Integumentary AKA Skin

Introduction

Skin comprises the largest organ system in the body

Weighs approximately 17 Kg Takes up 2.0 square meters

Functions

Regulates body temp. Acts as an excretory organ Stores chlorides Manufactures vitamin D which is essential for

the mineralization of bones and teeth Serves as the most extensive and varied of

the sense organs – high concentration of sensory receptors, especially where this is critical – lips, finger tips

The Envelope

Prevents the loss of essential host constituents or the entry into the host of toxic physical, chemical and microbiotic agents

Properties go beyond a mere envelope• Is waterproof and prevents the evaporation and

escape of tissue fluids

• Becomes thick when subjected to rough treatment

• Fastened down where most likely to be pulled off

• Has friction ridges to lessen slippage – e.g., finger tips

Anatomy

Non-Homogeneous Large differences in form, color, and

consistency in various parts of the same body

Three distinct types of tissue – epidermis, dermis, and subcutaneous

Epidermis Ectodermal embryonic origin – two basic layers –

superficial and deep Two main cell types are Melanocytes or pigment

cells and Karatinocytes or epithelial cells Superficial layer is called the Stratum Corneum

• Dead layer, less than 1 micrometer thick

• Consists of several strata of dry, flattened, scaly cells without visible nuclei

• The surface cells are perpetually being rubbed away and replaced by cells from the next layer – the Germative layer

Epidermis

Epidermis

Germative Layer

AKA Basal Layer This layer is living Cell division occurs here and the cells

biochemically and functionally mature as they ascend through the more superficial layers

Elapsed time from the cell division to shedding is at least 4 weeks – in abnormal states such as psoriasis = may turn over in 4 days

Dermis

Has a mesodermal embryonic origin, similar to CT

Primarily made up of collagen, elastin, and reticulin fiber

Dermis accounts for 5% of body mass The outer aspect of dermis nearest to the

epidermis is called the papillary dermis – rich in nerves, vessels, and various sensory receptors

Dermis

Dermis

The deeper dermis is called the Reticular Dermis that contains the cutaneous vascular network

These vessels subserve the thermoregulatory functions

Also, there are more neuroreceptors and lymph glands

Subcutaneous Tissue

Deep to dermis Fatty structure of various thickness Functions as a thermal barrier and

protective cushion AKA superficial fascia or tela subcutanea

Subcutaneous Tissue

Skin Color

Due primarily to melanin, a pigment in the epidermis and to carotene, a pigment in dermis as well as the blood in the capillaries of the dermis

Melanin is synthesized in cells called melanocytes – found in basal layer

Number of melanocytes is essentially the same in all races. Therefore, differences in skin color due to the amount of pigment the melanocytes produce and disperse

When skin is exposed to ultraviolet radiation – enzymatic activity is increased and both the amount and darkness of melanin increase and the skin darkens as a protective measure

Sweat Glands

Two types – eccrine and sebaceous Eccrine – produce watery sweat that reaches

the surface of skin – found in very high concentration throughout the body and serve to regulate temperature

Sebaceous – are outgrowths of hair follicles into the dermis• Are filled with cells which secrete greasy substance

called sebum and give skin a greasy feels and make the skin waterproof

• Are found in high concentration in upper torso

Sweat Glands

Hairs Are distributed throughout the whole body except

selected areas May be short or long Have a shaft which projects beyond skin surface, a

root that lies in a follicle of the skin and a bulb Hairs last 2-4 years on head, 3-5 months on an

eyelash The erector pili muscles are bundles of smooth

muscle that pass next to the hairs, are involuntary, cause hairs to stand up, typically an ANS reaction to fear

Hairs

Hairs

Brief Overview of Burns

1st degree – damages only epidermis, a sunburn with reddening of the skin

2nd degree – burn destroys much of the epidermis but leaves some epidermal remnants• Re-growth from remnants is possible

• Blisters are common and pain is often severe since the skin nerves are irritated by the products of cellular destruction

1st Degree Burn

2nd Degree Burn

Burns

3rd Degree – reaches to and thru dermis – often exposing muscle and bone

No epidermal remnants are present Little or no feeling because of destruction

of nerves Treatment requires skin grafts to provide

epidermal cells Healing is slow at best

3rd Degree Burn

Major Problems of Burns

Infection Maintaining fluid Maintaining electrolyte balance which

requires food and fluid intake Contractures of skin and underlying CT

and muscle (all soft tissue) due to intense scarring

Other Common Problems with Skin

Decubitus Ulcers – AKA bed or pressure sores• Caused by constant deficiency of blood to

tissues overlying a bony prominence subjected to prolonged pressure – especially if CNS or PNS not functioning fully

• Tissue breakdown leads to infection, necrosis, etc.

Heel Decubitus ulcer

Deep Lesion

1st Level of Healing

Healing

Further Healing

Skin Problems Skin Cancer Prolonged overexposure to sunlight is primary cause

with higher risk for fair skin South and southwest have higher incidence Main types Basal Cell – most common

• Appears as small, shiny, fleshy nodules on the head, neck and/or hands

• Untreated, the nodular lesions will begin to bleed, crust over, and repeat the cycle

• Does not metastasize – may cause localized destruction of tissue

Basal Cell

Problems

Squamous Cell Nodules or red, scaly, plate-like patches

that are sharply outlined Typically develops on ear, lips, mouth

and can metastasize Cure rate for basal and squamous is

95% if treated

Squamous Cell

Squamous Cell

Problems Melanoma Uncommon Serious, can metastasize, can lead to death Appears as a dark brown or black mole-like growth

with irregular borders and irregular pigmentation Lesions may turn shades of gray, blue and white Most common sites are upper back in males and

female, anterior body in males, lower legs in females

Melanoma

Melanoma

Melanoma