A & P TEST 1 | integumentary system

skin (cutaneous membrane)

largest organ in the body

epidermis

thin, superficial

dermis

thicker, deep

skin rests on ____(subcutaneous layer) that stores fat and has large blood vessels

hypodermis

stratum basale (basal layer)

• deepest layer

• attached to dermis by hemidesmosome

• 1 row of stem cells

• melanocytes (10-25% of the layer)

stratum basale mitosis (2 cells)

• one stays a stem cell

• one becomes a keratinocyte

stratum spinosum (prickly layer)

• 8-10 rows of irregular/spiny cells

• keratinocytes do not divide, joined by desmosomes

• cells contain web-like pre-keratin system

• cells contain melanosomes

• dendritic cells are present

stratum granulosum (granular layer)

• thin layer: 3-5 rows of cells

• keratinocytes change drastically

• accumulate water-resistant glycolipids

what drastic change in appearance happens in the stratum granulosum?

• become flat

• nuclei and organelles deteriorate

• keratinization begins

glycolipid

slows water loss

stratum lucidum (clear layer)

• only in thick skin: palms and soles

• thin clear layer above statum granulosum

• few rows of flat, clear, dead keratinocytes

• provides extra protection

stratum corneum

• 20-30 rows of dead, flat, anucleate keratinized cells

• cells at surface are sloughed

• dead cells still provide a protective barrier

cells of epidermis

• keratinocyte

• melanocyte

• intraepidermal (langerhans) macrophage

• tacticle epithelial (merkel) cell

keratinocytes

• numerous, arranged strata

• produce protective keratin protein and lamellar granules that release waterproofing substance

• connected by desmosomes

melanocytes

• produce pigment melanin for protection from UV light

langerhans cells (dendritic)

immune response (phagocytosis)

tactile epithelial / merkel cells

function with merkel disc of dermis for touch

A

epidermis

B

stratum corneum

C

stratum lucidum

D

stratum granulosum

E

stratum spinosum

F

stratum basale

G

dermis

H

dead keratinocytes

I

sweat gland duct

J

living keratinocyte

K

melanocyte

L

epidermal dendritic cell

M

basement membrane

N

tactile cell

O

sensory nerve ending

eumelanin

brown/black color

pheomelanin

yellow/tan color

carotene

source of yellow-orange pigment

hemoglobin

• oxygen carrying red pigment in blood

• visible through skin in dermal blood vessels

• oxygen level + dilation/constriction can change color

nevus (mole)

local overgrowth of melanocytes

freckles

• yellowish or brown spots

• local area of increased melanocyte acitvity

hemangiomas

• skin discoloration due to benign blood vessel tumor

• ex: capillary and cavernous hemangiomas

friction ridges

• large folds and valleys of dermis and epidermis

• responsible for fingerprints

dermis components

• papillary components

• reticular components

papillary components

• meissner corpuscles

• capillary loops (blood capillaries)

• free nerve endings (temperature, pain, itching)

reticular components

• fibroblasts, adipocytes, and macrophages

• blood vessels + nerves (smooth muscle)

• hair follicles + glands

• lots of collagen (reticular formation)

lines of cleavage

bundles of collagen and elastic fibers in parallel bundles (heal more quickly)

derivatives of the skin (appendages)

• derived from epidermis

• located in the dermis

• include cutaneous glands, sweat glands, oil glands, hair follicles, nails

3 types of glands of the skin

• eccrine

• apocrine

• sebaceous

2 main types of sweat glands

• eccrine (merocrine)

• apocrine

eccrine sweat glands

• widely distributed

• abundant on palms, soles, and forehead

• duct transports sweat to skin surface through a pore

• poorly functional before age 2

• true sweat

secretion (true sweat)

• 99% water, salt, vitamin c, antibodies, dermicidin and metabolic wastes

• pH 4-6

primary function of eccrine sweat glands

thermoregulation

secondary functions of eccrine sweat glands

excretion of wastes, protection from microbes

apocrine sweat glands

• found in axillary and pubic regions

• larger than eccrine glands

• duct transport sweat into a hair follicle

• start working at puberty

• secretion: sweat + fatty substances + protein

modified apocrine sweat gland

• ceruminous glands

• mammary glands

ceruminous glands

• only found in ear canal

• secrete cerumen (earwax)

mammary glands

• located in breasts

• secrete milk

• found in males + females

• functional in pregnant and lactating females

• apocrine secretion

sebaceous (oil) glands

• found everywhere EXCEPT palms + soles

• holocrine secretion (entire cell ruptures)

• inactive until puberty

• secretes sebum

thick skin

only on palms, soles, and palmar portion of fingers and toes

thin skin

everywhere else

functions of integumentary sytem

1. protection

2. body temp regulation

3. cutaneous sensations

4. metabolic functions

5. blood reservoir

6. excretion

physical barriers

• dead keratinized cells + lipids

• protects from abrasion

• 1st line of defense against pathogens

• prevents dehydration

• keratin + glycolipids block water + water soluble substances

• limited penetration (selectively permeable)

what can penetrate skin

• lipid soluble substances

• plant oleoresins

• organic solvents

• salts of heavy metals

• some drugs

chemical barriers

• skin secretions

• melanin

skin secretions

• called acid mantle

• low pH slows bacterial mitosis

• sebum, dermicidin and defensins kill bacteria

melanin

• defense against UV radiation damage, protects DNA

biological barriers

• dendritic cells of epidermis

• macrophages of dermis

• white blood cells patrol skin tissue

dendritic cells of epidermis

present for eign antigens to cells of adaptive immune system

macrophages of dermis

hunt and phagocytize foreign material

cutaneous sensations

• contains nerve endings and receptors that detect stimuli

• detect temperature, touch and pain

blood reservoir and excretion

• up to 5% of blood can be stored in dermal capillaries

• if organs need more oxygen due to blood loss, capilaries vaconstrict

• sends blood to core of the body

• causes pallor (pale skin)

deep wound healing (4 phases)

• inflammatory

• migratory

• proliferative

• maturation

proliferative phase

continued growth and repair

maturation phase

scab sloughs off, fibrosis can form scar

rule of nines

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

pressure ulcers (bed sores)

• lack of blood flow to tissues can cause

• causes epithelium to shed

• risk increases with age