Presentation 10: Skin Flashcards
What are the functions of skin?
- protection from environment
- water and ion balance
- secretion of products (i.e. waste, hormones, compounds involved in behaviors)
- thermoregulation
- respiration (i.e. cutaneous for amphibians)
- locomotion (i.e. scales for snakes, nails/claws)
What is the function of the skin
- protection from the environment
- water and ion balance
- secretion of products (i.e. waste, hormones, compounds involved in behaviors)
- thermoregulation
- respiration (i.e. cutaneous for amphibians)
- locomotion (i.e. scales, nails/claws)
What are the layers of the skin
Epidermis = outermost layer(ectoderm derivative)
- stratified into Stratum Germinativum,
stratum granulosum, and stratum corneum
basal membrane = middle layer (gives rise to cells in epidermis and dermis)
Dermis = innermost layer (mesoderm derivative)
- divided into stratum spongiosum and
stratum compactum
Epidermis
Outermost layer of skin derived from ectoderm and stratified into:
- Stratum germinativum (inner layer w/ muvous and proteinaceous cells with keratin),
- Stratum granulosum middle layer (only in mammals)
- Stratum corneum (outer layer of dead cells)
Dermis
Innermost layer of skin derived from mesoderm that is thicker with a meshwork of fibers (e.g. collagen, elastin fibers) and is stratified into:
- Stratum spongiosum (outermost layer in contact w/ basal membrane) and
- Stratum compactum (innermost fibrous layer)
Basal Membrane
Gives rise to cells of both the dermis and the epidermis and located in-between the two (boundary)
Stratum Germinativum
The innermost layer of the epidermis consisting of 2 lines of cells (mucous which maintains moisture and proteinaceous which gives rise to upper layers)
Also contains keratin (e.g. for feathers, hairs, scales etc.)
What types of keratin are there and what are they used in
Alpha keratin is softer and found in hair and the stratum corneum
Beta keratin is harder and found in beaks and feathers
Stratum Granulosum
A synapomorphy for mammals, this middle layer of the epidermis is found between s. germinativum and the s. corneum
Stratum Corneum
The outside layer of epidermis made up of dead cells
Stratym Spongiosym
Outermost layer of the Dermis in contact with the basal membrane
Stratum Compactum
The innermost layer of the dermis that is fibrous
Chromatophores
cells that accumulate pigment
i.e. Melanophores, Iridiophores, Xanthophores and Erythrophores
Melanophores
produces darker colorations based on melanin accumulations that can change based on expansion (darker) or contraction (lighter) of melanin in the cell)
Where is pigment found for Homeotherms/endotherms vs Poikotherms vs ecthotherms
- Homeotherms/endotherms, pigment found in the epidermis
- Poikiotherms or ecthotherm, pigment found in the dermis
Iridophores
crystals of guanine accumulate in the platelets to reflect light causing white and silver colorations
Xanthophores
Accumulation of pteridines that produce yellow pigment
Erythrophores
Accumulation of carotenoids that produce red pigment
What are the 2 major classes of glands and what is the difference between the two
Exocrine vs Endocrine glands.
