the lymphatic system consists of The lymph conducting channels Lymphoid tissues Lymphoid organs

The lymphatic system is part of the immune system and acts as a secondary (accessory) circulatory system.

Functions of the lymphatic system: remove excess fluids from body tissues, absorb fatty acid and transport fat to circulatory system, and produce immune cells (lymphocytes, monocytes, and plasma cells).

Blood fluid escapes through the thin-walled capillaries into spaces between body tissue cells. Lymph vessels, which have very thin walls, pick up these fluids called lymph.

Composition Lymphatic vessel Lymphatic capillary Lymphatic vessels: two sets, superficial and deep Lymphatic trunks: nine Lymphatic ducts: thoracic duct, right lymphatic duct Lymphatic organ Lymphatic nodes Tonsil, spleen, thymus Lymphatic tissue Include diffused lymphoid tissues and lymph nodules. They are mainly situated in the wall of the respiratory-alimentary tracts and consist of aggregated of lymphocytes and associates cells.

Tissue fluid and its formation composition same as blood but without read blood cells (RBCs), platelets & proteins because they are too large to leak out of the capillaries - forms a link between blood and cells, providing a medium for exchange of materials between blood & cells

At the arterial end of a capillary, liquid is forced out as tissue fluid which is similar to plasma in composition except its has no plasma proteins, platelets & RBCs.  At the venous end, some fluid returns to blood while some enters lymph vessels which eventually join to a vein near the heart and thus returns to blood finally.

Lymph some tissue fluid returns to capillaries by osmosis while some (about 10%) goes into lymph capillaries; this fluid is now called lymph Path: Blood  lymph capillaries  lymph vessels  lymph ducts  Blood - Lymph re-enters blood

Lymphatic capillary Begin blindly The wall is composed of a single layer of overlapping endothelial cells They are numerous and form complex networks The brain, spinal cord, bone marrow, parenchyma of spleen and eyeball lack lymphatic capillaries

Lymph is driven by contraction of surrounding muscles, aided by valves which enable one-way flow to the neck.

Movement of lymph through the lymphatic system: 1. Hydrostatic pressure 2. Muscle contraction 3. Inspiratory movement 4.Valves to ensure one-way traffic towards the heart

The Lymphatic System Heart Vein Lymphatic duct Artery Lymphatic trunk Capillaries Lymphatic node Cell Tissue fluid Lymphatic capillary Lymphatic vessel

lymphatic vessels lymphatic capillary lymphatic vessel lymphatic trunks lumbar trunks(2) brochomediastinal trunks(2) subclavian trunks(2) jugular trunks(2) intestinal trunk lymphatic ducts thoracic duct right lymphatic duct

Lymphatic vessel Features of structure Three layered wall similar to, but thinner than vein, More numerous valves than in vein Interposed by lymph node at interval along the course Arranged in superficial and deep sets

Lymphatic trunks right and left jugular trunks right and left subclavian trunks right and left bronchomediastinal trunks right and left lumbar trunks intestinal trunk

Lymphatic ducts Right lymphatic duct Formed by union of right jugular, subclavian, and bronchomediastinal trunks Ends by entering the right venous angle Receives lymph from right half of head, neck, thorax and right upper limb

Thoracic duct Begins in front of L1 as a dilated sac, the cisterna chyli , which formed by joining of left and right lumbar trunks and intestinal trunk Enter thoracic cavity by passing through the aortic hiatus of the diaphragm and ascends along on the front of the vertebral column, between thoracic aorta and azygos vein

Thoracic duct Travels upward, veering to the left at the level of T5 At the roof of the neck, it turns laterally and arches forwards and descends to enter the left venous angle Just before termination, it receives the left jugular, subclavian and bronchomediastinal trunks

Thoracic duct Drains lymph from lower limbs, pelvic cavity, abdominal cavity, left side of thorax, and left side of the head, neck and left upper limb

Lymphatic vessel Have valves that give them a beaded appearance Two sets: superficial (lie in the superficial fascia ) and deep (run with blood vessels and nerves) Passes through at least one lymph node and often several

lymphatic ducts thoracic duct from cisterna chyli (L1) to left venous angles left jugular trunk left subclavian trunk left bronchomediastinal trunk right and left lumbar trunk intestinal trunk right lymphatic duct right brochomediastinal trunk right subclavian trunk right jugular trunk

The lymph vessels join to form larger ducts that pass through lymph nodes (or glands). Each lymph node has a fibrous outer covering (capsule), a cortex, and a medulla.

(Small oval or bean-shaped bodes lymph node (Small oval or bean-shaped bodes Afferent vessels enter the node on its convex surface, and efferent vessels leave the node at its concave surface－the hilum Arranged in groups, along the blood vessels Regional nodes is the lymph node where the lymph of the organ or part of the body drainage to firstly

Photo from U. S. Federal Government courtesy of Wikipedia.

Lymph nodes filter foreign substances, such as bacteria and cancer cells, from the lymph before it is re-entered into the blood system through the larger veins. Lymph nodes, which are scattered among the lymph vessels, act as the body’s first defense against infection.

