the integumentary system skin and derivatives sweat glands oil glands hair nails
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The Integumentary System
Skin and derivatives Sweat GlandsOil Glands HairNails
Amazing Facts About Skin The skin is waterproof. The outer surface is made of dead cells. House dust is 90% skin flakes! Skin is the largest organ in the body!
It weighs 2.5 kg. Skin is elastic. If you laid skin on a flat surface, it would have an
area of 2 square meters! Your hair stands on end and you develop
“goosebumps” when the muscles in the hair follicles contract b/c you’re cold or scared.
Skin Functions
Integument – means covering Functions are mostly protective:
Mechanical damage – ex. CutsChemical damage Thermal damage – burnUV radiation – sunlightBacteria
Also insulates and cushions internal organs.
Skin Functions
Waterproof Keeps water in and keeps water out
Temp. regulationCapillaries and sweat glands both release
heat from the body Excretion
Sweat – releases toxins Makes proteins and vitamin D Contains sensors to feel touch,
temperature, pain
Structure of the Skin
The skin is composed of two kinds of tissue: The outer epidermis is made of stratified
squamous epithelium The underlying dermis is made up of
connective tissue The epidermis and dermis are firmly
connected. A burn or friction may cause them to separate
resulting in a blister.
Structure of the Skin
Deep to the dermis is the subcutaneous tissue, or hypodermis, which is mostly adipose tissue (fat).
It is not considered part of the skin, but it does protect the organs. absorbs shock and insulates the deeper
tissues from extreme temperature changes
Epidermis
The epidermis is composed of 5 layers called strata.
The epidermis has no blood supply of its own, it is avascular.
Most cells are keratin cells, which produce keratinKeratin – fibrous protein that makes the
epidermis tough & protective
Epidermis
Melanin – pigment that ranges in color from yellow to brown to blackProduced by special cells called
melanocytes When the skin is exposed to sunlight, the
melanocytes produce more of the melanin pigment and tanning occurs.
Freckles and moles are seen where melanin is concentrated in one spot.
Epidermis
Excessive sun exposure eventually damages the skin.By causing the elastic fibers to clump,
leathery skin forms.It depresses the immune system.
Overexposure to the sun can also damage DNA of skin cells, which leads to skin cancer.
Dermis
The dermis is the strong, stretchy envelope that holds the body together.
When you purchase leather goods, you are buying the treated dermis of animals.
The dermis varies in thickness very thick on palms of hands and soles of the feet,
but is quite thin on the eyelids. The dermis contains blood vessels, sweat and oil
glands, pressure receptors, touch receptors, temperature receptors and pain receptors.
Dermis
Collagen fibers are found throughout the dermis. They are responsible for the toughness of the dermis
and give the skin its elasticity. The dermis is supplied with blood vessels that play a
role in maintaining body temperature. When body temperature is high, the capillaries become
swollen and the skin is reddened and warm. This allows body heat to radiate from the skin surface.
If the environment is cool and body heat must be conserved, blood bypasses the dermis capillaries allowing the internal body temperature to remain constant.
Appendages of the Skin
The skin appendages include oil and sweat glands, hairs and hair follicles, and nails.
Each of these appendages arises from the epidermis and plays a role in maintaining homeostasis.
Includes: Oil (Sebaceous) Glands Sweat Glands Hair and Hair Follicles Nails
Sweat and Oil Glands
Sweat and oil glands are exocrine glands (they secrete substances) that release their secretions to the skin surface through ducts.
These glands reside in the dermis.
Oil Glands
Oil glands are found all over the skin, except on the palms of the hands and the soles of the feet
Their ducts usually empty into a hair follicle, but some open directly onto the skin surface.
The product of the sebaceous glands is called sebum.
Sebum keeps the skin soft and moist and keeps the hair from becoming brittle.
Oil Glands
Sebum also contains chemicals that kill bacteria, so it is important in preventing the bacteria present on the skin surface from invading deeper skin regions.
if a sebaceous gland’s duct becomes blocked by sebum, a whitehead appears
if the accumulated material oxidizes and dries, it darkens, forming a blackhead
Sweat Glands
Widely distributed in the skin More than 2.5 million per person 2 types of sweat glands:
Eccrine glands – more numerous and found all over the body, produce sweat to regulate body temperature and inhibit the growth of bacteria present on the skin surface
Apocrine glands – larger than eccrine glands, ducts empty into hair follicles, confined to the axillary (armpit) and genital areas of the body
Hair and Hair Follicles
Millions of hairs scattered all over the body Hair is a flexible epithelial structure produced
by a hair follicle. The part of the hair enclosed in the follicle is
called the root. The part projecting from the surface of the scalp
or skin is called the shaft. A hair is formed by division of the epithelial cells
in the growth zone, called the hair bulb, at the bottom of the follicle.
Hair and Hair Follicles
The bulk of the hair shaft, like most of the epidermis, is dead material and almost entirely keratinized protein.
Each hair consists of a central core called the medulla.
The medulla is surrounded by a bulky cortex layer.
