Integument presentation

1. Comparative Anatomyof
Vertebrates
Integument and its derivatives
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By- Sanju Sah
St. Xavier’s college, Maitighar, Kathmandu
Department of Microbiology

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Integument
Integument: The skin and its derivatives
Skin: External body covering, continuous with the mucus
eye-
membrane lining of buccal cavity, rectum, eyelids,
conjunctiva and urinogenitalduct.
Barrier between external and internal environment .
The type of external environment whether aquatic or
terrestrial, influences the characters ofskin.
Evolution of vertebrate integument is correlated with the
transition of vertebrates from aquatic to terrestrial
environment.

3. General structure of Integument
• Vertebrate skin bears 2
layers: Epidermis and
Dermis.
• Relative abundance of two
layers depends on
environment.
• Epidermis and dermis are
closely united but differ
greatly in their nature and
origin.
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VS of skin of a Mammal

4. Epidermis:
• It is the outer layer; derived from embryonic ectoderm.
• It is stratified squamous epithelium (multilayered).
• Lowermost layer resting on basement membrane is a layer of columnar living
cells called Stratum germinativum or stratum Malpighi.
• Cells of stratum germinativum divide mitotically forming upper layers.
• Outer region of many layers of
flattened (squamous) keratinized
cells is stratum corneum.
• Keratin: a kind of tough, insoluble
and waterproof protein.
• Keratinization: replacement of
cellular cytoplasm by keratin.
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5. 5
Epidermis (Contd.)
• Stratum corneum provides protection against mechanical and
chemical injuries, fungal/bacterial infection and loss of body
moisture.
• Cells of stratum corneum are periodically moulted.
• It is thin, bearing mucous glands in aquaticvertebrates.
• It is thicker in terrestrial vertebrates with scales, feathers, hairs,
nails, claws, horns etc.
• Epidermis is separated from dermis by a thin and noncellular
bilayered basement membrane made of glycoproteinous
substance (2 layers- basal lamina + reticular lamina).

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Dermis/Corium:
• It is thicker.
• It bears fibrous connective tissue, blood vessels, lymph vessels,
nerve fibres, sensory corpuscles, white collagen fibres and
yellow elastic fibres.
• It also bears some branched/stellate cells called
Chromatophores.
• Chromatophores are of three types:
- : contain brown to blackmelanin.
- Lipophores/Xanthophores: contain yellow-red fattypigment.
- Iridocytes/Guanophores: contain crystals of guanine which
refract light.

7. • Skin is attached with underlying muscles by areolartissue
(hypodermis).
Evolutionary trend of skin:
- in anamnia: decrease in
thickness allowing greater
mobility and in amphibians
permit cutaneous respiration also.
- in amniotes:
progressively thicker (the largest
organ in mammalian body) to
prevent loss of water and to
retain the body heat.
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Major Functions of Integument
1. Protection
• Against mechanical and chemical injuries
• Against loss of moisture
• Against bacterial/fungal infection
• Spine, claws, nails, hooves, horns etc. serve for offence and
defense.
• Protective colouration serves to escape from enemies.
• Against solar radiation.
2. Secretion
• Mucous glands, poison glands, uropygial glands in birds,
sebaceous glands, sweat glands, scent glands, mammary
glands, lacrymal glands, ceruminous glands etc.

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Major Functions of Integument
3. Thermal regulation
• Fur, feathers, scales etc insulate and conserve body heat in cold
climate.
• Sweat glands provide cooling by evaporation.
• For loss of heat- dermal blood vessels dilate, increase blood
flow. Skin becomes radiator of heat and rate of perspiration
also increases.
• For the conservation of heat- dermal blood vesselsconstrict.
4. Locomotion
• Fin rays of fishes; webs of frogs, turtles, aquatic birds etc.
• Adhesive pads, claws, digits etc on climbing and feathersof
wings, patagia on flying.

