Vitiligo

 Vitiligo Individuals with vitiligo experience depigmentation that results in lighter colored patches of skin. The condition is especially noticeable on darker skin. (credit: (a) Klaus D. Peter (b) Owl Bridge Media / Wikimedia.)

melanin

 Albinism is a genetic disorder that affects (completely or partially) the coloring of skin, hair, and eyes. The defect is primarily due to the inability of melanocytes to produce melanin. 

Individuals with albinism tend to appear white or very pale due to the lack of melanin in their skin and hair. Recall that melanin helps protect the skin from the harmful effects of UV radiation. Individuals with albinism tend to need more protection from UV radiation, as they are more prone to sunburns and skin cancer. They also tend to be more sensitive to light and have vision problems due to the lack of pigmentation on the retinal wall. Treatment of this disorder usually involves addressing the symptoms, such as limiting UV light exposure to the skin and eyes. In vitiligo, the melanocytes in certain areas lose their ability to produce melanin, possibly due to an autoimmune reaction. This leads to a loss of color in patches (Figure 5.10). Neither albinism nor vitiligo directly affects the lifespan of an individual

fat deposit

 Where the fat is deposited and accumulates within the hypodermis depends on hormones (testosterone, estrogen, insulin, glucagon, leptin, and others), as well as genetic factors.

Cells of the Epidermis

 Figure 5.6 Cells of the Epidermis The cells in the different layers of the epidermis originate from basal cells located in the stratum basale, yet the cells of each layer are distinctively different. EM × 2700. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

  Epidermis

 The epidermis is epithelium composed of multiple layers of cells. 

The basal layer consists of cuboidal cells, whereas the outer layers are squamous, keratinized cells, so the whole epithelium is often described as being keratinized stratified squamous epithelium. LM × 40. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

keratinocytes

 The cells in all of the layers except the stratum basale are called keratinocytes. A keratinocyte is a cell that manufactures and stores the protein keratin. Keratin is an intracellular fibrous protein that gives hair, nails, and skin their hardness and water-resistant properties. 

 multiple layer 

connective tissue

deeper layer has vascularized. 

epidermis

dermis irregular connective , sweat gland 

loose connective tissue and fatty tissue

Dermis - four or five layers 

The epidermis is composed of keratinized, stratified squamous epithelium.

deep to superficial 

Skin that has four layers of cells is referred to as “thin skin.” 

From deep to superficial, these layers are the 

1. stratum basale, 
2. stratum spinosum,
3.  stratum granulosum, and 
4. stratum corneum.        

Most of the skin can be classified as thin skin.

Thick skin” is found only on the palms of the hands and the soles of the feet. It has a fifth layer, called the stratum lucidum, located between the stratum corneum and the stratum granulosum