7.1-4 Exchange and transport Flashcards
What is the need for specialised exchange surfaces?
- size of the organisms
- surface area to volume ratio decreases
Why can substances easily enter cells of single celled organisms?
- distance that needs to be crossed over is short
Why is the distance for substances to cross larger in larger organisms?
- a lower surface area to
volume ratio
What do multicellular organisms require?
- specialised exchange
surfaces for efficient gas exchange of carbon dioxide and oxygen
What is a feature of efficient exchange surfaces?
- large surface area
-for instance the root
hair cells or folded membranes, such as those of the mitochondria
What does an efficient exchange surface require?
- should be thin to ensure that the distance that needs to be crossed by the substance is short
- a good blood supply/ventilation to
maintain a steep gradient, for example that of the alveoli
What are the lungs?
- a pair of structures with a larger surface area located in the chest cavity with the ability to inflate
- surrounded by the rib cage as a form of protection
What is released between the rib cage and what does it help with?
- a lubricating substance is secreted to reduce friction during inflation and deflation
What are placed between the ribs?
- external and internal intercostal muscles
What do the intercostal muscles do?
- contract to raise and lower the ribcage
What does the diaphragm do?
- separates the lungs and from abdomen area
How does air enter the first half of the respiratory system and what are they adapted for?
- nose
- along the trachea
- bronchi
- bronchioles
- to their role in enabling passage of air into the lungs
Where does gaseous exchange take place?
- in the walls of the alveoli which are tiny air sacs filled with air
Which three structures allow air in and out of the lungs?
- trachea
- bronchi
- bronchioles
How are the airways held open and how is this different in the trachea?
- with the help of rings of cartilage
- incomplete in the trachea to allow passage of food down the oesophagus behind the trachea
Which two structures are similar yet different and what reasons?
- trachea and bronchi
- similar in structure
- different in size (bronchi smaller)
What is the structure of trachea and bronchi like?
- composed of several layers which together make up a thick wall
- the wall is mostly composed of cartilage in the form of C rings
What is the inside surface of cartilage like?
- a layer of glandular and connective tissue, elastic fibres, smooth muscle and blood vessels
- referred to as ‘loose tissue’
What is the inner lining of an epithelial layer made out of?
- ciliated epithelium and goblet cells
How are bronchioles different to bronchi?
- narrower
- larger bronchioles contain cartilage
- wall is made out of smooth muscle and elastic fibres
- smallest bronchioles have alveoli clusters at the ends