Respiratory System Anatomy and Physiology

Respiratory System Anatomy and Function

Oxygen (O₂) intake transforms into ATP. The respiratory pathway includes the nostrils, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli.

• Nares (Nostrils): The yellow region is associated with smell, while the reddish region warms the air.
• Choana: The communication hole between the nasal fossae and the nasopharynx.
• Bronchioles: These allow CO₂ output through the lungs.
• Alveoli: The primary site for gas exchange.

Upper and Lower Respiratory Tracts

The upper respiratory tract consists of the mouth, pharynx, and larynx. The pharynx is divided into the nasopharynx, oropharynx, and laryngopharynx.

• Larynx: A cartilaginous structure connecting the pharynx with the trachea; it is responsible for phonation.
• Epiglottis: Prevents food from passing into the pharynx when breathing stops during swallowing.
• Glottis: Contains the vocal cords.
• Trachea: Formed by C-shaped cartilaginous rings, it is the main airway to the lungs and divides into two bronchi.

Lung Structure and Gas Exchange

• Lung Hilum: The opening where blood vessels, bronchi, and bronchioles enter the lungs.
• Bronchi and Bronchioles: Internal ramifications within the lung that terminate in the alveoli.
• Alveoli: Air sacs located at the ends of the bronchi and bronchioles.
• Hematosis: The process where CO₂-carrying blood passes into the air, and venous blood becomes arterial blood.
• Lungs: Elastic organs that dilate and contract via the diaphragm. They are located in the thoracic cage and protected by the pleura, which can sometimes be invaded by bacteria, causing pleurisy.

Respiratory Control and Receptors

• Central Receptors: Located in the respiratory center and meningeal receptors; they respond to increased CO₂ and decreased pH.
• Chemoreceptors: Located in the aortic arch and carotid sinus; they detect a lack of O₂, CO₂ excess, and low pH.
• Distension Receptors: Located in the respiratory muscles.
• Thermoreceptors and Chemoreceptors: Located in the skin and musculature.
• Central Influences: Originating from the cerebral cortex and reticular formation, influenced by emotion, work, sleep, and wakefulness.
• Efferent Impulses: Sent to the motor neurons of the respiratory muscles.

Lung Capacity and Blood Chemistry

• Spirogram: A graphical representation of air levels in the lungs.
• Vital Capacity: The maximum air containment achieved in one inspiration.
• Heparin: A natural anticoagulant; its failure can lead to a thrombus.

Oxygen and Carbon Dioxide Transport

Oxygen (O₂) binds with Hemoglobin (Hb) to form Oxyhemoglobin (HbO₂). This is an unstable reaction that spreads easily; 3% dissolves in plasma, while 97% travels as HbO₂. The reaction moves in both directions: O₂ + Hb ↔ HbO₂.

Carbon Dioxide (CO₂) transport occurs in three ways:

• 60% travels as Bicarbonate Ion (HCO₃^-).
• 30% joins Hemoglobin to form carbaminohemoglobin.
• The remainder joins H₂O to form carbonic acid (H₂CO₃), which is rapidly degraded. This also moves in both directions: H₂O + CO₂ ↔ H₂CO₃ ↔ HCO₃^-.