We already know what organs are in the integumentary system. Now let us concentrate on the structure and function of each organ individually.
Skin: The skin is the main organ of the integumentary system. It is made of two dermal layers. They are:
Epidermis: It is the outermost layer of the skin. It forms the waterproof barrier over the body.
Dermis: It lies below the epidermis. It contains blood vessels, hair follicles and various glands.
Although studied along with the different layers of the skin, hypodermis is actually not a part of the largest organ of the body. In fact it is a subcutaneous layer (layer that lies below the skin) that attaches the skin with the underlying tissues. 50% of the hypodermis is fat which provides padding and insulation for the body. The glands present in the skin are the sweat glands and the sebaceous glands. The sweat glands release sweat which is the primary way of cooling the body. The sebaceous glands on the other hand release sebum - an oily substance that lubricates the skin and the hair.
Hair: One of the defining characters of all mammals, hair is formed from the hair follicles that are found all over the skin. Hair is mainly keratin. Each hair strand can be divided into three layers that lie one inside the other. The innermost layer is the medulla which is made up of loose cells and air spaces. Outside this is second layer - the cortex which is made of densely packed keratin. The outermost layer is the cuticle which is made up of cells overlapping like scales. Hair traps air around the body that acts like an insulating layer. Hair lining the nasal chambers and those that appear in the form of eyelashes, keep out dust particles. The hair present in non human mammals is termed as fur.
Nails: Like the skin, nail is also made up of keratin. In fact nails are a hard layer of keratinized cells and they develop from the epidermis. These structures that are present on the end of fingers provide protection to the tips of toes and fingers.
Scales: Scales are rigid plate-like structures that cover the body of fish, reptiles and arthropods. These grow from the skin of an animal and their function is to provide protection to the inner tissues of the body.
Feathers: Of all the system structures, feathers are the most complex in terms of structure. These are typically present in birds. Although apparently they aid birds in flight, feathers also provide insulation, water proofing and camouflage.
The skin, which is the main organ, along with its extensions the hair, nail, scales, and feathers protect the inner tissues of the body. They also ensure that the internal environment is not affected due to changes in the conditions in the environment outside. Hence the integumentary system organs play an important role in the proper functioning of all other systems of the body.