Lymphoid Organs
Red pulp
Acidophilic, soft, dark, red masses in H&E part of spleen where majority of RBC's are
Splenic pulp
Another term for the parenchyma of the spleen
Ampulla of Thoma
Another term for the terminal branch of penicillar artery
Medullary cords
Arrangement of the medulla of lymph nodes; anastomosing cords; medullary sinuses would branch and anastomose and would fragment the parenchyma into strands or cords
White pulp
Basophilic, dark-staining in H&E part of spleen where majority of lymphocytes are
Subcapsular/ Primary/ Germinal sinus
Beneath the capsule; the space between the capsule & nodule
Splenic artery => (enter hilum and follow trabecula) trabecular artery =>reaches 2mm diameter (leaves trabecula) => enters white pulp => acquires PALS => artery surrounded by CT and becomes Central artery => diameter is 25 micra => enters red pulp => branch repeatedly => forms penicillar artery (penicillus of Ruysch) which has at least 5 branches
Blood vessels in the spleen
Venous sinuses
Blood-filled spaces of the red pulp
Thymus
Broad, flat bilobed mass of lymphoid tissue found just beneath the upper part of the sternum
Reticular CT Dense irregular fibrous CT
CT of stroma of lymphoid organs (2)
Dense fibrous CT
CT of the capsule of the thymus
Germinal center (of Flemming)
Cells are actively dividing therefore nodes produce lymphocytes; arranged diffusely
Bilroth's cord or Splenic cord
Cells in the red pulp are arranged in cords with spaces in between
Parenchyma
Cellular part of lymphoid organs
Germinal center (of Flemming)
Central pale-staining part of the cortex of lymph nodes; medium and large lymphocytes
Medulla
Central part of the parenchyma of lymph nodes; forms cellular cords; no lymphatic nodules
Lymphoid Organs
Collection of lymphoid tissue in fixed location & with definite structural characteristics
Tonsils
Collection of lymphoid tissues in the mucous membrane of the upper part of the respiratory & digestive parts
Lymphoid CT
Component CT of parenchyma; responsible for the production of lymphocytes
Lymphocyte
Component cell of parenchyma of lymphoid organs
Cortex Medulla
Components of the parenchyma of the lymph node (2)
White pulp Red pulp
Components of the parenchyma of the spleen (2)
Cortex Medulla
Components of the parenchyma of the thymus (2)
Capsule Trabeculae Septa Reticular network
Components of the stroma of lymphoid organs (4)
Capsule Trabeculae Network of reticular fiber & cells
Components of the stroma of the lymph node (3)
Capsule Trabeculae Network of reticular fibers & cells
Components of the stroma of the spleen (3)
Capsule Septa Trabeculae
Components of the stroma of the thymus (3)
Reticular fibers B and T lymphocytes Macrophages
Composition of the splenic cord (3)
Hilum
Concavity or slight indentation of the lymph node where the entering BV emerge and exit
Cortex
Darker, peripheral part of the parenchyma of the thymus
Monocytes Plasma cell Macrophage
Differentiated B-lymphocytes of the parenchyma of lymphoid organs (3)
Afferent lymphatic vessels => subcapsular => cortical => medullary => efferent lymphatic vessels
Direction of the filtration of lymph
Trabeculae
Divide the parenchyma into smaller components called splenic lobule
Incomplete basal lamina
Due to this cell can enter into the venous sinuses of the spleen
Stave cells
Elongated endothelium that lines the sinusoids
Trabeculae
Extensions of the septa of the thymus which end at the cortico-medullary junction
Lymph
Extracellular fluid from the blood
Capsule of the spleen
Fibro-muscular; contains smooth muscle fibers
Stroma
Framework/lattice/scaffolding of lymphoid organs
Filtration of lymph Production of lymphocytes Immune defense
Functions of the lymph node (3)
-Filtration of blood -Blood reservoir -Iron storage -Production of lymphocytes -Immunologic defense
Functions of the spleen (5)
Medullary sinus
In the medulla; the space between medullary cords or between the trabeculae & medullary cords
Lymph node
It is an aggregation of lymphoid tissue in the course of lymphatic vessels; secondary lymphoid organ
Thymus
It is seeded with stem cells coming from the yolk sac and it is a site where T-lymphocytes mature; first organ seeded with lymphocytes from the bone marrow
Spleen
Largest lymphoid organ (about the size of a person's fist)
Left hypochondriac region
Location of the spleen
Between sternum and heart; anterior mediastinum
Location of the thymus
Pulp arteriole
Longest segment of the penicillar artery (2/3)
Plasma proteins Bacteria Cells
Lymph components (3)
Lymph node Spleen Thymus
Lymphoid organs as an organ (3)
Tonsils Peyer's Patch Confluent nodules of appendix
Lymphoid organs as part of an organ (3)
