MCAT Anatomy > Human Body Systems
List of Systems
The Reproductive System is responsible producing sex cells called gametes, known as eggs and sperm in humans. Gametes are sex cells that contain exactly half the genetic material of the parent, and are produced through the process called meiosis. The gamete cells are what differentiate sexual reproduction from asexual reproduction. In asexual reproduction, there is only one parent, and the offspring of the parent cell ideally has identical genetics to the parent cell, not accounting for possible genetic mutations.
The egg gamete is produced by the female ovaries, and sperm is produced by the male testis. If everything goes right after a sexual act, the egg and sperm will meet in the uterus, where an embryo is formed and will develop until birth. The reproductive system, its functions and processes will be discussed in detail in this section.
See Digestive System
The Digestive System is used to process food and liquids to extract nutrients for our body to use for energy and to support all bodily functions. The digestive system begins at the mouth and ends at the large intestine. The digestive system is made up of the mouth, the esophagus, the stomach, the small intestine, the large intestine, and the pancreas. The purpose of the digestive system and the functions of each of its organs will be discussed in detail in this section.
The Respiratory System is responsible for gas exchange, where oxygen is brought into the body and waste products are expelled. This process occurs in the lungs, where the lungs serve as a storage unit for air, and blood in the lungs act to absorb the oxygen from the air in the lungs and expel waste products that the blood is carrying.
Oxygen is essential for ATP synthesis. ATP (Adenosine-5'-triphosphate) is responsible for transporting chemical energy within a cell to where it is needed, and is used in all known organisms. The main waste product expelled from blood via the lungs is CO2, which is a waste product created by metabolic processes (energy burning). In this section, the respiratory system, its functions, and processes will be discussed in detail.
The Circulatory System is designed to circulate nutrients, oxygen, hormones, and white blood cells throughout the body and aid in the process of waste removal, i.e. carbon dioxide. Blood, which is 55% plasma and 45% cells (i.e. red blood cells, white blood cells, etc.), is pumped throughout the body by the heart to all extremities, traveling outwards from the heart through arteries and into capillaries, which increase the surface area blood is exposed to exponentially to increase absorption of both nutrients by the body and waste products by the blood.
The blood then moves through the capillaries and into veins, which carry the blood back to the heart, which then is pumped out of the heart through the pulmonary artery, which brings the depleted blood to the lungs, where gas exchange occurs, dumping waste products and picking up oxygen. The blood is then pumped back to the heart through the pulmonary vein, and the cycle is repeated. This section will go into detail about the circulatory system, its purposes and its processes.
See Excretory System
The Excretory System functions to remove waste products and toxic substances from the body. This is very important because 1) a build up of waste products in the body can cause toxicity on its own, and 2) toxic substance can cause damage to any or all vital organs in the body. The excretory system is particularly useful in limiting the amount of done by mildly toxic substances by reducing long term chronic exposure levels. The organs of the excretory system include the liver, kidneys, bladder, urinary tract and the rectum. The excretory system, its functions and processes will be discussed in depth in this section.
See Immune System
The Immune System is there to protect our body from physical illness. Specifically, our immune system is designed to help keep our bodies void of harmful bacteria, viruses, parasites, and even objects. Antibodies and white blood cells are created to identify and eliminate foreign agents.
For example, say a patient acquires a sinus infection. The runny nose, the thick mucous, the sneeze, and the fever the patient may experience is all a result of your body’s immune response to the bacteria infecting the patients sinuses. The patient’s body is trying to expel the bacteria, and all of these symptoms are caused by the body’s immune response to infection. In this section, the immune system, its processes and functions will be discussed in depth.
See Lymphatic System
The Lymphatic System is considered part of the circulatory system. It is comprised of lymphatic vessels that serve as a transportation network for a clear fluid called lymph. Lymph is made up of interstitial fluid, the fluid that bathes and surrounds all cells, and is collected by lymphatic nodes for transportation to lymphatic nodes.
Lymphatic nodes serve as points where bacteria and viruses picked up by lymphatic fluid can be neutralized. The lymph network transports lymph towards the heart until it reached the right or left subclavian vein, where it is placed back into blood circulation. The lymphatic system, its functions and processes will be discussed in detail in this section.
See Endocrine System
The Endocrine System secretes all of the hormones necessary for proper functioning of the body, in the correct amounts. This system is made up of a number of glands that are each responsible for production of various hormones. For example, the anterior pituitary gland, part of the endocrine system, is responsible for producing growth hormone, prolactin, endorphins and trophic hormones. Various other glands produce their own specific set of hormones, which serve to regulate different bodily functions. The endocrine system, its functions, processes, and a description of the various hormones it produces will be discussed in detail in this section.
The Muscular-Skeletal System serves as both the framework (skeletal) of organisms with this system and allows for movement (muscular) of the organism. The skeleton serves both to support the various organs and tissues in our bodies and provides a means of movement at specific points in the body (joints) that provide the best leverage and the least amount of resistance for movement.
Muscles serve to move our various limbs and body parts about the joints, and even control the movements of certain organs, such as the diaphragm pulling and pushing on the lungs to cause inhalation and exhalation. This system developed over time in humans to allow for faster movement, longer range of travel, and as a means of fight or flight response to protect ourselves, as humans are known to be able to run longer distances compared to other animals. This section will go into detail about the muscular-skeletal system, its functions and processes.
See Nervous System
The Nervous System is responsible for controlling bodily functions and relaying messages between your body and your brain, which is also part of the nervous system. All bodily functions are driven and harmonized by the brain. Your brain tells your heart to beat, your diaphragm to pull and push on your lungs to cause inhalation and exhalation, it sends impulses to your limbs that cause movement, and it drives your thought processes, and different parts of the brain control each of these processes.
The brain sends these commands through nerves, which extend throughout your body. Your body can also send impulses to your brain, such as when you touch something hot or step on a nail, and these impulses in turn effects your brains next decision, such as causing you to pull your hand away from the heat source or retract your foot from the nail, preventing further damage to your body. Since they are impulses, however, and not involuntary commands, you can choose to override the impulse and continue your course of action. For these reasons the nervous system tends to be one of the most fascinating systems of the human body. The nervous system, its processes and functions will be discussed in depth in this section.