Introduction to the Respiratory System

• Aerobic Metabolism: Primary pathway for energy production.

  • Requires oxygen (O2) and produces carbon dioxide (CO2).

  • O2 is obtained from the air and diffuses across surfaces in the lungs.

  • O2 is transported from lungs to peripheral tissues, while CO2 is transported from tissues back to lungs.

Functions of the Respiratory System

• Gas Exchange: Provides surface area for gas exchange between air and circulating blood.

• Air Movement: Moves air to and from gas exchange surfaces of lungs.

• Protection: Protects respiratory surfaces from dehydration, temperature changes, and pathogens.

• Sound Production: Allows for phonation (production of sound).

• Olfactory Detection: Detects odors with olfactory receptors in the nasal cavity.

Organization of the Respiratory System

• Upper Respiratory System:

  • Includes the nose, nasal cavity, sinuses, and pharynx.

• Lower Respiratory System:

  • Consists of the larynx, trachea, bronchi, bronchioles, and alveoli.

Components of the Respiratory Tract

• Conducting Portion: From nasal cavity to larger bronchioles.

• Respiratory Portion: Composed of smaller respiratory bronchioles and alveoli, where gas exchange takes place.

• Alveoli: Air-filled pockets within lungs crucial for gas exchange.

Respiratory Mucosa

• Structure: Lines conducting portions of the respiratory system.

  • Composed of an epithelium and areolar tissue layer (lamina propria).

• Function: Protects against inhaled particles and pathogens through filtration mechanisms.

Lamina Propria

• Contains mucous glands in the upper respiratory system and smooth muscle cells in the conducting portion of lower respiratory tract.

Respiratory Epithelium Types

• Nasal Cavity & Superior Pharynx: Pseudostratified ciliated columnar epithelium with numerous mucous cells.

• Inferior Pharynx: Stratified squamous epithelium.

• Smaller Bronchioles: Cuboidal epithelium with scattered cilia.

Alveolar Epithelium

• Composed of delicate simple squamous epithelium and specialized scattered cells.

Respiratory Defense System

• Filtration: Nasal cavity filters large particles.

• Mucous Production: Mucous cells and glands produce mucus to trap debris.

• Ciliary Action: Cilia sweep mucus towards the pharynx.

• Alveolar Macrophages: Engulf small particles that reach the lungs.

Upper Respiratory System Components

• Nose: Main entry for air; nostrils lead into nasal vestibule.

• Nasal Hairs: Filter large particles from the air.

• Nasal Septum: Divides nasal cavity into left and right sides, includes olfactory region and mucous from sinuses.

• Air Meatuses: Produce turbulence to warm, humidify air and trap particles.

Pharynx Structure

• Shared area for digestive and respiratory systems.

• Composed of three parts:

  • Nasopharynx: Contains pharyngeal tonsil and openings to auditory tubes.

  • Oropharynx: Connects directly to the oral cavity.

  • Laryngopharynx: Between hyoid bone and entrances to larynx and esophagus.

Lower Respiratory System

• Air flows from the pharynx to the larynx through the glottis.

• Larynx Components: Composed of thyroid cartilage, cricoid cartilage, and epiglottis (covers glottis during swallowing).

Sound Production in Larynx

• Air vibrates through glottis, moving vocal folds to produce sound waves.

• Voluntary muscles alter tension of vocal folds to change sound pitch.

Trachea Structure

• Flexible tube extending from cricoid cartilage to mediastinum.

• Contains mucus-producing glands and C-shaped tracheal cartilages for support.

The Bronchial Tree

• Divides into right and left main bronchi, further branching into lobar and segmental bronchi; gradually lose cartilage and gain smooth muscle.

Bronchioles and Gas Exchange Structures

• Bronchioles: Branches containing smooth muscle without cartilage.

• Alveolar Ducts and Sacs: Lactate network of capillaries for gas exchange occurs in alveoli.

Surfactant Function

• Decreases surface tension within alveoli to prevent collapse.

Blood Supply to Lungs

• Oxygen-depleted blood reaches alveoli from pulmonary arteries, capillary networks surround alveoli for gas exchange.

External and Internal Respiration

• External Respiration: Gas exchange with the environment.

• Internal Respiration: Cellular uptake of O2 and release of CO2.

Gas Exchange Mechanisms

• Gas Transport: O2 is bound to hemoglobin (Hb), CO2 is transported in different forms including as bicarbonate ions and bound to Hb.

Control of Respiration

• Neural Mechanisms: Regulate the depth and rate of respiration via brain centers in response to sensory information.

• Local factors help adjust blood flow and ventilation in lungs.

Reflex Controls

• Involves responses to irritants and changes in respiratory demand through various receptors, resulting in protective measures like coughing or sneezing.