Lymphatic System

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LYMPHATIC SYSTEM
* Carries fluid in one direction, from the tissues to the circulatory system.

Functions of the Lymphatic System
1. Fluid Balance
* Collecting excess fluid and particulate matter from tissues and depositing them in the bloodstream. 2. Fat Absorption
* Absorbs fats and other substance from the digestive tract through lymphatic vessels called lacteals located in the lining of the small intestine. * Fat enters the lacteals and pass through the lymphatic vessels to the venous circulation. 3. Defense

* Microorganism and other foreign substance are filtered from lymph by lymph nodes and from blood by the spleen.

Anatomy of the lymphatic system
A. Lymphatic capillaries and vessels
* Lymphatic vessels carry lymph away from the tissues. Valves in the vessel ensure the one-way flow of lymph. * Skeletal muscle contraction, contraction of lymphatic vessel smooth muscle, and thoracic pressure changes move the lymph through the vessels. * The thoracic duct and right lymphatic duct empty lymph into the blood.

B. LYMPHATIC ORGANS
* The lymphocytes originates from red bone marrow and are carried by the blood to lymphatic organs, the lymphocytes divide and increase in number when the body is exposed to microorganisms or foreign substances. * Lymphatic tissue has very fine reticular fibers; these fibers form an interlaced network that holds the lymphocytes and other cells in place.

* Tonsils
* Form a protective ring of lymphatic tissue around the openings between the nasal and oral cavities and the pharynx. Has 3 group which are the following: 1. Palatine tonsils – located on each side of the posterior opening of the oral cavity. Usually referred to as the “tonsils”. 2. Pharyngeal tonsil – located near the internal opening of the nasal cavity. When it is enlarged, it is commonly called adenoid. 3. Lingual tonsil – posterior surface of the tongue.

* Lymph Nodes
* Rounded structures, varying from the size of a small seed to that of a shelled almond. * Distributed along the various lymphatic vessels and it filters the lymph. * There are three superficial aggregations of lymph nodes on each side of the body: inguinal nodes in the groin, axillary nodes in the axilla (armpit), and cervical nodes in the neck. * Capsule – surrounds each lymph node.

* Trabeculae – subdivide a lymph node into compartments containing lymphatic tissue and lymphatic sinuses. * Lymphatic nodules – lymphocytes and other cells that can form dense aggregations of tissue. * Lymphatic sinuses – spaces between the lymphatic tissues that contain macrophages on a network of fibers. * Germinal centers – the lymphatic nodules containing rapidly dividing lymphocytes.

* Spleen
* Roughly the size of a clenched fist and is located in the left, superior corner of the abdominal cavity. * The white pulp of the spleen responds to foreign substances in the blood, whereas the red pulp phagocytizes foreign substance and worn-out red blood cells. * Its function is also as a blood reservoir.

* Thymus
* A bilobed gland roughly triangular in shape, located in the superior mediastinum. * Site for the maturation of lymphocytes.
* The lymphocytes that survive the maturation process are capable of reacting to foreign substance.

Overview of the lymphatic system
* Lymphatic capillaries remove fluid from tissues and absorb fats from the small intestine. * Lymph nodes filter lymph, spleen filters blood.
* B cells originate and mature in red bone marrow. The pre-T cells enter blood and migrate to the thymus. * B cells and T cells increase in number and circulate to lymphatic and other tissues. They can respond to infections by dividing and increasing in number.

Immunity
* the ability to resist damage from the foreign substances (microorganism, toxins, cancer cells) *...
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