Chapter 4: The Tissue Level of Organization

Comprehensive vocabulary flashcards covering the primary tissue types, cell junctions, epithelial and connective tissue classifications, membranes, muscle, nervous tissue, injury responses, and histology concepts from Chapter 4 of Fundamentals of Anatomy & Physiology.

Tissues

Collections of specialized cells and cell products that perform specific functions.

Histology

The study of the structure of tissues.

Epithelial Tissue

One of the four basic tissue types; covers exposed surfaces, lines internal passageways and chambers, and forms glands.

Connective Tissue

One of the four basic tissue types; fills internal spaces, supports other tissues, transports materials, and stores energy.

Muscle Tissue

One of the four basic tissue types; specialized for contraction to produce movement.

Nervous Tissue

One of the four basic tissue types; specialized for carrying electrical signals and information from one part of the body to another.

Apical Surface

The exposed surface of an epithelium facing an internal space or exterior environment, which may feature microvilli or cilia.

Basolateral Surface

The region of an epithelial cell that includes the base where it attaches to the basement membrane and the sides where it contacts adjacent cells.

Avascularity

The characteristic of lacking blood vessels, requiring cells to obtain nutrients by absorption or diffusion across surfaces.

Cell Adhesion Molecules (CAMs)

Transmembrane proteins that bind opposing plasma membranes to one another or to the extracellular matrix.

Gap Junctions

Intercellular connections held together by interlocking transmembrane proteins called connexons that permit the passage of small molecules and ions between cells.

Tight Junctions

Junctions formed by the interlocking of membrane proteins that bind plasma membranes together, preventing the passage of water and solutes between cells.

Adhesion Belt

A band located inferior to a tight junction that ties an epithelial cell to the microfilaments of the terminal web.

Spot Desmosomes

Small, disc-shaped intercellular junctions linked by CAMs and proteoglycans that stabilize the shape of cells by tying adjacent cells together.

Hemidesmosomes

Intercellular junctions resembling half of a spot desmosome that anchor an epithelial cell to extracellular protein fibers in the basement membrane.

Basal Lamina

The superficial, amorphous layer of the basement membrane closest to the epithelium that functions as a selective filter.

Reticular Lamina

The deeper portion of the basement membrane composed of reticular fibers and ground substance that provides strength to the attachment.

Mesothelium

The simple squamous epithelium that lines ventral body cavities, including the pleural, pericardial, and peritoneal cavities.

Endothelium

The simple squamous epithelium that forms the inner lining of the heart and blood vessels.

Stratified Squamous Epithelium

A multi-layered epithelium located where severe mechanical stresses occur, providing protection against abrasion, pathogens, and chemical attack.

Transitional Epithelium

A stratified epithelium whose appearance changes from cuboidal to squamous as it stretches, permitting repeated cycles of stretching without damage in organs like the urinary bladder.

Pseudostratified Ciliated Columnar Epithelium

An epithelium that appears layered because cell nuclei are at various distances from the surface, though every cell contacts the basement membrane; typically possesses cilia to move mucus.

Endocrine Glands

Ductless glands that produce secretions called hormones and discharge them directly into the bloodstream.

Exocrine Glands

Glands that discharge their secretions directly onto epithelial surfaces through tubular or branched passageways called ducts.

Goblet Cells

Unicellular exocrine glands scattered among the epithelial cells of the intestines that secrete mucin to form mucus.

Merocrine Secretion

A mode of glandular secretion where product is released from secretory vesicles at the apical surface by exocytosis without cellular damage.

Apocrine Secretion

A mode of glandular secretion involving the loss of apical cytoplasm, containing secretory vesicles and components, after which the cell regenerates before releasing further secretion.

Holocrine Secretion

A mode of glandular secretion where the entire gland cell becomes packed with secretory products, bursts, and dies, requiring continuous replacement by dividing stem cells.

Serous Glands

Exocrine glands that produce watery secretions containing enzymes.

Mucous Glands

Exocrine glands that secrete mucins that hydrate in water to form a thick, protective mucus.

