The document summarizes the human respiratory system. It describes the upper and lower respiratory tract. The lower tract consists of the conducting zone and respiratory zone. It then describes the structures involved in respiration like lungs, pleura, diaphragm, nasal cavities etc. It also explains different types of respiration seen across species and the mechanisms of external and internal respiration in humans.

1. RESPIRATION

2. HUMAN RESPIRATORY SYSTEM
UPPER RESPIRATORY TRACT LOWER RESPIRATORY TRACT
1) NOSTRILS
2) NASAL
CAVITIES
3) PHARYNX
4) LARYNX
CONDUCTING ZONE RESPIRATORY ZONE
1) TRACHEA
2) PRIMARY BRONCHI
3) SECONDARY BRONCHI
4) TRETIARY BRONCHI
5) BRONCHIOLES
6) TERMINAL BRONCHIOLE
1) RESPIRATORY
BRONCHIOLES
2) ALVEOLI

3. LOWER RESPIRATORY TRACT
CONDUCTING ZONE RESPIRATORY ZONE
1) THICKER WALL 1) THINNER WALL
2) LARGER DIAMETER 2) SMALLER DIAMETER
3) SMOOTH MUSCLES IN WALLS 3) ABSENT
4) TOTAL AREA OCCUPIED 4) MORE
WITHIN THE LUNG IS LESS
5) VELOCITY OF AIR MOVEMENT* 5) SLOW
IS FASTER

4. RESPIRATORY OR BRONCHIAL TREE

5. INFUNDIBULUM
• Atria are
also called
infundibulum.

6. ALVEOLI
• The number of alveoli present in each lung is 300
million.
• An average diameter of each alveolus is 0.2mm.
• The alveoli of both lungs provide a combined surface
area of 80 sq.meters.
• The trachea undergoes 23 levels of branching to produce
the bronchial tree or respiratory tree.

7. LUNGS
LEFT LUNG
1) Smaller
2) Weighing 550 grams
3) Divided into two lobes namely
superior & inferior by an oblique
fissure
4) Has a cardiac notch to
accommodate the tip of the heart
RIGHT LUNG
1) Larger
2) Weighing 650 grams
3) Divided into three lobes namely
superior, middle & inferior lobes
by oblique and horizontal fissures
4) It is absent

9. PLEURA
• Lungs are surrounded by two pleural membranes. They
are
● Inner visceral/pulmonary
● Outer parietal

11. PLEURISY
• It is the painful infection involving inflammation of
pleura and overproduction of pleural fluid.

12. RESPIRATORY MECHANISMS

13. CELL SURFACE RESPIRATION
• It is the direct exchange of gases between cells and the
environment.
Example; Sponges, coelenterates and protistans

14. CUTANEOUS RESPIRATION
• Skin functions as respiratory surface Example;
Earthworm, leech and frog

15. TRACHEAL RESPIRATION
• This system consists of network of white shining tubes
called tracheae. Tracheae communicate to the outside
through lateral holes called spiracles or stigmata.
It occurs in insects and myriapods.

16. BRANCHIAL/GILL RESPIRATION
• It is the exchange of gases with the help of gills. They
occur in aquatic animals.
• There are two kinds of gills
● External
● Internal

17. PULMONARY RESPIRATION
• It occurs with the help of lungs and
respiratory tract
• Examples; All land vertebrates
including birds and mammals. (Even
whale)

18. PULMONARY SAC RESPIRATION
• It is seen in molluscs.
• Here the mantle or glandular membrane of molluscs is
modified in many cases to function as respiratory sac or
pulmonary sac.

19. BUCCOPHARYNGEAL RESPIRATION
• It is seen in frog and some related animals where the
buccopharyngeal surface functions as respiratory
surface.

20. CLOACAL RESPIRATION
• It is seen in some turtles.
• Some turtles, especially those specialized in diving,
are highly reliant on cloacal respiration during dives.
They accomplish this by having a pair of accessory air
bladders connected to the cloaca, which can absorb
oxygen from the water.
• In zoological anatomy, a cloaca is the posterior
opening that serves as the only such opening for
the intestinal, urinary, and genital tracts of certain
animal species. The word comes from Latin, and means
"sewer". All birds, reptiles, and amphibians possess
this orifice, by which they simultaneously evacuate both
urine and feces

21. SURFACTANT
• The walls of the alveoli are extremely thin, being composed
primarily of a single layer of squamous epithelial cells called type
I cells. Scattered among them are cuboidal cells called type II
cells or Septal cells or surfactant cells. In addition to these cells,
there are roaming phagocytic cells called alveolar macrophages
or dust cells. They are involved in defence.
• These type II cells secrete a fluid called surfactant.
• It forms a coating to the inner surface of an alveolus.
• It lowers the surface tension of alveoli. If the surface tension is
not kept low, the alveoli become smaller during expiration and
collapses.

22. SURFACTANT
Dust cells

24. EUSTACHIAN TUBES
• They are also known as auditory tubes and
pharyngotympanic tubes
• This tube connect the pharynx with the cavity of the
middle ear.

