Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Lymphatic System Lecture PPT
LYMPHATIC SYSTEM
INTRODUCTION
? Lymphatic system is also called as immune system.
? This system consists of following structures
? Lymphatic vessels:-- Thin walled vessels collect
lymph and drain into vein.
? Specific lymphatic organ:-- Lymphatic tissue
surrounded by capsule, e.g. Lymph node, spleen
and thymus.
? Lymphatic tissue found within tissue of other
organ:-- Not surrounded by capsule, e.g. Tonsil,
peyer's patches.
Components of the Lymphatic System
? Lymph Tissue fluid drained
24-
by lymphatic vessels.
3
Consists of tissue fluid, proteins,
fat & particulate matters.
? Lymphatic Vessels
? Lymphatic Capillaries
? Lymphatic Vessels
? Lymphatic Trunks
? Lymphatic Ducts
? Lymphatic Organs
? Thymus
? Lymph Nodes
? Spleen
? Tonsils
? Lymphatic cells
? The specific immune response is evoked by
lymphocytes.
? Lymphocytes are of two types, B and T.
? They are derived from common stem cells in the
bone marrow.
? B lymphocytes mature and become
immunocompetent in the bone marrow.
? T lymphocytes mature and become
immunocompetent in thymus and migrate to
other peripheral lymphoid organ.
? The defence mechanism mediated by B
lymphocytes is called humoral immune response.
? The defence mechanism mediated by T
lymphocytes is called cellular immune response
% of lymphocytes in various lymphoid organ
B lymphocytes
T lymphocytes
Bone marrow
90
10
Thymus
0
100
Lymph node
40
60
Spleen
55
45
Blood
30
70
LYMPH NODE
? GENERAL FEATURE--
? Oval or bean shaped situated along the course of
lymphatic vessels.
? They serve as filter of lymph, removing particulate
matter and bacteria, thereby localising and
preventing the spread of infection.
? Lymph node usually found in groups e.g. axilla,
inguinal region, root of lung.
? COMPONENTS/STRUCTURE--
? Stroma : Connective tissue framework
-Capsule
-Trabeculae
-Reticular stroma
? Parenchyma : Lymphoid tissue
-Cortex
-Paracortex (inner cortex)
-medulla
? Connective tissue framework--
? Capsule and trabeculae-
*Lymph node is surrounded by a thin connective
capsule which sends trabeculae into the interior.
*Beneath the capsule is the subcapsular sinus.
*The subcapsular sinus receives afferent lymphatic
vessels and is continuous with trabecular sinus.
*Trabecular sinus becomes continuous with the
medullary sinus.
? Reticular stroma-
*Made of reticular fibre and phagocytic reticular cells.
*Gives structural supports to lymphoid cells.
? Parenchyma-
? Cortex ? Peripheral part of the lymph node situated deep to
the capsule.
? It contains
1.Subcapsular sinus
2.Lymphatic nodules- with or without germinal centres formed
mainly of B lymphocytes.
a)Primary nodule-lymphatic nodule without germinal centre.
b)Secondary nodule-nodule with germinal centre.
? The germinal centre contains large lymphoblast with more
cytoplasm and lighter nuclei as compared to periphery of
nodule.
? Paracortex-
? It is the inner cortical zone, does not have
precise boundary with outer cortex.
? Contains mainly T lymphocytes and called
thymus-dependent zone.
? The dense lymphoid tissue in the paracortex
becomes continuous with medullary cords.
? Medulla-
? Has two components, medullary cords and
medullary sinuses.
? Medullary cords- are branching and
anastomosing cords of lymphoid tissue
contains mainly B lymphocytes, few plasma
cells and macrophages.
? Medullary sinuses- drain into the efferent
lymphatic vessels found at the hilum.
Flow of lymph through lymph node
Afferent lymphatic vessels
Subcapsular sinus
Trabecular sinus
Medullary sinus
Efferent lymphatic vessels
SPLEEN
? GENERAL FEATURES--
? Spleen is the largest lymphoid organ.
