Gas exchange 👍 Flashcards
Describe type I pneumocytes
- Cover 70% of the internal surface area of each alvelous.
- Thin, flattened epithelial cells.
- Amitotic and unable to replicate
- Connected by occluding junctions which prevent leakage
What is the function and adaptations of type I pneumocytes
Gas exchange. They’re extremely thin to make them:
1. More permeable
2. Shorter diffusion distance
What is the route of air during ventilation?
Nose/mouth
Nasal cavity
Larynx
Epiglottis
Trachea
Bronchi
Bronchioles
Alveoli
Process of inspiration regarding body/organs
As you inhale the external intercostal muscles contract (internal intercostal relax) which causes the ribcage to move up and out, and the diaphragm flattens downward. Abdominal muscles relax. Through the expansion the pressure decreases and the volume increases. Decrease in pressure causes the air to flow in, causing the lungs to inflate and gas exchange to happen in the alveoli.
Process of expiration regarding body/organs
The internal intercostal muscles contract and the external intercostal muscles relax, causing ribcage to move down and inwards. Abdominal muscles contract, pushing diaphragm up. Pressure increases, volume decreases, air is forced out.
Describe type II pneumocytes
Dense, large cells (cuboidal or round) full of surfactant concentrated in the alveoli septum.
Diffusion
Movement of gas from high to low concentration gradient (down conc. grad.) which makes ventilation like actually useful
Function of type II pneumocytes
Secrete surfactant on inner surface of alveolus for moisture to:
1. Aid diffusion of gases
2. Prevent walls from sticking together and thus collapsing
They also
* Divide to form type I pneumocytes in case of damage to epithelium
What happens in emphysema
Tobacco gets into lungs. Leukocytes release elastase which breaks down the connective tissue - protein elastin - in lungs. Loses lung elasticity in alveoli and in bronchiol causes collapse as they are not turgid anymore. When person inhales again, the air going in causes the already air-filled alveoli to forcefully expand, destroying the alveolar membrane (gas exchange medium). Large air pockets in lungs.
Define emphysema
Disease which causes inflammation of alveoli. Affects area to volume ratio.
Emphysema treatment
Stop smoking lmao. Oxygen therapies. Bronchodilators.
Spirometer
Instrument to measure volume of air entering and leaving lungs
Tidal volume
Volume of air inspired or expired in a single breath during regular breathing
Explain process of gas exchange in alveoli
- Oxygen diffuses into blood, carbon dioxide diffuses out of blood.
- Air in the alveolus is higher in Oxygen.
- This causes a concentration gradient which provokes diffusion.
- Concentration gradient is maintained by blood flow.
- Large surface area created by many alveoli for more efficient diffusion
- Rich supply of capillaries allows efficient exchange.
- Type I pneumocytes thin, more permeable, which makes diffusion faster.
What does surfactant do
- Reduces surface tension which prevents walls from sticking together and collapsing
- Allows more efficient gas exchange by providing medium
+ kills or prohibits dissemination of pathogens
Trachea adaptations
- Rings of cartilage which help support its shape (stays open but still flexible)
- strengthened by cartilage
- layer of smooth muscle that contracts or relaxes to change diameter of airway
- lined with ciliated epithelium to remove particles trapped in mucus that entered airway (bronchi too)
adaptations of mammalian lungs
- Alveoli (lots) have large surface area to ensure efficient gas exchange.
- Bronchioles ensure even distribution of alveoli throughout lungs
- Alveoli surrounded by clusters of capillary beds, increased surface area for diffusion of gas - maintains concentration gradient.
- Surfactant lowers surface tension
where are stomata mostly found
lower epidermis
What does potometer measure?
Rate of water uptake by a plant
How does bubble potometer work?
Measures movement of air bubble along a water-filled tube as water is drawn up by the shoot as plant transpirates
How does mass potometer work?
Measures loss of mass of water in water-filled tube as plant draws it up and transpirates
What does humidity do to transpiration?
As humidity increases, transpiration decreases. Air outside of leaf is saturated with water molecules: there is no concentration gradient. Equilibrium may be reached as levels of water vapour inside/outside are the same, net loss of water is zero.
What does temperature do to transpiration?
As temperature increases, transpiration increases until it DROPS. Higher temperature elevates kinetic energy of particles, making them evaporate quicker. Eventually, stomata close to prevent excess water loss, causing a dramatic drop in transpiration rate.
What does air movement do to transpiration?
As air movement increases, transpiration increases. Still air causes bundles of water vapour to form around stomata, meaning no concentration gradient. Air movement takes those bundles away, causing concentration gradient to go up and transpiration to increase.
