Lymphatic System: Spleen, Thymus Gland and Lymph Nodes PDF

LYMPHATIC SYSTEM SPLEEN, THYMUS GLAND AND LYMPH NODES Prof Dr Mohamed El-Badry Mohamed Professor and Head of Human Anatomy and Embryology Department, Head of Academic Departments Faculty of Medicine, Merit University Professor of Human Anatomy and Embry...

LYMPHATIC SYSTEM SPLEEN, THYMUS GLAND AND LYMPH NODES Prof Dr Mohamed El-Badry Mohamed Professor and Head of Human Anatomy and Embryology Department, Head of Academic Departments Faculty of Medicine, Merit University Professor of Human Anatomy and Embryology Department, Faculty of Medicine, Assiut University Learning objectives: After the lecture, students should be able to: - Describe anatomy of lymphatic system; definitions, end of lymphatic system, and sites of body have not lymph vessels. -Describe anatomy of the spleen - Describe anatomy of the thymus gland - Describe anatomy of the lymph nodes - What is the applied anatomy of the lymph nodes? LYMPHATIC SYSTEM Essentially a drainage system. There is no circulation. Essential for immunologic defences of the body against bacteria and viruses, absorption and transport of dietary fat. Lymphatic (Lymphoid) Tissues: - Type of connective tissue that contains large amounts of lymphocytes Sites that produce lymphocytes: 1. Thymus 2. Lymph nodes 3. Spleen 4. Lymphatic nodules aggregated in walls of digestive tract 6. Myeloid tissue in red bone marrow Lymphatic Vessels: Tubes that assist cardiovascular system in removal of tissue fluid from tissue spaces of the body then return the fluid to the blood. They are present in all tissues and organs of the body EXCEPT: 1. Central nervous system 2. Eyeball 3. Internal ear 4. Epidermis of the skin 5. Cartilage 6. Bone Lymph: - Tissue fluid once it enters a lymphatic vessel. Lymph Capillaries: Network of fine vessels that drain lymph from the tissues They are in turn drained by small lymph vessels, which unite to form large lymph vessels. The lymph vessels have a beaded appearance because of the presence of numerous valves along their course. Lymph Nodes: Small masses of lymphatic tissue located along course of lymphatic vessels through it lymph is filtered on its way to venous system. Afferent Lymph Vessels: - Lymph vessels carry lymph to lymph node Efferent Lymph Vessels: Lymph vessels that transport lymph away from a lymph node Right Lymphatic Trunk: - Ends into junction of right venous angle Drains lymph from body’s right upper quadrant. Thoracic Duct: - Drains lymph from remainder of the body. Ends into left venous angle (angle between left internal jugular vein and left subclavian vein).  THORACIC DUCT  About 45 Cm long  Has many valves and beaded appearance  Main lymphatic duct in the body Drains lymph vessels from all the body except: 1) Right side of head and neck 2) Right upper limb 3) Right side of chest 4) Upper surface of right lobe of the liver Beginning:  In the abdomen  Behind right crus of diaphragm  As dilated sac; cisterna chyli  At level of L1, 2 Course and relations of thoracic duct: Ascends through aortic opening of diaphragm, on right side of descending thoracic aorta Crosses median plane behind oesophagus to reach its left border At lower border of body of 4th thoracic vertebra (sternal angle) Runs upward along left edge of oesophagus to enter root of neck Bends laterally behind carotid sheath and in front vertebral vessels At level of 7th cervical vertebra Turns downward in front of phrenic nerve Crosses 1st part of left subclavian artery End of thoracic duct: In the neck Beginning of left brachiocephalic vein Thoracic duct at root of the neck receives: 1. Left jugular lymph trunk 2. Left subclavian lymph trunk 3. Left bronchomediastinal lymph trunk Thoracic duct conveys to blood lymph from: 1. Lower limbs 2. Pelvic cavity 3. Abdominal cavity 4. Left side of thorax 5. Left side of head and neck 6. Left upper limb  RIGHT LYMPHATIC TRUNK About ½ inch (1.25 Cm) long Formed by union of: 1. Right jugular lymph trunk 2. Right subclavian lymph trunk 3. Right bronchomediastinal lymph trunk Drains: 1. Right side of head and neck 2. Right upper limb 3. Right side of thorax End: Beginning of right brachiocephalic vein  SPLEEN Prof Dr Mohamed El-Badry Mohamed  SPLEEN 1, 3, 5, 7, 9, 11  1 inch thick, 3 inches wide, 5 inches long, 7 ounces weight and 9-11 ribs relation  Reddish in colour  The largest single mass of lymphoid tissue in the body  Oval in shape  Lies just below left