Lymphatic System of Human Body by Dr. Rabia Inam Gandapore.pptx

General Anatomy

1. Lymphatic System Dr. Rabia Inam Gandapore Assistant Professor Head of Department (Dentistry-BKCD) B.D.S (SBDC) , M.Phil. Anatomy (KMU) , Dip. Implant (Sharjah, Bangkok, ACHERS) , CHPE (KMU) , CHR (KMU) , Dip. Arts (Florence, Italy)

2. Lymphatic System Lymphatic system = drainage system of coarse type Its Accessory to venous system = drainage system of fine type . Tissue fluid (10-20%) = absorbed by lymphatic (begin blindly in tissue spaces). Larger particles (proteins etc.)= removed from tissue fluid by Lymphatics

3. Tissue fluid formed at the arterial end of capillaries is absorbed back into the blood by venous ends of the capillaries and post capillary venules . Starts from portal radicle around hepatic lobule and joins to drain into thoracic duct which ends in the large vein near heart

4. L ymphatic system ( lympho -reticular organs ) involved in Phagocytosis Increase immune responses C ontributing to cell populations of blood & lymph . Tissue fluid is called lymph , Lymph vessels = Lacteals . F ilters via lymph nodes & drains into venous blood . Lymph is clear & colourless L ymph from small intestine is milky-white called chyle due to absorption of fat .

5. Components of Lymphatic System L ymphatic system comprises: Lymph capillaries & vessels C entral lymphoid tissues P eripheral lymphoid organs C irculating lymphocytes Epithelio -lymphoid system Mononuclear phagocytes system

6. 1. Lymph Vessels and Capillaries B egin blindly in tissue spaces and form intricate networks. C alibre is greater and less regular than blood capillaries, E ndothelial wall is permeable to substances of greater molecular size. Lymph capillaries are absent from the cellular structures i .e. Brain spinal cord splenic pulp, bone marrow etc Lymph capillaries have been compared to blood capillaries

7. Comparison of lymph and blood capillaries No. Lymph Capillaries Blood Capillaries 1. Colourless, difficult to observe. Reddish, easy to observe 2. Blind (closed at the tip). Joined to arterioles at one end and to venules at another end 3. Wider than blood capillaries Narrower than lymph capillaries 4. Wall consist of thin endothelium and poorly developed basement Wall consist of normal endothelium and basement membrane 5. Contain colourless lymph Contain red blood 6. Have relatively low pressure Have relatively high pressure 7. Absorb tissue fluid from intercellular spaces Add tissue fluid to intercellular cellular spaces

8. Conti.. L ymph capillaries join to form lymphatics , which are: Superficial Lymphatics : accompany veins Deep L ymphatics : accompany arteries L ymph passes through filters: lymph nodes F iltered lymph passes through larger lymphatics and collected into: thoracic duct right lymphatic duct pour lymph into brachiocephalic veins

9. Conti.. Thoracic duct drains Abdomen lower limbs left halves of thorax head and neck left upper limb. Right lymphatic duct drains right halves of thorax head and neck right upper limb.

10. Conti.. lymphatics anastomose freely with neighbours of same side & opposite side. Larger lymphatics = supplied with their vasa vasorum and accompanied by plexus of fine blood vessels which form red streaks seen in lymphangitis .

11. 2. Central Lymphoid Tissues Central lymphoid tissues comprise: B one marrow Thymus .

12. A . Bone Marrow All 'pluripotent' lymphoid stem cells are produced by bone marrow, except during early fetal life are produced by liver and spleen . S tem cells undergo differentiation in central lymphoid tissues, so lymphocytes become competent defensive elements of immune system . Bone marrow helps differentiation of the committed B-lymphocytes which are capable of synthesizing antibodies after getting transformed into plasma cells

13. B . Thymus Situated in anterior & superior mediastina of thorax extending into lower part of neck Grows upto puberty & undergoes atrophy and replaced by fats Only lymphoid organ well-developed at birth Bi-lobed structure Made of 2 pyramidal lobes of unequal size connected by areolar tissues

14. Functions of Thymus 1. Controls lymphoopoiesis , maintains pool of circulating l ymphocytes and reacts to antigenic stimuli 2. Controls development of peripheral lymphoid tissue during neonatal period (Puberty= fully developed) 3. Cortical Lymphocytes of thymus arise from stem cells of bone marrow. 95% T-lymphocytes are autoallergic , short lived (3-5days ) and remnants seen in Hassall’s corpuscles. 5% T-lymphocytes long lived , joins circlulating pool of lymphocytes and acts as uncommitted cells. Some circulating lymphocytes ( spleen) are committed only to specific antigen.

