5.1

Introduction

• The respiratory system's purpose is to maximize gas exchange across body tissues.
• It involves two main processes and many structures spanning other body systems.
• The goal is to deliver oxygen to tissues and remove carbon dioxide.
• Understanding organ order, function, and gas pathways is crucial.

Structures

1. Nasal Cavity

• Warms, filters, and moistens inhaled air.
• Lined with mucous membranes producing mucus.
• Mucus helps humidify air and trap debris.
• Cilia in the nose push debris out of the nasal cavity.

2. Pharynx

• Shared space behind the nasal cavity and mouth, acting as a passage for air and food.

3. Glottis

• Located at the end of the pharynx and start of the windpipe.
• Covered by the epiglottis during swallowing.

4. Larynx

• Space below the glottis, leading to the windpipe.
• Also known as the voice box, containing vocal cords.
• Vocal cords are bands of muscle opening/closing to produce vocal sounds.
• Pitch depends on vocal cord tension and movements of other structures like tongue and lips.
• Protected by the cartilaginous Adam's apple.

5. Trachea

• Also known as the windpipe.
• Composed of cartilage rings to prevent collapse.
• Lined with cilia that move debris-laden mucus upwards.

6. Bronchi

• Branches of the trachea, each leading to a lung.
• Contain cartilage, maintaining rigidity.

7. Bronchioles

• Smaller branches of the bronchi.
• Numerous and lack cartilage.

8. Alveoli

• Small air sacs at the ends of the bronchioles resembling balloons.
• Important for gas exchange.
• Made of simple squamous epithelium (one cell layer thick) to allow for rapid diffusion.
• Numerous, providing a large surface area for gas exchange.

What Happens to Air on its Way to the Alveoli

• Air is cleaned of debris by nose hairs and mucus in the nasal cavity.
• Mucus and cilia in the trachea and bronchi help trap debris.
• Air is warmed and humidified by contact with moist tissues to reach body temperature (37°C).
• Air reaches the alveoli with no temperature or humidity difference.

Specializations of the Alveoli

• Extremely numerous, approximately 300 million per lung, maximizing surface area.
• One cell layer thick to facilitate rapid gas exchange.
• Lined with lipoprotein to prevent collapse and sticking.
• Stretch receptors signal when alveoli are full of air for the body to exhale.
• High vascularization (surrounded by capillary networks), facilitating gas exchange between air and blood.

Pleural Membranes

• Double membranes surrounding the lungs.
• One membrane lines the lungs and the other the thoracic cavity.
• Fluid between the membranes create a vacuum to prevent lung collapse.
• Allows lungs to slide over the inner chest wall reducing friction.

Thoracic Cavity (Chest Cavity)

• Encompasses area from larynx to diaphragm just below the lungs.
• The diaphram is a horizontal band of muscle separating the thoracic cavity from the abdominal cavity.
• Rib muscles surrounding rib cage play a vital role in ventilation.