1. RESPIRATORY SYSTEM
Topic 6.4
IB Biology
Miss Werba

2. NERVOUS & ENDOCRINE SYSTEMS
TOPIC 6 - PHYSIOLOGY
6.1
DIGESTIVE SYSTEM
6.2
CIRCULATORY SYSTEM
6.3
IMMUNE SYSTEM
6.4
RESPIRATORY SYSTEM
6.5
NERVOUS & ENDOCRINE SYSTEMS
6.6 REPRODUCTIVE SYSTEM
J WERBA – IB BIOLOGY 2

3. THINGS TO COVER Ventilation, gas exchange and cell respiration
Need for ventilation system
Features of alveoli adapted for gas exchange
Structure of ventilation system
Mechanism of ventilation of the lungs
J WERBA – IB BIOLOGY 3

4. RESPIRATORY SYSTEM TERMS
6.4.1
RESPIRATORY SYSTEM TERMS
Ventilation:
The exchange of air between the lungs & the environment (via act of breathing)
Gas Exchange:
The exchange of O2 and CO2 between the alveoli & bloodstream
Cell Respiration:
Release of energy from the breakdown of organic compounds (aerobic = O2)
J WERBA – IB BIOLOGY 4

5. THE NEED FOR VENTILATION
6.4.2
THE NEED FOR VENTILATION
Maintains a concentration gradient of gases between alveoli and the blood
The body needs O2 for cell respiration and produces CO2 as waste, which must be removed
The alveoli must have high levels of O2 and low levels of CO2 to promote diffusion of gases (O2 in ; CO2 out)
The ventilation system removes CO2 and replenishes O2 from the atmosphere to maintain the gradient
It also has a large surface area
J WERBA – IB BIOLOGY 5

6. THE RESPIRATORY SYSTEM: Command terms: DRAW and LABEL
6.4.4
THE RESPIRATORY SYSTEM: Command terms: DRAW and LABEL
nasal cavity
buccal cavity
pharynx
epiglottis
oesophagus
larynx
ring of cartilage
trachea
R. bronchus
cut rib
L. lung
bronchioles
external intercostal muscles
pleural cavity
inner pleural membrane
internal intercostal muscles
outer pleural membrane
abdominal cavity
diaphragm
capillary network
alveoli
Ref: Rowland p205
J WERBA – IB BIOLOGY 6

7. THE RESPIRATORY SYSTEM: Command terms: DRAW and LABEL
6.4.4
THE RESPIRATORY SYSTEM: Command terms: DRAW and LABEL
J WERBA – IB BIOLOGY 7

8. 6.4.3
THE ALVEOLI
J WERBA – IB BIOLOGY 8

9. 6.4.3
THE ALVEOLI
There are a number of features of alveoli that make them highly efficient in their job of gas exchange:
They have a large surface area:
there are hundreds of millions of alveoli
huge overall surface area:volume ratio
They have very thin walls:
walls only a single layer of flattened cells
creates short diffusion distances for gases
J WERBA – IB BIOLOGY 9

10. THE ALVEOLI The walls are kept moist: alveolus walls secrete a fluid
6.4.3
THE ALVEOLI
The walls are kept moist:
alveolus walls secrete a fluid
keeps the inner surface moist and allows gases to dissolve
They have a very good blood supply:
a dense capillary network surrounds the alveoli
brings deoxygenated blood from the heart
J WERBA – IB BIOLOGY 10

11. THE ALVEOLI Remember: TRIM
6.4.3
THE ALVEOLI
Remember: TRIM
Thin lining (single cell layer = less diffusion)
Rich capillary network (for gas exchange)
Increased SA:Vol ratio (↑ gas exchange)
Moist (dissolves gases; prevents collapsing)
J WERBA – IB BIOLOGY 11

12. BREATHING INHALATION EXHALATION diaphragm contracts and flattens
6.4.5
BREATHING
INHALATION
EXHALATION
diaphragm contracts and flattens
diaphragm relaxes and curves upwards
external intercostal muscles contract, raising ribs
internal intercostal muscles contract, lowering ribs
volume in thoracic cavity is increased (pressure decreased)
volume in thoracic cavity is decreased (pressure increased)
pressure in lungs drops below atmospheric pressure
pressure in lungs rises above atmospheric pressure
air flows into lungs along a pressure gradient
air flows out of lungs along a pressure gradient
J WERBA – IB BIOLOGY 12

13. Sample questions Q1 What is the function of the structure labelled X?
Gas exchange
Ventilation
Respiration
Inspiration
J WERBA – IB BIOLOGY 13

14. Sample questions Q2
Describe the need for a ventilation system in humans. [2] Q3
Describe the structure of the ventilation system, including the alveoli. [8]
J WERBA – IB BIOLOGY 14

15. Sample questions A1 A A2
most cellular respiration is aerobic/requires oxygen / produces carbon dioxide;
ventilation system exchanges gases between inhaled air and lungs/blood stream;
ventilation system maintains high concentration gradient of gases in alveoli/lungs;
J WERBA – IB BIOLOGY 15

16. Sample questions A3 ventilation occurs within the lungs;
trachea divides to form two bronchi;
bronchi divide to form bronchioles;
several divisions of bronchioles;
alveoli connected to bronchioles;
trachea/bronchi/bronchioles/airways lined with cilia/ciliated epithelium;
diaphragm and intercostal muscles;
trachea/bronchi have rings/c-shaped pieces of cartilage;
alveolus is an (air) sac;
very small / diameter is (about) 100 μm;
many alveoli so large total surface area;
wall of alveolus is a single layer of cells;
cells in alveolus wall are very thin;
surrounded by a network of capillaries;
some (larger) cells in the wall secrete fluid/surfactant/natural detergent;
Award any of the above points if clearly drawn in a diagram.
J WERBA – IB BIOLOGY 16