Lymph nodes produce the following cells: Lymphocytes – a type of white blood cell, Monocytes – a leukocyte that protects against blood-borne pathogens, and Plasma cells – produce antibodies.

Each lymph node has its own blood supply and venous drainage. The lymph nodes usually have names that are related to their location in the body.

When a specific location gets infected, the lymph nodes in that area will enlarge to fight the infection. If the lymph node closest to an infected area is unable to eliminate the infection, other lymph nodes in the system will attempt to fight the infection.

This is particularly critical in the case of cancer, which can be spread from its point of origin to all parts of the body through the lymphatic system.

Lymph drainage of the body

The lymphatic drainage of head Lymph nodes of head Located at junction of head and neck Consist of Occipital lymph nodes Mastoid lymph nodes Parotid lymph nodes ★ Submandibular lymph nodes lies near the submandibular gland, receive lymphatic vessels from the face, nose and mouth submental lymph nodes Drain into deep cervical lymph nodes

Lymph nodes of the neck Anterior cervical ln. Superficial anterior cervical lymph nodes Deep anterior cervical lymph nodes Lateral cervical ln. ★ Superficial lateral cervical ln. －lie along the external jugular vein ★ Deep lateral cervical ln. －extend along the internal jugular vein

Lymph nodes of the neck ★ Deep lateral cervical ln. Extend along the internal jugular vein from the base of skull to the root of neck Divided into superior deep lateral cervical ln. and inferior deep lateral cervical ln. Receive lymphatic vessels from head, neck, tongue, larynx, cervical parts of esophagus and trachea, thyroid gland, upper parts of the thoracic wall and breast Efferent vessels form the jugular trunk Left jugular trunk joins the thoracic duct Right jugular trunk joins the right lymphatic duct

Lymph nodes of the neck Superior deep lateral cervical ln. Jugulodigastric ln. Lies at the junction of posterior belly of digastric and internal jugular vein Drain the nasopharynx, palatine tonsil and root of tongue Inferior deep lateral cervical ln. Juguloomohyoid ln. Lies at the junction of the intermediate tendon of omohyoid and internal jugular vein Drain the apex of tongue

Lymph nodes of the neck Inferior deep lateral cervical ln. Supraclavicular lymph nodes Lie along transverse cervical a. & v. palpable in the supraclavicular fossa. The most notable supraclavicular lymph node is Virchow's node. which can contain metastasis of visceral (abdominal) tumor. Retropharyngeal ln. Lying vertically behind the pharynx drain nasopharyngeal lymph

Lymph nodes of upper limb Cubital lymph node lies above medial epicondyle of humerus Receive lymph vessels from forearm Axillary lymph node arranged in five groups

Axillary lymph nodes Axillary lymph nodes vary in size from a pin-head to a large bean. They are arranged in five groups.

Axillary lymph nodes Pectoral lymph nodes Lying along the lower border of pectoralis minor behind the pectoralis major Receive lymph vessels from the lateral quadrants of the breast and superficial vessels from the anterolateral abdominal wall above the level of the umbilicus

Axillary lymph nodes Lateral lymph nodes Along medial side distal part of axillary vein Receives lymph from upper limb

Axillary lymph nodes Subscapular lymph node Lying along subscapular vessels, in front of the subscapularis Receive superficial lymph vessels from the back, down as far as the level of the iliac crests Efferents of above three groups pass to central lymph node

Axillary lymph nodes Central lymph node Lying in the center of the axilla in the axillary fat Receive lymph from the above three nodes Efferents pass to apical lymph node

Axillary lymph nodes Apical lymph node infraclavicular lymph nodes Lying at the apex of the axilla at the lateral border of the fist rib Receive lymph of the efferent lymph vessels from all the other axillary nodes The efferents of the apical nodes form the subclavian trunk

Axillary lymph nodes Efferents form subclavian trunk, the right subclavian trunk joins the right lymphatic duct; left usually drains directly into thoracic duct Apical ln. Subclavian trunk Central ln. Pectoral ln. Lateral ln. Subscapular ln.

Lymphatic drainage of thorax The lymphatic drainage of thoracic wall To axillary lymph nodes To parasternal lymph nodes (along internal thoracic vessels) To intercostals lymph nodes from deeper structures

The lymphatic and venous drainages of the breast are of great importance in the spread of carcinoma. About three quarters of the lymphatic drainage is to the axillary nodes: (1) Lymphatics pass around the edge of the pectoralis major and reach the pectoral group of axillary nodes; (2) routes through or between the pectoral muscles may lead directly to the apical nodes of the axilla; (3) lymphatics follow the blood vessels through the pectoralis major and enter the parasternal (internal thoracic) nodes; (4) connections may lead across the median plane and hence to the contralateral breast; (5) lymphatics may reach the sheath of the rectus abdominis and the subperitoneal and subhepatic plexuses. It should be noted that free communication exists between nodes below and above the clavicle and between the axillary and cervical nodes.

