8 - integument

7/27/2019 8 - Integument

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Lecture 8 TheIntegumentKK or H&G Chapter 6 + KK p. 501

snapping turtle


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The Integument is:

Morphologically Compound

Epidermis

Dermis

Embryologically Compound

Ectoderm

Mesoderm (dermatome,

mesenchyme)

plus minor contributions from

neural crests cells

KK. 6.1, H&G 6.1


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Functions of the Integument

Protection Water balance

Reserve food storage

Heat regulation

Sensory Excretion

Secretion

Respiration

Locomotion Communication

Reproduction

mandrill


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Generalized Vertebrate Integument

KK 6.2, H&G 6.1

The epidermis produces mucus in fishes and keratin in tetrapods.

Glands are also from the epidermis, although they may penetrate into

the dermis. Melanophores are brown/black pigment cells in the

epidermis containing melanin.


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Generalized Vertebrate Integument

The Dermis may contain blood vessels, nerve endings, fat bodies,collagen and elastic fibres, chromatophores, and bone.

Chromatophores are more diverse in pigmentation than

melanophores, often can change quickly, and are typically found

in ectotherms.

KK 6.2, H&G 6.1


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Bony Armour of Ostracoderms

KK 6.8, H&G 6.4

The armour of ancient fishes was enamel covering dentin, covering

bone. Enamel is composed of the mineral apatite. Dentin is also mostly

apatite, but is infused with protein (collagen) fibres.


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Scales of Modern Fishes

Scales of modern fishes arethought to be derived from

ostracoderm armour (cosmoid

scales). In Osteicthyes with

bony (ganoid) scales, e.g., gar,

bowfin, the dentin layer is

missing. In teleosts, both the

enamel and dentin are missing,

and only bone with no apatite

and lots of collagen remains.

In shark scales (dermaldenticles or placoid scales) all

three layers remain.


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Elasmoid scale from a

mature Atlantic Salmon.

Fisheries biologists can use

such scales to determine the

fish

s age, when it went tosea, and how many times it

has returned to spawn.


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Amphibian Integument

KK 6.12, H&G 6.7

Amphibian integument is like that of

fish, but poison glands are commonand there are no scales. Many

poisonous forms are brightly

coloured with chromatophores.


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Reptile Integument

Snake Skin

KK6.12, H&G 6.8

There are no mucous glands inamniotes, although scent glands may

be present.

Scales are epidermal, not dermal, and

are keratin rather than bone. They are

not homologous with fish scales

Larger scales on the ventral surface of

snakes or over dermal bones in turtles

and crocodiles, are called scutes.

Dermal bones under scutes are called

osteoderms.


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Bird Integument

Aves have a thinly keratinized skin,otherwise generally similar that of

reptiles. They have reptile-like

keratin scales on their legs, and

feathers are thought to be derived

from keratin scales. They also haveclaws and friction pads on their feet.

Avian innovations: in addition to

feathers of various kinds, they have

a keratin beak and a uropygial glandunder the tail for grooming the

feathers.

KK 6.15, H&G 6.10, 6.11


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Despite that feathers seemto come from deep in the

integument, they are

actually produced from

the epidermis like all

keratin structures. The

epidermis penetrates thefeather follicle and covers

the dermal papilla around

which a new feather

develops.

KK 6.16, H&G 6.12


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Epidermal Glands- sebacious glands

- sweat glands

- mammary glands

- scent glands

Mammalian

Integument

KK 6.20, H&G 6.13

Hair is also made

of keratin, but is

not considered to

be homologous toreptilian scales.


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Mammary GlandsKK 6.22, H&G 6.14

Mammary glands arise from

ectoderm that descends along

2 folds ormilk lines in the

embryo.

Monotreme


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pangolin

Keratin structures in mammals

hair, including sensory bristles

scales (e.g. pangolin, armadillo)

unguis (claws, nails, hooves)

true horns (e.g. cow, antelope)

rhinocerus horn baleen (baleen whales)

quills (porcupine, hedgehog, echidna)

echidna


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keratin horns bony imposters


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Teeth

Teeth are also structures of theintegument. They have

fundamentally the same structure

as the armour of ancient fishes

and placoid scales of sharks.

Teeth arise at the interface

between the epidermis and the

dermis.

The epidermis produces the

enamel from above, and the

dermis produces the dentin from

below.

KK 6.32 Continuous formation of

shark teeth.


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Mammalian

Tooth

Development

Mammalian teeth also begin as

a fold in the margin of the jaw,

even though they are anchoredin bone rather than integument.

Special cells of the epidermis

(ameloblasts) produce enamel,

while odonoblasts from the

dermis secrete dentine. Again,the tooth grows between

epidermis and dermis. Neural

crest contributes as well.

KK 13.8, H&G 7.2

8 - integument

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