Histology II: lymph organs Flashcards
name 5 lymphoid systems (/organs)
bone marrow thymus lymph nodes MALT system spleen
what is the MALT system?
“mucosa associated diffuse lymphoid tissue” -system initiates immune responses to specific antigens encountered along all mucosal surfaces.
What is the chief cellular constituent of lymphatic tissue?
Circulating lymphocytes
Where are T lymphocytes produced?
in the thymus (in young individuals as the thymus shrinks away with age)
(they account for the majority of circulating lymphocytes)
T lymphocyte function?
involved in cell-mediated immunity
roles include: killing infected host cells, activating other immune cells, producing cytokines and regulating the immune response.
What does it mean to be cell-mediated?
the immune response that does not involve antibodies but rather incorporates the activation of macrophages and various lymphocytes
B lymphocyte function?
They are involved in the production and secretion of various circulating antibodies, also called immunoglobulins (IgG), the immune proteins associated humoral immunity.
What does humoral immunity refer to?
Humoral immunity is the process of adaptive immunity manifested by the production of antibodies by B lymphocytes.
What is the major difference between humoral and cell-mediated immunity?
humoral immunity produces antigen-specific antibodies, whereas cell-mediated immunity uses macrophages and cellular apoptosis.
Name 5 cells of the immune system.
T lymphocytes helper T lymphocytes B lymphocytes (plasma cells and memory b's) NK cells (natural killer lymphocytes) APC cells (antigen-presenting cells)
difference between T lymphocytes and helper T lymphocytes?
cytotoxic T cells destroy virus-infected cells and tumor cells
whereas
the helper T cells secrete cytokines to activate or regulate other cells in the immune system
Activated B lymphocytes differentiate into?
Plasma cells and
Memory B cells
Plasma cell function?
synthesize and secrete specific antibodies
Memory B cell function?
memorizes the characteristics of the antigen that activated their parent B cell
so if they later encounter the same antigen, it triggers an accelerated and robust secondary immune response.
APC cell function?
antigen-presenting cells
boost immune responses by showing antigens on its surface to other cells of the immune system.
detects, phagocytizes, and informs the adaptive immune response about an infection
APC cells include what all cells?
macrophages,
Kupffer cells in the liver,
Langerhans´ cells in the epidermis,
dendritic cells of spleen and lymph nodes.
describe the thymus structure
lobules surrounded and connected by connective tissue,
outer cortex,
central medulla,
Hassal’s corpuscles found in medulla
thymal lobules made up of what cells?
Most cells in the lobules are thymolymphocytes (T cells),
markedly more in the cortex than in the medulla.
Epithelioreticular cells form the extensive meshwork of the thymus.
Where are Hassall’s corpuscles found?
In the thymic medulla
What does APC cell refer to?
antigen-presenting cells
Hassall’s corpuscles’ function?
are a potent source of the cytokines that instruct dendritic cells in the thymus to induce development of regulatory T cells
hassall’s corpuscles made of what
derived from epithelioreticular cells
Outer layer of spleen?
fibrous capsule
What are splenic trabeculae?
Fibrous connective tissue that branches into the spleen, connected to the capsule
What is found between splenic trabeculae?
the splenic pulp that contains darker white pulp which is surrounded by lighter red pulp.
White splenic pulp consists of?
a thick accumulation of lymphocytes (surrounding a central artery)
Within the white splenic pulp the branch of the trabecular artery is called?
the central artery
What are the structures consisting of lymphocytes that aggregate around the central splenic arteries called?
lymphatic nodules and lymphatic sheaths.
What do the lymphatic nodules that surround the splenic arteries consist of?
B lymphocytes
What do the lymphatic sheaths that surround the splenic arteries consist of?
chiefly T-lymphocytes
Splenic red pulp consists of?
splenic sinuses and splenic cords.
What are the splenic sinuses lined by?
endothelial cells
What do the splenic cords consist of?
a loose meshwork of reticular cells and reticular fibres
that contain large numbers of erythrocytes, macrophages, lymphocytes, plasma cells and granulocytes.
What is the role of the red splenic pulp?
blood filtration
removal of particulate material, macromolecular antigens, and aged, abnormal, or damaged blood cells from circulating blood.
What is the role of the white splenic pulp?
activation and proliferation of T-lymphocytes
differentiation of B lymphocytes and plasma cells
secretion of antibodies
What are the two types of lymphatic vessels?
Afferent lymph vessels
Efferent lymph vessels
Describe afferent lymph vessels.
convey lymph towards the node and enter it at several points on the convex surface
Describe efferent lymph vessels.
convey lymph away from the node at the hilum, a depression on the concave surface of the node.
What are the supporting elements of the lymph node?
Capsule
Trabeculae
Reticular tissue
What is the capsule of a lymph node made up of?
dense connective tissue
What are lymphatic trabeculae?
extend from the capsule into the substance of the node, forming a gross framework
What is the purpose of the reticular lymph tissue?
reticular cells and reticular fibres form a fine supporting network
A lymph node is divided into what main parts?
darker-stained cortex and lighter-stained central medulla.
The lymphatic cortex is formed by?
lymphatic nodules or lymphatic follicles with the germinal centre in the middle.
The lymphatic medulla consists of?
the medullary cords and medullary sinuses
What do the lymphatic medullary cords contain?
dendritic cells lymphocytes macrophages plasma cells reticular cells
Where does the filtration of lymph occur more specifically?
within a network of interconnected lymphatic channels called sinuses.
Name the 3 types of lymphatic sinuses.
Subcapsular sinuses
Trabecular sinuses
Medullary sinuses
Where are subcapsular sinuses found?
between capsule and lymphatic follicles.
Afferent lymphatic vessels drain lymph into these sinuses.
Where are trabecular sinuses found within lymphnodes?
they pass inwards along the sides of the connective tissue trabeculae and drain into medullary sinuses.
Where are medullary sinuses found?
are spaces that separate the medullary cords, they converge near the lymphatic hilum, where they drain into the efferent lymphatic vessel.
