TISSUE

The Living Fabric

Pages 118-124

Section 1

Epithelial Tissue

Epithelial tissue (epithelium) Sheet of cells that covers a body surface or

lines a body cavity. Two types:

Covering and lining epithelium Outer layer of skin, lines open cavities

Glandular epithelium Fashions the glands of the body

Epithelial Tissue

Epithelium has many functions: Protections Absorption Filtration Excretion Secretion Sensory reception

Classification of Epithelia

Each epithelium is given two names First - # of layers

Simple and stratified Simple epithelia – single cell layer (found

where absorbtion and filtration occur Stratified epithelia – two or more layers

(high abrasion areas)

Classification of Epithelia

Second name – shape of cells Three common shapes

Squamous cells – flattened and scalelike Cuboidal cells – boxlike Columnar cells - tall and column shaped

Simple Epithelia

Simple Squamous Flattened laterally, cytoplasm is sparse Look like a fried egg

Allows passage of materials by diffusion and filtration

Areas where protection is not important Kidneys, air sacs of lungs, lining of heart

Two names that reflect their location Endothelium – ‘inner covering’ Mesothelium – covering organs

Simple Cuboidal Epithelium

Consists of a single layer of cells as tall as they are wide, spherical central nuclei Functions:

Secretion Absorption

Location Ovary surface, ducts and secretory protions of

small glands

Simple Columnar Epithelium Single layer of tall closely packed cells,

round/oval nuclei Some contain cilia which help move

substances through pathway Function:

Absorption, secretion of mucus Location:

Lines most of the digestive tract, gallbladder

Stratified Epithelia

Two or more layers of cells More durable Regenerate from below Role is protection

Stratified Epithelia

Stratified Squamous Epithelium Thick membrane composed of several

layers Function:

Protects underlying tissues in areas subjected to abrasion

Locations: Moist linings of mouth and esophagus

Stratified Epithelia

Stratified Cuboidal and Columnar Epithelia Cuboildal

Quite rare in the body Mostly found in ducts of larger glands

Columnar Small amounts are found in pharynx, and lining

of some glandular ducts

Connective Tissue

Connective Tissue

Found everywhere in the body Most abundent and widely distributed of

the primary tissues Four main classes

Connective tissue proper Catilage Bone tissue blood

Connective Tissue

Functions: Binding and support Protection Insulation Transportation of substances within the

body

Common Characteristics

Despite their diverse functions, they have many common characteristics Common origin

All connective tissue comes from mesenchyme (embryotic tissue)

Degrees of vascularity Have many degrees of vascularity (contain

vessels) Extracellular Matrix

Seperates the living cells of the tissue Because of matrix connective tissue can bear

weight

Structural Elements of Connective Tissue

Connective Tissues have 3 main elements: Ground substance Fibers Cells

Ground Substance

Unstructured material that fills the space between the cells and contains the fibers Composed of:

Interstitial fluid Cell adhesion proteins

Acts like glue, helps attach themselves to matrix elements

Proteoglycans Holds large amounts of fluid and functions

as a molecular sieve, or medium for nutrients to diffuse between blood capliaries and cells

Fibers

Provide support Three main types of fibers:

Collagen Elastic Reticular fibers

Fibers

Collagen fibers By far the strongest and most abundant Constructed mainly of collagen

Secreted into the extracellular space Cross-linked fibrils

Because of this cross-linked pattern they are very strong

Have a glistening white appearance – also called white fibers

Elastic Fibers

Long, thin fibers that form branching networks in the extracellular matrix Contain rubber-like protein elastin

Allows them to stretch and recoil Found where elasticity is needed

Skin, lungs, and blood vessel walls Sometimes called yellow fibers

Reticular Fibers

Short, fine, collagenous fibers Branch extensively, forming delicate

networks that surround small blood vessels and support soft tissue

Cells

Each connective tissue has a fundamental cell type Blast – ‘bud’ or ‘sprout’, means ‘forming’ Primary blast cell types by connective

tissue class are: Connective tissue proper (fibroblast) Cartilage (Chondroblast) Bone (osteoblast) Blood (hematopoietic stem cell)

Is no located in its tissue (blood)

These cells make the matrix of their connective tissue.

