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Class notes

Functions of lymphatics

  • Removing excess tissue from periphery
  • Monitoring fluid for infective material
  • Production of immune cells
  • Because of this, the lymphatics are prone to invasion by tumour ells

Histology of lymph nodes

  • Usually the size of a pea
  • Afferent lymphatic vessels that penetrate the capsule
  • Outer cortex
  • Inner medulla
  • Hilum; where the efferent vessels leave
  • Small arteries and veins entering each lymph node
  • Cortex is made up of follicles, in the middle of which is the germinal centre containing B lymphocytes and macrophages, outside of which is the marginal zone, surrounded by T lymphocytes; in the subcortical region are macrophages and plasma cells
  • Note capsule, subcapsular sinus, cortical sinus, trabecula, medullary cord

Appearance in pathology

  • Infection
    • Overlying skin is red
    • Painful
    • Swollen
  • Tumour
    • May not be red or painful at all
    • Capsular rupture may have cemented the LN to surrounding tissue (less mobile than normal)

Lymph node location

  • Head and neck = 60-70 lymph nodes (felt clinically)
  • Upper limb/superior thorax: 30 LNs
  • Deep thorax: 100 lymph nodes
  • Deep abdomen and pelvis: ~230 lymph nodes
  • Lower abdominal wall, perineum and lower limb: ~20 lymph nodes

Lymph channels

  • Thoracic duct - a few mm across (largest in the body)
    • Starts in upper abdomen (from a dilated sac - the cisterna chyli in 20% of people; most people have a collection of individual lymph channels that join together to form the thoracic duct)
    • Runs up the posterior mediastinum, deviating to the left, and drains into the junction of the Lt internal jugular vein and Lt subclavian vein
    • Intended to return tissue fluid back into the venous CVS (because more blood goes out in arteries than returns in veins)
  • Rt lymphatic duct (for the right upper limb and right side of head/neck); joins into the right internal jugular vein and right subclavian vein, upper right chest
  • Note the jugular trunk, subclavian trunk and bronchomediastinal trunk on each side (that each drain into the thoracic duct and right lymphatic duct)
  • Intestinal trunks for each of the fore- mid- and hindgut (coeliac, sup. mesenteric and inf. mesenteric)
  • Lumbar lymph trunks are arranged alongside the aorta
  • Common iliac trunk, external iliac trunk and internal iliac trunk

Lymphatic Drainage of the Head & Neck

  • Sternocleidomastoid muscle is a line of boundary to the superficial and deep nodes
  • Occipital lymph nodes
  • Retroauricular lymph nodes
  • Parotid lymph nodes
  • Buccal lymph nodes
  • Submental lymph nodes
  • Submandibular lymph nodes
  • Superficial cervical lymph nodes (top of SCM)
  • Upper deep cervical LNs
  • Lower deep cervical LNs
  • Drains from superficial to deep and from peripheral to proximal (from top of head to the neck) (e.g. eyebrow --> parotid and buccal --> superficial --> deep --> etc)

Axillary lymph nodes

  • Recall axilla
  • Apical group, central group, anterior group (close to pec minor), posterior group (close to subscapularis), lateral group
  • Anterior/pectoral, lateral and posterior groups all drain toward central group
  • Then it drains to apical group
  • Then to subclavian trunk, then right lymphatic duct/thoracic duct, then veins
  • Breast drainage: laterally to axillary nodes. Medially to internal thoracic nodes (on the inside, behind the costal cartilages alongside the sternum)
  • Axillary tail hooks around pectoralis minor; drains via retropectoral route to pectoral lymph nodes
  • Tumour cells can spread from one breast to the other without going through the lymph system
  • Transpectoral route = penetrate pectoral muscles

Lymph drainage of the thorax

  • There are large clusters of lymph nodes alongside airways
  • There are nodes associated with the body wall (parietal) and also those associated with viscera (largest group)
    • Visceral group usually alongside airways
  • See illustration of lung lymph nodes
  • There aren't very many LNs in the upper limb (there are some in the epitrochlear position; near the ulnar nerve)
  • Lower limb: inguinal lymph nodes

Large bowel lymph nodes

Review AEA bowel arteries

  • Lymphatics are associated with main venous drainage, which is associated with the arteries
  • There are groups alongside the main branches of SMA and IMA
  • Paracolic LNs are on mesenteries where they attach to the bowel
  • Intermediate LNs are on branch of Lt colic artery
  • Inferior mesenteric LNs

Pelvic lymphatics

  • Logically arranged alongside the major vessels of the pelvis
  • Common iliac LNs
  • Internal iliac LNs
  • External iliac LNs
  • Sacral LNs (in front of sacrum)
  • These drain all organs you might expect, with exceptions
    • External iliac LNs= lower limb
    • Internal iliac LNs = pelvic organs (uterus, upper vagina, bladder, etc)
    • Sacral LNs = drain structures at the back of the pelvic cavity (some from reproductive, largely from gluteal region, and muscles of pelvic floor)

