Respiratory System (Unit 3) - Handwritten Notes
Download handwritten notes for Human Anatomy and Physiology 2 (Semester 2), covering Unit 3: The Respiratory System. These notes detail the anatomy of the respiratory system, with a particular focus on the lungs. They explain the mechanism and regulation of respiration, lung volumes and capacities, the transport of respiratory gases (oxygen and carbon dioxide), and methods of artificial respiration and resuscitation. Includes information on lung diagrams, total lung capacity, the nose, and the pathway of the respiratory system. Provided in PDF format.
Keywords: Respiratory System, Lungs, Respiration, Lung Volumes, Lung Capacities, Gas Transport, Artificial Respiration, Resuscitation, Anatomy, Physiology, Handwritten Notes, PDF, Download, Semester 2, B.Pharm, Nose, Respiratory Pathway, Total Lung Capacity.
Respiratory System (Unit 3) - Detailed Explanation
Anatomy of the Respiratory System
The respiratory system is responsible for the exchange of oxygen and carbon dioxide between the body and the environment. It can be divided into the upper respiratory tract (nose, nasal cavity, pharynx) and the lower respiratory tract (larynx, trachea, bronchi, lungs).
Nose and Nasal Cavity
The nose is the external opening of the respiratory system. The nasal cavity is lined with a mucous membrane that warms, humidifies, and filters incoming air. The nasal conchae (turbinates) increase the surface area and create turbulence, improving air filtration.
Pathway of the Respiratory System
Air enters through the nose or mouth, passes through the pharynx (throat), then the larynx (voice box). The trachea (windpipe) carries air to the bronchi, which branch into smaller and smaller tubes (bronchioles) within the lungs. The bronchioles terminate in tiny air sacs called alveoli, where gas exchange occurs.
Lungs
The lungs are the primary organs of respiration. They are paired, cone-shaped organs located in the thoracic cavity, surrounded by the pleural membranes (visceral and parietal pleura). The right lung has three lobes, while the left lung has two (to accommodate the heart). The alveoli are surrounded by a network of capillaries, allowing for efficient diffusion of oxygen into the blood and carbon dioxide out of the blood.
Mechanism of Respiration
Respiration involves two main phases: inspiration (inhalation) and expiration (exhalation). These are driven by changes in pressure within the thoracic cavity, controlled by the diaphragm (a dome-shaped muscle) and the intercostal muscles (between the ribs).
- Inspiration: The diaphragm contracts and flattens, and the external intercostal muscles contract, lifting the rib cage. This increases the volume of the thoracic cavity, decreasing the pressure inside (Boyle's Law: pressure and volume are inversely related). Air flows from the higher pressure atmosphere into the lower pressure lungs.
- Expiration: The diaphragm relaxes and returns to its dome shape, and the external intercostal muscles relax. The elastic recoil of the lungs and chest wall decreases the volume of the thoracic cavity, increasing the pressure. Air flows from the higher pressure lungs to the lower pressure atmosphere.
Regulation of Respiration
Breathing is primarily controlled by the respiratory centers in the brainstem (medulla oblongata and pons). These centers receive input from chemoreceptors, which detect changes in blood levels of oxygen, carbon dioxide, and pH.
- Central chemoreceptors: Located in the medulla, these are most sensitive to changes in the pH of cerebrospinal fluid, which is directly affected by blood CO2 levels. Increased CO2 leads to increased acidity, stimulating increased ventilation.
- Peripheral chemoreceptors: Located in the carotid bodies and aortic bodies, these are sensitive to changes in blood oxygen levels (primarily), as well as CO2 and pH. Low oxygen levels stimulate increased ventilation.
Lung Volumes and Capacities
Lung volumes and capacities are measurements of the amount of air that can be moved in and out of the lungs.
- Tidal Volume (TV): The amount of air inhaled or exhaled during normal breathing (around 500 mL).
- Inspiratory Reserve Volume (IRV): The additional amount of air that can be inhaled after a normal inspiration.
- Expiratory Reserve Volume (ERV): The additional amount of air that can be exhaled after a normal expiration.
- Residual Volume (RV): The amount of air remaining in the lungs after a maximal exhalation.
- Vital Capacity (VC): The maximum amount of air that can be exhaled after a maximal inhalation (VC = TV + IRV + ERV). Represents maximum exchangeable air.
- Total Lung Capacity (TLC): The total amount of air the lungs can hold (TLC = VC + RV).
Transport of Respiratory Gases
Oxygen Transport: Most oxygen (about 98.5%) is transported bound to hemoglobin in red blood cells. A small amount is dissolved in the plasma. The binding of oxygen to hemoglobin is affected by factors like partial pressure of oxygen (PO2), pH, temperature, and the presence of 2,3-bisphosphoglycerate (2,3-BPG).
Carbon Dioxide Transport: Carbon dioxide is transported in three ways:
- Dissolved in plasma (about 7%).
- Bound to hemoglobin (about 23%).
- As bicarbonate ions (HCO3-) in plasma (about 70%). This is the primary method. CO2 reacts with water in red blood cells (catalyzed by carbonic anhydrase) to form carbonic acid (H2CO3), which dissociates into H+ and HCO3-.
Artificial Respiration and Resuscitation Methods
These methods are used when a person's breathing has stopped or is inadequate.
- Mouth-to-mouth resuscitation: Providing breaths to the victim by blowing air into their mouth.
- Cardiopulmonary resuscitation (CPR): Combines chest compressions and rescue breaths to maintain circulation and oxygenation.
- Mechanical ventilation: Using a machine (ventilator) to assist or control breathing.
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