Anat and Phsy week 2 - Integument

what is the integument

the skin, the largest organ of the body

what functions do skin perform

protects underlying tissues and organs

excretes salts, waters, and organic wastes

maintains body temperature

synthesizes vitamin D_³

stores lipids

detects touch, pressure, pain, and temperature

what are the two major components of the integument?

the cutaneous membrane and the accessory glands/organs

what is the cutaneous membrane?

the epidermis and the dermis

sometimes the hypodermis even though its not technically considered integument

what are the 5 layers of the epidermis?

stratum corneum

stratum lucidum

stratum granulosum

stratum spinosum

stratum germinativum

what are the characteristics of the epidermis

avascular - no blood veins

stratified squamous epithelium - living cells w/ increased metabolic demands closer to dermis

is made up of cells called keratinocytes → contain keratin, toughens skin and water-proof

skin life cycle: takes 15-30 days for a cell to move from stratum germanitivum to stratum corneum

stratum germanitivum

the “germinative layer”

has many germinative cells or basal cells, replace dead and last cells from layer above, is attached to the basal lamina

basal lamina

a collection of glycoproteins and protein filaments

• connects epithelial tissue to underlying tissue

• secreted by epithelial cells

• cells of stratum basale are connected via protein accumulation called hemidesmosomes

what forms cellular connections?

connections of epithelial cells to one another

occurs at the desmosomes, many in the epidermis

epidermal ridges and dermal papillae formed in stratum germinativum

what are fingerprints?

ridges and papillae which are translated to the surface

what are the specialized cells of the stratum germinativum

merkel cells - found in hairless skin, respond to touch

melanocytes - contain/produce melanin pigment, number of these cells is determined genetically

what is the stratum spinosum (aka the spiny layer → due to desmosomes)

is produced by division of the stratum germinativum

continues to divide, increasing the thickness of the epithelium

contain dendritic cells which are active in immune response, antigen presenting

what is the stratum granulosum (aka the grainy layer)?

where living skin cells turn into the tough, dead barrier cells that protect the body

has cells that produce protein fibers and flatten

they dehydrate and die

the plasma membrane becomes less permeable, and they create tightly interlocked layers of keratin

what is the stratum lucidum?

the “clear layer”

is found only in thick skin, like palms of hands and soles of feet

is superficial to the stratum granulosum

cells are flattened, no organelles

what is the stratum corneum?

the “horn layer”

is exposed to the surface of the skin

contains 15 to 30 layers of keratinized cells

is shed and replaced every 2 weeks

is water resistant, we lose 1 pint per day w/o sweating

where/how is vitamin D produced

by/in the cells of the stratum germinativum and the stratum spinosum in response to uvb radiation

modified by liver and kidneys to produce calcitrol → which increases calcium absorption

effects of sun exposure on the skin

damages collagen and elastic fibers in the dermis, which can speed up/worsen aging

also damages dna, a sunburn is inflammation due to skin cell damage, can lead to skin cancer

what/where is the dermis

located between the epidermis and the subcutaneous layer

how many components does the dermis have? what are they?

2

the superficial loose CT proper

the deep dense irregular CT proper

how does blood supply to the dermis work?

branches of deep arteries form networks of blood vessels in the reticular and papillary layer, contusion (bruising) occurs when one or some of these vessels rupture

what is the hypodermis

the subcutaneous layer

lies below the integument, stabilizes the skin, allows separate movement, is made of loose connective tissues (CT proper) and adipose (fat) tissues

connected to the reticular layer of integument via connective fibers

subcutaneous fat

insulates, absorbs shock, stores energy

two types: white fat and brown fat

what are the accessory organs of the integument

hair follicles, oil glands, sweat glands, and nails

what is hair?

made up of dead keratinized cells, made of the root and shaft

how/where is hair produced

hair is produced from the base of the follicle, hair bulb is the site of mitosis

consists of the arrector pili muscle (responsible for goosebumps!), sebaceous glands (oil), and color (dunno how?)

what are sudoriferous glands

sweat glands

how many types of sudoriferous glands are there? what are they?

2 types

apocrine and eccrine (merocrine)

apocrine sweat glands

discharge sweat into hair follicles of axilla (armpit), nipples and groin. begins at puberty

eccrine or merocrine sweat glands

most common type, discharges onto the skin, has water and salt, protects from hazards like bacteria, cools you down

the “sweaty” odor is just from bacteria, not the actual sweat itself

what are ceruminous glands?

modified sweat glands in external ear, EAR WAX

secretions combine with sebaceous glands to form cerumen

protects the ear canal from foreign objects, insects, and bacteria

what are nails?

made up of dead keratinized cells

root → fold of epidermal tissue

cuticle → stratum corneum

color → capillaries in dermis