? Present in the left hypochondrium.
? COMPONENTS/STRUCTURE--
? A)Connective tissue framework
? Capsule
? Trabeculae
? Reticular stroma
? B)parenchyma
? White pulp
? Red pulp
? Connective tissue framework--
? Capsule-
? Covers the spleen completely.
? Lies deep to the peritoneum.
? Formed by dense collagenous connective tissue and
few smooth muscle fibres.
? Trabeculae-
? Given off from the capsule into the substance of
spleen.
? Reticular stroma-
? Made of reticular fibres and associated phagocytic
reticular cells.
? Parenchyma--
? The interior of spleen shows rounded white/grey
areas surrounded by red matrix.
? These grey area are called white pulp and the dark
red matrix called red pulp.
? White pulp--is the lymphatic tissue sheath that
surrounds the central artery (eccentric position)
? It contains lymphocytes and macrophages in a
reticular connective tissue meshwork.
? This peri-arterial lymphatic sheath also contain
lymphatic nodules with germinal centre.
? These nodules are called splenic nodules or
malpighian corpuscles.
? Lymphocytes in white pulp is T while in nodule B
lymphocytes.
? Red pulp-- consist of network of inter-
anastomosing splenic cords.
? Splenic cords-- made up of reticular cells and
reticular fibres containing B and T lymphocytes,
macrophages, plasma cells, RBC, and granulocytes.
? These splenic cords are also called as "cords of
Billroth".
Splenic Circulation
? Blood enters via splenic artery at hilus
? Splenic artery trabecular arteries (within
trabeculae).
? Trabecular arteries central arteries(covered by a
peri-arterial lymphatic sheath) [ PALS].
? Central artery terminate into straight vessels called
penicilli.
? Penicilli shows localiszed thickening (ellipsoid)
Penicilli continue as arterial capillary.
? The mode of blood flow between arterial capillaries
and splenic sinuses is not clear.
? Two different theories open and closed circulation
have been proposed.
? According to "closed circulation theory" arterial
capillaries open directly into splenic sinuses that drain
into tributaries of splenic vein.
? According to "open circulation theory" the arterial
capillaries open and pour their blood into splenic cord
of red pulp.
? Pulp veins drain into trabecular veins.
? Trabecular veins drain into splenic vein at the hilus.
Splenic Cords and Splenic Sinusoids
Open and Closed Circulation in Spleen
Spleen
Functions of the spleen
? Filtration of blood.
? Storage of blood.
? Formation of blood cells during fetal life.
? Aged and abnormal RBCs are destroyed in the
spleen.
? Immune response.
THYMUS
? Covered by a capsule which extends to form
Trabeculae.
? Trabeculae extends inwards to forms
numerous incomplete lobules (lobulated
appearance).
? Each lobule consists of dark staining outer
cortex and a light staining inner medulla.
? Cortex contains densely packed lymphocytes (No
lymphatic nodules).
? Medulla contains fewer lymphocytes but more
epithelial reticular cells.
? Medulla also contains Thymic (Hassall's)
Corpuscles.
? Thymic (Hassall's) Corpuscles are oval structures
consisting of round whorls of flattened epithelial
cells.
Thymus
Function of thymus
? Maturation of T lymphocytes.
? Mature T lymphocytes then carried from
thymus to the lymph node, spleen, and other
lymphatic tissues.
? Thymopoietin induces T cell production and
maturation.
? Thymosin supports T cell activities.
? Thymus gets atrophied after puberty.
PALATINE TONSIL
? Collection of lymphoid tissue in mucosa of
oropharyngeal isthmus.
? Consist of lymphatic nodules within diffused
lymphoid tissue .
? Lateral surface is covered by capsule.
? Medial surface is pitted by 10-20 tonsillar crypts,
lined by stratified squamous non-keratinised
epithelium.
? It has only efferent vessels.
? Infection of tonsil is called tonsillitis.
? Function
? Production of lymphocytes.
? Immunological responses.
This post was last modified on 30 November 2021