Respiratory Anatomy & Gas Laws

What is the primary function of the respiratory system?

The respiratory system takes in oxygen and expels carbon dioxide; it enables breathing and gas exchange.

What are the two anatomical divisions of the respiratory system?

Upper respiratory system and lower respiratory system.

What are the two functional divisions of the respiratory system?

Conducting zone and respiratory zone.

What is the function of the conducting zone?

To prepare, warm, filter, and humidify air before gas exchange.

What is the function of the respiratory zone?

To perform gas exchange between air and blood.

What is the primary passageway for air entry?

The nose and nasal cavity.

What is the function of nasal hair?

To trap airborne particles.

What does turbulent airflow in the nasal cavity provide?

Extra time for warming/humidifying air, circulates odorants to receptors, and increases particle contact with mucus.

What is lost when breathing through the mouth?

Air warming, humidifying, odor detection efficiency, and particle filtration.

What is respiratory mucosa?

Epithelium + underlying lamina propria that lines the conducting portion of the respiratory tract.

Where does the pharynx change epithelium type and why?

At the nasopharynx-oropharynx boundary; it changes from pseudostratified columnar to stratified squamous because it is shared with the digestive system.

What is the larynx?

A cartilaginous tube that surrounds and protects the glottis.

What is the glottis?

A slit-like opening between the vocal cords.

What is the trachea?

A tough, flexible tube that carries air and branches into right and left bronchi.

How many tracheal cartilages are there?

20 C-shaped cartilages.

Why are tracheal cartilages C-shaped?

The open portion allows the trachea to distort so food can pass down the esophagus.

What is the function of pneumocyte type I cells?

They are the primary site of gas diffusion in the alveoli.

What is the function of pneumocyte type II cells?

They produce surfactant.

What is surfactant?

A substance that reduces surface tension in the alveoli and keeps them open.

What causes Respiratory Distress Syndrome?

Difficulty breathing due to alveolar collapse caused by inadequate surfactant production.

Why are premature infants prone to Respiratory Distress Syndrome?

They produce insufficient surfactant and often require surfactant replacement therapy.

Which epithelial type lines the nasal cavity, superior pharynx, and upper lower-respiratory tract?

Pseudostratified ciliated columnar epithelium with mucous cells.

What is the function of pseudostratified ciliated columnar epithelium?

To permit mucociliary clearance of trapped particles.

Which epithelial type lines the inferior pharynx?

Stratified squamous epithelium.

Why is stratified squamous epithelium found in the inferior pharynx?

To provide protection against abrasion.

Which epithelial type is found in smaller bronchioles?

Cuboidal epithelium with scattered cilia.

Which epithelial type lines the alveoli and why?

Simple squamous epithelium; it allows efficient gas exchange.

What is a pulmonary lobectomy?

Surgical removal of a diseased or cancerous segment (lobe) of the lung.

Why perform a pulmonary lobectomy?

To prevent diseased or cancerous tissue from spreading to the rest of the lung or body.

What creates the adhesion between lungs and the thoracic cavity?

A fluid bond between the parietal and visceral pleura.

What is the function of pleural fluid?

To lubricate the pleural cavity and reduce friction.

How do changes in thoracic cavity volume affect the lungs?

Changes in thoracic volume directly change lung volume because the pleura stick the lungs to the thoracic wall and diaphragm.

What is external respiration?

Gas exchange of oxygen and carbon dioxide between the external environment and interstitial fluids.

What is internal respiration?

Absorption of oxygen and release of carbon dioxide by body cells.

What is pulmonary ventilation?

The physical movement of air into and out of the lungs.

How does air flow during ventilation?

Air flows from an area of higher pressure to an area of lower pressure.

What determines pressure exerted by a gas?

The frequency of gas molecules bumping into the walls of the container.

According to Boyle's Law, what happens to pressure when volume decreases?

Pressure increases due to increased collision frequency.

According to Boyle's Law, what happens to pressure when volume increases?

Pressure decreases due to fewer collisions.

What factors favor an increase in lung volume (inspiration)?

Muscle contraction, high lung compliance, negative intrapleural pressure, and surfactant reducing surface tension.

How does diaphragm contraction affect lung volume?

The diaphragm moves downward, increasing thoracic cavity volume and decreasing pressure.

How do intercostal muscle contractions affect lung volume?

They lift the ribs, increasing thoracic volume and decreasing alveolar pressure.

What is lung compliance?

A measure of how easy it is to inflate the lungs; depends on negative intrapleural pressure and surfactant.

What factors favor a decrease in lung volume (expiration)?

Elastic recoil of alveolar walls, surface tension, and elastin fibers.

Are muscle contractions required for expiration?

Only during forced expiration, where abdominal contents are pushed upward.

What unit measures air pressure?

mmHg using a mercury barometer.

How does altitude affect air pressure and density?

Both decrease as altitude increases.

What is standard atmospheric pressure at sea level?

760 mmHg.

Does changing air pressure alter the composition of air?

No, only the density changes.

What happens to intrapulmonary pressure during a respiratory cycle?

It rises and falls as air moves into and out of the lungs.

What happens to intrapleural pressure during a respiratory cycle?

It becomes more negative during inhalation and less negative during exhalation.

What does a spirometry plot show?

The amount of air moving into and out of the lungs during a single respiratory cycle.

What happens when the pleural sac is punctured?

Intrapleural pressure equalizes with atmospheric pressure.

Why does intrapleural pressure equalize when the pleural sac is punctured?

Air flows from higher pressure to lower pressure.

What happens to intrapleural volume when the pleural sac is punctured?

It increases.

What happens to the lung when intrapleural pressure equalizes with atmospheric pressure?

The lung collapses (pneumothorax).

What does Dalton's Law state?

The total pressure of a gas mixture equals the sum of the partial pressures of each gas.

What determines the partial pressure of a gas?

It is directly proportional to its percentage in the gas mixture.

What are the three layers of the blood-air barrier?

Alveolar cell layer, capillary endothelial layer, fused basement membrane.

Why is gas exchange across the blood-air barrier fast and efficient?

Because diffusion distance is short and gases are lipid-soluble.

What is diffusion?

Bulk movement of molecules from high concentration to low concentration.

What does Fick's law describe?

Factors that influence the rate of diffusion across a membrane.

According to Fick's Law, what increases diffusion rate?

Larger surface area, higher gas diffusion coefficient, and greater partial pressure gradient.

What decreases diffusion rate according to Fick's Law?

Increased membrane thickness.

How does emphysema affect diffusion?

Decreases surface area for gas exchange.

How does pulmonary fibrosis affect diffusion?

Increases membrane thickness, reducing diffusion.

What does Henry's Law state?

Gases dissolve in a liquid in proportion to their partial pressures.

Why does opening a soda can cause fizzing?

CO₂ partial pressure in the can equilibrates with the much lower atmospheric CO₂ pressure.

Why does CO₂ diffuse at the same rate as O₂ despite a lower partial pressure gradient?

CO₂ is 20 times more soluble in plasma than O₂.

How soluble is nitrogen in plasma?

It is practically insoluble.