Tissue: The Living Fabric (Chapter 04)

Key vocabulary terms and definitions covering epithelia, connective tissue, membranes, muscle, nervous tissue, repair, and developmental concepts from the tissue chapter.

Tissue

Groups of cells similar in structure that perform common or related functions; the living fabric of the body.

Histology

The study of tissues.

Four basic tissue types

Epithelial, connective, muscle, and nervous tissue.

Epithelial tissue (epithelium)

A sheet of cells that covers a body surface or lines a body cavity; also forms glands.

Glandular epithelium

Epithelium that forms glands and secretes substances.

Polarity (epithelial)

Cells have an apical (top) and basal (bottom) surface with different structures and functions.

Apical surface

Exposed, free surface of an epithelium, often with microvilli.

Basal surface

Surface that faces inward toward the body and attaches to the basal lamina.

Basal lamina

Adhesive sheet that anchors epithelial cells to underlying tissues.

Basement membrane

Layer formed by the basal lamina plus reticular lamina; reinforces the epithelial sheet.

Avascular but innervated

Epithelia lack blood vessels but receive nerve supply.

Regeneration (epithelial)

High regenerative capacity to replace lost or damaged cells.

Simple epithelium

One cell layer thick.

Stratified epithelium

Two or more cell layers thick; provides protection.

Squamous

Flat, scale-like epithelial cells.

Cuboidal

Cube-shaped epithelial cells.

Columnar

Tall, column-like epithelial cells.

Simple squamous epithelium

Single layer of flattened cells; rapid diffusion or filtration; examples: kidney glomeruli, air sacs of lungs; endothelium and mesothelium are specialized types.

Endothelium

Simple squamous lining of blood vessels, lymphatic vessels, and the heart.

Mesothelium

Simple squamous epithelium lining serous membranes of ventral body cavities.

Simple cuboidal epithelium

Single layer of cube-shaped cells; secretion and absorption; kidney tubules and glands.

Simple columnar epithelium

Single layer of tall cells; absorption and secretion; often has microvilli and goblet cells.

Goblet cell

Unicellular mucus-secreting cell in epithelia.

Cilia

Hairlike projections that move substances (e.g., mucus) across epithelia.

Pseudostratified columnar epithelium

Single layer of cells of differing heights; often ciliated with goblet cells; nuclei at different levels.

Stratified squamous epithelium

Several cell layers; protection; keratinized (skin) or nonkeratinized (moist linings like mouth, esophagus, vagina).

Transitional epithelium

Stratified epithelium that stretches; lines urinary bladder, ureters, part of urethra.

Gland

One or more cells that secrete a fluid (secretion).

Endocrine gland

Glandular tissue that secrete hormones into interstitial fluid and blood (ductless).

Exocrine gland

Gland that secretes onto surfaces or into body cavities through ducts.

Unicellular exocrine glands

Goblet cells and mucous cells; produce mucin that forms mucus.

Multicellular exocrine glands

Glands with a duct and a secretory unit; tubular, alveolar, or tubuloalveolar; can be simple or compound.

Merocrine secretion

Secretion by exocytosis; no cell damage (most sweat, pancreas, salivary).

Holocrine secretion

Secretions released when the gland cells rupture (sebaceous glands).

Apocrine secretion

Product accumulates at the apex and the apex is released; cell repairs and repeats (controversial in humans).

Connective tissue

Most abundant and widespread primary tissue; supports, binds, protects; four classes: proper, cartilage, bone, blood.

Extracellular matrix (ECM)

Nonliving material between cells made of ground substance and fibers that supports cells.

Ground substance

Unstructured gel-like material between cells; contains interstitial fluid and proteoglycans.

Fibers (connective tissue)

Collagen (tibile strength), elastic (stretch/recoil), reticular (support networks).

Connective tissue cells

-blast cells produce matrix; -cyte cells maintain matrix; examples: fibroblasts, chondroblasts, osteoblasts, hematopoietic stem cells.

Areolar connective tissue

Widely distributed loose CT; packing material; supports and binds; contains a mix of fibers and ground substance.

Adipose tissue

Loose CT with adipocytes; white fat stores energy; brown fat generates heat.

Reticular connective tissue

Loose CT with reticular fibers forming a mesh that supports lymphoid organs.

Dense regular connective tissue

Dense CT with parallel collagen fibers; resistance to tension; examples: tendons and ligaments.

Dense irregular connective tissue

Dense CT with irregular collagen; resists tension from many directions; in dermis and joint capsules.

Elastic connective tissue

Dense CT with elastic fibers; found in ligaments of the vertebral column and arterial walls.

Cartilage

Rigid, avascular connective tissue; matrix secreted by chondroblasts and chondrocytes; perichondrium supplies nutrients.

Hyaline cartilage

Most common cartilage; glossy; found at ends of long bones, nose, trachea; most abundant type.

Elastic cartilage

Cartilage with more elastic fibers; found in external ear and epiglottis.

Fibrocartilage

Strong cartilage with thick collagen fibers; located in intervertebral discs and knee menisci.

Bone tissue (osseous tissue)

Rigid calcium-rich connective tissue; osteoblasts/osteocytes; osteons; supports and protects; stores minerals.

Blood

Fluid connective tissue with plasma; formed elements (RBCs, WBCs, platelets); transports nutrients and wastes.

Nervous tissue

Tissue of the nervous system; neurons transmit signals; glial cells support neurons.

Neuron

Nerve cell that conducts electrical impulses; has dendrites and a long axon.

Glial cells (neuroglia)

Supporting cells that protect, insulate, and support neurons.

Membranes

Coverings/linings composed of more than one tissue; include cutaneous, mucous, and serous membranes.

Cutaneous membrane

Skin; keratinized stratified squamous epithelium plus dense connective tissue; dry membrane.

Mucous membrane (mucosae)

Line cavities that open to the exterior; epithelium over lamina propria; often secretes mucus.

Serous membrane (serosae)

Moist membranes of closed ventral body cavities; mesothelium on areolar tissue; parietal and visceral layers; serous fluid.

Inflammation

Initial response of tissue to injury; dilates vessels and increases permeability.

Tissue repair

Process of healing after injury; regeneration (same tissue) or fibrosis (scar formation).

Regeneration (tissue repair)

Replacement by same tissue type, restoring function.

Fibrosis (tissue repair)

Replacement by dense connective tissue, forming scar; may impair function.

Scar tissue

Fibrous tissue that replaces damaged tissue; can alter organ function.

Tissue regenerative capacity

Different tissues regenerate at different rates; epithelial and bone regenerate well; cardiac and nervous tissues regenerate poorly.

Embryonic germ layers

Ectoderm, mesoderm, and endoderm; give rise to all four primary tissues.

Ectoderm

Outer germ layer; gives rise to nervous tissue and epidermis.

Mesoderm

Middle germ layer; gives rise to muscle, bone, connective tissue.

Endoderm

Inner germ layer; gives rise to mucosal epithelial linings of many organs.