Transcript VERTEBRATE INTEGUMENTARY SYSTEM

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The integument consists of the skin and its
derivatives: hair, horns, nails, hooves, claws,
feathers, and scales.
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The skin of two animals or different parts of the
same animal can look quite dissimilar depending on
its color, thickness, or types of derivatives that it
produces.
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Despite these different appearances, the basic
structure of all skin is nearly the same. It consists of
two major layers: epidermis, an outer layer that is
subdivided into several other layers and the dermis,
a connective tissue layer
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Underneath the skin is the hypodermis (or subcutis)
which may consist of adipose cells, glands or bone.
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Skin derivatives may be waterproof, abrasionresistant covering that can be used for insulation,
protection, weapons, locomotion
The skin or the derivatives may be colored for
camouflage, thermoregulation, or communication.
The skin contains receptors for cutaneous sensation.
Maintains water balance, Vitamin D synthesis
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Superficial layer that
may be divided into
several regions
Contains numerous
types of glands that
may secrete mucus,
slime, poisons,
enamels,
pheromones,
photophores, etc.
Various kinds of
derivatives arise
from cornified layer
of tetrapod
epidermis
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FISHES and AQUATIC AMPHIBIANS:
Mostly unicellular goblet and granular cells that
secrete mucus and other substances, e.g. alkaloids,
toxins or nutritious mucus (eaten by hatchlings)
Teleosts have PHOTOPHORES or light-emitting
multicellular glands (luciferase luciferin)
TETRAPODS
Morphologically varied (simple or compound,
saccular, tubular, or both)
Secretions could be
merocrine (intact cells, e.g.
sweat glands), holocrine
(cellular, e.g. oil glands), or
apocrine (intermediate, e.g.
mammary glands)
MUCOUS GLANDS - loss maybe due to thick stratum
corneum; retained only in lubricated surfaces of mammals
GRANULAR GLANDS- secrete toxic or irritating alkaloids;
chiefly located on back and feet (e.g., femoral glands of male
lizards form temporary spines to hold female); absent in birds
and mammals
OIL GLANDS -water-repellant secretion of avian uropygial
glands is transferred to feathers during preening
SEBACEOUS GLANDS- alveolar glands that secrete the oily
sebum, usually exuded into hair follicles; ceruminous glands
of ear canal secrete cerumin; Meibomian glands moisten eye
conjunctiva
SUDORIFEROUS GLANDS- coiled tubular glands that extend
deep into the dermis; thermoregulators
SCENT GLANDS- pheromones secreted by sebaceous and
sudoriferous glands
MAMMARY GLANDS- compound alveolar glands arising
from milk lines that spread beneath the dermis, with
supernumerary nipples forming above patches
Milk letdown is
under neurohormonal
control
Marsupials
secrete milk
from modified
sweat glands
on surface of
hair tufts in
the absence
of nipples.
Keratinized outer layer, rare in aquatic forms, except for
cornified spines and teeth in buccal cavity of
cyclostomes and anuran tadpoles; mostly found in skin
derivatives of tetrapods that help prevent dessication
Found only in amniotes; overlapping folds in
squamates; large polygonal scales called scutes are
found on snake belly and turtle’s plastron.
Horny scales of birds are overlapping plates of
keratinized epidermis.
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Claws first appeared
in basal amniotes and
persisted in birds and
in most mammals.
Claws evolved into nails
in primates, and into
hoofs in ungulates;
usually worn down by
abrasion, except squamates which shed them.
Claws and nails are local modifications of skin, as
can be seen in their retention of epidermal, dermal
and subcutis layers.
Claws serve primarily to protect underlying tissues,
but are also used for scratching, digging or as a
weapon.
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Basic structure consists
of a horny dorsal plate
(unguis), and a softer
ventral plate (subunguis
or sole)
Partially surrounded by
the unguis in ungulates
is a softer pad, the
cuneus.
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Are highly specialized epidermal structures that
have evolved from the scales of reptiles.
The color of feathers serve as camouflage and to
protect birds from predators.
The color of feathers serve to communicate sex
type. This is called sexual dimorphism when the
male and female of a species display different
plumages.
Feathers repel water with the aid of the uropygial
glands' oily secretions rubbed over the body during
preening.
This is particularly important in waterfowl, where oil
spills saturate the feathers and destroy the bird's
delicate protective covering.
CONTOUR FEATHERS- give a bird its general shape
Each vane consists of barbs, barbules, flanges and
hooklets that interlock with the flanges on the next barb.
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FLIGHT FEATHERS- contour feathers specialized for
flight.
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DOWN FEATHERS- small, fluffy feathers lying
underneath and between contour feathers; short
calamus, barbs lack hooklets
FILOPLUMEShairlike feathers,
few barbs and
barbules at the tip;
follicles are richly
supplied with nerve
endings.