The difference between these two type of glands is where their products are secreted. Exocrine glands secrete substance into a ductal system to an epithelial surface (to skin) whereas endocrine glands secrete products directly into the bloodstream
Types of Exocrine glands
Unicellular glands (in fishes and larval amphibians, i.e. goblet cells - single cells that produce mucus to maintain humidity)
Multicellular glands (in tetrapods, either alveolar aka flask-like or tubular)
What types of cutaneous glands do amphibians have
- Mucous glands ( produce mucus which aids in cutaneous respiration, reproduction, thermoregulation, and defense)
- Granular glands (present in toads and reptiles and secrete toxic alkaloids that are defensive and ward off predators or a source of pheromones such as reproductive pheromones. Include parotoid glands (toxic substance) and femoral glands (substance that hardens to form temporary spine to restrain females during copulation)
Mucous Glands
produce mucus which aids in cutaneous respiration, reproduction, thermoregulation, and defense - found in amphibians and reptiles bids and mammals in the stratum corneum
Granular Glands
Include pheromone releasing glands that participate in behavior (i.e. social or sex scent glands in reptiles) and parotoid glands (i.e. toxic defense in amphibians)
What kinds of Cutaneous Glands to birds have
They are mostly aglandular but they have Uropygial glands which is right above the tail and secretes mucus that the birds then spread throughout feathers to protect them from water
What keratinized regions are in birds
Beak, feathers, scales in legs, spurs, egg-tooth in birds and reptiles
Structure of a feather (Contour Feathers)
- Rachis or shaft running up the middle from the medial to the distal end
- Barbs that extend out from the shaft that then have barbules extending off of them
- Barbules have hooklets extending off of them
What are the types of feathers
Contour: give shape and color and found everywhere except the beak, legs, and feet. The base is downy (helps insulate) and include the flight feathers of the wing and tail
Down: reduced shaft, soft and fluffy, beneath the contour feathers to aid in insulation/thermoregulation
Semiplume: cross btw down and contour feathers, they have a formed shaft but poorly developed barbules and hooklets
Bristles: stiff w/ a few barbs on the calamus, around the mouth and eye and connected to nerve endings (serve a sensory function)
Filoplumes: incredibly small, tuft of barbs at tip of shaft and also connected to nerve ending and serving a sensory function
Contour feathers:
give shape and color and found everywhere except the beak, legs, and feet. The base is downy (helps insulate) and include the flight feathers of the wing and tail
Down feathers:
: reduced shaft, soft and fluffy, beneath the contour feathers to aid in insulation/thermoregulation
Semiplume feathers:
cross btw down and contour feathers, they have a formed shaft but poorly developed barbules and hooklets
Bristles feathers:
stiff w/ a few barbs on the calamus, around the mouth and eye and connected to nerve endings (serve a sensory function)
Filoplumes feathers:
incredibly small, tuft of barbs at tip of shaft and also connected to nerve ending and serving a sensory function
What are the major glands in mammals
- Sweat glands (sudiferous), multicellular tubular glands that are variable and prevent overheating through evaporation (not present in whales)
- Sebaceous glands: Alveolar or flask-like glands that produce an oily product. Ex. scent glands unsed for attraction, defence, and marking territory
- Mammary glands are modified sebaceous glands that are unique to therian mammals and only active at time of birth
How do feathers develop
Derived from the ectodermal placoid and the dermal papillae, epidermal placoid sinks into dermis channel around base of future feather forming the feather follicle. The follicle elongates forming a rachis and blood vessels irrigate for early nutrients. blood vessels and dermal papilla retreat and pulp caps form to segment the follicle it which gives rise to barbs. The calamus is formed at the base and mesodermal papillae remains with calamus to form the new feather
How does hair develop
Very similarly to feathers, there is an epidermal cluster that moves dermally to form a dermal papilla. The hair primordium/follicle elongates down into the dermis and the hair follicle grows out facilitated by a sebaceous gland. The arrector pili muscle is attached to each follicle and able to make your hair stand up
What are the different types of scales
- placoid scales (denticles)
- Cosmoid scales (ancestral scale)
- Ganoid scales (found in Latimeria and Brachiopterygii)
- Leptoid scales (in most fishes)
Placoid scales
(denticles), found in Chondrichthyes. Dense layer of lamellar bone, dentine, and enamel (aka ganoin). lack spongy bone and are avascular and derived from vertebrate teeth
Cosmoid scales
Scales of all 4 layers of bone found in primitive agnathans and primitive bony fishes but not found in any living fishes
Scale bone layers
- Lamellar bone (inner layer)
- Spongy (vascular bone)
- Cosmine = dentine bone-like material
- Ganoin layer = enamel-like
Ganoid scales
Lack spongy bone, has greater development of the ganoid layer and found in Latimeria and Brachiopterygii (gars, bichirs, and reedfishes)