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Major Functions of Integument
5. Excretion
• Excess of water, salts and urea- eliminated in sweat.
• Gills of marines fishes bear chloride secreting cells.
• During ecdysis, shedding of skin also gets rid off some
metabolic wastes.
6. Storage
• Stores fat in blubber of whales and seals
• Fat is stored in subcutaneous fatty layer of the animals prior to
hibernation and aestivation.
• Fat deposit on the hypodermis also helps in insulation and acts
as cushion.

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Major Functions of Integument
7.Sensation: skin bears sensory corpuscles sensitive to touch,
pain, pressure, temperature, moisture, chemicalsetc.
8.Sexual selection: brilliantly coloured feathers, skin, antlers
etc lead to sexual dimorphism and serve to attract opposite
sex for mating.
9. Synthesis: of Vitamin D in mammals.
10. Cutaneous respiration inamphibians.
11. Parental care: brood pouches under the skin of some
fishes and amphibians protect unhatched eggs.

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Derivatives of Integument
Epidermal glands, Epidermal scales and scutes, dermal scales
and scutes, digital cornifications, horns, feathers andhairs.
A. Epidermal glands:
• Formed from Malpighian layer of epidermis often invade the
dermis.
• They may be unicellular or multicellular; tubular or alveolar
in shape and simple or compound (branched).
• Bear cuboidal or columnar secreting cells.
• 9 major types- mucous, poison, luminescent, femoral,
uropygial, sweat, sebaceous, scent and mammary glands.

13. Derivatives of Integument
i) Mucous glands: unicellular (fishes) or multicellular, secrete
mucin, forms slimy and sticky mucus when mixed in water.
Mucus keeps the skin moist, slippery and protects against
the bacteria and fungi. Abundant in fishes and amphibian
skin.
ii) Poison glands: in many fishes and amphibians, secreting
bitter and irritating secretions. Parotoid glands of toadare
aggregations of poisonglands.
Mucus gland
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14. Derivatives of Integument
iii) Luminescent glands/photophores: in deep sea luminous bony
fishes,
mucous
some multicellular glands emitting light. Superficial
cells form magnifying lens, basal part bears
luminescent cells surrounded below by reflecting pigment cells.
It serves to attract preys.
iv) Femoral glands: Only the skin glands present in some male
lizards. Present on ventral surface of thigh secreting sticky
substance that serves to hold the female during copulation.
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15. Derivatives of Integument
v) Uropygial
integumentary
glands:
glands
Only the
found in
birds, present as a prominent
swelling just above the
tail/uropygium. It is the branched
gland
for
secreting
lubricating
oily
beak,
alveolar
substance
preening feathers and attracting
opposite sex.
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16. Derivatives of Integument
vi) Sweat glands/ Sudoriferous glands: simple coiled tubular
glands on skin of mammals only. Little urea and some salts
dissolved in water are eliminated as sweat. It also helps in
thermal regulation.
• Absent in scaly and spiny anteaters and marine mammals.
• Distribution restricted in some: only on soles of feet ( cats and
mice), lips (rabbit), muzzle and between toes (Ruminants),
sides of head (bats), ears (hippopotamus).
vii) Sebaceous glands: are branched alveolar glands opening into
hair follicles of mammals. They secrete oily substance sebum
for lubrication of hair and skin.
• Ceruminous glands of external ear canals are modified
sebaceous glands secreting cerumen/ear wax.
• Meibomian glands of eyelids secreting oily substance are
modified sebaceous glands.
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17. Derivatives of Integument
viii) Scent glands: modified sweat or sebaceous glands of
mammals. They are used to repel or attract members of opposite
sex, maintain territory, signal for other members etc.
• May occur between the digits /interdigital glands (goat, rhino
etc), near eyes on head / preorbital glands (deer family), navel on
abdomen (musk deer), around anus / perianal glands (many
carnivores and rodents).
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18. Derivatives of Integument
ix) Mammary glands: are compound tubular glands that produce
milk during lactationperiod.
• In monotremes (egg laying mammals), mammary glands lack
nipples or teats and are modified sweat glands.
• In other mammals, they possess nipples and are modified
sebaceous glands.
• Distribution and number of mammary glands and nipples vary
with species (2 in many mammals to 25 in Opossum).
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19. Derivatives of Integument
B. Dermal Scales and Scutes
• Develop from dermis and hence mesodermal in origin.
• The bony dermal scales are not shed but increase in size during life.
• Present in fishes and some reptiles andmammals.
i. Dermal scales of fishes
• The overlying epidermis wears off, so dermal scales are exposed
forming exoskeleton.
• Cosmoid scales occurred in extinct lobe-finned fishes
(crossopterygii), Placoid scales in Chondrichthyes; Ganoid scales
in ganoid fishes (chondrostei and holostei); Cycloid and Ctenoid
scales in modern teleosts.
ii. Dermal scales and scutes of tetrapods: dermal scales or
osteoderms are present in some Apoda (Amphibia),
lizards, crocodiles and alligators (Reptiles);
some
armadollis and
whales (mammals).
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20. Types of Scales in fishes
Development of Dermal Scales
Labeo rohita (Rohu) 20

