Chapter 11
All Systems Go: When
The musculoskeletal system
The musculoskeletal system is made up of 206 bones and more than 600 muscles. The bones of the skeleton have tons of jobs. They provide support for the body’s framework and protect vital internal organs, brain, and spinal column. Bones store minerals necessary for growth, and red bone marrow makes blood cells. Most importantly, bones make movement possible, pro- viding attachments for muscles.
Bones are attached to other bones by ligaments, whereas tendons connect bones to muscles. A joint is where two bones meet.
Muscles attach to bone, not only making movement possible but holding the bones of the skeleton together. Muscles allow flexibility of the body and help maintain body temperature. But think about some other functions of mus- cles. There are all kinds of muscles you probably don’t think too much about.
Cardiac muscle keeps your heart beating, but the cardiac muscle is involun- tary. That means you don’t have to think about keeping your heart beating.
Muscle contraction throughout the body keeps the blood flow moving. The digestive system is lined by smooth muscle that keeps the food moving. And don’t forget the muscles that keep the bladder and colon closed up — until you voluntarily relax these muscles when you want.
The integumentary system
The integumentary system is a really fancy way of referring to the skin, hair, nails, and glands. The skin is actually the body’s largest organ (yes, it is an organ!). It covers about 20 square feet and accounts for nearly 15 percent of your body weight. Skin (obviously) provides an external covering for the body. As a protective membrane, it prevents loss of water, salt, and heat.
The skin provides a protective barrier against bacteria, pathogens, and toxins that want to invade your body. Plus, it’s full of glands that do many smaller, but equally important jobs. Sebaceous glands secrete oil to lubri- cate, whereas sudoriferous glands secrete sweat, acting as a cooling system.
Nerves are involved as well and carry impulses that act as receptors for pain, temperature, and touch. The blood vessels in the skin aid in regulating body temperature.
The sensory system
The eyes and the ears, like the skin, are sense organs. They act as the body’s external perception/alarm system by letting in light and sound. Impulses from the eyes are sent to the occipital lobe in the brain for processing, and
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Chapter 11: All Systems Go: When Systems Combine
impulses from the ears go to the brain’s temporal lobe. In these lobes of the brain, nerve impulses are translated into sound sensations and visual images that we experience as vision and hearing.
Age sure takes its toll on the eyes and ears. Presbyopia is impaired vision due to aging. Presbycusis is hearing loss occurring in old age.
Physiology Systems Working Together
Physiology is the study of the function or day-to-day operation of the parts of the body. This includes the functions of everything from the smallest cell, seen only under a microscope, to a large organ like the heart. You might think that each body part has one function to carry out and works indepen- dently on its own to accomplish this function, but in fact, most body parts are team players that work together to accomplish a task. Brisk walking, for example, not only requires the use of leg muscles, but also good lung capac- ity to keep up the pace. You know that the heart pumps blood through the body via arteries and veins, which are part of the cardiovascular system.
Without the lungs performing their function to re-oxygenate the blood as it passes through the lungs, the exchange of gases (the function of the respira- tory system) would not happen, and body cells and organs would die.
Pathology (sometimes pathophysiology) is the study of the effects of disease on body parts and the ways disease can interfere with an organ or system’s func- tioning ability.
The cardiovascular and lymphatic systems
The cardiovascular system (sometimes called the circulatory system) has many functions. Blood carries oxygen, nutrients, hormones, and lymph fluid to cells and transports waste products, carbon dioxide, and urea away to be excreted. The heart is the body’s pumping station that pumps out freshly oxygenated blood through a vast network of vessels. The heart is divided into four chambers: two upper chambers (the right atrium and left atrium (plural: atria) and two lower chambers, the right and left ventricles.
The cardiovascular system could not survive without the assistance of the muscular system — the myocardium is the heart muscle — which in turn is kept functional by the autonomic section of the nervous system.
Not to be forgotten as a team player with the cardiovascular system is the lymphatic system. This system works together with the blood to fight disease.
It looks after the body’s immune system. This system produces lymph, a fluid released into the body through lymphatic vessels, which are linked up
duces lymphocytes, the disease-fighting cells that circulate the body through blood. Lymph nodes located throughout the body act as the filtrating centers.
Lymph nodes can trap and filter toxic and malignant substances. Special cells can digest foreign substances as well as manufacture antibodies to fight off infection.
The spleen, tonsils, and thymus are accessory organs of this system, all play- ing special roles. The spleen stores red blood cells, which can be released into the body as needed. The thymus gland produces lymphoctes, the disease fighters. The tonsils are also made up of lymphatic tissue and act as a filter system for bacteria.
The respiratory system
The respiratory system provides the mechanisms that allow you to breathe.
You can’t live without it, and, as with the other systems, improper function- ing would render you dead! Now that would really ruin your day.