Unit 2 Tissues

Epithelial tissue

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

Epithelial characteristics

Closely packed cells, little extracellular matrix, desmosomes and tight junctions, polarity, and rapid regeneration.

Apical surface

Free surface of epithelial tissue exposed to air or fluid.

Basement membrane

Thin layer anchoring epithelium to connective tissue.

Avascular epithelium

Contains no blood vessels.

Simple squamous epithelium

Single layer of flat cells; diffusion and filtration.

Microscope ID (simple squamous)

Thin, flat cells with flattened nuclei.

Stratified squamous epithelium

Multiple layers

Microscope ID (stratified squamous)

Many layers; cells flatten toward surface.

Cuboidal epithelium

Cube-shaped cells; secretion and absorption.

Microscope ID (cuboidal)

Square cells with round central nuclei.

Columnar epithelium

Tall cells; absorption and secretion.

Microscope ID (columnar)

Elongated cells with nuclei near the base.

Connective tissue

Most abundant tissue type; supports, binds, and protects.

Connective tissue characteristics

Cells separated by extracellular matrix; usually vascular.

Vascular connective tissue

Most connective tissues have blood supply.

Avascular connective tissue

Cartilage, tendons, and ligaments lack blood vessels.

Extracellular matrix

Nonliving material made of fibers and ground substance.

Microscope ID (connective)

Cells scattered with visible fibers and matrix between them.

Bone

Hard connective tissue providing support and protection.

Microscope ID (bone)

Concentric rings (osteons) with central canals.

Cartilage

Flexible connective tissue providing support and cushioning.

Microscope ID (cartilage)

Cells in lacunae surrounded by smooth matrix.

Dense connective tissue

Strong tissue with tightly packed collagen fibers.

Microscope ID (dense CT)

Parallel collagen fibers with flattened nuclei.

Adipose tissue

Fat-storing connective tissue.

Microscope ID (adipose)

Large empty-looking cells with nuclei pushed to side.

Muscle tissue

Tissue specialized for contraction and movement.

Muscle characteristics

Excitability, contractility, extensibility, elasticity.

Vascular muscle tissue

Muscle tissue is well vascularized.

Microscope ID (muscle)

Elongated cells (fibers) that may show striations.

Skeletal muscle

Voluntary muscle attached to bones.

Microscope ID (skeletal)

Long, striated fibers with multiple nuclei.

Cardiac muscle

Involuntary muscle of the heart.

Microscope ID (cardiac)

Striated, branching cells with intercalated discs.

Smooth muscle

Involuntary muscle in walls of organs.

Microscope ID (smooth)

Spindle-shaped cells with no striations.

Nervous tissue

Tissue that conducts electrical impulses for communication and control.

Vascular nervous tissue

Nervous tissue is vascular.

Microscope ID (nervous)

Large neurons with long extensions and many small supporting cells.