lymph nodes of the thorax Pulmonary ln. lie in the angles of bifurcation of branching lobar bronchi Bronchopulmonary hilar ln. －lie in the hilums of the lung Tracheobronchial ln. －situated above or below the bifurcation of trachea Paratracheal ln. －along each side of the trachea

lymph nodes of the thorax Anterior mediastinal lymph node Lies anterior to the large blood vessels of thoracic cavity and pericardium The efferents unite with those of paratracheal lymph nodes and parasternal lymph nodes to form the right and left bronchomediastinal trunks The left bronchomediastinal trunk terminates in thoracic duct, and right in the right lymphtic duct Posterior mediastinal lymph nodes lie along the esophagus and thoracic aorta

Lymph nodes of lower limb Popliteal ln. Embedded in the fatty connective tissue of popliteal fossa Receive superficial lymphatic vessels from posterolateral part of calf, and from deep lymphatic vessels accompanying anterior and posterior tibia a. Efferents pass to the deep inguinal ln.

Lymph nodes of lower limb Superficial inguinal lymph nodes Superior group: Lies just distal to the inguinal ligament Receive lymph vessels from anterior abdominal wall below umbilicus, gluteal region, perineal region, external genital organs Inferior group: Lies vertical along the terminal great saphenous v. Receives all superficial lymph vessels of lower limb, except for those from the posterolateral part of calf Efferent vessels drain into the deep inguinal ln. or external iliac ln.

Lymph nodes of lower limb Deep inguinal lymph nodes Lie medial to the femoral v. Receive deep lymph vessels of lower limb, perineal region, and efferent vessels from the superficial inguinal ln. Drain into the external iliac ln.

Lymph nodes of pelvis Internal iliac lymph node Surround internal iliac vessels Receive afferents from pelvic viscera, perineum, buttock and back of thigh External iliac lymph nodes Lie along external iliac artery Receive afferents from lower limb and some parts of pelvic viscera Sacral lymph node locate along middle sacral a. and lateral sacral a. Receive lymph from posterior pelvic wall ,rectum,prostate or uterus Common iliac lymph node Lie along common iliac artery Receive afferents from all the above nodes Efferent pass to lumbar lymph node

Lymph nodes of abdomen Lymphatic drainage of abdominal wall To axillary lymph node from region above umbilicus To superficial inguinal lymph node from region below umbilicus To lumbar lymph node from post wall of abdomen

Lymph nodes of abdomen Lymphatic drainage of abdominal viscera Lumbar lymph nodes Lie on posterior abdominal wall, along the abdominal aorta and inferior vena cava Receive lymph from kidneys, suprarenal glands, testes, ovaries, fundus of uterus, uterine tubes, and common iliac nodes Right and left lumbar trunks formed by efferent vessel Paired viscera－drain to the lumbar lymph nodes

Lymph nodes of abdomen Right and left gastric ln. lie along the same vessels and finally to the celiac ln. Right and left gastroomental ln. lie along the same vessels, the former drain into subpyloric ln., the latter drain into splenic ln. Suprapyloric and subpyloric ln. receive lymphatics from pyloric part and finally to the celiac ln. Splenic ln. receive lymphatics from fundus and left third of stomach, and finally to the celiac ln. Celiac lymph nodes －situated around the celiac trunk

Lymph nodes of abdomen Superior mesenteric lymph node －situated around superior mesenteric a. Inferior mesenteric lymph node －situated around inferior mesenteric a. Intestinal trunk －formed by efferent vessel of celiac, superior and inferior lymph nodes

Thymus Featrues Consists of two elongated lobes Is large organ in the fetus Occupies the thoracic cavity behind the sternum Secrete lymphopoietin

Thymus The thymus is partly in the neck and partly in the thorax. It comprises one to three lobes, each of which consists of numerous lobules containing lymphocytes, which are important in the development and maintenance of the immune system. The cervical part of the thymus lies on the anterior and lateral sides of the trachea, whereas the thoracic part lies posterior to the superior portion of the sternum. The organ has a profuse blood supply and lymphatic drainage. The thymus reaches its greatest size at puberty and then begins to regress. Much of its substance is replaced by fat and fibrous tissue, but thymic tissue never disappears completely. Function:to develop lymph cell

Spleen Shape Location: The largest single mass of lymphoid tissue in the body Reddish in color Location: lies in the left hypochondriac region (between stomach and diaphragm) deep to the 9th to 11th rib its long axis corresponds roughly to the 10th rib Its lower pole extends forward only as far as the midline and cannot be palpated on clinical examination

Spleen Two surfaces Two extremities Two border Diaphragmatic: smooth, convex Visceral: concave, hilum of spleen Two extremities Anterior－wider Posterior－rounder Two border Superior－has 2-3 splenic notch, which serve as a landmark on palpation when it is enlarge; normally it is not palpable Inferior－rounder

Spleen Function Erythrocyte storage Phagocytosis Cytopoiesis Immune responses