BIOL2302 Chapter 6

Chapter 6: Respiratory System

Overview

The respiratory system is essential for supplying oxygen (O2) to body cells and removing carbon dioxide (CO2), a byproduct of metabolism. It works with the cardiovascular system to transport gases. This chapter covers the anatomy of the respiratory system, mechanics of breathing (ventilation), gas transport, and control of breathing. Cellular respiration, which occurs in cells, uses oxygen to produce ATP.

Anatomy of Respiratory System

The respiratory system includes the nose, nasal cavity, pharynx, larynx, trachea, bronchi, and alveoli. The upper respiratory tract consists of the nose, nasal cavity, and part of the pharynx, while the lower respiratory tract includes the remaining pharynx, larynx, trachea, bronchi, and alveoli. The conducting zone (nose to bronchioles) conducts air, while the respiratory zone (respiratory bronchioles and alveoli) is where gas exchange occurs.

The Nose and Nasal Cavity

The nose leads to the nasal cavity, which warms, humidifies, and filters air. It is lined with mucous membranes that trap pathogens and particles.

The Paranasal Sinuses

These are cavities in skull bones that open into the nasal cavity, helping to keep the nasal epithelium moist and contributing to voice resonance.

The Pharynx

The pharynx connects the nasal cavity to the larynx and the oral cavity to the esophagus. It is divided into the nasopharynx, oropharynx, and laryngopharynx.

The Larynx

The larynx, or voice box, contains vocal cords and is involved in sound production. It is supported by cartilage and is located between the pharynx and trachea.

The Trachea

The trachea is a rigid tube that conducts air to the bronchi and is supported by cartilage rings. It divides into primary bronchi.

The Bronchial Tree and Alveoli

The bronchial tree branches into smaller bronchi and bronchioles, leading to alveoli, where gas exchange occurs. The alveolar wall consists of type I and type II pneumocytes, with type II cells secreting surfactant to reduce surface tension.

The Lungs

The lungs are located in the thoracic cavity, separated by the diaphragm, which is crucial for breathing. Each lung is encased in pleura, with a pleural cavity containing lubricating fluid.

Respiratory System Physiology

Ventilation involves moving air in and out of the lungs through inspiration and expiration. Inspiration is an active process, while expiration is typically passive. The mechanics of breathing involve changes in thoracic cavity volume and pressures.

Respiratory Volumes and Capacities

Tidal volume is the amount of air exchanged during normal breathing. Other volumes include inspiratory reserve volume, expiratory reserve volume, and residual volume. These can be measured to assess lung function.

Transport of Gases

Oxygen is primarily transported by hemoglobin in red blood cells, while carbon dioxide is transported in three forms: dissolved in plasma, as carbamino compounds, and as bicarbonate ions. Gas transport is influenced by physical laws governing partial pressures and solubility.

Control of Breathing

Breathing rate is regulated by centers in the brain, responding to levels of oxygen and carbon dioxide in the blood. Carbon dioxide levels are the primary driver for changes in breathing rate.

Cellular Respiration

Oxygen is used in cellular respiration to produce ATP, with carbon dioxide as a waste product.

Pathological Conditions

Common respiratory conditions include asthma, pneumonia, and chronic obstructive pulmonary disease (COPD). Diagnostic procedures and treatments are also discussed.