Table 1.

Selective functions of the integument

Protection from the environment

Mechanical, keep the form and internal organs in position and away from damage

Chemical, internal homeostasis in water and land (barrier)

Physical: UV (melanocyte on human)

Keep moist (amphibian) and oily (sebaceous gland)

To be worn off

To heal and regenerate (cytokines)

Defense

Exoskeleton (arthropod)

Armor (turtle, armadillo)

Spiny appendages (porcupine quills)

Inflammatory response (prostaglandin, etc.)

Immune function, with memory of previous stimuli

Weapons

Sting cell of hydra and jelly fish

Claws

Poisonous glands

Communication with outside organisms

Display of messages (pigment pattern, painted skin of human)

To mark territory

Pheromones for sexual attraction

For pack behavior coordination

To scare enemies away

To mimic

Communication with inside organs

Sense the environment (human skin, mouse vibrissa)

Tactile or thermo senses go in through nerves

Endocrine-like function through secretion (neuro-endocrines, endorphin, growth factors, etc.)

Respiration

Insects

Some frogs

Chemical reaction

Vitamin D

Locomotion

Swim (tentacles of hydra, jelly fish and octopus; tube feet of sea cucumber)

Crawl (belly scale of snake)

Glide (skin flap of Pterosaur, bat)

Fly (feathers)

Thermoregulation

Hairs (mammals)

Sweat gland

Dermal blood vessels

Feathers (feathered dinosaurs, birds)

Progeny bearing

Skin flap in toads and abdominal pouch in kangaroos

Mammary glands in mammals