A&P Integumentary System

integumentary system

largest organ system in the body including all structures and tissues related to the skin

epidermis

superficial, avascular and thinner portion which is composed of epithelial tissue, composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers

dermis

below the epidermis, highly vascular and thicker connective tissue portion mostly fibrous connective tissue

hypodermis

superficial fascia, subcutaneous layer, loose areolar tissue and adipocytes absorb shock and insulates, anchors skin to muscles and other structures

integumentary system functions

protection, sensation, temperature regulation

components of integumentary system

skin, hair, nails, sweat glands, sebaceous glands

epidermis cell types

keratinocytes, melanocytes, Langerhans cells, Merkel cells

keratinocytes

most abundant cell type, produce keratin, protect the skin and underlying tissues from heat, microbes, and chemicals, several layers are dead keratinized cells

melanocytes

spider shaped cells deep in epidermis, make and store melanin into melanosomes, long slender projections extend between keratinocytes and transfer melanin granules to them

melanin

types are pheomelanin (yellow red), eumelanin (brown black), contributes to skin colour and absorbs UV light

Langerhans (dendritic) cells

arise from red blood marrow, migrate to epidermis, epidermal macrophages help other cells of immune system recognize and destroy invading microbes

Merkel (tactile) cells

least numerous, located in deepest layer of epidermis, associated with sensory nerve endings that function as touch receptors

five layers of skin (superficial to deep)

corneum, lucidum, granulosum, spinosum, basale

stratum basale

deepest layer of epidermis, also called basal layer or stratum germinativum as, single row of cuboidal or columnar keratinocytes, melanocytes abundant in this layer

stratum spinosum

second deepest, 8-10 layers of many side keratinocytes fitting closely together, desmosomes join cells together to resist tension and pulling, presence of some Langerhans cells, abundant melanosomes and keratinocytes

stratum granulosum

third deepest layer, consists of 3-5 layers of flattened keratinocytes, cell appearance and content changes (flatten cells, thicken cell membranes, lose nuclei and organelles, accumulation of keratin), cells accumulate lamellated granules, hydrolytic enzymes and proteins participate in desquamation

stratum lucidum

only present in thick skin, 4th deepest layer, thin transparent band consisting of a few rows of late dead keratinocytes

stratum corneum

outermost layer of keratinized cells, 15-30 rows of flat anucleated keratinized dry dead cells, about ¾ of epidermal thickness, protect deeper layers by preventing water loss and protecting from injuries

dermis fibers

contains collagen and elastin fibers, provide tensile strength, elasticity, and flexibility to the skin

dermis cell types

fibroblasts, macrophages, leukocytes, mast cells

structures embedded in dermis layer

epidermal hair follicles, oil glands, sweat glands

dermis layers

papillary (top), reticular (bottom)

papillary layer structure

composed of loose connective tissue with finger like projections called dermal papillae which interlock with the epidermis increasing SA for nutrient exchange

papillary layer function

supplies nutrients to the epidermis through capillaries and contains sensory receptors for touch, friction ridges contribute to formation of fingerprints

Meissner’s corpuscles

sensory receptors for touch

reticular layer structure

made of dense irregular connective tissue with thick bundles of collagen fibers that run in various directions, providing skin with strength and resilience, elastin provides elasticity and collagen provides structural and tensile strength

reticular layer function

supports the skin’s overall structure and houses the appendages of the skin, such as hair and glands

hypodermis

subcutaneous tissue, superficial fascia, deepest layer of the skin, lies between dermis and serves as connection between skin and muscles and bones, composed of loose connective tissue and adipose tissue

hypodermis structure

contains collagen and elastin, similar to dermis but less dense fibers to provide flexibility and cushioning

hypodermis function

supply with blood vessels, lymphatic vessels, and nerve fibers, helps with protection and cushioning of underlying tissue from mechanical injury, insulates, stores energy, prevents heat loss

skin accessory structures

hair, nails, skin glands

hair

made of hard keratin growing out of epidermis, originates from hair follicle (epidermal penetration of the dermis)

follicle

contains hair root embedded in the dermis, surrounded by arrector pili make hair stand up

hair shaft

made of dead cells, continuous with root, forms externally visible part of the hair

hair bulb

found deep in the dermis, contains mitotic basal cells (hair matrix) and surrounds hair papilla

hair papilla

dermal connective tissues with nerve ending and capillaries

hair role

sensory, protection, insulation

cuticle

outer layer of hair consisting of overlapping layers of single clear cells

cortex

middle layer of hair made of pigmented flattened cells around medulla

medulla

central core of hair with large cells and air spaces

nails

hard keratin modifications of epidermis, protect distal dorsal surfaces of fingers and toes, consist of free edge, body, and root

