Lymphatic System and Axillary Lymph Nodes

Objectives Discuss Lymph, Lymphatic vessels, Lymphatic nodules and Lymphoid organs. Enlist functions of lymphatic System. Explain Lymphatic circulation. Discuss Main lymphatic channels. Describe the axillary lymph nodes

- The lymphatic system carries excess of the extracellular fluid back to the venous system. - This fluid is the result of filtration from capillaries. - The lymphatic system consists of : lymphatic vessels, lymph nodes, lymphatic ducts Spleen.

Lymph vessels - The lymph capillaries start as blind ended vessels that collect to form lymphatic vessels which are similar to the small veins (contain smooth muscles) but contain valves so it has beaded appearance. - In the intestine the lymphatics are called lacteals.

Superficial lymphatic vessels: * Present on the deep surface of the epithelium. * They run parallel to the superficial blood vessels of the skin. * They then join together to form larger vessels, which pierce the deep fascia to join the deeper vessels.

Deep lymphatic vessels: * They are deep to the deep fascia, parallel to the major blood vessels. * These are larger than the superficial vessels and have thick wall and valves.

2. Lymph Nodes Definition: - They are small oval bodies along the course of lymphatic vessels. Site: - They form groups especially in the neck, axilla, thorax, abdomen, and groin.

Structure: - It has two surfaces: a. Convex (outer) surface: - This surface receives afferent lymphatics. - Filtrations of its contents occur inside the lymph node. b. Concave (inner) surface: - It is called the hilum. This surface gives exit to an efferent lymphatic in addition to the presence of a small artery and vein.

Functions of lymph nodes: 1. Act as a filter as they prevent micro-organisms and certain substances from entering the blood stream. 2. Formation of lymphocytes. 3. Formation of antibodies. 4. In case of infection or malignancy, the lymph nodes become enlarged and change in consistency.

3. Lymphatic Duct a. Thoracic duct - There are two lymphatic ducts thoracic duct and right lymphatic duct. a. Thoracic duct - It begins in the cisterna chili in the abdomen (in front of the lumbar vertebrae) - It ascends through the posterior abdominal and thoracic walls (deviating to the left side). - It terminates at the junction of left subclavian and left internal jugular veins. - It drains lymph from all the body except the upper right quadrant.

b. Right lymphatic duct - It is much smaller in size. - It drains lymph from the upper right quadrant (right side of the head and neck, right upper limb, and right side of the chest) - It terminates at the junction of right subclavian and right internal jugular veins

Other lymphatic aggregations: They are seen in: - tonsils. - Mucous membrane of the intestine (Peyer's patches). - Spleen. - Thymus gland. All parts of the body possess lymphatics except: - C.N.S: its lymphatics is replaced by perivascular spaces that are connected with the subarachnoid space. - Bone marrow. On the other hand, certain parts of the body have a rich network of lymphatics e.g. dermis of the skin, mucous, and serous membranes and glands.

Axillary Lymph Nodes Divided into 5 groups: 1- Pectoral (Anterior) group: Site: on lower border of pectoralis minor. Afferents: from front of upper ½ of trunk, and breast. 2- Scapular (Posterior) group: Site: along subscapular artery Afferents: from back of upper ½ of trunk, and axillary tail of breast. 3- lateral group: Site: Along the axillary vessels. Afferents: From upper limb.

Axillary Lymph Nodes cont. 4- Infraclavicular LNs: Site: Below clavicle Afferents: from upper part of breast. 5- Apical group: Site: At the apex of axilla Afferents: from previous groups. Efferents form the subclavian trunk which enters the thoracic duct or right lymph trunk Applied note: Infection or malignancy in the upper limb or breast give swelling in the axilla due to involvement of axillary LNs.

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