the integument is the natural outer protective covering of an organism or an organ, such as its skin,  husk,  shell, or rind. The cutaneous Membrane (skin) And its derivatives (Exoskeleton) are together referred to as Integuments. Skin also includes conjunctiva Of eyeballs and the external surface of eardrums and it is directly continuous with the mucous epithelial lining of the mouth rectum, nostrils, Eyelids, and urinogenital ducts.

1. M. G. COLLEGE ARMORI DIST. GADCHIROLI
CLASS: B.SC. II SEM III
PAPER: I UNIT: IV
Topic: Comparative account of derivatives of
integuments - scales
By: prof. S. B. Kumre
(dept. of zoology)

2. ➢ integument is the natural outer protective covering of an
organism or an organ, such as its skin, husk, shell, or rind.
➢ The cutaneous Membrane (skin) And its derivatives (Exoskeleton)
are together referred to as Integuments.
➢ Skin also includes conjunctiva Of eyeballs and external surface of
eardrums and it is directly continuous with the mucous epithelial
lining of the mouth rectum, nostrils, Eyelids and urinogenital ducts.

3. FUNCTIONS OF INTEGUMENTS
❖ Protection: It separates the animal from external environment and helps to
maintain internal environment. 2. It protects the body from mechanical and
chemical injuries which results from Friction, pressure, harmful gases and fluids.
3.Protective derivatives such as scales, bony plates, feathers, hair etc. reduce the
force of injury, prevent excessive loss of body moisture and do not allow entry of
harmful bacteria and fungi and other foreign bodies. 4. Please plumage, bristles or
spines claws, nails, hoofs, antlers, horns etc. serve for offense and defense. 5. Skin
pigments also protect against solar radiation.
❖ Nourishment: skin synthesize vitamin F in the presence of sunlight and
calcium when dehydrocholesterol is converted into vitamin D.
❖ Dermal endoskeleton: animals like crocodiles, turtles and armadillo have
a dermal bony covering over the body to protect them from predators.

4. ❖ Locomotion: Skin is modified in the limbs of all animals for walking, running
swimming flying etc. Dermal fin Rays in the fins of fishes and skin webs in the feet
of frogs turtles, aquatic birds etc. Help in swimming. Pads in amphibia and claws
in amniotes on digit assist in climbing. Feathers on wings and short tail of birds
and wings of bats help in flying.
❖ Sensation/exteroception: skin functions as a sensory organ. Free nerve
endings are scattered in the demis of the entire skin. These nerve endings and
other sense organs are stimulated by touch pain change in pressure and moisture
heat and cold and chemicals etc. In their absence these animals may starve or
destroyed by an animals.
❖ Sexual selection: briliantly coloured skins, antlers of male deer, long tail
coverts of peacock, etc. lead to sexual dimorphism and also serve to attract the
females for mating.

5. ❖ Secretion: Mucous glands in aquatic Forms keep the skin moist and slippery. Oil from
sebaceous glands of mammals lubricates the skin and hair. Uropygial glands in birds secrete
oil for preening feathers. Mammary gland’s milk secretion nourishes the young ones.
Poisonous, bitter or offensive secretions ward off potential enemies. Odours of scent glands
attract the opposite sex. Tears from lacrymal glands wash the conjunctiva of mammalian eye
ball.
❖ Respiration: cutaneous respiration occurs in amphibians when they are living an aquatic
life. Many reptiles, such as sea turtles and sea snakes can also carry out some amount of
respiration through the skin.
❖ Brood pouch: brood pouch is a bag of skin that is usually attached to the belly in
marsupials. Some other animals such as sea horse, pipe fish and some amphibians develop
brood pouches for keeping their eggs or juveniles.

6. ❖ Food storage: Fat deposits in the adipose tissue of skin functions as stored nutrition
apart from conservation of body heat in almost all animals. For e.g.. Thick fatty layer of
blubber under the skin of seals and whales serves as insulation as well as reserved food. During
lean period when food is scanty, the stored fat is utilized to sustain life.
❖ Temperature control: In warm blooded animals, fur, feathers and scales insulate and
conserve body heat in cold climate. Sweat glands of mammals provide cooling by evaporation
in summer. Thick layer of fat under the skin of whales sea lions, polar bears insulating the body
from outside subzero temperature.
❖ Excretion: excess of water, salts and urea are eliminated in sweat. Many toxic substances
evaporate through the surface of skin. Sweat glands serve as excretory organs that excrete
toxins out of the body. Gills of marine fishes contain chloride secreting cells. Shedding of skin
during ecdysis also gets rid off some metabolic wastes.

