Vasc. Unit 2.2 Anatomy and Physiology PDF

THE LYMPHATIC SYSTEM: ANATOMY AND PHYSIOLOGY Unit 2 Unit Objectives: Tubular System ■ To gain knowledge of the anatomy and physiology of the following lymphatic system components – Lymph – The lymphatic organs – Pre lymphatic channels – Lymphatic capillaries – Lymphatic pre collectors – Lymphati...

THE LYMPHATIC SYSTEM: ANATOMY AND PHYSIOLOGY Unit 2 Unit Objectives: Tubular System ■ To gain knowledge of the anatomy and physiology of the following lymphatic system components – Lymph – The lymphatic organs – Pre lymphatic channels – Lymphatic capillaries – Lymphatic pre collectors – Lymphatic collectors/ lymphangion – Lymphatic nodes – Post nodal collectors – Lymphatic trunks – Lymphatic ducts The lymphatic system Lymph capillaries Lymph node Pulmonary blood capillaries Lymphatic vessel THE TUBULAR SYSTEM Valve Lymph node Lymphatic vessel Systemic blood capillaries Lymph capillaries Lymphatic vessels that carry the lymph from interstitial spaces to the venous system (at the base of the neck) Components of the Tubular System Lymphatic Collectors ■ Vessels of a larger calibre than the previous capillaries and pre collectors ■ Made up of three layers: – Tunic intima: endothelial cell, – Tunic media: smooth muscle, – Tunic externa: collagen fibres ■ Similar to veins but with more valves, thinner and anastomose more ■ Lymphatic nodes are intermittently present along their course Valves and Lymphangion ■ The portion of vessel between 2 consecutive valves is called the lymphangion Valves Lymphangion Similar to those in the vascular venous system; allow flow in one direction. The portion of lymphatic vessel between two consecutive valves. Made of endothelial cells that are continuous with the inside wall of the lymphatic collector vessels. The walls of these sections of vessels contain smooth muscle that are able to contract 10-12 times a minute, with a resting interval of 5-6 seconds. Bicuspid in the collector vessels. The frequency of contraction may be influenced by lymph load and external stretch e.g. MLD, hormones.. The Lymphangion Innervation: Autonomic or somatic nervous system? A co-ordinated contraction of smooth muscle takes place. The contraction is staggered along the collector vessel, giving each vessel a systolic and diastolic phase Lymphatic Collectors ■ Run in 3 networks – Superficial: drains from the skin and subcutaneous tissue – Deep: drains from muscles, joints, synovial sheaths – Visceral: drains from the internal organs of the abdomen Anastomosing Collector Vessels ■ Between the lymph collectors there are anastomosing collateral branches that allow lymph to flow through if there is an obstacle in the path of one of the collectors. Superficial → superficial Deep → deep Lymph Nodes ■ Collections of concentrated lymphatic tissue ■ Main functions – Filtration: Macrophages destroy microorganisms and other debris before the lymph reaches its terminal location; the blood stream – Immune system activation: Nodes are located at regional sites for lymphocytes to encounter antigens, to be activated to bring about the attack (direct and through antibodies) – Transport of fats (uptaken in lacteals) Lymph Nodes ■ Bean shaped and usually <25mm in length ■ Afferent vessels bring lymph in (on convex side) and it exits through efferent vessels (on concave side) ■ Compartmentalised by connective tissue called trabeculae ■ 2 main sites: cortex and medulla ■ Cortex contains T and B cells ■ Medulla acts as a collection space for lymph and the mainly T cells before entry into the lymphatic vessels ■ Movement stagnates in medulla afferent vessels>efferent vessels Lymph Nodes ■ The size, position and number of lymph nodes varies ■ 500-1000 (600 average) throughout body ■ Number determined at birth ■ Concentrated at: • Inguinal region • Pelvic cavity • Abdominal cavity (along small intestine) • Thoracic cavity • Axillary region • Supratrochlear region • Face and cervical region (the highest concentration ≈ 160 nodes) Post Nodal Collectors ■ These vessels are very similar to the previously discussed lymphatic collectors except: – They are of a wider diameter – Their valves are tricuspid rather than bicuspid They carry lymph through to further nodes (to ensure the lymph is thoroughly cleansed) and to the larger lymphatic trunk vessels From Collectors to Trunks… Superficial Deep Trunk Visceral Lymphatic Trunks ■ These are the largest vessels in the system which carry lymph from the postnodal collectors of large relatively defined areas of the body ■ The trunks appear in the following branches Paired – Lumbar and so – Bronchomediastinal appear on left and – Subclavian right side – Jugular of body – Intestinal Singular trunk Lymphatic Trunks ■ The route of the trunks is not symmetrical Name of trunk Area of body it drains Lumbar Lower limbs Intestinal Abdominal organs Bronchomediastinal Breast tissue, thoracic organs, intercostal tissues Subclavian Upper limbs Jugular Head and neck The trunks drain into one of two lymphatic ducts Lymphatic Ducts ■ There are two ducts within the lymphatic system ■ They contain many valves and carry the lymph to the terminal location The right lymphatic duct The thoracic duct Lymphatic Ducts- The Right Lymphatic Duct ■ Deposits lymph into the right terminus ■ Located anterior to the right anterior scalene ■ Formed from the junction of the right jugular, right subclavian and right bronchomediastinal lymphatic trunks ■ Therefore it terminates the lymph arising from… Lymphatic Ducts- The Thoracic Duct ■ Deposits lymph in the left terminus ■ Arises anterior to L2 as an enlarged sac called the cisterna chyli or Pequet’s cistern ■ Cistern chyli collects lymph from both lumbar trunks and intestinal trunk ■ Continues superiorly as the thoracic duct ■ Collecting from: left bronchomediastinal, left subclavian and left jugular trunk ■ It therefore terminates the lymph arising from… Right jugular Left jugular Right bronchomediastinal Left bronchomediastinal Right subclavian Left subclavian Right lumbar Intestinal Left lumbar Lymph Terminus ■ The lymph collected in each duct reaches it’s terminal location ■ The right lymphatic duct deposits lymph into the junction where the right internal jugular vein anastomoses the right subclavian vein ■ The thoracic duct deposits lymph into the left equivalent ■ Valves prevent venous reflux The lymph has therefore reached its terminal location- the venous system The Movement of Lymph ■ How does lymph flow without the presence of a pumping organ? ■ 2 intrinsic factors, 3 extrinsic factors ■ The lymphatic pump (intrinsic factors)– The rhythmic contraction of the smooth muscle within collector vessels (lymphangion) and trunks – The presence of one-way valves that prevent backflow – How many times does the smooth muscle contract per minute? What is the resting interval time? The Movement of Lymph ■ Extrinsic compression (extrinsic factors)– The contraction of surrounding skeletal muscles – The thoracic/respiratory pump – The flow of venous blood in subclavian veins drawing lymph in End of unit… Quiz-tions on lymphatic anatomy and physiology Kahoot.it Lymphatic System Unit Summary Tubular System Lymphatic Organs Bone Marrow Pre Lymphatic Channels Capillaries Pre Collectors The Thymus The Tonsils The Spleen • Anatomy, physiology and function of the labelled components of the lymphatic system • Mechanism of movement within the vessels Collectors Lymph Nodes Lymphoid Follicles Lymph Nodes Ducts Trunks Post Nodal Collectors