Lymphatic System Anatomy ANAT 211, 212, 213 2023-2024 PDF

Lymphatic System Anatomy Course ANAT 211, 212 and 213 Term 2, 2023-24 Basic Sciences Department, COSHP, KSAU-HS, KSA The Lymphatic System At the end of this session the students should be able to: Describe lymph and its formation Identify the components of lymphatic system Discuss lymph circulation...

Lymphatic System Anatomy Course ANAT 211, 212 and 213 Term 2, 2023-24 Basic Sciences Department, COSHP, KSAU-HS, KSA The Lymphatic System At the end of this session the students should be able to: Describe lymph and its formation Identify the components of lymphatic system Discuss lymph circulation and its relation to cardiovascular system Discuss the significance of lymphatic obstruction Discuss lymphatic vessels and regional groups of lymph nodes Describe the structure of Thymus, Spleen, Lymph Nodes, Tonsils, Lymphatic nodules. Discuss the lymphatic drainage of different regions of body Origin of Lymph The arterial blood slows down as it moves through the capillaries. This allows plasma to leave the capillaries and flow into the tissues where it becomes tissue fluid. This fluid is called interstitial fluid. Exchange of nutrients and waste occurs between the cells and the fluid. After this task is complete, 90% of this fluid carrying waste products, returns to the circulatory system as venous blood. The remaining 10% of the fluid left behind is called “Lymph” when it enters the lymph capillaries. Lymphatic Circuit Components of Lymphatic System The lymphatic system comprises of: o Lymph o Lymph capillaries o Lymphatic vessels o Lymphatic cells o Lymphatic duct o Lymphatic nodules o Lymph nodes and other lymphoid organs Components of Lymphatic System Lymph The extracellular fluid/ tissue fluid once it has entered the lymph capillaries is called as “Lymph” It is similar in composition as plasma Lymph formation depends on tissue fluid formation Lymphatic system and its Relationship with Cardiovascular System Every day, around 20 liters of plasma fluid, carrying dissolved substances and some plasma protein, escape from the arterial end of the capillaries and into the tissues. Most of this fluid is returned directly to the bloodstream via the capillary at its venous end, but 3-4 liters of fluid are drained away by the lymphatic vessels. Without this system, the tissues would rapidly become waterlogged, and the cardiovascular system would begin to fail as the blood volume falls. Lymphatic system and its Relationship with Cardiovascular System The lymphatic vessels which are blind-ended unidirectional absorptive vessels that transport interstitial fluid, immune cells, and macromolecules to the lymph nodes and from these back to the blood circulation. In the process helps to maintain pressure and volume of the extracellular fluid. Functions of the Lymphatic System o Removal of large molecular weight substances/ proteins which cannot be absorbed by the blood capillaries o Immunity: Lymphatic organs contain lymphocytes that destroy invading organisms Lymph nodes and other lymphatic organs filter the lymph to remove microorganisms and other foreign particles o Absorption: The absorption of fats and fat-soluble vitamins from the digestive system Why is this information of lymph drainage so important ? Damage to the lymphatics disturbs the flow of lymph If the lymphatic tissue or lymph nodes have been removed, obstructed or destroyed by disease, lymph cannot drain normally from the affected areas Consequences of Lymphatic Obstruction Any obstruction to drainage of lymph due to disease or removal and destruction of lymphatics during surgery, results in accumulation of lymph leading to swelling called Lymphedema Lymphatic Circulation 1. Interstitial fluid 2. Lymph capillaries 3. Afferent lymphatic vessels 4. Lymph nodes 5. Efferent lymphatic vessels 6. Lymphatic trunks 7. Lymphatic duct Venous system Lymphatic Capillaries Features: The lymphatic capillaries are blind ended capillaries, located next to blood capillaries in tissue spaces. These are lined by a single layer of overlapping endothelial cells which act as one-way valves allowing interstitial fluid to flow in but not out. More permeable than blood capillary. Absent from epithelia, cartilage, brain, spinal cord and bone marrow. Lymphatic Vessels Features: Three layered wall (tunica intima, media and externa) similar to, but thinner than vein More numerous valves than in vein Presence of lymph nodes at interval along the course Arranged in superficial and deep sets. The superficial