Ch 22 Respiratory System Lecture

Alveoli are tiny, balloon-like air sacs, approximately 0.2 to 0.3 mm in diameter, located in the lungs that are crucial for gas exchange between the lungs and blood.
Each alveolus is surrounded by a dense network of capillaries, which are tiny blood vessels with walls only one cell thick, allowing for efficient diffusion of gases.
During gas exchange, oxygen diffuses from the air in the alveoli into the capillaries, where it binds to hemoglobin molecules in red blood cells. This process is essential for transporting oxygen throughout the body.
Conversely, carbon dioxide, produced as a waste product of cellular respiration in tissues, diffuses from the capillaries into the alveoli to be expelled from the body during exhalation.

Interdependent Functions

The respiratory system's function of gas exchange is closely linked to the cardiovascular system, which circulates blood throughout the body.
Oxygen is vital for cellular respiration, a biochemical process that generates adenosine triphosphate (ATP), the energy currency of cells.
The respiratory system ensures a constant supply of oxygen is available for tissues while removing carbon dioxide efficiently to maintain homeostasis.

Mechanism of Action

Oxygen enters the blood in the alveoli, binds to hemoglobin, and is transported via the bloodstream to various body tissues.
As tissues consume oxygen for energy, they produce carbon dioxide, which is transported back to the lungs through the venous circulation for exhalation, completing the cycle of gas exchange.

Nose: The primary entry point for air, filtering out large particles and providing humidification and temperature regulation.
Pharynx (Throat): A muscular tube that connects the nasal cavity to the larynx and esophagus. It plays a role in both breathing and digestion.
Larynx (Voice Box): Located below the pharynx, it houses the vocal cords and plays a crucial role in phonation and preventing food from entering the airway.
Trachea (Windpipe): A tube extending from the larynx to the bronchi, lined with ciliated epithelium that traps debris and particles.
Bronchi: The two main branches of the trachea that lead into each lung, dividing further into smaller bronchi and bronchioles, which eventually lead to the alveoli.
Lungs: The primary organs of respiration, consisting of a right lung with three lobes and a left lung with two lobes, facilitating the exchange of gases.

Components: Comprises the nose, pharynx, and larynx, primarily involved in the conduction of air and initial conditioning of air (warming and moistening).

Components: Includes the trachea, bronchi, bronchioles, and alveoli, focusing on gas exchange processes.

The nasal cavity effectively warms, moistens, and cleans incoming air before it reaches the lungs, enhancing respiratory efficiency.
It is lined with respiratory epithelium, specifically pseudostratified ciliated columnar epithelium, that traps particles and debris using mucus and cilia.

Nasopharynx: The upper part connected to the nasal cavity, including the openings for the Eustachian tubes which connect to the middle ear.
Oropharynx: Located behind the oral cavity; it serves as a passageway for food and air.
Laryngopharynx: The lower section that connects to the larynx, directing air to the respiratory tract and food to the digestive tract.

Situated atop the trachea, the larynx prevents food from entering the airway during swallowing and assists in the production of sound through the vibration of vocal cords.

The larynx is supported by three primary cartilage structures:
- Thyroid Cartilage: The largest, forming the Adam's apple.
- Cricoid Cartilage: A complete ring of cartilage that provides structure below the thyroid.
- Epiglottis: A flap of elastic cartilage that folds over the larynx during swallowing to prevent food from entering the airway.

The trachea is approximately 12 cm long and 2.5 cm wide, reinforced by C-shaped rings of hyaline cartilage that keep it open during breathing.
The trachealis muscle at the back allows for flexibility, accommodating the esophagus during the swallowing process.

The trachea bifurcates into the right and left main bronchi, each leading into their respective lung.
The right main bronchus is wider and more vertical than the left, making it more prone to the aspiration of foreign objects.