Chapter 4

Tissue: The Living Fabric

G.R. Pitts, Ph.D, J.R. Schiller, Ph.D. & James F. Thompson, Ph.D.

General Tissues - groups of cells with similar basic

structures which cooperate to perform a related function

Four basic types of tissues Epithelial – linings for protection, coordination,

synthesis, absorption, elimination

Connective – support

Muscle – for movement muscle tissue is a highly specialized connective tissue

Nervous – for control and coordination nervous tissue is a highly specialized epithelial tissue

Epithelial Tissue Characteristics1. Cellularity - densely packed2. Polarity

apical surface basal surface (or basolateral)

3. Specialized contacts - tight junctions and desmosomes

4. Supported by connective tissue basal lamina (epithelial “glue”) reticular lamina (connective tissue “glue”) basement membrane - reticular and basal

laminae together

5. Innervated but avascular (no direct blood supply)

6. Regeneration – high capacity for regeneration

Simple

Stratified

Classifying Epithelial Tissues By number of cell

layers

Pseudostratified epithelium (from the respiratory tree) appears stratified, but actually is a single layer of cells of varying heights; each cell touches the basement membrane

Classifying Epithelial Tissues

By cell shape

Transitional

Squamous

Columnar

Cuboidal

Glandular Epithelial Tissues functions in secretion – a gland may be one cell

or a group of specialized cells two major types

exocrine glands have ducts leading to body surfaces

various products are synthesized and stored for release

secretions are secreted into the duct system e.g., sweat glands, salivary glands, etc.

endocrine glands are ductless hormones are synthesized and stored for release hormones are secreted into the tissue fluid and

then diffuse into the blood stream e.g., thyroid and parathyroid glands

Exocrine Gland Classification

Unicellular glands single cell glands goblet cells

Exocrine Gland Classification

Multicellular glands Structurally classified

by duct configuration and by the shape of the secretory units

simple glands have a single duct

compound glands have branched ducts

Merocrine glands Exocytosis

Holocrine glands Cell rupture

Connective Tissue Characteristics1.Two basic components

Cells – fewer, rarely touching, surrounded by a matrix immature forms (-blasts) secrete the matrix and can still

divide once the matrix is secreted, the cells mature into -cytes

which have decreased cell divisions and secrete less matrix material

chondro- cartilage, osteo- bone, fibro – connective, etc.

Extracellular Matrix ground substance (gelatinous glycoproteins) structural fibers (fibrous proteins, e.g., collagen, elastin,

reticulin)

2.Common embryological origin (from mesoderm)

3. Innervated and Vascular (direct blood supply) Cartilage is the one exception with no capillary beds

Connective Tissue Matrix1. Ground Substance

supports cells, binds them together may be solid, fluid, or gel interstitial fluid

Glycoproteins called proteoglycans - large polysaccharide molecules bound to a protein core (like a bottle brush) Hyaluronic acid – gelatinous, separates cells, traps

extracellular fluid; lubricates joints; gives shape to eyeballs; fills body spaces

Chondroitin sulfate – capable of being mineralized; cartilage, bones, skin, blood vessels

Dermatin sulfate – harder; skin, tendons, blood vessels, heart valves

Keratin sulfate - still harder; bone, cartilage, cornea of the eyes

Connective Tissue Matrix2. Protein fibers are embedded in the ground substance

Used for structural support, adhesion, and to connect cells

Provide strength and support Collagen fibers

highly polymerized, gigantic molecules tough, moderate flexibility protein collagen - parallel bundles of fibers bone, cartilage, tendons, ligaments

Elastic fibers (elastin) branched; smaller, thinner fibers than collagen Very flexible and elastic but also strong can be stretched to 150% of its original length require special stains to be seen

Reticular fibers thin, less polymerized collagen fibers require special stains to be seen

Connective Tissue Proper areolar (loose fibrous) connective tissue adipose tissue reticular connective tissue dense (fibrous) regular connective

tissue dense (fibrous) irregular connective

tissue

Cartilage hyaline cartilage elastic cartilage fibrocartilage

Bone

Blood

Types of Connective Tissues

Classified by the characteristics of the matrix

Connective Tissue Types

Details covered in lab

Also see Table 4.1

Connective Tissue Diseases Many diseases

Most of them very rare

They may involve the joints but primarily affect other organs

Cause(s) of these diseases unknown

But in all of them, the immune system seems to be activated and causes damage to different organs in the body

Systemic Lupus Erythematosus Symptoms: skin rash, mild

arthritis, and generalized weakness or tiredness

Rarer symptoms: hair loss, mouth ulcers, headaches and poor circulation in the fingers

Serious complications of kidney, heart, and brain inflammation

9 times more likely in women

4 times more likely in African-Americans

http://www.niehs.nih.gov/health/topics/conditions/lupus/index.cfm

Marfan Syndrome

Genetic defect on chromosome 15 that encodes the fibrilin protein

Nervous Tissue Highly specialized

epithelial cells

Convert stimuli into electro-chemical signals for transfer of information

Structure cell body (soma) and

extensions dendrites (highly

branched) – carry incoming signal

axon (long, usually single strand) – carry outgoing signal

Muscle Tissue Characteristics a high degree of cellularity

cells contain contractile proteins

well vascularized

a highly specialized type of connective tissue

Classification of Muscle Tissues two types are StriatedStriated:

Skeletal muscle attached to bones multinucleate voluntary fibers are parallel and

cylindrical

Cardiac muscle most of the heart wall single nucleus (usually) involuntary branched cylinders

connected by intercalated discs

Classification of Muscle Tissues One type is non-striated

Smooth muscle located in the walls of

hollow organs:• blood vessels• digestive tract• airways• bladder

involuntary single nucleus spindle shaped

Epithelial Membranes

A particular Epithelium and its underlying Connective Tissue support

skin trachea

Cutaneous Membrane – The Skin

Mucous Membranes

Line body structures which open directly to the exterior

Viscous mucus secretions lubricate surfaces and provide a defensive barrier that traps particles and microbes

Line closed body cavities and their organs

Watery serous fluid lubricates the cavity and its organs

pleura – lungs

pericardium - heart

peritoneum - abdominal organs

parietal visceral

Serous Membranes

Tissue Injury & Repair1. Inflammation

redness swelling heat pain loss of function

2. Organization restores blood supply Blood clot replaced by

granulation tissue

3. Regeneration and Fibrosis Epithelium regenerates Fibrous conn. tissue

matures and contracts

Tissue Repair During development some cells lose their ability

to divide with specialization Some cells maintain the ability to replace others

Stem cells immature, undifferentiated cells hide in protected areas in skin/GI tract to replace

cells Tissue repair

new cells come from parenchyma (functioning portion) or stroma (connective tissue)

if parenchyma cells proliferate then repair nearly complete; if not, then we get scar tissue formation

fibroblasts will produce collagen and other matrix materials during fibrosis – a less functional tissue

Conditions Affecting Repair Nutrition

adequate protein in the diet for repair necessary vitamins and other nutrients

Blood circulation transport oxygen, nutrients, antibodies and other

defensive molecules and cells to the site WBCs remove debris which would otherwise

interfere with healing Age

young people heal faster and have less obvious scars

young people have a better nutritional status, a better blood supply, and a higher metabolism

Embryonic Germ Layers

We’ll see the embryonic tissues again in Chapter 28 next semester

End Chapter 4

Exam 1 covers Chapters 1-4

Connective Tissue Structure

Embryonic Structure