7. DERIVATIVES OF INTEGUMENT:
❖ Chordate skin is characterized by having two layers, the outer epidermis which is derived
from the embryonic ectoderm and the inner dermis, a derivative of mesoderm.
❖ Non- chordate skin lacks dermis except in echinoderms.
❖ Epidermal derivatives: these are formed by the epidermis and comprise: 1. epidermal
glands and 2. hard horny structures
❖ Dermal derivatives: these arise from dermis and comprise bony or dermal scales,
plates or scutes, fin- rays and antlers etc.
Epidermal scales:
❖ All the hard horny structures develop by the accumulation of a scleroprotien known as
keratin, in the cells of epidermis. Such cells are said to be keratinized or cornified, and they
become dead. They form hard horny exoskeletal structures like scales, beaks, horns, claws,
hoofs, feathers, hairs etc.
❖ Reptiles have outer covering of horny epidermal scales that prevents water loss through
skin surface. In lizards scales are thin, small, overlapping and modulated in small pieces.
❖ In snake the scales are overlapping, enlarged on head, called shields and on ventral
surface called scutes, which assist in locomotion.

8. ❖ Crocodilians and turtles have large, thick, rectangular scutes. Scutes of crocodilians are
shed or sloughed in patches at intervals.
❖ In birds small epidermal scales are present o the lower leg, foot and base of the beak.
❖ Reptile-like epidermal scales occur in some mammals also, such as on the feet and tails
of rats and beavers etc.

9. DERMAL SCALES:
❖ Bony structures develop within the dermis and are mesodermal in origin.
➢ Dermal scales of fishes: In fishes the overlapping epidermis wears off so
that the scales become exposed forming the exoskeleton. There are Five types of
dermal scales depending on their structure, 1) cosmoid scales occurred in lobe finned
fishes(crossopterygii) 2) placoid scales are characteristicof elasmobranches(
chondrichthyes) 3) ganoid scales are present in ganoid fishes 4) cycloid and ctenoid
scales are characteristic of modern teleosts.
cosmoid sclale

10. ➢ Dermal scales of tetrapods: Dermal scales or bony plates measurig 1 to 2
mm are called osteoderms are found embedded in the dermis below epidermis, in some
amphibia. Reptiles have traces of bony dermal armour of their ancestors. Lizards
exhibit small dermal scales. Crocodiles have many oval plates embedded in the dermis
of their back and neck. In turtles below horny epidermal scutes, are present large bony
plates.
• Dermal fin rays: supporting the fins of fishes are long, flexible fin rays
embedded in dermis. In chondrichthyes, they are horny, hair like made of fibrous
connective tissue and called ceratotrichia. In osteichthyes, they are branched made of
a series of segments or scales, and called lepidotrichia. Unsegmented sharp and spine
like fin rays are termed actinotrichia.

11. HORNS :
 Horns are found in mammals like
Artiodactyle and Perissodactyle only.
They are present on their head and
form organs of offense and defense.
 True horns: True or hollow horns
usually occurs in both the sexes in
goats, cows, sheep and buffalo.
Unbranched, cylindrical and tapering.
They are permanent and grow
continue throughout the life and are
never shed.

12.  Prong horns: The horns formed by a small
central permanent bony core arising from frontal
bone and covered by a thin hollow and horny
epidermal horn. But the horny sheath of a prongs an
it is shed every year.The permanent bony core
becomes the base around which a new horn is
developed the following year.
 Antlers: Antlers are found in deer family. They
found only on males but in reindeer. Antlers are
annual growths, and it is a branching solid
outgrowth of connective tissue and connected to the
frontal bone of skull. Deposition of calcium salts
makes the antler hard. During growth it is covered
with hairy skin or velvet, then velvet wears off
exposing the naked antlers. When breeding season is
over, the antlers are also shed and new antlers
develop.

13.  Giraffe horns: Horns of giraffe are
stunted, unbranched and permanent
antlers present in both the sexes. Each
consists of a short bony dermal core,
projecting from frontal bone and remains
covered with simple unmodified skin or
velvet which is never shed.
 Hair horns: Hair horns or fibre horns
are found in rhinoceros of both sexes.
Indian rhinoceros has a single horn, while
the African species has two, one behind the
other. These horns are entirely made of
thick hairy and keratinized epidermal
fibres fused together. These are permanent
structures and if broken they again grow
out.

15. THANK YOU