15. 4. Medullary Epithelial cells of thymus secretes: Lymphopoietin : Stimulates lymphocytes production in cortex of thymus and peripheral lymphoid organs Competence- Inducing factor: makes new lymphocytes competent to react to antigenic stimuli 5. No germinal centres in thymic cortex (if appears is autoimmune disease , de fect in thymus)

16. 3. Peripheral Lymphoid Organs Peripheral lymphoid organs comprise: L ymph Nodes Spleen B ecome overactive on stimulation . P rogenies of B- and T-lymphocytes reach these organs where the cells may proliferate and mature into competent cells. M ature lymphocytes join circulating pool of lymphocytes.

17. Lymphatic Follicle (Nodule) C ollections of lymphocytes in body. F ollicle is a spherical collection of lymphocytes with a pale centre known as germinal centre , lymphocytes are loosely packed. C entral cells are larger in size, stain less deeply, and divide more rapidly, than the peripheral cells .

18. a). Lymph Nodes Lymph nodes are small nodules of lymphoid tissue F ound in course of smaller lymphatics . L ymph passes through lymph nodes before reaching the larger lymph trunks. Nodes are : oval or reniform in shape 1-25 mm long L ight brown, black (pulmonary), Creamy white (intestinal) in colour.

19. O ccur in groups (cervical, axillary, inguinal, mesenteric, mediastinal , etc.), but may be a solitary lymph node. Superficial nodes are arranged= along the veins Deep nodes = along the arteries .

20. Cervical lymph nodes form a ring at junction of head & neck and vertical chains in neck. These drain whole of head ?& neck . R ight side drain into right lymphatic duct Left side drain into thoracic duct . Lymph vessels of abdominal wall above a line passing horizontally through umbilicus drain into respective sides of axillary lymph nodes . Lymph vessels below this line drain into i nguinal lymph nodes . This line is called "watershed"

21. Hilum: Lymph node has depression on one side A rtery enters the node, & vein with efferent lymphatic comes out Helium A fferent lymphatics enter the node at different parts of its periphery. L ymph node parts: Fibrous & Reticular framework Lymphatic Channels Cortex Medulla Blood Channels

22. 1. Fibrous and reticular framework L ymph node is covered by capsule . From deep surface of capsule mulitple trabeculae extend into the interior of node , and continuous with fine reticulum which forms supporting framework for the lymphoid tissue.

23. 2. Lymphatic channels S ubcapsular sinus lies beneath the capsule and surrounds the node except at the hilum. A fferent lymphatics of the node open into the subcapsular sinus. Lymph filters through reticulin fibres and leaves node by one efferent lymphatic vessel.

24. 3. Cortex O uter part of lymph node situated beneath subcapsular sinus , absent at hilum . M ade up of lymphatic follicles and traversed by fibrous trabeculae . C ortex is far more densely cellular than medulla. It is divided into: Zone 1: contain loosely packed small lymphocytes, macrophages and plasma cells in the periphery of follicle and extending into medullary cords . Zone 2: contain more densely packed small lymphocytes and macrophages, deep to zone I and limited to cortical and paracortical (inner cortex) areas . Zone 3: includes germinal centre which contains large lymphocytes and macrophages.

25. Conti.. M aturing lymphocytes pass from zone 3 to zone 2 to zone 1 and lymph sinus. According to distribution of B- and T-lymphocytes, cortex divided into: O uter part: contains immature B-lymphocytes. I nner part ( paracortex or thymus dependent zone ): contains T-lymphocytes, between the germinal centre and the medulla, M ature B-lymphocytes (plasma cells)=found in medulla .

26. 4. Medulla C entral part of lymph node, containing loosely packed l ymphocytes, plasma cells, and macrophages .

27. 5. Blood channels A rtery enters at hilum and divides into straight branches which run in the trabeculae . In C ortex the arteries further divide to form arterioles and capillaries with anastomosing loops. C apillaries give rise to venules and veins, which run back to hilum. C apillaries are more profuse around the follicles P ostcapillary venules are more abundant in paracortical zones for lymphatic migration.