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Derivatives of Integument
C. Epidermal Scales and Scutes
• After evolutionary loss of dermal scales of fishes, amniotes
develop scales formed from epidermis.
• Epidermal scales appear for the first time in Reptiles.
• They are cornified derivatives of the Malpighian layer and are
generally shed and replaced.
• Reptiles have continuous outer covering of horny epidermal
scales.
• Snakes and lizards (squamatans) have thin, small and
overlapping scales which are periodically moulted.
• Crocodilians and turtles have large and thick scutes,not
overlapping but touching each other and supported by
underlying dermal bones.

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23. Derivatives of Integument
• In birds, small epidermal scales are present on the shank,foot
and base of beak. The sheath of beak is also modification of
stratum corneum.
• Some mammals like rat and beavers bear scales on tail and
foot. Scaly anteaters bear large scales which undergo ecdysis.
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24. Derivatives of Integument
D. Digital cornifications:
• Claws, nails and hoofs are
modifications of stratum
corneum at the tips of digitsand
all are made in the same plan.
i. Claws: made their appearance
first in reptiles.
• A claw bears hard, pointed
curved, horny dorsal plate
called Unguis and relatively soft
ventral plate called subunguis;
both enclosing the tip of the
digit covering the last phalanx.
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25. Derivatives of Integument
ii. Nail
• In Primates (mammals),
claws are modified into nails.
• Unguis is broad and flat,
subunguis is softer and much
reduced.
• The tip of the digit forms
highly sensitive and vascular
pad.
• Growth of the unguis takes
place from the nail root lying
below the skin in nail groove.
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26. Derivatives of Integument
iii. Hoofs
• Hoofs are modified claws and are
characteristics of ungulates.
• Unguis is U or V-shaped, thick and
curved around the end of the digit.
• Subunguis is greatly thickened
touching the ground.
• Subunguis surrounds a softer horny
substance, the cuneus.
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27. E. Horns
• Present only in hoofed mammals (even hoofed-
artiodactyla and uneven hoofed –perissodactyla).
• They are the product of stratum corneum and
present on head forming organ of offense and
defense.
i. True Horns: In Bovidae (goat, sheep, cattles), true
or hollow horns are present.
• They are unbranched, cylindrical and tapering.
• Bears hollow dermal bony core arising from
frontal bone of skull and covered by epidermal
horny hollow cap.
• Permanent structures, grow throughout the life
and are never shed.
ii. Prong horns: True horns, horny epidermal sheath
bears 1 to 3 branches (prongs) which are shed
annually.
• Present in Russian antelope (Antilocapra).
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28. Derivatives of Integument
iii. Antlers: Characteristics of Family- Cervidae
(deer family).
• Present only in male, except in reindeer and
caribou.
• They are shed annually.
• Bears solid outgrowth of dense connective
tissue with Calcium deposition connected tothe
frontal bone.
• During growth, it is covered with hairy and
vascular skin- the velvet.
• When growth is complete, the velvet wears off.
• After the breeding season, the antlers arealso
shed and new antlers develop the following
year.
• Its formation is controlled by the hormonesof
testes and anterior lobe of pituitarygland.
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29. Derivatives of Integument
iv. Giraffe horns: They are short, unbranched
and permanent antlers present in both sexes.
• Each consists of dermal core covered by
simple hairy skin or velvet which is never
shed.
v.Hair /Rhino /keratin fibre horns:
• Present on both the sexes of Rhinoceros,
perched upon roughened area of nasal bone.
• They are made of thick hairy and keratinized
epidermal fibres fused together.
• They are permanent structures, if broken
grow again.
• Asian Rhino has single horn, while African
species has two horns; one behind the other.
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30. It is in threat for its skin derivative – the horn
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31. Derivatives of Integument
F.Feathers / Plumage: Present only in birds.
• They are dry, nonliving and cornified light weight, elastic
and waterproof products of stratum corneum of epidermis.
• They show different colours due to presence of pigments of
various shades and structural arrangement.
• Development is similar to that of scales and are moulted
and replaced seasonally.
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Types of Feathers: major 3 types
iii.
i. Contour feathers:
• Quills are larger present on wings
(remiges) and tail (retrices).
• Coverts are smaller and cover the body.
ii. Down feather: very small having barbs
with barbules.
Filoplumes: delicate, hairlike feathers
with long slender stalk and terminal
barbs.

