SKIN OF VERTEBRATES :- FISHE,AMPHIBIAN,REPTILE, BIRD & MAMMALS. FUNCTION OF SKIN

1. K.G. ART’S & SCIENCE COLLEGE RAIGARH (C.G.)
SESSION - 2021
DEPARTMENT OF ZOOLOGY & RESEARCH CENTER
• SUBJECT :- COMPARATIVE ANATOMY OF VERTEBRATES.
SEMINAR TOPIC :- GENERAL STRUCTURE & FUNCTION OF SKIN IN VERTEBRATES.
GUIDED BY SUBMITTED BY
DR. R.K. TAMBOLI SIR. GIRJA PRASAD PATEL
M.Sc. III SEM. ZOOLOGY

2. Synopsis :-
• INTRODUCTION
• DEFINITION
• INTEGUMENT OR SKIN IN DIFFERENT CLASS OF CHORDATES:-
1. Fishes
2. Amphibians
3. Reptile
4. Birds
5. Mammals
• FUNCTION OF SKIN
• CONCLUSION
• REFERENCE

3. INTRODUCTION :- The words INTEGUMENT comes from a
LATIN words that means “to COVER”
Integument or skin is the layer of usually soft, flexible
outer tissue covering the body of a vertebrate animal.
It is a largest organ with respect to surface area of the
vertebrate body.
It is divided into two main layers, dermis and epidermis.
there are three main functions: protection, regulation, and
sensation. Its other functions are insulation, temperature
regulation, sensation, and the production of vitamin D
folates.

4. DEFINITION:-
The term of integument is applied- to the outer most protective
covering of the animal body, the skin and its various derivatives. Skin
also includes the conjunctiva of eyeballs and external surface of
eardrums. It is directly continuous with the mucous epithelial lining of
mouth, rectum nostrils, eyelids and urinogenital ducts.

5. • Skin in different class of Chordates:-
1. FISHES:-
• The skin of fish is made up of two distinct
layers an outermost layer the epidermis
& an inner layer dermis or corium.
• The epidermis originates from ectoderm
& the dermis derives from mesoderm layer.
Epidermis:-
The epidermis is several-layered but
simple thin & without typical stratum
corneum is an adaptation to life in water.
• Epidermis is quit rich in unicellular goblet or mucous gland cells secreting
mucous which reduced friction between body surface & water. protects
from fungal & bacterial infection & controls osmosis.

7. • A few multicellular epidermal glands, such as poison gland & light-
emitting organ or photophores, may also be found.
Dermis:-
• The dermis is typical but all the connective tissue fibbers forming it
run parallel to the surface & the present of neve cell.
• The presence of 5 types of dermal scales projecting above the
surface.
• The cartilaginous fishes{elasmobranchs} have placoid scales.
Chondrostei & Holostei have ganoid scales, while Teleostei have
cycloid & ctenoid scales. Cosmoid scales are known from extinct
crossopterygii.
• Pattens & brilliance of colouration are perhaps greatest in fishes than
in any other group of chordates.
• This is because of pigment cells called chromatophores & iridophores
containing guanin, which are found in the dermis.

8. 2.AMPHIBIANS:- Amphibians are transitional between aquatic &
terrestrial vertebrates.
• Skin of frog is smooth, moist, slimy, fitting loosely on body &
characterized by the presence of large flask-shaped mucous gland.
• Large subcutaneous space called lymph space separates the skin from
body wall.
• The skin of dorsal surface is thicker than the ventral.
Epidermis:-
• It is the thin outer ectodermal layer of stratified squamous epithelium
6 to 12cells deep.
• One or two outer most layer of cells from stratum corneum.
• Its cells are much flattened, dead, without nuclei & their cytoplasm
replaced by a horny protein, keratin.

9. • These cells secrete a kind of hormone which inhibits cell division in
stratum germinativum.
• This horny or keratinized layer is periodically moulted or shed in large
patches.
• Epidermis deeper layer of cells are irregularly polyhedral, forming
stratum germinativum.
• Its basal or innermost cells are cuboidal or columnar, which large
nuclei, called stratum Malpighi.
• It rests on a basement membrane.
• Cell of Malpighian layer undergo mitosis to produce new cells of
epidermis.

11. • Dermis:-
• The underlying connective tissue layer called corium or dermis,
continuous the major part of skin.
• It contains blood capillaries nerve & muscle fibres, vertical connective
tissue, pigment cells called melanophores or chromatophores & large
flask-shaped epidermal glands embedded in it.
• Each pigment cell is irregular in outline with branched processes.
Chromatophores have black melanin & yellow xanthin pigment in it.
• Colour change is produced by spreading or condensation of these
pigment in these cells.