28. Haemal Nodes and Spleen S mall lymphatic bodies resembling lymph nodes found in the course of blood vessels. A fferent & efferent lymphatics are absent . S inuses are filled with blood rather than lymph. Haemal nodes may represent an intermediate stage between a lymph node & spleen . In man , spleen is a large haemal node.

29. b). Spleen Largest Lymphoid Organ covered by dense connective tissue capsule Trabeculae extend inwards from capsule Cellular material of spleen divided into White pulp: Comprise of lymphatic tissue containing lymphocytes and macrophages Red pulp: Consists of blood filled venous sinuses

30. Functions of Spleen Phagocytosis: Leukocytes , Platelets, abnormal/old RBCs phagocytized in spleen Storage of blood: 350ml Blood Immunity: B and T lymphocytes i.e. immune response to infection Erythropoiesis: RBC production Storage: Platelets

31. 4. Circulating Pool Of Lymphocytes Contains mature progenies of B & T Lymphocytes called during antigenic stimuli

32. Difference Between T & B Lymphocytes No T-Lymphocytes B-Lymphocytes 1. Origin Bone marrow Thymus Lymphoid tissue Bone marrow Bursa-equivalent Lymphoid tissue 2. Life Span Months to Years Less than 1 month 3. Location Lymph Nodes Perifollicular Germinal centre Spleen Perifollicular Germinal centre Peyer’s Patches Perifollicular Central Follicles 4. Number in Blood 80% 20% 5. Function Cell mediated activity ( T c cytotoxic ) Immunoregulation ( T H helper) Memory T cells Humoral immunity IgG produced by plasma cells Formed by enlargement & modification of B Lymphocytes Memory B cells

33. 5. Epithelio -Lymphoid System Comprises: MALT ( Mucosa Associated Lymphoid T issue )= in digestive system Peyer’s Patches : of ileum of small intestine and lymphoid tissue of vermiform appendix BALT ( Bronchus Associated Lymphoid Tissue )= Respiratory system Waldeyer’s Ring: Posterior 1/3 of tongue, oropharynx, nasopharynx ring of lymphoid tissue under mucous membrane. Its components are Lingual, Palatine, Tubal, and nasopharyngeal tonsils.

34. Peyer’s Patches Waldeyer’s Ring

35. 6. Mononuclear Phagocyte or Macrophage System ( Reticulo -endothelial System) not related to lymphatic system and Macrophage system is highly phagocytic in nature it include : Macrophages of connective tissue, reticular tissue and lungs Monocytes of blood Kupffer's cells of liver Meningocytes of meninges Microglial cells of nervous tissue Foreign body giant cells. E ndothelial cells, fibroblasts, and most leucocytes are not included in this system ( poor phagocytosis)

36. Functions First line of defence of the body : amoeboid and phagocytic properties Macrophages of lymphoid tissue : specific immune responses by the neighbouring cells. S ites of RES ( Reticulo -endothelial System ) are haemopoiesis . Absorbs fat from intestines to be transported to blood

37. Growth Pattern of Lymphoid Tissue Lymphoid tissue of the body is prominent at birth, and grows rapidly during childhood. G rowth ceases at time of puberty , followed by partial atrophy G rowth pattern is shared by lymph nodes, thymus, tonsils, lymphoid tissue of the intestines, and the follicles of spleen. L ymph nodes may enlarge again in response to inflammation (lymphadenitis) or tumour formation (Hodgkin's disease, lymphosarcoma , etc.). Lymph nodes are commonly enlarged by metastasis (spread) of the malignant growths (carcinoma).

38. Functions of Lymphoid System Lymph capillaries absorb and remove large protein molecules from tissue spaces. C ellular debris and foreign particles are conveyed to regional lymph nodes . Lymphatic's (lacteals) help in transportation of fat from gut. Proliferation and maturation of B- and T-lymphocytes is function of lymphoid tissue.

39. 5. Lymph nodes functions: A ct as filters for the lymph and foreign particles are prevented from entering the bloodstream. F oreign particles are engulfed by the macrophages in s inuses. Antigens are also trapped by phagocytes . M ature B-lymphocytes and T-lymphocytes are produced in the node. Both the cellular and humoral immune responses are mounted against the antigen-laden phagocytes. C irculating lymphocytes can pass back into the lymphatic channels within the node Humoral antibodies are freely produced by the lymph nodes .

40. Any Questions? Thank You!