Body structure

• The human body is a biological machine made of body systems; groups of organs that work together to produce and sustain life
• Key facts about the human body systems


  • Musculoskeletal system
  • Cardiovascular system
  • Respiratory system
  • Nervous system
  • Digestive system
  • Urinary system
  • Endocrine system
  • Lymphatic system
  • Reproductive system
  • Integumentary system
• System of organs


  A group of organs that work together to perform one or more functions in the body
• Musculoskeletal system


  • Mechanical support, posture and locomotion
• Cardiovascular system


  • Transportation of oxygen, nutrients and hormones throughout the body and elimination of cellular metabolic waste
• Respiratory system


  • Exchange of oxygen and carbon-dioxide between the body and air, acid-base balance regulation, phonation
• Nervous system


  • Initiation and regulation of vital body functions, sensation and body movements
• Digestive system


  • Mechanical and chemical degradation of food with purpose of absorbing into the body and using as energy
• Urinary system


  • Filtration of blood and eliminating unnecessary compounds and waste by producing and excreting urine
• Endocrine system


  • Production of hormones in order to regulate a wide variety of bodily functions (e.g. menstrual cycle, sugar levels, etc)
• Lymphatic system


  • Draining of excess tissue fluid, immune defense of the body
• Reproductive system


  • Production of reproductive cells and contribution towards the reproduction process
• Integumentary system


  • Physical protection of the body surface, sensory reception, vitamin synthesis
• There are 206 bones in an adult human body
• Joint


  The place at which two bones are fitted together
• Functions of the skeletal system


  • Mechanical support, movement, protection, blood cell production, calcium storage and endocrine regulation
• The anatomy of bones, joints and ligaments is studied topographically, as the bones of the head and neck, thorax, abdomen, upper and lower limbs
• Smooth muscle is found within walls of blood vessels and hollow organs such as the stomach or intestines
• Cardiac muscle cells form the heart muscle, also called the false
• Skeletal muscles attach to the bones of the body
• Skeletal and cardiac muscle fibers are arranged in a repetitive fashion giving a striped appearance, hence are called striated muscle
• Smooth muscle does not contain repetitive sarcomeres, thus is non-striated muscle
• The heart is composed of four chambers; two atria and two ventricles
• Blood enters the heart through the upper chambers of the left and right atria and exits via the left and right ventricles
• Heart valves prevent the backflow of blood
• The right side of the heart pumps deoxygenated blood into the pulmonary circulation of the lungs, where the blood is reoxygenated again
• The left side of the heart simultaneously pumps oxygenated blood into the systemic circulation, distributing it to the peripheral tissues
• The regular pumping, or heartbeat, is controlled by the conduction system of the heart
• Blood leaves the heart via arteries, these progressively reduce in size to continue as smaller arterial vessels called arterioles
• Arterioles end in a web of even smaller vessels called capillaries
• The exchange of gases and nutrients occurs through the capillary walls
• Small veins, called venules, leave from capillaries and gradually increase their lumen on the way to the heart to end as veins
• Arteries convey blood from the heart to the periphery, whereas the veins convey blood from the periphery to the heart
• There are three separate circuits to the circulatory system: the pulmonary circulation, the coronary circulation, and the systemic circulation
• Major arteries within the systemic circulatory system are the aorta and its branches, while the main representatives of the veins are the superior vena cava and inferior vena cava
• The respiratory system consists of a series of organs; the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and lungs (alveoli)
• The nasal cavity and pharynx are together called the upper respiratory system, while the remainder of the organs comprise the lower respiratory system
• Respiratory system organs, with the exception of the alveoli, function to conduct air into the lungs aided by the muscles of respiration (mainly the diaphragm and intercostal muscles)
• Once air is in the lungs it enters alveoli (the site of gas exchange) and interacts with blood transported by the pulmonary circulation. Here carbon dioxide is removed from, and oxygen returned to, the blood
• The major respiratory system function is to bring oxygen into the body and expel carbon dioxide