CELLS AND TISSUES

Human Anatomy

Ch. 3

7/5/2016

I. Cells

A. Basic structural units of life

1. cells contain 4 main elements

a. C, H, O & N

2. other common elements also found

a. Fe, Ca, Na, K

b. may be found as electrolytes

3. Cells contain about 60% water

4. Cells are bathed in interstitial fluid

a. site of tissue-blood material exchange

5. Cells vary in size, shape & function

a. 2μm – 1+ m long

6. Organelles carry out various jobs w/in cells

a. ex: nucleus is the control center,

mitochondria carry on cellular respiration

7. Cells reproduce by mitosis

a. gametes form by meiosis

II. Body Tissues

A. Epithelium – lining, covering & glandular tissues(“Epithe-” = laid on, covering)

1. Functions

a. protection

b. absorption

c. filtration

d. secretion

2. Anatomy

a. cells fitted tightly together as sheets

1) except glandular

b. 1 unattached apical surface

1) exposed to exterior or internal organ cavities

c. lower surface rests on a basement membrane

d. avascular (a- = not; vascular = vessel)

1) lacks own blood supply

2) diffuses to/from tissues below

e. regenerate easily

3. Categories

a. Simple – 1 layer of cells

1) used to absorb, secrete or filter

2) Simple squamous – scale-like

a) ex: alveoli, capillaries

3) Simple cuboidal – box-like

a) form glands, ducts, surfaces

b) ex: salivary glands, ovary surface

4) Simple columnar – pillar-shaped

a) often produce mucus

b) ex: digestive tract mucosae (lining)

5) Pseudostratified columnar – cells are different

heights, appearing layered

a) absorb & secrete

b) ex: respiratory tract lining

b. Stratified - more than 1 cell layer

1) named for cell type at apical surface

2) function = protection

3) Stratified squamous (most common)

a) in areas of abuse/friction

b) ex: esophagus, epidermis

4) Stratified cuboidal

a) limited in body

b) ex: sweat glands, pharynx

5) Stratified columnar

a) limited in body

b) ex: male urethra

6) Transitional

a) can stretch, slide, change shapes

b) ex: lining of urinary bladder

c. Glandular – produces secretions

1) gland = tissue specialized to secrete substances

for use elsewhere or for elimination from the body

2) endocrine glands

a) ductless, diffuse through the surface

b) ex: adrenal glands, pancreas

3) exocrine glands

a) secrete through ducts

b) ex: sweat, sebaceous glands

B. Connective Tissue – most abundant tissue in body

1. protects, supports & binds other tissues together

2. characteristics

a. varied blood supply

1) most is well-vascularized

a) exceptions = cartilage is avascular, tendons & ligaments are poorly supplied

b. housed in extracellular matrix

1) nonliving substance outside cells

2) varies from liquid to gel-like to hard

3. Types differ by cell & fiber types and matrix texture

a. Bone – a.k.a. osseous tissue

1) cells = osteocytes

a) housed in lacunae surrounded by layers of very hard matrix

2) protects, supports

b. Cartilage

1) cells = chondrocytes

a) housed in more flexible matrix

2) 3 forms

a) hyaline – most abundant; collagen fibers in matrix

1)) found in larynx, end of ribs, articular cartilage,

fetal skeletons

b) fibrocartilage – creates vertebral discs

c) elastic – highly flexible, such as external ear

c. Dense connective – a.k.a. dense fibrous

1) collagen fibers found in matrix

a) create rope-like structures

2) major examples

a) tendons – connect muscles to bones

b) ligaments – join bones in moving joints

c) dermis – lower layer of skin

d. Loose connective

1) softer, more cells, fewer fibers in matrix

2) 4 types

a) areolar – wraps, cushions & protects organs and holds

them in place

b) adipose – a.k.a. fat, to insulate & cushion or store excess

energy

c) reticular – limited; forms stroma framework inside of

organs

d) blood – a.k.a. vascular tissue; transports gases, nutrients,

wastes

C. Muscle

1. tissue specialized to contract

2. elongated cells known as fibers

3. 3 categories

a. Skeletal – pull on bones, skin

1) voluntary

2) striated due to overlapping proteins

3) multinucleate cells

b. Cardiac – pump blood to blood vessels

1) found only in heart

2) involuntary

3) striated

4) uninucleate, branching cells

a) join to others by intercalated discs that allow

them to function as a single unit

c. Smooth – a.k.a. visceral muscle

1) uninucleate, spindle-shaped & lack striations

2) involuntary

3) dilate & constrict walls of hollow organs

a) incl. blood vessels, digestive tract, uterus, urinary

bladder

D. Nervous Tissues

1. cells = neurons & neuroglia

2. in brain, spinal cord, sense organs, nerves

3. functions

a. irritability – receive electrochemical impulses

b. conductivity – send impulses out in response

4. unique cell structure

a. central body w/ short, receiving dendrites & a long

sending axon