Organ Systems
As you now know, there are 11 different organ systems within the human body that must constantly work to maintain a healthy internal environment. Each organ system has unique characteristics and functions. These are described below:
Integumentary
The integumentary system, or integument, is made up a cutaneous membrane (skin) and various accessory structures, some of them including hair, nails and many exocrine glands like sweat and oil glands. The integument is considered the body’s first line of defense – this is where the external environment first meets the human body. As such, one of the major functions of the integumentary system is to protect underlying tissues and organs from physical impact and abrasions as well as to protect the body from chemicals that may attempt to enter the body. These are only a few of the many functions, however. The integument also synthesizes vitamin D3, which is eventually converted in the body to calcitriol, a hormone important in calcium regulation. Maintaining and regulating body temperature is also a function of the skin, whether it is through insulation or cooling, depending on the need of the body. In addition to these functions, the skin also serves to eliminate salts, water and wastes. The body has a large amount of sensory nerves located in the integument as well. These nerves sense touch, pressure, pain and temperature.
Skeletal
The skeletal system provides structure to the body. There are about 206 bones found within the skeleton, of which 126 are of the appendicular skeletal and 80 are of the axial skeleton. In addition to this, the skeletal system also contains all of the joints, cartilages and ligaments associated with the bones. Not only does the skeletal system provide structure, but it also allows for movement. Muscles are signalled to contract by nerves and these muscles pull on specific bones so that an individual can do things like walk, run, speak, or essentially any movement you can think of. Protection is another major function of the skeleton, as internal organs are housed deep to the ribcage, skull, and pelvis, which provide a strong barrier for the softer, more vulnerable organs. Bones also serve as a major depot for the storage of minerals. Calcium and phosphate are found in very large amounts within bones and can be stimulated to be released into the blood if needed. Finally, the skeletal system is also a site for hematopoiesis, which is the production of blood cells. Red blood cells, which carry oxygen in our blood, white blood cells that fight off infection, and platelets, which help to clot blood are all produced within bone marrow.
Muscular
The muscular system’s main function, as one can imagine, is to produce movement. It is skeletal muscle that attaches to bone that is stimulated to contract and shorten to produce a movement. Imagine you are drinking a cup of coffee, the biceps muscle (biceps brachii) is one of the muscles signalled by your brain to contract and shorten, pulling on the bones in your forearm to lift the cup to your mouth. The muscular system also works to maintain posture, regulate body temperature, support internal organs, provide a depot or storage area for nutrients like fat, carbohydrate and protein, and also provide barriers within the digestive and urinary systems. Some types of muscle are under voluntary control, such as in the example of drinking coffee. Voluntary means that you can consciously perform the movement under your own control. Contrastingly, particular muscles like the ones that form some of the sphincters in the digestive and urinary system are considered involuntary, meaning your brain sends signals to these muscles to contract without you, the individual, even consciously knowing.
