One of the human body systems is the Skeletal System. The skeletal system serves many important functions; it provides a framework for our bodies in addition to protecting our vital organs, such as the brain, lungs and heart. The skeletal system also allows bodily movement and stores minerals. Another important function of the bones is the storage of certain minerals. Calcium and phosphorus are among the main minerals that are stored within the skeleton. This storage helps to regulate mineral balance in the bloodstream. When the fluctuation of minerals is high, these minerals are stored in bone; when it is low the minerals will be withdrawn from the bone.
Another body system is the Muscular System. The muscular system is a series of different muscles, including smooth muscles, cardiac muscles, and skeletal muscle. Cardiac and smooth muscle contraction occurs without conscious thought and is necessary for survival. Examples of these muscles are the contraction of the heart and stomach. Smooth muscle or “involuntary muscle” is found within the walls of organs and structures such as the esophagus, stomach, intestines, uterus, urethra, bladder, and blood vessels. Unlike skeletal muscles, smooth muscles are not under conscious control. Cardiac muscle is also an “involuntary muscle” but is more akin in structure to the skeletal muscle, and is found only in the heart. Skeletal muscle or “voluntary muscle” is anchored by tendons to the bone and is used to effect skeletal movement such as locomotion and maintaining posture. Although this postural control is generally maintained as a subconscious reflex, the muscles responsible react to conscious control like non-postural muscles.
One of the most well-known body systems is the Digestive System. The main organs of the digestive system are mouth, esophagus, stomach, small and large intestines, appendix, and anus. Accessory organs to the alimentary canal include the liver, gallbladder, and the pancreas. In the human body, food enters the mouth, is chewed by teeth, and broken down by the saliva from the salivary glands. Then it travels down the esophagus into the stomach, where acid begins physical break down of some food, and chemical alteration of some. The “leftovers” go through the small intestine, through the large intestine, and are excreted during defecation.
The Endocrine System is made up of a group of glands that produce the body's long-distance messengers, or hormones. The endocrine system is instrumental in regulating mood, growth and development, sexual function and the reproductive processes. The endocrine system is an information signal system much like the nervous system. However, the nervous system uses nerves to conduct information, whereas the endocrine system mainly uses blood vessels as information channels. Glands located in many regions of the body, release into the bloodstream specific chemical messengers called hormones. Hormones regulate many functions of an organism, including mood, growth and development, tissue function, and metabolism.
The Nervous System is a network of specialized cells that communicate information about an organism’s surroundings and the organism itself. It processes this information and causes reactions in other parts of the body. The nervous system is divided largely into two categories: the peripheral nervous system and the central nervous system. Neurons generate and conduct impulses between and within the two systems. The peripheral nervous system is composed of sensory neurons and the neurons that connect them to the nerve cord, spinal cord and brain, which together make up the central nervous system. In response to stimuli, sensory neurons generate and spread signals to the central nervous system which then processes and conducts signals back to the muscles and glands so they can respond to the change that triggered the nerves.
The Circulatory System is an organ system that passes, gases, hormones, blood cells, nitrogen waste products, etc. to and from cells in the body to help fight diseases and help stabilize body temperature and pH to maintain homeostasis. On average, the human body has about five liters of blood continually traveling through it by way of the circulatory system. The heart, the lungs, and the blood vessels work together to form the circle part of the circulatory system. Two types of fluids travel throughout the circulatory system: blood and lymph. The blood cells, heart, and blood vessels form the cardiovascular system. The lymph, lymph nodes, and lymph vessels form the lymphatic system. Together the cardiovascular system and the lymphatic system make up the circulatory system.
The Immune System, which is made up of special cells, proteins, tissues, and organs, defends the human body against germs and microorganisms every day. The immune system is a network of cells, tissues, and organs that work together to defend the body against attacks by foreign invaders.
The Respiratory System is a biological system consisting of specific organs and structures used for the process of respiration. Respiration takes place in the respiratory organs called lungs. The route of air into the lungs to supply the body with oxygen is known as inhalation, and the passage of air out of the lungs to expel carbon dioxide is known as exhalation; this process is collectively called breathing or ventilation. In humans, the features of the respiratory system contain airways, lungs, and the respiratory muscles. Molecules of oxygen and carbon dioxide are passively exchanged, by diffusion, between the external environment and the blood.
The skeletal system also has a very close relationship with the muscular system. Without one another, they would both be problematic. The muscular system is surrounds the skeletal system, and so provides connection to allow the muscles to move. Without the skeletal system, we would be immobile. Furthermore, we would have no structure; all vertebrates would just be blobs on the ground. Finally, our most vital organs are protected by out bones (example: skull protects brain, ribs protect lungs and heart,) and without them our organs could be easily damaged.