Lymph node and spleen histology

Pictured is a lymph node, what are the black arrows pointing at

Capsule

Pictured is a lymph node, what are the white arrows pointing at

Trabecula

Recall which type of CT proper provides structural scaffolding to the lymphocytes within the lymph node and spleen

Reticular CT network

Outlined in white of this lymph node is

Nodular cortex

Outlined in pink of this lymph node is

Paracortex

Which lymphocyte predominates in the nodular cortex

B lymphocytes

Which lymphocyte predominates in the diffuse paracortex

T lymphocytes

Pictured is a nodular cortex, what is pink?

Mantle

This is a nodular cortex, what is in blue?

Germinal center

Germinal center

Has proliferating B lymphocytes that are clonally dividing in response to antigenic stimulation.

In this lymph tissue, what is yellow?

Medullary sinus

In this lymph tissue, what is purple?

Medullary cord

Medullary cords

More densely populated with lymphocytes, plasma cells, and macrophages

In this lymph tissue, what is bracketed in black?

Subcapsular sinus

In this lymph tissue, what is bracketed in magenta?

Cortical sinus

Basic flow of lymph through a lymph node

• lymph enters node from afferent lymphatics

• lymph flows through subcapsular sinus

• lymph flows into cortical sinuses

• lymph flows to medullary sinuses

• lymph flows out of the node via the efferent lymphatics at the hilus

List two ways that lymphocytes are delivered to a lymph node.

• Through the blood, via high endothelial venules (HEVs)

• Through the lymph, via afferent lymphatic vessels

Pictured is spleen tissue, what is in green?

Trabecula with smooth muscle

Pictured is spleen tissue, what is in purple?

Capsule (spleen)

Do capsule or trabeculae contain smooth muscle in the spleen?

They both can, it varies with the species

Pictured is spleen, what is in blue?

Red pulp

Pictured is spleen, what is pink?

White pulp

T lymphocytes are predominant in this spleen tissue

periarterial lymphatic sheath (PALS) (diffuse lymphoid tissue)

B lymphocytes are predominant in this spleen tissue

splenic follicles (nodular lymphoid tissues)

This is red pulp, what is orange?

Splenic cord

This is red pulp, what is pink?

Splenic sinus

Determine which direction red blood cells (RBCs) are passing between these structures during the filtering process that removes senescent RBCs. (cords→sinuses or sinuses→cords)

Cords → sinuses

The spleen receives the blood that is delivered to the organ, then “subdivides the labor” between the two pulps. Which pulp functions like a lymph node and processes foreign antigens? Which pulp functions to “capture and recycle” old red blood cells?

1. White pulp

2. Red pulp