your name:. Possible Answers: Pancreas. Correct answer: All of these are sites of glucagon synthesis. Explanation : Glucagon acts in a negative feedback loop with insulin to regulate blood sugar concentration.

Report an Error. Which of the following structures acts as both an exocrine and an endocrine gland? Possible Answers: The adrenal cortex. Correct answer: The pancreas. Explanation : There is a key difference between exocrine and endocrine glands.

Possible Answers: Adrenal cortex. Correct answer: Beta cells of the pancreas. Explanation : Insulin is secreted from the beta cells of the pancreas. Possible Answers: Amylin. Correct answer: Somatostatin. Explanation : Somatostatin is synthesized in the delta cells in the islets of Langerhans in the pancreas, and serves to inhibit insulin and glucagon secretion from beta and alpha cells, respectively. Which of the following does NOT perform endocrine function? Correct answer: All of these are endocrine organs.

Explanation : Endocrine organs are capable of secreting hormones into the bloodstream. Which of the following is not a function of the endocrine system?

Possible Answers: Pancreatic secretions to the intestine. Hypothalamic secretions to the anterior pituitary. Correct answer: Pancreatic secretions to the intestine. Explanation : The endocrine system involves secretions by ductless glands into the bloodstream. Possible Answers: Only hormone A can dissolve in water.

Both hormone A and hormone B can dissolve in water. Both hormone A and hormone B cannot dissolve in water. Correct answer: Only hormone A can dissolve in water.

Explanation : The question states that both hormone A and hormone B act on the collecting ducts of the kidneys. Which of the following is false regarding insulin and calcitonin? Insulin functions to decrease glucose concentration in blood, whereas calcitonin functions to increase calcium concentration in blood II.

They are antagonistic hormones III. Insulin and calcitonin can only act on cells near their respective glands. Possible Answers: I only. Explanation : Insulin is released into the blood from the pancreas and functions to decrease the glucose concentration in the blood. The beta cells of the islets of Langerhans secrete which of the following hormones?

Possible Answers: Glucagon. Correct answer: Insulin. Explanation : Insulin is secreted by the beta cells of the islets of Langerhans in the pancreas in response to high blood glucose levels. Which of the following might explain type I diabetes, also known as juvenile diabetes?

Possible Answers: Consumption of a severely calorie-restricted diet during the first few years of life. Consumption of a high-caloric diet over a number of years. Correct answer: Antibodies directed against -cells in the islets of the pancreas. Explanation : Seeing as type I diabetes results from the destruction of the -cells in the pancreas, this is the only feasible answer. Copyright Notice. Cheyenne Certified Tutor.