AP BIOLOGY

Detailed explanation-1: -In a process called diffusion, oxygen moves from the alveoli to the blood through the capillaries (tiny blood vessels) lining the alveolar walls. Once in the bloodstream, oxygen gets picked up by the hemoglobin in red blood cells.

Detailed explanation-2: -The walls of the alveoli share a membrane with the capillaries. That’s how close they are. This lets oxygen and carbon dioxide diffuse, or move freely, between the respiratory system and the bloodstream. Oxygen molecules attach to red blood cells, which travel back to the heart.

Detailed explanation-3: -How does oxygen get into the bloodstream? Inside the air sacs, oxygen moves across paper-thin walls to tiny blood vessels called capillaries and into your blood. A protein called haemoglobin in the red blood cells then carries the oxygen around your body.

Detailed explanation-4: -The oxygen diffusion gradient from alveoli to capillary blood is approximately 40 mmHg. Carbon dioxide and oxygen directly compete with each other for hemoglobin binding. The unloading portion of the oxyhemoglobin dissociation curve has a steeper slope than the loading portion.

Detailed explanation-5: -This barrier between air and blood averages about 1 micron (1/10, 000 of a centimeter, or 0.000039 inch) in thickness. Oxygen passes quickly through this air-blood barrier into the blood in the capillaries. Similarly, carbon dioxide passes from the blood into the alveoli and is then exhaled.