Every human story begins with a single fertilized cell containing a complete set of genetic instructions. This tiny blueprint guides a process called organogenesis
The only organ system not required for the immediate survival of an individual, its sole biological purpose is the survival of the species. It produces gametes (sperm and egg cells) and hormones necessary for the creation and development of offspring. Homeostasis: The Balance of Life The Human Body
The gastrointestinal tract transforms food into usable fuel. Digestion begins in the mouth, continues through the highly acidic environment of the stomach, and concludes in the small intestine, where nutrients are absorbed into the bloodstream. The large intestine reabsorbs water and prepares remaining indigestible material for elimination. The liver and pancreas support this process by producing digestive enzymes and processing absorbed nutrients. The Urinary System Every human story begins with a single fertilized
Your skin completely renews itself approximately every 28 days. Over a lifetime, you shed about 40 kilograms (88 pounds) of dead skin cells – most of the dust in your home! Homeostasis: The Balance of Life The gastrointestinal tract