Lymphatic System Overview

Transports fluids back to blood, defends against diseases

Clear fluid similar to plasma, contains pathogens

Smallest lymphatic vessels, absorb tissue fluid

Carry lymph, one-way to heart, no pump

Filter lymph, contain lymphocytes to fight pathogens

Excess tissue fluid accumulation

Drains lymph from right arm, head, and upper body

Drains lymph from rest of the body to left subclavian vein

Valves, similar to those in veins, prevent backflow in lymphatic vessels, ensuring unidirectional movement of lymph towards the heart.

Larger lymphatic vessels are composed of three layers: tunica interna (containing endothelium and valves), tunica media (smooth muscle for contraction), and tunica externa (protective outer layer).

Lymph flows under pressure gradients similar to venous return, relying on rhythmic contractions of lymphatic vessels, skeletal muscle movement, and pressure changes during breathing.

Lymph nodes are bean-shaped structures that filter lymph fluid, containing lymphocytes (immune cells) to defend against pathogens.

Lymph nodes contain natural killer cells, macrophages, and lymphocytes, all of which play a role in destroying pathogens and infected cells.

The cortex of a lymph node is the outer region and contains a high concentration of lymphocytes, which are responsible for directly killing pathogens.

The medulla, the inner region of a lymph node, is rich in macrophages, cells that engulf and destroy pathogens.

Lymph travels from lymphatic capillaries to collecting vessels, then through lymph nodes for filtration, before flowing through larger collecting vessels and into lymphatic ducts, finally entering the subclavian veins and merging with the bloodstream.