The lymphatic (lymphoid) system is essentially a drainage system, which is concerned with return of a fluid called "lymph" back to the blood stream.

It consists of lymphatic tissues and lymphatic vessels. Its components are not in continuous order, but are scattered

throughout the body and it services almost all regions.

Lymphatic tissues are a type of connective tissue that contains large numbers of lymphocytes.

Lymphatic tissue is organized into the following organs: the thymus, lymph nodes, spleen, and lymphatic nodules.

Lymphatic tissue is essential for the immunologic defenses of the body against bacteria and viruses.

Lymphatic vessels are tubes that assist the cardiovascular system in the removal of tissue fluid from the tissue spaces of the body; the vessels then return the fluid to the blood.

Lymphatic vessels are found in all tissues and organs of the body except: Central nervous system. Eyeball & internal ear. Epidermis of skin. Cartilage & bone.

Lymph vessels are either superficial or deep: Superficial lymphatics: more numerous than veins in the

subcutaneous tissue and anastomosing freely, converge toward and follow the venous drainage.

These vessels eventually drain into deep lymphatics that accompany the arteries and also receive the drainage of internal organs.

Both superficial and deep lymphatics traverse lymph nodes as they course proximally, becoming larger as they merge with vessels draining adjacent regions.

The lymphatics that carry lymph to a lymph node are referred to as afferent vessels; those that transport it away are efferent vessels.

The larger lymphatics enter large collecting vessels, called lymphatic trunks, which unite to form either the right lymphatic duct or the thoracic duct: Right lymphatic duct. Thoracic duct.

LYMPH VESSELS

Functions of the lymphatic system

The functions of the lymphatic system are just as varied as its locations. These functions fall into 3 categories:

Fluid balance: The small lymphatic capillaries pick up excess interstitial fluids and

proteins, which accumulate in the tissue spaces. These capillaries then drain into larger vessels, which return these materials to the venous system near the heart.

Absorption and transport of dietary fat: Many digested fats are too large to enter the blood capillaries and are

instead absorbed into lymphatic capillaries. Special lymphatic capillaries, called lacteals (L. lacteus, milk), receive all lipid and lipid-soluble vitamins absorbed by the intestine. Visceral lymphatics then convey the milky fluid, chyle (G. chylos, juice), to the thoracic duct and into the venous system.

Formation of a defense mechanism for the body: When foreign protein drains from an infected area, antibodies specific to

the protein are produced by immunological cells (lymphocytes) and dispatched to the infected area.

Peritoneal covering: The spleen is surrounded by peritoneum, which passes from it at the

hilum to the: Greater curvature of the stomach as the gastrosplenic ligament (carrying the

short gastric and left gastroepiploic vessels). Left kidney as the splenicorenal ligament (carrying the splenic vessels and

the tail of the pancreas).

Blood supply: Arteries

The large splenic artery is the largest branch of the celiac artery. It has a tortuous course as it runs along the upper border of the pancreas. The splenic artery then divides into about 6 branches, which enter the spleen at the hilum.

Veins The splenic vein leaves the hilum and runs behind the tail and the body of the

pancreas. Behind the neck of the pancreas, the splenic vein joins the superior mesenteric vein to form the portal vein.

Lymph drainage: The lymph vessels emerge from the hilum and pass through a few lymph

nodes along the course of the splenic artery and then drain into the celiac nodes.

Splenic Enlargement A pathologically enlarged spleen extends downward and

medially. The left colic flexure and the phrenicocolic ligament prevent

a direct downward enlargement of the organ. As the enlarged spleen projects below the left costal margin,

its notched anterior border can be recognized by palpation through the anterior abdominal wall.

Trauma to the Spleen Although anatomically the spleen gives the appearance of

being well protected, automobile accidents of the crushing or run-over type commonly produce laceration of the spleen.

Penetrating wounds of the lower left thorax can also damage the spleen.

Clinical Notes

Superficial lymph vessels: The superficial lymph vessels draining the

superficial tissues of the upper arm pass upward to the axilla.

