Integument Ch.4

• Functions

  • regulation (internal body must be different than outside)
  • protection (& support) - scales
  • exchange of materials - like frogs - breathe through skin
  • nutrition - mammary glands
  • locomotory surface - placoid scales
  • sensory - fingers detect hearing
  • communication - fat storage
• Embryology - Mesoderm

  • mesdorm splits to form the coelom
  • Coelom - dorsally divided into nephrocoel and myocoel (Mesoderm splits)
  • Mesoderm associated with coelom is the hypomere (belly/gut) (splanknic)
  • with nephrocoel, mesomere (urinary/ reproductive tract)
  • with myocoel, epimere (not visible in adult)
• Blastula - hollow ball of cells that will become ectoderm, endoderm, and mesoderm
• Embryology - mesoderm

  
• Embryology - mesoderm

  • the mesomere gives rise to the urogenital system and the hypomere gives rise to the lining of the body cavity

  
• Embryology - mesoderm

  • the epimere is in serial clumps, somites will give rise to vertebrae, ribs, musculature, and the dermis (comes from somites) (only somites become segmented.

  
• Embryology -

  • somites lie next to notochord and under/ to the sides of the neural tube

  
• Embryology - mesoderm

  • each somite differentiates into
  • Myotome - to musculature
  • sclerotome - to bone
  • dermatome - to dermis

  
• Embryology -

  • discoidal cleavage from macrocleithral eggs can distort the embryo somehwat, though the basic pattern can be seen (flattened like a dics - no gut)
  • Bird embryos have big yolks so they distort things
  • another diagram on slide 10

  
• Embryology

  • integument has 3 origins
  • dermatome (mesoderm)
  • ectoderm
  • neural crest
• Protochordate: Amphioxus

  • Epidermis a single cell layer thick of cuboidal cells with no differentiation
  • the dermis is thin
• Vertebrates - overview

  • epidermis is more than 1 layer thick
  • has differentiated secretory cells
  • dermis is thicker and may have bone- Dermis can migrate through the body
  • dermis may have a loose fatty layer
• Vertebrates - Epidermis

  • Stratum Germinativum - adjeacemtn to basement layer, miotocally active(lowest most layer of epidermis) (next to basement layer)
  • Squamous layer - flat tile like cells (in fishes)
  • Stratum corneum - in tetrapods, keratinized thick in amniotes
• Vertebrates - Dermis

  • Stratum laxum -irregualry arranged collagen, vascularized and innervated (directly underneath the epidermis)
  • Stratum compactum - more tightly packed collagen may be arranged in piles (more at the bottom)
• Vertebrates: Chromatophores

  • various kinds, (iridophores, shiny guanine builds up)(erythrophores, red) (xanthophores, yellow) (melanophores, weird cell shapes compared to others)
  • originate from nerual crest
  • color change by distributing pigments within cells
  • melanophores mostly in dermis, produce melanosomers that are deposited into keratinocytes
• Fishes - epidermis

  • environment is not drying, so little keratinization (some exceptions)
  • abundant unicellular mucous glands (granular glands) mucous glands reduce drag, ion flow and has antibacterial properties
  • Speical glands in fish - poison, photophores
• Fishes - dermis

  • hypodermis thin and not loose
  • collagen in dermis in orderly piles that give skin flexibility in some directions but not others
• Chondrichthyes

  • placoid scales (may be homologous with teeth)
  • dentiles with ???
  • dermal pulp cavity, dentine layer
  • capped with epidermally produced enamel
• Sarcopterygii

  • cosmoid scales - flattened with bumpy top layer
  • enamel and dentine but no pulp cavity (bc flat)
  • On a layer of dermal bone (dentine and enamel grow underneath), vascular and compact
  • extant lungfish and coelacanths show reduction, lacking enamel and dentine - to make them lighter, trend in vertebraes to make lighter and faster
• Actinopterygii

  • ganoid scales primitively (smooth top layer)
  • lack dentine and often lack vascular bone
  • Note that enamel is the surface
  • interlocking/overlapping scales, very tough but not flexible
  • scales only of compact dermal bone
  • thin light and flexible
  • note that thin epidermis covers entire scale
• Actinopterygii

  • cycloid scales in most teleosts (primitive)
  • simple overlapping bony plates
  • concentric rings allow aging fish (scales are not rebuilt)
  • Ctenoid scales in advanced teleosts
  • with small cteni on exposed an of scale
  • makes skin rough texture
  • uncertain function (perhaps for breaking up water easier)
• Lissamphibia -

  • scales in caecilians - gymnophiona (not homologous w lungfish)
  • thin epidermis with weakly keratinized stratum corneum
  • many multicellular glands sunk into epidermis - mucous, granular
  • ample blood supply - cutaneous respiration
• Amniotes

  • lots of keratinized epidermal derivatives common
  • horns, claws, hooves, nails, feathers, hair
  • scutes (very big scales) often made of keratin
  • dermal scales are rare (osteoderms in some)
• Sauropsida

  • epidermis is thick and with multiple layers, scales are thickenings, beta keratin hinges thinner, alpha keratin, few glands, multicellular and specialized when present (synapomorphy beta keratin)
• Sauropsida - Lepidosauria (lepi = scale) (sauria = lizard)

  • scales strongly evident
  • reduplication of the epidermis
  • new epidermis grows under old
  • old epidermis is periodically shed
• Birds

  • thin epidermis, except on legs
  • body scales modified into feathers
  • few sepcalized glands (uropygial and salt gland)
  • can have scales on legs (rat/beaver tails)
• Mammals

  • epidermis thick
  • alpha keratin only
  • scales occasional
  • variety of epidermal glands sunk into dermis (lots of galnds)
  • dermis with papillary layer and reticular layer
• Mammals

  • hair of uncertain origin - not homologous with scales
  • mostly epidermal, through dermal root papilla needed to induce hair growth
  • inner medulla dead cells and outer cortex of keratin
  • under fur (insulative), guard hairs, vibrissae (whiskers, adaption to low light)(homeothermy)
• Mammals

  • true horn with bony core and keratin sheath, neither shed, unbranched, permanent
  • Bovidae - things w horns
  • other horns like giraffes / rinos
  • True antlers in cervidae only
  • branched and shed annually (think deer/moose)
  • made of dermal bone, though covered with epidermis (velvet) (provides blood supply) when growing
• Mammals

  • glands common and widespread
  • eccrine excrete by vacuoles fusing with cell membrane (sweat glands, dog nose)
  • apocrine excrete by cells budding - heavy secretion (pheromones)
  • sebaceous excrepete by rupturing the cell membrane - musk/ skunk (heaviest oils, hair follicles)
• Scale overview