The Integumentary System

Nicholas Vogt

11/27/2017

ST-112

Ms. T. MickleMcLemore

The Integumentary System

            The integumentary system makes up the skin to protect us from outside forces. It helps keep our temperature regulated, protects us from infections, and balances fluids. Five percent of your bodies blood volume is within the skin. The integumentary system includes the skin, hair, nails, oil glands, and sweat glands. It is the largest organ in the body covering approximately 1.5 to 2 square meters of surface area. The skin is composed of two layers, the epidermis, and the dermis. There is also the hypodermis which is directly under the skin and is still a part of the integumentary system. The skin has corpuscle receptors which work with the nervous system to help sense with touch and pressure.

The epidermis is the top layer of the skin. The epidermis is mostly made up of keratinocytes which are the building blocks for the tough fibrous protein, keratin. Keratin gives the epidermis durability, structure, and makes it waterproof. The epidermis produces enough keratinocytes to fully replace your epidermis every four to six weeks. The epidermis contains melanocytes, which create melanin, the pigment that gives your skin color. Whether your skin is dark or light, the number of melanocytes are about the same. There are Langerhans cells, which are immune cells that absorb unwanted and foreign cells and bacteria. And lastly, the epidermis has Merkle cells that work with the nerves to create a sensory receptor to touch.

            There is the thick skin of the epidermis, as well as the thin skin. Thick skin is a tougher part of skin found on the soles of your feet and the palms of your hands. The rest of your body is covered in thin skin. The epidermis has five layers of the thick skin and four in the thin skin. The first layer is the horny layer also known as stratum corneum. It is the roughest layer made up of twenty to thirty sheets of dead keratinocytes. The second layer is the clear layer also known as stratum lucidum. This layer holds two to three layers of dead clear keratinocytes and is only found in the thick skin. The third layer is the stratum granulosum which contains living keratinocytes that are producing keratin. The fourth layer is the spiny layer also known as stratum spinosum. This layer is near where mitosis of the cells happens. The fifth and final layer of the epidermis is the basal layer also known as stratum basale. The basal layer is a single layer of columnar cells, it is where most of the new-cell production takes place. The basal layer also connects the epidermis to the dermis.

            The dermis contains elastic fibers and collagen, as well and blood vessels and capillaries. The dermis also contains nerve fibers that process sensations like pressure, temperature, and pain. It also houses parts of the sweat and oil glands and hair follicles. The dermis is composed of two layers. the upper papillary layer is composed of a thin sheet of areolar connective tissue that is riddled with peg-like projections called dermal papillae. Dermal papillae cause friction ridges in the thick skin, also known as fingerprints. Beneath is the reticular layer, it is the thicker part of the dermis making up eighty percent of the whole dermis. The reticular layer is made up of irregular dense connective tissue. Both the nerve fibers and the blood vessels are distributed between both layers of the dermis, so when you get cut and you feel pain and bleed that is because you went past the epidermis and lacerated the dermis.

            The hypodermis, while not a part of your skin, is still part of the integumentary system. The hypodermis lies right beneath the dermis. It is made up of mainly adipose connective tissue, which is pretty much just a seam of fat. It is where most of your body fat lies. It provides shock absorption, insulation, energy storage, and helps anchor the skin. When your body is lacking energy, the adipocytes can be sent back into circulation through the venous route.

The skin may change color to signal that may be one or more homeostatic imbalances. Cyanosis, which means the abnormal condition of blue, can indicate that there is poor circulation, respiratory issues, or heart failure. Since deoxygenated blood is darker in color and when seen through the skin it appears bluish. Jaundice is when the skin turns a yellowish color signifying liver issues. Yellow bile seeps into the bloodstream, turning the skin yellow. Erythema or red skin could indicate inflammation, a fever, or allergy. This happens because these conditions cause the blood vessels to expand causing more blood to flow to the surface of the skin.

            Sweat and blood vessels work together in regulating body temperature. The body excretes about half a liter of sweat a day without exercising to keep the body at a comfortable temperature. This is known as insensible perspiration. When exerting the body or when it is hot outside, the body can produce up to twelve liters of sweat a day. This is referred to as sensible perspiration. If the temperature gets cold outside the body can lose a lot of heat from the surface of the skin. To regulate heat loss the blood vessels, constrict to move the blood to the inner tissues to keep the internal organs warm and healthy. During this time, the skin may appear pale and a little bluish due to the lack of blood near the skin. The blood will return to the surface once the outside temperature is back to normal.