Lymphatic System

Returns excess interstitial fluid and proteins to the bloodstream, transports dietary lipids from the small intestine, and supports immune defence against pathogens.

Inside the intestinal villi, where they absorb dietary fats and transport them as chyle.

Lymph, lymphatic vessels, lymph nodes, and lymphoid organs and tissues.

Usually clear or pale yellow; intestinal lymph rich in absorbed fats, called chyle, appears milky white.

Hydrostatic pressure pushes fluid across a membrane, whereas oncotic pressure is the osmotic pulling force generated by proteins that draws water towards the compartment containing them.

Plasma proteins, especially albumin; dissolved ions contribute to osmotic pressure but usually have a smaller effect on the oncotic pressure difference across capillary walls.

Interstitial fluid that enters lymphatic capillaries and is transported through the lymphatic system.

One-way valves

Lymphatic capillaries → collecting lymphatic vessels → lymph nodes → lymphatic trunks → lymphatic ducts → venous circulation.

They filter lymph, trap foreign particles and antigens, and provide sites where immune cells recognise antigens and initiate immune responses.

A parasitic disease caused by filarial nematode worms that damage or obstruct lymphatic vessels, potentially causing lymphoedema and elephantiasis.

Mosquitoes, which transmit infective filarial larvae during blood feeding.

Persistent swelling caused by impaired lymphatic drainage and accumulation of protein-rich fluid in tissues.

They may enlarge due to immune-cell proliferation and increased immune activity

The efferent lymphatic vessel exits, and blood vessels enter and leave the node.

Afferent lymphatic vessels enter and deliver lymph to the node.

Superficial lymph nodes, such as cervical, axillary, and inguinal nodes.

Into deeper collecting lymphatic vessels, which carry lymph towards regional lymph nodes and larger lymphatic trunks.

Cervical, axillary, and inguinal lymph nodes.

The sternocleidomastoid (SCM) muscle.

Along the external jugular vein, superficial to the sternocleidomastoid muscle.

Deep to the sternocleidomastoid muscle, along the internal jugular vein.

They are often tender, mobile, and soft or firm, although consistency varies with the cause.

They may be firm or hard, non-tender, and fixed to surrounding tissues, although malignant nodes can also be mobile or tender.

Secondary cancer involving cervical lymph nodes, often originating from a primary tumour in the upper aerodigestive tract.

Squamous cell carcinoma of mucosal surfaces of the head and neck, although other cancers can also metastasise to cervical nodes.

An operation that classically removes cervical lymph node groups I–V, the internal jugular vein, sternocleidomastoid muscle, and spinal accessory nerve (cranial nerve XI); modified procedures preserve one or more of these structures.

Surgical removal of breast tissue. The structures removed depend on the procedure; a simple mastectomy usually removes the breast and nipple–areolar complex, while the pectoralis major is generally preserved.

A tracer, such as a radioactive substance and/or blue dye, is injected near the tumour; lymphatic drainage identifies the first node or nodes likely to receive tumour cells.

Medial to the femoral vein, deep to the fascia lata, near the femoral canal.

Along the terminal part of the great saphenous vein.

Just inferior to the inguinal ligament, roughly parallel to it.

Primarily to the para-aortic (lumbar) lymph nodes, reflecting the testes' embryological origin in the posterior abdominal wall.

Primarily to the superficial inguinal lymph nodes.

No; they are generally too deep to be felt during routine examination.

Along major vessels, including the abdominal aorta, inferior vena cava, and iliac vessels.

Internal and external iliac nodes → common iliac nodes → lumbar (para-aortic and paracaval) nodes.

Through intestinal lymphatic vessels and mesenteric nodes to the intestinal lymphatic trunks, which usually drain into the cisterna chyli and thoracic duct.

They usually converge at the cisterna chyli, which continues as the thoracic duct; anatomical variation occurs.

A large lymphatic vessel formed by the convergence of collecting vessels that drains a major body region into a lymphatic duct.

They drain towards the venous angles, where the internal jugular and subclavian veins meet; drainage may be directly into the veins or through a lymphatic duct.

Most of the body: both lower limbs, the abdomen, the left thorax, left upper limb, and left side of the head and neck.

The right upper quadrant of the body: the right side of the head and neck, right upper limb, and right thorax.

Interstitial fluid enters lymphatic capillaries, travels through collecting vessels and lymph nodes, then through lymphatic trunks and ducts before returning to the bloodstream at the venous angles.

The thoracic duct, which drains most of the body.

A left supraclavicular lymph node that may enlarge due to metastatic malignancy, classically from an abdominal or gastrointestinal primary tumour.

Accumulation of chyle, a lipid-rich lymphatic fluid, in the pleural cavity, often due to thoracic duct injury or obstruction.

The spleen.

Filters blood, removes old or damaged red blood cells, recycles iron, supports immune responses to blood-borne antigens, and stores platelets.

It lies in the anterior superior mediastinum behind the sternum and undergoes age-related involution, with much of its functional tissue replaced by fat.

They sample antigens entering through the mouth and nose and support local immune responses in the upper respiratory and digestive tracts.

They are named by anatomical location: palatine tonsils, lingual tonsils, pharyngeal tonsil (adenoids), and tubal tonsils.