The document summarizes key aspects of the respiratory system and gas exchange in three parts: 1. It describes the process of breathing, including inspiration, expiration, and the roles of the diaphragm and rib cage muscles. Gas exchange occurs through external respiration in the lungs and internal respiration in tissues. 2. It explains the human respiratory system anatomy including the nose, air passages, lungs and alveoli where gaseous exchange takes place via diffusion. 3. It covers the transport of oxygen and carbon dioxide in the blood, cellular respiration consuming oxygen to produce energy, and common respiratory diseases like pneumonia, tuberculosis, and effects of smoking.

1. UNIT 3:
RESPIRATORY SYSTEM
AND GASEOUS
EXCHANGE

2. BREATHING
• SEQUENCE OF EVENTS THAT RESULTS IN GAS EXCHANGE.
• IN TERRESTRIAL VERTEBRATES IT INCLUDES 3 STEPS:
1. VENTILATION: INSPIRATION AND EXPIRATION.
2. EXTERNAL RESPIRATION: GAS EXCHANGE BETWEEN AIR (IN
LUNGS) AND BLOOD.
BLOOD THEN TRANSPORT OXYGEN TO THE BODY TISSUE
CELLS.
3. INTERNAL RESPIRATION: GAS EXCHANGE BETWEEN BLOOD
AND TISSUE FLUID. BLOOD THEN TRANSPORTS
CARBON DIOXIDE TO THE LUNGS.

3. External
respiration
Internal
respiration
oxygenCarbon dioxide
oxygen Carbon dioxide
Alveoli filled with air (gas)
Body cells surrounded by tissue fluid
Blood – part of
circulatory system
contain red pigment
– hemoglobin, to
transport gasses
Gas exhange surface
must be:
•Moist
•Thin
•Large in relation of
size of body
Process: Diffusion of
gasses (oxygen and
carbon dioxide

4. CELLULAR RESPIRATION
• IS THE PROCESS WHEREBY AN ORGANISM USES OXYGEN AND FOOD TO PRODUCE
ENERGY (ATP) AND 2 BY PRODUCTS E.G. WATER AND CARBON DIOXIDE
• GLUCOSE + O2 ATP + H2O + CO2
THEREFORE GASEOUS EXCHANGE IS NECESSARY TO GET OXYGEN FOR CELLULAR
RESPIRATION.

5. HUMAN RESPIRATORY SYSTEM
• CONSISTS OF:
1. NOSE
2. AIR PASSAGES:
 PHARYNX
 TRACHEA
 BRONCHUS
 BRONCHIOLES
3. LUNGS – ALVEOLI

6. NOSE
• NOSE HAS A NASAL CAVITY THAT
LEADS TO THE PHARYNX.
• NASAL CAVITY IS LINED WITH CILIA
AND HAIRS AND GOBLET CELLS THAT
MAKE MUCUS (ANTI-SEPTIC AND
MOISTEN AIR)– FILTER THE AIR –
DUST, POLLEN AND OTHER FOREIGN
MATERIAL STICKS TO IT.
• 3 X TURBINATE BONES DIVIDE THE
NASAL CAVITY INTO 4 PASSAGES –
THIS ENLARGES THE SURFACE OF THE
NASAL CAVITY – FOR WARMING,
CLEANING AND MOISTEN OF AIR.
• SEVERAL SURFACE BLOOD VESSELS
HELP TO WARM AIR.

7. AIRPASSAGES
• PHARYNX – PASS AIR FORM
NOSE TO TRACHEA VIA
LARYNX.
• TRACHEA: LONG, STRAIGHT
TUBE KEPT OPEN BY C-SHAPED
CARTILAGE RINGS.
• TRACHEA – LINED WITH CILIA
AND GOBLET CELLS (MUCUS
PRODUCTION) – TRAPS
FOREIGN PARTICLES

8. LINING OF AIRPASSAGES
CILIA (SEM) TRACHEAL LINING

9. AIRPASSAGES: BRONCHI AND BRONCHIOLES
• TRACHEA DIVIDES IN A RIGHT AND
LEFT BRONCHUS – CONSIST OF C-
SHAPED CARTILAGE RINGS AND LINED
WITH GOBLET CELLS (MUCUS)
• BRONCHI BRANCH IN LUNG TO FORM
BRONCHIOLES – BRANCH FURTHER
AND CARTILAGE RINGS DISAPPEARS –
LEAD AIR TO AIR SACS OF LUNG.
Bronchiole
Left bronchus – long,
branch in 2
Right bronchus-short
Branch in 3

10. LUNGS
• RIGHT LUNG (3 LOBES -
SHORTER) AND LEFT LUNG (2
LOBES – LONGER, NARROW)
• SPONGY, ELASTIC PINK ORGAN.
• CONSISTS OF SEVERAL AIR
SACS CALLED ALVEOLI.
• ALVEOLI ARE GROUPED
TOGETHER AND FORM THE
ENDINGS OF THE
BRONCHIOLES.

