Lymphatic

The lymphatic system plays a crucial role in the immune response and the maintenance of fluid balance in the body.
Key components include lymphatic capillaries, vessels, trunks, ducts, and various lymphatic organs.

Definition: Thin-walled vessels that absorb interstitial fluid and lead to lymphatic vessels.
Structure: Composed of endothelium and basement membrane; contain anchoring filaments that help maintain their shape.
Function: Capture interstitial fluid, which is then transported through lymphatic vessels.

Categories of Lymphatic Vessels:
- Superficial lymphatic vessels: Located in the skin and mucous membranes.
- Deep lymphatic vessels: Accompany deep veins of the body.
Lymphatic Trunks: Major vessels that drain lymph from various regions:
- Jugular Trunks: Drain lymph from the head and neck.
- Subclavian Trunks: Drain lymph from the upper limbs.
- Bronchomediastinal Trunks: Drain lymph from the thorax.
- Intestinal Trunks: Drain lymph from the digestive organs.
- Lumbar Trunks: Drain lymph from the lower limbs and pelvic organs.
Lymphatic Ducts:
- Right Lymphatic Duct: Drains lymph from the right arm, right side of the head and thorax into the right venous angle.
- Thoracic Duct: Larger duct that drains lymph from the rest of the body into the left venous angle. Begins at the cisterna chyli.

Definition: Lymphatic organs that participate in the immune response but lack a complete capsule.
Components include:
- Tonsils: Guard against pathogens entering through the oral and nasal cavities.
- Lymph Nodes: Distributed throughout the body and filter lymph, containing clusters of lymphocytes.
- Characteristics: Ranges from 1 mm to 25 mm in size; approximately 500 to 700 lymph nodes in the body; commonly found in clusters.
- MALT (Mucosa-Associated Lymphatic Tissue): Includes lymphatic nodules in the gastrointestinal tract, particularly in the small intestine (Peyer’s patches).

Red Bone Marrow: Source of all blood cells, including lymphocytes.
Thymus: Site for T-lymphocyte maturation and differentiation.
- Microanatomy: Includes a capsule, lobules, a cortex, and a medulla.

Components include:
- Cortex and Medulla: Cortex contains lymphatic nodules with germinal centers; medulla contains medullary cords and sinuses.
- Afferent and Efferent Vessels: Lymph enters through afferent vessels and exits through efferent vessels.
- Hilum: Area through which blood vessels and nerves enter and exit the lymph node.

Function: Largest lymphatic organ; filters blood, removes old red blood cells (RBCs), and serves as a platelet reservoir.
Characteristics: Located in the left upper quadrant of the abdominal cavity, surrounded by a connective tissue capsule, divided into red and white pulp:
- Red Pulp: Phagocytizes old RBCs and platelets.
- White Pulp: Contains lymphocytes responsible for filtering blood and immune response.

Types of Tonsils:
- Palatine: Located on either side of the oropharynx; the most commonly removed during tonsillectomy.
- Lingual: Located at the base of the tongue.
- Pharyngeal (Adenoids): Located in the nasopharynx.
Functions: Protect respiratory and digestive tracts by capturing pathogens.

Lymphatic Vessels: Drain excess interstitial fluid and transport it back to the bloodstream through lymphatic ducts.
Lacteals: Specialized lymphatic capillaries in the intestinal villi that absorb dietary fats and fat-soluble vitamins (A, D, E, K) from the gastrointestinal tract.

Fluid Balance: Transports interstitial fluid back into the circulatory system.
Immune Function: Lymph nodes, spleen, and MALT help protect the body against pathogens.
Transport of Lipids: Lacteals absorb lipids from the digestive tract and transport them to the bloodstream.