Official notes

  • The lymphatic system consists of:
    • lymphatic vessels (or 'lymphatic')
    • lymphoid tissue, which includes circulating lymphocytes as well as aggregates of lymphocytes and their associated cells. The latter are found in many sites e.g. spleen, lymph nodes, thymus.
  • Lymphatic tissue my be intimately associated with the lymphatic vessels, e.g. chains of lymph nodes along the lymphatic vessels; or may be unconnected with lymphatic channels e.g. the spleen, bone marrow and thymus.
  • The functions of the lymphatic system are varied:
    • transport of tissue fluid formed in the capillary bed
    • the removal by mononuclear phagocytic series cells of cells debris and foreign matter (e.g. bacteria) and the prevention of bacterial and foreign material from entering the blood stream.
    • production of lymphatic and control of the immune responses

Lymphatic vessels

  • Lymphatic capillaries form plexuses in tissue spaces and have much wider meshes than those of adjacent blood capillaries. They often begin as dilated lymphatics with blind endings. The endothelium of lymphatic capillaries is permeable to much larger molecules than blood capillaries, as well as cell debris, bacteria and colloidal material.
  • Lymph from most tissues is clear and colourless, but from the small intestine it is milky due to the absorption of fat globules (chylomicrons) and is called chyle. The terminal lymph capillaries from this region are called lacteals. Lymphatic capillaries are absent from avascular structures (e.g. epidermis, cornea, articular cartilage) and from the central nervous system and bone marrow.
  • Lymphatic capillaries join into larger vessels which pass to local lymph nodes. These are arranged largely in regional groups. There are occasional exceptions to this in that lymph vessels of the thyroid gland, oesophagus, coronary and triangular ligaments of the liver drain directly into the thoracic duct without passing through regional nodes.
  • Since lymphatic vessels are usually associated with arteries and veins during development, it is often found that the deep lymphatic channels (trunks) in the adult accompany the other vessels.
  • Several factors aid the flow of lymph from tissue spaces to lymph nodes and finally to the venous bloodstream:
    • 'filtration pressure' in tissue spaces, generated by filtration of fluid under pressure from the haemal capillaries
    • contraction of neighbouring muscles compresses the lymph vessels, moving lymph in the direction determined by the arrangement of valves
    • pulsation of adjacent arteries
    • respiratory movements and the low blood pressure in the brachiocephalic V. during inspiration
    • smooth muscle in the walls of lymphatic trunks is most marked proximal to their valves. Stimulation of sympathetic nerves accompanying them causes their contraction. Pulsatile contractions in the thoracic duct are known to occur also.

Lymph nodes

  • There are several important roles performed by lymph nodes which we need to consider:
    • provision of a labyrinth of channels of large surface area and volume through which lymph slowly percolates
    • trapping of foreign material in lymph nodes and exposure to nodal macrophages
    • production of lymphocytes and a pool of stem cells to become antibody-producing B lymphocytes and mature T lymphocytes
    • interaction between antigen-bearing mononuclear phagocytes and lymphocytes to produce immune responses.
    • re-entry of blood-borne lymphocytes into lymphatic channels and thence to the haemal circulation
    • humoral antibody production, its addition to lymph and ultimately the blood
  • A normal young adult body contains about 400 to 450 lymph nodes. The limbs and superficial body wall have relatively few. The arm and superficial thoraco-abdominal wall (down to the umbilicus) contain about 30 nodes. The leg, superficial buttock, infraumbilical abdominal wall and perineum contain only about 20 nodes. The head and neck carry about 60 to 70 nodes, while the remainder is divided between the thorax (up to 100 nodes in deep walls and contents) and abdomen and pelvis (230 or more nodes in deep walls and contents).

Major lymphatic channels in the body

The thoracic duct

  • This is the largest lymphatic channel in the body (38 to 45 cm in length) and extends from the 1st lumbar vertebra to the root of the neck. It drains lymph from the left arm, left neck and head, left thorax, left upper abdomen (to umbilicus), both sides of the abdomen below the umbilicus and both lower limbs. It arises either from the confluence of several lymph channels on the posterior abdominal wall, or in some individuals these lymph channels drain into a dilated sac known as the cisterna chyli, which lies anterior to the 1st and 2nd lumbar vertebrae. The thoracic duct then passes through the aortic opening in the diaphragm (TV 12), ascends in the posterior mediastinum to the right of the midline between the descending aorta (to its left) and the azygos vein (to its right). When it reaches the level of the TV5 it inclines to the left until finally terminates either into the junction of the left internal jugular and subclavian Vs or one of those veins only. In 50% of people it has a terminal dilatation or ampulla. Before it terminates it receives the Lt jugular (draining lymph from left head and neck) and Lt subclavian (from left arm) trunks.