Matrix

The extracellular component of connective tissue consisting of extracellular protein fibers and fluid ground substance, which constitutes most of the tissue volume.

Ground Substance

A clear, colorless, and viscous fluid component of connective tissue matrix that fills spaces between cells and slows the movement of pathogens.

Fibroblasts

The most abundant fixed cells in connective tissue proper; responsible for secreting components of ground substance and protein fibers.

Fibrocytes

The second most abundant cell type in connective tissue proper; functions to maintain existing connective tissue fibers.

Mesenchymal Cells

Stem cells present in connective tissue that divide and differentiate into fibroblasts, macrophages, or other connective tissue cells in response to injury or infection.

Melanocytes

Connective tissue cells that synthesize and store the brown pigment melanin, contributing to skin and eye coloration.

Macrophages

Large phagocytic immune system cells that engulf damaged tissue cells and invading pathogens; exist as fixed or free migrating cells.

Mast Cells

Mobile immune cells of connective tissue proper that release histamine to stimulate inflammation and heparin to inhibit blood clotting.

Collagen Fibers

The most common fibers in connective tissue proper; long, straight, unbranched, strong, and flexible fibers that resist tensile forces.

Reticular Fibers

Thin, interwoven, branching protein fibers that form a strong supportive framework (stroma) resisting forces applied from many directions.

Elastic Fibers

Branched and wavy fibers composed of the protein elastin that recoil to their original length after stretching.

Mesenchyme

The first embryonic connective tissue to appear, containing mesenchymal cells and fine protein fibers, which gives rise to all other connective tissues.

Mucous Connective Tissue (Wharton's Jelly)

A loose embryonic connective tissue found within the umbilical cord of a fetus.

Areolar Tissue

The least specialized loose connective tissue in adults, containing loosely organized cells and fibers within an open, viscous framework.

White Fat

The common type of adipose tissue in adults that stores energy, provides cushioning and shock absorption, and insulates against heat loss.

Brown Fat

A highly vascularized adipose tissue found in infants and young children that metabolizes fat to release heat and warm the body.

Reticular Tissue

A loose connective tissue dominated by reticular fibers that creates a complex supportive three-dimensional framework for organs such as the liver, kidney, spleen, and lymph nodes.

Dense Regular Connective Tissue

A dense connective tissue consisting of parallel, tightly packed collagen fibers aligned with the lines of stress, forming tendons, ligaments, and aponeuroses.

Dense Irregular Connective Tissue

A dense connective tissue characterized by an interwoven network of collagen fibers lacking a consistent pattern, providing strength against multi-directional stress.

Elastic Tissue

A dense regular connective tissue made up primarily of elastic fibers, found in vertebral ligaments and large blood vessel walls.

Fascia

Connective tissue wrappings that support, surround, and stabilize organs and internal structures throughout the body.

Superficial Fascia

The layer of areolar and adipose tissue situated between the skin and underlying organs; also known as the subcutaneous layer or hypodermis.

Deep Fascia

Dense regular connective tissue sheets that form organ capsules and wrap muscles, tendons, ligaments, cartilages, and bones.

Subserous Fascia

A layer of areolar tissue located between deep fascia and the serous membranes lining body cavities.

Plasma

The watery, noncellular fluid matrix of blood containing dissolved proteins and electrolytes.

Erythrocytes

Anucleate red blood cells that account for about half of whole blood volume and transport oxygen and carbon dioxide.

Leukocytes

Nucleated white blood cells that defend the body against infection and foreign pathogens.

Platelets

Membrane-enclosed packets of cytoplasm and cell fragments that function in the blood clotting response to seal broken blood vessels.

Lymph

A fluid connective tissue that forms as interstitial fluid enters lymphatic vessels, consisting primarily of lymphocytes.

Cartilage

An avascular supporting connective tissue with a firm gel matrix containing chondroitin sulfates and chondrocytes located within lacunae.

