The Integument Flashcards
(33 cards)
What is the general structure of skin?
Two main layers: epidermis and dermis
What is the epidermis divided into?
Stratum corneum (outermost) - thickness varies greatly, usually dead keratanized cells
Stratum germinatuvum - mitotically active
What is the dermis divided into?
Stratum laxum Stratum compactum (innermost)
What is keratin?
A family of fibrous structural proteins, mostly in tetrapods
Fish have keratin and other similar proteins but not in high numbers
It is important in the structure of hair, feathers, and scales
What are the functions of the skin?
Physical protection, water balance, thermoregulation, locomotion, gas exchange, coloration, secretion, sensory structure
How is the skin important for thermoregulation?
Sweat glands
Arrector pilli muscles - attach to hair and feathers
When it contracts, it raises the hair, doesn’t do anything for us. Important for mammals because it allows hot air to be trapped so it acts like an insulating layer.
Seals and sea otters have hair but no pill, makes them slow down in water with pilli
How is the skin specialized for sensory structures?
COME BACK TO THIS
How does skin coloration work?
Chromatophores, which are pigment-producing cells that deposit pigment into other cells. Big cells with projections.
In birds and mammals, at the base of the epidermis
In other vertebrates, in dermis
What are the different types of chromatophores?
Melanophores - brown/black
Iridiophores - shiny (guanine crystals - byproduct of nucleic acid)
Xanthophores - yellow (modified nucleotide)
Erythrophores - red/orange - derivative of B-kerotene
What can affect colour? Give an example.
Diet in flamingoes
The more B-kerotene they eat, the more pink they look
What is another way of colorization?
Structural coloration (other = pigment)
How does structural coloration work?
Cells and proteins are arranged in certain ways that refract light to produce colours
This type of coloration might have been around at the time of the dinosaurs
Give an example of a mammal with structural coloration?
Mandrill - collagen arranged in certain way
How are mammals typically coloured?
Mostly only have melanophores which can produce a few different colors
How does mammalian coloration work?
MSH can stimulated melanophores to produce eumelanin pigment (brown). The pigment is produced in melanosomes (vesicles).
If the MSH receptor is inactivated, it triggers the production of pheomelanin (yellow).
What can mutations in MSH receptor lead to?
Kermode (spirit) bear - species of black bear that have mutations in the receptor
This is not the same as albino because albino don’t have the pigment, kermode have mutation in receptor
What is a cell that produces melanin?
Melanophore/melanocyte
What is melanin?
A pigment molecules that absorbs and reflects light
What is MSH?
Melanocyte stimulating hormone affects receptors
What is an MSH receptor?
Melanocortin receptor that the hormone affects
What is melatonin?
Produced by the pineal gland and affects sleep. In some vertebrates affects pigmentation (eg. frogs). It doesn’t alter our pigment
What are the roles of skin coloration?
Cryptic, aposematic, communication (sex), thermoregulation, UV protection
What is the physiological mechanism of colour change?
Similar in most animals that can do this
Hormonal/Nervous system control (1 or other)
Vesicles move via the cytoskeleton
When vesicles are spread out, cell appears dark
When they aggregate in the middle, they appear light
What are the different glands in fish and why?
Mucus - friction
Granular - toxins
Photophores - chemoilluminescence
