Tissue Level of Structural Organization

Vocabulary flashcards covering histology, epithelial tissues, connective tissues, cell junctions, exocrine/endocrine glands, muscular and nervous tissues, and body membranes based on lecture slides.

Histology

The science that deals with the study of tissues.

Pathologist

A physician who specializes in laboratory studies of cells and tissues to help other physicians make accurate diagnoses by examining tissues for disease changes.

Epithelial Tissue

Tissue that covers body surfaces, lines body cavities, hollow organs, and ducts, and forms glands.

Connective Tissue

Tissue that protects and supports the body and its organs, binds organs together, stores energy reserves as fat, and helps provide immunity to disease-causing organisms.

Muscular Tissue

Tissue that contracts to make body parts move and generates heat.

Nervous Tissue

Tissue that carries information from one part of the body to another through electrical signals called nerve impulses.

Cell Junctions

Contact points between the plasma membranes of tissue cells.

Tight Junctions

Cell junctions consisting of web-like strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes, acting as a diffusion barrier to prevent fluid leakage.

Adherens Junctions

Cell junctions containing plaque and cadherins attached to microfilaments of the cytoskeleton that help epithelial surfaces resist sheer and abrasive forces.

Adhesion Belts

Extensive zones formed by adherens junctions in epithelial cells that encircle the cell like a belt.

Desmosomes

Cell junctions containing plaque and cadherins attached to intermediate filaments (keratin) that provide high tensile strength, preventing cells from separating under tension.

Hemidesmosomes

Cell junctions resembling half a desmosome that contain transmembrane glycoproteins called integrins to anchor cells to the basement membrane.

Gap Junctions

Cell junctions formed by transmembrane proteins called connexins that create fluid-filled tunnels (connexons) for direct cell-to-cell communication and rapid impulse propagation.

Apical Surface

The free surface of an epithelial cell that faces body cavities, lumens, or exterior surfaces, which may contain cilia or microvilli.

Basal Surface

The deepest surface of an epithelial cell that adheres to extracellular materials such as the basement membrane.

Microvilli

Non-motile cytoplasmic projections with cores of actin filaments that increase apical surface area for absorption.

Stereocilia

Long, specialized microvilli found in absorptive epithelia (such as the epididymis and ductus deferens) that increase surface area and possess mechanosensory functions.

Cilia

Highly motile, hair-like projections with a microtubule core inserted into basal bodies that move wave-like to propel fluids and particles along epithelial surfaces.

Keratin

A tough protein in epithelial surface cells that hardens and cornifies them to protect underlying tissues and conserve water.

Simple Squamous Epithelium

A single layer of flat cells with centrally located nuclei that functions in filtration, diffusion, osmosis, and secretion in serous membranes.

Simple Cuboidal Epithelium

A single layer of cube-shaped cells with centrally located nuclei that functions in secretion and absorption.

Ciliated Simple Columnar Epithelium

A single layer of ciliated column-like cells with nuclei near the base, functioning in moving mucus and other substances by ciliary action.

Pseudostratified Columnar Epithelium

Epithelium in which all cells attach to the basement membrane but nuclei rest at different levels, giving a false multi-layered appearance.

Transitional Epithelium

Epithelium with variable surface cell appearance (ranging from flat when stretched to cuboidal when relaxed) that permits distension in organs like the urinary bladder.

Endocrine Glands

Ductless glands that secrete hormones directly into the interstitial fluid and bloodstream.

Exocrine Glands

Glands that secrete their products into ducts that empty onto epithelial surfaces or into hollow organ lumens.

Goblet Cells

Unicellular exocrine glands that secrete mucus directly onto the apical surface of lining epithelium.

Merocrine Glands

Glands whose secretions are packaged into vesicles by the Golgi complex and released via exocytosis without damaging the cell.

Apocrine Glands

Glands that accumulate secretory products at their apical surface, which then pinches off from the cell to release the secretion.

