Unit 2: Integumentary System Notes Part 1

two major groups of body membranes

epithelial membranes and connective tissue

3 epithelial membranes

cutaneous, mucous, serous

functions of epithelial membranes

covering and lining

cutaneous membrane

skin

superficial epidermis

composed of keratinizing stratified squamous epithelium

cutaneous membrane

dry

mucous membranes

line body cavities that open to the exterior

mucous membranes

respiratory, urinary, digestive, and reproductive tracts

mucous membranes

wet

serous membranes

line body cavities that are closed to the exterior

serous membranes

thoracic, abdominal

serous membranes

occurs in pairs

serous membranes

parietal and visceral

parietal layer

line the inside wall of the cavity

visceral layer

line the outside of organ

connective tissue membranes

synovial membranes

synovial membranes

line the fibrous capsules surrounding joints, bursae, and tendon sheaths

skin

body’s largest organ

skin

weighs about 10 pounds

skin

surface area of about 20 square feet

integumentary system

skin, hair, nails, exocrine glands

two primary layers of skin

superficial epidermis and dermis

epidermis

stratified squamous epithelium in 5 zones

epidermis

20-50 layers thick

epidermis

avascular

epidermis

rapid cell division occurs in lower layer

epidermis

cells die as they migrate towards the surface

keratinocytes

make up almost 90% of cells in epidermis

keratinocytes

produce and store the protein keratin

keratin

makes cells tough, scaly, and water-resistant

melanocytes

located in lower layer of the epidermis

melanocytes

produce the pigment melanin

melanocytes

melanin protects skin from UV radiation

melanocytes

freckles and moles are concentrated melanin

carotene

they are components of the pigment systems and are involved in the primary light absorption

hemoglobin

the protein contained in red blood cells that is responsible for delivery of oxygen to the tissues

dermis

gives skin strength and elasticity

dermis

varies in thickness

dermis

particularly thick on palms and soles of feet

two regions of dermis

papillary layer and reticular layer

papillary layer

superficial layer borders the epidermis

papillary layer

projections called dermal papillae hold epidermis and dermis together

papillary layer

capillary loops nourish epidermis

papillary layer

pain receptors - free nerve endings

papillary layer

touch receptors - meissner’s corpuscles

reticular layer

blood vessels

reticular layer

sweat and oil glands

reticular layer

deep pressure receptors - pacinian corpuscles

reticular layer

phagocytes act to prevent bacteria from penetrating more deeply into the body

dermis

collagen and elastin

collagen

a protein that gives toughness and hydration to the skin

elastin

a fibrous glycoprotein that provides elasticity

hypodermis

holds skin to underlying tissue and stores fat

sudoriferous glands

also called sweat glands

sudoriferous glands

eccrine and aprocrine

eccrine

most common gland and widely distributed in skin

sudoriferous glands

ducts lead to pores which open at the skin’s surface

sudoriferous glands

sweat reduces body temperature

apocrine glands

less numerous than eccrine glands

apocrine glands

concentrated in axillary and genital areas

apocrine glands

have ducts that empty into hair follicles

apocrine glands

secretion contains fatty acids and proteins in addition to usual products

apocrine glands

odor is from associated bacteria

apocrine glands

begin to function during puberty

sebaceous glands

produce oil called sebum

sebum

skin and hair lubricant

sebum

contains anti-bacterial substances

sebaceous glands

most have ducts that empty into hair follicles

sebaceous glands

glands are activated at puberty

hair

grows from root in the hair follicle

hair

consists of tightly packed keratinocytes

hair

melanocytes provide pigment for hair color

hair

protects skin from UV radiation

nails

sheets of hardened keratinocytes

nails

reinforce and protect distal ends of fingers and toes

nails

nail matrix produces new growth

lunula

thick area over nail matrix

5 basic skin functions

protection, temperature control, excretion, vitamin D production, detection of stimuli

keratinization

the process of keratin accumulating within keratinocytes

protection

provided by the tough keratin barrier

protection skin function

protects mechanical damage such as bumps

protection skin function

protects chemical damage such as exposure to acids and bases

protection skin function

bacterial damage

protection skin function

desiccation or drying out

temperature control skin function

responds to high body temperature through activating sweat glands and relaxing blood vessels and increasing blood flow into capillary beds

temperature control skin function

responds to low body temperature by constricting blood vessels and reducing blood flow into capillary beds

arrector pili muscles

small bands of smooth muscle that connect hair follicles to the dermis

excretion skin function

urea, uric acid, ammonia, and lactic acid are eliminated through perspiration by sweat glands

composition of sweat

mostly water, some salts, vitamin c, metabolic wastes, low ph of sweat inhibits bacterial growth

vitamin D synthesis skin function

modified cholesterol molecules in the skin are converted into vitamin D by sunlight

vitamin D synthesis skin function

vitamin D is necessary for the absorption of calcium and also plays a vital role in immunity

detection of stimuli skin function

the sense of touch is accomplished by a variety of nerve endings

detection of stimuli skin function

free nerve endings detect temperature and pain

detection of stimuli skin function

meissner’s corpuscles detect light touch

detection of stimuli skin function

pacinian corpuscles detect deep pressure

tissue damage and cell death cause

heat, electricity, UV radiation, chemicals

rules of nines

way to estimate the extent of burns

rule of nines

body is divided into 11 areas for quick estimation

rule of nines

each area represents about 9%

severity of burns

first-degree, second-degree, third-degree