Chapter 3

Body Tissues

Body Tissues

• Human body starts out as one cell• Cell division occurs to create millions of cells• Cellular Specialization results• Anytime you have a group of cells working

together for the same purpose TISSUES result.

Four Main Tissue Types

1. Connective- Support2. Nervous- Control3. Muscle- Movement4. Epithelium- Covering

Tissues

• Most organs are composed of several tissue types.

• The Type of tissue will determine the function of the organ.

Epithelial Tissue

• The lining, covering, and glandular tissue of the body.

• Covers all free body surfaces and contains versatile cells.

• Nearly all substances given off or received by the body must pass through the epithelium.

Epithelial Functions

1. Protection2. Absorption3. Filtration4. SecretionExamples: Epithelium of the skin-protects

against bacterial and chemical damage.-Epithelium that lines the digestive tract absorbs

food into the body.

Characteristics of Epithelium

• Cells fit closely together and form continuous sheets.

• The membranes always have one free (unattached) surface or edge. This Apical Surface is exposed to the body’s exterior or tot eh cavity of an internal organ

Characteristics Cont.

• The lower surface rest on a basement membrane

• Epithelial tissues have no blood supply of their own(avascular) and depend on diffusion from capillaries to provide oxygen and food.

• If well nourished, epithelial cells will regenerate easily.

Classification of Epithelium

• Given two names: the 1st= number of cell layers, 2nd= shape of the cells

Number of cells1) Simple= one layer of cells2) Stratified= more than one cell layer

Classification Cont.

Shapes of Cells1. Squamous- flattened like fish scales 2. Cuboidal- cube shaped like dice3. Columnar- cells shaped like columns

* The terms describing the shape and the arrangement are then combined to describe the epithelium completely.

Simple Epithelia

• The simple epithelia are most concerned with; -absorption- secretion- filtration

**because they are thin protection is not a function**

Simple Squamous Epithelium

• A single layer of thin squamous cells.• Cells fit closely together• Forms membranes where filtration or

exchange of substances by rapid diffusion occurs.

• Found in the following areas:-air sacs of the lungs, forms walls of capillaries, forms serous membranes

Simple Cuboidal Epithelium

• One layer of cuboidal cells• Forms:

- glands and their ducts(salivary glands and the pancreas), walls of kidney tubules, covers the surface of the ovaries,

Simple Columnar Epithelium

• Made up of a single layer of tall cells that fit closely together.

• Forms;- Goblet Cells(produce lubricating mucus), lines the entire length of the digestive system

Pseudostratified Columnar Epithelium

• Pseudo=false or fake• The appearance of the cells arrangement leads

to the look of multiple layers when in fact there is only one.

• Function; absorption and secretion• Ciliated version lines the respiratory tract,

goblet cells produce mucus to trap dust and debris while the cilia push the mucus away from the lungs

Stratified Epithelium

• Consists of two or more cell layers• Considerably more durable then simple

epithelia• Functions to Protect

Stratified Squamous Epithelium

• Most common stratified epithelium in the body.

• Consists of several layers• Found in sites that receive a good amount of

abuse or friction like the esophagus, the mouth, and the outer portion of the skin

Stratified Cuboidal Epithelium

• Two layers with the cells being cuboidal in shape

• Very rare along with stratified columnar epithelium

Stratified Columnar Epithelium

• Very rare found only in the ducts of large glands

Transitional Epithelium

• Highly modified, stratified squamous epithelium that forms the lining of only a few organs- the urinary bladder, the ureters, and the urethra.

• All of these organs are a part of the urinary system and subject to considerable stretching.

• The ability of transitional cells to slide past one another and to change shape allows for the urinary system to function properly

Glandular Epithelium

• A gland consists of one or more cells that make and secrete a particular product.

• This product is called an secretion.• Two major types of glands are formed from

epithelial sheets.1. Endocrine Glands2. Exocrine Glands

Endocrine Glands

• Lose their connection to the duct• Their secretions(all hormones) diffuse directly

onto the blood vessels that weave through the gland.

