lymphoid tissue
TRANSCRIPT
LYMPHOID TISSUES
Maj Dr Rishi PokhrelMBBS, MD
Lecturer, NAIHSFAIMER Fellow, USA
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Lymphatic System-Organs
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
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
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
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
• 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
Development
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• 3rd Endodermal pouch
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.
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
Location
• Present around large arteries or veins– Cervical LN– Axillary LN– Coeliac and mesenteric LN– Inguinal LN
Applied anatomy
• Lymphadenitis• Metastasis
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
The Spleen
• Size: 1 X 3 X 5 inches• Weight: 7 ounce• Relation: 9-11 ribs in mid-
axillary line
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).
RELATIONS
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
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
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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