The cortex is enclosed by the outermost cuticle. Hair pigment is made by melanocytes in the
hair bulb, and varying amounts of different types of melanin (yellow, rust, brown, black) combine to produce all varieties of hair color from pale blond to black.
Hair and Hair Follicles
Humans are born with as many hair follicles as they will ever have.
Hairs are among the fastest growing tissues in the body.
Hairs have muscles called arrector pili that connect the hair follicle to the dermis.
When these muscles contract, the hair is pulled upright causing “goosebumps”.
Nails
Scalelike modification of the epidermis, like the hoof or claw of other animals
Nails are mostly nonliving material, like hairs.
Nails are transparent and nearly colorless, but they look pink because of the rich blood supply in the underlying dermis.
The white crescent in the nail is called the lunula.
• It is a thickened area of the nail.
Homeostatic Imbalances of the Skin
The skin is only about as thick as a paper towel! But, when the skin is seriously damaged, nearly every system in the body is affected.
The skin can develop more than 1000 different disorders.
The most common skin disorders result from allergies or bacterial, viral, or fungal infections.
Less common problems are burns and skin cancers, but these are also more serious.
Infections and Allergies
Athlete’s foot: a fungus infection of the skin on the foot, between the toes
Boils: inflammation of hair follicles and sebaceous glands, common on the back of the neck
Cold sores: small fluid-filled blisters on the lips/mouth caused by herpes simplex (virus) infection; the virus localizes in a nerve under the skin where it remains inactive until fever, UV radiation, or emotional upset
Infections and Allergies
Dermatitis: itching, redness, and swelling of the skin that results in blistering; caused by exposure of the skin to chemicals that provoke allergic reactions (such as poison ivy)
Impetigo: lesions that form around the mouth and nose; caused by a highly contagious bacterial infection
Psoriasis: a chronic condition that may be hereditary; reddened lesions of the skin, attacks are triggered by trauma, infection, hormonal changes and stress
Burns A burn is tissue damage and cell death caused by
intense heat, electricity, UV radiation, or certain chemicals (such as acids).
When the skin is burned, the cells are destroyed. 2 life threatening problems result: The body loses its supply of fluids because they
seep from the burned surfaces. This results in dehydration and electrolyte imbalance. Fluids (including blood) must be administered to the patient.
Infection is the leading cause of death in burn victims since pathogens, such as bacteria and fungi, easily invade areas where the skin has been destroyed.
Burns
To determine how much of the body surface is burned, the rule of nines is used. The body is divided into 11 areas. Each accounts for 9% of the total body surface area, plus 1% for the genital region.
Burns
Burns are classified according to the severity as first, second, or third-degree burns.
In first-degree burns, only the epidermis is damaged. the area becomes red and swollen, not usually
painful ex. sunburn (usually)
Second-degree burns involve injury to the epidermis and the upper region of the dermis.
the skin is red and painful, blisters appear regrowth of the epithelium can occur
Burns
Third-degree burns destroy the entire thickness of the skin
also called full-thickness burns burned areas appear blackened or gray-
white in color the burned area is not painful since the
nerve endings in the area are destroyed regeneration is not possible, skin
grafting must be done cover the underlying tissues
Burns are considered critical if any of these conditions exist:
• Over 25% of the body has 2nd degree burns• Over 10% of the body has 3rd degree burns,
or • There are 3rd degree burns of the face,
hands, or feet.
Skin Cancer
Numerous types of tumors Most are benign and do not spread However, some skin tumors are malignant, or
cancerous, and they tend to invade other areas of the body.
Skin cancer is the single most common type of cancer in humans.
Most important risk factor – overexposure to ultraviolet radiation
Frequent irritation of the skin by infections or chemicals – also a predisposing factor for skin cancer
3 Types of skin cancer
Basal Cell Carcinoma – the least malignant and most common skin cancer Cancer lesions occur on sun-exposed
areas of the faceAppear as shiny, dome-shaped nodules
that later develop a central ulcer with a “pearly” beaded edge.
Slow growing 99% of cases are cured when lesion is
removed surgically.
Squamous Cell Carcinoma
Most often on the scalp, ears, hands, and lower lip
Scaly, reddened, and round elevation that forms an ulcer w/ a raised border
Grows rapidly and may spread to the lymph nodes if not removed.
Also sun-induced Curable if treated early with surgery or
radiation.
Malignant Melanoma
Cancer of melanocytes Melanoma accounts for only 5% of skin cancers. However, its incidence is increasing rapidly and it
is often deadly. Melanoma usually appears as a spreading brown
to black patch that spreads rapidly to surrounding lymph nodes and blood vessels.
The chance for survival is about 50%. Early detection helps to increase this chance.
Skin Cancer Detection ACS suggests that everyone examines skin for new
moles/spots, especially people who are frequently exposed to the sun.
ABCD rule for recognizing melanoma. Asymmetry – two sides of mole do not match Border irregularity – borders of the lesion are not
smooth Color – the spot contains areas of different colors Diameter – the spot is larger than 6mm in diameter
(pencil eraser)http://www.cancer.org/docroot/lrn/lrn_0.asphttp://www.skincancer.org/
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