The Mammal Gas Exchange System (Human)
Structure
The human gas exchange system is composed of the nasal cavity, trachea, epiglottis, cartilage, cilia, bronchi, lungs, bronchiole, alveoli, diaphragm, heart and the capillaries.
When a human breathes in, the air travels down the larynx and the trachea, which both consist of rings of cartilage to support the airway open. The trachea branches off into the bronchi which then branches off into millions of tubes; the bronchioles forming the bronchial tree. The bronchioles end with bunches of alveoli(air sacs) that provide a moist gas exchange surface in which the oxygen is diffused in and the carbon dioxide is diffused out. For diffusion across the gas exchange surface, a steep concentration gradient is needed. When the alveoli are full of oxygen and are wrapped by blood capillaries, the oxygen can always diffuse down its concentration gradient from the air to the blood. At the same time, carbon dioxide diffuses from the blood to the air.
When a human breathes in, the air travels down the larynx and the trachea, which both consist of rings of cartilage to support the airway open. The trachea branches off into the bronchi which then branches off into millions of tubes; the bronchioles forming the bronchial tree. The bronchioles end with bunches of alveoli(air sacs) that provide a moist gas exchange surface in which the oxygen is diffused in and the carbon dioxide is diffused out. For diffusion across the gas exchange surface, a steep concentration gradient is needed. When the alveoli are full of oxygen and are wrapped by blood capillaries, the oxygen can always diffuse down its concentration gradient from the air to the blood. At the same time, carbon dioxide diffuses from the blood to the air.
What are the Advantages of a Mammal/Human's Environment?
Mammals can almost live in any habitat. But for the humans who live and thrive on land, the amount of oxygen concentration in the air is very high. Humans can easily ventilate oxygen in their gas exchange systems.
What are the Limitations of a Mammal/Human's Environment?
When the air is dry, it can cause the gas exchange surface (alveoli) to become susceptible to dessication. Air is also dirty, so the dirt particles that might travel down the spiracles along with the oxygen could damage the delicate gas exchange surfaces. The temperature can fluctuate, resulting in surprising, unexpected climate changes that might also affect the diffusion rate of oxygen.
Humans will often live in different climates, where some will live in higher altitudes than others. This results in humans living in higher altitudes to gain less oxygen. This is due to lower air pressure in higher altitudes. Temperature and the humidity of air can also limit the efficiency of gas exchange in mammals. If either or both the temperature and humidity of the air is high, then the air pressure will lower and the mammals will gain less oxygen from the air.
Humans will often live in different climates, where some will live in higher altitudes than others. This results in humans living in higher altitudes to gain less oxygen. This is due to lower air pressure in higher altitudes. Temperature and the humidity of air can also limit the efficiency of gas exchange in mammals. If either or both the temperature and humidity of the air is high, then the air pressure will lower and the mammals will gain less oxygen from the air.
What are the Advantages of a Mammal/Human's Gas Exchange System & How have they adapted to their Environment? (Compared to Insects)
1. Humans have their alveoli covered in surfactant which helps prevent dessication and maintains a moist surface for efficient gas exchange to occur, as living in a dry environment (air) can easily lead to dessication. Insects, however, have water at the end of their tracheoles to maintain their moist surface, due to their size and their abundance of a circulatory system.
2. Because mammals can grow larger than insects, this allows them to explore and expand their population over a large area of land. Mammals can grow larger than insects because they have a circulatory system. Oxygenated blood is pumped through the mammal's body whereas insects rely on simple diffusion only and can never grow as big as a human because their body proportions must be accurate in order to sufficiently undergo simple diffusion without a circulatory system.
3. Each alveoli is covered in a rich casing of blood capillaries. The alveoli are thin; the reduced diffusion distance is 0.5mm and is one blood cell thick. This increases the efficiency of the mammalian gas exchange system and the rate in which oxygen is diffused into the blood. Insects do not have a circulatory system. Therefore in their gas exchange system the oxygen is directly diffused from the air to the cells, and through the tracheoles.
2. Because mammals can grow larger than insects, this allows them to explore and expand their population over a large area of land. Mammals can grow larger than insects because they have a circulatory system. Oxygenated blood is pumped through the mammal's body whereas insects rely on simple diffusion only and can never grow as big as a human because their body proportions must be accurate in order to sufficiently undergo simple diffusion without a circulatory system.
3. Each alveoli is covered in a rich casing of blood capillaries. The alveoli are thin; the reduced diffusion distance is 0.5mm and is one blood cell thick. This increases the efficiency of the mammalian gas exchange system and the rate in which oxygen is diffused into the blood. Insects do not have a circulatory system. Therefore in their gas exchange system the oxygen is directly diffused from the air to the cells, and through the tracheoles.
4. When a mammal breathes, it is due to the thoraic cavity expanding and shrinking, led by the intercostal muscles and the diaphragm. Lungs do not have muscle and so rely on the two sets of muscles to ventilate the lungs.
What are the Limitations of a Mammal/Human's Gas Exchange System?
Because humans are homotherms (warm-blooded) they require a lot of energy to function and to maintain their body heat. In turn, this increases the amount of oxygen needed to efficiently power the body. Higher levels of oxygen is needed by the human body, yet tidal breathing is not efficient at all in transferring oxygen present in the air into the blood. This is because only some of the air inhaled will be used in the gas exchange which decreases the efficiency of the amount of oxygen diffused into the blood stream.
The gas exchange surface of humans are also prone to dessication via our own body heat combined with the dry air that is inhaled.
The gas exchange surface of humans are also prone to dessication via our own body heat combined with the dry air that is inhaled.