Tissue: The Living Fabric

Comprehensive vocabulary flashcards covering the primary tissue types, classifications of epithelia and connective tissues, muscle and nervous tissues, body membranes, tissue repair mechanisms, and embryological origins.

Histology

The study of tissues.

Tissue

A group of cells similar in structure that work together to perform a common or related function.

Epithelial Tissue

A primary tissue type that forms boundaries between different environments, covering body surfaces, lining cavities, and forming glands; functions in protection, absorption, filtration, excretion, secretion, and sensory reception.

Connective Tissue

The most abundant and widely distributed primary tissue type; functions to support, protect, bind other tissues together, insulate, store reserve fuel, and transport substances.

Muscle Tissue

A primary tissue type composed of excitable, highly vascularized cells that contract to cause movement.

Nervous Tissue

A primary tissue type specialized for internal communication and control, consisting of neurons and supporting neuroglia.

Polarity (in Epithelial Tissue)

An epithelial characteristic defined by having an apical surface (upper free surface exposed to the exterior or a cavity) and a basal surface (lower attached surface resting on connective tissue).

Simple Epithelium

An epithelium composed of a single cell layer; primarily involved in absorption, secretion, and filtration.

Stratified Epithelium

An epithelium composed of two or more cell layers; primarily found in high-abrasion areas where protection is important.

Squamous Cells

Flattened and scale-like epithelial cells with disc-shaped central nuclei.

Cuboidal Cells

Boxlike epithelial cells, approximately as tall as they are wide, with large, spherical central nuclei.

Columnar Cells

Tall, column-shaped epithelial cells with oval or round nuclei, often located close to the basal surface.

Simple Squamous Epithelium

A single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; facilitates diffusion and filtration in kidney glomeruli, lung air sacs, and lining of blood vessels.

Endothelium

The slick, friction-reducing simple squamous epithelial lining found in lymphatic vessels, blood vessels, and the heart.

Mesothelium

The simple squamous epithelium found in serous membranes lining the ventral body cavity and covering its organs.

Simple Cuboidal Epithelium

A single layer of cubelike cells with large, spherical central nuclei; functions in secretion and absorption within kidney tubules, small gland ducts, and ovary surfaces.

Simple Columnar Epithelium

A single layer of tall cells with round to oval nuclei, frequently featuring microvilli or cilia; functions in absorption and secretion along the digestive tract and reproductive organs.

Pseudostratified Columnar Epithelium

A single layer of cells of differing heights whose nuclei appear at different levels, giving a false impression of stratification; frequently ciliated with goblet cells to propel mucus in the trachea and upper respiratory tract.

Stratified Squamous Epithelium

A thick, multilayered epithelial membrane with active basal cells and flattened surface cells; protects against abrasion in nonkeratinized form (esophagus, mouth, vagina) and keratinized form (epidermis).

Transitional Epithelium

A stratified epithelium characterized by dome-shaped apical cells that flatten and stretch readily to accommodate distension in urinary organs such as the bladder and ureters.

Gland

One or more specialized epithelial cells that produce and discharge an aqueous fluid secretion.

Exocrine Gland

A gland that secretes products into ducts that carry them onto external body surfaces or into internal cavities.

Endocrine Gland

A ductless gland that releases hormones directly into the extracellular space to enter blood or lymphatic fluid.

Goblet Cell

A unicellular exocrine gland found in epithelial linings that produces and secretes mucin, which dissolves in water to form mucus.

Ground Substance

The unstructured material filling the space between connective tissue cells and fibers, composed of interstitial fluid, cell adhesion proteins, and proteoglycans.

Collagen Fibers

Tough, strong, and abundant fibrous proteins in connective tissue matrix that provide high tensile strength.

Elastic Fibers

Long, thin fibers containing elastin protein that form branching networks allowing tissues to stretch and recoil.

Reticular Fibers

Short, fine, collagenous fibers that branch extensively to form delicate supporting networks (stroma) around blood vessels and soft organs.

Fibroblasts

Immature, mitotically active cells of connective tissue proper that secrete the fibers and ground substance of the extracellular matrix.

Chondroblasts

Active, matrix-secreting stem cells found in developing or growing cartilage.

Chondrocytes

Mature cartilage cells that reside within small matrix cavities called lacunae to maintain the extracellular matrix.

