An organ is a collection of tissues joined structurally that have a common function. Functionally related organs cooperate together to form organ systems. Essentially organs work together to serve functions for the overall well-being and recycling of the body’s energy.
The functions of organs and organ systems tend to overlap; in these cases, it is particularly useful to discuss the connection and shared functionality between the organs that overlap. The human body has 11 distinct organ systems that work in unison to keep the body functioning optimally:
The Cardiovascular System
Major Organs: Heart, Blood vessels (arteries, veins, and capillaries)
The cardiovascular system, combined with the respiratory system form the basis for the circulatory system in the human body, supplying tissues with nutrients and oxygen, while allowing waste and carbon dioxide to be excreted from the tissue. Capillaries are the single celled veins that form the wall between tissue and arteries and tissue and veins.
Artery walls are thick and are pressured to pump blood from the heart to the organs. The aorta, pulmonary artery, femoral arteries, the carotid arteries, and the coronary arteries. Oxygen rich blood flows through the arteries from the heart to the various organic tissue within the body.
Veins carry oxygen depleted and carbon dioxide back to the heart from the bodies various tissues. Veins are much thinner than arteries, but have valves to help keep the blood flowing in one direction. The superior vena cava, the inferior vena cava, the pulmonary vein, the jugular veins and the great saphenous veins are all major veins in the body that can be considered the most prominent.
The Digestive System
Major Organs: Mouth, Teeth, Salivary Glands, Tongue, Pharynx, Esophagus, Liver, Gallbladder, Stomach, Small Intestine, Large Intestine, Pancreas, Appendix, Colon, Rectum, Anal Canal
The digestive system is a group of organs working together to convert food sources into energy for the body to assimilate, then use. This is the primary mover of the bodies energy; it allows for processing and absorption of the environment. From the time food enters through the mouth, it is being digested by enzymes in mucus. Remember to chew your food well, the more broken down the food is, the easier it is to digest.
The Respiratory System
The respiratory system is a series of organs responsible for intaking oxygen from the atmosphere and expelling carbon dioxide back into the air. This basic gas exchange between the body and the atmosphere is completely dependent upon the respiratory system. This exchange affects every other system, as they oxygenation of blood is necessary in every organ. The nervous system also seems to draw energy from the respiratory system, and the cardiovascular system takes cues to determine how much blood it should be pumping based on breath rate.
Yoga focuses primarily on the respiratory system’s functioning to move the muscular-skeletal system. The respiratory system is vital to the functioning of every mammal on the planet.
The Nervous System
Major Organs: Brain, Spinal Cord
The nervous system is the body’s communication network. It begins in the brain and runs through the brainstem down the spinal cord and into the extremities. Sensations are felt at the fingers via pressure receptors, then are sent through the body’s nerves to the spinal cord, then up into the brain. The nervous system consists of nerves, which are specialized cells used to transmit and receive information.
Nervous tissue first arose with worms over 500 million years ago. The simplest worms have a few hundred nerve cells, while humans have over 100 billion nerve cells. Neuroscience is the field that studies the nervous system in detail.
The brain is the control center of the body. It is where all information stems and must eventually return to be processed.
The Muscular and Skeletal Systems
The muscular and skeletal systems, though distinctly different, belong together. Muscles move bones through space and bones support organs as they move through space. Together, muscles and bones create the support structure that is your body. Bones are organs, they grow as you do and fuse together as you mature. This system is intricately related to the nervous system, as the three work together to provide a functional feedback loop within the body so that as it moves, it can adjust to the environment.
The muscular-skeletal system requires constant maintenance, as it would have been the primary means of survival in humanities beginnings. Many of the problems in the modern world result from not using this system properly, or often to ensure that it maintains itself in a healthy and optimal way.
The Urinary System
Major Organs: Kidneys, Ureter, Urinary Bladder, Urethra
Humans produce on average 1-2 liters of urine per day, the urinary system is the removal of urea and uric acid. The kidney receives about 20% of the blood from the heart to break down into urine.
The urinary system also assists in regulation of electrolytes, ph balance of the blood, and controlling blood volume and pressure. This is the bodies balancing system for the blood stream and is used in the wild extensively for communication between animals in similar areas. marking territory, or submissiveness uses the urinary system.
The Reproductive System
The reproductive system are sex organs. They allow for reproduction while insulating vital organs from infection and bacteria (ideally). This allows for the combination of genetic material of two individuals. Hormones affect the growth and maturation of sex organs and many other systems are involved in the creation of offspring, but the sex organs are the primary movers of the genetically encoded cells required for reproduction.
The Lymphatic System
The lymphatic system is a circulatory system that carries lymph, a clear liquid (from the word for “water” in Latin) towards the heart. This is an open system that allows for excess plasma in the blood stream to get re-introduced after storage. This is the primary function, along with functioning of the immune system.
Lymph contains plasma, but also white blood cells, lymphocytes, waste, bacteria, and proteins. Lymphocytes, a type of white blood cell concentrated in the lymph nodes, is very present in the spleen, tonsils, thymus, bone marrow, and lymphatic digestive tissue.
The lymph system does not have a primary mover, as the circulatory system has the heart, though some animals have lymph hearts. It is moved via the muscular-skeletal and digestive systems, but it remains an open system. Bone marrow is responsible for the creation of T cells, which then move to the thymus for maturation. Afterwards, they combine with B cells in search of pathogens, but 95% of the cells begin aptosis (preprogrammed cell death).
The Endocrine System
Major Organs: Pineal Gland, Pituitary Gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus, gastrointestinal tract, and adrenal glands
The endocrine system is a collection of glands that secrete hormones into the circulatory system that are carried towards target organs. These are information signals similar to the nervous system, yet its effects and mechanisms are much different. These are slower, more gradual effects, take longer to process and effect the system and are slower to stop affecting the system as a whole. The hypothalamus is the seat of control of the endocrine system in all vertebrate mammals. Many other organs also have secondarily endocrine functions for the body.
The endocrine system quickly becomes chemistry and cell biology, so we will revisit this in detail in a future article. But essentially, the endocrine system is responsible for changing the body slowly, such as in growth, maturation, disease, reproduction, puberty, menopause, and many other common events we see as humans age.
The Integumentary System
The integumentary system protects the body, including from loss of water or abrasion. It serves a variety of functions: waterproof, cushioning, and protecting deeper tissue, excreting wastes, regulating temperature, and is the attachment site for sensory receptors to detect pain, sensation, pressure, and temperature. The skin, nails, feathers, hair, scales, and hooves are all part of the integumentary system. It also allows for vitamin D synthesis in conjunction with the sun.
The skin is the largest organ in the body and is integral to functioning, containing 12-15% of our body weight. There are three layers, the epidermis, the dermis, hypodermis. The epidermis is the outermost wall of skin. Keratin stiffens epidermal tissue to form fingernails. Keratin aids in protection. The system also protects against a variety of things: UV rays, body maintenance, protection from dehydration, excretion of waste through perspiration, protecting internal organs, and much more.
The body is a complex playground of intermingling chemical and biological behaviors, many of which are listed here, most of which are not. I will continue to write articles about the most interesting aspects of these system, but let me know what else you want to know about!
Please let me know if you have any questions about what’s here. Thanks for reading!