Human Physiology: Respiratory and Renal System Functions

Pulmonary Ventilation and Gas Exchange

Pulmonary ventilation: This is the mechanism through which the air in the lungs and the respiratory tract is renewed. It allows air to flow in and out of the lungs. Ventilation is carried out through two respiratory movements: inhalation and exhalation. The diaphragm and the intercostal muscles mainly participate in these movements. By contracting and relaxing, these muscles produce changes in the volume of the lungs.

Inhalation

This is the movement that allows air to enter the lungs.

1. The diaphragm contracts, increasing the vertical diameter of the thoracic cavity.
2. The external intercostal muscles contract. The diameters of the thoracic cavity increase.
3. The lungs, which are elastic, expand.

Exhalation

This is the movement that allows air to leave the lungs.

1. The diaphragm relaxes and returns to its original position, decreasing the vertical diameter of the thoracic cavity.
2. The external intercostal muscles relax, and the diameters of the thoracic cavity decrease.
3. The lungs contract.

Gas Exchange

In this exchange, oxygen from the air in the alveoli passes into the pulmonary blood capillaries. From there, the carbon dioxide from the blood in the capillaries passes into the alveoli. Gases pass through the walls of the alveoli and blood vessels in one direction or another by simple diffusion; this is due to the difference in the concentration of gases between one side and another.

1. The pulmonary arteries carry the oxygen-poor blood to the lungs.
2. The concentration of oxygen is greater in the air of the alveoli than in the blood of the capillaries, so this gas diffuses into the blood (inhaled air).
3. The concentration of carbon dioxide in the blood of the capillaries is greater than in the air of the alveoli. The oxygen-rich blood flows out.

The Renal System and Nephrons

Nephrons: Each kidney contains about a million microscopic nephrons; these are the functional units that produce urine.

• Renal artery (arteria roja): Blood containing waste enters the kidneys through the right and left renal arteries.
• Glomerulus: Blood capillaries that are arranged in the shape of a ball. The blood carrying waste that needs to be eliminated circulates through them.
• Renal tubule: A long tubule surrounded by peritubular capillaries. The urine that is being formed flows through it.
• Glomerular capsule: A cup-shaped dilation located at the beginning of the renal tubule.
• Collecting tubule: A tube shared by various nephrons that receives the newly formed urine from the nephrons and carries it to the renal pelvis.

The filtered, waste-free blood leaves the kidneys through the right and left renal veins.