Osteoblasts

Active, bone-forming cells that secrete organic components of the bone matrix.

Osteocytes

Mature bone cells residing inside lacunae that maintain the calcified bone matrix.

Areolar Connective Tissue

A prototype loose connective tissue with a gel-like matrix containing all three fiber types, fibroblasts, macrophages, and mast cells; cushions organs and holds tissue fluid.

Adipose Tissue

A loose connective tissue dominated by closely packed adipocytes storing fat droplets; functions in fuel storage, insulation, and shock absorption.

Reticular Connective Tissue

A loose connective tissue consisting of a network of reticular fibers and cells that forms an internal supportive skeleton (stroma) in lymphoid organs such as the spleen and lymph nodes.

Dense Regular Connective Tissue

A connective tissue composed predominantly of parallel collagen fibers and fibroblasts; resists tensile stress in a single direction, forming tendons and ligaments.

Dense Irregular Connective Tissue

A connective tissue containing irregularly arranged collagen fibers; withstands tension exerted in multiple directions, forming joint capsules, organ capsules, and the dermis.

Elastic Connective Tissue

Dense regular connective tissue rich in elastic fibers; enables recoil after stretching in structures such as the aorta walls and large bronchial tubes.

Hyaline Cartilage

The most widespread cartilage type, characterized by a glassy, amorphous matrix with imperceptible collagen fibers; cushions and supports ribs, trachea, nose, and ends of long bones.

Elastic Cartilage

A flexible cartilage containing abundant elastic fibers in its matrix; maintains structure and flexibility in the external ear and epiglottis.

Fibrocartilage

A tough cartilage with thick rows of collagen fibers alternating with chondrocytes; provides high tensile strength and shock absorption in intervertebral discs and pubic symphysis.

Osseous Tissue

Hard, calcified connective tissue consisting of osteocytes in lacunae, osteons, inorganic calcium salts, and abundant collagen fibers; supports and protects the body.

Blood (Tissue)

A fluid connective tissue consisting of erythrocytes, leukocytes, and platelets suspended in an extracellular fluid matrix called plasma; transports nutrients, wastes, and gases.

Skeletal Muscle

Voluntary, striated muscle tissue composed of long, multinucleate cylindrical fibers attached to bones; causes body locomotion and manipulation.

Cardiac Muscle

Involuntary, striated muscle tissue consisting of branching, uninucleate cells joined by intercalated discs in the heart walls; propels blood into circulation.

Smooth Muscle

Involuntary, nonstriated muscle tissue made of spindle-shaped, uninucleate cells arranged in sheets; propels substances along internal passageways of hollow organs.

Neurons

Specialized, branching nervous cells that generate, receive, and conduct electrical impulses throughout the body.

Neuroglia

Nonexcitable supporting cells in nervous tissue that insulate, nourish, and protect neurons.

Cutaneous Membrane

The skin; an organ system membrane composed of keratinized stratified squamous epithelium (epidermis) attached to a thick layer of dense irregular connective tissue (dermis).

Mucous Membrane (Mucosa)

A wet membrane that lines body cavities open to the exterior (digestive, respiratory, urogenital tracts), consisting of an epithelium resting on a layer of loose connective tissue called lamina propria.

Serous Membrane (Serosa)

A double-layered, lubricated membrane lining closed ventral body cavities, composed of simple squamous epithelium (mesothelium) resting on a thin layer of areolar connective tissue.

Regeneration

A mechanism of tissue repair where destroyed tissue is replaced by proliferation of the same kind of cells, restoring original tissue function.

Fibrosis

A mechanism of tissue repair where destroyed tissue is replaced with dense fibrous connective tissue (scar tissue), causing a loss of original tissue function.

Granulation Tissue

Delicate, vascularized pink tissue formed during the organization phase of tissue repair, containing budding capillaries, proliferating fibroblasts, and macrophages.

Ectoderm

The primary embryonic germ layer that differentiates into nervous tissue and the epidermis of the skin.

Mesoderm

The primary embryonic germ layer that differentiates into all muscle tissues, connective tissues, and bone.

Endoderm

The innermost embryonic germ layer that differentiates into the mucosal linings of the digestive and respiratory tracts.