half of diaphragm close to 9th, 10th and 11th ribs  The long axis: Lies along shaft of 10th rib  Its lower pole extends forward only as far as mid-axillary line  Can not be palpated on clinical examination  Has notched anterior border  Surrounded by peritoneum: Passes from its hilum as gastrosplenic ligament to greater curvature of the stomach (carrying short gastric and left gastroepiploic vessels)  Peritoneum also passes to left kidney as lienorenal ligament (carrying splenic vessels and tail of pancreas) RELATIONS OF SPLEEN: Anteriorly (visceral surface): 1.Stomach 2.Tail of pancreas 3.Left colic flexure 4.Left kidney Posteriorly (diaphragmatic surface) of spleen: 1.Diaphragm 2.Left pleura (left costodiaphragmatic recess) 3.Left lung 4.Left 9th, 10th and 11th ribs BLOOD SUPPLY OF SPLEEN: ARTERIES: Celiac trunk  Splenic artery (6): Enter spleen at the hilum VEINS: Portal vein  Splenic vein: leaves the hilum and runs behind tail and body of pancreas to join superior mesenteric vein behind neck of pancreas to form portal vein LYMPH DRAINAGE:  Lymph vessels emerge from hilum and pass through lymph nodes along course of splenic artery and drain into celiac nodes NERVE SUPPLY:  Accompany splenic artery and derived from celiac plexus THYMUS GLAND  THYMUS GLAND Primary lymphoid organ Flattened, bilobed structure, no main hilum Lying between sternum and pericardium in anterior mediastinum Thymus gland in newborn infant: Has largest size relative to size of the body Extend up into superior mediastinum front great vessels into root of the neck Continues to grow until puberty, but later undergoes involution Pink, lobulated appearance Site for development of T (thymic) lymphocytes (immunity) Arterial supply of thymus gland: 1) Inferior thyroid artery 2) Internal thoracic artery 3) Superior thyroid artery (sometimes) Venous drainage of thymus gland: 1) Left brachiocephalic vein (common) 2) Internal thoracic veins 3) Inferior thyroid veins Lymphatic drainage of thymus gland: No afferent lymphatics Efferent vessels end into following nodes: 1) Brachiocephalic 2) Tracheobronchial 3) Parasternal Nerve supply of thymus gland: 1) Sympathetic chain via cervico-thoracic (stellate) ganglion and vagus nerve (ANS) 2) Branches from phrenic and descending cervical nerves to its capsule (sensory) LYMPH NODES  Lymph nodes Encapsulated centres of antigen presentation and lymphocyte activation, differentiation and proliferation. Generate mature, antigen-primed, B and T cells, and filter particles, including microbes, from the lymph by the action of numerous phagocytic macrophages. Normal young adult body contains up to 450 lymph nodes, of which 60– 70 are found in the head and neck, 100 in the thorax and as many as 250 in the abdomen and pelvis. Lymph nodes are particularly numerous in the neck, mediastinum, posterior abdominal wall, abdominal mesenteries, pelvis and proximal regions of the limbs (axillary and inguinal lymph nodes). The greatest number lie close to the viscera, especially in mesenteries.  Lymph nodes (Cont.) Small, oval or kidney-shaped bodies, 0.1–2.5 cm long, lying along course of the lymphatic vessels. Each usually has a hilum, through which blood vessels enter and leave and efferent lymphatic vessel leaves. Several afferent lymphatic vessels enter the capsule around periphery. Lymph nodes have a highly cellular cortex and a medulla which contains a network of minute lymphatic channels (sinuses) through which lymph from the afferent lymphatics is filtered, to be collected at the hilum by the efferent lymphatic. The cortex is absent at the hilum, where medulla reaches the surface.  Lymphatic and vascular supply The lymph vessels that carry lymph to a lymph node through the cortex are referred to as afferent vessels; those that transport it away from a node through the hilum are efferent vessels..  Arteries and veins Pass through the hilum, giving off straight branches which traverse the medulla, and sending out minor branches. In the cortex, arteries form dense arcades of arterioles and capillaries in numerous anastomosing loops, eventually returning to highly branched venules and veins. Veins leave a node through its principal trabeculae and capsule, and drain them and the surrounding connective tissue. Lymph nodes (Appied): May swell as the result of metastases, or primary tumor For this reason, lymphatic drainage of all major organs of the body, including the skin, should be known. THANK YOU