Skin, skin, skin, skin, skin! Its' amazing! Not only is it strong and flexible but it's also waterproof and able to cover our bodies smoothly. Judging by weight, skin is also the largest organ of the body. Do you know what else it is called? The integumentary system!
The integumentary system (our skin) is very versital and also nessesary to mantaining homeostasis. It is the house for many sensory receptors and immune system cells. Our skin synthesizes various chemicals, like vitamin D, and excretes small amounts of waste.
Our skin is split up into three layers or regions. We have the
epidermis, the
dermis, and the
hypodermis.
THE EPIDERMIS
-The epidermis is the outer layer. It lacks blood vessels because it is solely composed of stratified squamous epithelium. The epidermis is made up of four different types of cells and about 5 layers. These four cell types are
keratinocytes (produce keratin),
melanocytes (produce melanin),
Langerhans' cells(help to activate immune system), and
Merkel cells(function as receptors).
The outermost layer of the epidermis is
stratum corneum. It is composed of many layers of keratinized, flattened, and dead epithelial cells. These cells have no nucleus.
The next layer,
stratum lucidum, is found beneath the stratum corneum on the soles of your feet and the palms of your hands. the cells here appear to be clear. The nucleus, organelles, and cell membrane are not visible.
Underneath the stratum corneum and sometimes the stratum
lucidum is the
stratum granulosum. it is made up of 3-5 layers of granular cells that are flattened. They contain shrunken fibers of keratin and shriveled nuclei.
Next comes the
stratum spinosum which lies under the stratum
granulosum. This layer consists of many layers of cells with large, ovular nuclei located in their center. They have developing keratin fibers and are becoming flattened.
The deepest layer is
stratum basal or the basal cell layer. Here there is a single row of either cuboidal or columnar cells. They divide and grow. Also in this layer there are melanocytes.
DID YOU KNOW. . . Psoriasis is a chronic skin disease in which cells in the epidermis divide 7x more frequently than normal. Five million people in the U.S. and 2% of people world wide have this disease.
THE DERMIS
-The dermis is the second layer of the skin. It is what binds the epidermis to all of the underlying tissue. This layer is mostly made up of dense and irregular connective tissue that includes collagenous and elastic fibers. The networks of these certain fibers give our skin its toughness and elasticity. This provides the ability to stretch and helps resist against distortion such as sagging and wrinkles.The dermis is an average of 1-2 mm think but vary at the eyelids or the soles of feet.
There are different cell types in the dermis, including
fibroblasts,
macrophages, and the occcasional
mast cells and
white blood cells. The Dermis is split into to individual layers.
The
Papillary layer! This layer of the dermis is make of areolar connective tissue. The surface of this layer comes with peglike projections that are called dermal papillae. These little dermal papillae contain capillary loops, Meissner's corpuscles, and free nerve endings.
The second layer of the dermis is called the
reticular layer. This layer is particularly special because it makes up approximately 80% of the thickness of the skin. The collegen fibers located here provide strength and the elastin fibers provide stretching and recoiling.
THE HYPODERMIS
-The hypodermis is the third layer of the skin and also to deepest. This layer is mainly composed of adipose and areolar connective tissue.
SKIN COLOR
- We as humans come in many different colors. Three pigments in our skin contribute to this vast range of color that we have.
Melanin is a pigment that ranges from yellow to reddish-brown to black. This is the pigment responsible for darker skin colors. We get freckles and pigmented moles as a result of an accumulation of melanin in one spot.
We have a pigment that ranges from yellow to orange called
carotene. This pigment is most obvious on the soles of our feet and the palms of our hands.
Hemoglobin! This is the pigment responsible for the pinkish hue of the skin.
SWEAT GLANDS
- So you might not like it when you sweat or have those embarrassing pit stains but the truth is that sweating is healthy for you. Sweating is a function that your body does to keep you from overheating. But, of course its not just that simple. We have different types of sweat glands.
On the soles of our feet, the palms of our hands, and our forehead we have a type of sweat gland called
eccrine sweat glands.
There are
apocrine sweat glands found in the axillary and anogenital areas.
The
ceruminous glands are a type of apocrine gland in the external ear canal.
Mammary glands are a very special type of sweat gland that secrete milk.
Our bodies also have a special type of gland called sebaceous glands. These are a bunch of alveolar glands found all over the body. They are stimulated by hormones and soften the skin. These glands create an oily secretion called sebum.
HAIR!
-Hair is filamentous strands of dead kerantinized cells produced by the hair follicles. The keratin in the hair is called hard keratin and is much more durable that the soft keratin that we find in the skin. Our hair is pigmented by the melanocytes found at the base of the hair.
Our Hair has different functions including:
-maintaining warmth
-alerting the body if there are insects on the skin (nasty!)
-helping guard scalp against physical trauma and sunlight
A
hair follicle is a root sheath that extends from the epidermal surface and into the dermis. There is a knot of sensory nerve endings that wrap around each hair bulb. Because of this, our hair acts a sensitive touch receptors.
SKIN CANCER
-With skin, like all good things, there also comes complications and problems. Skin cancer is one of the bad things that can happen to our skin. There are three major types of different skin cancer.
Basal cell carcinoma is the most common type of skin cancer with over one million people in the U.S. being diagnosed with it every year. Stratum basal cells invade the hypodermis and the dermis. These cells usually stay together and do not spread. This type of skin cancer can be cured by surgical excision 99% of the time.
Squamous cell carcinoma is a type of skin cancer that comes from keratinocytes of stratum spinosum. It is the second most common type of skin cancer. This type of skin cancer grows rapidly. Luckily the prognosis is pretty good if treated by radiation therapy of removed surgically.
Melonoma is the worse skin cancer to be diagnosed with. Malanoma originates in the melanocytes. It is highly merastatic, which means is spreads easily. This type of skin cancer is also resistant to chemotherapy.
BURNS
A
first-degree burn is when only the epidermis is damages. This can cause redness, swelling, and pain at the location of the burn.
Second-degree burns happen when both the epidermis and the upper region of the dermis are damaged. With this type of burn redness, swelling, and pain might occur as well, but this burn often blisters.
The entire thickness of the skin is damaged in a
third-degree burn. at this point when the subject initially gets burned they cannot feel pain because the nerve endings are all destroyed. The burned area may appear cherry red, gray, or black.
There is a certain point where burns are considered critical.
-If over 25% of the body is covered with second-degree burns
-If over 10% of the body is covered with third-degree burns
-If there are third degree burns on the face, hands, or feet
Well, I hope I have been able to tell you a little more about the integumentary system. Thanks for reading!
