Histology of Hematopoietic and Lymphoid Organs Practice Flashcards

This set of vocabulary flashcards covers the histological structures and cellular components of hematopoietic and lymphoid organs, including the bone marrow, thymus, spleen, lymph nodes, and palatine tonsils.

Red Bone Marrow

Hematopoietically active marrow where most of the forming cells are Red Blood Cells (RBCs).

Yellow Bone Marrow

Inactive marrow characterized by fat accumulation.

Megakaryocyte

A large cell found in the bone marrow responsible for the production of platelets.

Osteoclast

A type of bone cell involved in bone resorption, often seen in the bone marrow environment near trabeculae.

Osteoblast

A bone-forming cell found on the surfaces of bone matrix.

Parenchyma (Lymphoid)

The functional part of the organ, typically composed of reticular connective tissue, reticular fibers, reticular cells, and lymphocyte aggregates.

Germinal Center

The central area of a lymphatic nodule (follicle) where active stimulation and proliferation of B lymphocytes occur.

Hassall’s Corpuscles

Characteristic whorl-like formations of concentrated, flattened thymic epithelial cells found in the thymic medulla, with a keratinized center.

White Pulp

The region of the spleen containing immune system cells (lymphatic nodules and periarterial lymphoid sheaths) that respond to pathogens in the blood.

Red Pulp

The splenic region responsible for filtering blood, removing foreign objects or worn-out red blood cells; it consists of splenic cords (of Billroth) and venous sinuses.

Central Artery

An artery located within the white pulp of the spleen, often surrounded by a periarterial lymphoid sheath (PALS).

Thymic Epithelial (Reticular) Cells

Cells unique to the thymus that form a structural framework in both the cortex and medulla.

Subcapsular Sinus

The space situated immediately deep to the lymph node capsule where afferent lymphatic vessels empty.

Medullary Cords

Columns of lymphoid tissue found in the medulla of the lymph node, separated by medullary sinuses.

Hilum

The indentation of a lymph node or spleen where blood vessels enter and leave, and where efferent lymphatic vessels exit.

Tonsillar Crypts

Deep surface invaginations in the palatine tonsils whose lumens may contain desquamated epithelial cells, lymphocytes, and bacteria.

Palatine Tonsil Epithelium

The stratified squamous nonkeratinized epithelium that covers the surface of the palatine tonsil.

High Endothelial Venules (HEV)

Specialized venules found in the paracortical region of lymph nodes between the cortex and medulla.

Trabeculae

Connective tissue partitions that extend from the capsule into the parenchyma of lymphoid organs, carrying vascular, nerve, and lymph structures.

MALT

Mucosa-associated lymphoid tissue, which includes structures like Peyer patches and tonsils.