skin epidermis and dermis. epidermis the epidermis is the outer layer of our skin it is made of...

Skin

Epidermis and Dermis

Epidermis• The epidermis is the outer layer of

our skin

• It is made of several layers:1. Stratum corneum2. Stratum lucidum3. Stratum granulosum4. Stratum germinativum

Stratum corneum• The stratum corneum is the layer we

touch and care for; it is only dead cells

• This layer contains NO blood vessels (i.e. nutrients can’t be brought to the epidermis)

• When the cells die, they undergo a chemical process that changes them from soft, easily damaged cells into ones that are harder and tougher.

• Keratin is a protein that helps harden these cells and makes them waterproof, thereby helping to prevent water loss by the body

• Although dead, these cells can pass on sensations such as pressure to the nerve endings in the layers below the epidermis

Stratum Germinativum

• The stratum germinativum (jer-min-a-tiv-um) is the bottom layer of cells in the epidermis, which is made up of cells which divide to produce new cells (cell division)

• As new cells are produced, they push older cells above them toward the surface of the skin.

• The outer layer is constantly shedding dead cells

• The SG layer of the epidermis produces the pigment melanin which gives skin color, and allows the skin to tan

• Melanin production is stimulated by exposure to ultraviolet light; doses of sunlight cause the skin to tan

• Prolonged exposure to the sun may destroy several layers of epidermal cells and cause sunburn/blisters

• Freckles are caused by uneven distribution of melanin (small irregular patches)

Dermis• Underneath the epidermis

• Contains living tissues which are specialized to monitor the changes that occur in the environment immediately around the body

• Contain collagen fibres: limits how much the skin can be stretched

• Contains elastic fibres: pulls the skin back after stretching

• Contains blood vessels: for regulating body temperature in response to impulses from special heat/cold receptors

– There are also touch, pressure, and pain receptors; found within different levels of the dermis

• Contains many dermal papillae: blood in these dome-shaped structures nourish the germinative layer above

Between the Dermis and Epidermis

• Where the epidermis and the dermis meet, there is a wavelike layer formed of many tiny cones and ridges

• These patterns show through the surface of the skin on the hands and feet, some of them becoming fingerprints

• The patterns emerge while the baby is developing in the uterus and never change, except with respect to size

• Patterns on the skin of fingers can be classified into 10 basic arrangements of loops and whorls

• Even identical twins will have some differences (even if they are not obvious from facial feature, body size etc)