Place the following in order from highest to lowest expected partial pressure oxygen levels.

• cells of systemic tissues
• atmospheric air
• systemic capillaries
• pulmonary capillaries
• alveoli of lungs

Atmospheric air

Alveoli of lungs

Pulmonary capillaries

Systemic capillaries

Cells of systemic tissues

Explanation:

Partial pressure of oxygen levels in the blood is very important for the oxygen diffusion.Partial pressure  of oxygen is defined as the amount of pressure exerted by oxygen in the blood. If two adjacent areas have a different partial pressure of the oxygen, the oxygen will move from the area of higher concentration to the area of lower concentration until it reaches equilibrium. So this is a principle by which oxygen is picked up from the atmospheric air, transported through the capillaries and other vessels and delivered to the cells of systemic tissues.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!