32. Derivatives of Integument
G. Hairs/ Pelage: Characteristics of
mammals.
• Cover the entire
animals), reduced
body (furred
to patches
(human) and scattered (whales).
• They are also the cornified
epidermal products of integument.
• Each hair originates from a tubular
invagination of stratum
germinativum of epidermis (hair
follicle) into dermis.
• Hair papilla contains blood vessels
and nerves, nourishes the root and
adds new cells forming the shaft.
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33. Derivatives of Integument
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•The hair shaft consists of
three layers: Cuticle made of
overlapping scales, cortex
containing pigment cells and
medulla containing air
spaces.
•The involuntary
pilli” muscle is
“Arrector
associated
with each hair follicle.
•Hairs serve for insulation
and as sensitive tactile
organs (vibrissae).

34. Integument in Vertebrates
1. Cyclostomata
• Skin consists of epidermis and dermis.
• Epidermis is multilayered and non-keratinized.
• Epidermis consists of three types of secretory cells or unicellular
glands: mucous cells secrete slime, elongated club cells are probably
neural or scab forming and granular cells are of unknownfunction.
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• Dermis consists of cutis with
white collagen fibres and yellow
elastic fibres and it also bears
melanocytes or pigment cells
which can migrate and change
the colour dark orpale.
• Scales are absent.
• A layer of subcutaneous tissue
contains blood vessels, fat and
connective tissue. V.S. of Skin of Cyclostome

35. Integument in Vertebrates (Contd.)
2. Fishes:
• Epidermis has several layers of cells; typical stratum corneum
(with keratinized cells) is absent.
• It bears unicellular goblet cells / mucus gland cells secreting
mucus.
• Mucus makes skin slimy reducing friction, protects skin from
bacterial and fungal infection and assists in control of osmosis.
• Some multicellular glands are present, mostly in Dipnoi.
• Dermis contains connective tissue, blood vessels, lymph
vessels, nerves, muscles and collagen fibres.
• Collagen fibres run parallel to the surface.
• Dermis bears dermal scales.
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36. • Elasmobranchs have placoid scales,
Chondrostei and Holostei have
ganoid scales and Teleostei have
Leptoid (cycloid and ctenoid)scales.
• Many bony fishes show brilliant
colours due to chromatophores and
iridocytes with guanin in dermis;
which causes iridescence.
• The uses of colours are :
- Cryptic for concealing
- Sematic for warning
- Epigamic or sex colour mostly
found in males, more brilliant
during breeding season.
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V.S. of Skin of Elasmobranch
V.S. of skin of Teleost

