Lymphatics

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Lymphatics...

Lymphatic System:

Lymphatics Anatomy and Physiology

1. General

a. Specialized component of the circulatory system comprising lymph fluid, lymphatic vessels, lymph nodes, tonsils, thymus, and spleen.

b. As part of the circulatory system, it functions to maintain fluid balance and provide immunity.

c. Lymph vessels serve to collect excess tissue fluid for transport into the veins before its return to the heart.

d. The lymphatic system transports tissue fluid, proteins, fats, and other elements to the general circulation.

e. Unlike the cardiovascular system, the lymphatic system is not a closed circuit.

2. Lymphatic fluid: Clear, watery, isotonic fluid resembling blood plasma.

3. Lymphatic vessels

a. Vessels similar to veins, but have thinner walls, more valves, and contain lymph nodes along the course of the vessels.

b. Lymphatic capillaries: Microscopic vessels composed of a single layer of endothelial cells.

c. Lacteals: Lymphatic capillaries that absorb fat in the villi of small intestine.

d. As lymphatic vessels increase in diameter, their walls become thicker and form three layers similar to blood vessels.

e. Semilunar valves: are present every few millimeters and increase as the vessels get smaller.

f. Right lymphatic duct: Lymph from upper right quarter of the body drains into right lymphatic duct, which then drains into the right subclavian vein.

g. Thoracic duct: Lymph from the rest of the body drains into the thoracic duct, which then drains into the left subclavian vein.

4. Circulation

a. Lymph moves in a rightward direction due to the number of valves.

b. Breathing and skeletal muscle motion cause a pressure gradient, which moves the lymph fluid through the vessels.

5. Lymph nodes

a. Lymph nodes are oval-shaped filters enclosed by a fibrous capsule.

b. Lymph nodes generally occur in clusters. The most significant of which include submental, submaxillary, cervical, cubital, axillary, and inguinal lymph nodes.

c. Lymph nodes filter and phagocytose toxins and microorganisms.

d. Site of final stages of maturation for some lymphocytes and monocytes.

6. Lymphatic tissues

a. Tonsils

(1) Located under the mucous membranes in the mouth and pharynx at the base of the tounge.

(2) Protect against bacteria invading the tissues between the nasal and oral cavities.

b. Thymus

(1) Pyramid-shaped organ located in the mediastinum; it is replaced by fat as one ages.

(2) Produces lymphocytes before birth.

(3) Shortly after birth, secretes thymosin which allows lymphocytes to develop into T-cells.

c. Spleen

(1) Oval-shaped organ located in the left hypochondriac region, below the diaphragm, above the left kidney, posterior to the stomach.

(2) Macrophages within the spleen phagocytose microorganisms from the blood.

(3) Site of final maturation of monocytes and lymphocytes.

(4) Macrophages phagocytose worn out RBC’s and platelets and recycle iron and globin.

(5) Serves as a blood reservoir in case of sudden blood loss.

1. Lymphopathies

a. Lymphedema: Abnormal accumulation of lymph especially in the extremities due to obstruction of lymph vessels resulting in swelling.

b. Hodgkin’s disease: Malignant neoplastic condition of the lymphatic system causing enlargement of lymphatic tissues.

c. Lymphosarcoma: Non-Hodgkin’s lymphoma that is a malignant disease of the lymphatic system.

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