The Lymphatic System

The fluid forced out of the blood plasma by hydrostatic pressure, which surrounds and bathes the body's cells and tissues.

Interstitial fluid

The force exerted by the blood against the wall of systemic capillaries, forcing blood plasma to leak out and bathe the surrounding tissues.

Hydrostatic pressure

Aggregated lymph nodes surrounding the opening to the respiratory and digestive tracts, which filter incoming air.

Tonsil

Bean-shaped structures that filter lymph and activate the immune system. There are 600 scattered throughout the body, with large clusters in cervical, mammary, axillary (armpit) and groin regions.

Lymph node

Gland that is a primary organ of the lymphatic system, found in the mediastinum, above the heart. Produces hormones thought to promote the maturation of T lymphocytes. Functional part is largest during childhood.

Thymus

Component of the spleen that removes worn out platelets and red blood cells, stores platelets, produces blood cells in the foetus.

Red pulp of spleen

A secondary organ of the lymphatic system located on left side of abdominal cavity below the diaphragm that primarily filters blood.

Spleen

Substance produced and released by the thymus, thought to promote the maturation of T lymphocytes.

Thymic hormone

Component of the spleen that carries out immune function and removes blood borne pathogens.

White pulp of spleen

Primary organ of the lymphatic system, responsible for the production of stem cells that eventually mature to form blood cells. Including red blood cells, white blood cells, and platelets.

Red bone marrow

A vessel that collects lymph from the right side of the head, neck, thorax, and right arm, and drains it into the bloodstream.

Right lymphatic duct

Specialized lymphatic capillaries located in the folds of the small intestine (villi) that absorb dietary fats and transport them to the bloodstream.

Lacteals

Also known as the thoracic duct, the largest lymphatic vessel in the body. It collects lymph from the left side of the head, neck, thorax, left arm, and lower body, and drains it into the bloodstream.

Left lymphatic duct

The fat-laden creamy-looking lymph fluid formed in the small intestine during digestion of fatty foods, absorbed and transported by lacteals.

Chyle

The pressure of a solution proportional to the concentration of the solute particles that cannot cross the membrane. For example, blood proteins can be too large to leave the capillaries, creating a gradient that pulls interstitial fluid back in.

Osmotic pressure

The body's non-specific response to injury or infection, characterized by redness, pain, heat and loss of function. Sets the scene for restoration and repair.

Inflammation

Fluid that circulates through the lymphatic system. It is derived from interstitial fluid and contains white blood cells, proteins, fats, and waste products. Main difference to interstitial fluid is the location, not composition.

Lymph fluid

The widening of the arterioles, which increases blood flow to tissues. It is a response to inflammation and helps deliver immune cells and nutrients to the affected area.

Vasodilation

An increase in blood flow to a specific area of the body, often in response to inflammation or injury. It helps deliver WBCs and chemicals. Provides extra heat, promoting metabolic rate of cells, and inhibiting migration of bacteria.

Hyperaemia

The movement of cells towards a chemical stimulus. It refers to the movement of WBCs towards areas of infection or inflammation.

Chemotaxis

The movement of WBCs out of the capillaries and into the surrounding tissues, due to increased permeability which occurs during inflammation. Allows defensive proteins such as antibodies and clotting factors to enter the injured area.

Emigration

Cells that engulf and digest pathogens, dead cells, and other debris. Examples are macrophages and neutrophils.

Phagocyte

A chemical released by mast cells that promotes vasodilation of local arterioles and increases the permeability of capillaries, as part of the inflammatory response to injury or infection.

Histamine

Key cell in inflammation, that releases histamine and other chemicals. Equivalent to the basophil cell in blood.

Mast cell