Integument in Different Classes of Vertebrates

Integument in Different Classes of Vertebrates

Integument in Different Classes of Vertebrates

We will discuss and compare the integument in different classes of vertebrates under two headings : Epidermis and Dermis .


Integument in Pisces / Fishes

  1. Epidermis
    • Epidermis is thin, simple and multi layered.
    • The stratum germinativum(inner most layer) consists of actively dividing cells and it forms the cells present at the upper layer.
    • Fishes lack stratum corneum instead they have a layer of cuticle at the outermost part of skin.
    • Their epidermis also consists of unicellular mucus gland. In some fishes , poision glands and light emitting gland are also found.
  2. Dermis
    • Dermis is comparatively more thick and is basically made up of fibrous connective tissue.
    • Fibers (collagen fibers) usually run transversely and parallel with one another.
    • Scales in fishes are present in the dermis which extends beyond the epidermis .
    • Cartilaginous fish ( chondrichthyes ) usually have placoid scales while bony fish (osteichthyes) usually have cycloid or ctenoid scales.
    • Many color imparting (giving) cells called chromatophores are also present in dermis of skin just below epidermis.


Integument in Amphibia

  1. Epidermis
    • In case of amphibians , they are comparatively thick than that of fishes.
    • It consist of outer stratum corneum and stratum germinativum.
    • Stratum corneum is made up of flat, dead and keratinized cells while stratum germinativum is usually made up of actively dividing columnar cells.
    • Epidermis of amphibians lack hard structures like claws, horns, spines etc.
  2. Dermis
    • It is also comparatively thick than that of fishes.
    • It is mainly made up of fibrous connective tissue containing a large number of blood vessels.
    • Presense of multicellular mucus and poison glands, derived from stratum germinativum of epidermis.
    • Mucus glands are best developed in those amphibians which spend  most of their time in water while poison glands are best developed in those amphibians which spend most of their time in land.
    • In many amphibians, coloured giving cells called chromatophores are also present in the dermis of skin just below epidermis.


Integument in Reptiles

  1. Epidermis
    • Epidermis is the most thicker than that of fish and amphibians.
    • Stratum corneum in them is also very much thick preventing the loss of body’s moisture.
    • Their epidermis is virtually without any glands and this also prevent the loss of body’s moisture.
    • Their epidermis consist of different derivatives like haard epidermal scales, claws, spines etc.
  2. Dermis
    • Dermis of reptiles is relatively thin that of amphibians.
    • The upper layer of dermis consist of areolar connective tissue while the lower layer consist of fibrous connective tissue.
    • In many snakes and lizards , chromatophores are also present in dermis of skin just below epidermis.


Integument in Birds/Aves

  1. Epidermis
    • In birds is comparatively thin that of reptiles but it is thick than that of fish and amphibians.
    • The innermost layer of epidermis is stratum germinativum which consist of actively dividing cells and it forms the cells of upper layer( stratum corneum).
    • Stratum corneum is made up of flat dead cells and it forms derivatives like feathers, scales, claws etc.
    • Feather are lost and replaced periodically.
    • Scales in birds are limited only to the lower part of their legs and feet.
    • The skin of birds is virtually without any glands except for preen glands (uropygial glands) present dorsally at the base of tail feather.
  2. Dermis
    • In birds ,it is also thin compared to that of reptiles.
    • It is made up of areolar connective tissue containing blood vessels, nerve fibres, muscle fibres, fat cells etc.
    • Dermis of birds lack chromatophores.


Integument in Mammalia

  1. Epidermis
    • In mammals it is thickest among all the vertebrates.
    • In the thick part of the body , epidermis may consist of five different layers which are :-.
      • Stratum corneum ; it is the outermost layer and made up of flat , dead and keratinized cells.
      • Stratum lucidium ; it is present just below stratum corneum and consists of cells   having protein called eledin .
      • Stratum granulosum ; it is present below stratum lucidium and consist of cells having granules called keratohyaline.
      • Stratum spinosum; it is present below stratum grannulosm and it consist of defensive (protective ) cells called Langerhans cells.
      • Stratum germinativum; it is inner most layer and consist of actively dividing columnar cells.
  2. Dermis
    • In mammals, dermis is also the thickest among all the vertebrates.
    • The upper part of dermis is made up of areolar connective tissue while the lower part consist of adipose tissue.
    • Different types of nerve fibres ,muscle fibres ,blood vessels etc. also found in the dermis .
    • Dermis also consist of different glands like sweat glands,sebaceous glands, mammary glands,lacrimal glands(tear) derived from epidermis.
    • Epidermal derivatives like hair is also present in the dermis.

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