• Examples include; thyroid, adrenals, and pituitary

Exocrine Glands

• Retain their ducts• Secretions empty through the ducts to the

epithelial surface• Include; sweat and oil glands, liver and

pancreas

Connective Tissue

• Connects body parts• Found everywhere in the body• It is the most abundant and widely distributed

of the tissue types.

Common Characteristics of Connective Tissue

• Variations in blood supply (well vascularized)Exceptions: tendons and ligaments poor

blood supply, cartilages are avascular.• Extracellular Matrix-made up of many types of

cells and a non-living substance found outside those cells

Extracellular Matrix

• Makes connective tissue different then all other tissues.

• The matrix is produced by the connective tissue cells and secreted to there exterior.

• Matrix may be liquid, semi-solid, gel-like, or very hard

Extracellular Matrix

• Because of the matrix, connective tissue can bear weight, withstand stretching, and other abuses that no other tissue could withstand.

• One extreme-fat with lots of cells and a soft matrix

• Another extreme-bone with few cells and hard matrix

Extracellular Matrix

• Various types and amounts of fibers are deposited in and form a part of the matrix.– Examples: Collagen Fibers ( white)– Elastic Fibers (yellow)– Reticular Fibers ( Fine collagen)

Connective Tissue Functions

• Protecting, Supporting, and Binding together other body tissues.

Types of Connective Tissues

• Bone• Cartilage (3)• Dense connective tissue (2)• Loose connective tissue (2)• Adipose tissue• Reticular connective tissue• Blood

Muscle Tissue

• Highly specialized to CONTRACT AND SHORTEN.

Types of Muscle Tissue

• Skeletal Muscle• Cardiac Muscle• Smooth Muscle

Skeletal Muscle

Cardiac Muscle

Smooth Muscle

Nervous Tissue

• Composed of cells called neurons• All neurons receive and conduct

electrochemical impulses from one part of the body to another

Nervous Tissue Function

• Irritability and conductivity are two major functions of nervous tissue.

Neuron Structure

• Very unique• Cytoplasm stretches out into long extensions

that can carry impulses over large areas in the body.

• Work with a group of supporting cells that:– Insulate– Support– Protect the delicate structures of the neurons

Tissue Repair

• The body has many protective features put into place to help prevent damage or injury.

• When injury does occur, it stimulates the body’s inflammatory and immune responses and the healing immediately begins.

Inflammation

• A nonspecific response to try and prevent further injury.

Immune Response

• An extremely specific response that mounts a vigorous attack against a recognized invader.

2 Major Ways That Tissue Repair Occurs

1. Regeneration-the replacement of destroyed tissue by the same kind of cell

2. Fibrosis- repair by dense connective tissue or the formation of scar tissue

Tissue Repair

• The type of tissue repair depends on:

1. The type of tissue damaged

2. The severity of the injury

**Clean cuts(incisions) heal more quickly than ragged tears(lacerations).

Tissue Injury Events

1. Capillaries become very permeable which allows fluids rich in clotting proteins to seep into the injured area.

2. A clot is constructed which stops the bleeding and holds the edges of the wound together.

Events

3. Clot walls off the injured area preventing bacteria and other harmful substances from getting into the tissue.

4. The clot that is exposed to air will dry and form a scab.

5. Granulation Tissue Forms

Events

6. Granulation tissue is a delicate pink tissue composed largely of capillaries that grow into the damaged area from surrounding healthy blood vessels.

7. The clot is disposed of and the connective tissue synthesizes collagen fibers(scar tissue) to form

Events

8. Surface epithelium begins to regenerate.

9. Surface epithelium will cover the scar.

**the ability for different tissues to regenerate varies widely**

Regeneration

• Easily: skin epidermis and mucous membranes, fibrous connective tissue, and bone

• Poorly: skeletal muscle

• Not at all: cardiac muscle and nervous tissue-replaced only by scar tissue

Developmental Aspects of Cells and Tissues

Developmental

• Neoplasm- an abnormal mass of proliferating cells . – Benign– Malignant

Developmental

• Hyperplasia-occurs when certain body tissues enlarge because there is some local irritant or condition that stimulates cells

Developmental

• Atrophy-decrease in size- can occur in a certain organ or body area that loses its normal stimulation