nail matrix

thick portion of nail root responsible for nail growth

nail folds

skin folds that overlap border of nail

eponychium

cuticle, nail fold that protects on surface of nail body

hyponychium

area under free edge of plate

sweat/sudoriferous glands

merocrine glands present on nearly all skin surfaces (except nipples and parts of external genitalia), perspiration controlled by nervous system signals myoepithelial cell contraction forcing sweat into ducts

eccrine sweat glands

all over the body but most abundant on palms, soles, and forehead, ducts connect to pores and function in thermoregulation, secrete hypotonic sweat that is mostly water by exocytosis

apocrine sweat glands

empty into hair follicles in axillary and anogenital areas, this sweat has more proteins and fats

sebaceous glands

oil glands, found all over body except thick skin, produce sedum that help lubricate stratum corneum, most associate and secrete into hair follicles, inactive during childhood

skin functions

protection, barrier, sensation, thermoregulation, vitamin d synthesis, immune defense, storage and synthesis, prevention of dehydration, excretion

Meissner corpuscles

tactile, sense light touch, found in papillary

Pacinian corpuscles

sense vibration, found in reticular

Merkel cells

touch receptors in stratum basale

hair follicle receptors

sense tectile touch

thermoreceptors

sense temperature changes, found in dermis

free nerve endings

sense pain

inflammatory/allergic skin disorders

acne, psoriasis, eczema, contact dermatitis

acne

condition where hair follicles become clogged with oil and dead skin cells, leading to pimples, blackhead, whiteheads, or cysts, caused by hormonal change, bacteria, excess oil, common in face, back, shoulders, and chest

psoriasis

autoimmune disorder that causes the rapid buildup of skin cells, leading to thick scaly patches, caused by immune system dysfunction, genetics, stress, or infection, common in scalp, elbows, knees, and lower back

eczema

chronic inflammatory skin condition characterized by itchy, red, and dry skin, caused by genetics, immune dysfunction, and environmental factors, common in face, elbows, knees, and hands

contact dermatitis

caused by contact with allergens or irritants, leading to redness, itching, and inflammation, found in hand, face, head, and neck

bacterial skin infections

impetigo, boil (furuncle), carbancle, cellulitis, folliculitis

viral skin infection

herpes simplex, warts, shingles

fungal skin infections

candidasis, athlete’s foot, ringworm, yeast infections

parasitic skin infections

scabies, lice

alopecia

condition that causes hair loss in patches (Alopecia areata) or complete baldness (Alopecia totalis), caused by autoimmune response, genetics, stress, or underlying health conditions

vitiligo

condition where skin loses its pigment cells, leading to white patches on different parts of the body, caused by autoimmune response, genetics, and possibly environmental factors

skin cancer

cancerous cells (abnormal cells that proliferate uncontrollable due to accumulated DNA mutations) accumulate in the skin

skin cancer risk factors

overexposure to UV, genetics, frequent skin irritation, skin type, family history, moles, age, immunosuppression

three major types of skin cancer

basal cell carcinoma, squamous cell carcinoma, melanoma

basal cell carcinoma

least malignant and most common, stratum basale cells divide and spread to other layers of the skin, cured by cryosurgery and ointments

squamous cell carcinoma

second most common, can metastasize, keratinocytes of stratum spinosum proliferate into papules on scalp, ears, lower lip, or hand, good prognosis with radiation therapy/surgical removal

melanoma

melanocyte cancer, highly metastatic and resistant to chemotherapy, key is detection

ABCDE rule

asymmetry, border (irregularity), colour (multiple), diameter (greater than 6mm), evolution (change over time)

burn

tissue damage caused by heat, electricity, radiation, or chemicals where cellular proteins and denatured and skin cells die which can lead to dehydration, electrolyte imbalance, and renal/circulatory failure

treatment of burns

fluid and nutrient IV administration, close monitoring of infections and antibiotic treatment, skin graft if necessary

first degree burn

superficial epidermal damage only, localized redness, edema, pain, heals in a few days

second degree burn

epidermal and upper dermal damage, swelling and blistering of the skin

third degree burn

full thickness burns, all layers of skin affected

fourth degree burn

affects all skin layers plus underlying tissue (bone or muscle)

scar

collagen rich skin formed during healing, fibroblast produce fibrous collagen that alter the structure of the skin losing accessory structures, overproduction of scar tissue can cause raised or hypertrophic scars (keloid)

stretch marks

excessive stretch beyond skin elasticity

bedsores

caused by excessive pressure on certain body parts, reduced blood flow results in tissue necrosis

calluses

hyperactivity of stratum basale to increase skin thickness in areas of high abrasion