Comprehensive Tissues and Membranes: Types, Functions, and Locations

Tissues

Group of cells that carry out specialized activities.

Histo

Tissue.

Ology

Study of.

Pathologists

Study of cells and tissue; diseased.

Patho

Disease.

Epithelial Tissue

Covers body surfaces, cavity linings, hollow organs, ducts, and glands.

Connective Tissue

Protects and supports, binds organs together, stores energy reserves as fat.

Muscle Tissue

Generates the force needed to make structures move.

Nervous Tissue

Stimulates action potential to coordinate body functions.

Ectoderm

The primary layer which gives rise to the nervous system and the epidermis of skin.

Mesoderm

The middle germ layer which gives rise to connective tissue, blood, muscles.

Endoderm

The lower germ layer that gives rise to the GI tract, urinary bladder, and respiratory tract.

Cell Junctions

Points of contact between adjacent membranes of various cell types.

Tight Junctions

Fluid tight seal between cells to prevent leaking of substances into the blood or surrounding tissues.

Desmosomes

Fasten cells to one another; common in stretched areas such as heart, uterus, outer skin.

Gap Junctions

Allow passage of chemical/electrical signals through connexons from cell to cell.

Simple Epithelium

Single layer; functions in osmosis, diffusion, absorption, and secretion.

Stratified Epithelium

Two or more layers; protects underlying tissues in areas of wear and tear.

Pseudostratified Epithelium

One layer of mixed cells; functions in mucus secretion and movement.

Squamous Cells

Flat cells.

Cuboidal Cells

Thick, cube-shaped cells.

Columnar Cells

Tall, cylindrical cells.

Transitional Cells

Cells that vary in shape.

Simple Squamous Epithelium

Function: Filtration, diffusion, osmosis, and secretion in serous membranes.

Simple Cuboidal Epithelium

Function: Secretion and Absorption.

Simple Columnar Epithelium (Non-Ciliated)

Function: Secretion and Absorption; Microvilli and Goblet cells.

Ciliated Simple Columnar Epithelium

Function: Moves fluids and particles along passageways.

Pseudostratified Columnar Epithelium

Functions: Mucus secretion & movement by cilia action.

Stratified Squamous Epithelium

Functions: Protection of superficial layers of skin, vagina, mouth, esophagus, tongue.

Keratinized Stratified Squamous Epithelium

Location: Superficial Layers of Skin.

Non-Keratinized Stratified Squamous Epithelium

Location: Wet Surfaces (Mouth, Vagina, Tongue).

Stratified Cuboidal Epithelium

Functions: Protection and limited secretion and absorption; rare type. Location: in the ducts of sweat glands and esophageal glands.

Stratified Columnar Epithelium

Functions: Protection and secretion. Location: urethra, ducts of some glands, anal membranes, parts of the eye; uncommon.

Transitional Epithelium

Function: Accommodate distension in the urinary tract as fluid pressures vary. Stretched = Stratified Squamous; Relaxed = Stratified Cuboidal. Location: Lining of the ureters, urethra, and bladder.

Glandular Epithelium

The function of glandular epithelium is secretion.

Gland

A gland consists of one cell or a group of highly specialized epithelial cells secreting substances into ducts, onto a surface, or into the blood.

Endocrine Glands

Function: Produce hormones; ductless glands that secrete directly into the bloodstream. Location: Thyroid, Pituitary, Adrenal Gland, Ovaries, and Testes.

Exocrine Glands

Function: Secrete products into ducts (tubes) that empty at the surface of covering and lining epithelium or onto a free surface. Examples: sweat glands, salivary glands, and digestive tract glands.

Merocrine (or Eccrine) Secretion

Forms the product and discharges from the cell completely. Example: Salivary Glands.

Apocrine Secretion

Product forms at apical surface and pinches off from rest of cell. Example: Mammary gland.

Holocrine Secretion

Accumulates secretory product in cytosol, cell dies, and is discharged with its product. Example: Sebaceous Gland (Acne).

Functions of Connective Tissue

Binds together, supports, and strengthens other body tissues; protects and insulates internal organs; the major transport system within the body (blood); the major site of stored energy reserves (adipose); the main site of immune responses.

Connective Tissue Composition

Connective tissue consists of two basic elements: cells and extracellular matrix.

Extracellular Matrix

The material between its widely spaced cells and consists of protein fibers and ground substance.

Fibroblasts

Large, flat cells responsible for the secretion of matrix compounds; most numerous.

Macrophages

Phagocytes that develop from monocytes and eat bacteria.

Plasma Cells

Synthesized from a B lymphocyte; secrete antibodies.

Mast Cells

Involved in the inflammatory response (histamine production) and also kill bacteria.

Adipocytes

Fat cells that store triglycerides.

Ground Substance

The component of a connective tissue between the cells and fibers; supports cells, binds them together, and allows the exchange of materials between blood and cells.

Hyaluronic Acid

Cell binding, lubricating joints, wound healing.

Chondroitin Sulfate

Adhesiveness for bone, cartilage, skin, and blood vessels.

Glucosamine

Maintains joint structure and function and reduces inflammation.

Collagen Fibers

Very strong and resist pulling forces, but they are not stiff, which promotes tissue flexibility.

Elastin Fibers

Strong but can be stretched up to 1½ times their relaxed length without breaking.

Reticular Fibers

Form the framework (stroma) of many internal soft organs; form the basement membrane.

Loose Connective Tissue

Provides strength, elasticity, and support to the subcutaneous layer of skin.

Dense Connective Tissue

Dense, closely packed collagen fibers that provide high tensile strength.

Cartilage

Extremely strong, but very flexible and elastic; provides smooth surface for reduction of friction.

Bone

Provides support, involved in movement, and the production of marrow (blood-forming).

Liquid Connective Tissue

Includes blood and lymph; involved in clotting and immunity.

Adipose Fat (White)

Used for insulation, energy reserve, and fat storage.

Adipose Fat (Brown)

Generates body heat in newborns that do not shiver; most mitochondria disappear as infants grow up.

Reticular Connective Tissue

A network of reticular fibers and reticular cells; forms the stroma of soft organs such as the liver, spleen, and lymph nodes.

Fibrocartilage

Extremely tough; acts as a shock absorber, found between ball and socket joints, intervertebral discs, meniscus of the knees.

Elastic Cartilage

Abundance of elastin for stretching capability; found in ears and epiglottis.

Skeletal Muscle Tissue

Attached to bones by tendons; functions in body movements, posture, and thermogenesis.

Cardiac Muscle Tissue

Composes the heart wall; functions in pumping blood to all parts of the body.

Smooth Muscle Tissue

Forms walls of many internal organs; functions in motion of internal organs.

Neuron

Conversion from stimulus response to action potential; consists of dendrites and axons.

Dendrites

React to stimuli.

Axons

Conductor of impulse.

Epithelial Membranes

Combination of an epithelial layer and underlying connective tissue.

Mucous Membranes

Line a body cavity that opens directly to the exterior; found in the digestive, respiratory, and reproductive systems.

Serous Membranes

Line body cavities that do not open directly to the exterior and cover the organs within the cavity.

Synovial Membranes

Line the cavities of some joints.

Tissue Repair

Replaces worn-out, damaged, or dead cells with healthy ones; varies by tissue type.

Aging and Tissue Repair

With aging, tissues heal more slowly and produce more scars.