Tissues

Tissues

Group of cells that are similar in structure

and function

4 primary types

● Epithelium (covering)

● Connective (support)

● Nervous(control)

● muscle(movement)

Epithelial tissue (epithelium)

Lining, covering, and glandular tissue of the

body

Functions: protection, absorption,

filtration, and secretion

Special characteristics of epithelium - Cells fit closely together to form continuous

sheets

- Membranes have one free surface (apical surface)

which is exposed to body’s exterior or cavity

- Lower surface of epithelium rests on a basement

membrane (structureless material secreted by

cells)

- No blood supply of their own (avascular) and

depend on diffusion from capillaries in the

underlying connective tissue

- Regenerate easily if well nourished

Classification of epithelium

Simple epithelium- one layer of cells- most

concerned with absorption, secretion, and

filtration (not protection)

Stratified epithelium- more than one layer of

cells- function primarily to protect

shapes

Squamous cells- flattened cells like fish

scales

Cuboidal cells- cube-shaped like dice

Columnar cells- shaped like columns

Combine these with simple and stratified to

describe the epithelium fully

Simple epithelium Simple squamous epithelium-

single layer of thin

squamous cells resting on a

basement membrane- usually

forms membranes where

filtration or exchange

occurs by rapid diffusion-

also forms serous membranes

that line ventral body

cavity and cover the organs

in that cavity

Simple epithelium

Simple cuboidal

epithelium- 1 layer of

cuboidal cells resting

on a basement

membrane- common in

glands or ducts- forms

walls of kidney

tubules and surface of

ovaries

Simple epithelia Simple columnar epithelium-

single layer of tall cells that

fit closely together- lines

entire length of the digestive

tract

Goblet cells- produce lubricating

mucus are often seen here

Mucosae (mucous membranes)-

epithelial membrane that line

body cavities open to exterior

Simple epithelia

Pseudostratified

columnar epithelium- all

cells rest on basement

membrane but some are

shorter than others

giving it the false

appearance that it is

stratified- main

function is absorption

and secretion

Stratified epithelia Stratified squamous- most

common stratified in the

body- several layers of

cells- at the free edge are

squamous but at basement are

cuboidal or columnar - found

where abuse or friction

occurs (mouth, esophagus,

skin)

Stratified epithelia

Stratified cuboidal- usually has just

2 cell layers with at least the

surface cells being cuboidal in shape

Stratified columnar- columnar cells

but base cells vary in size or shape

Both are fairly rare in body being

found mainly in ducts of large glands

Stratified epithelia

Transitional epithelium- highly modified

squamous epithelium that forms the lining of

only a few organs (bladder, ureters, and part

of urethra due to considerable stretching)-

cells of the basal layer are cuboidal or

columnar; near free surface vary in

appearance- when organ is stretched the cells

become squamous like

Glandular epithelium

Gland- consists of one or more cells that

make and secrete particular products

Secretion- product secreted that typically

contain protein molecules in an aqueous

(water-based) fluid

2 major types of glands Both develop from epithelial sheets

Endocrine glands- lose their connection the surface

(duct)- secretions (hormones) diffuse directly into

the blood vessels that weave through the gland-

(thyroid, adrenals, pituitary)

Exocrine glands- retain ducts and secretions empty

through ducts into epithelial surface- (sweat and

oil, liver)

Connective tissue

● Connects body parts

● Found everywhere in the body

● Most abundant and widely distributed of the

tissue types

Common characteristics of connective tissue

● Variations in blood supply

○ Most are well vascularized

○ Exceptions: tendons and ligaments have

poor blood supply, cartilages are

avascular

■ Consequently takes longer to heal

Common characteristics

Extracellular matrix- many different types of cells

plus varying amounts of a nonliving substance found

outside the cells

Produced by the connective tissue cells then secreted

to their exterior

Can be liquid, semi-solid/gel-like, or solid

Because of this connective tissue is able to bear

weight to withstand stretching or other abuses

characteristics

Fibers- various types and amounts are

deposited in and form part of the matrix

material

Collagen (White) fibers

Elastic (yellow) fibers

Reticular (fine collagen) fibers

characteristics

Performs many functions:

● Protecting

● Supporting

● Binding together other body tissues

Types of connective tissue

Bone- (osseous) composed of bone cells siting

in cavities (lacunae) and surrounded by

layers of very hard matrix that contains

calcium salts in addition to large numbers of

collagen fibers

Exceptional ability to protect and support

cartilage

less hard and more flexible than bone

Found only a few places in the body

Hyaline- most widespread and has abundant

collagen fibers hidden in a matrix with a blue-

white appearance

● Forms supporting structures of the larynx,

attaches ribs to breast bone, covers ends of

bones where they form joints

cartilage

Elastic- found where structure with

elasticity is desired

Supports the external ear

Fibrocartilage- highly compressible- between

the vertebrae of the spinal column

Dense connective tissue (Dense fibrous tissue)

Collagen fibers are in matrix element- between collagen are

rows of fibroblasts

Forms strong, ropelike structures such as tendons and

ligaments; also lower layers of the skin

Tendons- attach skeletal muscles to bones

Ligaments- connect bones to bones at joints- more stretchy

and contain more elastic fibers

Loose connective tissue

Softer and have more cells/fewer fibers than

any other connective tissue except blood

Areolar tissue- wraps organs and protects

them

● edema= body region is inflamed areolar

tissue soaks up the excess fluid and swells

Loose connective tissue

Adipose tissue- commonly called fat- tissue

where cells predominate- cells filled with

oil

Forms subcutaneous tissue beneath the skin

to insulate the body- also surrounds some

organs

Reticular connective tissue

Consists of a delicate network of reticular

fibers with reticular cells

Limited at certain sites

Forms the stroma- internal supporting

framework which supports many free blood

cells in lymphoid organs

blood

Vascular tissue

Consists of blood cells surrounded by

nonliving, fluid matrix called blood plasma

Fibers are soluble protein molecules that are

visible only when blood clotting

Muscle tissue

Highly specialized to contract or shorten to

produce movement

Types:

● Skeletal- striated, voluntary, multinucleate

● Cardiac- only in heart, striated, uninucleate,

involuntary

● Smooth- no striations- uninucleate, stomach,

bladder, blood vessels, involuntary

Nervous tissue

Commonly called neurons- receive and conduct

impulses from one part to another

(irritability and conductivity are the 2

major functional characteristics)

Make up the nervous system (brain, spinal

cord, and nerves)

Name these structures!

A:

Fibroblas

ts

B:

Collagen

fibers

C:

Elastin

Fibers

Tendon

Stratified

Squamous

Adipose

tissue

Transitional

epithelium

Simple

columnar

Reticular

fibers

Bone tissue

osseous

Hyaline

cartilage

Simple

cuboidal

blood

Skeletal muscle

tissue

Elastic cartilage

Pseudostratified columnar epithelium

Nervous

tisse

Smoothe

muscle

tissue

Stratified

cuboidal

epithelium

Reticular tissue

fibrocartilage

ligament

Simple squamous

Cardiac

muscle

Stratified

columnar

Areolar

tissue