Body Systems & Their Functions

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It is difficult to imagine a subject closer to you than the topic of human body systems and their functions. After all, you are inside a human body right now! While human anatomy is a complex subject, breaking it into its recognized organ systems simplifies the relationships within the body.

TL;DR (Too Long; Didn't Read)

TL;DR (Too Long; Didn't Read)

The human body comprises 12 distinct human body systems, and their functions reflect their names: cardiovascular, digestive, endocrine, immune, integumentary, lymphatic, muscular, nervous, reproductive, respiratory, skeletal and urinary.

Body System Definition

Like most subjects in biology, scientists approach body anatomy from a systems perspective, identifying levels of organization from simple to complex. When considering the human body, the most simple component is the cell. A group of similar cells form tissues, and those tissues comprise organs with distinct functions that support human life. Organs that work together to carry out coordinated activities classify into organ systems.

Integumentary, Muscular and Skeletal Systems

These organ systems comprise the basic structure of the human body. The integumentary organ system includes the hair, nails and skin and acts as a barrier between the interior of the body and the outside world. It protects the body from damage and infiltration by microorganisms, and also keeps the fluids inside the body and helps maintain body temperature. The muscular system includes cardiac, skeletal and smooth muscles that enable the body to move, as well as offering support and heat generation. The skeletal system comprises bones, cartilage, ligaments and tendons. Its functions include supporting the body, preventing damage to soft tissues, enabling movement and making blood cells.

Cardiovascular, Nervous and Respiratory Systems

The next systems perform life-sustaining activities. The cardiovascular system includes the blood, heart and vascular network. This system moves nutrients and waste products through the body and assists with maintaining body temperature and pH. The nervous system includes the brain, nerves, sensory organs and spinal cord. As a unit, it gathers and utilizes information, and controls short-term modifications in other systems. The respiratory system comprises the bronchi, diaphragm, lungs, mouth, nose and throat. This system manages breathing, transporting air to facilitate gas exchange.

Digestive, Reproductive, and Urinary Systems

These systems and their important functions are familiar to most people. The digestive system includes the esophagus, intestines, gallbladder, liver, mouth, pancreas, salivary glands and stomach. These organs work together to process food and absorb nutrients and water. The reproductive system comprises fallopian tubes, ovaries, penis, prostate, seminal vesicles, testes, uterus, vagina and vas deferens. This system makes gametes and sex hormones that enable humans to produce offspring. The urinary system includes the bladder, kidneys, urethra and ureters. Its purpose is to remove waste products and excess water from the body.

Endocrine, Immune and Lymphatic Systems

The final organ systems may be less familiar since their functions are less tangible – although no less vital. The endocrine system contains the adrenals, ovaries, pineal, pituitary, testes and thyroid. These glands work together to send hormonal messages through the body and control long-term alterations in the body systems. The immune system includes adenoids, leukocytes, spleen, thymus and tonsils. Its function is defense against pathogens and diseases. The lymphatic system comprises lymph, lymph nodes and lymph vessels. This system defends the body against infections and diseases, and also moves lymph between the blood and tissues.


About the Author

Melissa Mayer is an eclectic science writer with experience in the fields of molecular biology, proteomics, genomics, microbiology, biobanking and food science. In the niche of science and medical writing, her work includes five years with Thermo Scientific (Accelerating Science blogs), SomaLogic, Mental Floss, the Society for Neuroscience and Healthline. She has also served as interim associate editor for a glossy trade magazine read by pathologists, Clinical Lab Products, and wrote a non-fiction YA book (Coping with Date Rape and Acquaintance Rape). She has two books forthcoming covering the neuroscience of mental health.

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