CH. 2 HISTOLOGY

1. Histology - study of tissue.

2. Tissue - group of similar cells that perform a certain job.

3. There are 4 basic types of tissue.a. epithelial b. connectivec. muscled. nerve

4. Epithelial tissuea. location* widespread - covers and lines body surfaces including hollow organs and body cavities.

b. function* protective barrier* absorbs and secretes materials into the blood

c. characteristics* cells are close together, little intercellular material- effective protective barriers in skin and mouth* lacks blood vessels

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* reproduce rapidly- injuries are likely to heal rapidly as new cells replace lost or damaged ones

d. classification* simple - one layer of cells* stratified - 3 or more layers of cells* squamous - appear flat, similar to fish scales* cuboidal - small cubes* columnar - taller than they are wide

e. Types1) simple squamous epithelium - consists of a single layer of thin, flattened scale-like cells

* substances pass through easilyeg. Page 52 lab book

- lines the air sacs of lungs where oxygen and carbon dioxide are exchanged. page 424 lab.

- lines the insides of blood vessels and lymphatic vessels

- covers the membranes that line body cavities

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2). stratified squamous epithelium - consists of many layers of cells, only the top layer is flat.- Page 54

* located in areas exposed to wear and tear such as:

- skin, mouth, throat

3) simple cuboidal epithelium - single layer of cube-shaped cells.

- Page 53 * important in secretion, lines glands and ducts of some glands

- salivary, thyroid gland, panceas, and liver.

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4) simple columnar epithelium - cells that are longer than they are wide

- Page 53

* thickness provides protection

* located in linings of stomach and intestines

* microvilli - cylindrical minute processes that extend from columnar cells to increase surface area and aid substances being absorbed.

* goblet cells - flask-shaped cells scattered among the columnar cells that secrete a protective fluid

on the cells.

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5. Connective Tissue a. location* most abundant type of tissue by weight

b. function* binds structures together- muscle to muscle- muscle to bone- bone to bone* stores fat* transports (blood) substance throughout the body

c. characteristics* farther apart than epithelial cells and they have an abundance of intercellular material called matrix between cells

- matrix consists of fibers whose consistency varies from fluid to semisolid to solid.

- matrix of blood is fluid - no fibers except when it clots

* connective tissue cells are able to reproduce

* good blood supply and well nourished5

e. types of connective tissue

1) loose (areolar) connective tissue - one of the most widely distributed connective tissues in the body. Page 59 lab book

* loose - stretchable

* areolar - bubble appearance when pulled apart

* function - acts like an elastic glue that connects the skin to underlying tissue

* location- upper dermis of skin, around blood vessels, nerves, & organs.

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2) adipose tissue - large ring-shaped fat cells* 18% of weight of males* 28% of weight of females

* function - protective cushion for joints and some organs, such as kidneys

- storage area for excess food

- insulating material to conserve body heat

* location- found where areolar connective tissue is found, around the kidneys & heart, behind the eyeball.

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3) elastic cartilage - contains large numbers of very fine elastic fibers * Page 61 lab book

* chondrocyte - cartilage cell found in small chambers

- lack a direct blood flow so nutrients reach by diffusion from surrounding blood vessles

- injuries repair slowly because of insufficient nutrient delivery

* function- provides strength, elasticity, & maintains shape of organs.

* location- epiglottis of the larynx, external part of the ear, & the auditory tubes.

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4) bone - most rigid of connective tissue, hardness is due to mineral salts embedded in the intercellular material.

* osteocytes - bone cells* function- support and protection- forms blood cells- stores inorganic salts

* location- skeleton

5) blood - most unusual connective tisue because of the liquid state of the intercellular material.

* plasma - liquid straw-colored intercellular material

* cells - red, white, platelets

* function- transports gases, nutrients, & waste products,

- regulates body temperature9

6. Muscle tissue - 3 types, each is named for its location

* function of each each type is movement

a. skeletal muscle - attaches to bones, voluntary & striated. * voluntary - controlled by conscious effort

* cells (muscle fibers) are long and threadlike, with alternating light and dark cross-markings called

striations. * each fiber has many nuclei* responsible for movement of head, trunk, and limbs, facial expressions,writing, talking, singing, chewing, swallowing, and breathing.

b. visceral (smooth) - found in walls of viscera (hollow organs) such as urinary bladder, uterus, stomach, and blood vessels. * called smooth because it lacks striations. * involuntary - is not controlled by conscious effort* cells are shorter than skeletal* each cell has 1 centrally located nucleus* responsible for moving food through the digestive tube, constricting blood vessels, and emptying the urinary bladder.

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c. cardiac - wall of the heart

* striated, involuntary cells* cells are interconnected in complex networks* each cells has a single nucleus* intercalated disk are dark bands found where cells connect to each other* responsible for pumping the blood through the heart chambers and into certain blood vessels.

7. Nerve tissue - found in the brain, spinal cord and peripheral nerves.

a. neuron - basic cells of this tissue* transmit nerve impulses to other neurons or to muscles or glands.

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b. neurolglial cells - support and bind the components of nervous tissue together, carry on phagocytosis, and supply nutrients to neurons by connecting them to blood vessels.

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