Animal Tissues: Structure, Function, and Repair

Comprehensive vocabulary flashcards covering animal tissue types, epithelial classifications, glandular secretions, connective tissue variants, muscle types, nervous tissue histology, and tissue repair processes.

Differentiation

The developmental process by which unspecialized cells acquire distinct structural and functional specializations through differential gene expression.

Stem cells

Unspecialized cells capable of self-renewal and cell replacement by dividing to produce new cells that differentiate into specialized tissue cells.

Tissue

A group of cells with a common embryonic origin that share structural features and work together in an organized pattern to perform specific functions.

Histology

The microscopic study of tissue appearance, organization, and function.

Epithelial tissue

One of the four primary animal tissue types; composed of closely packed cells that cover exterior surfaces, line internal cavities and passageways, and form glands.

Connective tissue

A primary animal tissue type consisting of cells dispersed within an extracellular matrix that functions to support, bind, protect, and transport.

Muscle tissue

An excitable and contractile primary tissue type containing contractile proteins that shortens to generate pulling forces and produce movement.

Nervous tissue

An excitable primary tissue type composed of neurons and glial cells that detects stimuli and transmits electrochemical signals throughout the body.

Apical surface

The exposed, uppermost surface of epithelial tissue that borders an internal lumen, space, or the body exterior.

Basal surface

The bottom surface of an epithelium that attaches to the underlying basement membrane.

Basement membrane

An extracellular structure that adheres epithelial cells to underlying connective tissue and anchors the basal surface.

Simple epithelium

An epithelial tissue arrangement consisting of a single layer of cells, where every cell rests on the basement membrane.

Stratified epithelium

An epithelial tissue organization consisting of two or more stacked cell layers designed primarily for protection against chemical or physical wear.

Simple squamous epithelium

A single layer of thin, flat cells that provides a minimal barrier to allow rapid diffusion and filtration in lung alveoli and capillaries.

Simple cuboidal epithelium

A single layer of cube-shaped cells specialized for absorption and secretion, commonly found lining kidney tubules and small gland ducts.

Simple columnar epithelium

A single layer of tall, column-like cells active in nutrient absorption and mucus secretion, lining the digestive tract and uterine tubes.

Pseudostratified columnar epithelium

A single-layered epithelium whose cell nuclei appear at varying levels, giving a false stratified appearance; its ciliated form lines much of the respiratory tract.

Stratified squamous epithelium

A multi-layered tissue whose surface cells are flattened; provides protection against abrasion in areas such as the mouth and esophagus.

Stratified cuboidal epithelium

A protective epithelial tissue made of multiple layers of cube-shaped cells, found lining the ducts of sweat and salivary glands.

Stratified columnar epithelium

An epithelium with multiple cell layers having tall surface cells, providing secretion and protection in parts of the urethra and certain gland ducts.

Transitional epithelium

A specialized stratified epithelium whose cell shapes stretch and change form as organs distend, found lining the urinary bladder and ureters.

Cilia

Motile apical projections on epithelial cells that move fluids, mucus, and trapped particles along tissue surfaces in uterine tubes and respiratory passages.

Goblet cells

Unicellular mucus-secreting exocrine gland cells scattered among columnar epithelial cells in mucous membranes such as the small-intestinal lining.

Endocrine glands

Ductless glands that secrete hormones directly into the interstitial fluid to diffuse into the bloodstream and target distant receptor-bearing cells.

Exocrine glands

Glands that release their secretory products through ducts onto an epithelial surface or into an organ lumen.

Merocrine secretion

A secretory mode where glandular products are packaged into vesicles and released across the cell membrane by exocytosis without damaging the cell.

Apocrine secretion

A secretory mode where the apical portion of the cell pinches off containing the secretory product, after which the remaining cell survives and repairs itself.

Holocrine secretion

A secretory mechanism in which the entire mature gland cell ruptures, dies, and becomes incorporated directly into the secretory product.

Sebaceous glands

Holocrine glands that release an oily secretion into hair follicles to lubricate and protect skin and hair.

Extracellular matrix

The non-cellular material surrounding connective tissue cells, consisting of protein fibers embedded in ground substance.

Collagen fibers

Thick protein fibers with high tensile strength that resist pulling and tension in tendons and ligaments.

Fibroblasts

The most abundant fixed cells in connective tissue proper that synthesize and secrete protein fibers and ground substance.

Areolar tissue

A loose connective tissue forming a mesh of varied cells and fibers that fills spaces, cushions vessels, and underlies most epithelia.

