Accessory organs of digestive systemPresentation Transcript
Food provides us with fuel to live, energy to work and play, and the raw materials to build new cells. All the different varieties of food we eat are broken down by our digestive system and transported to every part of our body by our circulatory system .
ACCESSORY ORGANS OF THE DIGESTIVE ORGAN
The liver is the largest glandular organ of the body. It weighs about 3 lb (1.36 kg). It is reddish brown in color and is divided into four lobes of unequal size and shape. The liver lies on the right side of the abdominal cavity beneath the diaphragm. Blood is carried to the liver via two large vessels called the hepatic artery and the portal vein. The heptic artery carries oxygen-rich blood from the aorta (a major vessel in the heart ). The portal vein carries blood containing digested food from the small intestine. These blood vessels subdivide in the liver repeatedly, terminating in very small capillaries. Each capillary leads to a lobule. Liver tissue is composed of thousands of lobules, and each lobule is made up of hepatic cells, the basic metabolic cells of the liver.
Your Liver Lets You Live Your liver, located under your right rib cage, normally weighs about three pounds and is the body's second largest organ. (Your skin is the largest.) It is a complex chemical factory which produces many important substances such as bile, digestive enzymes, clotting factors, cholesterol, and proteins. It is essential in the metabolism of fats, carbohydrates, proteins, and the various vitamins and minerals. It helps control the level of blood sugar and fats. It cleanses the blood and detoxifies drugs and potentially harmful chemicals such as alcohol. The liver is a storehouse for blood, vitamins and minerals, and glycogen - the stored form of sugar - the body's major fuel. The liver is an amazing machine and largely unappreciated - until something goes wrong.
What is its major function? The liver has many functions. Some of the functions are: to produce substances that break down fats, convert glucose to glycogen, produce urea (the main substance of urine), make certain amino acids (the building blocks of proteins), filter harmful substances from the blood (such as alcohol), storage of vitamins and minerals (vitamins A, D, K and B12) and maintain a proper level or glucose in the blood. The liver is also responsible fore producing cholesterol . It produces about 80% of the cholesterol in your body.
FUNCTIONS OF THE LIVER
Excretion of IgA (defense against bacteria in the gut)
Special macrophages (Kupffer cells) gobble up bacteria which have crossed from the gut into the blood. Macrophage means "big eater" and so they are!
poisons from the gut
nutrients such as amino acids, sugar and fat
bilirubin, bile acids
cholesterol, bile acids, phospholipids
poisons (e.g. pesticides, insecticides, heavy metals)
proteins including the clotting factors
bile acids (products of cholesterol, important in fat digestion)
fat and cholesterol
vitamins, in particular the fat soluble ones (A, D, E and K)
The pancreas does not actually digest any of the foods that you eat, but makes most of the enzymes that do. The pancreas sends the enzymes to the small intestine through a tube called the pancreatic duct.
The pancreas, is a gland in the abdomen that produces enzymes and hormones. The pancreas produces digestive juices (enzymes) that continue the process of breaking down foods, which begins in the stomach. The pancreas also produces hormones, most famously insulin, which control the balance of glucose between the blood and the rest of the body. Thanks to the pancreas, the body can use the sugars and store the fats, which are essential for health.
What the pancreas looks like? The pancreas looks like a flat, elongated tadpole 6-10 inches (18-25 cms.) long. It lies behind the stomach in the upper abdomen. Its broadest part, called the head, is attached to the duodenum, which is the loop at the top of the small intestine. The stomach empties already partially digested food and liquid into the duodenum and it is here that it mixes with the secretions from the pancreas. The main part of the pancreas, the body, extends leftwards and slightly upwards, narrowing towards a tail. The pancreas can be compared with a stalk with clusters of grapes attached to it. It has a duct running through its length which is joined by many small branches from the glandular tissue. This duct joins another duct bringing bile from the liver, and a single duct then opens into the duodenum. The pancreas is composed of two main types of tissue. Most of this is known as exocrine tissue which produces pancreatic enzymes - a litre (2.2 pints) or more every day - which aid digestion. If insufficient enzymes are produced serious malnutrition can result even though enough high quality food is being eaten. Embedded throughout the mass of exocrine tissue are the grape-like clusters of hundreds of thousands of endocrine cells, known as islets of Langerhans. These produce two main hormones which regulate pancreatic secretions and control blood glucose, the body's fuel.
