The Integumentary System Chapter 6

Objectives  Identify the basic functions of the integumentary system  Distinguish between the two layers of skin on the basis of structure and function  Identify the layers of the epidermis, and describe the changes that occur in the cells as they are pushed toward the surface  Discuss the role of the integumentary system in regulating body temperature

Functions  Protection  forms physical barrier to prevent loss of body fluids, damage from physical injury or uv light, keeps out microorganisms  Regulation of body temperature  insulating barrier from external environment  Communication  sensory receptors relay info to brain

Functions continued  Excretion of wastes  sweat glands get rid of metabolic waste  Vitamin D Production  needed to help absorb calcium  calcium needed for bone growth and repair, muscle contraction and nervous system functions

The Skin  Primary organ of integumentary system  Two layers  epidermis  thin, superficial layer of epithelium  dermis  thicker, deep layer of connective tissue  hypodermis  connection between skin and muscle

Epidermis  forms protective waterproof layer  must constantly renew itself  composed of five layers  deepest to superficial  Stratum Basale  Stratum Spinosum  Stratum Granulosum  Stratum Lucidum  Stratum Corneum

Stratum Basale single layer of columnar cells cells capable of cell division newer cells push newer cells push older cells upward older cells upward as they move toward surface they lose surface they lose their blood supply their blood supply and begin to die and begin to die

Stratum Spinosum multiple layers of cuboidal cells cuboidal cells attached to each other by molecular bridges spiny appearance darkened nuclei first sign of death interstitial fluid no longer reaches these cells

Stratum Granulosum 3-5 rows of partly flattened cells cytoplasm has small granules – proteins in process of becoming keratin keratin = waterproofing protein

Stratum Lucidum only found in thick skin palms or soles of feet 3-4 rows of flat, dead, transparent cells keratin formation continues

Stratum Corneum rows of flat, dead cells sloughed off and replaced every 3 weeks – 1 month ghost cells contain keratin but not absolutely waterproof wrinkle after long bath due to osmosis

Skin color  Melanocytes = special cells in between stratum basale  secrete pigment – melanin  dark colored protein  more protein = darker skin  everyone has same number of melanocytes  color determined by amount of melanin produced  production regulated by genetic code  skin color inherited

Skin color continued  Melanin production modified by uv light  exposure increases production  job is to absorb uv light so body is protected from harmful rays  excessive exposure – can’t keep up  results in sunburn & skin cancer  Carotene  other pigment found in s. corneum & dermis  give yellowish hue = Asian people  Blood vessels of dermis (Caucasians)  High number = pink to red skin  Low number = pale skin

Review Questions  What are the five major functions of the integumentary system?  Why do cells die as they are pushed farther away from the stratum basale?  What factors determine the color of your skin?

Dermis  Connective tissue underlying the epidermis  intercellular material made of collagen  forms dense mat – like a wet sponge  large supply of blood vessels  ¼ of blood located here  nourishes cells and regulates temperature

Dermis continued  Papillary region  superficial area adjacent to dermis  named for papillae  fingerlike projections  interlock with epidermis strengthening layers  responsible for fingerprints/footprints  papillae project into epidermis forming friction ridges  ridges help hand or foot grasp surface of objects

Dermis continued  Reticular region  lies deep to papillary region  gives dermis strength, elasticity and extensibility  if we lose these properties we get wrinkles we get wrinkles

Accessory Organs  Located in dermis but originated elsewhere = epidermal derivatives  Functions  protection, communication, excretion  Examples  Hair, Sweat Glands, Nails

Hair  Functions  protects from injury from sunlight and foreign particles  follicle – supports hair  Two parts  Root – surrounded by the follicle  Shaft – part that extends from the surface

Hair continued  Grows similar to skin  Bulb provides nutrients to root and follicle  developing cells are in bulb next to blood supply pushed toward surface cytoplasm replaced by keratin – shaft made of keratin Grows 1mm/3days continues as long as cells are healthy Lose 100/day Not replaced if follicles are damaged Hair color affected by melanin get old-no melanin-gray hair

Hair Follicle Structures  Arrector Pili  narrow band of smooth muscle  extends at angle from follicle to papillary region  pulls hair vertically when you are cold or scared insulator – gives off heat presses sebaceous gland and forces oils to surface of skin

Hair Follicle Structures  Sebaceous Glands  oil glands  found all over skin except for palms and soles  secrete sebum  water, fat, cholesterol, protein and salt protein and salt  keeps hair & skin soft and pliable  water resistant layer  production accelerated by sex hormones  ducts get clogged – blackheads form

Sweat Glands  Sudiferous Glands  distributed throughout skin  secrete sweat/perspiration  Functions  maintain body temp  help kidneys eliminate metabolic waste  each gland is single tube, tightly coiled in dermis or hypodermis  Two types  Eccrine  Apocrine

Two types of sweat glands  Eccrine  functions throughout life  widely distributed through skin  secrete in response to high body temp  Apocrine  begin functioning during puberty  secrete thick sweat containing proteins  these proteins promote bacterial growth on skin  odor caused by microorganisms growing on skin  most active during periods of stress  most numerous in armpits and groin

Nails  Function  Protects end of fingers and toes  Helps pick up small stuff  Grips floor as we walk  Made of compressed epidermis and keratin  Nail body  visible surface  Cuticle  flap of stratum corneum overlying proximal edge of nail of nail

Nails continued  Nail root  contains active stratum basale  Nail matrix  pushes new cells outward  cells soon die and compress  Lunula  part of matrix seen through nail  Formation of keratin requires calcium  no calcium – thin brittle nails

Receptors  Distal ends of nerve cells  Act like antennae – receive info about world  Sensations travel to brain at 40m/s  Three types of receptors  Pacinian Corpuscles  pressure changes  Meissner’s Corpuscles  slight pressure  detects fine touch  Nerve Endings  excessive temp and pressure changes  detection of pain

Hypodermis  Lies deep to the skin  Insulating barrier for deep structures  Connects skin to underlying structures  uses strands of collagen extending from dermis through hypodermis to muscle layer

Temperature Regulation on HOT Days  Heat sensitive receptors in skin tell brain it’s too hot  Brain stimulates sweat glands  Body begins secreting sweat  Brain signals blood vessels to dilate  relax and expand  Blood flow to skin increases  Excess heat carried by blood escapes through skin to air  Sweat evaporates, cooling skin surface  Lower skin temp cools blood  Cooled blood travels to other parts of the body and internal temp is lowered

Temperature Regulation on COLD Days  Receptors tell brain it’s too cold  Brain tells blood vessels to constrict  reduces heated blood flow  reduces heat lost through skin  Brain tells skeletal muscles to contract  shivering  arrectores pilorum = goose bumps  contractions arrector pili produces heat

Other systems helping out  If body temp is too high  Cardiovascular System  heart beats faster which pushes blood to the surface faster to be cooled  Respiratory System  breathing rate increases so heat is carried out when we exhale