CHAPTER 5- Integumentary System

The Integumentary System
Integumentary System: What I have learned?

The integument as an organ: The integumentary system includes the skin and the skin derivatives hair, nails, and glands. The integument is the body’s largest organ and accounts for 15% of body weight. It is an organ that is involved in protection and barrier function.

The derivatives of the integument:
Hair: functions include protection & sensing light touch.
Hair is composed of columns of dead, keratinized cells bound together by extracellular proteins. Hair has two main sections: The shaft- superficial portion that extends out of the skin and the root- portion that penetrates into the dermis. Surrounding the root of the hair is the hair follicle. At the base of the hair follicle is an onion-shaped structure called the bulb Papilla of the hair and the matrix within the bulb produce new hair.

Nails: participate in the grasp & handling of small things.
Nails are plates of tightly packed, hard, keratinized epidermal cells.


 

The nail consists of:
nail root: -the portion of the nail under the skin,
nail body: -the visible pink portion of the nail, the white crescent at the base of the nail is the lunula, the hyponychium secures the nail to the finger, the cuticle or eponychium is a narrow band around the proximal edge of the nail and
free edge: -the white end that may extend past the finger.
Glands: participate in regulating body temperature.
There are three main types of glands associated with the integument:


Sebaceous - Oil glands. Located in the dermis, and secrete sebum.
Sudoriferous - Sweat glands. Divided into two main types:
Eccrine - Most common, main function is regulation of body temperature by evaporation, and
Apocrine - Responsible for “cold sweat” associated with stress.
Ceruminous – Lie in subcutaneous tissue below the dermis, secrete cerumen (ear wax) into ear canal or sebaceous glands.
The Two Layers of Skin:

Epidermis – The Epidermis is the thinner more superficial layer of the skin.
The epidermis is made up of 4 cell types:
(A) Keratinocytes – Produce keratin protein a fibrous protein that helps protect the epidermis
(B) Melanocytes - produces the brown pigment melanin
(C) Langerhan Cells – participate in immune response and
(D) Merkel cells - participates in the sense of touch.
There are five distinct sub-layers of the Epidermis:

Stratum corneum: the outermost layer, made of 25-30 layers of dead flat keratinocytes. Lamellar granules provide water repellent action and are continuously shed & replaced.
Stratum lucidum: Only found in the fingertips, palms of hands, & soles of feet. This layer is made up of 3-5 layers of flat dead keratinocytes.
Stratum granulosum: made up of 3-5 layers of keratinocytes, site of keratin formation, keratohyalin gives the granular appearance.
Stratum spinosum: appears covered in thornlike spikes, provide strength & flexibility to the skin.
Stratum basale: The deepest layer, made up of a single layer of cuboidal or columnar cells. Cells produced here are constantly divide & move up to apical surface.
Dermis: is the deeper, thicker layer composed of connective tissue, blood vessels, nerves, glands and hair follicles.
The epidermis contains 3 cell types:
Adipocytes,
Macrophages and
Fibroblasts.
There are two main divisions of the dermal layer:
Papillary region - The superficial layer of the dermis, made up of loose areolar connective tissue with elastic  fibers.
Dermal papillae - Fingerlike structures invade the epidermis, contain capillaries or Meissner corpuscles which respond to touch.
Reticular region of the Dermis – Made up of dense irregular connective & adipose tissue, contains sweat lands, sebaceous (oil) glands, & blood vessels.




Hypodermis: the hypodermis is not a skin layer but lies below the dermis, and is a subcutaneous tissue which contains fat, blood vessels and sensory receptors.










“CROSS SECTION OF THE SKIN”

Clinical Considerations
Cleavage lines Cleavage lines are the tension lines in skin which follow the direction of the arrangement of collagen bundles in the dermis. Incisions along theses lines heal faster and give minimum scarring.
Burns Burns are classified according to how deep the burn has penetrated, as well as the percentage of surface area affected.
Depth;
Burns can be classified as partial or full thickness burns, first, second or third degree burns.
Partial thickness
First degree burns The burn has penetrated the epidermis only. Red and painful, only slight swelling.
Second degree burn The burn has penetrated the epidermis and the dermis. Red and painful, swelling and blistering.
Full-thickness
Third degree burn The burn has destroyed the epidermis and dermis and penetrated the hypodermis. Painless, the colour can be white, tan, brown black or red.
Surface area;;
In adults the Wallace's 'Rule of Nines' is used to work out an approximate percentage of total skin surface area that has been affected by the burn. Each area is approximately divided into multiples of 9. In infants and children (under 15) the body proportions are different and so this rule is not the same.
Body area Surface area
Head 9%
Upper limb (single) 9%
Trunk (front or back) 18%
Genitals 1%
Lower Limb (single) 18%


Skin absorption The epidermis is able to absorb lipid soluble substances and therefore certain medications can be applied to the surface of the skin.


Skin Function
Skin has several important functions;
Skin Function
Protects our bodies from trauma.
Wound healing.
Acts as a barrier to bacteria and viruses.
Produces vitamin D, essential for growth and bone maintenance.
Prevents us absorbing and losing excess water.
Secretes waste products.
Regulates our body temperature (thermoreceptors, sweat, vasodilation).
Sense what is happening in our external environment (touch, pressure, heat).
Pigments as well as hair on our heads protect us from the sun.
Secretes sebum.
Advertises sexual maturity.
Disperses scents.
Clinical Considerations
Wound healing It is important for the skin to repair quickly to prevent infection. If the epidermis is damaged it will simply heal by regrowing to cover the damaged area. If the damage reaches into the dermis and cuts the vessels, the blood will form a blood clot and healing of the wound will begin.
Phases of Wound Healing Processes of wound healing
Inflammatory Response Blood clotting occurs. White blood cells are brought to the wound site.
Migratory Phase Epithelial and fibroblast cells migrate beneath the clot and the blood vessels regenerate (angiogenesis).
Proliferation Phase Epithelial cells proliferate (epithelialisation) beneath the scab and the fibroblasts produce collagen and the wound is pulled together.
Maturation Phase Collagen fibres become more organized, pulling the wound together.