Chapter 10: Respiration

Students should be able to:

(a) Identify on diagrams and name the larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries

(b) State the characteristics of, and describe the role of, the exchange surface of the alveoli in gaseous exchange

(c) Describe the removal of carbon dioxide from the lungs, including the role of the carbonic anhydrase enzyme

(d) Describe the role of cilia, diaphragm, ribs and intercostal muscles in breathing

(e) Describe the effect of tobacco smoke and its major toxic components - nicotine, tar and carbon monoxide, on health

(f) Define and state the equation, in words and symbols, for aerobic respiration in human

(g) Define and state the equation, in words only, for anaerobic respiration in human

(h) Describe the effect of lactic acid in muscles during exercise

10.1 Aerobic Respiration

10.1.1 Definition Breakdown of food substances in the presence of oxygen with the

release of a large amount of energy, with CO2 and water as the waste product

Reaction take place in mitochondria, with help of enzymes (Tissue Respiration)

10.1.2 Equation C6H12O6 + 6O2 6CO2 + 6H2O + Energy Glucose + Oxygen carbon dioxide + water + energy

10.1.3 Uses of energy in the human body Processes that require energy

o Production of proteinso Heartbeat, Muscular contractionso Active transporto Regulation of body temperature

10.2 Anaerobic Respiration

1

10.2.1 Definition Breakdown of food substances in the absence of oxygen with the

release of a small amount of energy, with CO2 and ethanol as the waste product

Less efficient than aerobic respiration due to small energy released Certain microorganisms could depend entirely on it due to low

energy requirement to live

10.2.2 Equation C6H12O6 2C2H5OH + 2CO2 + Energy Glucose Ethanol + carbon dioxide + small amount of energy

Substantial amount of energy is still trapped within the chemical bonds of ethanol if ethanol is further broken down, more energy could be released

10.2.3 Anaerobic respiration in Man

Glucose Lactic acid + small amount of energy

Occurs when maximum aerobic respiration cannot release energy fast enough anaerobic respiration produce extra energy to meet the demand

Lactic acid builds up in the muscles causes fatigue Muscles incur an oxygen debt due to insufficient oxygen during

the course of vigorous contraction Lactic acid formation cause of muscular pain Normally goes on for short period of time Lactic acid is then removed to the liver during rest period

10.3 Gaseous Exchange in Man

10.3.1 Composition of inspired air (breathed in) and expired air (out) Inspired air Expired air

O2 21% 16.4%CO2 0.03% 4%N2 78% 78%

Water vapour Depends on external conditions SaturatedTemperature Depends on external conditions Body temperatureDust particles Depends on external conditions Very little

10.3.2 Respiratory System in Man

2

Removed during rest

Some are oxidized release energy

Specialized Breathing movements enable rapid exchange of gases

10.3.3 Gaseous exchange surface of alveoli (External Respiration)

3

Large surface area of alveoli provide large SA for gaseous exchange

10.3.4 Breathing mechanisms

4

O2

CO2

Blood enters lungs (low O2, high CO2)Concentration gradient builds up from

1. Continuous flow of blood2. Breathing air in and out of

alveoli

High O2

Low CO2

O2, and CO2 diffuses across capillariesRapid diffusion helped by

1. One cell thick alveolar walls2. Presence of moisture on the

alveolar wall to enable O2 to dissolve in it

1. Hb + O2 HBO8

2. Reaction is reversible3. Direction is determined by O2

concentration

CO2 dissolve in plasma carried as hydrogen carbonate (HCO3

-) ions to lungs

In lungs, HCO3- CO2

CO2 diffuses out of capillaries into alveolar cavity

Water vapour evaporates from alveolar walls

Heat escapes into the alveolar air

Air enters from nostrils (lined with mucous membrane)

During Inhalation (Inspiration) External intercostals muscles contract

5

Secrete mucus traps dust particles

Sweeps particles up the bronchi trachea larynx

Internal intercostals muscles relax

During Exhalation (Expiration) External intercostals muscles relax Internal intercostals muscles contract

10.4 Effect of tobacco smoke on health

Chemical Properties Effects on body

6

Ribs swing upwards and outwards Sternum moves up Diaphragm contracts and flattens Thoracic cavity enlarges Air pressure in alveoli cause lungs to

expand Expansion of lungs reduce air

pressure in alveoli Alveolar air pressure < Atmospheric

air pressure Air rushes into lungs until air

pressure in lungs = atmospheric air pressure

Short pause for gaseous exchange

Ribs swing downwards and inwards Sternum moves down Diaphragm relax and arches upwards Thoracic cavity decreases Ribs and sternum press on the lungs Air is compressed and forced out

sNicotine Addictive drug

Causes release of hormone adrenaline

Makes blood clot easily

Increases heartbeat and blood pressure

Increased risk of blood clots in blood vessels

Carbon Monoxide

Haemoglobin + CO Carboxyhaemoglobin

Formation of carboxyhaemoglobin reduces the efficiency of oxygen transport of RBC

Increase rate of fatty deposits on inner arterial wall (atherosclerosis)

Damages lining of blood vessels

Can cause death if conc. of CO > 1%

Increased risk of atherosclerosis

Increased risk of thrombosis

Tar Contains carcinogenic chemicals (cancer-causing) which cause uncontrolled cell division

Paralyze the cilia

Blockage of alveoli and reduction in gas exchange efficiency

Dust particles trapped in mucus lining the airways cannot be removed

Irritant particles

Paralyze cilia lining air passages

Increased risk of chronic bronchitis and emphysema

10.4.1 Chronic Bronchitis Signs:

o Epithelium lining the airway becomes inflamedo Excessive mucus is secreted by the epitheliumo Cilia on the epithelium are paralyzed. Mucus and dust cannot be

removedo Airway become blocked breathing becomes difficulto Person has to cough persistently to clear his airway to breathe

increases chances of lung infections

10.4.2 Emphysema Signs:

o Persistent coughing cause walls between alveoli to break down

7

o SA: Vol ratio decreaseso Lungs become inflated with airo Lungs lose their elasticityo Breathing becomes difficult person wheezes and suffer from

breathlessness

10.4.3 Lung Cancer Risk of getting lung cancer increases the more a person smokes

o Tar causes cells to divide uncontrollablyo Uncontrolled cell division leads to lumps of tissues being formed

Risks of getting other cancers are also greatly increased

8