Respiratory System Overview

Respiratory System Overview

• The respiratory system facilitates gas exchange between the atmosphere and blood.
• This system is divided into two parts: upper and lower.

Upper Respiratory System

• Components: Nose, pharynx (throat), and associated structures.
• Function: Warming, moisturizing, and filtering inhaled air.

Lower Respiratory System

• Includes: conducting portion and respiratory portion.

• Conducting portion: Series of tubes and cavities that filter, warm, and moisten air whilst carrying it to the lungs

  • Nose
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Bronchioles
  • Terminal bronchioles

• Respiratory portion: Tissues within the lungs facilitating gas exchange.

  • Respiratory bronchioles
  • Alveolar ducts
  • Alveolar sacs
  • Alveoli

Bony Framework

• The respiratory system's bony framework includes:
  • Frontal bone
  • Nasal bones
  • Maxillae

Cartilaginous Framework

• The cartilaginous framework comprises numerous cartilages, including those of the nose, larynx, and trachea. (Specific cartilage types are detailed in the text).

The Nose: External and Internal Portions

• External portion: composed primarily of bones and cartilages.
• Internal portion: large air-filled cavities in the skull.
• Connected internally to the pharynx.
• Includes the paranasal sinuses.

Paired Laryngeal Cartilages

• Include arytenoid cartilages, cornuculate cartilages and cuneiform cartilages.
• Located superior to the cricoid cartilage, and aid in vocal cord movement
• Associated with the production of sound.

The Pleura

• The pleural membrane surrounds the lungs and covers the thoracic cavity.
• The visceral pleura adheres to the lungs, while the parietal pleura lines the chest cavity.
• The pleural cavity is the space between these two membranes, which contains fluid to reduce friction.

The Lungs

• Paired cone-shaped organs extending from the diaphragm to a point superior to the clavicles.
• Base (inferior portion): concave surface resting on the diaphragm.
• Apex (superior portion): Narrow superior region.
• Hilus (mediastinal surface): Slit where bronchi, blood vessels, lymphatics, and nerves enter and leave.

The Trachea

• Tubular passageway about 12 cm long and 2.5 cm in diameter.
• Located anterior to the esophagus.
• Divides into the right and left primary bronchi at the sternal angle.
• Lined with pseudostratified columnar epithelium with cilia and goblet cells.

The Bronchi

• The trachea divides into two primary bronchi.
• The right primary bronchus is more vertical, shorter, and wider than the left one.

Lung Lobes and Fissures

• Both lungs have an oblique fissure, while the right lung additionally has a horizontal fissure.
• These fissures divide the lungs into lobes, each supplied by a lobar bronchus (lobe-specific branch).

Exchange Mechanism (Alveolar-Capillary Membrane):

• Gas exchange between the lungs and blood occurs across the thin alveolar-capillary membrane, about 0.5 micrometers thick.
• This membrane is composed of squamous pulmonary epithelial cells, alveolar macrophages, and capillary endothelial cells.

Pulmonary Ventilation

• Breathing, also known as pulmonary ventilation, is the movement of air in and out of the lungs.
• Involves pressure gradient between the atmosphere and the lungs, enabling inspiration and expiration.

Lung Compliance and Surfactant

• Lung compliance reflects the ease with which the lungs expand.
• Surfactant is a substance produced by alveolar cells that reduces surface tension within the alveoli, which improves lung compliance.

Airway Resistance

• The resistance to airflow in the airways depends on factors including the pressure gradient and the diameter of the airways.

Regulation of Respiration

• The respiratory centre in the brain regulates breathing rate and depth, adjusting to changes in blood CO2, O2, and pH levels.
• Chemical and other (non-chemical) signals coordinate this process involving the inspiratory, expiratory, apneustic, and pneumotaxic areas.
• Peripheral chemoreceptors (carotid and aortic bodies) help detect arterial blood gas levels to modify respiration pace.

Fate of Oxygen in the Blood

• Oxygen transport in the blood depends on the amount of oxygen entering the lungs, efficiency of pulmonary gas exchange, blood flow to tissues and the blood's capacity to carry oxygen.

Fate of Carbon Dioxide in the Blood

• Carbon dioxide is transported in the blood in several forms: dissolved in plasma, in chemical combination with blood constituents, and as bicarbonate ions.