1. Urinary System
1.1. The urinary system extracts and excretes dissolved waste products from the blood.
1.2. The main organs that function in the urinary system are the kidneys and bladder.
1.3. The urinary system keeps our body healthy by removing dangerous waste products from our blood and expelling them in the form of urine. It also functions to regulate the volume of fluid and the electrolyte balance in the body, ensuring homeostasis is maintained.
2. Endocrine System
2.1. The endocrine system secretes chemical signals that allow body systems to respond to environmental changes and to one another .
2.2. It includes hormone-producing tissues of the pineal gland and pituitary gland in the brain; the thyroid gland; the adrenal glands; the pancreas; and the ovaries, and testes.
2.3. The endocrine system consists of a number of tissues that send out chemical messages – called ‘hormones’ – to the rest of the body.
2.4. The endocrine system allows the body to respond to environmental changes, and to other types of survival changes, such as the need to reproduce.
3. Musculoskeletal system
3.1. The musculoskeletal system gives the body structure and allows us to move.
3.2. The system of muscles throughout an organism operate to move the organism and stimulate the internal organs.
3.2.1. Cardiac muscle is the muscle surrounding the heart and has a crucial function within the circulatory system.
3.2.2. Smooth muscle is better at squeezing and surrounds the digestive tract to push food through.
3.2.2.1. A portion of smooth muscle covers many internal organs and is responsible for holding certain passages shut, erecting hairs, and even moving food through the gut via an action called peristalsis.
3.2.3. The skeletal muscle is best adapted to short bursts of strenuous exercise.
3.2.3.1. Skeletal muscles work by attaching to the skeleton and contracting or relaxing.
4. Lymphatic System/Immune System
4.1. The lymphatic system is responsible for absorbing fat from the digestive system, maintaining fluid balance, and supporting the cells of the immune system.
4.2. In the case of animals, we have white blood cells that can specifically target and destroy invading pathogens. These white blood cells are made in our bone marrow and stored in our blood and our lymphatic systems.
4.3. The lymphatic system is a circulatory system separate from the cardiovascular system
4.3.1. It carries water, white blood cells, and other substances, but it does not have red blood cells or platelets.
5. Reproductive System
5.1. The reproductive system facilitates the production of offspring.
5.2. It includes the ovaries, uterus, mammary glands (breasts), penis, and testes.
5.3. In humans, there are two very different reproductive systems:
5.3.1. the male system, which is primarily concerned with producing sperm and finding mates
5.3.2. the female system, which must prepare for pregnancy, childbirth, and baby care for reproduction to be successful
5.4. The major effects of the reproductive hormones are on the reproductive organs themselves, which must bring eggs for maturity and prepare uterine lining, rich in blood vessels, to nurture a possible embryo.
6. Respiratory System
6.1. The respiratory system facilitates gas exchange between cells and the environment.
6.2. The structures involved include the nasal passage, the trachea, and the lungs.
6.2.1. In humans, oxygen is taken into the body by the lungs, where it and rapidly diffuses into the blood. The lungs accomplish this by passing large amounts of blood over gas exchange membranes.
6.3. Without oxygen to fuel cellular respiration, cells begin to die within minutes. This is the primary reason that heart attacks are deadly.
7. Digestive System
7.1. The digestive system ingests food and breaks it down into usable nutrients before excreting solid waste products.
7.2. It includes the mouth, esophagus, stomach, and intestines.
7.2.1. When food enters the body, it is first chewed by the mouth to break it down into a mush that stomach acids can penetrate. In the stomach, it is treated with acids and special enzymes that break the food’s components down into more useful forms.
7.2.1.1. Finally, it passes through the intestines: being squeezed through the huge surface area of the lower gastrointestinal tract to ensure as many useful nutrients are extracted from the food as possible.
7.3. The liver helps the process of digestion by releasing substances that assist the stomach and intestines in breaking down food, and by breaking down toxic substances in the blood.
8. Cardiovascular System
8.1. The cardiovascular system is responsible for the transport of materials through the body. These substances include oxygen, nutrients, hormones, and waste products.
8.2. The cardiovascular system includes the heart, the blood, and the blood vessels.
8.3. The heart is the central pump of the circulatory system, sending blood throughout the body at very high speeds. To ensure that we get enough oxygen, the heart even pumps blood through a special circuit to send large amounts of blood through the lungs quickly.
8.4. The arteries are the oxygen-delivery system that carry oxygenated blood through the body at high speeds and pressures.
8.5. The veins are the second type of blood vessel. They are the highway that runs in the opposite direction to the arteries, returning deoxygenated blood to the return blood to the heart.
9. Nervous System
9.1. The nervous system allows us to perceive and respond to the world around us. This also includes our emotions and personality.
9.2. The nervous system includes the brain, the brain stem, and all the nerves.
9.2.1. The brain allows us to perform tasks such as decision-making, recording memories, producing emotional responses, learning, and behavior.
9.3. The nervous system allows us to sense and respond to stimuli, such as light, sound, smell, and touch from our environment.
9.4. The nervous system accomplishes all of this using highly specialized cells called neurons, which can transmit signals extremely rapidly by firing electrochemical potentials.
10. Exocrine System
10.1. These systems cover the body and regulate its exchange with the outside world.
10.2. This includes the skin, hair, nails, sweat, and other glands that secrete substances onto the skin.
10.3. Skin is our body’s first line of defense against pathogens, harmful substances, injuries, and more.
10.3.1. The skin is a surprisingly complex material, which scientists have not been able to reproduce artificially. This is because it is a dynamic tissue, which is constantly maintained by the nourishing circulatory system underneath; and by a number of glands on the outside of our skin, which secrete oils and other substances that keep our skin from drying and cracking.