What does the nasal cavity control and what are 4 adaptations?
Temperature and humidity of air.
- Large surface area
- good blood supply
- hairy lining that protects the lungs
- moist surfaces that increase humidity and reduce evaporation
How do incomplete rings of cartilage support the lungs and why are they incomplete?
They stop the lungs from collapsing.
So food can move down the oesophagus behind the trachea.
What is the function of goblet cells?
Secrete mucus to trap dust and bacteria so that cilia can push it out of the lungs to the throat.
How do the bronchioles control how much air reaches the lungs?
Made of smooth muscle tissue that closes the bronchioles when it contracts and opens them when it relaxes.
What are alveoli made up of?
Thin layers of epithelial cells, collagen and elastic fibres, which allow the alveoli to stretch when air is drawn into them
What is elastic recoil?
When the alveoli return to resting size, they help to squeeze air out.
4 adaptations of the alveoli
- Large surface area (300-500m per adult lung)
- thin layers (one epithelial cell thick)
- good blood supply (network of capillaries)
- good ventilation (steep gradient)
What happens during inspiration?
- Diaphragm contracts and flattens,
- Intercostal muscles contract, rib cage moves up and out.
- volume and pressure in thorax increases
What happens during expiration?
- Diaphragm relaxes, moves up and is dome shaped.
- Intercostal muscles relax, rib cage moves down and in
- volume and pressure in thorax decreases
What is the function of sphincters in insects ?
Open and close spiracles to minimise water loss.
What is a tracheole?
single elongated cells that are freely permeable and are spread through the tissue of the insect.
What does tracheal fluid limit in diffusion and what happens to counteract this?
Limits penetration in diffusion.
When oxygen demands are high, and lactic acid build up results in water moving out of the tracheoles by osmosis, which exposes more surface area for gas exchange
How does mechanical ventilation occur?
Air is pumped into the system by muscular pumping movements of the thorax/abdomen. The volume of the body changes, so the pressure in the tracheoles change. Air is drawn in or forced our as pressure changes
What do collapsible enlarged tracheae or air sacs do?
Used to increase the amount of air moved through the exchange system. They are inflated by ventilating movements of the thorax and abdomen.
How does water flow over the gills?
- Mouth opens, buccal cavity lowers = increased volume of buccal cavity/pressure decreases
- water moves into buccal cavity
- opercular valve is shut, opercular cavity expands.
- pressure decreases in opercular cavity.
- buccal cavity moves up, pressure is increased = water moves over gills.
Two extra adaptations of the gills
Overlapping gill filaments - increase resistance to water flow =more time for gas exchange to take place.
Countercurrent exchange system - water and blood flow in opposite directions = steep concentration gradient = more gas exchange
