Module 3 - Specialized exchange surfaces Flashcards
1
Q
How does a large surface area provide a good exchange surface?
A
- larger SA = more substances can cross in a given time
2
Q
How does a thin exchange surface provide a good exchange surface?
A
- the shorter the distance for a substance to diffuse the less time it takes to travel
3
Q
Why do multicellular organisms need specialized exchange surfaces but single-celled organisms don’t?
A
- single-celled organisms can exchange materials as they have:
- large SA: V ratio
- CO2 produced is low
- metabolic activity is low therefore need low levels of O2
- multicellular organisms are the opposite:
- high metabolic rate
- small SA:V ratio
4
Q
What are the 3 main features of an efficient exchange surface?
A
- increased surface area
- thin layer
- good blood supply/ ventilation to maintain good gradient
5
Q
How does increased SA aid diffusion?
A
- larger SA: V ratio
- bigger area for exchange
6
Q
How do thin layers aid diffusion?
A
- reduces diffusion distance
7
Q
How does a good blood supply aid diffusion?
A
- increases concentration gradient
- substances constantly delivered and removed
8
Q
Describe the structure of the trachea
A
- supported by incomplete rings of strong flexible cartilage which supports the structure
- lined with ciliated epithelium which uses synchronised to move bacteria out of the lungs to the throat
- lined with goblet cells which produce mucus to trap bacteria
- smooth muscle and elastic fibers
9
Q
Describe the structure of the bronchiole
A
- smooth muscle contracts to constrict airways to control airflow
- elastic fibers
- ciliated epithelium
- goblet cells
10
Q
Describe the structure of the alveoli
A
- layer of thin flattened epithelial cells which results in a short diffusion pathway
- elastin + collagen allow for stretch and recoil
- surrounded by capillaries which results in a good blood supply
- they are elastic so recoil to repel air during ventilation
11
Q
What happens in the alveoli?
A
- main gas exchange surfaces
12
Q
What is the purpose of cartilage in the trachea?
A
- prevents it from collapsing on itself
13
Q
What is ventilation?
A
- movement of air into and out of lungs
14
Q
What happens during inspiration?
A
- diaphragm contracts, flattens + lowers
- external intercostal muscles contract so the rib cage moves upwards and outwards
- the volume of the thorax increases so the pressure in the thorax decreases
- pressure in the thorax is lower than the atmospheric pressure so air is drawn into the lungs
15
Q
What happens during expiration?
A
- diaphragm relaxes, and moves up into the dome shape
- external intercostal muscles relax so the rib cage moves downwards and inwards
- the volume of the thorax decreases so the pressure in the thorax increases
- pressure in the thorax higher than atmospheric pressure so air moves out of the lungs
