Human Gas Exchange and Transport

What happens to surface area-to-volume ratio as organisms increase in size?

It decreases.

Why do larger organisms face greater challenges in gas exchange?

Because internal cells are farther from the exterior and SA:V ratio decreases.

What is gas exchange?

The movement of oxygen into the body and carbon dioxide out across a respiratory surface.

What role does diffusion play in gas exchange?

It allows gases to move passively from high to low concentration.

Why do larger organisms need special structures for gas exchange?

To provide enough surface area for diffusion.

Why must gas-exchange surfaces be permeable?

So gases can easily cross the membrane.

Why must gas-exchange surfaces be thin?

To reduce diffusion distance and speed diffusion.

Why must gas-exchange surfaces be moist?

So gases can dissolve and diffuse across membranes.

Why must gas-exchange surfaces have a large surface area?

To maximize the amount of gas that can diffuse at once.

Why do gas-exchange surfaces have dense networks of blood vessels?

To transport gases quickly and maintain gradients.

Why must blood flow be continuous at gas-exchange surfaces?

To maintain steep concentration gradients.

Why do lungs require ventilation with air?

To bring in fresh oxygen and remove carbon dioxide.

Why do gills require water flow over them?

To maintain concentration gradients necessary for diffusion.

Why must concentration gradients be maintained at gas-exchange surfaces?

Diffusion only occurs when gradients exist.

How does cellular respiration help maintain concentration gradients?

It uses oxygen and produces carbon dioxide.

How does blood flow help maintain concentration gradients?

It removes absorbed oxygen and brings carbon dioxide.

How does ventilation help maintain concentration gradients?

It replaces stale air with fresh air.

What is cellular respiration?

The breakdown of glucose to release energy using oxygen and producing carbon dioxide.

What is the function of surfactant in alveoli?

It reduces surface tension and prevents alveolar collapse.

How do branched bronchioles aid gas exchange?

They increase surface area and deliver air efficiently.

Why are extensive capillary beds important in the lungs?

They maximize blood contact for rapid diffusion.

Why is high surface area important in the lungs?

It increases the rate of gas exchange.

Where does gas exchange occur in humans?

In the alveoli of the lungs.

What structures connect the alveoli to the outside of the body?

Bronchioles → bronchi → trachea → larynx → pharynx → nose/mouth.

What is ventilation?

The movement of air into and out of the lungs.

What is inspiration?

The process of drawing air into the lungs.

What is expiration?

The process of expelling air from the lungs.

What is the relationship between gas pressure and volume?

They are inversely related (Boyle’s law).

What happens to lung volume and pressure during inspiration?

Volume increases and pressure decreases.

What happens to lung volume and pressure during expiration?

Volume decreases and pressure increases.

What does the diaphragm do during inspiration?

It contracts and flattens.

What does the diaphragm do during expiration?

It relaxes and moves upward.

What do the external intercostal muscles do during inspiration?

They contract to lift the ribs upward and outward.

What do the external intercostal muscles do during expiration?

They relax, lowering the ribs.

What do abdominal muscles do during forced expiration?

They contract to push the diaphragm upward.

How do the ribs move during inspiration?

They move upward and outward.

How do the ribs move during expiration?

They move downward and inward.

What is ventilation rate?

The number of breaths taken per minute.

What is tidal volume?

The amount of air inhaled or exhaled in a normal breath.

What is vital capacity?

The maximum amount of air exhaled after a maximum inhalation.

What is inspiratory reserve volume?

The extra air inhaled beyond normal inspiration.

What is expiratory reserve volume?

The extra air exhaled beyond normal expiration.

How is tidal volume measured?

Using a spirometer.

How is vital capacity measured?

Using a spirometer.

How are inspiratory and expiratory reserves measured?

Using spirometry during forced breathing.

Why do capillaries have a small lumen diameter?

To force blood cells close to the wall for efficient diffusion.

Why are capillaries highly branched?

To increase surface area for exchange.

Why do capillaries have very thin walls?

To reduce diffusion distance.

Why do some capillaries have fenestrations?

To allow rapid exchange of substances.

How do artery walls compare to vein walls?

Artery walls are thicker.

How does lumen size differ between arteries and veins?

Veins have larger lumens.

Do arteries or veins contain valves?

Veins contain valves; arteries do not.

Which vessel has more smooth muscle: artery or vein?

Arteries.

What is the function of arteries?

To carry blood away from the heart under high pressure.

What are the three layers of an artery wall?

Tunica externa, tunica media, and tunica intima.

What is the function of the tunica externa?

To provide strength and prevent overstretching.

What is the function of the tunica media?

To provide elasticity and muscle control for pressure maintenance.

What is the function of the tunica intima?

To provide a smooth inner lining.

How do arteries withstand high pressure?

Thick, elastic walls absorb and maintain pressure.

What is the unit used to measure pulse rate?

Beats per minute (bpm).

What is one method to measure heart rate?

Feeling the radial or carotid pulse.

What is another method to measure heart rate?

Using a digital heart rate monitor.

What is the function of veins?

To return blood to the heart at low pressure.

Why do veins contain pocket valves?

To prevent backflow of blood.

Why do veins have thin walls?

To allow compression by surrounding muscles.

How do skeletal muscles help veins?

They squeeze veins to move blood forward.

What is the function of the coronary arteries?

To supply the heart muscle with oxygenated blood.

What causes a coronary occlusion?

Plaque buildup that narrows or blocks a coronary artery.

What is one consequence of coronary occlusion?

Reduced blood flow leading to heart attack.

What dietary factor increases risk of CHD?

High intake of saturated fats.

What lifestyle factor increases risk of CHD?

Smoking, inactivity, or chronic stress.

What factors increase the risk of coronary occlusion?

Smoking, high LDL, high blood pressure, diabetes, and obesity.