12. 3. REPTILES:- reptiles are the first true land vertebrates & their
integument show many terrestrial adaptation.
Epidermis:-
The seven epidermal layer are:-
• 1st The stratum germinativum:- the deepest layer of living cells which
have the capacity for rapid cell division.
• 2nd to 3rd the clear layer & lacunar layer:- which mature in the old skin
layer as the new skin is growing beneath.
• 4th to 6th the alpha layer, the Mesos layer & the beta layer :- these
layer consist of cells which are becoming keratinised, with production
of two types of keratin {alpha & beta keratin}. These cells are thus
being transformed into a hard protective layer.
• 7th 0berhauthen layer:- which forms the toughest outermost layer of
keratinised, dead skin cell.

14. • Dermis :-
• The dermis, which is the deeper layer of connective tissue with a rich
supply of blood vessels & nerves.
• Dermis is provided with chromatophores, colour bearing cells that
give many lizards & snakes their colourful hues.
• Reptiles exhibit relatively few integumentary glands, with the
exception of scent gland for sexual attraction near cloaca in some
snake, femoral glands on the things of male lizards, & musk gland on
the musk-turtles & alligator.

15. 4. BIRDS :- skin of birds like that of other vertebrates, is composed of
stratified epidermis & dermis. But skin is thin & loosely attached to achieve
maximum freedom of movement for flight.
• The integumentary system is verry important in providing protection to the
birds from number of potential dangerous situation.
• The skin is composed, in the main, of two different tissues:-
• Connective tissue of the dermis & hypodermis where the cells are widely
spaced.
• Cellular stratified epithelium of the epidermis, where make up the horny
outer layer of the skin in & forms the feathers.
• The hypodermis connect with air sac respiratory system thus enhancing
thus the ability to fly. different skin types contain different amounts &
distribution of special compounds mainly collagen elastin & keratin.

16. • Epidermis:- modification of stratum corneum, other than feathers, include
horny sheaths of beaks. Scales are restricted to lower legs, feet, webs &
base of beaks.
• The epidermis consist of three separate layer:-
A. The flatted, horny cell layer:-the outer most layer.
B. The transitional layer:- joins the outer layer to the inner layer. It is here
that the cells formed in the third innermost layer are transformed into the
hard, horny type found in the outermost layer.
C. The columnar cell layer:- this is the innermost layer of the epidermis & is
the germinative layer where the cell of epidermis are formed.

18. Dermis:-
• The dermis is relatively thin & shows a uniform, microscopic structure.
• This is different to many other animal that have both densely & loose layer
of cells.
• The main component of the dermis is collagen with a small amount of
elastin.
Hypodermis :-
• The hypodermis contains fewer cells & is more loosely arranged than the
dermis.
• Fat is stored here in special adipose cells {adipose tissue is fat tissue}.air
space found in the.
• No skin gland occur in birds with the exception of a uropygial or preen gland
on tail.

19. • Mammals:- skin of mammals is elastic, water-proof, thickest of all
vertebrates & variously modified. the two layers, epidermis & dermis, have
reached their highest specialization in mammals.
{a} Epidermis:- The outer most layer of skin is known as the EPIDERMIS. It is
composed of many sheets of flattened, scaly Epithelial cells. This is a thin
outer layer of skin. Its layers are made of mostly dead cells.
• There are five distinct sub-layers of the Epidermis :-
1. Stratum corneum:- The outer most layer made of 25-30 layers of dead
flat keratinocytes. Lamellar granules provide water repellent action & are
continuously shed & replaced.
2. Stratum lucidum:- Only found in the fingertips, palms of hands,& soles of
feet. This layer is made up of 3-5 layers of flat dead keratinocytes.

20. 3. Stratum granulosum:- made up of 3-5 layers of keratinocytes, site of keratin
formation, keratohyalin gives the granular appearance.
4. Stratum spinosum :- appears covered in thorn like spikes, provide strength
& flexibility to the skin.
5.Stratum Basale:- the deepest layer, made up of a single layer of cuboidal
cells. Cells produced here are constantly divide & move up to apical surface.

