.Found below the epidermis, but above the subcontinous layer

.composed of strong connective tissue(collagen and elastic fibers)

. cells found here are predominantly fibroblasts, with some macrophages, and a few adipocytes

.Contains Blood vessels,nerves, glands, and hair follicles

.Can be divided into a superficial papillary region and a deeper reticular region.

.Largest organ

-Functions of skin-

Protect 

Temp regulation 

Sense organ 

  Synthesis of vitamin D precursor 

Epidermis

-stratum basale  (takes on role of mitosis)

Dermis

hypodermis

.Makes up 90% of epethelial cells in epedermis

.Produce the protein Keratine

.Produce lamellar granules(produce a water repellent)

.Make up 8% of epithelial cells in epidermis

.develop from ectoderm of developing embryo

.produce the pigment melanin(yellow-red or brown-black pigment that contributes to the skin color and absorbs damaging ultraviolet light

.long slender projections attach to keratinocytes, where the shot in melanin, which in return helps shield the keratinocytes from UV rays

.arise from red bone marrow and migrate to epidermis.

.participate in immune response against microbes

.easily damaged by (UV)

.Detect fine touch

.Least numerous of cells in epidermis

.located in deepest layer of epidermis

.come in contact with merkel disks where they both contribute to detecting fine touch sensation

-Consist of- 

.sebacious glans(oil Glands)

.sudoriferous glands(sweat glands)

-eccrine Sweat Gland(open onto skin surface by the axillary and inguinal areas )

-apocrine sweat gland(open into hair follicle.secretion is odorless, but when it comes into contact with bacteria that metabolizes it, the secretion gives off a bad odor.)

.No blood vessels in epidermis

.Papillary layer of blood vessels

    -used for temp regulation

     dilation – incr blood flow and heat loss

      constriction- decr blood flow and heat retention

Precursor is cholesterol in cell membranes

Sunlight on skin causes cholesterol to be converted to intermediate

Liver and Kidney  synthesize the final product – cholecalciferol (calcitriol)

Calcitriol regulates the level of calcium and

phosphate in blood and bones, and at the same time absorb calcium from food in intestinal tract.

Hair

Nails

Sense organs in skin

• Touch

       fine touch receptors– near surface

       pressure receptors- deep

• temperature receptors

• pain receptors      

• Subcutaneous layer

• Contains adipose tissue