Integumentary System Skin

Integumentary system Skin Adnexal structures (nails, hair, and glands). 

Protects against drying unnecessary loss or addition of water to the body. Glands produce secretions Nerve endings interact with the environment.

Glands assist with the elimination of certain body wastes materials.

Vitamin D is manufactured in the skin when skin is exposed to ultraviolet radiation.

Skin Layers

Epidermis most superficial stratified (thick) epithelium may contain up to one hundred layers of cells. 

Epidermis  All of the cells of the epithelium form near the junction of the epidermis and the dermis.  As new cells are formed, they push the older cells closer to the skin surface.

Epidermis  The cells in the upper layers of the epidermis are dead. 

Epidermis epithelium lacks a direct blood supply depends upon the underlying connective tissue for nutrients. 

Epidermis  As the thickness of the epithelium increases, the cells move too far from the supply of nutrients to survive.  The upper layers of dead cells are constantly shed into the environment

Epidermis upper epithelium cells contain keratin. Keratin: waxy material that helps to create the water barrier to keep water in and out of the body makes the cells a bit more rigid helps resist penetration by microbes reduces damage from friction.

Dermis lies deep to the epidermis. contains most of the glands, blood vessels, nerve endings, and hair follicles. 

Dermis Small, finger-like projections from the dermis extend into depressions on the epidermis.  This helps to firmly hold the epidermis and dermis together.

Dermis melanocytes Produce melanin, a yellow-brown pigment, colors the skin and hair.  They "inject" the melanin into the cells of the epidermis.  produce melanin in response to exposure to UV-radiation. 

Dermis The lower layer of the dermis is made of strong collagenous connective tissue.  The collagen fibers in this tissue are arranged randomly and in all directions, which help the skin to resist damage due to tearing

Subcutaneous layer actually the junction of the skin to the underlying tissues.  Mostly made of fat, insulates the body and prevents heat loss.  women tend to have a thicker subcutaneous layer than men.

Adnexal Structures hair, nails, and glands of skin

Adnexal Structures Hair produced by a hair follicle and consists of dead, highly keratinized cells.   produced by cells of the hair bulb

Adnexal Structures Hair As new cells are formed, they push the older cells towards the surface.   The amount of melanin placed into the cells determines hair color

Adnexal Structures Nails made of highly keratinized dead cells The nail is produced by cells of the nail root, which lies near the base of the nail.  As new cells are made, the older cells are pushed towards the end of the finger. 

Exocrine glands that have ducts. Skin glands are like this

Types of Exocrine Glands Merocrine  very watery secretion. released as it is made.  can be produced in large volume in a relatively short period of time.  usually have very little odor to them.

Types of Exocrine Glands Apocrine gland more viscous (thicker) secretion has some odor.  (often bacterial action on the secretion) secretion is surrounded by a small piece of the cell membrane

Types of Exocrine Glands Holocrine gland Very thick secretion Often has an odor to it.  Entire cell is removed during secretion.  cell ruptures to release the secretion.  Or cell must leave the gland carrying the secretion along with it.

Skin Glands sudoriferous glands sweat glands. 2 varieties.

Skin Glands First sudoriferous most of the surface of the body / produces a very watery sweat using a merocrine form of secretion used to help cool the body.

Skin Glands Second sudoriferous groin and armpit areas more viscous (thicker) type of sweat.  an apocrine type of secretion tends to have an odor to it.

Skin Glands Sebaceous gland oily secretion Holocrine method. usually attached to the hair follicle root of the hair.  This oily secretion coats the hair and works its way to the skin surface Keeps skin and hair from drying out. 

Skin Glands Ceruminous glands canal of the ear produce the earwax. holocrine type of secretion earwax is used to collect debris that enters the ear canal.

Mammary gland produces milk The breast is a complex structure that contains numerous different glands.  Some of the glands of the breast produce the milk fat.  Others produce the other components of the milk.