Study of Tissues and Histology

Vocabulary flashcards covering key terms related to tissue types, embryology, connective tissue components, epithelium, glands, membranes, muscle, nervous tissue, cellular junctions, and tissue growth/repair.

Tissue

A group of similar cells and their extracellular matrix that arise from the same embryonic region and work together to perform a specific structural or physiological role in an organ.

Epithelial tissue

A sheet of closely adhering cells that covers body surfaces, lines cavities, forms glands, and functions in protection, absorption, secretion, and filtration.

Connective tissue

Tissues with relatively abundant extracellular matrix that support, protect, and bind organs; includes bone, cartilage, blood, fat, and fibrous tissues.

Nervous tissue

Tissue specialized for communication via electrical and chemical signals, composed of neurons and glial cells.

Muscular tissue

Tissue specialized to contract and exert force; includes skeletal, cardiac, and smooth muscle.

Ectoderm

Outer germ layer that gives rise to the epidermis and nervous system.

Mesoderm

Middle germ layer that forms mesenchyme and gives rise to muscle, bone, cartilage, and connective tissues.

Endoderm

Inner germ layer that forms mucous membranes of the digestive and respiratory tracts and many glands.

Basement membrane

Layer between epithelium and underlying connective tissue that anchors epithelium, regulates exchange, and binds growth factors.

Ground substance

The gel-like extracellular matrix around cells in connective tissue, containing water, GAGs, proteoglycans, and adhesive glycoproteins.

Fibers

Protein components of the connective tissue matrix, including collagen (tough), reticular (thin), and elastic (stretchy) fibers.

Simple squamous epithelium

Single layer of flat cells; promotes diffusion and filtration; lines air sacs (alveoli) and blood vessels.

Simple cuboidal epithelium

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

Simple columnar epithelium

Single layer of tall, column-like cells; often with microvilli and goblet cells for absorption and secretion.

Pseudostratified columnar epithelium

Nuclei at different levels give a layered look, but every cell rests on the basement membrane; often ciliated with goblet cells.

Stratified squamous epithelium

Multiple cell layers with surface cells flattened; keratinized or nonkeratinized; provides strong protection.

Stratified cuboidal epithelium

Two or more cell layers of typically cube-shaped cells; lines some ducts and glands.

Stratified columnar epithelium

Rare multi-layer epithelium with columnar surface cells; seen in limited regions such as pharynx or male urethra.

Urothelium (transitional epithelium)

Stratified epithelium of the urinary tract; dome-shaped umbrella cells adapt to volume changes and protect underlying tissue.

Areolar tissue

Loose connective tissue with loosely organized fibers and abundant ground substance; surrounding vessels and organs.

Dense regular connective tissue

Tightly packed collagen fibers arranged in parallel; found in tendons and ligaments; low vascularity.

Dense irregular connective tissue

Densely packed collagen fibers arranged in random directions; provides resistance to stresses in multiple directions (e.g., dermis).

Reticular tissue

connective tissue with a network of reticular fibers forming a supportive framework for organs like lymph nodes and spleen.

Adipose tissue (white)

Fat tissue dominated by white adipocytes with a single large lipid droplet; stores energy and cushions organs.

Adipose tissue (brown)

Fat tissue rich in mitochondria and capillaries; stores lipid in multiple small droplets and generates heat (thermogenesis).

Hyaline cartilage

Glassy cartilage with fine collagen fibers; provides smooth support and is enclosed by pericondrium.

Elastic cartilage

Cartilage rich in elastic fibers; flexible structure found in the ear and epiglottis.

Fibrocartilage

Cartilage with thick collagen fibers; resists compression and is found in intervertebral discs and joint areas.

Bone (osseous tissue)

Calcified connective tissue with osteocytes in lacunae, concentric lamellae around a central canal, and periosteum; provides support and protection.

Blood

Fluid connective tissue with plasma as the matrix and formed elements (erythrocytes, leukocytes, platelets) circulating in vessels.

Neuron

Nerve cell with a cell body, dendrites, and a long axon; primary signaling unit of the nervous system.

Glial cells

Supportive cells in the nervous system that protect and assist neurons; do not conduct nerve impulses.

Skeletal muscle

Striated, voluntary muscle composed of long multinucleate fibers that attach to bones.

Cardiac muscle

Striated, involuntary muscle of the heart; cardiomyocytes with intercalated discs that synchronize contraction.

Smooth muscle

Non-striated, involuntary muscle found in walls of organs and vessels; spindle-shaped cells with a single nucleus.

Tight junction

Cell junction encircling the apical region of epithelial cells; seals intercellular space to prevent passage between cells.

Desmosome

Anchoring junction that binds cells together to resist mechanical stress; connects cytoskeletons via protein plaques.

Hemidesmosome

Half desmosome that anchors an epithelial cell to the basement membrane.

Gap junction

Intercellular channel formed by connexons allowing direct cytoplasmic exchange of ions and small solutes between cells.

Endocrine gland

Gland that secretes hormones directly into the bloodstream; lacks ducts.

Exocrine gland

Gland that releases secretion onto an epithelial surface via ducts; includes serous, mucous, or mixed secretions.