Transcript Diaphragm (sheet of muscle)

Human Breathing
Chapter 31
Human Respiratory System:
• Consists of a pair of lungs and a series of tubes
• Lungs located in the thorax (chest)
• Diaphragm (sheet of muscle) forms the floor of the
thorax
• Ribs (protective cage) and intercostal muscles
(attached between ribs) form the walls of the thorax
Parts of the Respiratory System:
PART
Nostrils
Nose
Pharynx (throat)
Epiglottis
Glottis
FUNCTION
Allows air to enter the
nose
Warms, filters &
moistens air
Connects nose & mouth
to larynx
Found in pharynx
Stops food/drink
entering trachea
(windpipe)
Opening to larynx
Larynx (Vociebox)
Contains vocal cords
Trachea ( windpipe) Allows air to pass to
lungs
*Made of muscle &
elastic fibres with
incomplete rings of
cartilage
Cartilage
Strong material which
keeps trachea and
bronchi open
Bronchi
Transport air from
trachea into lungs
Bronchiole
Alveoli
About 1 million per lung
Transport air into the
alveoli
Thin walled, moist,
surrounded by capillaries.
Site of gas exchange,
provides a large surface
area (700 million in 2
lungs) for gaseous
exchange
Lung
Takes in O2 and gets rid
of CO2
Pleural membranes
Allow friction free
movement of lungs
Gas Exchange
Remember:
Diffusion is the movement of molecules
from a region of high concentration to a
region of lower concentration
Gas Exchange in an Alveolus
Air enters the nose travels down the windpipe, the
bronchus, and the bronchioles to the alveoli
Oxygen diffuses from the alveoli to the red blood cells in
the blood.
At the same time carbon dioxide and water vapour
diffuse from the blood (plasma) to the alveoli
Note: in both cases CO2 and O2 are moving from areas of
high concentration to low concentration.
Gas Exchange in Alveolus and Body Cell
Oxygen, carbon dioxide and water vapour diffuse in the
reverse direction in the cells of the body:
- Oxygen diffuses from the blood to the body cells
- Carbon dioxide and water vapour diffuse out of
the body cells and into the blood.
(Note: cytoplasm of body cells has higher conc. of
CO2 & H2O than blood)
Adaptations to improve Gas Exchange
Alveoli:
• have thin walls
• are very numerous
• are moist
Capillaries:
• have thin walls
• are numerous
Inhaled Vs. Exhaled Air
Note: - 97% oxygen transported by haemoglobin
- Carbon dioxide & water vapour transported by plasma
Mechanism of Breathing
•Breathing (ventilation) is normally an involuntary
process.
•The brain controls the rate of breathing
•This process has two stages:
- inhalation/inspiration
- exhalation/expiration
Inhalation:
 The brain sends signals to the intercostal muscles
and diaphragm to contract
 The intercostal muscles contract and cause the rib
cage to move up and out. At the same time the
diaphragm flattens downwards.
 The volume of the chest (thorax) increases, so air
pressure drops. External air pressure is now higher
than the pressure of air in the chest as a result more
air is forced into the lungs and subsequently the
alveoli.
Inhaling requires energy as it is an active process i.e.
energy required in movement of muscles
Exhalation:
 There is no message so the intercostal muscles and
diaphragm relax springing back to their original
positions:
- relaxed intercostal muscles cause rib cage to
move down and in.
- diaphragm moves up.
 Volume of the chest decreases so air pressure
increases, and air is forced out of the lungs.
Exhaling does not require energy as it is a passive process
i.e. muscles only have to relax
Effect of Exercise on Breathing Rate
Breathing
rate/min
Heart rate/min
225
Rest
Exercise
Recovery
100
175
75
125
50
75
25
5 mins
10 mins
15 mins
20 mins
Effect of Exercise on Breathing Rate
• Adult at rest breathes approx 15 times/min.
• Exercise results in increased respiration
• Brain detects increased level of exercise and so
increases breathing rate to allow for:
- increase in oxygen inhaled (respiration)
- increase in carbon dioxide exhaled (waste)
• Exhalation becomes an active process during exercise
Activity 19b: To investigate the effect of exercise
on the breathing rate
• You have a choice to complete this activity or
Activity 19a (pg. 266) – completed previously
Breathing Disorders
You are required to study 1 breathing disorder!!!
• *Asthma – inflammation & constriction of
bronchi
• Bronchitis
• Emphysema – destruction of alveoli
• TB – elasticity reduced (bacteria)
• Pneumonia – fills with fluid
Asthma:
Asthma results in the narrowing of the lower
bronchioles due to some irritant (dust mite, pollen,
cold, virus) and so the sufferer finds it difficult to
inhale enough oxygen
Symptoms:
• coughing
• wheezing
• breathlessness
• chest tightness
Causes:
• pollen
• animals
• smoke
• dust mites
• chemicals
• exercise
Prevention:
Identify triggers – avoid or remove e.g. Allergens
Treatment:
Specific drug treatments which generally cause the
bronchiole to widen e.g. Inhalers, steroids
Control Of Human Breathing
Higher Level Only
• Breathing is under
the control of the
medulla oblongata in
the brain, which is
sensitive to CO2 levels
• Nerve cells in the
medulla are
connected to the
diaphragm and
intercostal muscles
• When CO2 levels in the blood are high (as a result
of increased respiration caused by exercise), the pH of
the blood decreases
• This is detected by the brain and messages are sent
to the intercostal muscles and diaphragm and the
rate and depth of breathing is increased