Chapter 4 The Tissue Level of Organization

Flashcards covering the four tissue types, epithelium, connective tissue, muscle tissue, and nervous tissue

Tissues

Collections of specialized cells and cell products that perform specific functions; in combination, they form organs.

Histology

The study of tissues.

Epithelial tissue

Covers exposed surfaces, lines internal passageways, and forms glands.

Connective tissue

Fills internal spaces, supports other tissues, transports materials, and stores energy.

Muscle tissue

Specialized for contraction and includes skeletal, heart, and muscular walls of hollow organs.

Nervous tissue

Carries electrical signals from one part of the body to another.

Epithelia

Layers of cells covering internal or external surfaces.

Glands

Structures that produce fluid secretions.

Functions of epithelial tissue

Provide physical protection, control permeability, provide sensation, and produce specialized secretions.

Cellularity

Cell junctions

Proteoglycans

Contain glycosaminoglycans such as hyaluronan (hyaluronic acid).

Gap junctions

Allow rapid communication; cells held together by interlocking transmembrane proteins (connexons); coordinate contractions in heart muscle

Tight junctions

Between two plasma membranes; adhesion belt attaches to terminal web; prevent passage of water and solutes; keep enzymes, acids, and wastes in the lumen of the digestive tract

Desmosomes

CAMs and proteoglycans link opposing plasma membranes; tie cells together and allow bending and twisting; attach cells to the basement membrane

Basal lamina

Closest to the epithelium.

Reticular lamina

Deeper portion of basement membrane; provides strength.

Squamous

Thin and flat.

Cuboidal

Square shaped.

Columnar

Tall, slender rectangles.

Simple epithelium

Single layer of cells.

Stratified epithelium

Several layers of cells.

Mesothelium

Lines body cavities.

Endothelium

Forms inner lining of heart and blood vessels.

Endocrine glands

Glands are collections of epithelial cells that produce secretions; release hormones that enter bloodstream; no ducts

Exocrine glands

Produce exocrine secretions; discharge secretions through ducts onto epithelial surfaces

Goblet cells

Unicellular exocrine glands; in epithelia of intestines; secrete mucin, which mixes with water to form mucus

Merocrine secretion

Released by secretory vesicles (exocytosis); Example: merocrine sweat glands

Apocrine secretion

Released by shedding cytoplasm; Example: mammary glands

Holocrine secretion

Released by cells bursting, killing gland cells; gland cells replaced by stem cells; Example: sebaceous glands

Serous glands

Watery secretions

Mucous glands

Secrete mucins

Mixed exocrine glands

Both serous and mucous

Components of connective tissues

Specialized cells, extracellular protein fibers, and fluid called ground substance

Matrix

Consists of extracellular components of connective tissue (fibers and ground substance); majority of tissue volume; determines specialized function

Connective tissue proper

Connect and protect.

Fluid connective tissues

Transport.

Supporting connective tissues

Structural strength.

Fibroblasts

The most abundant cell type; found in all types of connective tissue proper; secrete proteins and hyaluronan (cellular cement).

Fibrocytes

Second most abundant cell type; maintain connective tissue fibers.

Adipocytes

Fat cells; each cell stores a single, large fat droplet

Mesenchymal cells

Stem cells that respond to injury or infection; differentiate into fibroblasts, macrophages, etc.

Melanocytes

Synthesize and store the brown pigment melanin.

Macrophages

Large phagocytic cells of the immune system; engulf pathogens and damaged cells; fixed macrophages stay in tissue

Mast cells

Stimulate inflammation after injury or infection; Release histamine and heparin

Lymphocytes

Migrate throughout the body; may develop into plasma cells, which produce antibodies.

Microphages

Phagocytic blood cells (neutrophils, eosinophils); attracted to signals from macrophages and mast cells

Collagen fibers

Long, straight, and unbranched; strong and flexible; resist force in one direction; abundant in tendons and ligaments.

Reticular fibers

Form a network of interwoven fibers (stroma); strong and flexible; resist forces in many directions; stabilize functional cells (parenchyma) and structures.

Elastic fibers

Contain elastin; branched and wavy; return to original length after stretching.

Ground substance

Is clear, colorless, and viscous; fills spaces between cells and slows pathogen movement.

Dense regular connective tissue

Tightly packed, parallel collagen fibers; attach muscles to bones; connect one bone to another and stabilize organs; are tendinous sheets that attach a broad, flat muscle to another structure

Dense irregular connective tissue

Interwoven network of collagen fibers; provides strength to dermis; forms sheath around cartilages (perichondrium) and bones (periosteum)

Elastic tissue

Made of elastic fibers (elastic ligaments of spinal vertebrae)

Fasciae

Connective tissue layers and wrappings that support and surround organs.

Superficial fascia

Separates skin from underlying tissues

Deep fascia

Sheets of dense regular connective tissue.

Subserous fascia

Lies between deep fascia and serous membranes that line body cavities.

Blood

Contains a watery matrix called plasma; contains cells and cell fragments, collectively known as formed elements.

Lymph

Forms as interstitial fluid that enters lymphatic vessels; monitored by immune system; returned to veins near the heart.

Perichondrium

Outer, fibrous layer (for support and protection) & inner, cellular layer (for growth and maintenance)

Interstitial growth

Enlarges cartilage from within.

Appositional growth

Growth at outer surface of cartilage

Osteocytes

Bone cells lie in lacunae; arranged around central canals within matrix; small channels through matrix (canaliculi) allow for exchange of materials with blood

Tissue Membranes

Tissue membranes consisting of an epithelium supported by connective tissue; physical barriers that line or cover body surfaces.

Mucous membranes

Line passageways that have external connections; in digestive, respiratory, urinary, and reproductive tracts

Serous membranes

Lines cavities that do not open to the outside; thin but strong; parietal portion lines inner surface of cavity

Cutaneous membrane

Skin that covers the body; thick, relatively waterproof, and usually dry.

Synovial membranes

Line synovial joint cavities; movement stimulates production of synovial fluid for lubrication; lack a true epithelium

Skeletal muscle

Large muscles responsible for body movement; striated voluntary muscle

Cardiac muscle

Found only in the heart; striated involuntary muscle

Smooth muscle

Found in walls of hollow, contracting organs; nonstriated involuntary muscle

Cardiac Muscle Tissue

Cells form branching networks connected at intercalated discs; regulated by pacemaker cells

Nervous tissue

Specialized for conducting electrical impulses; concentrated in the brain and spinal cord

Dendrites

Short branches extending from the cell body that receive incoming signals

Axon (nerve fiber)

Long, thin extension of the cell body that carries outgoing electrical signals to their destination.

Tissue Repair

Tissues respond to injury in two stages: Inflammation (inflammatory response) and Regeneration to restore normal function

Inflammatory response

Damaged cells release prostaglandins, proteins, and potassium ions; damaged connective tissue activates mast cells

Necrosis

Lysosomes release enzymes that destroy the injured cells and attack surrounding tissues.