Integument
Updated 4 November 2004
B.
Boundary between organism and
its environment; important!
C.
Numerous functions: physical protection,
barrier to foreign materials (disease), excretion, water balance, respiration,
temperature regulation, sensory reception, locomotion, sensory reception, UV
shield, adaptive coloration, etc.
D.
Little known about skin of
extinct forms
Integument structure: 2 major layers with basement membrane in between; slide
1
A.
Lower dermis (meso); relatively thick, few derivatives in terrestrial
vertebrates (fish)
B.
Upper epidermis (ecto); relatively thin, many derivatives in terrestrial
vertebrates (few in fish)
C.
Epidermis: 2 major layers
1.
Lower stratum germinativum (living germ layer) - differentiate and die
2.
Upper periderm
(dead layer) or stratum corneum if cornified/keratinized (primarily terrestrial vertebrates – slide 2,
w/lipids); shed periodically (molting or ecdysis; slide 2)
Derivatives of epidermis (numerous):
A.
Local thickenings (temporary
or permanent) - calluses, foot pads, friction ridges, nuptual
pads (ischial callosities), warts
B.
Scales (amniotes) - large scutes (turtles, crocodilians), smale
scales (squamates, birds, some mammals, e.g., beaver
tail); modified scales (rattle, spines, etc.)
1.
Modified: nails (flattened,
arboreal primates [e.g., aye-aye]; hoofs (cylindrical, ungulates)
D.
Beak - birds, turtles, several
extinct reptiles (substitute for teeth)
E.
Baleen - (“whalebone”; not
bone)
F.
Horns - keratin sheath over
bony core (Bovidae); not shed, not branched
1.
cf antlers? not epidermal; frontal bone outgrowth, branched, shed
annually (Cervidae)
G.
Feathers - birds (extremely
thin skin, thick derivatives (long teeth in bird eaters)
1.
Function: insulation
(endothermic, erector muscles), flight surface; shed 1-2 times/yr, (gradually
or all at once); feather tracts plumage structure: derived from scales
2.
Structure (slide
4): rachis, calamus (in feather follicle), vane
(barbs, barbules, barbicels); ratites®no barbicels (hairlike)
3.
Types: contour feather: as
above; down: no rachis or barbicels; bristles: no vanes
4.
Pitohui (poison feathers - repel predators)
H.
Hair - mammals (thick skin)
1.
Function: insulation
(endothermic, erector muscles), shed 1-2 times/yr; more uniform distribution on
body (re feathers); pelage
2.
Structure (slide 5):
shaft, root (in hair follicle); medulla (air spaces), cortex, cuticle
3.
Types: vibrissae, guard hairs,
underhair (=fur)
I.
Glands - in all vertebrate
classes; derived from epidermis (may sink into dermis)
1.
Fishes
a.
mucous (slime) glands, uniform
distribution; osmoregulation (no stratum corneum)
b.
serous (elasmobranches)
c.
misc: poison glands (associated w/ spines), light organs (photophores)
2.
Amphibians
a.
mucous (uniform distribution,
continuous secretion); respiration, nest building
b.
granular (toxic, localized distribution
(e.g., warts), occasional secretion)
3.
Reptiles
a.
scent (sexual, social behavior)
b.
poison (modified salivary
glands)
c.
salt glands
4.
Birds
a.
uropygial gland (dress feathers, synthesize vitamin D)
b.
salt glands
5.
Mammals
a.
wax (ear)
b.
sebaceous (associated w/ hair
follicles, lips, nipples, genitalia)
1)
dress hair, reduce desiccation
c.
sweat (in some, especially
large primates); non-uniform distribution (e.g., dog)
1)
thermoregulation (relative to
size - endothermic); excretion, urea
d.
scent highly developed (conchae)
1)
mammals primarily olfactory;
location various (e.g., undulates-feet; bats-face; weasels-anal)
e.
mammary (modified sweat
glands)
1)
secrete milk (nourish young)
2)
variable structure:
3)
monotremes: diffuse, no nipples, functional in both sexes
4)
therians: localized, concentrated (2-24 nipples; chest®inguinal)
A.
Fibrous connective tissue
(“leather”)
B.
Less variation relative to
epidermis, fewer derivatives
C.
Variation in thickness, vascularization, fat storage, muscle control
D. Dermal bone in fishes and some terrestrial vertebrates (most dermal
bones of tetrapods have been lost or sunk deep into
the body to become part of the endoskeleton); major exceptions - turtles
(carapace/plastron), armadillo, glyptodonts
1. Dermal armor - ostracoderms
& placoderms (slide 6)
2. Placoid scales – chondrichthyans
(slide
7)
3. Cosmoid scales - extinct sarcopterygians
(reduced in recent forms) (slide 8)
4.
Ganoid scales -
extinct actinopterygians (reduced in recent forms) (slide 8)
5.
Teleost scales -
teleosts (slide
8, slide
9)
Integument coloration
C.
Endotherms - melanophores only (mostly in
epidermis)
1.
May transfer melanin to
non-cellular structures (e.g., hair, feathers)
2.
May contain addition pigments
(not cellular): carotenoids, cranes rusty (iron);
copper (turacos - green)
3.
Constant color or relatively
slow color change (wear, molt®seasonal); man: tan and lose it (shed)