Those from the lateral side of the arm follow the cephalic vein to the infraclavicular group of nodes; those from the medial side follow the basilic vein to the lateral group of axillary nodes.

The deep lymphatic vessels: draining the muscles and deep structures of the arm drain into the lateral group of axillary nodes.

Lymphatic drainage of the upper limb

SiteAfferentEfferent

Anterior (pectoral) group

At the lower border of pect. minor (along lat. thorathic artery)

Lat. part of breastFront of trunk (above umbilicus)

Central groupApical group

Lateral (Brachial)group

Along the lateral wall of axilla (along axillary vein)

Most of lymphatics of UL

Central groupApical groupFew lymph vessels pass to deep cervical LN

Posterior(subscapular)group

Along lower border of subscapularis (along subscapular artery)

Back of trunk (above iliac crest)Tail of breastFrom the previous 3 groups

Central groupApical group

Central group

At the base of axilla in fat of axilla (closely related to intercosto-brachial N

From the previous 3 groups

Apical group

Apical groupNear the apex of axilla (behind clavi-pectoral fascia)

From previous groupsUpper part of breast

Lymph vessels of this group unite to form subclavian lymph trunk which opens into:

1. on left side: in thoracic duct

2. on right side: in right lymph duct

Axillary Lymph Nodes

Inguinal lymph nodes: are divided into superficial & deep groups. Superficial inguinal LNS

They lie in the superficial fascia below the inguinal ligament and can be divided into a horizontal and a vertical group.

The horizontal group lies just below and parallel to the inguinal ligament.

The medial members of the group receive superficial lymph vessels from the anterior abdominal wall below the level of the umbilicus, perineum, urethra, external genitalia of both sexes (but not the testes) and lower 1l2 of anal canal.

The lateral members of the group receive superficial lymph vessels from the back below the level of the iliac crests.

The vertical group lies along the terminal part of the great saphenous vein and receives most of the superficial lymph vessels of the lower limb.

The efferent lymph vessels from the superficial inguinal nodes pass through the saphenous opening in the deep fascia and join the deep inguinal nodes.

Lymphatic drainage of the lower limb

Lymphatic drainage of the thorax

Thoracic Wall:

The lymph vessels of the skin of the anterior thoracic wall drain

to the anterior axillary nodes.

The lymph vessels of the skin of the posterior thoracic wall drain

to the posterior axillary nodes.

The deep lymph vessels of the anterior parts of the intercostal spaces drain

to the internal thoracic nodes (along the internal thoracic vessels) to the thoracic duct on Lt.side and the bronchomediastinal trunk on Rt. side.

The deep lymph vessels of the posterior parts of the intercostal spaces drain

to the posterior intercostal nodes (lying near the heads of the ribs( to the thoracic duct.

Lymphatic drainage of the abdomen

Abdominal Wall:Superficial lymph vessels

The lymph vessels of the skin of anterior abdominal wall above the level of the umbilicus drain

to the anterior axillary nodes.

The lymph vessels of the skin of anterior abdominal wall below the level of the umbilicus drain

to the superficial inguinal nodes.

The lymph vessels of the skin of the back above the level of the iliac crests drain

to the posterior axillary nodes.

The lymph vessels of the skin of the back below the level of the iliac crests drain

to the superficial inguinal nodes.

Deep lymph vessels

The deep lymph vessels follow the arteries and drain

into the internal thoracic, external iliac, posterior mediastinal and para-aortic nodes.

Lymph nodes

The lymph nodes are closely related to the aorta and form a preaortic and a Rt. & Lt. lateral aortic (para-aortic) chain.