BRISTLESresemble filoplumes
but lack terminal
barbs; screen eyes,
ear and nasal
openings of foreign
matter
DERMAL PAPILLA- mound of dermal mesodermal cells
that indents the undersurface of the epidermis and
induces mitotic activity in the basal layer.
FEATHER PRIMORDIUM- pimple-like elevation on
epidermis resulting from growth of dermal papilla,
which soon becomes
vascularized
FEATHER FOLLICLE- a pit
lined with epidermis that
develops around base of
feather primordium; at the
base of a feather follicle is a
growth zone that pushes the
distal tip of the growing feather, now a feather sheath.
PIN FEATHER- growing feather in its sheath, which eventually
splits open to stretch out barbs and enable shaft to elongate.
Dermal papilla dies and becomes pulp, leaving an opening,
the inferior umbilicus. New feathers may arise from
reactivated dermal papillae.
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Feather
follicles are
disposed on
feather tracts
called pterylae.
Inserting on
the walls of the
follicles are
smooth erector
muscles
(arrectores
plumarum)
which enable a
bird to fluff its
feathers.
HAIR consists of dense keratin from cornified cells,
trapped air vacuoles, and varying quantities of
melanin. Cells are produced by the germinal
epidermis at the bulb of the hair follicle.
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The bulb encloses the dermal papilla; at its root, hair
cells cornify; remainder of hair is known as shaft. A
membranous cuticle covers each hair, composed of
thin,
transparent
cornified
squamous
cells arranged
like shingles
Coarse hairs
contain a
medulla,
composed of
irregular,
shrunken
cornified cells.
When the
arrectores
pilorum, a
smooth muscle
that is inserted
on the wall of
the hair follicle
contracts,
gooseflesh
results, or
gives the
carnivore its
ferocious
appearance.
Guard hairs are associated with sebaceous glands that
help them waterproof the skin. Wool hairs or underfur
are good insulators. Vibrissae are primarily tactile.
Guard
hairs
Underfur
Vibrissae
BOVINE HORNS (cows)
and PRONGHORNS
(antelopes)- consist of a
core of dermal bone
and sheath of horn;
antelopes annually shed
their branched and
horny covering
GIRAFFE HORNS- stunted antlers that remain in velvet
throughout life; also paired and protrude from the
frontals, but they are permanent, unbranched
HAIR HORNS- rhinoceros; composed of agglutinated
keratinized hair-like epidermal fibers resting roughened
area of nasal bone; not shed
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ANTLERS are
dermal bone
attached to the
frontal bone.
Deer antlers
develop in males,
starting growth
covered in
velvety hair,
which are
rubbed off at
maturity,
exposing naked
bone
Males shed them
off after rutting
season.
BALEEN- whales;
whalebone plates in
oral epithelium, with
fringes that strain
food out of the water
passing through them
RATTLESrattlesnake; rings of
horny stratum
corneum attached to
tail after each molt.
COMBS- roosters;
covered with thick,
waxy stratum
corneum
BEAKS- the bird beak is
the functional
counterpart of the lips
and teeth of mammals.
It is covered with horny
sheath, covering both
the upper and lower
jaws. It grows
continuously throughout
the lifetime of a bird.
The shape, strength and
organization of the beak
varies depending on
whether it is on a bird of
prey, a seed-eater, or a
fish-eater.
ISCHIAL CALLOSITIESmonkeys and apes; for
sitting
KNEE PADS- camels;
for kneeling
TORI or APICAL PADScats; epidermal pads
for “pussyfoot” walking
CORNS and
CALLUSES- temporary
thickenings where
stratum corneum is
subjected to unusual
friction
Consists of collagenous connective tissue, blood vessels,
small nerves, pigment cells, lymphatics, naked and
encapsulated exteroreceptors, bases of multicellular
glands, hairs or feathers and their erector muscles,
chromatophores
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Has an ancient
and persistent
potential to form
bone, e.g.
armored fishes
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Generalized
pattern consist
of lamellar bone,
Ostracoderm skin
spongy bone,
dentine (with spiny elevations called denticles), and
an enamel-like substance on surface.
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Dermal armor was protective, but is also a reservoir
of calcium and phosphates
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Large plates gave rise to thinner fish scales, or parts
of the skull and pectoral girdle skeleton
Scales are overlapping dermal plates of bone covered
with epidermal tissue. 4 types are found:
1. PLACOID- same as paleoniscoid scales, but
arising from the bony plate is a specialized denticle;
may have given rise to gnathostome teeth; found in
elasmobranchs
2. RHOMBOID- retain primitive
4 layers of dermal bone;
Osteichthyans
a. COSMOID- cosmine is not a tissue but a complex
canal system associated with dentine and
enamel layers; found
in Sarcopterygians,
absent in modern fishes
b. GANOID- ganoin is a form of enamel. The
paleoniscoid type is found in Actinopterygians
(Polypterus), while some Neopterygians (Amia
and gars) lost the spongy and dentine layers.
