Lymphoid tissue

Lymphoid tissue

1. LYMPHOID TISSUES Maj Dr Rishi Pokhrel MBBS, MD Lecturer, NAIHS FAIMER Fellow, USA

2. 2 Lymphatic System-Organs

3. Lymphatic System Not a primary tissue type but a variety of connective tissue. Consists of: - lymph - network of vessels - lymph nodes and nodules, MALT - tonsils - spleen - thymus gland - bone marrow

4. CELLS OF LYMPHATIC SYSTEM Chief cells are lymphocytes- B lymphocytes T lymphocytes Natural killer cells Supporting cells - interact with lymphocyte Present antigens to Lymphocytes OTHER TYPE OF WBC’S -monocyte -macrophages -neutrophils -eosinophil -basophils 4

5. Formation & flow of lymph

6. 7 CLASSIFICATION I. FUNCTIONAL LYMPHOID ORGANS CENTRAL PERIPHERAL THYMUS BONE MARROW LYMPH NODE SPLEEN MALT, GALT

7. 8 II. MORPHOLOGICAL LYMPHOID ORGANS DISCRETE DIFFUSE LN, SPLEEN THYMUS, TONSIL BM, PEYER’S PATCHES

8. FUNCTIONS protects body against foreign material - The site of clonal production of immunocompetent  lymphocytes and macrophages in the specific immune response. assists in circulation of body fluids between cells and bloodstream - Maintains pressure & volume of extracellular fluid by returning excess water to the circulation. transports dietary fats

9. THYMUS Introduction Gross anatomy development Histology -Circulation -Relation with immunology Functions Age changes Recent advances 10

10. THYMUS Bi-lobed organ Located in superior mediasternum ant to heart and great vessels. largest and most active during prenatal period and infancy after puberty it decreases in size Capsule- incomplete septa No Afferent lymphatics

11. composed of lymphatic tissue subdivided into lobules immature T cells originating in the bone marrow migrate to thymus via blood in thymus, cells develop into mature T cells for release into circulation thymic hormones aid in maturation of T cells THYMUS

12. Development 14 3 rd Endodermal pouch

13. BLOOD THYMUS BARRIER 15

14. 16 Changes of Thymic Structure with Age (involution) Largest at birth fully functional at 20 weeks of foetal life. progressive involution of adipose tissue. Accelerated by adrenal corticosteroids and sex hormones In juveniles: isolation of cortical compartments, reduction of cortical and medullary volume, and appearance of more, larger blood vessels, until the adult thymus is mainly dominated by fat.

15. Applied Myasthenia gravis DiGeorge syndrome-absent-thymus & parathyroid ,defect in cardiac outflow tract 17

16. 18 Lymph Nodes

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20. 22 Capsule – Trabeculae, hilus-collagenous framework Lymph flow Retculin Meshwork-sinuses Subcapsular Sinus Cortical Sinuses Medullary Sinuses Eff Lymph Ch

21. Location Present around large arteries or veins Cervical LN Axillary LN Coeliac and mesenteric LN Inguinal LN

22. Applied anatomy Lymphadenitis Metastasis

23. The Spleen largest lymphatic organ In upper left quadrant of the abdominal cavity. size of a cupped hand Functions filters the blood react immunologically to blood-borne antigens, removes defective blood cells store blood cells & platelets hematopoiesis 25

24. The Spleen Size: 1 X 3 X 5 inches Weight: 7 ounce Relation: 9-11 ribs in mid-axillary line

25. LIGAMENTS Gastrosplenic ligament passes to greater curvature of stomach (carries short gastric and left gastroepiploic vessels) Lienorenal ligament passes to posterior abdominal wall (contains splenic vessels and tail of pancreas).

26. RELATIONS

27. RELATIONS Posteriorly - left dome of diaphragm separating it from pleura, left lung and 9th, 10th & 11th ribs Anteriorly - stomach Inferiorly - splenic flexure of colon Medially - left kidney Tail of pancreas is related at the hilum of spleen

28. BLOOD SUPPLY Splenic artery- largest branch of coeliac axis Splenic vein joins superior mesenteric vein to form portal vein

29. 31 STRUCTURE It has a thin fibrous capsule, to which peritoneum adheres . The fibrous septae of capsule extends into spleen as trabeculae between which lies splenic pulp . Red pulp This has large numbers of red blood cells (RBCs). It consists of splenic sinuses , separated by splenic cords (of Billroth ) White pulp WBC, mainly lymphocytes around the central artery in a cylindrical fashion - periarterial lymphatic sheath (PALS) of the artery.

30. 32 STRUCTURE

31. CLINICAL ANATOMY During splenectomy, close relation of pancreatic tail to the hilum and splenic pedicle must be remembered; it is easily wounded . Stab wound of posterior left chest may penetrate diaphragm and damage the spleen. Spleen is the commonest organ ruptured by blunt trauma . Accessory spleens may occur near the hilum, in the tail of pancreas, omentum, mesentery, ovary and even testis.

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