Chapter 4: Tissue Level of Organization

KIN 267

Tissue

group of cells with a common embryonic origin and function that carry out specialized activities together

Cell junctions

points of contact between the plasma membrane of cells where cells are held to form tissues

Tight junctions

transmembrane proteins that seal off passageways between adjacent cells (bladder, stomach)

Adhering junctions

contain plaque that attaches to microfilaments and membrane proteins; join cells by cadherins (glycoproteins); help resist cell separation during muscle activity (food passing GI tract)

Plaque

dense protein layer in plasma membrane)

Desmosomes

contain plaque that attaches to membrane proteins containing keratin; involved in skin structure and cardia muscle; prevent cells from spreading (epidermis of skin)

Hemidesmosomes

anchor cells to basement membrane (link epithelium to connective tissue; assists in healing and regenerating tissue; involved in satellite cell activity in sections of muscle)

Gap junctions

tiny fluid-filled openings that connect nearby cells; allows molecules to pass from one cell to the other; communication mechanism between cells

Epithelial tissue

densely packed cells arranged in sheets; no spaces between plasma membranes; avascular; nerve supply; protects, secretes, absorbs and excretes; many cell junctions; attach to basement membrane

Surface epithelial tissue

forms skin and some organs, inner lining of blood vessels, ducts, body cavities

Glandular epithelial tissue

makes up portions of gland

Simple epithelium

one layer; involved in osmosis and diffusion

Pseudostratified epithelium

appear to have multiple layers; involved in absorption

Stratified epithelium

multiple layers; invovled in protection

Squamous epithelium

very thin; allows rapid movement of substances

Cuboidal epithelium

very wide; typically have microvilli for absorption

Columnar epithelium

very tall; have cilia or microvilli for secretion and absorption

Connective tissue

cells and extracellular matrix (ground substance and protein fibers); highly vascularized (except tendons and cartilage); nerve supply (except cartilage)

Ground substance

material between cells and fibers made of water and organic molecules; support and bind cells, stores water; where substances between blood and cells are exchanged

Collagen fibers

very strong and flexible; found in cartilage, bone

Elastic fibers

strong and stretchable; found in skin, blood vessels, and lung tissue

Reticular fibers

provide structural support in blood vessel walls and form branching networks around fat, smooth muscle, nervous, etc.

Cartilage

made by few chondrocyte cells (produce collagen); consists of collagen fibers for strength and chondroitin sulfate for resilience (gel-like component of ground substance); no nerve or blood supply in extracellular matrix

Hyaline cartilage

provides smooth surfaces for movement at joints, flexibility, and support; weakest type, fracturable; most abundant; long bone ends, anterior ends of ribs, nose, trachea)

Fibrous cartilage

support and join structures together; strong, rigid; strongest type; IV discs, menisci of knee, portions of tendons

Elastic cartilage

provides strength and elasticity; maintains shape of structures; epiglottis, part of external ear

Muscular tissue

consists of fibers that provide motion, maintain posture, and produce heat; smooth, skeletal, and cardiac

Skeletal muscle tissue

responsible for motion, posture, heat production, protection

Cardiac muscle tissue

pumps blood to all parts of body

Smooth muscle tissue

responsible for constriction of blood vessels and airways, propulsion of foods through gastrointestinal tract, contraction of urinary bladder and gallbladder

Nervous tissue

exhibit sensitivity to various stimuli and convert them into nerve impulses, generate action potentials, which are conducted to other nerve cells, muscle fibers, or glands

Neurons

carry sensory or motor info; perform integrative functions; most have a cell body, one to multiple dendrites, and an axon

Neuroglia

protect and support neurons

Excitable cells

neuron and muscle fibres that can respond to certain stimuli by producing electrical signals (AP) which travel along neural PM or muscle fibre due to the presence of specific voltage-gated channels

Tissue repair

replacing worn out, damaged, or dead cells

Fibrosis

forming of scar tissue