Respiration is carried out by all living things. Animals need oxygen to carry out aerobic respiration and they need to get rid of the waste product called carbon dioxide. This is called gas exchange. Swapping one gas for another. Animals have evolved different mechanisms for carrying out gaseous exchange. The most important thing is to create a large surface area, the bigger the surface area the faster diffusion of the gases can occur. Secondly they all have a good blood supply. You want to get oxygen into the blood and carbon dioxide out as quickly as possible so the blood travels very close to the exchange surface to once again maximise diffusion.
Insect Respiratory System Insects require oxygen just as we do, and must "exhale" carbon dioxide, a waste product of cellular respiration. Oxygen is delivered to the cells directly through respiration, and not carried by blood as in vertebrates. Along the sides of the thorax and abdomen, a row of small openings called spiracles (8) allow the intake of oxygen from the air. Most insects have one pair of spiracles per body segment. Small flaps or valves keep the spiracle closed until there is a need for oxygen uptake and carbon dioxide discharge. When the muscles controlling the valves relax, the valves open and the insect takes a breath. Once entering through the spiracle, oxygen travels through the tracheal trunk (8), which divides into smaller tracheal tubes. The tubes continue to divide, creating a branching network that reaches each cell in the body. Carbon dioxide released from the cell follows the same pathway back to the spiracles and out of the body. Most of the tracheal tubes are reinforced by taenidia, ridges that run spirally around the tubes to keep them from collapsing. In some areas, however, there are no taenidia, and the tube functions as an air sac capable of storing air. In aquatic insects, the air sacs enable them to "hold their breath" while under water. They simply store air until they surface again. Insects in dry climates may also store air and keep their spiracles closed, to prevent water in their bodies from evaporating. Some insects forcefully blow air from the air sacs and out the spiracles when threatened, making a noise loud enough to startle a potential predator or curious person.
In this video we examine the gills as an example of an exchange surface. We also discuss how fish pass water over their gills and how countercurrent flow maintains favourable exchange of oxygen.
So we all know that breathing is pretty important, right? Today we're going to talk about how it works, starting with the nameless evolutionary ancestor that we inherited this from, and continuing to the mechanics of both simple diffusion and bulk flow, as well as the physiology of breathing, and finishing with the anatomy of both the conducting zone and the respiratory zone of your respiratory system.
Can a paper bag really help you when you are hyperventilating? It turns out that it can. In part 2 of our look at your respiratory system Hank explains how your blood cells exchange oxygen and CO2 to maintain homeostasis. We'll dive into partial pressure gradients, and how they, along with changes in blood temperature, acidity, and CO2 concentrations, change how hemoglobin binds to gases in your blood.
Hank takes us on a trip around the body - we follow the circulatory and respiratory systems as they deliver oxygen and remove carbon dioxide from cells, and help make it possible for our bodies to function.