Doctors measure heart rate—the number of contractions of the heart (or heartbeats) in one minute—by taking a person’s pulse or listening to the heart with a stethoscope. Your heart rate can be taken at any spot on the body at which an artery is close to…
The human brain is divided into three main parts: the cerebrum, the cerebellum, and the brainstem. The cerebrum is the largest part of the brain (about 85 percent of its total weight). It controls emotions, thought, memory, and speech. It is divided into a right…
The brain is the body’s command center. Everything we do—eating, talking, walking, thinking, remembering, sleeping—is controlled and processed by the brain. As the most complex organ in the human body, the brain tells us what’s going on outside our bodies (whether we…
As the young red blood cell grows and takes on an adult form in the marrow of the bone, it loses its nucleus, and it increases its production of hemoglobin. Hemoglobin is the red pigment, or color of blood, and contains iron, combined with…
More than half of your blood is a light yellow watery liquid called plasma. Plasma contains nutrients and waste products, along with chemicals and matter needed for clotting, or sealing a wound before too much blood escapes. The rest of blood is made of…
The human body contains approximately 6 quarts (5.6 liters) of blood. Blood acts as your body’s transportation system—in one day, your blood travels nearly 12,000 miles (19,312 kilometers). Pumped along by your heart, blood takes oxygen from the air you breathe and nutrients from…
Learning Objectives By the end of this section, you will be able to: We have discussed the events that lead to the development of a newborn. But what makes each newborn unique? The answer lies, of course, in the DNA…
Learning Objectives By the end of this section, you will be able to: Lactation is the process by which milk is synthesized and secreted from the mammary glands of the postpartum female breast in response to an infant sucking at the…
Learning Objectives By the end of this section, you will be able to: From a fetal perspective, the process of birth is a crisis. In the womb, the fetus was snuggled in a soft, warm, dark, and quiet world. The…
Learning Objectives By the end of this section, you will be able to: A full-term pregnancy lasts approximately 270 days (approximately 38.5 weeks) from conception to birth. Because it is easier to remember the first day of the last menstrual…