Unit 3 Tissues

Tissue

Group of cells with similar structure and function that perform specialized tasks.

Histology

Study of tissues.

Epithelial Tissue

Compact arrangement of cells that covers body surfaces.

Functions of Epithelial Tissue

Protection, barrier, secretion, absorption.

Simple Epithelial

Single layer of cells.

Stratified Epithelial

Two or more layers of cells.

Pseudostratified Epithelial

One layer that looks like multiple layers.

Squamous Cells

Flat, scale-like cells.

Cuboidal Cells

Cube-shaped cells.

Columnar Cells

Tall, column-shaped cells.

Transitional Cells

Shape changes when stretched.

Keratinized Stratified Squamous Epithelium

Contains keratin protein; surface cells are dead.

Non-Keratinized Stratified Squamous Epithelium

Does not have a thick keratinized surface; found in moist areas.

Transitional Epithelium

Specialized type of stratified epithelium that can be greatly stretched.

Cell Contacts

Structures that hold cells together and allow them to communicate.

Hemidesmosomes

Anchor epithelial cells to the basement membrane.

Tight Junctions

Prevent substances from passing between epithelial cells.

Gap Junctions

Small channels between neighboring cells that allow small molecules to pass.

Exocrine Glands

Secretes substances onto a surface or into a duct.

Endocrine Glands

Releases hormones into the blood without ducts.

Classification by Structure

Simple (single, unbranched duct) and compound (branched duct).

Merocrine Secretion

Secretion occurs while the cell remains intact through exocytosis.

Apocrine Secretion

Portion of the cell is lost during secretion.

Holocrine Secretion

The entire cell disintegrates to release its secretion.

Connective Tissues

Found throughout the body; contains cells embedded in an extracellular matrix.

Functions of Connective Tissues

Enclose and separate tissues, connect tissues, support and move body parts, store compounds, cushion and insulate.

Extracellular Matrix Components

Protein fibers, ground substance, and fluid.

Collagen Fibers

Strong, flexible fibers that resist stretching.

Reticular Fibers

Form a supporting network/framework.

Proteoglycans

Molecules that trap large amounts of water and provide cushioning within the ECM.

Types of Loose Connective Tissues

Areolar, adipose, reticular.

Adipose Tissue

Provides energy storage and acts as a thermal insulator.

Reticular Tissue

Forms the structural framework of lymphatic organs.

Dense Connective Tissue

Contains collagen and elastic fibers.

Dense Irregular Tissue

Fibers arranged in different directions; mostly collagen fibers.

Hyaline Cartilage

Most abundant type of cartilage.

Fibrocartilage

Has more collagen fibers; provides extra strength.

Elastic Cartilage

Rich in elastic fibers and proteoglycans; can recoil after stretching.

Bone (Osseous Tissue)

Hard connective tissue consisting of living cells and mineralized matrix.

Compact Bone

More solid and dense; almost no visible spaces.

Spongy Bone

Contains open spaces between plates called trabeculae.

Blood

Liquid connective tissue.

Components of Blood

Red blood cells, white blood cells, platelets suspended in plasma.

Functions of Blood

Transports nutrients, oxygen, metabolic wastes, hormones, and other substances.

Muscle Tissue

Ability to contract, shorten, and generate physical movement.

Types of Muscle Tissue

Skeletal muscle, cardiac muscle, smooth muscle.

Nervous Tissue

Coordinates and controls body activities using electrical signals.

Structure of Nervous Tissue

Contains neurons with cell body, dendrites, and axon.

Tissue Membranes

Thin sheet/layer of tissue that covers surfaces, lines cavities, or covers internal organs.

Cutaneous Membrane

Skin; external body surface.

Mucous Membrane

Lines passages that open to the outside; respiratory and digestive.

Serous Membrane

Lines closed body cavities and covers organs within them.

Synovial Membrane

Lines joint cavities.

Tissue Inflammation

Beneficial protective process that occurs when tissue is damaged.

Signs of Inflammation

Redness, heat, swelling, pain, loss of function.