Structure & Function of the Respiratory System

These flashcards contain critical vocabulary terms and their definitions related to the structure and function of the respiratory system, gas laws, ventilation, lung compliance, and gas transport.

Ventilation

The exchange of air between the atmosphere and the lungs.

Inspiration

The process of air moving into the lungs.

Expiration

The process of air moving out of the lungs.

Alveoli

Tiny hollow sacs where gas exchange occurs.

Type I alveolar cells

Large but thin cells that allow rapid gas diffusion.

Type II alveolar cells

Smaller but thicker cells that synthesize and secrete surfactant.

Pulmonary Compliance

The ability of the lungs to stretch; higher compliance means easier expansion.

Lung Elastance

The degree and speed of lung return to resting volume after being stretched.

Gas Exchange

The diffusion of oxygen and carbon dioxide between alveoli and blood.

Partial Pressure

The pressure exerted by a gas in a mixture of gases.

Spirometer

An instrument that measures the movement of air during breathing.

Vital Capacity (VC)

The maximum amount of air that can be voluntarily moved in and out of the respiratory system.

Tidal Volume (TV)

The amount of air moved in a single normal inspiration or expiration.

Functional Residual Capacity (FRC)

The volume of air remaining in the lungs after normal expiration.

Alveolar Ventilation

The amount of air that reaches the alveoli each minute.

Dead Space

The volume of air that does not participate in gas exchange.

Central Chemoreceptors

Chemoreceptors located in the medulla oblongata that primarily control ventilation based on CO2 levels.

Peripheral Chemoreceptors

Chemoreceptors located in carotid bodies that sense changes in PO2 and pH.

Bronchodilation

The dilation of bronchi and bronchioles, decreasing resistance and increasing airflow.

Bronchoconstriction

The constriction of bronchi and bronchioles, increasing resistance and decreasing airflow.

Primary function of the respiratory system

To facilitate gas exchange, bringing $O<em>2$ into the body and removing $CO</em>2$.

Additional functions of the respiratory system

Includes vocalization, olfaction, regulating body pH, and protecting from pathogens.

The four main processes of external respiration

1. Ventilation, 2. Exchange of $O<em>2$ and $CO</em>2$ between alveoli and blood, 3. Transport of gases in the blood, 4. Exchange of gases between blood and tissues.

Two main divisions of the respiratory system based on function

The conducting system (for airflow) and the exchange surface (for gas diffusion).

Upper respiratory tract

Includes the nose, nasal cavity, pharynx, and larynx.

Lower respiratory tract

Includes the trachea, bronchi, bronchioles, and lungs.

Role of the conducting system

To warm, humidify, and filter incoming air before it reaches the exchange surface.

Features of the respiratory exchange surface

Large surface area, thin barrier for diffusion, and moist surface.

Pulmonary circulation

The flow of blood from the right ventricle of the heart, through the pulmonary arteries to the lungs, and back to the left atrium via the pulmonary veins.

Components of the respiratory pumping system

The bones and muscles of the thorax (rib cage, sternum, thoracic vertebrae), the diaphragm, and the pleural membranes.

Boyle's Law

States that at constant temperature, the pressure of a given quantity of gas is inversely proportional to its volume ($P<em>1V</em>1 = P<em>2V</em>2$).

Dalton's Law of Partial Pressures

States that the total pressure of a mixture of gases is the sum of the partial pressures of the individual gases.

Henry's Law

States that at a given temperature, the amount of gas dissolved in a liquid is proportional to its partial pressure in the gas phase.

How does partial pressure relate to gas movement?

Gases move from an area of higher partial pressure to an area of lower partial pressure.

The primary muscle for quiet inspiration

The diaphragm.

Muscles involved in quiet expiration

Primarily passive recoil of the lungs due to elastance; no active muscle contraction is typically required.

Muscles used for forced inspiration

External intercostals, sternocleidomastoids, and scalenes.

Muscles used for forced expiration

Internal intercostals and abdominal muscles.

Intrapleural pressure

The pressure within the pleural cavity, which is normally negative relative to atmospheric pressure, preventing lung collapse.

Factors affecting pulmonary compliance

Lung tissue elasticity and surface tension in the alveoli (reduced by surfactant).

Role of lung elastance in breathing

Its passive recoil helps drive expiration, returning the lungs to their resting volume.

Airway resistance

The opposition to airflow in the respiratory tract, primarily determined by the diameter of the bronchioles.

Factors that increase airway resistance

Bronchoconstriction, mucus accumulation, and inflammation.

Inspiratory Reserve Volume (IRV)

The additional volume of air that can be forcibly inhaled after a normal inspiration.

Expiratory Reserve Volume (ERV)

The additional volume of air that can be forcibly exhaled after a normal expiration.

Residual Volume (RV)

The volume of air remaining in the lungs after a maximal exhalation.

Forced Expiratory Volume in 1 second (FEV1)

The volume of air that can be exhaled in the first second during a forced exhalation.

Factors that optimize gas exchange efficiency

Large alveolar surface area, thin diffusion barrier, steep partial pressure gradients, and matching of ventilation to perfusion.

How is most oxygen transported in the blood?

Bound to hemoglobin within red blood cells.

Three main ways carbon dioxide is transported in the blood

1. As bicarbonate ions ($HCO_3^{-}$), 2. Bound to hemoglobin (carbaminohemoglobin), 3. Dissolved in plasma.

Ventilation-Perfusion (V/Q) ratio

The ratio of alveolar ventilation to pulmonary blood flow, indicating how effectively gas exchange occurs.

What do central chemoreceptors primarily sense?

Changes in $PCO_2$ and pH in the cerebrospinal fluid.

What do peripheral chemoreceptors primarily sense?

Major changes in arterial $PO<em>2$, as well as $PCO</em>2$ and pH.

Hering-Breuer reflex

A protective reflex triggered by stretch receptors in the lungs, which inhibits inspiration to prevent over-inflation.

Irritant receptors

Sensory nerve endings in the airway mucosa that respond to inhaled irritants, often causing reflex bronchoconstriction and coughing.

Juxtacapillary (J) receptors

Receptors in the alveolar walls that respond to conditions like pulmonary edema or emboli, leading to rapid, shallow breathing.