Adipose tissue

A loose connective tissue dominated by adipocytes with minimal extracellular matrix, specialized for fat storage, thermal insulation, and protection.

White adipose tissue

The most abundant form of fat tissue in adults that stores lipids, provides thermal insulation, and cushions organs such as the kidneys and eyes.

Brown adipose tissue

A highly vascularized, mitochondria-rich fat tissue common in infants and small adult depots that metabolizes lipids to generate heat.

Reticular tissue

A loose connective tissue composed of a network of reticular fibers that forms a supportive architectural stroma in soft organs such as the spleen and liver.

Dense regular connective tissue

Connective tissue packed with parallel bundles of collagen fibers that resist tensile forces along their axis, found in tendons and ligaments.

Dense irregular connective tissue

A connective tissue featuring an interwoven mesh of collagen fibers running in various directions to resist stretching from multiple angles, as in the dermis.

Chondrocytes

Mature cartilage cells that reside embedded within matrix cavities called lacunae.

Lacunae

Small fluid-filled matrix spaces or cavities that house chondrocytes in cartilage or osteocytes in bone.

Hyaline cartilage

The most common cartilage type; smooth, strong, and flexible, covering movable joint surfaces and forming the embryonic skeleton template.

Fibrocartilage

A tough supportive cartilage containing thick bundles of collagen fibers designed to withstand compression and absorb shock in knee menisci and intervertebral discs.

Elastic cartilage

A supportive cartilage containing abundant elastic fibers that provides firm yet elastic support in structures such as the external ear.

Osteocytes

Mature bone cells situated within lacunae that help maintain the mineralized extracellular matrix.

Hydroxyapatite

A hard calcium phosphate mineral integrated into the collagenous matrix of bone that provides rigidity and structural compressive strength.

Erythrocytes

Red blood cells specialized in transporting oxygen and some carbon dioxide through the bloodstream.

Lymph

A fluid connective tissue consisting of a liquid matrix and white blood cells, collected by lymphatic capillaries from interstitial spaces and returned to venous blood.

Skeletal muscle

Voluntary, striated muscle tissue consisting of long, cylindrical, multinucleated fibers with nuclei located at the cell periphery, attached to bones.

Cardiac muscle

Involuntary, striated muscle tissue comprising short, branched cells with a single central nucleus and intercalated discs, restricted to the heart wall.

Intercalated discs

Specialized junctional complexes between adjacent cardiac myocytes containing anchoring junctions and gap junctions that synchronize involuntary contractions.

Smooth muscle

Involuntary, non-striated muscle tissue composed of spindle-shaped cells with a single nucleus, lining internal hollow organs and blood vessel walls.

Neurons

Excitable nervous tissue cells that process and transmit information via electrochemical action potentials and neurotransmitters.

Neuroglia

Non-excitable, supportive cells of nervous tissue that protect, nourish, insulate, and regulate the environment around neurons.

Astrocytes

Glial cells in the central nervous system that regulate local ion concentrations, recycle neurotransmitters, and contribute to the blood-brain barrier.

Microglia

Phagocytic glial cells that provide immune protection by scavenging cellular debris and pathogens in the central nervous system.

Oligodendrocytes

Glial cells that produce the insulating myelin sheath around axons within the central nervous system (brain and spinal cord).

Schwann cells

Glial cells that produce the insulating myelin sheath surrounding neuronal axons in the peripheral nervous system.

Necrosis

Accidental, unprogrammed cell death caused by external damage or trauma that induces an inflammatory response.

Apoptosis

Programmed, orderly cell death that eliminates unneeded cells without releasing cellular contents or triggering inflammation.

Edema

Tissue swelling resulting from the abnormal accumulation of interstitial fluid that escapes widened, permeable capillaries during inflammation.

Granulation tissue

Vascular connective tissue formed by proliferating fibroblasts and new capillaries during the rebuilding phase of wound healing.

Primary union

The healing process that occurs in wounds where the severed edges are close together, enabling direct re-epithelialization with minimal scarring.

Secondary union

The healing process required for gaping wounds, where granulation tissue fills a wider defect and wound contraction draws margins together.

Hypertrophy

An increase in tissue mass and muscle fiber diameter resulting from the addition of structural and contractile proteins in response to physical demand.

Atrophy

A reduction in muscle fiber size and tissue mass caused by the degradation of structural proteins due to disuse, lack of stimulation, or aging.