Chapter 4: The Tissue Level of Organization – Vocabulary Flashcards

Key vocabulary terms and definitions from the Tissue Level of Organization chapter notes.

Tissue

A group of cells with a common embryonic origin that function together to perform a specialized activity; there are four basic tissue types.

Epithelial Tissue

Tissue that covers body surfaces and lines cavities; avascular; attached to a basement membrane; abundant cell junctions and high regenerative ability.

Connective Tissue

Tissues with cells and an extracellular matrix; highly vascularized; provides support, binds, and protects other tissues; highly variable in structure.

Muscular Tissue

Tissues composed of fibers that contract to produce motion, maintain posture, and generate heat; includes skeletal, cardiac, and smooth muscle.

Nervous Tissue

Tissue that conducts electrical impulses; made of neurons and neuroglia; analyzes and transmits information.

Basement Membrane

Thin layer that anchors epithelium to underlying connective tissue, composed of basal lamina and reticular lamina.

Apical Surface

The free, uppermost surface of an epithelial cell exposed to the lumen or outside environment.

Basal Surface

The bottom surface of an epithelial cell that rests on the basement membrane.

Lateral Surface

The sides of epithelial cells that contact neighboring cells.

Cell Junction

Points of contact between adjacent cells that hold them together and enable communication.

Tight Junction

A seal formed by strands of transmembrane proteins that prevents passage of substances between cells.

Adherens Junction

Junctions that connect cells via cadherin proteins linked to actin filaments, forming an adhesion belt.

Desmosome

Strong junction that connects cells via cadherins to intermediate filaments, providing mechanical strength.

Gap Junction

Channels formed by connexons allowing small molecules and ions to pass between neighboring cells.

Hemidesmosome

junction that attaches epithelial cells to the basement membrane via integrins and intermediate filaments.

Cadherin

Transmembrane glycoproteins that mediate cell–cell adhesion in adherens junctions and desmosomes.

Glandular Epithelium

Epithelium specialized for secretion; forms endocrine and exocrine glands; can be unicellular or multicellular.

Endocrine Glands

Glands whose secretions (hormones) enter interstitial fluid and diffuse into the bloodstream without ducts.

Exocrine Glands

Glands that secrete products into ducts that surface onto skin or into body lumen.

Merocrine Secretion

Secretory mode where vesicles release product by exocytosis without cell loss.

Apocrine Secretion

Secretory mode where a portion of the cell buds off and releases product; part of the cell is lost.

Holocrine Secretion

Secretory mode where whole cells rupture to release their product; new cells replace them.

Unicellular Glands

Glands consisting of a single cell, such as goblet cells, that secrete mucus.

Multicellular Exocrine Glands

Glands composed of many cells with a duct and a secretory portion; include tubular and acinar forms.

Ground Substance

Fills the space between cells and fibers in connective tissue; a gel-like material rich in water and glycosaminoglycans.

Extracellular Matrix

Material located between cells in connective tissue, composed of fibers and ground substance; provides structural support.

Collagen

A strong, flexible protein fiber; most abundant protein in the body.

Elastic Fibers

Fibers that provide stretch and recoil, made of elastin.

Reticular Fibers

Fine fibers of collagen that form supportive networks around cells and organs.

Fibroblast

A common connective tissue cell that synthesizes fibers and ground substance.

Chondrocyte

Cartilage cell located in a lacuna within cartilage.

Osteocyte

Bone cell located in a lacuna; maintains bone tissue.

Hyaline Cartilage

Most common cartilage; glassy matrix with chondrocytes in lacunae; provides smooth surfaces for joints.

Fibrocartilage

Cartilage rich in thick collagen fibers; very strong; lacks perichondrium in places.

Elastic Cartilage

Cartilage with elastic fibers; maintains shape and flexibility; perichondrium present.

Bone Tissue

Compact bone with osteons and lamellae; spongy bone with trabeculae and marrow; provides support and protection.

Blood

Liquid connective tissue with plasma and formed elements; transports gases, nutrients, and wastes; participates in immunity and clotting.

Mucous Membrane

Epithelium plus underlying lamina propria that lines cavities open to the outside and secretes mucus.

Serous Membrane

Membrane lining closed body cavities and covering organs; produces serous fluid to reduce friction.

Cutaneous Membrane

Skin; epidermis and dermis; keratinized epithelium providing protection.