Part 2 Appendages of the skin
These are found over the entire body. There are approximately 3 million per person
In the diagram above, note that the gland in a simple coiled tubular arrangement with the duct going through the epidermis.
Note how the duct opens into the hair duct in contrast to the sweat glands. They also have a simple coiled tubular arrangement.
If the sebaceous glands become blocked by accumulated sebum and white head (zit) appears. As this material dries it becomes a blackhead. Acne is an inflammation of the sebaceous gland.
Hair is distributed over the entire body except the soles, palms, lips and portion of the gentitalia. In the human, it serves to protect the head against trauma and heat loss.
Hair consists largely of dead keratinized cells that are tougher than those found on the skin. Hair consists of several regions:
a) Shaft – a region where keratinization is complete.
b) Root- a region where keratinization is on going.
a) Medulla- central core and is filled with large cells and air spaces
b) Cortex- surrounds the medulla and is made of flatten cells
c) Cuticle- outermost layer, one cell layer thick and helps keep hair from matting as it wears out it forms the so called split ends