Histology

The study of tissues

Tissue

A group of similar cells working together to perform a common function.

4 Types of Tissues Epithelial Connective Muscle Nervous

Epithelial Tissue

Covers a body surface or lines a body cavity

Characteristics of Epithelial Tissue

Composed of closely packed cells with specialized points of attachment

Have a free surface and attached to a basement membrane

Avascular but innervated

Rapid cell division Specialized to form

glands

Functions of Epithelial Tissue Protection Absorption Secretion

Filtration Excretion Sensory

Classification of Epithelial Tissue

Cell Shape:Squamous – flattened cells

Cuboidal- boxes

Columnar-tall

Cell Arrangement:Simple – single layers

Stratified – multiple layers

Examples of Epithelial Tissue

Simple Squamous Epithelium(Alveoli of lungs & linings of Blood vessels)

Simple Cuboidal Epithelium(Kidney tubules) A. Cuboidal cells

B. Nucleus of cell

Simple Columnar Epithelium(Digestive Tract)

A. Columnar cellsB. NucleusC. Cell membrane

Pseudostratified Epithelium(Trachea) A. Basement

membraneB. CiliaC. Nucleus

Stratified Squamous Epithelium(Lining of mouth)

A. Layers of epithelium

B. Surface cells

Stratified Squamous Epithelial(Human Cheek Cells)

A. NucleusB. CytoplasmC. Cell Membrane

Transitional Epithelium(Urinary bladder) A. Surface cells

B. Attached cells

Specialized for stretching

Connective Tissue

Connective Tissue

Found everywhere in the body; most abundant and widely distributed of all the tissues.

Characteristics of Connective Tissue

Cells widely separated by an extracellular matrix

Varying degrees of vascularization

Functions of Connective Tissue Binding and support Protection Insulation Transportation

Structural Elements Ground Substance

– unstructured material that fills the space between the cells

Cells Fibers

Collagen fibers Elastic fibers Reticular fibers

Examples of Connective Tissue

Areolar Connective Tissue(beneath the skin)

A. FibroblastsB. Collagen fibersC. Elastic fibers

Reticular Tissue(Spleen, liver, lymph nodes)

A. Reticular fibers

Adipose Tissue(Fat)

A. Nucleus of fat cellB. Fat droplet

Dense Fibrous Connective Tissue(Tendons)

A. FibroblastsB. Collagenous

fibers

Hyaline Cartilage(Ends of bones, trachea, larynx)

A. ChrondrocyteB. MatrixC. Lacuna

Bone A. Central Canal

B. LamellaeC. Osteocyte in

lacunaD. Canaliculi

Blood Leucocytes

(White Blood Cells)

Erythrocytes (Red Blood Cells)

Sickle Cells

Muscle Tissue

Responsible for body movements

Classification Location

Skeletal Cardiac Visceral

Appearance Smooth Striated

Action Voluntary Involuntary

Skeletal Muscle:Attached to bones for movement

AKA: Muscle fibers Long, blunt,

cylindrical Multinucleated Striated Voluntary

A. Width of cellB. Nucleus

Cardiac Muscle:Found in heart

Involuntary Mononucleate Branched StriatedA. Intercalated discsB. Nucleus

Visceral/Smooth Muscle:Found in walls of hollow organs

Involuntary Spindle-shaped Mononucleate No visible

striations

B. Nucleus

Nervous Tissue

Regulates and controls body functions

2 Major Cell Types

NeuronsGenerate and

conduct nerve impulses

Functional cells of the nervous system

Supporting CellsNonconductingSupport, protect and

insulate neurons

Neuroglia

Parts of Neuron

Cell Body Dendrite

Receives information from sensory receptors Axon

Carries impulses away from cell body to target structure

Neurons & Neuroglia A. Cell Body

B. Cell Process (axon or dendrite)

C. Neuroglia (small dark dots)

Neuromuscular Junction A. Axon

B. Motor end platesC. Skeletal cell