22. • The epidermis made by 4 types of cells:-
{a}Keratinocytes:- Produce keratin protein a fibrous protein that helps protect
the epidermis.
{b} Melanocytes :- produces the brown pigment melanin. these are cell located
in the bottom layer of the skins epidermis & in the middle layer of the eye,
the uvea. Through a process called melanogenesis, these cells produce
melanin, a pigment in the skin, eyes, & hair.
{c] Langerhans cells:- Formed in bone marrow and move to the skin and
participate in immune response.
{d] Marker cells:- participates in the sense of touch. & connected to cells from
dermis

23. • Dermis :-
• The inner most thick layer of the skin composed of living cells.
• The dermis lies beneath the Epidermis & contains blood vessels,
nerve ending, gland, sense organs, smooth muscle & hair follicles.
• The arrector pili muscle is a minute muscle found in the dermal layer
of the skin.
• It is attached at the root of the hair, inside the hairs follicle.
• Under the control of the autonomic nervous system these tiny
muscles aid the body in temperature regulation
• Sensory nerves in nerve ending of the skin send messages to the
brain, which if necessary triggers contraction & relaxation of the
muscle.

24. Hypodermis or subcutaneous :-
• Another name for the hypodermis is the subcutaneous tissue.
• The hypodermis is not part of the skin & lies below the dermis.
• Its purpose is to attached the skin to underlying bone & as well as
supplying it with blood vessels & nerve.
• It consist of loose connective tissue & elastin.
• The main cell types are fibroblasts, macrophages & adipocytes.
• The hypodermis contains 50% of body fat.
• Fat serves as padding & insulation for the body.

25. • KINDS OF GLAND :-
{a} Sweat glands :-
These are large lumen glands associated with hair follicles.
They develop from same down growth that give rise to hair follicles.
The connection is retained & they are coiled tubular glands, sometimes
branched.
The secretory portion is in the dermis or upper hypodermis.
The secretory product is stored in the lumen.
There are also myoepithelial cells that are responsible for the expression of
sweat from the gland.
The duct is stratified cuboidal.
There is both thermoregulation sweating & emotional sweating.
Resorption of some mineral take place in the duct.
Myoepithelial cells are present in the duct.

26. {B} Sebaceous glands or oil gland :-
• Found in the skin of mammal & these gland secrete sebum.
• Sebum :- that is made of fat & the debris of dead fat-producing cells.
• These gland exist in humans throughout the skin except in the palms of the
hands & soles of the feet.
• Sebum acts to protect & waterproof hair & skin & can also inhibit the growth
of microorganism on skin.

28. 5. Function of skin :-
1.Protection :- the skin separated the animal from its external
environment & helps to maintain a constant internal environment.
• Protected the body against mechanical & chemical injuries which may
result from pressure, friction, blows, harmful gases & fluid.
• Skin derivative are like spine, claw ,nails, hoofs ,fur and feathers etc.
are the help to offence & defence.
• Skin pigment also protect against solar radiation.
2. locomotion:- Dermal fin ray in the fins of fishes & skin webs in the
feet of frog, turtles, aquatic birds etc. help in swimming in water.
• Feathers on wings & short tail of birds & cutaneous patagia or wings
of bat & flying lizard help in flaying.

29. 3. Secretion :- skin gland secrete substance having several uses :-
• Mucous gland – for aquatic animal skin moist slippery.
• Uropygial gland- in birds secrete oil for preening feathers.
• Oil from sebaceous gland in mammal lubricates the skin & hairs.
• Mammary gland – production & secretion of milk for nutrition of the young
etc.
4.Food storage:- Thick fatty layer of blubber under skin of seals & whales serve
as insulation as well as resave food. animal also accumulate subcutaneous fat
prior to migration.

30. 5. Temperature controls :- In warm-blooded animals, fur, feathers & insulate
& conserve body heat in cold climate.
• Sweat gland of mammal provide cooling by evaporation in summer. for
eliminating of heat, integumentary blood vessels dilate so that skin becomes
a radiator. for conservation of heat. the vessels constrict. These devices help
in homoiotherm or in the maintenance of constant body temperature.
6. Excretion :- excess of water, salt & urea are also eliminated in sweat. Gills of
marine fishes contain chloride-secreting cells. shedding of skin during ecdysis
also gets rid off some metabolic wastes.
7.Sensation :- cutaneous nerve ending other sense organs are stimulated by
touch, pain, change in pressure & moisture ,extremes of heat & cold &
chemicals etc.

31. 8. Sexual selection:- brilliantly coloured skin , antlers of male deer, long
tail coverts of peacock etc. lead to sexual dimorphism & also serve to
attract the females for mating.
9. some other function like synthesis of vitamin-D etc.
• Conclusion:-
• Integument or skin is the outer most protective layer of vertebrates
animal.
• It is a largest organ in surface of area and weight.
• Its provide the body structure and several function like:-protection,
thermoregulation, excretion , sensation etc.

32. • Reference :-
1. Comparative of vertebrates:- R. L. Kotpal
2. Vertebrates : - R. L. Kotpal (Volume II)
3. By internet.