Interstitial fluid Interstitial fluid; also known as intercellular fluid and tissue fluid is fluid between the cells of multicellular organisms bathes and surrounds the cells of the body, and provides a means of delivering materials to the cells, intercellular communication, and removal of metabolic waste. -it represents the largest portion of the ECF compartment . The plasma and the interstitial fluid intermingle through pores in the blood capillaries which allow water and most dissolved substances except protein to diffuse . The exchange of material across the capillaries occurs at high rate by diffussion in both directions . Formation of the IF ;The high content of proteins in the plasma accounts for its higher osmotic pressure compared to that of the IF which will attract fluid and dissolved substances into the circulation from the tissue spaces . Opposing this force is the hydrostatic pressure of the blood which tends to force fluids out of the circulation and into the tissue spaces, thus equilibrium is always maintained. Edema; Is the term used to describe an unusual accumulation of interstitial fluid which occurs when an alteration in the balance mentioned earlier occurs . It could happen due to decrease in plasma albumin concentration leading to a decrease in blood osmolarity thus allowing fluid to escape from the circulation to the interstitial space.

Interstitial fluid

Lymph fluid composition The lymphatic system is made up of vessels which collect excess fluid from around the cells by diffusion into lymph capillaries, and returns it to the circulatory system. It consists of; composition of the Lymphatic System ; -Lymph fluid. -Lymph vessels. -Lymph duct. - lymph node. Function 1) lymphatic vessels transport fluids and protein that have escaped from blood vascular system back to the blood - 30 liters of plasma pass out of capillaries each day into the IF. -27 liters get resorbed at capillary -3 liter left in tissue spaces get resorbed into lymph vessels 2) Fat transport from gastrointestinal tract to the blood. 3) Body defense system -lymph nodes filter lymph contains lymphocytes

Lymph fluid It is that colorless, watery fluid originating from the interstitial fluid that is present in the lymphatic system . Composition of lymph.; It has the same composition as interstitial fluid. It has a higher content of protein and contains white blood cells, (its protein content will vary according to which tissue it penetrates).(thus containing proteins , fat absorbed from intestine , waste products , antibodies and lymphocytes .) Formation of lymph: filtration forces water and dissolved substances from the capillaries into thetissue space forming the interstitial fluid. Not all of this water is returned to the blood by osmosis, thus excess fluid is picked up by lymph capillaries thus forming the lymph fluid.

Lymph vessels Lymph vessels; The lymphatic vessels are a network of thin tubes that branch, like blood vessels, into tissues throughout the body. -They are one cell thick. -They are slightly larger and more permeable than blood capilleries.- -They remove excess fluid from around the cells thus preventing edema. - Thus Lymphatic vessels carry lymph, a colorless, watery fluid originating from interstitial fluid (fluid in the tissues to drain it into larger vessels called the ducts. -Unlike the circulatory system, the lymphatic system is not closed and has no central pump; the lymph moves slowly and under low pressure. Like veins, lymph vessels have one-way valves thus allowing the interstitial fluid to enter the lymph capillaries and flow in one direction to the lymph ducts passing through the lymph nodes to empty eventually into the blood circulation.

Lymph composition

Lymphatic system

Lymph nodes Along the network of lymph vessels are small organs called lymph nodes. They are small oval like structures that are 1-25mm long. Clusters of lymph nodes are found scattered around the body especially in the underarms, groin, neck, chest, and abdomen. Function of Lymph nodes ; -They contain cavities called sinuses ,In to which the lymph flows. The walls of the sinuses are lined with Phagocytic cells, which engulf and destroy any foreign particles,e.g., bacteria, viruses that might be present in the lymph thus filtering the lymph as it passes by. -It also play a vital role in the production of immuno competent lymphocytes and macrophages in the specific immune response. When the body is fighting an infection, these lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes. Approximately 25 billion different lymphocytes migrate through each lymph node every day. Thus it cleans the lymph before it returns it back to the blood ,produces lymphocytes and antibodies.

Disorders of the lymphatic system Whenever the lymphatic system cannot drain interstitial fluid from tissues faster than they accumulate, the resulting swelling is known as lymphedema. Accumulation of lymph fluid in the pleural cavities leads to chylothorax. Cancers that develop from lymphocytes are known as lymphomas.