37. 3. Amphibia:
• Integument is thin and less intimately attached to underlying
muscles due to large number of subcutaneous lymph spaces.
• No exoskeleton.
• Epidermis is many layered.
• Outermost layer is Stratum corneum, protects and prevents loss
of moisture. It is constantly moulted under the control of
pituitary and thyroid glands.
•Large number of multicellular
glands are present.
•Mucus glands secrete mucus
that keeps the skin moist for
cutaneous respiration.
•Cutaneous poison glands
secrete toxic secretion thatserves
to ward off enemies.
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38. • Dermis bears two layers: outer loose
stratum spongiosum and inner
compact and dense stratum
compactum.
• Chromatophores occur in stratum
spongiosum of dermis.
• Collagen fibres run both vertically
and horizontally.
• Extinct Labyrinthodontia beared
dermal scales.
• Living Amphibians have no
exoskeleton.
• Apoda/Gymnophiona like
Ichthyophis bear dermal plates on
dermis.
V.S. of Skin of Ichthyophis
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39. 4. Reptiles:
• Integument is thick and dry with almost no skin glands toprevent
evaporation of water.
• Stratum corneum is well developed, thicker that makes skin dry.
• It is variously modified into overlapping scales, spines, scutes,
shields, plates, claws, rattles etc. formingexoskeleton.
• Exoskeleton is periodically shed – ecdysis or moulting.
•Squamatans have
overlapping epidermal
scales while Crocodolians
and Chelonians have non-
overlapping scales and
their dermis also bears
bony dermal plates called
osteoderms.
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V.S. of Skin of Lizards

40. • Reptiles have relatively few or
almost no skin glands except scent
glands for sexual attarction near
cloaca of some snakes, femoral
glands on thigh of some lizardsand
musk glands of musk turtles and
alligators.
• Dermis bears chromatophores on
upper layer by which some lizards
and snakes exhibit elaborate colour
patterns.
• Lower layer of dermis has collagen
fibres which lie at right angles.
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41. 41
5. Birds:
•Integument is thin and loosely attached to achieve
maximum freedom of movement for flight.
•It is dry and devoid of skin glands except Uropygial or
preen gland on tail which is well developed in aquatic
birds.
•Oily or waxy secretion of preen gland is used for
preening feathers and prevents beak from being
brittle.
•Epidermis is stratified and delicate except on shank
and feet.
• Stratum corneum is modified into feathers, scales,
claws, spurs and sheaths of beak.
• Claws are restricted to toes, may also occur on one or
two fingers in flightless birds.

42. • Epidermal feathers form protective body coverings. They are of
three major types: Contour, down and filoplumes.
• Dermis is thin with interlacing connective tissue fibres,
abundant muscle fibres for moving the feathers, blood vessels
and nerves.
• Dermis bears upper spongy vascular layer and lower compact
layer.
•Skin of birds has no
chromatophores.
• Melanocytes with pigment
occur only in feathers and scales.
•Body colours are mainly due to
reflection and refraction of light
from feathers.
V.S. of skin of bird 42

43. 6. Mammals:
• Mammalian skin is elastic, water proof and thickest of all vertebrates,
especially the dermis is very thick and tough.
• Epidermis and dermis have reached the highest degree of specialization
in mammals.
• Epidermis is thick and differentiated into 5 layers, from outside:
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum germinativum / Malpighi
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Section of Epidermis in mammals

44. •Modifications of stratum corneum include epidermal
scales, hairs, bristles, claws, nails, hoofs, hornsetc.
•Based on functions, 5 major types of multicellular glands
are present: sweat, sebaceous, mammary, lacrimal and
scent glands.
•Mucous glands are absent in epidermis.
•Melanocytes are the
branched stellate cells with
pigments present in
between the cells of stratum
germinativum.
•Albinism results from the
lack of pigments and
melanism results from the
presence of excess of black
pigments.
V.S. of skin of mammals
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45. • Dermis consists of connective tissue, blood vessels, nerve
fibres, sensory corpuscles, glands, fat cells and unstriated
muscles.
•Hairs are present.
•Hair shaft is projected above, hair root
is embedded in hair follicle of dermis.
•Blood vessles and nerves project into
the hair at hair papilla.
•Hair follicle is connected to the dermis
by arrector pilli muscles regulating the
movement of hairs.
• Hair colour is due to the varying
intensities of brown or black pigment
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granules between and within the hair
cells of hair cortex.
L.S. of a hair