11. ALVEOLI
• LINED WITH SINGLE LAYER
SQUAMOUS EPITHELIAL CELLS –
THIN EASY DIFFUSION OF GAS.
• ALVEOLI IS SURROUNDED BY A
NETWORK OF BLOOD
CAPILLARIES – GASSES DIFFUSE
INTO AND OUT OF BLOOD.
• ALVEOLI IS LINED WITH MOIST
LAYER – OXYGEN DISSOLVES IN
MOISTURE AND DIFFUSES
THROUGH ALVEOLI WALL INTO
BLOOD CAPILLARY.

12. SEM TEM
Alveoli
Pulmonary
artery
(Deoxygenated
blood)
Pulmonary vein
(Oxygenated
blood)
Diaphragm
Bronchiole
Bronchus
Trachea
Pharynx
Turbinate bones

13. BREATHING - THE PROCESS WHEREBY AIR (GASSES)
MOVE IN AND OUT OF THE BODY.
INSPIRATION
• INSPIRATION
EXPIRATION
• EXPIRATION
Diaphragm
contracts
(moves down)
Diaphragm
relaxes
(moves up)
Rib cage
expands
as rib
muscles
contract
Rib cage
gets
smaller as
rib muscles
relax
Air inhaled
Air exhaled
When pressure in
lungs decrease –
air rush in
When pressure in
lungs increase –
air is pushed out

14. TIDAL VENTILATION MECHANISM
• AIR MOVES IN AND OUT OF THE BODY VIA THE SAME ROUTE.
• ALL TERRESTRIAL VERTEBRATES DO THIS EXCEPT FOR BIRDS.
• THE LUNGS ARE NOT COMPLETELY EMPTIED DURING EACH BREATHING CYCLE.
• THE AIR ENTERING MIXES WITH USED AIR REMAINING IN THE LUNGS.

15. DETERMINING LUNG CAPACITY
• A SPYROMETER CAN BE USED TO DETERMINE HOW MUCH AIR
ENTERS THE LUNGS.
• YOUR LUNGS HAS A VOLUME OF +/- 5 LITERS.
• TIDAL VOLUME – 0,5 LITERS OF AIR THAT IS EXCHANGED DURING
NORMAL BREATHING
• VITAL CAPACITY – 3,5 LITERS OF AIR EXCHANGED DURING FORCED
BREATHING (THE FITTER YOU ARE, THE HIGHER YOUR VITAL
CAPACITY.)
• RESEDUAL AIR/VOLUME – 1,5 LITERS OF AIR THAT IS ALWAYS LEFT
IN THE LUNGS DURING BREATHING

17. RESPIRATORY CENTER
• NORMAL BREATHING RATE FOR ADULTS: 12 – 20
VENTILATIONS PER MINUTE.
• RESPIRATORY CENTER IN THE MEDULLA OBLONGATA
OF THE BRAIN CONTROLS BREATHING.
• THE RESPIRATORY CENTER SEND IMPULSES THROUGH
THE PHRENIC NERVE TO THE DIAPHRAGM AND
THROUGH THE INTERCOSTAL NERVE TO THE
INTERCOSTAL MUSCLES TO EITHER CONTRACT OR
RELAX. (CONTRACT DURING INSPIRATION AND RELAX
DURING EXPIRATION)

18. NERVOUS CONTROL OF BREATHING
Brain
Respiratory center
automatically regulates
breathing
Intercostal nerves
stimulate the
intercostal muscles
Intercostal muscles
Pheric nerve stimulates
the diaphragm
Diaphragm

19. GAS EXCHANGE
EXTERNAL RESPIRATION
• GAS EXCHANGE BETWEEN AIR IN
LUNGS AND BLOOD
• MOVEMENT DRIVEN BY DIFFUSION
GRADIENT. ( [] TO [])
• GASSES EXERTS PRESSURE, THE
AMOUNT OF PRESSURE EACH GAS
EXERTS IS CALLED – PARTIAL
PRESSURE (PO2
AND PCO2
)
INTERNAL RESPIRATION
• GAS EXCHANGE BETWEEN BLOOD
AND TISSUE FLUID
• MOVEMENT DRIVEN BY DIFFUSION
GRADIENT. ( [] TO [])
• GASSES EXERTS PRESSURE, THE
AMOUNT OF PRESSURE EACH GAS
EXERTS IS CALLED – PARTIAL
PRESSURE (PO2
AND PCO2
)

20. EXTERNAL RESPIRATSION
• IF PO2
DIFFERS ACROSS A MEMBRANE – OXYGEN WILL DIFFUSE FROM A HIGH TO
A LOW PRESSURE.
• IF PCO2
DIFFERS ACROSS A MEMBRANE – CARBON DIOXIDE WILL DIFFUSE FROM A
HIGH TO A LOW PRESSURE.
• DURING INSPIRATION THE ALVEOLI FILLS WITH AIR – HIGHER PO2
AND LOWER
PCO2
THAN BLOOD.
• OXYGEN DIFFUSE FROM ALVEOLI INTO BLOOD AND CARBON DIOXIDE DIFFUSE
FROM BLOOD INTO ALVEOLI.

