Integument

Question 1

vocabulary

Answer 1

integument = skin

integumentary system = skin + skin derivatives (hair, hooves, nails, etc.)

Question 2

Integument functions

Answer 2

• protection (UV radiation, mechanical injury)
• water regulation/osmotic balance
• gas exchange (amphibians)
• sensory reception/detection (pressure,cold)
• thermoregulation (birds, mammals)
• locomotion (hooves, nails, claws)
• pheremonal secretions for attractions or repulsion (musk glands)
• fat storage (in hypodermis)
• homeostasis (mineral reservoir in bony scales)
• defense/immunity – anti-pathogen (human skin surface ph ~4-6.8; macrophages; Leydig cells in amphibians; mucus in fish)

Question 3

Integument components

Answer 3

epidermis
dermis
basement lamina
hypodermis/superficial fascia

Question 4

basement lamina

Answer 4

acellular; glycoprotein + collagen and reticular (branching, net-like) fibers

Question 5

hypodermis/ superficial fascia

Answer 5

loose connective tissue and adipose; anchors dermis to underlying muscle

Question 6

Epidermis

Answer 6

• boundary between organism and environment
• stratum germinativum
• stratum corneum
• all cells in stratum corneum dead in terrestrial vertebrates

Question 7

stratum germinativum

Answer 7

mitotic layer

Question 8

stratum corneum

Answer 8

uppermost layer of cells

Question 9

epidermal cells

Answer 9

• new epidermal cells arise from mitosis in stratum basale

- older epidermal cells form keratin; ultimately self destruct

Question 10

keratin

Answer 10

hydrophobic protein

Question 11

keratinocytes

Answer 11

two types:
alpha = soft = hair, fingernails
beta = hard = hooves

dead cells, periodically shed
thicker in areas of friction (callus) (see Fig 6.6)

Question 12

no stratum corneum in fish (see Fig 6.7)

Answer 12

all epidermal cells alive

less need for protection from environment because always aquatic

Question 13

muscle or blood vessels or bone in epidermis?

Answer 13

no! no muscle or blood vessels in epidermis; no bone ever develops in epidermis

Question 14

Epidermal derivatives

Answer 14

unicellular mucus glands (club cells and granular cells) in epidermis of fishes

multicellular glands in tetrapods (sweat glands, sebaceous glands)

feathers, nails, claws, hair-horns, antlers

baleen plates

Question 15

Baleen plates

Answer 15

suspended from the upper jaw whales in clade Mysticeti (Blue Whale group); filter feeding krill

Question 16

epidermal scales of reptiles and mammals

Answer 16

usually without bony support in the underlying dermis

Question 17

epidermal scales

Answer 17

folds of surface epidermis; heavily keratinized

Question 18

scute

Answer 18

enlarged epidermal scale

Question 19

Dermis

Answer 19

present in cephalochordates (lancelets) and craniates

attached to the epidermis via basement lamina

thicker in areas of friction; thinner at joints and regions of neural sensitivity

fibroblasts secrete collagen and elastic fibers

pigment cells (chromatosphores) in dermis or at interface between dermis and epidermis

blood vessels and nerves present, unlike epidermis

membrane bone (dermal bone) often present - fish scales, armadillo, turtles, etc.

connective tissue fibers are most conspicuous aspect of dermis

arrangement of collagen “woven” into distinct layers = plies

Plies with alternating orientation: warp (longitudinal) and weft (horizontal)

Question 20

Fig 6.5

Answer 20

flexible bias of skin in fish is oriented at 45 degrees to the body length to accomodate lateral bending during swimming

this arrangement keeps the skin flexible but tight so that surface wrinkling does not occur and turbulence is not induced in the streamline passing over the body as the fish swims

Question 21

dermal derivatives

Answer 21

dermal “armor” of ostracoderm fishes

“fish” scales

bony armor of armadillos

osteoderms of crocodylians and turtle shells

Question 22

“Fish” integument

Answer 22

different cell types that produce mucus:

• goblet cells (upper epidermis)
• granular cells
• club cells/alarm cells - also produce chemicals inducing fear/alarm behavior in conspecifics… may be important in reducing exposure to pathogens

Question 23

Fish Scale Types

Answer 23

ostracoderm scale
placoid scale
cosmoid scale
ganoid scale
teleost scale

Question 24

Ostracoderm Scale

Answer 24

dermal armor

enamel (outermost)
dentin
vascular bone
lamellar bone (innermost)

Question 25

Placoid Scale

Answer 25

``` only in chondrichthyes, thus no dermal bone "denticles" pointed at surface enamel dentin pulp cavity ```

Question 26

Cosmoid Scale

Answer 26

``` present in coelacanths (lungfish) enamel dentin (very thick = cosmine) vascular bone lamellar bone ```

Question 27

Ganoid Scale

Answer 27

``` in primitive actinopterygeans (ray finned fishes) bichirs and reedfishes also in lepisosteiformes (gar) ganoin = enamel vascular bone (absent in gars) lamellar bone ```

Question 28

Teleost scale (cycloid and ctenoid)

Answer 28

thin acellular, lamellar bone no enamel, dentin, or vascular bone possess circuli (=concentric rings); new circuli laid down as fish ages/grows annual cycles; fish aging techniques

Question 29

Tertrapod integument

Answer 29

keratinization; stratum corneum (cornified layer; dead cells) lipids often on skin surface - keratinized cells + lipids = waterproofing multicellular glands in integument more common glands reside in dermis; ducts

Question 30

amphibians

Answer 30

moist glandular skin; gas exchange epidermis with mucus glands, Leydig cells granular glands (release toxins) present; may be abundant nuptial pads on limbs or digits during breeding season - raised pigmented callus

Question 31

non-avian reptiles

Answer 31

much keratinization; associated with terrestrial environs epidermal scales = folds in epidermis hinge = junction between scales; flexibility skin shedding dramatic in squamates: ecdysis; outer and inner epidermal generations rest --> renewal --> shed --> rest turtles and crocodylians don't show squamate pattern not many skin glands in reptiles; if present, function is mate attraction/defense femoral glands in "lizards" musk glands in turtles (usually near bridge connecting carapace and plastron) and crocodylians (along lower jaw margin, cloacal region)

Question 32

aves

Answer 32

epidermal scales on feet/legs feathers = homogs of epidermal scales in squamate reptiles (Lepidosauria) few skin glands in birds - uropygial gland (preening) - salt glands in marine species

Question 33

mammals

Answer 33

Notable features: - hair - variety in epidermal glands - thicker dermis than other craniates - hypodermis is common fat reservoir continuous exfoliation of upper stratum corneum dermal bone --> endoskeleton components: pectoral girdle and skull contributions dermal bone --> dermal scales in armadillos and other species

Question 34

Two major gland types

Answer 34

1. sebaceous = releases sebum into hair follicle; ductless | 2. sudoriferous (sweat) glands = with ducts to surface, in less hairy areas, absent in cetaceans (marine mammals)

Question 35

scent glands

Answer 35

modified sweat gland or sebaceous gland intraspecific communication; pheromones or defensive signals "odors" at well-maintained mammal sections of zoos anal glands in canids and felids

Question 36

mammary glands

Answer 36

modified sweat gland milk release = lactation no nipple/teat taken into mouth: - licked - functional in male and female monotreme (egg-laying mammals) teat vs. nipple: teat = ducts do not open directly to surface, they empty into a chamber known as cistern