Lymphoid tissue
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Transcript of Lymphoid tissue
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LYMPHOID TISSUES
Maj Dr Rishi PokhrelMBBS, MD
Lecturer, NAIHSFAIMER Fellow, USA
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Lymphatic System-Organs
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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
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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
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Formation & flow of lymph
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CLASSIFICATIONI. FUNCTIONAL
LYMPHOID ORGANS
CENTRAL PERIPHERAL
THYMUS
BONE MARROW
LYMPH NODE
SPLEEN
MALT, GALT
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II. MORPHOLOGICAL
LYMPHOID ORGANS
DISCRETE DIFFUSE
LN, SPLEENTHYMUS, TONSIL BM, PEYER’S PATCHES
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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
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THYMUS• Introduction• Gross anatomy• development• Histology -Circulation -Relation with
immunology• Functions• Age changes• Recent advances
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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
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• 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
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Development
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• 3rd Endodermal pouch
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BLOOD THYMUS BARRIER
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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.
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Applied
• Myasthenia gravis
• DiGeorge syndrome-absent-thymus & parathyroid ,defect in cardiac outflow tract
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Lymph Nodes
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• Capsule – Trabeculae, hilus-collagenous framework
• Lymph flow– Retculin Meshwork-sinuses– Subcapsular Sinus– Cortical Sinuses– Medullary Sinuses– Eff Lymph Ch
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Location
• Present around large arteries or veins– Cervical LN– Axillary LN– Coeliac and mesenteric LN– Inguinal LN
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Applied anatomy
• Lymphadenitis• Metastasis
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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
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The Spleen
• Size: 1 X 3 X 5 inches• Weight: 7 ounce• Relation: 9-11 ribs in mid-
axillary line
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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).
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RELATIONS
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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
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BLOOD SUPPLY
• Splenic artery- largest branch of coeliac axis
• Splenic vein joins superior mesenteric vein to form portal vein
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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.
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STRUCTURE
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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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