1. The Integumentary System Skin Jasmine Gallup, Tony Li, Michael Ivanov, Ben Jones

2. The Basics Dermis- Innermost layer, contains blood vessels, nerves, sweat glands, hair follicles, and smooth muscles Epidermis- Outermost layer, rapid cell division leads to a tough waterproof outer layer which is constantly replaced, contains melenin* * a pigment that protects the body from UV radiation Functions- 1. Is a protective covering for the body and a sensory organ 2. Regulates body temperature 3. Produces vitamin D 4. Protects the body from UV radiation

3. Many amphibians must keep their skin moist at all times because it is their primary respiratory organ. The skin is membranous and oxygen can be absorbed directly into the bloodstream. Mucous glands in the skin help keep amphibians’ skin moist. Amphibians’ skin is very thin and permeable Amphibia

4. Agnatha, Chondrichthyes, and Osteichthyes Placoid cells, or denticles are tooth-like scales that cover sharks, rays, and skates. These develop from the dermal layer of the skin Many extinct agnatha (jawless fish) had scales similar to that of sharks, but nowadays the only covering is skin

5. Aves Birds have a very different type of skin system than mammals, mainly because they have feathers. Feathers aid birds in flight, waterproofing, and warmth. They also provide coloration for communication. The different types of feathers all grow from the epidermis layer of skin. Specifically from regions of skin known as pterylae. These feathers are made of a protein called Beta-keratin. Plumage- the arrangement and appearance of feathers on the body Sebaceous glands- the glands that secrete feathers on the skin of birds Reptiles have thick and protective skin Their scales are made of keratin, like that of birds Both birds and reptiles have few specified glands. The ones they do have usually secrete pheromones. In birds there is a gland that secretes an oil which helps with preening. Reptilia

6. Mammalia Mammals skin is the most complex system Underneath the layer of skin we have a layer of insulation (fat) that conserves heat. This layer is called the hypodermis. Besides that, as we already know, there are two other layers the epidermis and dermis. This skin system is complex simply because of the many specialized glands that mammals posses. Other animals do not posses these glands. Mammals also have hair, a defining characteristic of this Phylum