The preaortic lymph nodes lie around the origins of the celiac, superior mesenteric & inferior mesenteric arteries and are called as the celiac, superior mesenteric & inferior mesenteric lymph nodes, respectively. They drain the lymph from the gastro-intestinal tract, extending from the lower 1/3 of esophagus to halfway down the anal canal, and from the spleen, pancreas, gallbladder, and greater part of the liver. The efferent lymph vessels form the large intestinal trunk.The para-aortic lymph nodes drain lymph from the kidneys and suprarenals; from the testes in the male and from the ovaries, uterine tubes, and fundus of the uterus in the female; from the deep lymph vessels of the abdominal walls; and from the common iliac nodes. The efferent lymph vessels form the right and left lumbar trunks.

Lymph vessels

The thoracic duct starts in the abdomen as an elongated lymph sac, the cisterna chyli, which receives the intestinal trunk, the right and left lumbar trunks & some small lymph vessels that descend from the lower part of the thorax.

Abdominal cavity:

NameSiteThey receive lymph from

Occipital nodes

Over occipital bone on the back of skull.

Back of the scalp.

Retroauricular nodes

Behind ear over mastoid process.

Scalp above the ear, auricle & the ext. auditory meatus.

Parotid nodesOn or within the parotid gland.

Scalp above the parotid gland, eyelids, parotid gland & auricle.

Buccal nodesOver buccinator muscle.

Lateral side of scalp & face.

Submandibular nodes

Superficial to the submandibular gland just below the lower margin of jaw.

Front of scalp, nose, cheek, upper lip & lower lip (except the central part), frontal, maxillary & ethmoid sinuses, upper & lower teeth (except the lower incisors); anterior 2/3 of tongue (except the tip), floor of mouth & gums.

Submental nodes

In submental triangle just below the chin

Tip of tongue, floor of anterior part of mouth, incisor teeth, center part of the lower lip, and skin over the chin.

Regional nodes: are arranged as follows:

NameSiteThey receive lymph from

Retropharyngeal nodes

behind pharynx & infront of vertebral column.

Nasal pharynx, the auditory tube, and the vertebral column.

Laryngeal nodes

in front of the larynx Larynx.

Paratracheal nodes

alongside the trachea. Neighboring structures, including the thyroid gland.

Anterior cervical nodes

Along the course of ant. jugular veins.

Skin and superficial tissues of the front of the neck.

Superficial cervical nodes

Along course of ext. jugular vein superficial to sternomastoid.

Skin over the angle of the jaw, the skin over the lower part of the parotid gland, and the lobe of the ear.

Deep cervical nodes

Form a vertical chain along the course of IJV within the carotid sheath

All the groups of regional nodes.

The efferent lymph vessels from the deep cervical lymph nodes join to form the jugular trunk, which drains into the thoracic duct or Rt. lymphatic duct.

Spread of cancer: Cancer invades the body by growing into

adjacent tissue or by dissemination of tumor cells to sites distant from the original or primary tumor) metastasis).

Metastasis occurs by one of three ways: Direct seeding of the serous membranes of

body cavities. Lymphogenous spread via lymphatic

vessels. Hematogenous spread via blood vessels.

Lymphogenous spread is the most common route for the initial dissemination of carcinomas (epithelial tumors), the most common type of cancer.

Hematogenous spread is the most common route for the metastasis of the less common (but more malignant) sarcomas (C.T. cancers. Because veins are more abundant and have thinner walls that offer less resistance, metastasis occurs more often by venous than arterial routes. Since the blood-borne cells follow venous flow, the liver and lungs are the most common sites of secondary sarcomas.

Clinical Notes Disease of the Lymphatic System

Lymphangitis, Lymphadenitis, and Lymphedema:

Lymphangitis and lymphadenitis: are 2ry inflammation of lymphatic vessels and lymph nodes, respectively.

These conditions may occur when the lymphatic system is involved in chemical or bacterial transport after severe injury or infection.

The lymphatic vessels, not normally evident, may become apparent as red streaks in the skin, and the nodes become painfully enlarged.

Lymphedema or edema: is a localized accumulation of interstitial fluid, occurs when lymph does not drain from an area of the body, e.g. if cancerous lymph nodes are surgically removed from the axilla, lymphedema of the limb may occur.