Structure & Function of Lymph Node & Spleen Flashcards
Give examples of primary/central lymphoid structures
Bone marrow and
thymus
Give examples of secondary/peripheral lymphoid structures
Lymph nodes
Spleen
Tonsils/adenoids
Peyer’s patches in intestine
Define lymph node
Encapsulated collections of lymphoid tissue
Give examples of superficial node groups
In the cervical, axillary and
inguinal regions) can be palpated
Give examples of internal node groups
Mediastinal, para-aortic can be viewed radiologically
T or F: Groups of nodes drain particular territories. Particular territories drain to specific node group
True
What can cause Lymphadenopathy?
Local inflammation - infection
Systemic inflammatory - autoimmune
Malignancy - lymphoma / leukaemia
Sarcoidosis, Kikuchi’s lymphadenitis, Castlemans Disease, IgG4
Superficial infection may see red lines extending from an inflamed lesion
Lymphangitis - regional lymphadenopathy
_________ lymphadenopathy may be the first sign of underlying malignancy
Superficial
What is a sentinel lymph node?
The first lymph node to which cancer cells are most likely to spread
Describe the direction of lymph nodes
Afferent lymphatics penetrate the capsule and drain into subcapsular sinus
From there lymph percolates through the node
Lymph enters medullary cords and sinuses
Sinuses merge at hilum and form efferent lymphatics
Lymph rejoins extranodal lymphatic circulation
What are the three important regions of lymph nodes?
Cortex
Paracortex
Medulla
Give examples of lymph organs
Spleen - removes old RBCs
Thymus - development and maturation of T lymphocytes
Red bone marrow - same as thymus
Some lymphatic tissue is located in the…
Tonsils, appendix, and in the walls of the gastrointestinal tract
On average, an adult has around 400 to 450 different lymph nodes spread throughout the body – with the majority located within the..
Abdomen
Why are lymph nodes palpable during infection?
Each node contains T/B lymphocytes, and other immune cells. They are exposed to the fluid as it passes through the node, and can mount an immune response if they detect the presence of a pathogen. This recruits more inflammatory cells into the node
Lymph fluid enters the node through ________ lymphatic channels and leaves the node via ________ channels
Lymph fluid enters the node through afferent lymphatic channels and leaves the node via efferent channels
__________- located within the sinuses of the lymph node act to filter foreign particles out of the fluid as it travels through
Macrophages
Superficial vessels arise in the _________ tissue, and tends to accompany _________ flow. They eventually drain into deep vessels
Superficial vessels arise in the subcutaneous tissue, and tends to accompany venous flow. They eventually drain into deep vessels
Deep vessels drain the deeper structures of the body, such as the internal organs. They tend to accompany _____ arteries
Deep
The drainage of lymph begins in ____________, which start as blind ended capillaries and gradually develop into vessels. These vessels travel proximally, draining through several lymph nodes
Lymph channels
Vessels empty into lymphatic trunks (also known as collecting vessels) – and these eventually converge to form the..
Right lymphatic duct and the thoracic duct
The right lymphatic duct is responsible for draining the lymph from the..
Upper right quadrant of the body - right side of the head and neck, the right side of the thorax and the right upper limb
The thoracic duct is responsible for draining the lymph from the..
Rest of the body
The thoracic and right lymphatic duct then empty into the venous circulation at the __________ veins, via the right and left venous angles
Subclavian
Lymph is a _____________ fluid that is transparent and yellow
Transudative
Lymph is formed when fluid leaves the capillary bed in tissues due to..
Hydrostatic pressure
The composition of lymph is fairly similar to that of..
Blood plasma
B cell follicles in lymphoid organs can exist in either of two states. What are they?
Quiescent (primary) follicles - naïve B cells migrating extensively in search of cognate antigen
Activated (secondary) follicles - central germinal center (GC) full of B cell blasts undergoing events associated with antibody affinity maturation
Antigen-antibody complexes in a follicles are captured by..
Follicular dendritic cells (FDCs) - mesenchymal and form meshworks through the germinal centre
The antigens on the FDCs are then presented to naive B cells (T helper cells assist)
GC B cells cycle through the two distinct zones of the germinal center: the light zone and the dark zone. As they undergo rapid and mutative cellular division, B cells of the germinal center’s dark zone are known as…
Centroblasts
GC B cells cycle through the two distinct zones of the germinal center: the light zone and the dark zone. Once B cells have stopped proliferating in the dark zone and moved to the light zone, they are known as __________, and are subjected to selection by ______________ cells in the presence of ________________
GC B cells cycle through the two distinct zones of the germinal center: the light zone and the dark zone. Once B cells have stopped proliferating in the dark zone and moved to the light zone, they are known as centrocytes, and are subjected to selection by follicular helper T (TFH) cells in the presence of follicular dendritic cells (FDCs)
There are three possible fates for GC B cells that have been positively selected in the light zone..
Plasma cell
Memory B cell
B cell licensed to return to the dark zone for proliferation and mutation
How do T cells assist in the light zone?
FDCs present antigens to B cells
B cells bind and internalise the antigen
Antigen bound by MHC class II, presented to T cell
What type of cells does the medullary cord contain?
Plasma cells
B cells
Macrophages
What type of cells does the medullary sinuses contain?
Histiocytes, reticular cells
Lymph then drains into efferent vessels
Give examples of conditions that can cause granulomatous lymphadenitis
Sarcoidosis
Give examples of conditions that can cause granulomatous inflammation
TB
Stimulation of an immune reaction in a lymph node can cause a mixed pattern of changes. Explain this
What are the two key aspects of spleen?
Diaphragmatic surface
Visceral surface - Left Kidney, gastric fundus, tail of pancreas, splenic flexure of colon
Supply and drainage of spleen
Supplied by splenic artery (branch of coeliac trunk) and drained by splenic vein (with sup. mesenteric vein forms portal vein)
What are the two major functional zones of the spleen?
Hematogenous red pulp and the lymphoid white pulp
What does the red pulp of the spleen contain?
Cords (macrophages and some fibroblasts and cells in transit (RBC, WBC, PC and some CD8+ T cells) and sinusoids (fenestrated, lined by endothelial cells, supported by hoops of reticulin)
Why is the spleen red?
Spleen contains connective tissue (cords of Bilroth) and sinusoids engorged with blood (hence the red)
Cords in the spleen, contain lots of monocytes, generally lots of…
White blood cells and erythrocytes
What does the white pulp of the spleen contain?
Periarteriolar lymphoid sheath (CD4+ lymphoid cells)
This is expansed by lymphoid follicles (B cells, may show reactive changes as in lymph node)
What causes Hyposplenism?
Splenectomy - Coeliac disease, sickle cell disease, sarcoidosis
Which feature would you see due to hyposplenism?
Howell-Jolly bodies
Triad for Hypersplenism
Splenomegaly
Fall in one or more cellular components of blood (cytopenias)
Correction of cytopenias by splenectomy
