Human Anatomy: Chapter 5

What is the largest organ of the body?

skin

What is the two structural parts of the skin?

epidermis and dermis

What is the epidermis made of?

keratinized stratified squamous epithelial tissue

What is the dermis made of?

connective tissue

What is the hypodermis/subcutaneous layer?

it is not part of the skin; areolar and adipose tissue; serves as fat storage, blood vessel passage, and nerve endings

What are the four types of cells in the epidermis?

keratinocytes, intraepidermal macrophages/langerhans cells, melanocytes, and tactile epithelial cells

What are keratinocytes?

produce the protein keratin, which helps protect the skin and underlying tissue from heat, microbes, and chemicals, and lamellar granules, which release a waterproof sealant

What are melanocytes?

produce the pigment melanin which contributes to skin color and absorbs damaging UV light

What are intraepidermal macrophages/langerhans cells?

immune responses

What are tactile epithelial cells/merkel cells

contact a tactile/merkel disc and sense touch

What are the four/five layers of the epidermis from deep to superficial?

stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (only in thick skin), stratum corneum

What is the basale layer?

deepest layer; single row of cuboidal or columnar keratinocytes; stem cells undergo cell division to produce new keratinocytes here; melanocytes and tactile epithelial cells with tactile discs here

What is the corneum layer?

50 or more rows of dead, flat keratinocytes made of mainly keratin

What is keratinization?

replacement of cell contents with the protein keratin, occurs as cells move to the skin surface over 2-4 weeks

What are the two types of skin?

thin (hairy) skin (everywhere but palms and soles) and thick (hairless) skin (only on palms and soles)

What are the two regions of the dermis?

papillary and reticular

What is the papillary?

superficial; areolar connective tissue with thin collagen and fine elastic fibres; dermal ridges that house blood capillaries, tactile corpuscles, and free nerve endings

What is the reticular?

deep; dense irregular connective tissue with bundles of thick collagen and some coarse elastic fibres; adipose cells, hair follicles, nerves, sebaceous glands, and sudoriferous glands

What is melanin?

produced by melanocytes in the basale

What are the three types of melanin?

pheomelanin (yellow-red), eumelanin (brown-black), and freckles (patches of melanin)

What is hemoglobin?

red pigment of RBCs

What is carotene?

yellow-orange pigment in stratum corneum and adipose tissue

What is albinism?

congenital disorder that causes complete or partial absence of pigment in the skin, hair, and eyes due to a defect of an enzyme involved in the production of melanin

What is vitiligo?

a chronic disorder that causes depigmentation patches in the skin, unknown cause

What is hair made of?

dead, keratinized epidermal cells

What are the parts of the hair?

the shaft (above the skin), cuticle, the follicle (below the skin), and the root (dermis and subcutaneous)

What are the three growth stages of hair and what happens during them?

growth stage: cells divide, hair grows longer

regression stage: cell division and growth stops, follicle atrophies

resting stage: hair root falls out of the follicle

What is lanugo hair?

fine, nonpigmented, downy hair that covers the fetus

What is vellus hair?

short, fine, pale hair; “peach fuzz”​

What is terminal hair?

long, coarse, pigmented hair; hair of the head, eyelashes and eyebrows​; increase in response to androgens​

What determines hair colour?

amount and type of melanin

What is the function of hair?

protection, decrease in heat loss, and sensing light touch

What are the three types of skin glands and their function?

sebaceous (oil): connected to hair follicles

sudoriferous (sweat): help to regulate body temperature and eliminate wastes

ceruminous: modified sweat glands that produce called cerumen in the ear canal​

What are nails?

keratinized epidermal cells over the dorsal surfaces of the terminal portions of the fingers and toes

What are the functions of skin?

thermoregulation, blood reservoir (8-10%), protection, cutaneous sensations, excretion and absorption, synthesis of vitamin D

What are the six specific cells and secretions used in protection of the skin?

keratin: protects tissues ​

lipids: guards against dehydration​

sebum: kills bacteria and prevents skin/hairs from drying out​

acidic sweat: decreases bacterial growth​

melanin: UV protection​

macrophages: immune protection​

How is vitamin D synthesized?

requires activation of a precursor molecule in the skin by UV light, with enzymes in the liver and kidneys modifying the activated molecule to produce calcitriol

What are epidermal wounds?

the central portion of the wound usually extends deep down to the dermis, whereas the wound edges usually involve only superficial damage to the epidermal cells; repaired by enlargement and migration of basal cells, contact inhibition, and division of migrating and stationary basal cells; epidermal growth factor stimulates basal cells to divide and replace the ones that have moved into the wound

What are the four steps to deep wound healing and explain each?

inflammatory phase: a blood clot unites the wound edges, epithelial cells migrate across the wound, vasodilation and increased permeability of blood vessels deliver phagocytes, and fibroblasts form

migratory phase: epithelial cells beneath the scab bridge the wound, fibroblasts begin scar tissue, and damaged blood vessels begin to grow, tissue filling the wound is called granulation tissue

proliferative phase: events of the migratory phase intensify

maturation phase: the scab sloughs off, the epidermis is restored to normal thickness, collagen fibers become more organized, fibroblasts begin to disappear, and blood vessels are restored to normal, fibrosis can occur in deep wound healing

What age does the most effects of aging on the skin occur and what are some of them?

late forties; wrinkling, slow hair and nail growth, dryness and cracking, gray hair, decreased immune responsiveness, loss of subcutaneous fat and thinner skin, sweat production decrease, nails become more brittle

How does the integumentary system help all the other body systems?

skeletal: helps with vit. D production

muscular: provides calcium ions

nervous: input to brain

endocrine: vit. D converted to calcitriol

cardiovascular: vasodilation and vasoconstriction ​

lymphatic: first line of defense

respiratory: remove dust particles

digestive: promotes absorption of calcium

urinary: waste products excreted through sweat

reproductive: respond to erotic pleasure

What are the three major types of skin cancer?

basal cell carcinoma, squamous cell carcinoma, and malignant melanoma

What is a burn?

tissue damage caused by excessive heat, electricity, radioactivity, or corrosive chemicals that break down the proteins in the skin cells; the systemic effects of a burn are a greater threat to life than are the local effects

What is the rule of nines

used to estimate the surface area of an adult affected by a burn​

What is a pressure ulcer?

a constant deficiency of blood to tissues overlying a bony projection that has been subjected to prolonged pressure against an object such as a bed, cast, or splint