Lymphatic System & Lymph Node

Lymphatic System & Lymph Node Dr. Muhammad Rafique Objectives Define Lymph Formation of Lymph Constituents of Lymph Circulation of Lymph Lymph capillaries, Lymph Vessels & Lymph trunk External features of Lymph nodes Cross section of Lymph nodes Functions of Lymph nodes Formation of Lymph At the arterial end of capillaries the pressure inside the capillaries is high and plasma fluid along with nutrients and O2 come out of capillaries and collected within the interstitial spaces . The O2 and nutrients enters the cells while CO2 and waste products comes out from the cells now collected within interstitial space. Formation of Lymph Fluid, lipid soluble substances and CO2 are absorbed at venous end of capillaries which has low pressure inside. The colloidal substances which are lipid insoluble and have larger molecular weight can not be absorbed into the circulation and collected within the interstitial space is called as Lymph. Composition of Lymph Lymph from interstitial space consists of clear, colorless fluid very similar to plasma contains, plasma proteins and white blood cells but does not contains RBS. But lymph from interstitial space pale in color and contains more lipid which absorbed from the intestine this fluid is called as chyle Interstitial Fluid (Lymph) Lymph is absorbed by another system of channels, called as Lymphatic System. The lymph channels begins with in the interstitial spaces as the blind cannels . Each lymphatic channel fenestrated has a number of pores. Through this pores the fluid with larger molecular weigh absorbed. The lymphatic system is a pressure less system i.e. there is no pressure inside the channels Circulation of Lymph Lymph absorbs from the interstitial spaces and circulates through the lymphatic channels, ultimately draining into the venous circulation. Before reaching venous circulation the lymph should pass through one of group of lymph nodes. The lymph, lymphatic channels and lymph nodes are the part of immune system. Lymphatic Circulation The lymphatic channels begin within the interstitial spaces as the blind channels, they are smaller in size. Smaller lymphatic channels unite together and formed larger vessels, which run along with the blood vessels. There is general rule that superficial lymphatic vessels run along wit veins while deeper lymphatic vessels run along with arteries Lymphatic Circulation Unlike the cardiovascular system, the lymphatic system is not closed and has no central pump. Lymph movement occurs with low pressure due to peristalsis, valves, and the contraction of skeletal muscles. Like veins, lymph travels through vessels in one way only, due to semilunar valves. This depends mainly on the movement of skeletal muscles to squeeze fluid through them, especially near the joints. Rhythmic contraction of the vessel walls through movements may also help draw fluid into the smallest lymphatic vessels, capillaries. Lymph Nodes Lymph absorbs from the interstitial spaces and travel to lymph nodes which are present in the path of lymphatic vessels. The lymph nodes are usually present in groups for e. g. Axillary lymph nodes or Inguinal lymph nodes. The lymphatic vessels which bring lymph towards the lymph nodes are called as Afferent lymphatic vessels. Structures of Lymph Nodes A lymph node is bean of rennin or kidney shaped. It has convex surface, and at one site it shows concavity which bears a depression, called as hilum. Through the hilum the efferent lymphatic vessels, and vein leave the lymph nodes while artery enters the lymph node. Lymph node is surrounded by the thick capsule. Afferent Lymphatic vessels Afferent lymphatic vessels enter the lymph nodes penetrate the thick capsule and pour their contents into lymph nodes Cross Section of Lymph Nodes On cross section the lymph node divided into two regions, outer cortex and inner medulla. Afferent lymphatic vessels pour their lymph into cortex. Lymph contains proteins, tissue debris and foreign particulates, may be microorganism. When lymph passing through cortex of lymph node most of debris removed and micro-organism presented to lymphocytes . Passage of Lymph After passing trough the cortex the lymph collected into medulla and than drains into efferent lymphatic vessels. Than lymph ultimately drains into venous circulation Functions of Lymph Node Filtration of lymph First line of defense against microorganism Micro-organism acts as antigens and produced antibodies as part of immune system