The Lymphatic System

Lymph

Interstitial fluid after it enters a lymphatic vessel, clear, contains water, immune cells, and proteins

Fluid Recovery

Returns excess interstitial fluid and leaked plasma proteins to blood

Lipid Absorption

lymphatic capillaries called lacteals absorb dietary fats from the small intestine and transport them toward bloodstream

Lymphatic Capillaries

tiny, highly permeable vessels that collect excess tissue fluid.

Blind-ended

Lymphatic capillaries, they begin as closed-ended sacs in the tissueHi

Highly Permeable

lymphatic capillaries, can absorb large molecules and particles

Minivalves

lymphatic capillaries, overlapping endothelial cells form flap like openings that allow fluid to enter

Anchoring Filaments

lymphatic capillaries, attach the capillaries to surrounding connective tissue and help prevent collapse

Collecting Lymphatic Vessels

Have the same three basic tunics as veins. Have thinner walls than typical veins. Contain numerous internal valves to prevent back flow. Travel alongside other blood vessels

Lymphatic Trunks

Collecting vessels join together to form larger trunks, drain larger regions of the body

Right Lymph Duct

Drain lymph from the right side of the head, neck, thorax, and upper limbs. Empties into junction on the right internal jugular and subclavian veins

Thoracic Duct

Drain lymph from the left side of upper body and lower extremities

Skeletal Muscle Contractions

lymph movement, squeeze vessels, push lymph forward

Pressure Changes During Breathing

lymph movement, changes in thoracic pressure help draw lymph toward the chest

One-way valves

lymph movement, stop lymph from flowing backwards

Pulsations of Nearby Arteries

lymph movement, Compress adjacent lymphatic vessels

Smooth Muscle Contractions

lymph movement, Lymphatic vessel walls rhythmically contract

Movement of Surrounding Tissues

lymph movement, Helps compress vessels and move lymph

Diffuse Lymphatic Tissue

Scattered collections of immune cells within tissues and organs

Mucosa-Associated Lymphoid Tissue (MALT)

associated with mucus membranes, found in digestive, respiratory, and urogenital tracts, includes tonsils, peers patch, and lymph tissue in appendix

Red Bone Marrow

Lymphatic organ, produces blood cells, B-cell maturation, hematopoietic stem cells

Thymus

Lymphatic organ, T-cell maturation, superior to heart, has a connective tissue capsule that sends extensions called trabeculae into the organ, dividing it into lobule

Cortex

region of thymus lobule, Dense population of developing T cells and supporting cells

Medulla

region of thymus lobule, Contains fewer developing T cells, reticular cells, dendritic cells, and thymic corpuscles

Hematopoiesis

the production of blood cells

Lymph Nodes

Filter lymph to remove pathogens, debris, and foreign substances. Provide a site where B and T cells can be activated. Support immune responses against antigens carried in lymph.

Capsule

lymph node structure, Outer connective tissue covering

Trabeculae

lymph node structure, Extensions of the capsule into the node

Cortex

lymph node structure, Outer region containing lymphoid follicles

Germinal Centers

lymph node structure, Regions in activated secondary follicles where B cells proliferate and develop

Medulla

lymph node structure, Inner region containing B cells, T cells, plasma cells, and supporting structures

Lymph Sinuses

lymph node structure, Channels through which lymph flows inside the node

Afferent lymphatic vessels

lymph node structure, Carry lymph into the node

Efferent lymphatic vessels

lymph node structure, Carry lymph out of the node

Primary follicles

Generally contain inactive or naive B cells

Secondary follicles

Develop germinal centers during an immune response, where activated B cells proliferate and undergo further development.

The Spleen

Filters blood for pathogens. Removes old or damaged red blood cells. Supports lymphocyte proliferation and immune responses. Stores platelets and monocytes that can be released into circulation.

Red pulp

Region of spleen, Removes worn-out red blood cells and helps eliminate blood-borne pathogens

White pulp

region of spleen, Contains lymphocytes and macrophages around branches of the splenic artery; this is where immune surveillance and responses occur

Tonsils

patches of lymphatic tissue located near the entrance to the pharynx. They help detect pathogens entering through the mouth and nose.

Pharyngeal tonsil

One; also called the adenoids

Palatine tonsils

A pair, commonly called the tonsils.

Lingual tonsils

Numerous collections of lymphatic tissue near the base of the tongue.large clusters of lymphoid follicles in the small intestine, especially the ileum

Peyer’s Patch

large clusters of lymphoid follicles in the small intestine, especially the ileum. Helping prevent bacteria from breaching the intestinal wall. Supporting immune responses against intestinal pathogens. Helping generate memory lymphocytes for long-term immunity.