NR 324 Week 2 Upper Respiratory System

Grace J.
August 6, 2025August 6, 2025
CU BSN, NR-324

Student Name

Chamberlain University

NR-324 Adult Health I

Prof. Name

Date

Function of the Respiratory System

What is the primary role of the respiratory system?

The respiratory system’s essential function is gas exchange. It facilitates the movement of oxygen (O₂) into the bloodstream and carbon dioxide (CO₂) out into the atmosphere.

How is the respiratory tract anatomically divided?

It is split into two major subdivisions:

Upper respiratory tract, which includes the nose (responsible for warming, humidifying, and filtering inhaled air), mouth, pharynx, epiglottis, larynx, and trachea (ending at the carina).
Lower respiratory tract, beginning below the carina, comprising the bronchi, bronchioles, alveolar ducts, alveoli (the principal site of gas exchange with pulmonary capillaries), and the pores of Kohn (small openings connecting adjacent alveoli that allow air and bacteria to circulate).

What are key structural and functional details of the lungs?

The right lung has three lobes; the left has two.
Surfactant, a lipoprotein, reduces surface tension in alveoli, preventing collapse (atelectasis).
Pulmonary circulation delivers deoxygenated blood from the right ventricle to alveoli and returns oxygenated blood to the left atrium.
Bronchial circulation supplies oxygenated blood to lung tissues and bronchi; the azygos vein returns deoxygenated blood to the superior vena cava.

What about the chest wall and respiratory muscles?

The thoracic cage (ribs and sternum) protects the heart and lungs. The mediastinum holds vital structures like the heart and aorta.
The pleura consists of the parietal (chest wall) and visceral (lung) layers. The intrapleural space contains 20–25 mL of lubricating fluid, facilitating smooth lung movement.
The diaphragm is the principal respiratory muscle—during inhalation it contracts downward, increasing thoracic volume. Intercostal and scalene muscles assist. Phrenic nerves (from cervical vertebrae C3–C5) provide neural control.

Physiology of Respiration

How does the body oxygenate tissues?

Oxygenation: O₂ dissolves in plasma (PaO₂ normal range: 80–100 mm Hg) and binds to hemoglobin (oxygen saturation, SaO₂ > 95%).
Diffusion: Gases move across the alveolar-capillary membrane from high to low concentration until equilibrium is reached.

What drives ventilation?

Ventilation relies on changes in intrathoracic pressure and muscular action. Inspiration requires active muscular effort; expiration is generally passive, driven by lung elastic recoil.

What factors influence lung mechanics?

Compliance refers to how easily the lungs expand—reduced in fibrosis, increased in conditions like emphysema.
Resistance refers to airflow impediments (e.g. airway narrowing due to bronchoconstriction or secretions).

Control of Breathing

What regulates respiration neurologically and chemically?

The medullary respiratory center in the brainstem integrates mechanical and chemical signals to modulate breathing via the spinal cord and phrenic nerves.

Chemoreceptors:

Central chemoreceptors (in the medulla) detect changes in CO₂ and pH levels in cerebrospinal fluid and adjust ventilation accordingly.
Peripheral chemoreceptors (in carotid and aortic bodies) respond to low PaO₂, increased PaCO₂, and reduced pH, stimulating increased respiratory drive.

Mechanical receptors:

Irritant receptors, stretch receptors (triggering the Hering–Breuer reflex), and juxtacapillary (J) receptors sense physical changes in airways, lung tissue, and bronchial vessels.

Is there a difference in patients with COPD?

Yes. In chronic obstructive pulmonary disease (COPD), chronically elevated PaCO₂ blunts central chemoreceptor sensitivity, leading patients to rely more on a hypoxic drive (low oxygen) to regulate breathing.

Innate Respiratory Defense Mechanisms

The respiratory system employs multiple defense strategies:

Air filtration via nasal hairs and turbulence
Mucociliary clearance (the “mucus escalator”)
Cough reflex
Bronchoconstriction in response to irritants
Alveolar macrophages that engulf pathogens and debris

Age‑Related (Geriatric) Respiratory Changes

Structural: Decreased chest wall mobility and fewer functional alveoli.
Defense mechanisms: Reduced mucociliary activity and immune efficiency.
Regulatory: Slower and less sensitive respiratory responses to changes in O₂ and CO₂.

Assessment of the Respiratory System

Health History – What subjective (patient-reported) data is important?

Past medical conditions (e.g., asthma, COPD), allergies, surgeries, and current medications, including over‑the‑counter or illicit drug use and supplemental oxygen.
Lifestyle aspects: smoking history or exposure to secondhand smoke, travel, vaccination status.
Symptoms: cough (onset, sputum), dyspnea, fatigue, chest pain; note cough quality, triggers, sputum characteristics.
Family history: cystic fibrosis, COPD, asthma.
Functional patterns: weight changes, nutrition, activity tolerance, sleep disturbances (apnea, nocturnal awakenings), cognition, body image, social roles, stress-coping, and adherence beliefs.

Physical Examination – Which objective findings are evaluated?

Vital signs including pulse oximetry.
Head & neck exam: inspect nose, lips, oral cavity, pharynx, lymph nodes.
Thorax and lungs: observe chest shape, respiratory effort, skin, and fingernails (cyanosis, clubbing).
Palpation: tracheal position, chest expansion, tactile fremitus.
Percussion: lung resonance or dullness depending on underlying tissue or consolidation.
Auscultation: breath sounds including crackles, wheezes, stridor, pleural rubs; voice sounds—egophony, bronchophony, whispered pectoriloquy.