The pancreas is an amazingly efficient, self-regulating organ, far cleverer than any machine ever invented. Day in, day out throughout a lifetime, a healthy pancreas produces exactly the right chemicals at the right times in the right quantities for digesting the food we eat. As soon as food enters the duodenum, the pancreas begins its biggest job, which is to secrete from its exocrine tissue the clear, watery, alkaline juice containing enzymes that help break down food into molecules small enough to be absorbed by the intestine. Two of these enzymes, trypsin and chymotrypsin digest proteins. The enzyme amylase breaks down carbohydrate foods. Another enzyme, lipase, breaks down fats, into smaller molecules called fatty acids and cholesterol. The two main hormones produced by the endocrine tissue are insulin and glucagon. 1. Insulin is secreted when the blood sugar is raised and causes the muscles and other bodily tissues to take up glucose from the blood to fuel their activity. Insulin also promotes the absorption of glucose into the liver, where it is stored as glycogen for use in response to stress or exercise. 2. Glucagon is released from the pancreas when the blood sugar is low. It's main effect is on the liver to cause the breakdown of glycogen (the stored form of glucose) into glucose which is released into the blood thus restoring the level to normal.
What can go wrong with the pancreas For most of us, the pancreas is a wonderfully self-sustaining organ. But of course, like any organ, it can malfunction. If it fails to produce sufficient digestive enzymes and food is poorly absorbed, weight loss and/or diarrhoea can result. Much more important, however, is the risk of diabetes if the islets of Langerhans produce too little insulin. This raises the level of glucose in the blood, and increases the risk of a number of problems throughout the body. (for more information about diabetes,see our factsheet.) The most important disease of the pancreas itself is pancreatitis (inflammation) which can be acute or chronic. It may occur as a complication of mumps. However, the most common cause of acute pancreatitis is blockage by a gallstone of the main duct from the pancreas. This causes pancreatic juice to accumulate in the organ which can damage the pancreas or even result in the pancreas digesting itself. Fortunately, this serious condition is rare. However when it does occur it requires immediate medical attention. The symptoms include severe stomach pain and tenderness, nausea and vomiting, swelling of the abdomen and wind, fever and muscle aches. Treatment involves painkillers, stopping all solid food and providing fluid and nourishment with intravenous fluids (through a drip into a vein). Most people with acute pancreatitis recover completely but about 10% of people develop complications which are fatal. Chronic pancreatitis occurs either when repeated episodes of acute pancreatitis result in permanent damage to the organ or as the result of chronic damage resulting from alcohol abuse. It affects mainly middle aged men. Symptoms include persistent pain in the upper abdomen and back, weight loss, diarrhoea, and sometimes diabetes and mild jaundice (yellow eyes and skin). Occasionally, chronic pancreatitis can lead to cancer of the pancreas. In most cases, however, the cause of pancreatic cancer, (which unfortunately, is on the increase in the UK) is unknown. Smoking or heavy drinking may increase the risk, and cancer of the pancreas is also about twice as common in people with diabetes. It is also more common in men than women. Symptoms may not appear for some time and, even then, are usually vague, no more than discomfort or pain in the stomach and back or, if the cancer blocks a duct, jaundice. The skin may itch and there may be constipation and loss of appetite and weight. Such symptoms can be caused by many conditions other than cancer, but tell your doctor about any which persist as early diagnosis is important. Treatment of pancreatic cancer is difficult and the outlook is usually poor. Quite often, by the time the cancer is diagnosed it has advanced too far to be treated with anything except pain relief.
The pancreatic juices are composed basically of water, bicarbonate and three enzymes.
Water helps the nutrients and enzymes to come into contact with one another, by allowing them to move around within the small intestine.
The acid of the stomach is neutralized by bicarbonate made by the pancreas.
Trypsin acts on the proteins and completes the process of breaking proteins into amino acids begun in the stomach by pepsin..
Pancreatic Amylase continues the action on the carbohydrates that the saliva began.
Pancreatic lipase contributes to the transformation of fats begun by the bile from the liver. Without the bile from the liver, the fats would be too large for pancreatic lipase to work.