AP1 - Ch 4 - Histology Part 1

Vocabulary flashcards covering the basics of histology, the extracellular matrix, cell junctions, and epithelial tissue classification and functions.

Histology

The study of normal structures of tissues.

Tissue

A group of structurally and functionally related cells and their external matrix that together perform a common function.

Extracellular matrix (ECM)

The surrounding material of a tissue consisting of ground substance and protein fibers which provide strength and hold cells in place.

Ground substance

The nonliving material produced by tissue cells that contains water, nutrients, ions, and three families of macromolecules.

Glycosaminoglycans (GAGs)

Negatively charged, hydrophilic carbohydrate building blocks that attract cations such as $Na^+$ to the ground substance; includes chondroitin sulfate and hyaluronic acid.

Proteoglycans

Molecules composed of GAGs linked to a protein core ($90\%$ carbohydrate) that make the ECM firmer and more resistant to compression.

Cell-adhesion molecules (CAMs)

Different types of glycoproteins that adhere cell to cell and cells to surroundings to maintain normal tissue architecture.

Collagen fibers

Unbranched, cablelike protein fibers that make up $20-25\%$ of all body proteins and are highly resistant to tension and pressure.

Elastic fibers

Branching wavy fibers containing the protein elastin that allow a fiber to stretch up to $1.5\times$ its resting length and return to it.

Reticular fibers

Thin, branched short fibers made of the protein collagen that form a weblike structure to support cells in organs like the spleen and liver.

Scurvy

A disease caused by a vitamin C deficiency resulting in unhealthy collagen fibers, leading to weakness and gum ulceration.

Marfan Syndrome

A genetic disease caused by an abnormal gene on chromosome $15$ that affects elastic fibers, often resulting in long limbs and aortic dissection.

Tight junctions

Also called occluding junctions; these seal the space between adjacent cells to prevent substances from passing between them.

Desmosomes

Cell junctions composed of linking integral proteins attached to intermediate filaments, designed to help tissues resist mechanical stress.

Gap junctions

Small pores formed by protein channels that allow small substances and electrical signals to flow freely between adjacent cells.

Basal lamina

The component of the basement membrane synthesized by epithelial cells, consisting of collagen fibers and ground substance.

Reticular lamina

The component of the basement membrane synthesized by underlying connective tissue, consisting of reticular fibers and ground substance.

Simple epithelium

Epithelial tissue consisting of a single layer of cells where every cell is in direct contact with the basement membrane.

Stratified epithelium

Epithelial tissue consisting of two or more layers of cells, where only the basal layer is in contact with the basement membrane.

Pseudostratified epithelium

A type of simple epithelium that appears layered because nuclei are at different heights, but all cells are attached to the basement membrane.

Squamous cells

Epithelial cells that are flat, wide, and irregular in shape, possessing a flattened nucleus.

Cuboidal cells

Epithelial cells that are as tall as they are wide, possessing a spherical nucleus located in the center of the cell.

Columnar cells

Epithelial cells that are slender and taller than they are wide, with an oval nucleus typically oriented lengthwise in the basal region.

Transitional epithelium

A tissue found only in the urinary system comprised of cells that can change shape from dome-shaped to flattened when stretched.

Paracellular transportation

The process where substances leak through the narrow space between cells in an epithelial membrane.

Transcellular transportation

The process where a substance enters a cell via the plasma membrane, diffuses through the cytosol, and exits the opposite side.

Endocrine glands

Glands that lack ducts and secrete hormones directly into the interstitial fluid and blood to act as chemical messengers.

Exocrine glands

Glands connected to the epithelial surface by a duct through which they secrete products like sweat, saliva, or enzymes.

Goblet cells

The most common unicellular exocrine glands found in the digestive and respiratory tracts that secrete mucus.

Merocrine secretion

A mode of secretion where products are packaged into vesicles and released by exocytosis into ducts.

Holocrine secretion

A mode of secretion where cells accumulate product in the cytosol and only release it when the cell ruptures and dies.

Carcinoma

A term for cancer of epithelial origin, such as lung adenocarcinoma or basal cell carcinoma.