Dermis

What is the dermis?

The inner, thicker layer of skin. It consists mainly of tough connective tissue and is attached to the epidermis by collagen fibers.

Basic anatomy of the dermis

a matrix, or sort of scaffolding, composed of connective tissues. These tissues include collagen fibres — which provide toughness — and elastin fibres, which provide elasticity. Surrounding these fibres, the matrix also includes a gel-like substance made of proteins. The tissues of the matrix give the dermis both strength and flexibility.

Eccrine Glands (Sweat)

Skin all over the body with ducts emptying through pores on the skin surface

Apocrine Glands (Sweat)

Larger then eccrine and only in the armpits and groin and empty into hair follicles and inactive until puberty and digestion causes body odor.

Function of sebaceous glands

Secrete sebum into hair follicles and waterproofs hair and skin to help them from drying out and inhibits growth of microorganisms on the skin.

Structures associated with hair follicles

Bed of capillaries, nerve endings, tiny muscle called arrector pili

How does dermis regulate body tempreture?

When the body is too cool, sweat glands stop producing sweat and blood vessels contract and hair follicles are moved (goosebumps). Sensory receptors in the dermis detect stimuli and respond.

Three tactile receptors in the dermis

Mechanoreceptor: pressure, roughness, vibration and stretching

Thermoreceptors: variations in body tempreture

Nociceptors: pain stimuli

How does the dermis excrete waste?

Through eccecrine sweat glands which contain electrolytes secreted from the skin (sodium, chloride, potassium) and waste products like urea and ammonia.

What is subcutaneous tissue?

Last layer of the skin containing blood vessels, connective tissue, axons of sensory neurons and contains the bodies fat and insulation.

Provides the cushioning for subcutaneous tissue

Reticular layer and protects underlying tissue layers from stress and strain.

Brings nutrients and removes waste from lower dermal and upper epidermal

Blood vessels

Causes hairs to move

Arrector pilli muscles

Painful stimuli in the skin

Nerve endings/Nociceptors

What is the epidermis?

Two layers of skin (dermis and epidermis) and covers the entire body surface and contains keratinocytes and melanocytes and contains no nerves, blood vessels or other structures.

Cells in the epidermis

Keratinocytes (squamous), melanocytes, immune cells, merkel cells (touch and connect nerve endings)

Layers of the epidermis (top to bottom)

stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale, basement membrane, dermis.

Three ways the epidermis protects the body

protection, water retention, vitamin d synthesis

What makes skin waterproof?

selective permeability, lipids are arranged in an organized way from the cells of the stratum corneum to protect against water loss and allowing fat soluble substances to pass through the epidermis.

Why is selective permeability both good and bad?

Good because selective permeability allows certain medications to enter the bloodstream such as scopolamine and nitroglycerin, bad because harmful substances like heavy metal led can enter the body.

How is vitamin D synthesized?

Lipid compound named 7-dehydrocholesterol (in stratum basal and stratum spinosum) charges the molecules when UV light hits them and changes them to vitamin D3.

Describe bacteria normally residing on the skin and why there are no infections

Harmless bacteria that keep the skin healthy and no infections because the normal microorganisms on the skin keep it in check however overgrowth or antibiotics may cause infection or yeast.

Why are keratinocytes on surface dead vs deep are alive?

The innermost stem cells of the epidermis continuously divide to produce more cells and these cells move up to the skin serface but once the cells are filled with keratin they die once they reach the surface and make the waterproof layer.

Which layer of the epidermis do keratinocytes begin to die?

Stratum Granulosum