Explain the process of breathing

1 Breathing: The technical term is pulmonary ventilation, or the movement of air into
and out of the lungs. (Breathing is also called inspiration and expiration.)

2 Exchanging gases: This takes place between the alveolar cells in the lungs, the blood,
and the body’s cells in two ways:

   • Pulmonary, or external, respiration: The exchange in the lungs when blood
gains oxygen and loses carbon dioxide, transforming it from venous blood into
arterial blood

   • Systemic, or internal, respiration: The exchange within systemic capillaries
when the blood releases some of its oxygen and collects carbon dioxide from the
tissues

3 Adult breathing rate: About 12 to 20 times per minute.

4 Anoxia: Oxygen deficiency in which the cells either don’t have or can’t utilize
sufficient oxygen to perform normal functions.

5 Asphyxia: Lack of oxygen with an increase in carbon dioxide in the blood and
tissues; accompanied by a feeling of suffocation leading to coma.

6 Expiration or exhalation: The diaphragm returns to its domed shape as the
muscle fibers relax, via elastic recoil of the lungs and tissues lining the thoracic
cavity, the external intercostal muscles relax, and the internal intercostal muscles
contract. This movement pulls the ribs back into place, decreasing the volume of
the thoracic cavity and increasing pressure, forcing air out of the lungs.

7 Hypoxia: Low oxygen content in the inspired air.

8 Inspiration or inhalation: When the muscles of the diaphragm contract, its
dome shape flattens; simultaneously, the contraction of the external intercostal
muscles pulls the ribs upward and increases the volume of the thoracic cavity,
decreasing the intra-alveolar pressure. The pressure difference between the
atmosphere and the lungs diffuses air into the respiratory tract.

9 Lung capacity: The vital capacity plus the residual air.

10 Mediastinum: The region between the lungs extending from the sternum ventrally
(at the front) to the thoracic vertebrae dorsally (at the back), and superiorly
(top) from the entrance of the thoracic cavity to the diaphragm inferiorly
(at the bottom).

 11 Minimal air: The volume of air in the lungs when they’re completely collapsed
(150 cubic centimeters in an adult).

12 Phrenic nerve: The nerve that innervates (stimulates) the diaphragm.

13 Residual air: The volume of air remaining in the lungs after the most forceful
expiration (1,200 cubic centimeters in an adult).

14 Respiratory centers: Nerve centers for regulating breathing located in the
medulla oblongata, or brain stem. The centers are influenced by the amount of
carbon dioxide in the blood.

15 Tidal air: The volume of air inspired and expired in the resting state (500 cubic
centimeters in an adult).

16 Vital capacity: The volume of air moved by the most forceful expiration after a
maximum inspiration. It represents the total moveable air in the lungs (4,600
cubic centimeters in an adult).

Here’s what happens as you breathe in and out . Red blood cells use a
pigment called hemoglobin to carry oxygen and carbon dioxide throughout the body
through the circulatory system  Hemoglobin bonds loosely with oxygen, or O2, to
carry it throughout the body; the bonded hemoglobin is called oxyhemoglobin.

After hemoglobin releases its oxygen molecules, it picks up carbon dioxide, or CO2,
to deliver to the lungs for exhalation. The freshly bonded hemoglobin becomes
carbohemoglobin