Holocrine Glands

Glands whose cells accumulate secretory products in their cytosol, mature, and completely rupture to release the product.

Fibroblast

Large, flat, abundant connective tissue cells with branching processes that secrete fibers and ground substance components.

Adipocyte

Connective tissue cells specialized for storing triglycerides as a single large droplet.

Mast Cell

Tissue-bound basophil located alongside blood vessels that produces histamine to dilate small vessels during inflammation.

Macrophage

Phagocytic connective tissue cells derived from monocytes that engulf bacteria and cellular debris.

Plasma Cell

Connective tissue cells derived from B lymphocytes that secrete antibodies to neutralize foreign substances.

Ground Substance

The fluid, semifluid, gelatinous, or calcified matrix component between connective tissue cells and fibers that supports, binds, and stores water.

Hyaluronic Acid

A viscous, slippery polysaccharide ground substance component that binds cells together, lubricates joints, and maintains eyeball shape.

Fibronectin

The primary adhesion protein in connective tissue that links collagen fibers and ground substance together.

Collagen Fibers

Extracellular matrix fibers that are strong and resistant to tensile pulling forces while remaining flexible.

Elastic Fibers

Branching connective tissue fibers composed of elastin and fibrillin that provide strength and elasticity.

Reticular Fibers

Fine collagen bundles coated with glycoprotein that form stroma networks around blood vessels and tissue cells.

Mesenchyme

An embryonic connective tissue consisting of irregular mesenchymal cells, semifluid ground substance, and reticular fibers that gives rise to all other connective tissues.

Mucous Connective Tissue

Embryonic connective tissue (Wharton's Jelly) found in the umbilical cord containing scattered fibroblasts in a viscous jellylike ground substance with collagen fibers.

Areolar Connective Tissue

A widely distributed loose connective tissue containing collagen, elastic, and reticular fibers with multiple cell types in a semifluid ground substance.

Dense Regular Connective Tissue

Connective tissue composed mainly of regularly arranged parallel collagen bundles with rows of fibroblasts, forming tendons and ligaments.

Dense Irregular Connective Tissue

Connective tissue consisting of randomly arranged collagen fibers and few fibroblasts that provides strength against multidirectional pulling forces.

Chondrocytes

Mature cartilage cells located within spaces called lacunae in the extracellular matrix.

Perichondrium

A layer of dense irregular connective tissue surrounding cartilage that contains blood vessels, nerves, and cartilage precursor cells.

Hyaline Cartilage

The most abundant cartilage type, featuring a shiny bluish-white ground substance with fine collagen fibers and chondrocytes.

Fibrocartilage

Cartilage with chondrocytes scattered among thick bundles of collagen fibers that provides strong support and fusion.

Elastic Cartilage

Cartilage consisting of chondrocytes located within a network of elastic fibers that gives support while maintaining shape.

Compact Bone

Bone tissue composed of structural units called osteons (Haversian systems) that forms the solid external surface of bones.

Spongy Bone

Bone tissue consisting of thin columns called trabeculae with red bone marrow spaces between them.

Blood Plasma

The liquid extracellular matrix of blood, composed mostly of water with nutrients, proteins, wastes, gases, and ions.

Lamina Propria

The supporting areolar connective tissue layer of a mucous membrane.

Serous Membrane

An epithelial membrane lining closed body cavities and covering internal organs, composed of mesothelium over areolar tissue and secreting lubricating fluid.

Cutaneous Membrane

The skin, consisting of an epidermal layer of keratinized stratified squamous epithelium and a deeper dermis of connective tissue.

Synovial Membrane

A connective tissue membrane lining joint cavities composed of synoviocytes that produce lubricating synovial fluid.

Neuron

A nerve cell capable of converting stimuli into action potentials and conducting nerve impulses.

Neuroglia

Non-conducting supportive cells of the nervous system that assist, protect, and nourish neurons.