Body TissuesCh.3 (Part II)

Body Tissues Cells are specialized for particular functions Tissues

Groups of cells with similar structure and function

Four primary types Epithelium Connective tissue Nervous tissue Muscle

Body Tissues If we had to assign a single term to each primary

tissue type that would best describe its overall role, the terms would most likely be:

Covering (epithelium) Support (connective) Movement (muscle) Control (nervous)

However, these terms only reflect only a tiny fraction of the functions that each of these tissues perform.

1. Epithelial TissuesFound in different areas

Body coverings Body liningsGlandular tissue (forms glands in

body)

FunctionsProtectionAbsorptionFiltrationSecretion

Special Characteristics of Epithelium: Cells fit closely together (except for glandular) to

form connective sheets Tissue layer always has one free surface. This so

called “apical surface” is exposed to the body’s exterior or to the cavity of an internal organ.

The lower surface of epithelium is bound by a basement membrane (a structure less material secreted by cells)

Avascular (have no blood supply) so they depend on diffusion from the capillaries in the underlying connective tissue for food and oxygen

Regenerate easily if well nourished

Classification of Epithelium

1. Number of cell layers

Simple – one layer

Stratified – more than one layer

Figure 3.17a

Classification of Epithelium

2. Shape of cells Squamous – flattened

(like fish scales)

Cuboidal – cube-shaped (like dice)

Columnar – column-like (like columns…duh)

Figure 3.17b

Simple or Stratified…Simple

One layer of cells Most concerned with

absorption, secretion, and filtration

Because they are usually very thin, protection is not one of their specialties

Stratified Consist of two or

more cell layers More durable than

the simple epithelia

Function primarily to protect

Simple Epithelium 1. Simple squamous

Single layer of flat cells Usually forms membranes

where filtration or exchange of substances by rapid diffusion occurs. Lines body cavities Lines lungs and capillaries

Figure 3.18a

Simple Epithelium 2. Simple cuboidal

Single layer of cube-like cells

Common in glands and their ducts

Forms walls of kidney tubules

Covers the ovaries

Figure 3.18b

Simple Epithelium

3. Simple columnar Single layer of tall cells Often includes goblet

cells, which produce mucus

Lines the entire digestive tract from the stomach to the anus

Figure 3.18c

Simple Epithelium 4. Pseudostratified

Single layer, but some cells are shorter than others

Often looks like a double cell layer (false…hence the name pseudo)

Sometimes ciliated, such as in the respiratory tract

May function in absorption or secretion Figure 3.18d

Stratified Epithelium 1. Stratified squamous

Cells at the free edge are flattened but closer to the basement membrane, are cuboidal or columnar

Found as a protective covering where friction/abuse is common

Locations Skin Mouth Esophagus

Figure 3.18e

Stratified Epithelium 2. Stratified cuboidal

Two layers of cuboidal cells 3. 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 Epithelium 4. Transitional epithelium

Shape of cells depends upon the amount of stretching (near basement: typically columnar or cuboidal, at surface: varies)

Lines organs of the urinary system like the bladder, ureters, and part of the urethra where considerable amounts of stretching occur.

Figure 3.18f

Glandular Epithelium Gland – one or more cells that secretes a particular

product (secretion)

Two major gland types develop from epithelial sheets:

1. Endocrine gland Ductless (hormones diffuse directly into the blood vessels that

weave through the glands) Secretions are all hormones Examples of endocrine glands: thyroid, adrenals, and pituitary

2. Exocrine gland Empty through ducts to the epithelial surface Include sweat and oil glands, and liver and pancreas Are both internal and external

Connective Tissue Found everywhere in the body &

connects body parts Includes the most abundant and widely

distributed tissues Functions

Binds body tissues together Supports the body Provides protection

Connective Tissue Characteristics:

Variations in blood supply Some connective tissue types are well vascularized

(good blood supply) Some have poor blood supply or are avascular like

tendons and cartilages (these things heal slowly) Extracellular matrix

Connective tissues are made up of many different types of cells plus varying amounts of non-living material that surrounds living cells (called the extracellular matrix)

Extracellular MatrixMakes connective tissue different from any other

tissue.

