Lungs
Breathing
Inhalation and Exhalation
or is it Inspiration and Expiration..
To inhale, the diaphragm contracts, pulling on the bottom of the ribs, causing it to straighten (rather than being curved upwards) this increases the space inside the rib cage.
At the same time the External Intercostal muscles contract, causing the rib cage to change shape, with the bottom of it spreading outwards, again increasing the space inside the rib cage.
As the space increases inside the ribcage (the pleural cavity) the lungs expand to occupy this space. This decreases the pressure inside the lungs relative to the outside space. Air flows from an area of higher pressure to an area of lower pressure, so air pours into the lungs.
To exhale the diaphragm relaxes and the intercostal muscles relax, the ribcage springs back to its rest state. To exhale with force, like when you are blowing up a balloon, your abdominal muscles get involved, pulling down on the rib cage, pulling the bottom of the rib cage down into a smaller space. At the same time the Internal Intercostal muscles pull the rib cage down making it smaller as well.
It is the bottom of the ribs that move the most. You can test this by doing the following:
Place hands on ribs with thumb under armpit and fingers pointed towards sternum
Feel the movement of the rib cage as you:
Breath in till your lungs are completely full
Breath out till your lungs are as empty as you can make them
Repeat
Place hands on the bottom sides of the ribcage with thumb along the side of the ribcage and fingers pointed towards sternum
Feel the movement of the rib cage as you:
Breath in till your lungs are completely full
Breath out till your lungs are as empty as you can make them
Repeat
Although the greatest range of movement is at the bottom of the ribs, the pressure change inside the lungs is equal
Side note, when you eat 'spare ribs' you are eating the internal and external intercostal muscles.
Structure of the lungs
Trees follow the pattern of:
Trunk
Limbs
Branches
Secondary branches off the bigger branches
Twigs
Millions of leaves
These leaves take in Carbon Dioxide and release Oxygen.
Lungs follow the pattern of:
Trachea
With rings of Cartilage to keep it open
You can feel these cartilage rings on the 'windpipe' part of your throat
Primary Bronchi
Of which there are two, Right and Left.
These are held open with cartilage rings
Secondary Bronchi
Branches from the primary Bronchi
Segmental Bronchi
Branches form the Secondary Bronchi and each branch off the first Segmental Bronchi are also called Segmental Bronchi.
You can also label them fourth order through to sixth order depending on how many branches they have branched off These all contain cartilage to keep them open
Bronchioles
These are the twigs.
They are too small to have any cartilage. They are kept open by elastic tissue and smooth muscle
Bronchioles
These branch off Bronchioles
Terminal Bronchioles
These are the stems of the leaves. are around 80 of these branching off each Bronchiole
Alveoli
This is where Gas Exchange occurs
These look like grapes
These Alveoli take in Oxygen and release Carbon Dioxide
Alveoli look like grapes and the Alveolar Sacks look like bunches of grapes.
The arterioles and venules meet on these grapes. Connecting through the capillaries that wrap around the alveoli
Alveoli + Capillaries = Gas Exchange
The alveoli are only 1 cell thick.
Capillaries are only 1 cell thick.
So the oxygen and carbon dioxide only need to cross two cells!
As for all animals, there needs to be liquid for gas exchange to work. Our lungs are lined with liquid. Oxygen moves from the air into the liquid, then through the wall of the alveoli into the capillaries.
This liquid contains surfactant. Pulmonary Surfactant. This is a slippery substance that stops the walls of the alveoli from sticking together.
The liquid in the lungs is mostly water. Water is attracted to water, so if the lungs are wet and they touch, it could act like two planes of glass with water between them, stuck together and painful. The Surfactant stops the alveolar from getting stuck together.
Gas Exchange
Air contains 78% Nitrogen. This just moves in and out of your lungs
Air contains 20% oxygen
When this is inhaled it goes into the alveoli.
This 20% oxygen in the alveoli is more than the amount of free oxygen in the deoxygenated blood
Because there is more oxygen in the alveoli than in the blood the oxygen will diffuse from the alveolar into the bloodstream. The oxygen is then bound into the hemoglobin in the red blood cells, effectively making it 'disappear' from the blood stream, allowing the continued diffusion of oxygen into the blood stream until all of the hemoglobin is holding oxygen.
Air contains 0.03% Carbon Dioxide. This is less then the amount of Carbon Dioxide in the blood in the alveoli. So, the Carbon Dioxide diffuses from the blood into the alveolar air space.
Gas exchange in the Alveoli just follows the diffusion gradients for the gases.
Blood going to the alveoli has high carbon dioxide and low oxygen. Whilst the Alveoli air space has high oxygen and low Carbon Dioxide
Due to cellular respiration, when you exercise you produce more carbon dioxide and need more oxygen.
The heart will beat faster to move blood from the muscles to the lungs and back again faster. So, the CO2 from the muscles can not build up and the muscles get the oxygen that they need for aerobic respiration.
You breath more and deeper, ensuring that diffusion in the alveoli is as efficient as possible, thus the blood doesn't need to spend as much time there so it can zoom through with the pace set by the heart that's beating faster.
Ventilation, External Respiration, Internal Respiration, Cellular Respiration
Respiration
the movement of Oxygen and Carbon Dioxide through living systems
Ventilation
is the movement of air into (inhalation or inspiration) and out of (exhalation or expiration) the lungs.
Hence the phrase '"we've hooked him up to a ventilator"
External Respiration
is the movement of Oxygen from the alveoli into the blood, and the movement of Carbon dioxide from the blood into the alveoli.
External because this is where the gases move from the exterior environment and become assimilated with the body
Internal Respiration
is the movement of Oxygen from the blood into the cells, and the movement of Carbon Dioxide from the cells into Blood.
Internal because it in fully inside the body, its just blood and cells
Advanced Respiratory System
