INTEGUMENTARY SYSTEM 2

• Most common type of cancer.

  skin cancer
• Most skin cancers result from damage caused by the ultraviolet (UV) radiation in sunlight. Some skin cancers are induced by chemicals, x-rays, depression of the immune system, or inflammation, whereas others are inherited.
• the most common type of skin cancer.

  It affects cells in the stratum basale.

  Removal or destruction of the tumor cures most cases.

  basal cell carcinoma
• Is the 2nd most common type of skin cancer.

  It affects cells in the stratum spinosum and can appear as a wart like growth.

  Removal or destruction of the tumor cures most cases.

  squamous cell carcinoma
• Least common but is the most deadly, 77% of the skin cancer deaths in the United States.


  melanoma
• If the melanoma is only in the epidermis layer then the cancer is treatable.
• if the melanoma invades the Dermis and metastasizes to other parts of the body, it is difficult to treat and can be deadly.
• The accessory skin structures include the hair, glands, and nails.
• Hair is found everywhere on the skin except the palms, the soles, the lips, the nipples, parts of the external genitalia, and the distal segments of the fingers and toes.
• Is divided into the shaft, which protrudes above the surface of the skin, and above the root, located below the surface.


  hair
• White hair happens when hair follicles lose melanin.
• Alopecia/Baldness: disease that happens when our immune system is attacked
• Soft , fine hair that develops and covers the fetus while in the fifth or sixth month of fetal development.

  lanugo
• Long, coarse and pigmented hairs that replace the lanugo of the scalp, eyelids and eyebrows

  terminal hairs
• Usually replaces the Vellus hairs in the pubic and axillary regions of the body at puberty. 


  terminal hairs
• Short, fine and usually unpigmented which usually replace the lanugo on the rest of the body.

  vellus hairs
• The base of the root is expanded to form the hair bulb.
• Hair is divided into the shaft, which protrudes above the surface of the skin, and the root, located below the surface.
• -Most of the root and the shaft are composed of columns of dead, keratinized epithelial cells arranged in 3 concentric layers. Medulla, Cortex, Cuticle.
• It is the central axis of the hair.

  Consists of 2 or 3 layers of cells containing soft keratin. 


  medulla
• Surrounds the medulla.

  Forms the bulk of the hair.

  The cells of the cortex contain hard keratin.


  cortex
• Covers the cortex.

  A single layer of cells also contains hard keratin.

  The edges overlap like shingles on a roof.

  cuticle
• Tubelike invagination of the epidermis that extends into the dermis.

  A hair develops and grows within each hair follicle.

  hair follicle
• Consists of a dermal root sheath and an epithelial root sheath.


  hair follicle
• Is the portion of the dermis that surrounds the epithelial root.

  dermal root sheath
• At the opening of the follicle, the external epithelial root sheath has all the strata found in thin skin.
• The internal epithelial root sheath has raised edges that mesh closely with the raised edges of the hair cuticle and hold the hair in place.
• epithelial root sheath

  Deeper in the hair follicle, the number of cells decreases until, at the hair bulb, only the stratum basale is present.
• Is an expanded knob at the base of the hair root.

  hair bulb
• It is inside the hair bulb and is a mass of undifferentiated epithelial cells.

  Produces the hair and the internal epithelial root sheath.

  matrix
• The dermis of the skin projects into the hair bulb.

  Within the hair papilla are blood vessels that provide nourishment to the cells of the matrix.

  hair papilla
• Hair is produced in cycles that involve a growth stage and resting stage.
• Eyelashes = 30 days and rest for 105 days
• Scalp hair = 3 years and rest for 1-2 years.
• 90% of the scalp hairs are in the growing stage, and loss of approximately 100 scalp hairs per day is normal.
• Smooth muscle cells that are associated with each hair follicle.

  arrector pili
• The major glands of the skin are the sebaceous glands and the sweat glands.
• Located in the dermis.

  Are simple or compound alveolar glands that produce sebum.

  Classified as holocrine glands. 


  sabaceous glands
• A few sebaceous glands located in the lips, the eyelids (meibomian glands), and the genitalia are not associated with hairs but open directly onto the skin surface.
• sebum


  An oily, white substance rich in lipids. Released by the lysis and death of secretory cells.