Lymphatic System Overview

Lymphatic System Overview

• The lymphatic system protects the body against foreign materials.
• It assists in circulating body fluids between cells and the bloodstream.
• It transports dietary fats.
• It consists of lymphatic vessels, lymph, lymph nodes, tonsils, spleen, and the thymus gland.

Lymph

• Lymph is derived from tissue fluid.
• It contains more white blood cells than plasma.
• Lymph enters lymph nodes through afferent lymphatic vessels.
• Lymph flows through the node in one direction.
• Lymph flows through sinuses in the cortex and medulla of a lymph node.
• Lymph exits the lymph node through efferent lymphatic vessels.
• Lymph must be returned to the bloodstream to maintain blood volume and pressure.

Lymphatic Vessels

• Lymphatic vessels resemble veins but have thinner walls and more valves.
• Lymph movement is facilitated by vessel constriction, skeletal muscle pumps, and respiratory pumps.
• Lymph flows, at intervals, into lymph nodes along the vessels.
• Lymphatic vessels unite to form lymph trunks.

Lymph Trunks

• Lymph trunks are formed by uniting lymphatic vessels.
• They are large tubes that empty lymph into lymphatic ducts.

Lymphatic Ducts

• Lymph empties into two ducts: the thoracic duct (left lymphatic duct), and the right lymphatic duct.
• Lymph from these ducts enters the bloodstream via the left subclavian vein and the right subclavian vein.

Thoracic Duct

• The thoracic duct (left lymphatic duct) is about 38-45 cm long.
• It begins as a dilation called the cisterna chyli.
• It is the main collecting duct of the lymphatic system.
• It receives lymph from the lower body and upper left quadrant.
• It empties into the left subclavian vein.

Right Lymphatic Duct

• The right lymphatic duct is about 1.5 cm long.
• It receives lymph from the upper right quadrant.
• It empties into the right subclavian vein.

Lymph Nodes

• Lymph nodes are oval or bean-shaped masses of lymphatic tissue.
• They aid in defense and white blood cell formation.
• They are located along the length of lymphatic vessels.
• They are scattered throughout the body, usually in clusters.

Major Lymph Nodes

• Cervical nodes are located in the neck, filtering lymph from the head and neck.
• Axillary nodes are located in the armpits, filtering lymph from the hand, arm, and breast.
• Inguinal nodes are located in the groin, filtering lymph from the lower extremities and external genital organs.
• Mesenteric nodes are located in the abdominal peritoneum, aiding in infection control after abdominal surgery and filtering lymph from the abdominal cavity.

Metastasis

• Metastasis is the process by which bacteria or body cells spread from one body part to another, through lymphatic or circulatory systems.
• Cancer cells often migrate to nearby nodes (e.g., breast cancer to axillary nodes).

Tonsils

• Tonsils are aggregations of large lymphatic nodules embedded in mucous membranes.
• They are located beneath the epithelium of the pharynx and oral cavities.
• They protect nasal and oral cavities.
• Three types of tonsils include nasopharyngeal, palatine, and lingual tonsils.

Nasopharyngeal Tonsils

• Also called adenoids, these tonsils are located behind the nose, on the roof of the posterior wall of the pharynx, and the posterior opening of the nasal cavity.

Palatine Tonsils

• Commonly referred to as just "tonsils."
• Located in the back of the mouth and lateral walls of the pharynx.
• Frequently removed through tonsillectomy.

Lingual Tonsils

• Found at the base of the tongue.
• Act as a first line of defense against external threats.

Spleen

• The spleen is the largest lymphatic organ, located in the upper left abdominal quadrant, between the stomach fundus and the diaphragm.
• It resembles a large lymph node and filters blood.

Spleen Structure

• The spleen is covered by a capsule.
• The hilum is a depression on the medial surface of the spleen, where nerves, arteries, veins, and lymphatic vessels enter and exit.
• Trabeculae are extensions of the spleen capsule that form partitions within the spleen.
• The spleen's tissue/substance (pulp) is divided into the white and red pulp.

White Pulp

• White pulp consists of lymphatic tissue and mostly lymphocytes, arranged around central arteries.

Red Pulp

• Red pulp consists of venous sinuses filled with blood, and cords of splenic tissue; it contains red blood cells, macrophages, lymphocytes, plasma cells, and granulocytes.

Spleen Functions

• Phagocytosis of bacteria, worn-out or damaged red blood cells, and platelets.
• Blood storage and release (e.g., during hemorrhage).
• Immune function as a site for B cell proliferation into plasma cells.
• Does not filter lymph (no afferent lymphatic vessels or lymph sinuses).

Thymus Gland

• The thymus gland is a bilobed organ in the upper part of the chest, along the trachea, inferior to the thyroid gland and posterior to the sternum.
• It's the largest and most active during the prenatal period and infancy.
• It decreases in size after puberty.

Thymus Gland (cont.)

• It's composed of lymphatic tissue.
• It's subdivided into lobules.
• Immature T cells originate in bone marrow and migrate to the thymus via blood.
• Within the thymus, cells mature into T cells and then are released into circulation.
• Thymic hormones aid in T cell maturation.

Thymus Removal

• Removing the thymus (thymectomy) can decrease T-cell production, potentially increasing susceptibility to acute infections.

Spleen Removal

• Removing the spleen (splenectomy) can be compensated by function in other organs (e.g. liver and bone marrow).
• Removal can also increase susceptibility to diseases.

MALT (Mucosa-Associated Lymphoid Tissue)

• MALT is mucosa-associated lymphatic tissue.
• It's the infiltration of mucosa by a large number of lymphocytes.
• Peyer's patches of the small intestine are an example of MALT.

Explore the crucial functions and components of the lymphatic system, which plays a vital role in protecting the body and maintaining fluid balance. This quiz covers the structure and flow of lymph, as well as the organization of lymphatic vessels and nodes.