AN70.1-AN71.2 | Glands & Lymphoid tissue — Glossary

The structural unit of compact bone (Haversian system) consisting of concentric lamellae around a central canal containing blood vessels

The central canal of an osteon containing blood vessels, nerves, and loose connective tissue; runs parallel to the long axis of the bone

Perforating canals that connect adjacent Haversian canals horizontally; carry blood vessels between osteons

A bone-forming cell that synthesises and secretes osteoid (unmineralised bone matrix); lines bone surfaces; expresses alkaline phosphatase

A mature bone cell trapped in a lacuna; communicates with other osteocytes via canaliculi; senses mechanical stress (mechanotransduction)

A large multinucleated bone-resorbing cell derived from monocyte-macrophage lineage; occupies Howship's lacunae; has a ruffled border for acid secretion

The most common cartilage type with a glassy matrix of type II collagen and aggrecan; found in trachea, costal cartilage, and articular surfaces

Cartilage with abundant elastic fibres in addition to type II collagen; found in pinna, epiglottis, and Eustachian tube; never calcifies

Cartilage with dense type I collagen bundles and no perichondrium; found in intervertebral discs, pubic symphysis, and menisci

The connective tissue covering of cartilage with an outer fibrous layer and inner chondrogenic layer; absent in fibrocartilage and articular cartilage

A cluster of 2-4 chondrocytes in a shared lacuna, derived from a single parent cell by mitotic division

A secretory unit of an exocrine gland producing watery, enzyme-rich secretions; pyramid-shaped cells with basophilic granular cytoplasm and round central nuclei

A secretory unit producing viscous mucin-rich secretions; tall cells with pale foamy cytoplasm and flattened basal nuclei

A crescent-shaped cap of serous cells on a mucous acinus in mixed glands (Giannuzzi's demilune); seen in submandibular gland

The pale-staining centre of a secondary lymphoid follicle where B cells undergo proliferation, somatic hypermutation, and affinity maturation

Concentrically arranged keratinised epithelial cells in the thymic medulla; a diagnostic feature of the thymus; involved in T-regulatory cell development

Periarteriolar lymphoid sheath; a sleeve of T lymphocytes surrounding the central arteriole in the splenic white pulp

Specialised postcapillary venule in the paracortex of lymph nodes with cuboidal endothelium allowing lymphocyte extravasation from blood into lymphoid tissue

The resorption pit created on the bone surface by an active osteoclast

The most common tumour of the parotid gland; contains both epithelial and mesenchymal (myxoid) components; also called mixed tumour

Decreased bone density due to trabecular bone loss exceeding formation; increased fracture risk at vertebrae, femoral neck, and distal radius