integumentary system

• what are the epidermal layers ?

  epidermis, dermis, hypodermis
• what are the functions of the skin?


  protection, storage, sensory neurons, production, gaseous exchange, waterproofing, absorption, respiration and thermoregulation
• what is stored in the skin?

  lipids and water
• what does the skin produce?

  new cells and vitamin D
• the epidermis is made up of flat cells and no blood vessels, hair exits the skin here. sweat and oil glands secrete here
• the dermis is the middle layer of skin, it contains hair follicles, nerves and blood vessels. contains glands that help to regulate body temperature
• the hypodermis is underneath the skin. it is a layer of fat and loose connective tissue, functions as an energy reserve and aids in thermoregulation
• fat tissue protects and insulates the body
• why do snakes have elastic skin?

  so it can stretch and withstand prey attempt to escape
• why do some animals change the colour of their skin?

  to hide from predators, intimidate rivals and woo mates. this can also send information to others (ready to mate)
• why is amphibian skin thick and moist?

  allows gases to pass through which helps the frog to breathe. they breathe through their skin when burrowing and when underwater
• why do elephants have thick skin?


  to hold together their mass
• why do elephants have wrinkles?


  they act as a cooling mechanism by increasing the skins surface area. they trap moisture which then takes longer to evaporate
• why do elephants have thin skin on their ears?

  when they flutter their ears, the capillary blood vessels and therefore the body is cooled.
• what are the three exocrine glands?

  sudoriferous, sebaceous, ceruminous
• what does the sudoriferous gland secrete?

  sweat
• what does the sebaceous gland secrete?

  sebum, this keeps skin and hair lubricated
• what does the ceruminous gland secrete?

  ear wax
• some hair is found on all mammals, no other creature possesses true hair
• the base of the hair, sunk into the skin is called ?

  the root
• the part of hair that emerges to the exterior?

  the shaft
• next to the folicle, an involuntary arrector pili muscle may be found. hair normally lies parallel to the skin. contraction of the arrector pili muscles will cause the hair to erect and pulls down on the skin, this causes bumps known as 'goosebumps'
• what is hair made of?

  keratin
• what is downy hair?


  dense, fine, soft hair which lie close to the skin, making up the undercoat and providing insulation
• what is guard hair?

  coarse, thicker, longer hairs, that make up the top coat, helping prevent injury to the skin
• 6-12 downy hairs surround one guard hair
• a nail matrix forms on top of the dermis, the root of the nail grows from a thick layer of matrix
• label this diagram of a vaned feather:

  A) rachis

  B) vane

  C) calamus

  D) barb

  E) barbule

  F) downy barbs

  G) hooklets

  H) barbule

  I) barb

  
• claws and hooves are made up of a section of the dermis which is covered in a layer off keratinised epithelium
• what are hooves?


  horses hooves are the thick and horny coverings that protect the end of a horses leg and also provides shock absorbency
• the keratin in a horses' hoof is layered in horizontal sheets, in order to add strength and to minimise the extent of any damage that could split the hoof irreparably
• the outer wall of a hoof is insensitive, the inner parts can feel pain
• antlers are bone. young antlers are covered in velvety skin which is rubbed off over time as the antlers develop. the bone them turns into compact bone tissue as they mature
• a hollow horn is compromised of keratin, a solid horn has additional melanin and calcium. if a horn breaks off, a new one can be developed
• elephants tusks are made up of ivory which its largely made up of dentine, this is what makes up teeth.
• can elephants grown their tusks back?


  no
• horns and antlers are made up of different things depending on the species
• when it is cold, feathers trap air underneath and muscles connected to the feathers allow the bird to fluff itself up to trap more air
• how do birds cool down?

  they compress the feathers to eliminate heat trapping pockets of air
• why do birds apply oil to their feathers?

  to waterproof them and prevent the growth of bacteria or fungi