21. INTERNAL RESPIRATION
• WHEN BLOOD REACHES THE TISSUE, CELLULAR RESPIRATION IN CELLS CAUSES
THE TISSUE FLUID TO HAVE A LOWER PO2
AND A HIGHER PCO2
THAN THE BLOOD.
• THUS OXYGEN DIFFUSE FROM A HIGH PRESSURE IN THE BLOOD TO A LOW
PRESSURE IN THE TISSUE FLUID AND EVENTUALLY IN THE TISSUE CELLS.
• CARBON DIOXIDE DIFFUSE FROM A HIGH PRESSURE IN THE TISSUE FLUID TO A
LOW PRESSURE IN THE BLOOD.

23. TRANSPORT OF OXYGEN
• MOST OXYGEN IS TRANSPORTED BY HEMOGLOBIN (RED PIGMENT PROTEIN IN
ERYTHROCYTES).
• OXYGEN COMBINES WITH HEMOGLOBIN TO FORM OXYHEMOGLOBIN.
HB + O2 = HBO2
HEMOGLOBIN OXYGEN OXYHEMOGLOBIN
• A SMALL AMOUNT OF OXYGEN IS TRANSPORTED IN SOLUTION IN THE BLOOD
PLASMA.

24. HEMOGLOBIN MOLECULE
EACH RED BLOOD CELL CARRIES 250
MILLION HB MOLECULES = 1 BILLION
OXYGEN MOLECULES
• CONSIST OF 4 POLYPEPTIDE CHAINS
(PROTEIN – 2 ALPHA AND 2 BETA).
• EACH CHAIN IS ASSOCIATED WITH A HEME
GROUP.
• EACH HEME GROUP CONTAINS AN IRON
ATOM.
• IRON BINDS WITH OXYGEN.

25. TRANSPORT OF CARBON DIOXIDE
• MOST CO2 IS TRANSPORTED AS BICARBONATE IONS (HCO3
-)
HOW?
FIRST CO2 BINDS WITH WATER TO FORM CARBONIC
ACID (H2CO3)
CO2 + H2O = H2CO3
THEN CARBONIC ACID DISSOCIATES TO FORM HYDROGEN
AND BICARBONATE IONS.
H2CO3 = H+ + HCO3
-

26. TRANSPORT OF CARBON DIOXIDE
• A SMALL AMOUNT OF CARBON DIOXIDE IS TRANSPORTED BY THE HEMOGLOBIN
MOLECULES IN THE FORM OF CARBAMINOHEMOGLOBIN (HBCO2).
CO2 + HB = HBCO2
• THE HIGHER THE AMOUNT OF HYDROGEN IONS IN THE BLOOD THE LOWER THE
PH. THEREFOR HYDROGEN IONS BOND WITH THE GLOBIN PART OF HB TO KEEP
THE PH NORMAL IN THE BLOOD.

27. COMMON BRONCHIAL AND PULMONARY
DISEASES
• THE FOLLOWING LOWER RESPIRATORY TRACT DISORDERS ARE CAUSED BY
EXPOSURE TO INFECTIOUS PATHOGENS AND / OR POLLUTED AIR, INCLUDING
TOBACCO SMOKE.
 PNEUMONIA
 PULMONARY FIBROSIS
 PULMONARY TUBERCULOSIS
 EMPHYSEMA
 BRONCHITIS
 ASTHMA

28. PNEUMONIA
BACTERIA STREPTOCOCCUS
CAN CAUSE PNEUMONIA
• ALVEOLI FILL WITH PUS AND FLUID
MAKING GAS EXCHANGE DIFFICULT
X-ray of a
patient with
pneumonia

29. PULMONARY FIBROSIS
• FIBROUS CONNECTIVE TISSUE BUILDS
UP IN LUNGS, REDUCING THEIR
ELASTICITY AND OXYGEN DIFFUSION.

30. PULMONARY TUBERCULOSIS
• CAUSED BY A BACILLUS
BACTERIUM

31. EMPHYSEMA
• ALVEOLI BURST AND FUSE INTO
ENLARGED AIR SPACES. – SURFACE
AREA FOR GAS EXCHANGE IS
REDUCED.

32. BRONCHITIS
• AIRWAYS ARE INFLAMED DUE TO
INFECTION (ACUTE) OR DUE TO AN
IRRITANT (CHRONIC). COUGHING
BRINGS UP MUCUS AND PUS.

33. ASTHMA
• AIRWAYS ARE INFLAMED DUE TO
IRRITATION AND BRONCHIOLES
CONSTRICT DUE TO MUSCLE SPASMS

34. SMOKING AND LUNG DISORDERS
• SMOKING CAUSES ALMOST 90% OF ALL LUNG CANCERS AND IS ALSO A MAJOR
CAUSE OF EMPHYSEMA.
Healthy normal
lung of a non-
smoker
Lung of a
smoker

35. Lung with large
tumors causing
lung cancer

36. Horneja, D (2012). Respiratory system. Accessed from SlideShare
https://www.slideshare.net/dindin04/respiratory-system-10815800 (30 August 2018)