Table: Major Organ Systems - Merck Manuals Consumer Version

Major Organ Systems

System	Organs in the System	Some Major Functions of the System
Cardiovascular Biology of the Heart The heart and blood vessels constitute the cardiovascular (circulatory) system. The heart pumps the blood to the lungs so it can pick up oxygen and then pumps oxygen-rich blood to the body.... read more	Heart Blood vessels (arteries, capillaries, veins)	Pumps blood and circulates it throughout the body
Respiratory Overview of the Respiratory System To sustain life, the body must produce sufficient energy. Energy is produced by burning molecules in food, which is done by the process of oxidation (whereby food molecules are combined with... read more	Nose Mouth Pharynx Larynx Trachea Bronchi Lungs	Adds oxygen to the blood (and removes carbon dioxide from the blood)
Nervous Overview of the Nervous System The nervous system has two distinct parts: the central nervous system (the brain and spinal cord) and the peripheral nervous system (the nerves outside the brain and spinal cord). The basic... read more	Brain Spinal cord Nerves (both those that carry impulses to the brain and those that carry impulses from the brain to muscles and organs)	Directs intentional (and many automatic) actions of the body Enables thinking, self-awareness, and emotions
Skin Structure and Function of the Skin The skin is the body’s largest organ. It serves many important functions, including Protecting the body against trauma Regulating body temperature Maintaining water and electrolyte balance Sensing... read more	Skin (both the surface that is generally thought of as skin and the underlying structures of connective tissue, including fat, glands, and blood vessels)	Provides barrier protection between the inside of the body and the external environment
Musculoskeletal Introduction to the Biology of the Musculoskeletal System The musculoskeletal system provides form, stability, and movement to the human body. It consists of the body's bones (which make up the skeleton), muscles, tendons, ligaments, joints, cartilage... read more	Muscles Tendons and ligaments Bones Joints	Provides structure and allows motion of the body
Blood Overview of Blood Blood is a complex mixture of Plasma (the liquid component) Red blood cells (the oxygen-carrying component) White blood cells (the cells that defend against infection) Platelets (particles that... read more	Red blood cells, white blood cells, and platelets Plasma (the liquid part of blood) Bone marrow (where blood cells are produced) Spleen Thymus	Transports oxygen and nutrients to all the cells of the body (and removes carbon dioxide and waste products)
Digestive Overview of the Digestive System The digestive system, which extends from the mouth to the anus, is responsible for receiving food, breaking it down into nutrients (a process called digestion), absorbing the nutrients into... read more	Mouth Esophagus Stomach Small intestine Large intestine Rectum Anus Liver Gallbladder Pancreas (the part that produces enzymes) Appendix	Extracts nutrients from foods Excretes waste products from the body
Endocrine Endocrine Glands The endocrine system consists of a group of glands and organs that regulate and control various body functions by producing and secreting hormones. Hormones are chemical substances that affect... read more	Thyroid gland Parathyroid gland Adrenal glands Pituitary gland Pancreas (the part that produces insulin and other hormones) Stomach (the cells that produce gastrin) Pineal gland Ovaries Testes	Produces chemical messengers carried in the blood (hormones), which direct the activities of different organ systems
Urinary Overview of the Urinary Tract Normally, a person has two kidneys. The rest of the urinary tract consists of the following: Two ureters (the tubes connecting each kidney to the bladder) The bladder (an expandable muscular... read more	Kidneys Ureters Bladder Urethra	Filters waste products from the blood
Male reproductive Structure of the Male Reproductive System The male reproductive system includes the penis, scrotum, testes, epididymis, vas deferens, prostate, and seminal vesicles. The penis and the urethra are part of the urinary and reproductive... read more	Penis Prostate gland Seminal vesicles Vasa deferentia Testes	Enables reproduction
Female reproductive Overview of the Female Reproductive System The female reproductive system consists of the external genital organs and internal genital organs. Other parts of the body also affect the development and functioning of the reproductive system... read more	Vagina Cervix Uterus Fallopian tubes Ovaries	Enables reproduction