A Look Inside the Human Body
A look inside the human body reveals a fascinating network of interrelated systems and organs whose responsibility is to make the body function properly. Although each system has its own primary function, they work together in a coordinated fashion, much like the parts of a car collaborating to make it run efficiently. The following is a general overview of the components of blood and five body systems found inside the human body.
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Blood
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Blood is the vital component that delivers oxygen and nutrients to every body organ and system, and people need it to survive. Blood is made up of three types of cells: red blood cells, white blood cells and platelets. Red blood cells transport oxygenated blood throughout the body, while the primary function of white blood cells is to fight infection. When you get a cut, it is the blood's platelets that aid in the clotting process. In addition to delivering oxygen and nutrients, blood also carries bodily wastes to the lungs, kidneys and digestive organs so they can be expelled.
Digestive
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The digestive system is made up of a series of hollow organs that include the mouth, esophagus, stomach, small and large intestines, rectum and anus. The function of the digestive system is to break down and absorb food so that it can be used by the body. Two solid organs, the pancreas and liver, secrete digestive juices into the intestines to break down food into microscopic components that are then absorbed by the blood. Peristalsis, a series of wavelike contractions, propels food through the digestive system.
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Cardiovascular
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Humans have what is referred to as a closed circulatory system. In other words, chemicals are exchanged by diffusion rather than released directly into the bloodstream. The cardiovascular system is made up of the heart, arteries and veins. As a general rule, veins carry deoxygenated blood to the heart, and arteries carry oxygen-rich blood to other organ systems. The exception is the pulmonary artery, which carries deoxygenated blood from the heart to the lungs, where it then becomes oxygenated. Humans are equipped with a double circulation system. The pulmonary circuit serves the lungs, and the systemic circuit serves the rest of the body.
Musculoskeletal
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The musculoskeletal system gives people the ability to move. It is made up of muscles, bones, ligaments, joints and tendons. Connecting muscles to bones are the tendons. Ligaments, white bands of tissues, form the joints that allow the bones to bend and work together. The musculoskeletal system also provides protection to internal organs. For example, the hard skull protects the brain, while the heart and lungs are kept safe behind the ribs.
Central Nervous
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The central nervous system is composed of the spinal cord and brain. The spinal cord transmits sensory information from the peripheral nervous system to the brain and then relays motor information from the brain to the rest of your body. For example, when you touch a hot stove, your brain receives the message that your hand hurts. As a result, your brain sends a message for you to quickly remove your hand from the hot stove. Additionally, your brain receives sensory input from the olfactory and optic nerves that are connected to your nose and eyes.
Endocrine
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The endocrine system uses chemical messages, called hormones, to communicate with various body organs. These hormones are made and secreted by endocrine glands and released directly into the blood stream. Once in the blood stream, they target specific cells. There are three groups of hormones. Steroid hormones include prostaglandins and sex hormones. Amino acid derivatives, like epinephrine, are composed of amino acids. Peptide hormones are the most numerous and include insulin. Major endocrine glands include the hypothalamus and pituitary glands, thyroid, pancreas, adrenal glands and gonads. One of the least studied and least understood, the pineal gland, is responsible for the production and secretion of melatonin, which is the chemical that makes people feel sleepy.
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