Download MBBS Lymphatic System Lecture PPT

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