ZOO 2090 Lecture Notes - Lecture 6: Stratum Corneum, Mucous Gland, Neural Crest
1 May 2018
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ZOO2090 – The Integument of “Fishes”
Integument (or skin) is a composite organ at the interface between the organism and its
environment. It varies greatly depending on habitat of the organisms.
Basic Structure:
• From outside inside
o Epidermis
▪ May be one or multiple layers
• If multiple, the most inside layer=stratum germinativum (generated
new cells and pushes outward)
• Most outside layer = stratum corneum (keratinized and water
proof)
• When cells move from germinativum to the outer layer, the cells
generally keratinize and die
▪ May contain glands including:
• Unicellular mucous gland
• Multicellular gland (tubular and alveolar glands; often located in
dermis but originate from epidermis)
o Dermis
▪ Two layers:
• Vascular stratum spongiosum (top)
• Thicker stratum compactum (bottom)
▪ Basic components:
• Network of fibres (collagenous and elastic)
• Small nerves
• Blood vessels
• Pigment cells (chromatophores)
• Connective tissue (holds everything together)
▪ Has potential to form bone
▪ *see skin section of an amphibian
o Hypodermis (may not be present in all vertebrates)
▪ Beneath the dermis
▪ Often contains fat cells for insulation (important in polar bears)
• Development
o Epidermis forms from ectoderm
o Dermis is developed from mesoderm (dermatome)
o Pigment cells (chromatophores) migrate from the neural crest
o *many cells migrate during developmental process
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