M3 Gas Exchange Flashcards
As the size of an object increases, the the volume increases and the SA:Vol ratio….
Decreases
Why do some multicellular organisms need specialized exchange systems?
- Low SA:Vol ratio
- Some cells are deep within the body (large diffusion distance)
- Need a constant supply of glucose and oxygen due to high metabolic rate
- Skin/surface tissue impermeable
Describe the general structure of the gas exchange system of insects
Spiracles –> Trachea –> Tracheoles –> Respiring tissue
Each segment of the abdomen has a pair of spiracles. The spiracles can be closed by valves to reduce water loss.
Trachea are supported by chitin strengthening rings.
How do insects maintain a concentration gradient?
Oxygen is delivered straight to tissues that are respiring.
What happens in insects to speed up the movement of oxygen to their tissues?
- Pumping of abdomens using muscles.
What happens in insects where air flow is unidirectional? And not unidirectional?
Front spiracles open to allow air to enter. These then close and the back ones open to allow air out.
All spiracles are open at the same time.
How are insects designed to increase the rate of diffusion?
The ends of tracheoles are filled with water:
- anaerobic respiration produces soluble lactic acid, lowering the water potential of cells.
- this causes water to move from the tracheoles into cells by osmosis.
- this decreases the volume of water in the tracheoles, drawing air further in.
- This increases the rate of diffusion as diffusion is through a gas rather than liquid.
Describe the structures involved in gas exchange in fish.
Operculum –> Gill arch–> filaments –> lamellae
filaments - high SA
llamellae are only a few cells thick and contain blood capillaries - high SA, short diffusion distance.
Why do fish die when out of water?
Gills are so thin that they cannot support themselves without water. Out of water, they collapse, decreasing SA and the fish suffocates.
Explain the counter-current mechanism in fish gas exchange.
Blood flows in the opposite direction to the water. It always flows next to water that has more oxygen. This way the blood is absorbing more and more oxygen as it moves along and a concentration gradient is always maintained. This maximizes the amount of oxygen diffused into the blood stream.
Describe the general structure of the human gas exchange system and it’s specific components and their function.
Mouth –> trachea –> bronchi –> bronchioles –> Alveoli
The system also contains ribs, pleural membranes and intercostal muscles in the thorax, and the diaphragm in the abdomen.
- Alveoli are lined with epithelial cells - site of gas exchange.
- Bronchioles are able to constrict to control air movement.
- Bronchi have cartilage, cilia and goblet cells.
- Trachea is supported by rings of cartilage, and has cilia and goblet cells - to produce mucus and trap dirt particles. Cilia to waft trapped dirt upwards.
- Intercostal muscles - external and internal between ribs, used to move ribs for ventilation.
- Ribcage protects lungs and are moved by intercostal muscles for ventilation.
- Diaphragm - muscular sheet separating abdomen and thorax and used for ventilation.
What is the function of the C shaped cartilage in the trachea? Why is it C shaped? Why do bronchioles not have cartalage?
To provide support, preventing it from collapsing when air pressure falls.
To allow food to be swallowed in the oesophagus.
So they can constrict to control airflow.
What is the main cause of air being forced out of the lungs?
Recoil of elastic tissue. Muscles are used increasingly with strenuous activity.
What occurs in inspiration?
Air flows in, down a pressure gradient.
External intercostal muscles contract.
Internal intercostal muscles relax.
Diaphragm contracts and flattens.
Volume of thorax increases.
Pressure decreases.
What occurs in expiration?
Air flows out, down a pressure gradient.
External intercostal muscles relax.
Internal intercostal muscles contract.
Diaphragm relaxes.
Volume of thorax decreases.
Pressure increases.