The right lymphatic duct

  • On the right side of the body, lymph from the right head and neck, right arm and right thorax and abdomen (down to the convex surface of the liver) are drained by the Rt jugular, Rt subclavian and Rt bronchomediastinal trunks respectively. In 20% of people these join into a single channel, the Rt lymphatic duct, which drains into the junction of the Rt internal jugular and Rt subclavian Vs or each of these veins separately.

Lymphatic drainage of the head and neck

  • Nodes in the head and neck may be divided into a terminal group related to the carotid sheath (deep cervical), and outlying groups. The deep cervical nodes drain into the jugular trunk which enters the thoracic duct on the left and the right lymphatic duct or jugulo-subclavian junction on the right.
    • The deep cervical lymphatic nodes are divided into superior and inferior groups. The superior group lie adjacent to the upper internal jugular vein, usually deep to the sternomastoid muscle. The inferior group lies adjacent to the lower internal jugular V.
    • Superficial groups
      • In the head: occipital, retroauricular (mastoid), parotid, buccal (facial)
      • In the neck: submandibular, submental, anterior cervical, superficial cervical.
      • Efferents from these nodes drain into the deep group

Lymphatic drainage of the upper limb

  • There are lymph nodes located around the elbow (trochlear nodes) but the most important groups of nodes in the upper limb are located in the axilla. These receive lymph from the breast, axilla, lateral chest wall and upper limb. There are 5 principal groups in the axilla: pectoral, subscapular, humeral, central and apical.
    • Pectoral (anterior): 3 to 5 nodea on the medial wall along the lateral thoracic vein and the inferior border of the pectoralis minor. They drain anterior thoracic wall, including most of the breast.
    • Subscapular (posterior): 6 or 7 nodes that lie along the posterior axillary fold and the subscapular blood vessels. They drain posterior aspect of the thoracic wall and scapular region.
    • Humeral (lateral): 4 to 6 nodes that lie along the lateral wall of the axilla, medial and posterior to the axillary vein. These are the main drainage of the upper limb.
    • Central: 4 to 6 nodes that lie along the lateral wall of the axilla, medial and posterior to the axillary vein. The central nodes receive lymph from other axillary nodes (pectoral, subscapular, humeral).
    • Apical: situated in the apex of the axilla along the medial side of the axillary vein and the 1st part of the axillary artery. They receive lymph from all other axillary nodes. Efferent vessels drain into either right lymphatic duct or thoracic duct

Lymphatic drainage of the breast

  • Most lymph (>75%) especially from the upper lateral quadrant, drains to the axillary lymph nodes, initially to the anterior or pectoral nodes. However, some lymph may drain directly to the other axillary nodes or even the inter-pectoral, deltopectoral, supraclavicular or inferior cervical nodes.
  • Most of the remaining lymph, particularly from the medial quadrants, drains to the parasternal lymph nodes or to the opposite breast, whereas lymph from the inferior quadrants may pass deeply to the abdominal lymph nodes (subdiaphragmatic inferior phrenic lymph nodes).

Lymphatic drainage of the thorax

  • Lt and Rt bronchomediastinal trunks drain into the thoracic duct and the right lymphatic duct respectively
  • Parietal nodes:
    • diaphragmatic
    • parasternal
    • intercostal
  • visceral nodes
    • pulmonary
    • bronchopulmonary
    • tracheobronchial (superior and inferior)
    • paratracheal
    • mediastinal

Lymphatic drainage of the abdomen and pelvis

  • The lymph drainage of the abdomen is mainly via thoracic duct
  • Three terminal groups of lumbar nodes are identified:
  1. preaortic, consisting of:
    • coeliac nodes, draining the foregut structures
    • superior mesenteric nodes, draining midgut structures (nodes in the mesenteries)
    • inferior mesenteric nodes, draining hindgut structures (nodes in the mesenteries)
    • These are associated with the appropriate artery. Efferents from these nodes form intestinal trunks, which enter the abdominal confluence of the lymph trunks and thence the thoracic duct.
  2. lateral aortic, efferents of which form paired lumbar trunks. Lymphatic vessels from the kidney, suprarenal glands, abdominal ureter, posterior abdominal wall, testis and ovary, uterus and uterine tube all drain directly to the lateral aortic nodes. These nodes also ultimately drain the lower limb. Several other named groups of nodes are known: common iliac nodes, external iliac nodes, internal iliac nodes.
  3. retroaortic nodes drain posterior abdominal wall. They may actually be peripheral nodes of the lateral group.