Anatomy and Physiology Study Guide for the HESI Exam

Urinary

The urinary system, or renal system, removes waste from the body and regulates the blood. It is composed of the kidneys, ureters, bladder, and urethra. The kidneys filter the blood, converting waste into urine. The ureters are smooth, muscular tubes, which transport urine from the kidneys to the bladder. Urine is stored in the bladder before being passed through the urethra and expelled.

Within the kidneys, blood is filtered through renal corpuscles into a structure called a nephron, inside which urine is produced. The urine then passes through a system of vessels known as the collecting duct system, forming minor and major calyces. These vessels lead into the pelvis of the kidney, which drains into the ureter.

As well as creating urine, the kidneys also maintain the balance of ions, pH, fluids, and electrolytes, and blood pressure. This is achieved through the production of hormones and enzymes, such as calcitriol, erythropoietin, and renin.

Circulatory

The circulatory, or cardiovascular, system is composed of the heart, blood vessels, and blood. Its function is to transport blood cells and nutrients around the body. Blood contains plasma, red blood cells, white blood cells and platelets. Plasma is the fluid, which carries hormones, carbon dioxide and waste. Red blood cells carry oxygen and white blood cells produce antibodies. Platelets, or thrombocytes, form clots to stop bleeding.

There are two circuits through which blood travels: pulmonary and systemic. The pulmonary circuit carries blood to the lungs where carbon dioxide is removed and oxygen binds to the hemoglobin in the red blood cells. The oxygenated blood is then taken back to the heart, where it can be circulated by the systemic circuit to deliver oxygenated blood to the rest of the body, as well as transporting nutrients and waste.

The human heart is composed of four chambers; the left and right atriums, and left and right ventricles. The atria receive blood and the ventricles pump it out. The heart also contains valves to stop the blood from flowing backward.

Deoxygenated blood is received by the right atrium via large veins called the venae cavae. It is then transferred to the right ventricle through the tricuspid valve and subsequently exits the heart through the semilunar valve and is transferred to the pulmonary artery, where it is pumped toward the lungs for oxygenation.

Oxygenated blood is received by the left atrium and transferred to the left ventricle through the mitral valve. It is then pumped through the aorta and to the rest of the body, via another semilunar valve.

The arteries transport blood away from the heart under high pressure and have strong muscular walls. The veins carry blood to the heart under low pressure and are thinner, but contain valves to prevent backflow. Capillaries are the smallest blood vessels. They are incredibly thin, enabling efficient gas exchange between blood and tissues in the muscles and lungs, where oxygen is transferred from blood to tissue and carbon dioxide from tissue to blood.

The pulse rate is the number of heartbeats per minute and a normal pulse rate for a healthy adult should fall between 60 and 100 beats per minute.

There are two types of blood pressure―systolic and diastolic. Systolic pressure is the pressure inside the arteries when the heart contracts and should be less than 120 mm Hg. Diastolic pressure is the pressure in the arteries when the heart relaxes and a normal value is under 80 mm Hg.