Histopathology BMS4470A - Cytoplasm: Cytoskeleton and Inclusions

Flashcards covering the components of the cytoplasmic cytoskeleton and various types of cellular inclusions as described in the Histopathology BMS4470A lecture.

Cytoskeleton

A complex array of microtubules, microfilaments (actin filaments), and intermediate filaments that determine cell shape and play roles in contraction, transport, and movement.

Microtubules

Semi-rigid tubular structures $25\,nm$ in diameter with walls composed of polymerized tubulin; they act as tracks for transport by motor proteins and maintain cell shape.

Tubulin

The subunit of microtubules, consisting of heterodimers of $\alpha\beta$-tubulin ($54\,kDa$ proteins).

Kinesin and Dynein

Motor proteins that use microtubules as tracks for the transport of vesicles.

Microfilaments

Short, flexible, dynamic filaments of actin subunits ($5-7\,nm$ in diameter) that regulate cytoplasmic viscosity and movement.

G-actin

Globular monomeric subunits ($42\,kDa$) that assemble into two intertwined filaments of F-actin to form microfilaments.

Myosins

Motor proteins that bind and move along actin filaments, carrying vesicles or producing cytoplasmic movement important for endocytosis and cell cleavage.

Intermediate Filaments

The most stable cytoskeletal component ($8-10\,nm$ diameter) composed of various protein subunits, conferring strong mechanical stability to cells.

Vimentin, nuclear lamins, and keratins

Examples of various protein subunits that compose intermediate filaments in different cell types.

Mitotic spindle inhibitors

Cancer chemotherapy drugs such as vinblastine, vincristine, and paclitaxel that block microtubule activity in rapidly growing neoplastic cells.

Glial fibrillary acidic protein (GFAP)

An intermediate filament protein used in immunocytochemistry to identify astrocytomas, the most common type of brain tumor.

Inclusions

Cytoplasmic structures that are not metabolically active and serve primarily as storage sites for accumulated metabolites; most are transitory and not membrane-enclosed.

Lipid droplets

Accumulations of lipid that fill adipocytes (fat cells) and are present in various other cell types.

Glycogen granules

Aggregates of carbohydrate polymer visible as irregular clumps of Periodic Acid–Schiff (PAS), notably in liver cells.

Melanin

Dark brown pigment granules in the skin that serve to protect cells from ultraviolet radiation.

Lipofuscin

Pale brown granules found in stable nondividing cells, such as neurons and cardiac muscle; also known as residual bodies.

Hemosiderin

A dense brown aggregate of denatured ferritin proteins representing an iron-containing inclusion.

Hemosiderosis

A condition characterized by the occurrence of hemosiderin in cells of organs throughout the body, often due to increased dietary iron or excessive lysis of red blood cells.

Hemochromatosis

A disorder resulting from extreme accumulations of iron in cellular hemosiderin which leads to damage in tissues of the liver and other organs.