Here are some basic facts about skin, hair and teeth.
Skin
Skin is made up of two main layers the epidermis, the outermost layer, and the dermis, the inner layer. As the largest organ of the integumentary system, skin plays a key role in protecting the body against pathogens and excessive water loss.
The epidermis, "epi" coming from the Greek meaning "over" or "upon", provides waterproofing and serves as a barrier to infection. It is actually made up of 5 sublayers. New skin cells are constantly being made in the innermost layers of skin. These skin cells evolve, become filled with keratin, and move towards to the top layer. They eventually reach the top layer, called the stratum corneum, consisting of approximately 15-350 layers of dead cells strengthened and made water-resistant by the keratin.
The dermis, which serves as a location for the appendages of skin, consists of connective tissue and cushions the body from stress and strain. It is tightly connected to the epidermis by a basement membrane. It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels, blood vessels and many nerve endings.
Hair
There are two main parts of a strand of hair: the follicle and the shaft. The part below the skin is called the hair follicle, or when pulled from the skin it's called the bulb. Hair grows from follicles which are found in the dermis layer of skin. The shaft is what extends past the skin; it's hard and filamentous.
A cross section of the hair shaft can be divided into three zones: the cuticle, the cortex, and the medulla. The cuticle, the outermost zone, is made up of layers of flat thin cells that overlap one another like roof shingles. The cortex, the next zone, contains keratin bundles that are in rod-like cell structures. The medulla is a disorganized and open area at the shaft's core.
Teeth
Teeth are calcified structures that are largely made of tooth enamel, dentin, cementum, and dental pulp. Surprisingly teeth are not made of bone, but rather of these multiple tissues of varying density and hardness. Tooth enamel is the hardest and most highly mineralized substance in the human body. In fact, ninety-six percent of enamel is mineral. Enamel is the typically visible dental tissue of a tooth which covers the anatomical crown. The crown is mostly made of dentin with a pulp center, and is above the cementoenamel junction (CEJ). Below the CEJ is the anatomic root which is covered with cementum. The roots of teeth are embedded in the Maxillary bone and are covered by gums.
Skin
Skin is made up of two main layers the epidermis, the outermost layer, and the dermis, the inner layer. As the largest organ of the integumentary system, skin plays a key role in protecting the body against pathogens and excessive water loss.
The epidermis, "epi" coming from the Greek meaning "over" or "upon", provides waterproofing and serves as a barrier to infection. It is actually made up of 5 sublayers. New skin cells are constantly being made in the innermost layers of skin. These skin cells evolve, become filled with keratin, and move towards to the top layer. They eventually reach the top layer, called the stratum corneum, consisting of approximately 15-350 layers of dead cells strengthened and made water-resistant by the keratin.
The dermis, which serves as a location for the appendages of skin, consists of connective tissue and cushions the body from stress and strain. It is tightly connected to the epidermis by a basement membrane. It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels, blood vessels and many nerve endings.
Hair
There are two main parts of a strand of hair: the follicle and the shaft. The part below the skin is called the hair follicle, or when pulled from the skin it's called the bulb. Hair grows from follicles which are found in the dermis layer of skin. The shaft is what extends past the skin; it's hard and filamentous.
A cross section of the hair shaft can be divided into three zones: the cuticle, the cortex, and the medulla. The cuticle, the outermost zone, is made up of layers of flat thin cells that overlap one another like roof shingles. The cortex, the next zone, contains keratin bundles that are in rod-like cell structures. The medulla is a disorganized and open area at the shaft's core.
Teeth
Teeth are calcified structures that are largely made of tooth enamel, dentin, cementum, and dental pulp. Surprisingly teeth are not made of bone, but rather of these multiple tissues of varying density and hardness. Tooth enamel is the hardest and most highly mineralized substance in the human body. In fact, ninety-six percent of enamel is mineral. Enamel is the typically visible dental tissue of a tooth which covers the anatomical crown. The crown is mostly made of dentin with a pulp center, and is above the cementoenamel junction (CEJ). Below the CEJ is the anatomic root which is covered with cementum. The roots of teeth are embedded in the Maxillary bone and are covered by gums.