7.2 Mammalian Gaseous Exchange System Flashcards
Define ventilation
The process in which air is constantly moved in and out of the lungs to maintain diffusion of gases across the alveolar epithelium
Label this image of the human gaseous exchange system
What is the pathway of air into the lungs?
- Air enters theorugh the mouth and the nose then down the trachea
- The trachea splits into two bronchi, one bronchus leading to each lung
- Each bronchus then branches off into small tubes called bronchioles
- The bronchioles end in small ‘air sacs’ called alveoli where gases are exchanged
- The ribcage, intercostal muscles and diaphragm all work together to move air into and out of the
What is each lung surrounded by?
Pleural fluid
What is the role of pleural fluid?
Lubricates the lungs and helps the lungs to adhere to the walls of the thoracic cavity by water cohesion, this allows the lungs to expand with the chest during inhalation
What are the important features of the nasal cavity?
-A large surface area with a good blood supply, which warms the air to body temperature
-A hairy lining, which secrets muscles to trap dust and bacteria, protecting the lung tissue from irritation and infection
-Moist surfaces, which increase the humidity of incoming air, reducing evaporation from the exchange surfaces
What cells and tissues does the trachea contain?
C shaped cartilage, Smooth muscle, Elastic fibres, Goblet cells, Ciliated epithelium
How does cartilage benefit the trachea?
Provide support which stops the trachea from collapsing. Rings are incomplete so that food can move down the oesophagus behind it easily
What are the properties of cartilage?
Strong, flexible
How do goblet cells benefit the trachea?
Secrete mucus onto the lining of the trachea, to trap dust and microorganisms that have escaped the nose lining stopping them from reaching the alveoli
How do ciliated epithelial cells benefit the trachea?
Cilia beat and move the mucus along upwards away from the alveoli towards the throat
What cells and tissues does the bronchus contain?
Smaller rings of cartilage, smooth muscle, elastic fibres, goblet cells, ciliated epithelium
What cells and tissues does the bronchioles contain?
larger bronchioles - Smooth muscle, Elastic fibres, Goblet cells, Ciliated epithelium
smaller bronchioles - Smooth muscle, Elastic fibres, Ciliated epithelium
smallest bronchioles - Smooth muscle, Elastic fibres
Some larger bronchioles contain cartilage
How does smooth muscle benefit the bronchioles?
Allows their diameter to be controlled to change the amount of air reaching the lungs
What cells and tissues does the alveoli contain?
Elastic fibres, So collagen
How do elastic fibres benefit the alveoli?
Allow the alveoli to stretch so more air can be drawn in, and recoil to help squeeze air out known as elastic recoil
What is the definition of elastic recoil?
The ability of something to return to its original shape and size following stretch
Where in the human body does elastic recoil particularly occur?
Alveoli, arteries
What is the function of cartilage?
Provide structural support, holding structure open
Where in the mammalian gaseous exchange system is cartilage found?
Trachea, Bronchi, Some larger bronchioles
What is the function of smooth muscle?
Controls the diameter of tissues and cells, cosntrusts to restrict the flow of air, dilates to increase the flow of air
Where in the mammalian gaseous exchange system is smooth muscle found?
Trachea, Bronchi, Bronchioles
What is the function of elastic fibres?
Recoil and stretch to help take air in and breathe air out
Where in the mammalian gaseous exchange system are elastic fibres found?
Trachea, Bronchi, Bronchioles, Alveoli
What is the function of goblet cells?
Secrete mucus to trap microorganisms dust particles stopping them form reaching the alveoli towards
Where in the mammalian gaseous exchange system are goblet cells found?
Trachea, Bronchi, Larger bronchioles
What is the function of ciliated epithelium?
Beat in a synchronised pattern to waft muscular up the airway to the throat away from the alveoli towards prevent irrition and infection
Where in the mammalian gaseous exchange system is ciliated epithelium found?
Trachea, Bronchi, Larger and Smaller bronchi but not the smallest (terminal) bronchi
What type of epithelium does alveoli contain?
Squamous
How are the alveoli adapted for efficient gas exchange?
-Large surface area, large number of alveoli increase the space available for gas exchange
-Thin layers, only one epithelium cell thick so diffusion distance is short allowing for rapid diffusion
-Good blood supply, surrounded by millions of capillaries bringing CO2 and carrying off oxygen, this maintains a steep concentration gradient between the alveoli and capillaries
-Good ventilation, breathing moves air in and out of the alveoli helping maintain a steep diffusion gradient
What is the purpose of lung surfactant in the alveoli?
Ensures alveoli remain inflated
What is lung surfactant?
A chemical mixture containing phospholipids and both hydrophilic and hydrophobic proteins, which coat the surfaces of the alveoli and prevent them form collapsing
Label this diagram of the lungs
What are the mechanisms of breathing for inspiration?
-Active process, requires energy
-External intercostals contract moving ribs upwards and outwards
-Diaphragm contracts and flattens
-Volume of thoracic cavity increases
-Pressure of thoracic cavity decreases below pressure of atmospheric air so air is drawn inwards
What are the mechanisms of breathing for expiration?
-Passive process
-Diaphragm relaxes and returns to dome shape
-External intercostals relax moving ribs downwards and inwards
-Elastic fibres in alveoli return to normal stretch
-Volume of thoracic cavity decreases
-Pressure in thoracic cavity increases above atmospheric pressure so air moves out of the lungs
What happens when expiration is forced?
-The internal intercostals contract moving, to pull the ribcage down and in harder and faster
-Abdominal muscles contract forcing the diaphragm up to increase the pressure in the lungs rapidly
Label this diagram of the bell jar model of ventilation
What are the limitations of the bell jar model of ventilation?
-The bell jar is a rigid structure, which is unable to move in the same way as a ribcage
-Model shows lungs as empty scars whereas in reality the lung is composed of many alveoli
-The rubber sheet needs to be pulled down for the ballon’s to inflate whereas the diaphragms only flattens to cause air to enter the lungs
-The bell jar is filled with air, whereas the chest cavity is filled with pleural fluid
-Does not include structures such as the alveoli
