7.1 - Specialised Exchange Surfaces + Features of the Mamalian Gaseous Exchange Flashcards
Why do multicellular organisms require specialised gas exchange surfaces?
Their smaller SA: V ratio means they have a longer diffusion distance
Name 4 features of an efficient gas exchange surface
- Large surface area
- Thin / short distance
- Steep concentration gradient - delivery of oxygen poor blood and removal of oxygen rich blood via the capillaries maintains a steep concentration gradient
- Lungs are surrounded by the diaphragm and intercostal muscles- maintain concentration gradient, ventilation occurs , delivery/ removal of oxygen and carbon dioxide
Describe the trachea and its function in the mammalian gaseous exchange system
• wide tube supported by C- shaped cartilage to keep the air passage open during pressure changes
• lined by ciliated epithelium cells which move mucus produced by goblet cells towards the throat to be swallowed preventing lung infections
• carries air to the bronchi
Describe the bronchi and their function in the mammalian Gaseous Exchange
• supported by rings of cartilage and are lined by ciliated epithelium cells and goblet cells
• narrower and there are two
• allow passage of air into the bronchioles
Describe the bronchioles and their function in the mammalian gaseous exchange system
• narrower than the bronchi
• do not require to be open by a cartilage
• have smooth muscle and elastic fibres
• allow passage of air into the alveoli
Describe the alveoli and their function in the mammalian gaseous exchange system
• lined with epithelium cells
• site of gaseous exchange
• walls are only one cell thick
• contain a network of capillaries
• facilities gas diffusion
• have elastic tissues which allow the alveoli to stretch as air is drawn in and return to resting size to help squeeze the air out - elastic recoil
Explain the process of inspiration
• external intercostal muscles contract - pulling the ribs up and out
• diaphragm contracts and flattens
• volume of the thorax increases
• air pressure outside the lungs is higher than the air pressure inside
• air moves into rebalance
Explain the process of expiration
• external intercostal muscles relax - bringing the ribs down and in
• diaphragm relaxes and domes upwards
• volume of the thorax decreases
• air pressure inside the lungs is therefore higher than the air pressure outside
• air moves out to rebalance
Explain how a spirometer works
• used to measure lung volume
• person breathes into an air tight chamber which leaves a trace on a graph which shows the volume of the breaths
Define vital capacity
Maximum volume of air that can be taken in or expelled from the lungs in one breath
Define tidal volume
The volume of air we breathe in and out during each breath at rest
Define breathing rate
The number of breaths we take per minute
What are the functions of cilliated epithelium cells?
•Moving substances across the surface of a tissue
• have cilia which beat in a coordinated way to shift material along the surface of the epithelium tissue
• trap bacteria and mucus and transport it away and towards the throat to be swallowed
What is the function of goblet cells?
Secrete mucus
- helps to trap dust , dirt and microorganisms preventing them from entering the vital organs where they may cause a infection
What is the function of squamous epithelium?
• provide a surface covering or outer layer
• found on organs and structures eg. Blood vessels and alveoli
