Capillary Dynamics and the Lymphatic System

This set covers capillary exchange pressures and the anatomy, function, and cell types of the lymphatic system.

Hydrostatic pressure (HP)

The force exerted by a fluid pressing against a wall.

$$HPC$$

Capillary blood pressure or filtration pressure; it is $35\,mmHg$ at the arterial end and $16\,mmHg$ at the venous end.

$$HPIF$$

Hydrostatic pressure of the interstitial fluid, which is $0\,mmHg$ due to excess fluid being reclaimed by lymphatic vessels.

Osmotic pressure (OP)

Pressure created by the presence of large, non-diffusible molecules (plasma proteins) that draw water towards them.

$$OPC$$

Capillary osmotic pressure which is equal to $26\,mmHg$.

$$OPIF$$

Interstitial fluid osmotic pressure which is equal to $5\,mmHg$.

Lymphatic vessels

Components that transport excess fluid from interstitial spaces and return it to the venous system.

Lymphatic capillaries

Blind-ended vessels where fluid moves in one direction; they occur everywhere except bones, teeth, bone marrow, and the central nervous system.

Lymph

The name for the fluid once it enters the lymphatic capillaries.

Lacteals

Specialized lymphatic capillaries located in the villi of the intestinal mucosa.

Chyle

Whitish, fatty lymph found in the lacteals.

Cisterna chyli

An enlarged sac that marks the beginning of the thoracic duct and collects lymph from the lumbar and intestinal trunks.

Thoracic duct

Collects lymph from the left side of the head, neck, thorax, left arm, abdomen, and legs; empties at the juncture of the left subclavian and left internal jugular veins.

Right lymphatic duct

Collects lymph from the right side of the head, neck, thorax, and right arm; empties at the juncture of the right subclavian and right internal jugular veins.

T cells

Activated lymphocytes that manage the immune response and some directly attack antigens.

Foreign Antigens

Non-self substances the body perceives as foreign, such as bacteria-toxins, viruses, cancer cells, and mismatched RBCs.

B cells

Lymphocytes that produce plasma cells, which in turn produce antibodies.

Antibodies

Produced by plasma cells to help immobilize antigens until they can be destroyed.

Lymph nodes

Organs clustered along lymph vessels that filter lymph and monitor for the presence of antigens.

Tonsils

Partially encapsulated lymph nodules located in the pharynx.

Peyer’s patches

Aggregations of nodules scattered throughout the ileum of the small intestine.

Thymus

An organ in the thorax that secretes thymosin and is the site for the differentiation of lymphocytes into T cells.

Thymosin

A hormone secreted by the thymus that stimulates T cells after they leave the organ.

Spleen

The largest lymphatic organ; it filters blood, serves as a RBC graveyard, and is a site of RBC production in a fetus.

White pulp

Splenic nodules containing a large number of lymphocytes.

Red pulp

Spaces of lobules in the spleen containing many RBCs as well as lymphocytes and macrophages.