CHAPTER 4

Tissues are collections of cells and cell products that perform specific, limited functions

Histology = study of tissues There are 4 types of tissues

1. Epithelial

2. Connective

3. Muscle

4. Neural

Covers body surfaces, lines cavities and tubular structures Includes epithelia and glands

Characteristics

Cells are tightly packed together

Free (apical) surface exposed to environment

Attached to underlying connective tissue (basement membrane)

Avascular (no blood supply)

Continually replaced at exposed surface

1. Physical protection (abrasion, dehydration, destruction) 2. Control permeability 3. Provide sensation 4. Produce specialized secretions Exocrine= secretions are discharged onto the surface o Milk, sweat, enzymes entering the digestive tract

Endocrine = secretions are discharged into tissue fluid and blood o hormones

1. Cell layers Simple epithelium: single layer of cells Stratified epithelium: several layers of cells Pseudostratified epithelium: appears to be stratified but is not

2. Cell shapes Squamous – thin and flat Cuboidal – cube shaped Columnar – tall, slender rectangles

1. Simple Squamous ▪ Locations: Lining of the heart , blood vessels, kidney tubules,

inner lining of cornea, alveoli of lungs

▪ Functions: Reduce friction, controls vessel permeability, adsorption and secretion

2. Simple Cuboidal ▪ Locations: Sweat glands, ducts, kidney tubules, thyroid gland

▪ Functions: Limited protection, absorption and secretion

3. Simple columnar ▪ Locations: Lining of the stomach, intestines, gall bladder,

uterine tubes, collecting ducts of kidney

▪ Functions: protection, absorption and secretion

▪ Other: : Cells are very long and often have cilia

4. Stratified Squamous ▪ Locations: surface of skin, lining of mouth, throat, esophagus,

rectum, anus and vagina

▪ Functions: Protection from abrasion, pathogens, and chemicals

5. Pseudostratified ciliated columnar ▪ Locations: lining of nasal cavity, trachea and bronchi and

portions of male reproductive tract

▪ Functions: Protection and secretion

6. Transitional ▪ Locations: bladder, renal pelvis, ureters ▪ Functions: permits expansion and recoil after stretching

Practice Identifying epithelial tissues

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Most diverse tissue of the body Highly vascular Never exposed to external environment Characteristics Specialized cells

Extracellular matrix (majority of tissue volume; determines function) ▪ Solid extracellular protein fibers

▪ Fluid extracellular ground substance (amorphous gel like substance composed of large carbohydrates and proteins)

1. Support and protection 2. Transportation of materials 3. Storage of energy reserves 4. Defense of the body

1. Connective Tissue Proper

a) Loose (underlying skin, fat)

b) Dense (tendons and ligaments)

2. Supporting Connective Tissues

a) Cartilage (solid rubbery matrix)

b) Bone (solid crystalline matrix)

3. Fluid Connective Tissues

a) Blood

b) Lymph

1. Loose Connective Tissue

More ground substance, less fibers

Mainly composed of fibroblasts

Locations: between other tissue and organs, beneath skin, digestive, respiratory and urinary tracts, between muscles, around blood vessels, nerves and joints

Functions: cushion, support, allows movement, defense against pathogens

1. Loose Connective Tissue

2. Adipose Tissue

Fibroblasts enlarge and store fat

Very little matrix

Locations: beneath the skin and around organs especially at sides, buttocks, breasts, around eyes and kidneys

Functions: padding, shocks insulates, stores energy

2. Adipose Tissue

3. Dense Connective Tissue

More fibers, less ground substance

Fibroblast matrix composed of parallel collagen fibers

Locations: between skeletal muscles (tendons) between bones (ligaments), covering skeletal muscles

Functions: firm attachment; conducts pull of muscle, reduces friction between muscles, stabilizes position of bones, helps prevent overexpansion of organs (bladder)

3. Dense Connective Tissue

Gel-type ground substance For shock absorption and protection No blood vessels Types of cartilage include

Hyaline cartilage

Elastic cartilage

Fibrous cartilage

1. Hyaline Cartilage

Most common

Location: between ribs and sternum, bone joints, trachea, bronchi and nasal septum

Function: Stiff but flexible support; Reduces friction between bones

2. Elastic Cartilage

Elastic fibers in addition to collagen

Locations: external ear and epiglottis

Functions: Supportive but very flexible

3. Fibrous Cartilage (fibrocartilage)

Strong collagen fibers in matrix

Locations: knees, pubic bones, intervertebral discs

Functions: Limits movement, prevents bone-to-bone contact, absorbs shock, reduces friction

Most rigid connective tissue Matrix composed of hard mineral salts deposited

around collagen fibers

Gives bone rigidity and elasticity

Bone cells (osteocytes) Periosteum (Covers bone surfaces)

Physical barriers Line internal spaces of organs and tubes that

open to the outside Line body cavities Different types of membranes\ Mucous

Serous

Cutaneous

Synovial

Meninges

Mucous = protection Line passages that have external connections

Lining of digestive, respiratory, urinary and reproductive tracts

Epithelial surfaces are moist to reduce friction and help absorption and excretion

Line cavities not open to outside Are thin but strong Have fluid to reduce friction Three serous membranes

Pleura – lungs

Peritoneum – abdomen

Pericardium - heart

Outer covering of body Skin Thick, waterproof and dry Stratified keratinized squamous epithelium

Line freely movable joint cavities Secrete synovial fluid into joint cavity –

provides lubrication Protects the end of bones Lacks a true epithelium

Specialized for contraction Produces all body movement Three types

Skeletal

Cardiac

Smooth

1. Skeletal Muscle

Specialized for contraction

Moves and stabilizes bone

Guards entrances and exits

Generates heat

Protects organs

Cells are long, cylindrical, striated and multinucleate

2. Cardiac Muscle

Found only in the heart

Circulates blood

Maintains blood pressure

Cells are short, branched and striated usually with a single nucleus

3. Smooth muscle

Walls of hollow, contracting organs (blood vessels digestive, respiratory, urinary and reproductive tracts)

Moves food, urine and other secretions

Controls diameter of respiratory passageways and blood vessels

Cells are short, spindle-shaped and non-striated with a single central nucleus

Specialized for conducting electrical impulses Rapidly senses internal or external environment Processes information and controls responses Concentrated in the central nervous system

Brain and spinal cord

Two kinds of neural cells

Neurons

Neuroglia

A.k.a nerve cells Perform electrical communication Parts of a neuron

Cell body – contains the nucleus

Dendrites – receive incoming signals

Axon (nerve fiber) – long thin extension of the cell body which carries outgoing electrical signals to the effector

Supporting cells Repair and supply nutrients to neurons

Tissues respond to injury to maintain homeostasis

Inflammatory response The tissue’s first response to injury Signs and symptoms of the inflammatory response

Swelling, redness, heat, pain

Can be triggered by

Trauma (physical injury) or infection

Fibroblasts produce dense network of collagen fibers (scar tissue)

Most successful in…

epithelia, connective tissues and smooth muscle

Least successful in…

Neural tissue, cardiac muscle

Speed and efficiency of tissue repair decrease with age due to

Slower rate of energy consumption (metabolism)

Hormonal alterations

Reduced physical activity

Osteoporosis – age related reduction in bone strength of women

Tissue ID

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