Human body
Oxygen makes up 65.02 percent of the human body by mass. Carbon accounts for 18.5 percent, while hydrogen comprises 9.5 percent. Nitrogen follows at 3.2 percent, and calcium represents 1.5 percent of total weight. These five elements form the bulk of every adult male and female structure. Trace elements like phosphorus, potassium, and sulfur make up less than one percent combined. Each trace element individually stays below 0.1 percent of total body mass. The distribution of these atoms determines how tissues function and interact daily.
An average mature human contains roughly 30 trillion cells within their physical frame. This number includes bacteria living inside the body, estimated at 38 trillion organisms. Skin hosts billions of commensal organisms alongside immune cells that protect against invaders. DNA damage occurs tens of thousands of times per day in each cell. Unrepaired errors can block genome replication or lead to mutations threatening viability. Most cells sit within an extracellular matrix made of proteins like collagen. Some red blood cells lose their nucleus as they mature into functional units.
The heart pumps blood through two circuits: pulmonary and systemic pathways. It sits in the thoracic cavity between lungs and slightly to the left side. Coronary artery disease causes 16 percent of all deaths worldwide due to plaque buildup. Digestion begins in the mouth where teeth chew food into smaller pieces. Peristalsis moves chyme through the gastrointestinal tract via muscle contraction. The kidneys filter about 150 quarts of blood daily but produce only one to two liters of urine. The nervous system divides into central and peripheral components controlling thought and movement.
Fertilization marks the start when sperm penetrates an egg released from a female ovary. An embryo lodges in the uterus before developing into a fetus until birth. Female puberty generally occurs between ages nine and thirteen with menstruation beginning. Male puberty sees further development of the penis and testicles producing sperm throughout life. At birth, females possess about 70,000 immature egg cells that degenerate over time. Growth continues through childhood, adolescence, adulthood, and finally old age. Genetic, hormonal, and environmental factors influence this lifelong process of maturation.
The Hippocratic Corpus described skeletal and muscular anatomy in Ancient Greece around 420 BCE. Galen of Pergamum compiled classical knowledge into texts used throughout the Middle Ages. Andreas Vesalius published De humani corporis fabrica in 1543 after pioneering dissection techniques. William Harvey described the circulatory system in the 17th century using careful observation. Matthias Schleiden and Theodor Schwann proposed cell theory in 1838 stating organisms consist of cells. Modern imaging includes magnetic resonance imaging and computed tomography for unprecedented detail.
Medical students gain practical experience by dissecting cadavers during their first year at school. Health professionals learn from illustrations, models, and demonstrations to understand structure and function. Anatomy, physiology, and biochemistry form basic medical sciences taught globally. Dissection allows direct examination of internal organs like the heart, lungs, and liver. Students study how blood vessels carry oxygen and waste products throughout the body. Clinical education bridges theoretical knowledge with real-world patient care scenarios today.
Common questions
What percentage of the human body is made up of oxygen by mass?
Oxygen makes up 65.02 percent of the human body by mass. Carbon accounts for 18.5 percent, while hydrogen comprises 9.5 percent. Nitrogen follows at 3.2 percent, and calcium represents 1.5 percent of total weight.
How many cells are in an average mature human body including bacteria?
An average mature human contains roughly 30 trillion cells within their physical frame. This number includes bacteria living inside the body, estimated at 38 trillion organisms. Skin hosts billions of commensal organisms alongside immune cells that protect against invaders.
Where does digestion begin and how does food move through the gastrointestinal tract?
Digestion begins in the mouth where teeth chew food into smaller pieces. Peristalsis moves chyme through the gastrointestinal tract via muscle contraction. The kidneys filter about 150 quarts of blood daily but produce only one to two liters of urine.
When did Andreas Vesalius publish De humani corporis fabrica?
Andreas Vesalius published De humani corporis fabrica in 1543 after pioneering dissection techniques. Galen of Pergamum compiled classical knowledge into texts used throughout the Middle Ages. Matthias Schleiden and Theodor Schwann proposed cell theory in 1838 stating organisms consist of cells.
What elements form the bulk of every adult male and female structure?
These five elements form the bulk of every adult male and female structure. Oxygen makes up 65.02 percent of the human body by mass. Carbon accounts for 18.5 percent, while hydrogen comprises 9.5 percent.