lymphatics run with veins and deep with arteries Larger lymphatic vessels pass through lymph nodes and merge to form lymphatic trunks Right and left Lymphatic Trunks Named for the regions they drain  Right and left jugular trunks drain the Head & Neck regions  Right and left subclavian trunks drains the upper limbs  Right and left bronchomediastinal trunks drains the Thorax  Right and left lumbar trunks abdomen, pelvis and lower limbs  Intestinal trunk drains the intestine Lymphatic ducts Right lymphatic duct  Formed by union of right jugular, right subclavian, and right bronchomediastinal trunks  Ends by entering in venous system at the junction between right subclavian and internal jugular veins  Receives lymph from right half of head, neck, thorax and right upper limb cnx.org Thoracic Duct 1. Begins in front of L2 vertebra as a dilated sac, the cisterna chyli, which is formed by the union of left and right lumbar trunks and intestinal trunk 2. At the root of the neck, it enters the left brachiocephalic vein 3. Just before its termination, it receives the left jugular, left subclavian and left bronchomediastinal trunks 4. It drains all parts of the body except those drained by the Right lymphatic duct Lymphatic Tissue The lymphatic tissue is composed of two main components: (1) Cells: lymphocytes {T-cells and B-cells}, macrophages, and reticular cells. (2) Supporting frame work of reticular connective tissue. 1. Mucosa-Associated Lymphatic Tissues are diffuse scattering or collection of lymphocytes in the mucous membranes of the respiratory digestive, urinary, and reproductive tracts 2. Lacteals are special lymphatic capillaries in the villi of small intestine. These are sites of lipid absorption, bringing of lipids from digestive system back to blood. Aggregates of Lymphatic Cells Lymphatic nodules are isolated clusters of lymphocytes and macrophages with some extracellular matrix. They are: Not surrounded by a capsule Much smaller than lymph nodes Not located along a lymphatic vessel so do not act as lymph filters Nodules are a constant feature of the lymph nodes, tonsils, and appendix Payer's patches are dense clusters of lymphocytes in the ileum Lymphatic Organs The lymphoid organs have well-defined anatomical sites. These are composed of lymphatic tissue surrounded by connective tissue capsule. Examples: lymph nodes, spleen, thymus gland Lymphatic organs can be classified as: Primary lymphatic organs also called central lymphoid organs. It is where immature lymphocytes develop and mature; they include thymus and bone marrow (red) Secondary lymphatic organs and tissues where antigen is exposed to mature lymphocytes, they include: lymph nodes, spleen, and lymph nodules Lymphatic Organs and Tissues Lymph Node Lymph nodes are most numerous lymphatic organs scattered throughout the body usually in clusters These are elongated bean shaped structures arranged into superficial and deep groups The lymph nodes cleanse the lymph and act as a site of T and B cell activation Major lymph nodes groups are: 1. Cervical located in neck area, filter lymph from head and neck 2. Axillary located in armpits filter lymph from upper limb and breast 3. Inguinal located in groin area filter lymph from lower extremities and external genital organs 4. Abdominal, Intestinal and Mesenteric located in abdomen/abdominal peritoneum filter lymph from abdominal cavity, viscera and pelvic region Cervical Axillary Abdominal Inguinal Spleen A largest lymphatic organ located in upper left hypochondriac region between fundus of stomach and diaphragm; between 9th-11th rib, in line of 10th rib Features: Surfaces & borders:  Diaphragmatic surface-posterior  Visceral surface - Splenic Hilum -anterior  Superior border- Splenic Notch  Inferior border  Anterior extremity  Posterior extremity Hilum: a depression on medial surface where nerves and Blood vessels enter and leave the spleen. Hilum Thymus A member of the endocrine, lymphatic, and immune systems The lymphoid organ that does not filters blood or lymph Bi-lobed organ located between sternum and aortic arch Covered by a fibrous capsule that gives off septa that divide the gland into several lobes lobes have cortex and medulla populated by T-lymphocytes, responsible for cell-mediated immune responses. Atrophies after puberty o Lymphoid tissue is in the form of diffuse aggregated lymphocytes o It has no lymph nodules and no afferent lymphatics, but efferent lymphatics are present o Secretes hormones: thymosin and thymopoietin which regulate maturation of T-lymphocytes