Connective Tissue Proper

Has two subclasses: Loose connective tissues Dense connective tissues

Except for bone and blood, all mature connective tissues belong to this class

Loose Connective Tissue

Areolar Connective Tissue Gel-like matrix with three fiber types

Fibroblasts, macrophages, mast cells, and some white blood cells

Function Wraps and cushions organs Plays important role in inflammation (holds

fluids) Location

Widely distributed under epithelia of body Surrounds capillaries

Loose Connective Tissue

Adipose (fat) tissue Closely packed fat cells Have nucleus pushed to side by large fat droplet

Function: Provides reserve food fuel Insulates against heat loss Supports and protects glands

Location: Under skin Around kidneys and eyeballs Within abdomen and breasts

Loose Connective Tissue

Reticular Connective Tissue Network of reticular fibers in a typical loose

ground substance; lie on the network Function:

Fibers from soft internal skeleton that supports other cell types of cells including white blood cells

Location: Lymphoid organs

Pictures

Adipose Tissue

Areolar Tissue

Reticular Tissue

Cartilage

Stands up to both tension and compression Has qualities imtermediate between dense

connective tissue and bone Tough but flexible Made up of 80% water Gets nutrients from blood vessels in

membranes Three varieties of cartilage:

Hyaline cartilage Elastic cartilage fibrocartilage

Hyaline Cartilage

Most abundent Contains large amounts of collagen, not

apparent in matrix Appears glassy (hyalin = glass)

Provides support with some pliability Absorb compression at joints Supports tip of nose, connects ribs to

sternum Supports respiratory pathways

Elastic Cartilage

Description: Similar to hyaline cartilage, but more

elastic fibers in matrix Function:

Maintains the shape of structure Allows great flexibility

Location: Supports the external ear

Fibrocartilage

Description: Less firm than hyaline cartilage Thick collagen fibers

Function: Tensile strength with the ability to absorb

commpressive shock Location:

Intervertebral discs Discs of knees

Pictures

Hyaline Cartilage

Fibrocartilage

Elastic Cartilage

Bone

Rocklike hardness osseous tissue, has an exceptional ability to support and protect body structures Provide cavity for fat storage Synthesis of blood cells Inorganic calcium salts Seen as closely packed structural units

called osteons, form rings

Blood

Blood Fluid within blood vessels Does not connect things to give mechanical support Classified as connective tissue because it developes

from mesynchyme and consists of blood cells surrounded by a nonliving matrix called blood plasma

Majority is red blood cells ‘fibers’ are soluble protein molecules that precipitate,

forming large fiberlike structures during clotting Transport vehicle

Carries nutrients, waste and respiratory gases throughout body

Pictures

Bone Tissue

Red Blood Tissue

White Blood Tissue

Nervous Tissue

Main component of nervous system Brain, spinal cord, nerves

Neurons Highly specialized nerve cells that generate

and conduct nerve impulses Branching cells – cell processes Transmit electrical eignals from sensory

receptors to effectors which control their activity

Muscle Tissue

Responsible for most types of body movements

Three kinds of muscle tissue: Skeletal Cardiac Smooth

Skeletal Muscle

Attached to bones of the skeleton Form the flesh of the body

When they contract they pull on bone or skin to produce movement

Long, cylindrical, many nuclei, obvious striations Voluntary movement, facial expression,

voluntary control

Cardiac Muscle

Found only in the wall of the heart Helps propel blood throughout body Branching, striated, generally

uninucleate

Smooth Muscle

No visible striations Walls of hallow organs

Digestive and urinary tract organs Works to squeeze substances through

these organs by alternated contracting and relaxing

Both smooth and cardiac muscles are involuntary muscle – we do not think about it when it is working

Steps of Tissue Repair

Repair occurs in two major ways: Regeneration

Replacement of destroyed tissue Fibrosis

Proliferation of fibrous connective tissue called scar tissue

Which of these occurs is based on: Type of tissue damaged Severity of the injury