Two main elements Ground substance – mostly water

along with adhesion proteins and polysaccharide molecules

FibersProduced by the cellsThree types

Collagen fibersElastic fibersReticular fibers

Extracellular Matrix Continued:

Allows connective tissue to form a soft packaging tissue around

other organs, to bear weight, and to withstand stretching and other

abuses, such as abrasionthat no other tissue could endure.

Connective Tissue Types: Bone (osseous tissue)

Composed of:Bone cells in lacunae

(cavities)Surrounded by a hard

matrix of calcium saltsLarge numbers of

collagen fibers Because of its

rocklike hardness, bone is used to protect and support the body Figure 3.19a

Connective Tissue Types:

Hyaline cartilage Most common cartilage

(cartilage is found only in a few places in the body…is less hard and more flexible than bone.)

Composed of: Abundant collagen fibers Rubbery matrix Blue-white appearance

Entire fetal skeleton is hyaline cartilage (turns to bone by birth)!

Also forms the supporting structure of the larynx (voicebox), attaches ribs to the breastbone, and covers the ends of bones where they form joints.

Figure 3.19b

Connective Tissue Types: Elastic cartilage

Provides elasticity Example: supports the external ear

Connective Tissue Types:

Fibrocartilage Highly compressible Example: forms

cushion-like discs between vertebrae

Figure 3.19c

Connective Tissue Types: Dense connective tissue

Main matrix element is collagen fibers

Cells are fibroblasts (fiber forming cells)

Forms strong ropelike structures (like the examples listed below)

Examples Tendon – attach muscle to

bone Ligaments – attach bone to

boneFigure 3.19d

Connective Tissue Types: Areolar connective

tissue Most widely distributed

connective tissue Soft, pliable

“cobwebby” tissue that cushions and protects the body organs

Helps hold internal organs together and in their proper positions

Contains all fiber types Can soak up excess

fluid Figure 3.19e

Figure 3.19f

Connective Tissue Types: Adipose tissue:

Commonly called fat! Matrix is an areolar

tissue in which fat cells predominate

Many cells contain large lipid deposits

Functions Insulates the bodyProtects some organsServes as a site of

fuel storage

Connective Tissue Types:Reticular connective

tissueDelicate network of

interwoven fibersForms stroma

(internal supporting network) of lymphoid organsLymph nodesSpleenBone marrow

Figure 3.19g

Connective Tissue Types: Blood (vascular tissue)

Blood cells surrounded by fluid matrix (called plasma)

Fibers are visible during clotting

Functions as the transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases, and many other substances throughout the body. Figure 3.19h

Muscle Tissue Function is to produce movement Three types

1. Skeletal muscle2. Cardiac muscle3. Smooth muscle

Muscle Tissue Types: 1. Skeletal muscle

Can be controlled voluntarily

Form the muscular system

Cells attach to connective tissue

Cells are striated (striped)

Cells have more than one nucleus

Figure 3.20a

Muscle Tissue Types 2. Cardiac muscle

Found only in the heart Function is to pump blood

(involuntary) Cells attached to other

cardiac muscle cells at intercalated disks (have gap junctions …remember this mean info can pass freely from cell to cell….)

Cells are striated One nucleus per cell Under involuntary control

Figure 3.20b

Muscle Tissue Types 3. Smooth muscle

AKA: visceral muscle Involuntary muscle Surrounds hollow

organs Spindle-shaped

(pointed at each end) Attached to other

smooth muscle cells No visible striations

(hence the name smooth)

One nucleus per cellFigure 3.20c

Nervous Tissue Neurons and nerve

support cells Function is to send

impulses to other areas of the body Irritability Conductivity

Figure 3.21

Tissue Repair (Wound Healing)

Tissue repair occurs in two major ways…

1. Regeneration Replacement of destroyed tissue by the same kind of

cells 2. Fibrosis

Repair by dense fibrous connective tissue (scar tissue is formed)

Determination of method Type of tissue damaged Severity of the injury

Tissue injury sets a series of events into motion…

1. Capillaries become very permeableA. Introduce clotting proteinsB. Wall off injured area

2. Formation of granulation tissue3. Regeneration of surface epithelium

Regeneration of Tissues

Tissues that regenerate easily Epithelial tissue Fibrous connective tissue 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

Read about Homeostatic Imbalance on pg. 98 and make notes….