3. ELASMOID- formed from thin lamellar bone with a
fibrous plate; flexible and transparent; most teleosts
c. CTENOID- comblike free border
d. CYCLOID- Amia, Latimeria and Dipnoi
ARMADILLOS- small polygonal bones
united and extending to midventral line.
CROCODILIANS- oval osteoderms at
the back, with cornified crests
TURTLES- scales compose the
carapace and plastron
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CHROMATOPHORES- permanently branched dermal
pigment cells; all are derived from neural crest.
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Melanophores- melanin (brown) granules in cytoplasmic
organelles called melanosomes; melanocytes contain
melanin granules in striated muscle and meninges
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Lipophores- lipid-soluble; consist of: xanthopores
(yellow) and erythropores (red)
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Iridophores- contains guanine, a prismatic substance
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Physiologic color changes are reflexive and result from
movement of pigment granules into or out of the processes.
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Dispersal of pigment granules is under control of
neurotransmitters or hormones (intermedin and melatonin).
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Morphologic color changes are slow and depend chiefly on
seasonal pigment synthesis.
Lack scales.
Hagfishes are also called “slime eels” due to
abundant unicellular mucous glands in
mutilayered epidermis.
Horny denticles in buccal funnel and cornified
teeth are periodically shed and replaced.
Dermis is thin, but tough due to interwoven
collagenous CT.
Contains many melanophores which adheres
to underlying body musculature.
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Ancient placoid scales have bony basal plate in the
dermis, and projects with a spine on epidermis,
giving it a sandpaper texture.
Epidermis has thicker layers than agnathan skin;
dermis is composed of 2 well-defined layers.
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Unicellular cells are less abundant; some goblet
cells are modified to secrete toxins.
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Few multicellular
glands, limited to
base of male claspers
Photophores
invade dermis, and
lose connections with
epidermis.
A denser continuous
sheet of melanophores on the back epidermis and
less denser sheet on belly makes a shark less visible
from above and below the water.
Chimaeras have slippery skins, having lost their
scales, and more mucous glands.
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Unicellular epidermal
mucous glands; a few
multicellular glands,
such as granular glands
that secrete poisonous
alkaloids
Deep sea forms have
photophores that permit
species recognition, warnings or lures
Dermis of Polypterus and gars contain ancient ganoid
scales; modern teleosts have cycloid or ctenoid scales,
or both.
Scaleless teleosts develop abortive embryonic scales.
Scales are absent.
Abundant epidermal
multicellular mucous
glands make the skin moist
and slimy; granular glands
abundant in toads.
Epidermis has incipient stratum corneum, except in toads
where a layer of cornified cells impede dessication;
cornified appendages rare, except in horny teeth of
tadpoles.
Dermis is attached to underlying musculature, but anurans
have abundant subcutaneous lymph sinuses.
Caecilians and a few tropical toads have tiny bone scales in
the back.
Thick stratum corneum with
variety of specialized cornified
structures: scales, scutes,
beaks, rattles, claws, plaques,
and spiny crests, which maybe
periodically shed by ecdysis.
Dry skin, with few
integumentary glands: granular
glands have protective or
pheromonal secretions.
Dermis has bony deposits
ranging from osteoderms to
large bony plates with
prominent cornified crests
(absent in snakes).
Epidermis and dermis are delicate membranes loosely
attached to underlying muscles, making skin mobile,
except on feet and head where scales, spurs, claws and
horny beaks are found.
Integumentary glands are absent except for the
uropygial gland at
base of tail.
No osteoderms
present, except the
spur of dermal bone
in male game fowls
on each ankle, fused
to the metatarsus.
Thickened epidermis consists of 3 strata: stratum
corneum, stratum granulosum and mitotic stratum
germinativum. The stratum lucidum is a 4th layer
present in epidermal soles and palms.
Epidermal glands have greater functional variety:
sebaceous (secretions such as mammary glands), or
sudoriferous (sweat glands).
Cornified structures
include hair (modified into
bristles, vibrissae, quills),
scales, claws, horns.
Dermis is thicker than
epidermis due to presence
of many hair follicles,
erector muscles, glands,
supportive CT, encapsulated sensory nerve endings
and greater vascularity.
Skin is separated from underlying muscle by loose CT
called superficial fascia, with adipose tissue.
Care for the mammalian
integument:
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