Integumentary System Protection & support Sensory Respiratory (amphibians) Thermoregulation – Dissipate heat (blood vessels, sweat) – Conserve heat (blood vessels, hair, feathers)

Locomotion Water balance Protective coloring, behavior Vitamin D synthesis

Epidermis Ectodermal derivative nonvascular

Epidermis Stratum germinativum – Deeper layer – Mitosis

Epidermis Superficial layer – Mucus cells (amphibians, fish) – Proteinaceous cells/granular glands Slime, poisons, enamels, photophores, pheromones Keratin (cornified, horny, stratum corneum) – Tetrapod feature

Epidermis Glands are epidermal in origin

Dermis Dermatome (mesoderm) in origin Lateral/ventral mesoderm Neural crest cells for pigment

Dermis Collagen for strength Mucopolysaccharides Elastic fibers Smooth muscle Blood and lymph vessels Follicles and bases of gland

Dermis Dermis has ancient potential in forming bone as in this ostracoderm!

Hard or Mineralized Tissues Enamel Dentin Bone – Lamellar = Compact – Spongy

Hard tissues Bone is very primitive dating back to the ostracoderms

Dermis Chromatophores – Dermal in origin – From neural crest cells – Homeotherms have melanophores & pigment is INJECTED into epidermis – Poikilotherms – the pigment stays in the dermis

Dermis - Chromatophores Iridophores – silvery & iridescent Xanthophores – yellow Erythrophores - red

Fish Skin - Epidermis Cyclostomes – thin with unicellular mucus glands Jawed fish – unicellular mucus glands, no keratin!, photophores in some

Fish Dermis Cyclostomes – no scales Ostracoderms & Placoderms – Armor shields

Ostracoderm Armor Lamellar bone Spongy bone Dentin(e) Enamel

Armor Shield Denticle – Elevations capped with enamel Protection Mineral reservoir

Fish Dermis Cosmoid scales Modified dentin layer called Cosmine Extinct sarcopterygians

Fish Dermis Ganoid scales Modified thick enamel layer called ganoine Found in gars

Ganoid scale

Fish Dermis Placoid scales Chondrichthyes Denticle points reduce friction Ancestor to teeth

Placoid Scales Dentin Pulp Pulp cavity Epidermis

Fish Dermis Modern scales Acellular Thin lamellar bone only Teleosts and modern sarcopterygians Annual rings allows aging of fish

Cycloid & Ctenoid Scales

Cycloid scale

Ctenoid scale

Key Points Give two major characteristics of fish skin.

Amphibians No scales Multicellular glands (mucus) Stratum corneum – keratin – tetrapod feature

Amphibian Epidermis Thin Stratum corneum with keratin Mucus and granular glands

IntegumentIntegument DermisDermis EpidermisEpidermis Mucus gland Poison gland

Amphibian Dermis Firmly attached May have chromatophores (Caecilians may have bony dermal scales)

Key Points Give 2 major characteristics of amphibian skin

Reptile Skin THICK stratum corneum Epidermal scales in all Horny (keratinized)surface structures Very few glands, dry skin Some have bony dermal scales or plates

ScalesScales EpidermisEpidermis DermisDermis ScaleScale CornifiedlayerCornifiedlayer ChromatophoresChromatophores

Reptile epidermis Stratum corneum with keratin Scales Scutes No mucus glands Some have granular/scent glands, but rare

ScalesScales EpidermisEpidermis DermisDermis ScaleScale CornifiedlayerCornifiedlayer ChromatophoresChromatophores

Reptile Dermis Thin Osteoderms e.g. crocodile Turtle shell – Carapace – Plastron Gastralia – Abdominal “ribs” but dermal scale splints in abdomen of crocodiles

Key Points Give 2 major characteristics of reptile skin

Bird Skin

Thin skin, only thick at foot and beak Loose skin FEATHERS Evolution of feathers

Bird Epidermis Thin Horny scales at face, legs, feet Beak Uropygial glands at rump, esp. in aquatic birds

Bird Epiderms - Feathers Contour feathers

Feathers

Shaft – Calamus = Quill – Rachis – vane-bearing part Vane – Barb – Barbule – Hooklet

FeathersFeathers ShaftShaft QuillQuill VaneVane

Feather structure ShaftShaft BarbBarb HookletsHooklets BarbuleBarbule

Bird feathers Preening Rehooks hooklets

Bird feathers Down Feathers MAY be ancestral feather Short calamus No hooklets insulation

Feathers Contour feathers Down feathers Filoplumes Bristles

Bird feathers Feather follicle – ectoderm, but activated by vascular mesoderm Molt is shedding old and growing new feathers

Bird Dermis Thin Arrector pullorum muscle Some males have a spur of dermal bone near feet

Mammal Skin

Mammal skin Hair Glands – a variety Highly keratinized stratified cornified epidermis Thick dermis

Mammal Epidermis Stratum germinativum for mitosis Stratum granulosum (one or more layers) Stratum corneum

Stratum corneum derivatives Horny scales as in beaver tail Claws, hooves, nails, armadillo shell

Stratum corneum derivatives - horns True horns Dermal bony core Horny cover Not shed Ruminants (antelope, cattle)

Stratum corneum derivatives - horns Hair horns Rhinoceros

Stratum corneum derivatives - horns Antlers & giraffe horns Bone Velvet Antlers (deer, elk, moose) shed but not giraffe horns

Mammal Epidermis Glands Sweat Sebaceous Scent Mammary

IntegumentIntegument Eccrine sweat gland gland SweatporeSweatpore SebaceousglandSebaceousgland ErectormuscleErectormuscle FollicleFollicle Apocrine sweat gland gland

Mammal Epidermis Hairs Origin Shaft – Cortex with cuticle – Medulla

Mammal Epidermis - hair Root of hair – Follicle undergoes mitosis – Bulb is widened area in dermis providing nourishment for growing hair Arrector pili muscle

Types of hairs Guard hairs

Types of hair Underfur

Types of hair Vibrissae

Types of hair Quills

Mammal Dermis Very thick Follicles Arrectors CT Blood vessels Gland bases Nerve endings

Key Points Give one major characteristic of bird skin Give one major characteristic of mammal skin

Epidermal or Dermal? Sweat gland Hair Fish scale Reptile scale Oil gland