Human Respiration and the Circulatory System
Respiration
Respiration is the process by which air containing oxygen enters our body, and air rich in carbon dioxide is expelled. A living being can survive for several hours without eating, sleeping, or drinking water, but cannot stop breathing for more than three minutes. This fact highlights the importance of breathing for our lives.
Composition of Air
- Nitrogen (N2): 78.084%
- Oxygen (O2): 20.946%
- Argon (Ar): 0.9340%
- Carbon dioxide (CO2): 0.039%
- Neon (Ne): 0.001818%
- Helium (He): 0.000524%
- Inter alia
Respiratory Mechanics
Respiratory mechanics refers to the cyclic process that maintains the amount of air in the lungs. It comprises two phases: inspiration, which is inhaling air, and expiration, which is expelling air.
Breathing Frequency
The frequency of breathing refers to the number of times we complete a full breathing cycle per minute (inspiration and expiration). Normal breathing frequencies vary according to age, among other factors. Typical values for normal breathing are:
- Babies from zero to six months: 30 to 50 breaths per minute
- Babies from six months to a year: 20 to 40 breaths per minute
- Babies from one to two years: 20 to 30 breaths per minute
- Children from two to six years: 15 to 25 breaths per minute
- Children from six to ten years: 15 to 20 breaths per minute
- Children over ten years: 13 to 15 breaths per minute
The relationship between frequency and respiratory mechanics is that the frequency represents the number of times the process of mechanical ventilation occurs.
Air enters through the nose or mouth and travels through the pharynx and larynx, where it is warmed. It then reaches the trachea, bronchi, and their branches, finally reaching the bronchioles. Gas exchange occurs in the alveoli due to the pressure difference between the alveoli and the outside. The air then travels through the artery, arterioles, and capillaries, where oxygen is exchanged.
The Voice
The voice is a combination of sounds produced by the vibration of the vocal cords. The articulation of sounds involves the lips, tongue, jaws, teeth, and palate.
Coughing
Coughing is essentially the rapid expulsion of air from the lungs, moving quickly through the trachea and throat. This action helps to clear any irritants found in the lining of these areas, potentially expelling them (such as phlegm).
Sneezing
Sneezing is similar to coughing but focuses on clearing irritants from the nasal mucosa. Instead of expelling air solely through the mouth, a portion is diverted into the nasal cavities to expel irritants like mucus or pollen.
Hemoglobin
Hemoglobin’s function is to transport respiratory gases. When it encounters oxygen, it forms a chemical compound called oxyhemoglobin, which carries oxygen to the tissues. In the tissues, the blood picks up carbon dioxide, which partially combines with hemoglobin to form carboxyhemoglobin. When this compound reaches the lungs, it splits, releasing carbon dioxide for expulsion, and oxyhemoglobin is reformed. This cycle repeats continuously.
The Circulatory System
The circulatory system is responsible for distributing oxygen and nutrients to all parts of the body. It is closely related to the respiratory system. Through pulmonary circulation, deoxygenated blood is re-oxygenated in the alveoli during gas exchange (hematosis), where respiratory gases move in and out by simple diffusion (O2 in, CO2 out).
The circulatory system is also connected to the digestive system at the level of the intestinal villi in the second portion of the small intestine (jejunum-ileum). Nutrients are absorbed by these villi and pass into the capillaries due to blood pressure, distributing them to all body cells.
The circulatory system consists of the heart, veins, vena cava, pulmonary vein, aorta, arteries, arterioles, and pulmonary artery.
The circulatory system is considered closed because the exchange between blood and body tissues occurs through the vessel walls.
The circulatory system is double because it has two distinct circuits: one circulating blood between the heart and lungs, and the other circulating blood from the heart to the rest of the body.
Composition of Blood
- Red Blood Cells: Carry most of the oxygen in the blood, bound to hemoglobin.
- White Blood Cells: Involved in defending the body in various ways, depending on the type of white blood cell.
- Platelets: Participate in the blood clotting process, promoting wound healing.
- Plasma: Carries substances that cells need or discard, except for most of the oxygen and some carbon dioxide.
Heart Rate
Heart rate refers to the existence of beats that follow a precise order, all within the same frequency range and sounding like a drum. Arrhythmia occurs when there is an irregular heartbeat, disrupting the rhythmic motion of the heart, or a totally chaotic rhythm, as in atrial fibrillation.
The Lymphatic System
The lymphatic system plays a protective role throughout the body, helping to remove waste products, excess fluids, and substances that can accumulate in tissues and potentially harm them.