I sketched out a very simple and brief outline on the Living Body and how it works here:
https://c.blogspot.com/2025/04/the-living-body-how-it-works.html
I thought I should write just a little bit more using just two examples - the heart and the lungs among other organs and body systems so that readers can have a glimpse how beautifully the body is designed
Lung Physiology: Structure, Function, and Diseases
The lungs are the central organs of the respiratory system, responsible for gas exchange between the environment and the bloodstream. Oxygen enters the alveoli and diffuses into the capillary network, where it binds to hemoglobin and is transported through the arterial system to perfuse tissues. The respiratory system consists of the nose, oropharynx, larynx, trachea, bronchi, bronchioles, and lungs. The lungs are divided into lobes, further subdividing into over 300 million alveoli—the primary site of gas exchange.
Breathing is primarily controlled by the diaphragm, which is innervated by the phrenic nerve (C3, C4, C5). During physical exertion or respiratory distress, external intercostal muscles assist in inspiration.
Lung Volumes and Capacities
Lung function is assessed using various volumes and capacities:
1. Inspiratory Reserve Volume (IRV): Air inhaled beyond a normal breath.
2. Tidal Volume (TV): Air exchanged in a normal breath.
3. Expiratory Reserve Volume (ERV): Air exhaled beyond a normal breath.
4. Residual Volume (RV): Air remaining after maximal exhalation (not measurable by spirometry).
5. Inspiratory Capacity (IC): Maximum air inhaled after a normal exhalation.
6. Functional Residual Capacity (FRC): Air left in lungs after a normal breath.
7. Vital Capacity (VC): Maximum air exhaled after full inhalation.
8. Total Lung Capacity (TLC): Total air in lungs after maximal inhalation.
9. Forced Expiratory Volume (FEV1): Air exhaled in the first second of a forced breath.
Lung Diseases: Obstructive vs. Restrictive
Lung diseases are classified into obstructive and restrictive disorders
Obstructive Lung Diseases
These diseases impair expiration, leading to air trapping and increased FRC. Common examples include:
1. Asthma: Chronic bronchial inflammation causing reversible airway obstruction. Symptoms include wheezing, chronic cough, tachypnea, and dyspnea.
2. Chronic Obstructive Pulmonary Disease (COPD): A progressive condition involving both chronic bronchitis (airway inflammation, excess mucus) and emphysema (loss of alveolar elasticity, enlarged air spaces). Smoking is the primary cause, leading to small airway disease and lung tissue destruction.
In obstructive diseases, lung function tests show decreased FVC, decreased FEV1, and a significantly reduced FEV1/FVC ratio.
Restrictive Lung Diseases
These diseases limit lung expansion, reducing lung volumes (FVC and FEV1) but maintaining or increasing the FEV1/FVC ratio. Examples include:
1. Idiopathic Pulmonary Fibrosis
2. Pneumoconiosis (lung damage from inhaled dust/particles)
3. Sarcoidosis (inflammatory lung disease)
Oxygen Transport and Hemoglobin
At the cellular level, oxygen is carried in two main forms:
1. Bound to hemoglobin (Hb) – the major oxygen carrier
2. Dissolved in plasma
The oxygen content of blood is calculated as:
Where:
1. CaO2 = Oxygen content in blood
2. [Hb] = Hemoglobin concentration
3. SaO2 = Oxygen saturationReplyForward |
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