HISTOLOGYThe Study of Body Tissues:

Epithelial, Connective, Muscle, Nervous

BODY TISSUES

Tissues

…Groups of cells with similar structure and function

…Four primary types Epithelial tissue (epithelium)

Connective tissue

Muscle tissue

Nervous tissue

EPITHELIAL TISSUES: MEMBRANEOUS

Locations

… Body coverings

… Body linings- digestive & respiratory tract

Functions

… Protection

… Absorption

… Filtration

… Secretion

EPITHELIUM CHARACTERISTICS Cells fit closely together and often form

sheets

The apical surface is the free surface of the tissue, covers major glands

The lower surface of the epithelium rests on a basement membrane

Avascular (no blood supply)

Regenerate easily if well nourished

EPITHELIAL TISSUE: GLANDULAR

Glandular secretes from endocrine & exocrine glands

EPITHELIUM CHARACTERISTICS

CLASSIFICATION Shape of cells

…Squamous: flat, single layer

…Cuboidal: cube-shaped

…Columnar:column

… Transitional: change form squamous to cuboidal

CLASSIFICATION Number of cell

layers

…Simple—one layer

…Stratified—more than one layer

…Pseudostratified- appears as many layers but only one

SIMPLE EPITHELIA

Simple squamous

…Single layer of flat cells

…Tightly packed

…Permeable to oxygen thru diffusion

… Lines body cavities

Lines lungs and capillaries

SIMPLE EPITHELIA

SIMPLE EPITHELIA

Simple cuboidal

… Single layer of cube-like cells

… Common in glands and their ducts

… Secretes & absorption

… Forms walls of kidney tubules

… Covers the ovaries

SIMPLE EPITHELIA

SIMPLE EPITHELIA Simple columnar

… Single layer of tall cells

… Often includes mucus-producing goblet cells

… Nuclei near bottom

… Absorption, secretion & transport

… Cells with microvilli for absorption

… Lines digestive tract & uterus

SIMPLE EPITHELIA

SIMPLE EPITHELIA Pseudostratified columnar

… Single layer, but some cells are shorter than others, varying heights

… Often looks like a double layer of cells

… Sometimes ciliated, such as in the respiratory tract

… May function in absorption or secretion

SIMPLE EPITHELIA

STRATIFIED EPITHELIA

Stratified squamous

…Many layers of flat cells

…Found as a protective covering where friction is common, wear & tear

…Locations Skin, Mouth, Esophagus & Vagina

STRATIFIED EPITHELIA

STRATIFIED EPITHELIA Stratified cuboidal—two layers of

cuboidal cells

Stratified columnar—surface cells are columnar, cells underneath vary in size and shape

Stratified cuboidal and columnar

… Rare in human body

… Found mainly in ducts of large glands

STRATIFIED EPITHELIA Transitional epithelium

… Shape of cells depends upon the amount of stretching

… Multiple layers, change from squamous to cube

… Lines hollow organs, under stress: bladder

… Lin

STRATIFIED EPITHELIA

GLANDULAR EPITHELIUM Gland

… One or more cells responsible for secreting a particular product

… Cells are responsible for producing and secreting

GLANDULAR EPITHELIUM Two major gland types

…Endocrine gland Ductless since secretions diffuse into

blood vessels

All secretions are hormones

…Exocrine gland Secretions empty through ducts to

the epithelial surface

Include sweat and oil glands

GLANDULAR EPITHELIUM

GLANDULAR TYPES Apocrine:Secretion results in damage to cell membrane

& loss of cytoplasm EX: mammary glands

Holocrine:Secretion products causes rupture & death of

cell

EX: sebaceous glands/ oil glands

Merocrine:Most numerous, secretion w/o loss of cytoplasm

EX: sweat glands

CONNECTIVE TISSUE

Found everywhere in the body

Includes the most abundant and widely distributed tissues

Functions

… Binds body tissues together

… Supports the body

… Provides protection

… Transports

CONNECTIVE TISSUE CHARACTERISTICS Variations in blood supply

… Some tissue types are well vascularized

… Some have a poor blood supply or are avascular

Extracellular matrix

… Non-living material that surrounds living cells

… Defines connective tissue characteristics

… Matrix may be solid, gel or liquid w or w/o fibers

EXTRACELLULAR MATRIXTypes of Fibers: Three types

…Collagen: made of collagen- tough & stingy

Bundles for strength, protein, white

…Elastic yellow fibers, stretches- elastic & returns to original length after stretch, found in come cartilage

…Reticular fibers: delicate, in networks, found in capillaries & nerve fibers

CONNECTIVE TISSUE TYPES Loose connective tissue types

…Areolar tissue Most widely distributed connective

tissue

Soft, pliable tissue like “cobwebs”

Functions as a packing tissue

Contains collagen & elastic fibers

Can soak up excess fluid (causes edema)

