3. Mammal Gas Exchange Flashcards
What membranes surround the lungs?
Pleural membranes
Where is the pleural fluid?
In the pleural cavity (space between ribs & lungs)
Ventilation
Movement of air into & out of the lungs in 2 stages: inspiration & expiration.
What is ventilation controlled by?
Movement of the diaphragm and ribcage
Why do we breathe out CO2?
CO2 is acidic (dissolves to form carbonic acid) so lowers blood pH: not optimal for enzymes
2 reasons for C-shaped cartilage rings in trachea
- Prevents kinking
2. Keeps airways open no matter what you do/which way you twist your neck
What is the trachea made of?
Smooth muscle & elastic tissue - allows constriction & recoil respectively
Why are the cartilage rings in the trachea in gaps?
Maintains flexibility
What produces mucus?
Goblet cells
What do the cilia in the trachea do?
They waft mucus up & away from the lungs.
Either cough it out or swallow it: stomach acid will kill bacteria
What effect does cigarette smoke have on the cilia?
Cilia get paralysed
3 features of lungs that make it efficient for gas exchange
- Large SA
- Short diffusion distance
- Steep conc gradient
Epithelium definition
Cells that line the exterior surface of the body and body tubes that exchange materials with the external environment, such as the digestive & respiratory tracts
How many membranes must an oxygen molecule pass through in order to enter an erythrocyte?
5!
Alveoli & capillaries are one cell thick. There is also one membrane to pass through in the RBC.
Type I pneumocytes
- A single layer of cells form the walls of an alveolus
- Extremely thin: short diffusion distance
- Permeable: aids diffusion
Type II pneumocytes
- Secrete fluid to moisten the inner surface of the alveolus to reduce tension
- Fluid aids diffusion of gases
- Fluid contains surfactant to prevent the walls sticking together - maintains the lumen
- Can divide to form type I pneumocytes: repair damage
What are there more of: type I or type II pneumocytes?
Type I
Fick’s Law
Rate of diffusion is proportional to both SA & conc difference, but inversely proportional to membrane thickness (distance)
How is a large surface area achieved in mammal gas exchange systems?
Huge number of very small alveoli
How is a short diffusion distance achieved in mammal gas exchange systems?
- Alveolar wall epithelial cells are flattened, with only a thin layer of cytoplasm between their cell surface membranes
- Alveoli covered with a network of blood capillaries which also have very thin endothelial cells
- RBCs touch the walls of the capillaries as they pass through
How is a steep concentration gradient achieved in mammal gas exchange systems?
- Ventilation of the lungs
2. Blood constantly flowing through the capillaries
Steps of inhalation
- Abdominal muscles relax
- Diaphragm contracts & flattens/moves downwards
- Internal intercostal muscles relax
- External intercostal muscles contract
- Ribcage moves up & out
- Volume increases
- Pressure decreases so air is drawn inwards
Steps of exhalation
- Abdominal muscles contract, pushing the diaphragm up
- Diaphragm relaxes & returns to its dome shape
- Internal intercostal muscles contract
- External intercostal muscles relax
- Ribcage moves down & inwards
- Volume decreases
- Pressure increases so air moves outwards
What is tidal volume?
Resting breathing rate
The volume of one breath (measured in dm cubed)
