Gas Exchange Flashcards
What are the 6 features of a gas exchange system?
- Large SA:V ratio
- Thin/short diffusion path
- Permeable
- Moist
- Linked to a transport system
- Maintaining a diffusion gradient through a system to deliver and take away gases and also create currents along the surface
Why do insects have a high demand for oxygen?
Because they’re very active in flight/on land
What is an insect’s exoskeleton made out of?
A polysaccharide called chitin
Why is an exoskeleton needed by insects?
To reduce loss of gases and water
What are the tracheae?
A series of fine tubes that carry gases to and from active organs in the body of an insect
What role does chitin play in the tracheae?
Rings of chitin support the tubes and prevent them collapsing under high pressure but allow the tubes to be flexible
What are tracheoles?
Small tubes which branch off from the main trachea and lead directly into the tissues
How are the tracheoles and tracheae different?
The tracheoles aren’t supported by rings of chitin
What are spiracles?
Valves found in the thorax and abdomen of insects where gas exchange takes placet
How are the spiracles opened and closed?
Small sphincter muscles
Why are there small hairs in the spiracles?
To prevent entry of small particles which can block the spiracles
By what process does gas exchange occur in the trachea?
Diffusion
Explain how diffusion works in the tracheoles?
Oxygen diffuses into trachea through spiracles
Trachea transport it to tracheoles
Tracheoles penetrating the tissues are full of a watery fluid from the hypotonic cytoplasm of the cells
O2 diffuses out of the tracheoles bc the partial pressure in the tracheoles is higher
CO2 diffuses into tracheoles
How and why does an increased rate of metabolism affect osmotic potential?
It reduces the osmotic potential of the cells due to the increase of lactic acid.
How have insets evolved to increase oxygen supply for flight?
Ventilation mechanism - thorax and abdomen pump and move more air through the tubes through compressing and opening the tubes (increased by opening and closing certain spiracles)
Air sacs - contain reservoir of air to be pumped into trachaea when O2 demand is high
What are the problems of aquatic animals for gas exchange?
- 25x less O2 in water than air and that gets less as temp. increases
- Water is 800x denser than air to its harder to move
How do fishes reduce gas loss?
By having impermeable skin
What are features of the gills?
Large SA:V ratio to allow more diffusion
Permeable membranes
Thin
Good vascular supply
Explain the structure of a gill
A gill has two rows of gill filaments arranged in a v shape on a gill arch. Along the gill arch are gill lamellae/filaments which have small gill plates on them and capillaries
What is the operculum?
A flap covering the gills and the gill cavity
Explain how inspiration happens in a fish
Mouth opens and floor of the buccal cavity lowers. Water flows in and the buccal cavity floor lifts so the volume decreases and pressure increases.
Explain how expiration happens in a fish
Muscles in the operculum contract and bulge out so volume of operculum cavity increases so pressure decreases so water is drawn in and over the gills. Mouth closes and buccal cavity raises so water is forced over the gills. Pressure behind operculum increases until pressure inside > outside so water is forced out.
How are gill filament and plates adapted for diffusion?
Thin and have large surface area
Explain the counter current system
Water passes over the gills and in the opposite direction to the blood flow which maintains a high concentration gradient so 80-90% of oxygen diffuses into capillaries rather than 50%.
What are afferent blood vessels?
Carry deoxygenated blood to the capillaries and to the secondary lamellae
What are efferent blood vessels?
Carry oxygenated blood from the capillaries to the gill arch
What are the lungs?
The organs of gas exchange in mammals
Where are the lungs found?
In the thorax
What is the buccal cavity?
The area in the mouth
What is the thorax?
The rib cage, intercostal muscles and the diaphragm
What is the diaphragm?
A thick sheet of muscle which separates the thorax and abdomen
What are pleural membranes?
These line the thorax and the lung and they secrete and maintain pleural fluid which is a lubricating fluid derived from blood plasma that protects the lungs from friction during breathing
Summarise the passageway of air through the body
Nasal/oral cavity - pharynx - epiglottis/glottis - larynx - trachea - bronchi - bronchioles - alveoli
What is the pharynx?
A passageway from the oral and nasal cavities to the oesophagus and larynx
What is the trachea?
The windpipe which transfers air to and from the lungs to the mouth/nose
What is the larynx?
The voice box which houses the vocal cords
What is the glottis?
The slit to get into the larynx
What is the epiglottis?
The cartilaginous flap called the epiglottis
What is the purpose of the glottis and the epiglottis?
To stop food from entering the trachea
Describe and explain the structure of the trachea
Runs along the oeophagus and has incomplete cartilage rings to prevent collapse under pressure from balls of food in the oespohagus
Describe and explain the structure of the bronchi/bronchioles
Made of smooth muscle and supported by incomplete cartilaginous rings to prevent collapse due to sudden pressure drop from breathing in
How are the trachea and bronchi similar in structure?
Both have cartilage rings and both have ciliated epithelia on the inner surface. They have a rhythmic wave-like movement
What are goblet cells and where are they found?
In the trachea and bronchi and they secrete sticky mucus containing glycoproteins and lysosomes.
What is the purpose of goblet cells?
Mucus produced prevents dehydration and traps microbes and dust which are then moved away from the lungs by the cilia
What are the differences in cartilage bands between the trachea and bronchi?
In trachea bands are c shaped so food can be passed down the oesophagus
In bronchi it’s in irregular blocks with loose tissue which forms smooth muscle
What does the smooth muscle on the bronchi do?
Contracts and relaxes to alter the diameter of the bronchi to control how much air is coming in/out. Also has elastic fibres which recoils during exhalation
Explain inspiration in the lungs
External intercostal muscles contract which pulls ribcage upwards and outwards. Diaphragm contracts and flattens. Volume of thorax and lungs and increases thus reducing so pressure so air is drawn in, travelling down the concentration
Explain (relaxed) expiration in the lungs
External intercostal muscles relax and the ribcage collapses under its own weight. Diaphragm relaxes and gut pressure pushes it back to its domed shape. Elastic recoil of lungs. Volume of thorax and lungs decreases so pressure increases and air is forced out
Explain (forced) expiration in the lungs
Internal intercostal muscles contract which pulls ribcage down and in. Abdominal muscles contract and pull diaphragm upwards
When does forced expiration occur?
During exercise or singing
Explain the structure of the alveoli
Made of squamous epithelium surrounded by blood capillaries
What is squamous epithilium?
A single layer of flattened cells forms an outer covering
What is endothelium?
A single layer of cells in the blood capillaries forming an inner layer.
Name four features of the alveoli
Elastic fibres which stretch during inhalation and recoil during exhalation
White blood cells to remove pathogens and dust not trapped by ciliated epithelium
Moist film into which gases dissolve before they diffuse
Cover an area of 70m^2
Why don’t tracheoles have chitin?
To allow them to be permeable to gases
