All About the Human Body
Article Written by Dr. David A. Sieber
The human body is amazing! It’s made of many parts, including one’s bones, heart, lungs, skin, and muscles. Each of these parts fulfills an important role that makes human life possible. Together, they comprise the various systems in the body. When they all work together and function properly, it is called homeostasis. Knowing and understanding these systems can help people stay healthy.
The Skeletal System
The skeletal system is the body’s supporting structure. Without a skeletal system with about 206 bones, it would be impossible to stand up, sit up or move around. Besides supporting the body, bones also help protect internal organs. Joints connect bones, making moving your arms and legs possible. The skeletal system also produces blood cells that carry oxygen throughout the body. Without our skeletal system, people wouldn’t have a shape or be able to stand up and move around.
The Muscular System
The muscular system comprises over 600 muscles that make movement possible. There are three types of muscles in the body. These muscles are the skeletal, smooth, and cardiac muscles. Skeletal muscles are those that are attached to bones by tendons. They are the ones that people consciously control and move and are known as voluntary muscles. Skeletal muscles move one’s head, arms, and legs.
Smooth and cardiac muscles are involuntary. This means they move on their own without conscious thought or effort. Smooth muscles are in the stomach, bladder, and intestines. The cardiac muscle is the heart muscle.
Cardiovascular /Circulatory System
The cardiovascular or circulatory system includes the heart, blood vessels, and blood. When a person’s heart beats, it pumps blood and travels throughout the body using blood vessels. As blood moves, it carries and delivers oxygen and nutrients to organs and tissues. Another essential function of the cardiovascular/circulatory system is to remove waste materials and carbon dioxide.
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Digestive System
Most people love to eat because of the taste and smell of food. However, food’s actual value is what happens after it enters the digestive system. Digestion is necessary to break down food into the nutrition and energy that one’s body needs to remain healthy and strong. The parts of the digestive system include the mouth, esophagus, stomach, small intestine, large intestine, and anus, as well as other organs such as the pancreas, liver, and gallbladder.
The digestion process starts when food first enters one’s mouth, where chewing breaks it into smaller and digestible pieces. From there, food makes its way to the stomach, which mixes with digestive juices before entering the small intestine. In the small intestine, the absorption of nutrients takes place. The next stop is the large intestine, where the remaining water and nutrients are removed. What remains is stool, or solid waste, which is stored in the rectum until it leaves the body out of the anus.
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Nervous System
A person’s ability to process information and respond to their environment happens courtesy of the nervous system. The parts of the nervous system include the brain and spinal cord and a system of nerves that travel and carry signals throughout one’s body. Together, these parts create the central and peripheral nervous systems. The brain and spinal cord make up the central nervous system, while the system of nerves makes up the peripheral nervous system. The brain controls emotions and the thought process. Nerves carry neurons that are sent by the brain to control body functions. Nerves carry these neurons to the body and back again.
Respiratory System
Human life can’t exist without the ability to breathe oxygen. One’s ability to breathe is possible because of the parts of the body that make up the respiratory system. These include the nose, throat, lungs, trachea, and bronchial tubes. Every time a person breathes in or inhales, their lungs fill with air. The oxygen enters the bloodstream, where it travels through the body. When a person breathes out or exhales, their lungs deflate and expel carbon dioxide from the body.
Endocrine System
The endocrine system helps to regulate a person’s mood, growth, development, and other biological processes in the body. This system includes glands, such as the thyroid, adrenal, and pituitary glands. Endocrine glands are also in the ovaries and testes. These glands release hormones into the bloodstream, which is why it is sometimes called the hormone system.
Hormones act like messengers that tell parts of the body what to do. Their specific purpose depends on the gland that releases them. The pancreas, for example, releases hormones that help to control blood sugar.
Urinary System
Whenever a person has to pee, it’s their body wanting to flush out liquid waste. The urinary system makes it possible to remove this waste, which is toxic if left in the body. Parts of the urinary system include the kidneys, ureters, bladder, and urethra.
A person’s kidneys are very important to the urinary process as they act like filters to remove waste from the blood. This waste mixes with water and becomes urine. Urine travels down to the bladder where it stays until it’s flushed from the body when a person has to urinate.
Immune/Lymphatic System
The immune system is a system that protects the body from infections and germs that can cause illness. In this system, tissues, cells, and organs work together to defend the body. It includes the lymphatic system, which also helps protect the body from infections by draining a watery substance that contains white blood cells and protein from tissues and into the blood. This substance is called lymph. Lymph drainage is important to prevent it from building up in tissues, which can cause problems like swelling. The organs that make up the lymphatic system include the thymus gland, bone marrow, tonsils, appendix, spleen, Peyer’s patches, lymph vessels, and hundreds of lymph nodes.
Reproductive System
The reproductive system makes it possible for people to have children. Reproductive organs are different depending on a person’s gender. Female reproductive organs, for example, include the ovaries, which contain eggs or ova. Other female organs include the uterus, cervix, fallopian tubes, and vagina. The female reproductive system is responsible for menstruation, in which an ovary releases a mature egg for fertilization. If fertilization does not happen, menstruation occurs in the uterus shedding blood and its lining. If fertilization happens, pregnancy is the result.
Male reproductive organs are both on the outside of the body and inside of it. The visible organs include the penis and scrotum. Internal organs include the testes inside the scrotum, the epididymis, the prostate gland and seminal vesicles, and the vas deferens tubes. Male reproductive organs make the sperm that fertilizes the egg. Sperm are made in the testicles and matures in the epididymis.
Integumentary System
Skin, hair, and nails combine to create the integumentary system. This system protects the body by creating a barrier against environmental hazards, such as sun ultraviolet (UV) rays and germs and bacteria that would otherwise cause infection, severe injury, or even death. Skin, which has three layers, also makes it possible to feel and adjust to heat and cold and is also the largest organ.
Hair protects the body in several ways. Eyelashes and brows prevent dirt and excess water from getting into the eyes, while the hair on one’s head helps the body to keep heat. Glands in the body, such as sweat, sebaceous, and mammary glands, are also part of the integumentary system.
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