Found between skin & muscle- Fascia

CONNECTIVE TISSUE TYPES

CONNECTIVE TISSUE TYPES Loose connective tissue types

…Adipose tissue Matrix is large lipid deposits

Functions

… Insulates the body

… Protects & supports some organs

… Serves as a site of fuel storage

… found thruout body

CONNECTIVE TISSUE TYPES

CONNECTIVE TISSUE TYPES Loose connective tissue types

…Reticular connective tissue Delicate network of interwoven fibers

Forms network of lymphoid organs

Found in Lymph nodes, Spleen, Bone marrow

Function is to defend against microorg. & filter out harmful particles

Phagocytocize

CONNECTIVE TISSUE TYPES

CONNECTIVE TISSUE TYPES Dense fibrous tissue

Main matrix element is collagen fiber

Provide strong connections & flexibility

…Locations Tendons—attach skeletal muscle to

bone

Ligaments—attach bone to bone at joints

Dermis—lower layers of the skin

CONNECTIVE TISSUE TYPES

CONNECTIVE TISSUE TYPES Bone (osseous tissue)

…Composed of Bone cells: osteocytes

Hard matrix of calcium salts

Large numbers of collagen fibers

…Used to protect, support, mineral reserve & muscle attachement

CONNECTIVE TISSUE TYPES

CONNECTIVE TISSUE TYPES Hyaline cartilage

…Most common type of cartilage

…Composed of: collagen fibers, rubbery/gel matrix- shiny & translucent

… Contains chondrocytes (cartilage cells)

… Avascular

…Locations: End of articulating bones, fetal skeleton prior to birth

CONNECTIVE TISSUE TYPES

CONNECTIVE TISSUE TYPES

Elastic cartilage…Provides elasticity & flexibility

…Has fine elastic fibers to make it more bendable than hyaline

…Location: Supports the external ear, nose

CONNECTIVE TISSUE TYPES

CONNECTIVE TISSUE

Fibrocartilage• Strong & durable, highly compressibleShock absorber• Location: discs between vertebrae, pubic

symphysis

CONNECTIVE TISSUE TYPES

CONNECTIVE TISSUE TYPES Blood (vascular tissue)

… Blood cells surrounded by LIQUID matrix called blood plasma

… Fibers are only visible during clotting

… Functions as the transport vehicle for materials

… protection

CONNECTIVE TISSUE TYPES

MUSCLE TISSUE Specialized cells involved in

contraction

Function is to produce movement

Three types

… Skeletal muscle

… Cardiac muscle

… Smooth muscle

MUSCLE TISSUE TYPES Skeletal muscle

… Under voluntary control

… Contracts to pull on bones or skin

… Produces gross body movements or facial expressions

… Characteristics of skeletal muscle cells Striated

Multinucleate (more than one nucleus)

Long, cylindrical

MUSCLE TISSUE TYPES

MUSCLE TISSUE TYPES Cardiac muscle

… Under involuntary control

… Found only in the heart

… Function is to pump blood

… Characteristics of cardiac muscle cells Striated

Branching ends

One nucleus per cell

MUSCLE TISSUE TYPES

MUSCLE TISSUE TYPES

Smooth muscle

… Under involuntary muscle

… Found in walls of hollow organs such as stomach, uterus, and blood vessels

… Characteristics of smooth muscle cells No visible striations

One nucleus per cell

Spindle-shaped cells

MUSCLE TISSUE TYPES

NERVOUS TISSUE Composed of neurons and nerve

support cells called neuroglia

Function is to send impulses to other areas of the body

… Irritability- changing nerve impulse

… Conductivity- transmit nerve impulse

… Found in : brain, nerves & spinal cord

NERVOUS TISSUE

TISSUE REPAIR (WOUND HEALING) Three Phases

… Inflammatory Phase

To remove injury causing agent and limiting tissue damage

Redness, swelling, heat and loss of function

Blood vessels dilate and fluid move into tissue. Blood clotting occurs.

This also allow WBC’s to move to injury to clean up bacteria and other debris

TISSUE REPAIR (WOUND HEALING)

Chemicals released to attract fibroblasts (connective tissue cells that make collagen fibers)

… Proliferative Phase

Fibroblasts make collagen fibers that fill the space. Blood vessels also start to regenerate and fill the space

Surrounding cells begin to divide and form granulation tissue –new and lots of blood vessels so it’s pink

TISSUE REPAIR (WOUND HEALING) Epitheliazation—epithelial cells divide

and move into space with collagen fibers

WBC’s leave and swelling decreases so it turns white

… Remodeling Phase (3 weeks – 6 months)

Collagen continues to be formed (how much depends on severity of wound)

Epithelial cells move into place

Scab detaches

REGENERATION OF TISSUES Tissues that regenerate easily

… Epithelial tissue (skin and mucous membranes)

… Fibrous connective tissues and bone

Tissues that regenerate poorly

… Skeletal muscle

Tissues that are replaced largely with scar tissue

… Cardiac muscle

… Nervous tissue within the brain and spinal cord