10.2 Respiratory structures and processes Flashcards
Respiratory structures
There are 4 structural features required in the mammal respiratory system
A thin permeable respiratory membrane through which diffusion can occur
Large surface area for gas exchange
A good supply of blood
A breathing system for bringing oxygen-rich air to respiratory membrane
The lungs
The lungs alone it the first three structural features
Permeable membrane, large surface area and good supply of blood
Due to importance, they are in the thoracic cavity, and protected by the rib cage
How oxygen gets to the lungs
- Air enters our body through the nose and mouth
- The air warms and moistens in the nasal passages and the mouth
- The nasal passages are lined with tiny hairs and mucus to filter dirt
- The air reaches the pharynx
- The epiglottis closes the glottis, blocking the trachea. Usually the glottis remains open for oxygen to flow
- Air flows from the pharynx into the trachea lined with cilia that also filter the air
- The trachea branches into two bronchi each connecting to a lung
- Inside the lungs the bronchi divide into smaller tubes called bronchioles to form a respiratory tree
- The airway ends in tiny sacs called alveoli. Each network of alveolus is surrounded by a capillary network to diffuse oxygen and CO2. There are 150 million alveoli which is why the surface area is so large.
Gas exchange in alveoli
Air is now moist which allows for diffusion to occur
Walls of alveoli are thin allowing for oxygen to diffuse into the blood and carbon dioxide out of the blood
Diaphragm-inhalation
At the bottom of the lungs is your diaphragm that separates the thoracic cavity from the abdomen
When inhaling the brain causes the diaphragm to contract, shortening it
Simultaneously, external intercostal muscles contract and pull the ribs outward
This whole process causes the lungs to expand, increasing volume and reducing pressure
The pressure is now larger outside causing air to rush to the lungs
Diaphragm-exhalation
When we exhale the diaphragm relaxes to its usual shape
The external intercostal muscles also relax, decreasing the size of the chest cavity
This reduces the size of the lungs and increases their pressure
The atmospheric pressure is now less then the pressure in the lungs causing the air to flow out of the lungs
Exercise and activity
During exercise a second set of muscles called internal intercostal muscles start to contract and relax
When they contract, they pull the rib cage downward, increasing pressure inside the lungs, and forcing more air out of the lungs
This is why we tend to have deeper breaths when we exercise
Friction
The pleural membrane cover the lungs and line the thoracic cavity with a thin layer of tissue
Between the membrane and the lungs is the pleural cavity which is full of fluid to prevent friction
Is this membrane has air introduced (Puncture from ribs), the membrane separates from the lungs
This prevents the lung from expanding and collapsing, causing a collapsed lung or pneumothorax
Lung capacity
The volume of air in our lungs varies
Total lung capacity is the maximum volume of O2 inhaled in a single breath
Typically between 3-5L
During regular breathing we take only a fraction of this which is called Tidal volume
Typically 0.5L
After normal inhalation, we still have lots of room left. The room left is called inspiratory reserve volume
After exhalation, there is still lots of room left, called the expiratory reserve volume
Even after max exhalation, there is O2 available outside of the expiratory reserve volume, which is the Residual volume (to prevent a collapsed lung)
The Vital capacity is then defined as the maximum O2 we can inhale or exhale
Oxygen usage
The higher rate of oxygen usage in the body indicates an efficient respiratory system
Meaning the more O2 you use, the more efficient your system is
The rate at which O2 is used is the VO2 measured in mm per kg per min
The max rate of O2 usage in the body is defined as the VO2 max
