The Respiratory System and Gas Exchange

Acid Base Balance

The respiratory system helps control the hydrogen ion (H⁺) concentration in the blood, determining its pH.

Gas Concentration Control

The primary function of the respiratory system; it regulates the concentrations of Oxygen (O₂) and Carbon Dioxide (CO₂) in the blood.

Respiratory Membrane

The interface where gas diffusion occurs between the air in the alveolus and the blood in the capillary.

Pulmonary Ventilation

The clinical term for breathing, consisting of two phases: inhalation (air in) and exhalation (air out).

Intra-alveolar Pressure

The pressure inside the lungs, specifically the alveoli.

Intrapleural pressure

The pressure within the potential space between the visceral and parietal pleura.

Muscle of Respiration

Includes the diaphragm, external intercostals (expand volume), internal intercostals (decrease volume), and accessory muscles.

Boyle’s Law

As the volume of a container decreases, pressure increases due to more frequent collisions of molecules.

Lung Compliance

Refers to the 'stretchiness' of the lungs; affected by elastic fibers and pathologies.

Tidal Volume (VT)

The normal amount of air inhaled or exhaled during a calm breath, approximately 500 mL.

Total Lung Capacity (TLC)

The maximum amount of air the lungs can hold, typically 5,000 mL to 6,000 mL depending on body size.

Partial Pressure of O2 at Sea Level

Approximately 160 mm Hg, derived from the atmospheric pressure where Oxygen is about 21%.

External Respiration

Gas exchange between the alveoli and the blood in the pulmonary capillaries.

Carbon Monoxide Poisoning

CO binds to hemoglobin in place of O₂, hindering oxygen transport and leading to a lack of O₂ availability.

Medulla Oblongata

Area in the brain that houses the Dorsal Respiratory Group, setting the breathing rate of 12 to 20 breaths per minute.

Acute Mountain Sickness (AMS)

A condition occurring at altitudes over 12,000 feet, leading to hypoxia and possible cerebral or pulmonary edema.

Sleep Apnea

A sleep disorder often caused by airway abnormalities, treated with Continuous Positive Airway Pressure (CPAP).

Hyperventilation

Fast or deep breathing leading to excessive CO₂ expulsion and potential alkalosis; may be treated by re-inhaling CO

External intercostals

Muscles that elevate the ribs, increasing thoracic volume during inhalation.

Internal intercostals

Muscles that depress the ribs, decreasing thoracic volume during forced expiration.

Diaphragm

The primary muscle of respiration, acting as the 'floor' of the thoracic cavity and enabling inhalation by flattening when contracted.

Accessory Muscles

Additional muscles engaged during forced breathing to assist with inhalation or exhalation, such as the sternocleidomastoid and scalene muscles.

Alveolar Surface Tension

The force that causes alveoli to collapse, mitigated by surfactant, which reduces surface tension.

Emphysema

A chronic lung condition characterized by the destruction of alveoli, leading to decreased elastic recoil and impaired gas exchange.

Inspiratory Reserve Volume (IRV)

The additional air that can be inhaled forcefully after a normal tidal breath, typically around 3,000 mL.

Vital Capacity (VC)

The maximum amount of air a person can exhale after maximum inhalation; calculated as Tidal Volume (V_T) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV).

Dalton’s Law of Partial Pressures

States that the total pressure of a gas mixture is equal to the sum of the partial pressures of individual gases within that mixture.

Internal Respiration

The process of gas exchange between the blood in systemic capillaries and the tissue spaces, facilitating oxygen delivery to cells and carbon dioxide removal.

Cellular Respiration

The metabolic process within cells where food molecules are converted to energy, producing carbon dioxide as a byproduct.

Hypoventilation

Abnormally slow or shallow breathing leading to increased carbon dioxide levels and respiratory acidosis.

Apnea

A temporary cessation of breathing, which can occur during sleep or

3 components of respiratory membrane

alveolar epithelium, fused basal membrane, and capillary endothelium

Tidal Volume value

500 mL/Breath

Inspiratory Reserve Value

1900-3200 mL

Dead space value

150 mL

Vital Capacity value

4800 mL

Total Lung Capacity

5-6 liters

Alveolar Ventilation (AV)

The volume of air that reaches the alveoli and particpates in gas exchange

AV= TV- VD

Muscles of forced expiration

Internal intercostal and abdominal muscles

Muscles of forced inspiration

sternocleidomastoids, pectoralis, and serratus

Muscle action during expiration at rest

External intercostal muscles and diaphragm receives impulses from DRG and contracts.

muscles of inspiration at rest

Dorsal respiratory group (DRG)

Decreases the stretchiness of lung tissue

Lung cancer, Fibrosis, Scarring

Pneumothorax

A pneumothorax occurs when the seal between the visceral and parietal pleura is broken, causing the lung to collapse.

Medulla Oblongata

contains the DRG

Pons

Contains the Pneumotaxic Center

Upper airways

nose, pharynx, and larynx

Lower airways

trachea, bronchi, bronchioles, and lungs

Paranasal sinuses

Sphenoid sinus, Frontal sinus, Ethmoid cells, Maxillary sinus

Pharynx parts

Nasopharynx → Oropharynx → Laryngopharynx

Epiglottis

closes the opening to the trachea upon swallowing