Splenic artery
Main blood supply of the spleen which become smaller venous sinuses
Lymphoid Organs
May be considered as an organ in themselves or part of an organ
Hassal's corpuscle or thymic corpuscle
Nest of epithelioid (epithelial-like) cells containing keratohyaline granules arranged concentrically in the thymus; unknown significance
Lymphatic nodules
Nodular arrangement of the cortex of lymph nodes
Axilla Inguinal area Abdominal area Cervical area (great vessels of the neck) Mesentery Prevertebral region
Occurences of the lymph nodes (6)
Endoderm
Origin of the thymus
Medulla
Pale, central part of the parenchyma of the thymus
Corona
Peripheral dark-staining part of the cortex of lymph nodes; small lymphocytes (big nucleus and scanty cytoplasm)
Cortex
Peripheral part of the parenchyma of the lymph node
Plasma cell
Present in the parenchyma of lymphoid organs and produces antibodies
Filtration of lymph
Primary function of lymph nodes
Filtration of blood
Primary function of the spleen
Thymus
Primary lymphoid organ
Dendritic cells (macrophages of lymph nodes) => processes antigens (mostly CHON/CHO) to stimlulate immune system => competent lymphocytes
Process of immune defense in the lymph nodes
Parenchyma
Represents functional component of the lymphoid organs because of lymphocyte
Lymph node
Rounded or kidney-shaped organ with an outer convex surface and inner concave surface
Immune defense
Secondary function of lymph nodes
Spleen and mouth
Secondary lymphoid organs
Sheathed artery
Segment of the penicillar artery with wall thickened with reticular cells and fibers and macrophages
Pulp arteriole Sheathed artery Terminal branch
Segments of penicillar artery (3)
Trabeculae or septa
Strands of CT that develop from the capsule, dividing the organs into smaller components or lobules
Splenic lobule
Structural & functional unit of the spleen
Reticular CT
Supporting CT of lymph nodes
Reticular network
Supports the component cells in the lymphoid organ (parenchymal cells)
Mucosa associated lymphoid tissues (MALT)
System of lymphoid tissues that lines body organs and cavities
F; arterioles-capillaries
T/F Each penicillar artery would divide into 2-3 arterioles and would acquire the sheath of Schweigger-Seidel
T
T/F In the lymph node, afferent vessels enter the convex side and efferent vessels exit from the concave side
F; CT-endothelium
T/F Lymphatic sinuses are lined with CT
F; present-absent
T/F Lymphatic sinuses are present in the spleen
F; not all-all
T/F Not all vessels in lymph nodes contain valves to ensure one-way flow of lymph: afferent (towards the node), efferent (away for the node)
T
T/F Sheathed capillaries would continue as simple capillaries and would terminate in the venous sinuses
F; elastic-fibrous
T/F The capsule of lymph nodes are made up of dense elastic CT and is thickened at the hilum
T
T/F The spleen has a hilus but doesn't have afferent lymph vessels
T
T/F Within lobules of the thymus, there are no networks or reticular tissue. Instead, reticular cells are present which will be connected by their processes. The reticular cells will form a reticulum which will support the cellular compound (parenchyma) (shorter and smaller than septa)
T
T/F The thymus has no afferent lymph vessels or lymphatic sinuses
Subcapsular/ Primary/ Germinal Cortical/ Secondary Medullary
The 3 lymphatic sinuses
Parenchyma of the thymus
The lymphocytes are diffusely arranged and will not form nodules only the inner lighter medulla and darker peripheral cortex of the Thymic lobules
When RBC is destroyed, iron is removed and stored in spleen
The reason for the function of the spleen as iron storage
Due to the suspended lymphocytes (stem cells)
The reason why the thymus is the primary lymphoid organ
Lymphatic sinuses
The spaces between cords and lymphatic tissues in lymph nodes where the lymph will pass through
Sheathed artery + sheath of Schweiger-Seidel
These make up the splenic ellipsoid
CT Capsule
This encloses all the lymphoid organs
Peri-arterial lymphoid sheath (PALS)
This is present in the white pulp since the lymphoid tissue in the white pulp are always associated with an artery; arranged diffusely/form nodules which may have a germinal center
Septa
This structure in the thymus divides the lobes to lobules (cortex & medulla); inward extensions of the capsule
Solid Organs Hollow Organs
Types of organs (2)
Discontinuous capillaries
What type of capillary are the venous sinuses?
Bone marrow
Where B-lymphocytes are honed in
Thymus
Where immunocompetent T-lymphocytes are honed in before being distributed to other lymphoid organs
Cortical/ Secondary sinus
Within the cortex; the space between the trabeculae & nodule
