MIXED CONTENT REVIEW

THE CARDIOVASCULAR SYSTEM

WHAT IS YOUR LEARNING STYLE?

WHAT IS AN ELECTROSCOPE?

VOCABULARY PART 3

CENTRIOLES AND CENTROSOMES

THE DERMIS OF THE SKIN

The dermis is the layer of the skin beneath the epidermis. It  makes up about 90% of the skin's thickness. It has:

• Blood vessels
• Hair follicles - This is the tube that surrounds the hair and nourishes it.
• Lymphatic vessels - These drain the lymph in the skin. The lymph contains cells that fight infections. 
• Sebaceous glands - These glands produce sebum. This is the oily substance that lubricates the skin and keeps it waterproof. It keeps the skin smooth and supple. It also helps to fight off bacteria and fungal infections.
• Sweat glands - Produce sweat. There are two types: Apocrine and Eccrine sweat glands. Apocrine sweat glands are found in the armpit and pubic areas. They produce milky sweat that can encourage bacteria growth. Eccrine sweat glands are found in the other parts of the body. 
• Nerve endings - These include touch, pain, pressurs and temperature sensors.
• Collagen and Elastic fibers - These are connective tissues that help to keep the skin tough and elastic.

The dermis consist of two layers. The upper layer is called the papillary dermis and the lower one is called reticular dermis. The papillary layer is thinner than the reticular layer. The papillary layer contains a lot of blood vessels that help to nourish the epidermis and to regulate the body's temperature. The reticular layer has collagen fibers arranged parallel to the skin to help in stretching and maintenance of the strength of the skin. It supports the hair follicles, sweat and sebaceous glands.