Chondrocytes

Mature cartilage cells that occupy small chambers in the extracellular matrix called lacunae.

Perichondrium

A membrane surrounding cartilage composed of an outer fibrous layer for support and an inner cellular layer for growth and maintenance.

Hyaline Cartilage

The most common cartilage type; features closely packed collagen fibers providing stiff but flexible support at synovial joints, the ribs, larynx, and trachea.

Elastic Cartilage

A flexible cartilage type whose matrix is rich in elastic fibers, permitting repeated deformation without damage in structures like the auricle of the external ear and epiglottis.

Fibrocartilage

A durable, tough cartilage dominated by densely interwoven collagen fibers that resists compression and absorbs shocks in intervertebral discs and the pubic symphysis.

Interstitial Growth

A growth mechanism of cartilage where chondrocytes within lacunae divide and secrete additional matrix, enlarging the cartilage from within.

Appositional Growth

A growth mechanism where stem cells in the inner perichondrium differentiate into chondroblasts that secrete new matrix, adding layers to the outer cartilage surface.

Osseous Tissue

A supporting connective tissue with a calcified matrix containing calcium salts and strong, flexible collagen fibers.

Canaliculi

Fine, branching cytoplasmic passageways through the calcified bone matrix that connect lacunae to central canals for nutrient exchange.

Central Canal

A longitudinal channel located at the center of an osteon containing blood vessels that supply surrounding osteocytes.

Periosteum

A membrane covering the outer surface of bone consisting of an outer fibrous layer and an inner cellular layer.

Mucous Membranes

Moist tissue membranes that line passageways and chambers opening to the exterior, such as the digestive and respiratory tracts, supported by a lamina propria.

Lamina Propria

The layer of areolar connective tissue that supports the epithelium in a mucous membrane.

Serous Membranes

Thin, slick membranes consisting of mesothelium supported by areolar tissue that line sealed internal cavities of the trunk to reduce friction.

Cutaneous Membrane

The skin; a thick, dry, waterproof membrane composed of keratinized stratified squamous epithelium and underlying connective tissues.

Synovial Membrane

An incomplete tissue lining composed of areolar tissue and atypical epithelium that produces lubricating synovial fluid inside freely movable joint cavities.

Skeletal Muscle Tissue

Striated, voluntary muscle tissue composed of long, cylindrical, multinucleate cells known as muscle fibers.

Myosatellite Cells

Stem cells persisting in adult skeletal muscle tissue that divide and fuse to repair damaged muscle fibers.

Cardiac Muscle Tissue

Striated, involuntary muscle tissue restricted to the heart, featuring branched cells connected at intercalated discs with usually a single central nucleus.

Intercalated Discs

Specialized cell junctions connecting cardiac muscle cells that contain proteoglycans, desmosomes, and gap junctions to coordinate synchronous contractions.

Smooth Muscle Tissue

Nonstriated, involuntary muscle tissue consisting of small, spindle-shaped cells with a single central nucleus capable of cell division and regeneration.

Neurons

Nervous tissue cells specialized for the generation, reception, and transmission of electrical impulses.

Neuroglia

Supporting cells of nervous tissue that maintain tissue structure, repair damaged framework, perform phagocytosis, and supply nutrients to neurons.

Dendrites

Short, branching processes extending from a neuronal cell body that receive incoming signals from other neurons.

Axon

A long, thin cellular process extending from a neuron cell body that conducts outgoing electrical impulses to other cells.

Inflammation

The initial non-specific defense response of body tissues to injury or infection, characterized by redness, heat, swelling, pain, and loss of function.

Necrosis

The destruction and death of tissue that occurs after injury as lysosomal enzymes break down damaged cells and surrounding structures.

Abscess

An accumulation of pus—comprising tissue debris, fluids, and dying white blood cells—within an enclosed tissue space.

Regeneration

The repair process that restores normal tissue structure and physiological function after injury and inflammation subside.

Fibrosis

The permanent replacement of damaged normal tissue with dense, fibrous collagenous scar tissue that fails to restore original function.