Presentation 10: Skin

Question 1

What are the functions of skin?

Answer 1

• 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)

Question 2

What is the function of the skin

Answer 2

• 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)

Question 3

What are the layers of the skin

Answer 3

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

Question 4

Epidermis

Answer 4

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)

Question 5

Dermis

Answer 5

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)

Question 6

Basal Membrane

Answer 6

Gives rise to cells of both the dermis and the epidermis and located in-between the two (boundary)

Question 7

Stratum Germinativum

Answer 7

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.)

Question 8

What types of keratin are there and what are they used in

Answer 8

Alpha keratin is softer and found in hair and the stratum corneum
Beta keratin is harder and found in beaks and feathers

Question 9

Stratum Granulosum

Answer 9

A synapomorphy for mammals, this middle layer of the epidermis is found between s. germinativum and the s. corneum

Question 10

Stratum Corneum

Answer 10

The outside layer of epidermis made up of dead cells

Question 11

Stratym Spongiosym

Answer 11

Outermost layer of the Dermis in contact with the basal membrane

Question 12

Stratum Compactum

Answer 12

The innermost layer of the dermis that is fibrous

Question 13

Chromatophores

Answer 13

cells that accumulate pigment
i.e. Melanophores, Iridiophores, Xanthophores and Erythrophores

Question 14

Melanophores

Answer 14

produces darker colorations based on melanin accumulations that can change based on expansion (darker) or contraction (lighter) of melanin in the cell)

Question 15

Where is pigment found for Homeotherms/endotherms vs Poikotherms vs ecthotherms

Answer 15

• Homeotherms/endotherms, pigment found in the epidermis
• Poikiotherms or ecthotherm, pigment found in the dermis

Question 16

Iridophores

Answer 16

crystals of guanine accumulate in the platelets to reflect light causing white and silver colorations

Question 17

Xanthophores

Answer 17

Accumulation of pteridines that produce yellow pigment

Question 18

Erythrophores

Answer 18

Accumulation of carotenoids that produce red pigment

Question 19

What are the 2 major classes of glands and what is the difference between the two

Answer 19

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

Question 20

Types of Exocrine glands

Answer 20

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)

Question 21

What types of cutaneous glands do amphibians have

Answer 21

• 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)

Question 22

Mucous Glands

Answer 22

produce mucus which aids in cutaneous respiration, reproduction, thermoregulation, and defense - found in amphibians and reptiles bids and mammals in the stratum corneum

Question 23

Granular Glands

Answer 23

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)

Question 24

What kinds of Cutaneous Glands to birds have

Answer 24

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

Question 25

What keratinized regions are in birds

Answer 25

Beak, feathers, scales in legs, spurs, egg-tooth in birds and reptiles

Question 26

Structure of a feather (Contour Feathers)

Answer 26

• 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

Question 27

What are the types of feathers

Answer 27

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

Question 28

Contour feathers:

Answer 28

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

Question 29

Down feathers:

Answer 29

: reduced shaft, soft and fluffy, beneath the contour feathers to aid in insulation/thermoregulation

Question 30

Semiplume feathers:

Answer 30

cross btw down and contour feathers, they have a formed shaft but poorly developed barbules and hooklets

Question 31

Bristles feathers:

Answer 31

stiff w/ a few barbs on the calamus, around the mouth and eye and connected to nerve endings (serve a sensory function)

Question 32

Filoplumes feathers:

Answer 32

incredibly small, tuft of barbs at tip of shaft and also connected to nerve ending and serving a sensory function

Question 33

What are the major glands in mammals

Answer 33

• 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

Question 34

How do feathers develop

Answer 34

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

Question 35

How does hair develop

Answer 35

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

Question 36

What are the different types of scales

Answer 36

• placoid scales (denticles)
• Cosmoid scales (ancestral scale)
• Ganoid scales (found in Latimeria and Brachiopterygii)
• Leptoid scales (in most fishes)

Question 37

Placoid scales

Answer 37

(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

Question 38

Cosmoid scales

Answer 38

Scales of all 4 layers of bone found in primitive agnathans and primitive bony fishes but not found in any living fishes

Question 39

Scale bone layers

Answer 39

1. Lamellar bone (inner layer)
2. Spongy (vascular bone)
3. Cosmine = dentine bone-like material
4. Ganoin layer = enamel-like

Question 40

Ganoid scales

Answer 40

Lack spongy bone, has greater development of the ganoid layer and found in Latimeria and Brachiopterygii (gars, bichirs, and reedfishes)