Chapter 5: The Tissue Level of Organization

Flashcards covering key terms related to the tissue level of organization, including types of tissues, their characteristics, classifications, and specific examples, based on the provided lecture notes. This set focuses on vocabulary necessary for understanding histology and tissue function.

Tissue

A group of similar cells organized for a specific function.

Histology

The scientific field that studies tissues.

Epithelial tissues

Tissues that cover external and internal surfaces of the body and form secretory glands.

Connective tissues

Tissues that protect and support other tissues and various organs.

Muscle tissues

Tissues that create forces for movement and generate body heat.

Nervous tissues

Tissues that collect and analyze information about the body and signal muscles and glands.

Epithelial tissue (definition)

Consists of cells arranged in continuous sheets, in either single or multiple layers, with the upper surface usually exposed to the environment or an internal space.

Apical (free) surface

The surface of epithelial cells that faces the body surface, body cavity, lumen, or duct.

Lateral surfaces (epithelial cells)

The surfaces of epithelial cells that face adjacent cells.

Basal surface (epithelial cells)

The surface of epithelial cells opposite the apical layer, which adheres to extracellular materials or the basement membrane.

Basement membrane

A layer between an epithelium and the underlying connective tissue that anchors the epithelium.

Avascular

Lacking its own blood supply, characteristic of epithelial tissues.

Simple epithelium

Epithelial tissue where cells are arranged in a single layer.

Pseudostratified epithelium

Epithelial tissue that looks multilayered, but all cells touch the basement membrane.

Stratified epithelium

Epithelial tissue where cells are arranged in multiple layers.

Squamous cells

Flat (scale-like) cells found in epithelial tissue.

Cuboidal cells

Cube-shaped cells found in epithelial tissue.

Columnar cells

Tall, narrow (rectangular) cells found in epithelial tissue.

Transitional cells

Cells in epithelial tissue that can change shape from squamous to cuboidal, depending on the state of stretch.

Simple Squamous Epithelium

A single layer of flat cells; permits rapid diffusion and filtration; found in heart linings, blood vessels, and air sacs of lungs.

Simple Cuboidal Epithelium

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

Simple Columnar Epithelium (Nonciliated)

A single layer of nonciliated rectangular cells with nuclei near the base; functions in absorption and secretion; found in the gastrointestinal tract.

Pseudostratified Columnar Epithelium

Looks multilayered with nuclei at varying levels but all cells contact the basement membrane; often ciliated with goblet cells; functions in mucus secretion and propulsion; found in the respiratory tract.

Exfoliation (or Desquamation)

The process by which the outermost layers of cells in stratified epithelia die and flake off.

Keratinized Stratified Squamous Epithelium

Multiple layers of cells that become flat and scaly toward the surface, producing keratin; resists abrasion and water loss; forms the epidermis of the skin.

Stratum Basale

The deepest layer of the epidermis, consisting of columnar cells, mostly keratinocytes.

Stratum Spinosum

The layer of the epidermis where keratin is made.

Stratum Granulosum

The layer of the epidermis where keratin is bundled and a lipid is secreted to create a waterproof barrier.

Stratum Lucidum

A clear layer found only in thick skin, appearing white due to eleidin protein.

Stratum Corneum

The most superficial layer of the epidermis, composed of dead, squamous keratinocytes.

Nonkeratinized Stratified Squamous Epithelium

Stratified squamous epithelium without a surface layer of dead cells or keratin production; resists abrasion and pathogen penetration; found in the tongue, esophagus, and vagina.

Transitional Epithelium

A multilayered epithelium whose surface cells change from round to flat when stretched; permits organ distention; found in the urinary bladder and ureters.

Endocrine glands

Glands that secrete hormones directly into the blood after passing through interstitial fluid; examples include the thyroid and adrenal glands.

Exocrine glands

Glands that secrete materials into ducts or directly onto an apical surface; examples include sweat, oil, and salivary glands.

Stratified Cuboidal Epithelium

Consists of two or more layers of square or round cells; secretes sweat and produces ovarian hormones; found in sweat gland ducts and ovarian follicles.

Extracellular Matrix (ECM)

The material located between cells in connective tissue, consisting of protein fibers and ground substance.

Fibroblasts

Connective tissue cells that secrete fibers (collagen, elastic, reticular) and components of the ground substance.

Adipocytes (fat cells)

Connective tissue cells specialized to store triglycerides (fat).

Mast cells

Connective tissue cells that produce histamine, which dilates blood vessels to increase blood flow during an immune response.

Macrophages

Connective tissue phagocytic cells that engulf bacteria and cellular debris.

Plasma cells

Connective tissue cells that secrete antibodies as part of an immune response.

Ground substance

The fluid, semifluid, gelatinous, or calcified material between cells and fibers in the ECM, which supports cells, stores water, and allows exchange.

Loose connective tissue

A type of mature connective tissue characterized by many cells and loosely arranged fibers.

Dense connective tissue

A type of mature connective tissue characterized by fewer cells and many more fibers.

Cartilage

A type of connective tissue with a dense network of fibers in ground substance; its cells (chondrocytes) are in lacunae, and it is avascular.

Osseous tissue (bone)

A type of connective tissue whose ECM contains numerous collagen fibers enmeshed in calcium phosphate crystals, with bone cells confined to lacunae.

Liquid connective tissue

A type of connective tissue where cells are suspended in a fluid extracellular matrix, such as blood and lymph.

Areolar Connective Tissue

A loose connective tissue with loosely organized collagen, elastic, and reticular fibers and various cell types; provides strength, elasticity, and support; found beneath epithelia.

Adipose Tissue

A loose connective tissue dominated by adipocytes that store triglycerides; functions in energy storage, thermal insulation, and organ cushioning.

White fat

The primary type of fat found in most adults, serving as an energy reservoir and insulator.

Brown fat

A heat-generating adipose tissue found in fetuses, infants, and children.

Reticular Connective Tissue

A loose connective tissue composed of a mesh of reticular fibers and fibroblasts; forms the supportive stroma for lymphatic organs like lymph nodes and spleen.

Dense Regular Connective Tissue

A dense connective tissue with densely packed, parallel collagen fibers and fibroblasts in rows; provides strong attachment; found in tendons and most ligaments.

Dense Irregular Connective Tissue

A dense connective tissue with densely packed, randomly arranged collagen fibers and few fibroblasts; withstands unpredictable stresses; found in the dermis of the skin and organ capsules.

Elastic Connective Tissue

A dense connective tissue predominantly consisting of freely branching elastic fibers; allows stretching of various organs; found in lung tissue, trachea, and arterial walls.

Hyaline Cartilage

The most abundant type of cartilage, with a bluish-white, shiny ground substance and fine collagen fibers; provides smooth surfaces for joints, flexibility, and support; found at bone ends and in the trachea.

Fibrocartilage

Cartilage containing large, coarse bundles of collagen fibers; resists compression and absorbs shock; never has a perichondrium; found in pubic symphysis and intervertebral discs.

Elastic Cartilage

Cartilage containing elastic fibers, providing flexible, elastic support; covered with perichondrium; found in the external ear and epiglottis.

Marfan Syndrome

A genetic defect in fibrillin production, a protein crucial for strength in elastic connective tissue, leading to skeletal, cardiovascular, and visual abnormalities.