The respiratory system allows for gas exchange through breathing. Air enters the nose and travels through the pharynx, larynx, trachea, bronchi and bronchioles to the alveoli in the lungs. In the alveoli, oxygen diffuses into the bloodstream and carbon dioxide diffuses out. The blood carries oxygen to tissues and removes carbon dioxide through external and internal respiration.

1. Respiratory
System

2. v Major Functions
v Gas exchange (external and internal exchange)
v Cleanse/Moisten/Warm Air
v Inspiration and expiration move air in and out of the
lungs during breathing.
v Cellular respiration is the final destination where ATP is
produced in cells.
Introduction

3. The respiratory tract

4. The Nose
v The two nasal cavities are divided by a septum.
v They contain olfactory cells, receive tear ducts from
eyes, and communicate with sinuses.
v The nasal cavities empty into the nasopharynx.
v Auditory tubes lead from the middle ears to the
nasopharynx.

5. The path of air

6. The Pharynx
v The pharynx (throat) is a passageway from the nasal
cavities to oral cavities and to the larynx.
v The pharynx contains the tonsils; the respiratory tract
assists the immune system in maintaining homeostasis.
v The pharynx takes air from the nose to the larynx and
takes food from the oral cavity to the esophagus.

7. The Larynx
v The larynx is a cartilaginous structure lying between the
pharynx and the trachea.
v The larynx houses the vocal cords.
v A flap of tissue called the epiglottis covers the glottis, an
opening to the larynx.
v In young men, rapid growth of the larynx and vocal cords
changes the voice.

8. Placement of the vocal cords
15-8

9. The Trachea
v The trachea, supported by C-shaped cartilaginous rings, is
lined by ciliated cells, which sweep impurities up toward
the pharynx.
v Smoking destroys the cilia.
v The trachea takes air to the bronchial tree.
v Blockage of the trachea requires an operation called a
tracheostomy to form an opening.

10. Cilia in the trachea
15-10

12. The Bronchial Tree
v The trachea divides into right and left primary bronchi
which lead into the right and left lungs.
v The right and left primary bronchi divide into ever smaller
bronchioles to conduct air to the alveoli.
v An asthma attack occurs when smooth muscles in the
bronchioles constrict and cause wheezing.

13. The Lungs
v Lungs are paired, cone-shaped organs that lie on either
side of the heart and within the thoracic cavity.
v The right lung has three lobes, and the left lung has two
lobes, allowing for the space occupied by the heart.
v The lungs are bounded by the ribs and diaphragm.

14. The Alveoli
v Alveoli are the tiny air sacs of the lungs made up of
squamous epithelium and surrounded by blood capillaries.
v Alveoli function in gas exchange, oxygen diffusing into the
bloodstream and carbon dioxide diffusing out.
v Infant respiratory distress syndrome occurs in premature
infants where underdeveloped lungs lack surfactant (thin
film of lipoprotein) and collapse.

15. Gas exchange in the lungs

16. v During breathing, air moves into the lungs during
inspiration (inhalation) from the nose or mouth, then
moves out again during expiration (exhalation).
v A spirometer allows measurement of the components
of air during breathing.
Mechanism of Breathing

17. Respiratory Volumes
v Tidal volume (VT) the normal amount of air
moved in and out of the lungs when relaxed, is
usually 500 ml.
v Inspiratory reserve volume is the maximum
amount of forcibly inspired air.
v Expiratory reserve volume is the maximum
amount of forcibly expired air.
v Vital capacity is the maximum amount of air
moved in and out on deep breathing, and is the
sum of tidal, inspiratory reserve, and expiratory
reserve volumes.
v Air that remains in the lungs is residual volume.

18. Vital capacity

19. Inspiration and Expiration
v There is a continuous column of air from the pharynx to
the alveoli, and the lungs lie within the sealed-off thoracic
cavity.
v The thoracic cavity is bounded by the rib cage and
diaphragm.
v Pleural membranes line the thoracic cavity and lungs and
the intrapleural pressure is lower than atmospheric
pressure, keeping the lobules of the lungs from collapsing.
v Minute Ventilation – The volume of inhaled and exhaled
air in one minute.

20. Inspiration
v When we inhale (inspiration) impulses from the
respiratory center in the medulla oblongata cause the rib
cage to rise and the diaphragm to lower, causing the
thoracic cavity to expand.
v The negative pressure or partial vacuum in the alveoli
causes the air to come in.
v Changing amounts of blood of H+ and CO2 detected by
chemoreceptors in the carotid arteries and aorta increase
breathing rate.

21. O2 UPTAKE DURING
EXERCISE
v VO2 - measured in
ml/Kg/min
v VO2max - maximal
oxygen uptake
v Metabolic Cart
v Predicted VO2max
testing
v Astrand 6 min. test
v Balke Test

22. Nervous control of
breathing

23. Inspiration

24. Expiration
v When we exhale (expiration), lack of impulses from the
respiratory center allow the rib cage to lower and the
diaphragm to resume a dome shape.
v Expiration is passive, while inspiration is active.
v The elastic recoil of the lungs causes expiration (gravity).
v A deep breath causes alveoli to stretch; stretch receptors
then inhibit the respiratory center via the vagus nerve.

25. Expiration

26. Expiration: active
v Under extreme conditions, exhalation becomes
dynamic.
v Internal intercostal muscles contract forcing the ribs
down and inward.
v Tightening of the abdominal walls also pushes on the
viscera which pushes the diaphragm and forces out
even more air.
v FEV1 – the amount of air forcibly expired in one
second. Reduced in patients with COPD

27. Spirometry

28. v External Respiration
v Individual gases exert pressure proportional to their
portion of the total in a mixture of gases; this is called
“partial pressure” (PO2). (Air - 21% O2, 0.04% CO2)
v External respiration is the diffusion of CO2 from
pulmonary capillaries into alveolar sacs and O2 from
alveolar sacs into pulmonary capillaries.
v Most CO2 is carried as bicarbonate ions.
v The enzyme carbonic anhydrase, in red blood cells,
speeds up the conversion of bicarbonate and H+ to
H2O and CO2; CO2 enters alveoli and is exhaled.
Gas Exchange

29. Partial
Pressures

30. Hemoglobin Structure
v Hemoglobin (Hb)
takes up oxygen
from alveoli and
becomes
oxyhemoglobin
(HbO2).
v 4 globular proteins
(globin) & 4 heme
units.
v (64 000 daltons)

31. Internal Respiration
v Internal respiration is the diffusion of O2 from systemic
capillaries into tissues and CO2 from tissue fluid into
systemic capillaries.
v Oxyhemoglobin gives up O2, which diffuses out of the
blood and into the tissues because the partial pressure of
O2 of tissues fluid is lower than that of the blood.
v After CO2 diffuses from tissue cells into the blood, it enters
red blood cells where a small amount is taken up by
hemoglobin, forming carbaminohemoglobin.

32. Internal Respiration Cont.
v Most of the CO2 combines with water to form
carbonic acid (H2CO3), which dissociates to release
hydrogen ions (H+) and bicarbonate ions (HCO3
-);
the enzyme carbonic anhydrase speeds this reaction.
v The globin portion of hemoglobin combines with
excess hydrogen ions to become reduced hemoglobin
or HHb; this helps maintain a normal blood pH.
v Blood leaving capillaries is a dark maroon color
because red blood cells contain reduced hemoglobin.

33. External and Internal Respiration

34. External and Internal Respiration
External
v Hb + O2 à HbO2
v HbCO2 à Hb + CO2
v H+ + HCO3
- à H2CO3
à CO2 + H2O
Internal
v HbO2 à Hb + O2
v CO2 + H2O à H2CO3
à H+ + HCO3
-
v Hb + CO2 à HbCO2
v H+ + Hb à HHb
v HCO3
- dissolves in
plasma
Chemical Equation Summary

36. Respiratory Centre
• located in the medulla oblongata
• stimulated by the presence of CO2 and H+ ions.
• neurons send automatic rhythmic discharge that
triggers breathing
• the signals travel to the diaphragm and the intercostal
muscles via the phrenic nerve.

37. v Low O2 in blood
registered by carotid
and aortic bodies
v Communication with
respiratory centre
v Increase in minute
ventilation occurs
v Hemoglobin has 200X
affinity for CO than O2
Respiratory Centre Cont.

38. Hemoglobin Saturation (SO2)
v Lungs: 98-100% saturated
v Tissues: 60-70% saturated
v Conditions affecting Saturation:
v Partial Pressure of O2 – incr. é SO2
v pH – incr. pH é SO2
v Temperature – incr. temp ê SO2
v Exercise – increases temperature and decreases pH
causing a decrease in arterial oxygen saturation (SaO2)

39. Oxyhaemoglobin Dissociation Curve

40. v Common Respiratory System Diseases:
v Asthma
v COPD
v Chronic Bronchitis
v Emphysema
v Pleurisy
v Cancer
v Influenza
v Sinusitis
Respiration and Health

41. Sites of upper respiratory infections

42. Sinusitis
v Sinusitis is infection of the cranial sinuses within the
facial skeleton that drain into nasal cavities.
v It occurs when nasal congestion blocks the sinus
openings and is relieved when drainage is restored.
v Pain and tenderness over the lower forehead and
cheeks, and toothache, accompany this condition.

43. Lower respiratory tract disorders

44. COPD
Chronic Bronchitis
v Long-term cough with
mucus
Emphysema
v A breakdown of the
alveoli walls.
Causes, Risk Factors, Symptoms
v Smoking
v Exposure to gases and fumes, cooking fire
v Cough, Fatigue, many R.T.I, Wheezing

45. Asthma
v Muscle lining small airways becomes irritated
v Causes a narrowing of airway passages
v Steroids or bronchodilators can be used to prevent
constriction

46. Lung Cancer
v Lung cancer follows this sequence of events: thickening of
airway cells, loss of cilia on the lining, cells with atypical
nuclei, tumor development, and finally metastasis.
v Removal of a lobe or lung, called pneumonectomy, may
remove the cancer.
v Smoking, whether active or passive, is a major cause of
lung cancer.

47. Normal lung versus cancerous
lung
15-47

48. Chapter Summary
v Air passes through a series of tubes before gas exchange
takes place across an extensive moist surface in the alveoli
of the lungs.
v Respiration comprises breathing, external and internal
respiration, and cellular respiration.
v During inspiration, the pressure in the lungs decreases and
air comes rushing in; during expiration, increased pressure
in the thoracic cavity causes air to leave the lungs.

49. Chapter Summary Cont.
v External respiration occurs in the lungs where oxygen
diffuses into the blood and carbon dioxide diffuses out
of the blood.
v Internal respiration occurs in the tissues where oxygen
diffuses out of the blood into tissue cells and carbon
dioxide diffuses into the blood.
v Spirometry is the measurement of lung capacities and
can be used to diagnose certain respiratory conditions
such as COPD.

50. Chapter Summary Cont.
v The respiratory pigment hemoglobin transports
oxygen from the lungs to the tissues and aids in the
transport of carbon dioxide from the tissues to the
lungs.
v Hemoglobin’s oxygen affinity is affected by pH, temp
and PO2
v The respiratory tract is especially subject to disease
because it is exposed to infectious agents; also,
cigarette smoking contributes to two major lung
disorders—emphysema and cancer.