28. CHOANAE
• They are the internal nostrils or nares
• During swallowing of food, it is closed by Uvula.

29. GUARDIAN OF AIRWAYS
• Epiglottis
is called
guardian of
airways

31. NASAL CHAMBER
• Nasal chamber is differentiated into three regions
namely vestibular, respiratory and olfactory parts.
● Vestibular part; It is the anterior most region, lined
by pseudostratified ciliated epithelium, meant for
filtration.
● Respiratory tract; It is the middle region, lined
by glandular and vascular epithelium, meant for
warming up of air.
● Olfactory part; It is the posterior region, lined by
sensory epithelium, meant for olfaction.

32. BRONCHIAL TREE
• The bronchial tree divides 23 times.
• The first 16 generations form the conducting zone.
It includes bronchi, bronchioles and terminal
bronchioles.
• The remaining 7 generations form the transitional
and respiratory zones. They are made up of
respiratory bronchioles, alveolar ducts and alveoli.

33. PHRENIC MUSCLES
• The muscles of diaphragm are called phrenic muscles.

34. THE TONSILS
• The tonsils are the 2 oval masses of lymphoid tissue
lying in the side walls of the oral pharynx. The tonsils
forms part of a ring of lymphoid tissue guarding the
alimentary and respiratory tracts against bacteria.

35. CARTILAGES OF LARYNX
• The wall of larynx is supported by 9 pieces of cartilages.
● 3 of them are unpaired and 3 of them are paired.
● The three unpaired pieces are thyroid cartilage (Adams
apple), epiglottic cartilage (epiglottis) and cricoid cartilage.
● Paired ones are the arytenoids, corniculate and cuneiform
cartilages.

37. PRESSURES INVOLVED IN
BREATHING
Atmospheric
pressure
It is the pressure
exerted by
surrounding air on
the body.
It is 760 mm Hg.
It is a positive
pressure.
Intrapulmonary
pressure
It is the pressure
exerted within the
lung.
It is 760 mm Hg.
It is a positive
pressure.
Intrapleural
pressure
It is the pressure
exerted within the
pleural space.
It is 756 mm Hg.
It is a negative
pressure.

38. RESPIROMETER OR SPIROMETER
• It is a device to measure the amount of air exchanged
during breathing. Its recording is called a “spirogram”.
• Spirometer is also called pulmometer.
• Measurement of lung capacity with the help of
spirometer is called spirometry.

39. SPIROMETER
• The instrument used in
measuring and recording
the volume of air exchanged
during breathing is called
spirometer or respirometer.

40. BREATHING RATE
▪ Normal breathing rate in a new-born baby is 32/ minute.
▪ In a child of 6 years of age , it is about 26/minute.
▪ It is 12-15/minute in a man of 25-30 years of age.
▪ It is 18/minute in a man of 50 years of age.

41. RESPIRATORY VOLUMES
• Tidal volume: - It is the amount of air move in
and out of lungs during normal breathing. It is
approximately 500 ml of air for an average person.
• Inspiratory reserve volume: - It is the amount of air
inspired forcefully over and above the tidal volume.
It is about 3000ml for a normal person.
• Expiratory reserve volume: - It is the amount of air
that can be forcefully expired over and above the
tidal volume. It is about 1200 ml on the average.

42. RESPIRATORY VOLUMES
• Vital capacity: - It is the maximum amount of
air a person can move in and out of his lungs.
It is equivalent to the sum of the tidal volume +
inspiratory and expiratory reserve volumes.
The vital capacity of an average person is about
4500-5500 ml.
• Residual volume: - Even after a maximum
expiration about 1200 ml of air remains in the
lungs. This is known as the residual volume.

43. RESPIRATORY VOLUMES
• Tidal volume; 500mL
• Inspiratory reserve volume (Inspiratory capacity); 3000-
3500ml
• Expiratory reserve volume; 1200ml
• Vital capacity; 4500-5500ml
(TV+IRV+ERV=500+3000+1200= 4700ml)
• Residual volume; 1200ml

44. TIDAL VOLUME
• It is 500ml
• It consists of 150ml of dead space volume and 350 ml of
alveolar volume

45. CARRYING CAPACITY OF BLOOD
• 20ml of oxygen and 3-7ml of CO2/100 ml of blood

46. OXYGEN CARRYING CAPACITY OF
HAEMOGLOBIN
• There is about 15gm of haemoglobin in 100 ml of blood,
which can transport about 20 ml of oxygen.

47. RESPIRATORY MINUTE VOLUME
(RMV)
• It is the product of tidal volume and normal breathing
rate per minute i.e. 500 x 12 =6000ml/minute

48. RESPIRATORY VOLUMES;
• Functional residual capacity; It is sum total of ERV+
residual volume i.e. 1200+1200= 2400
• Total lung capacity; Maximum amount of air the lungs
can hold after forceful inspiration. It is 6000ml. It is the
sum of IRV+ERV+TV+RV

49. ANATOMICAL DEAD SPACE AIR
• It is the volume of air, present in the conducting zone of
human respiratory system.
• It is not used for exchange of gases
• It is 150 ml

50. RESPIRATORY CYCLE
• A respiratory cycle includes one inspiration and one
expiration
• An average period taken by one respiratory cycle is 5
seconds
• Out of 5 seconds, 2 seconds are for inspiration and 3
seconds for expiration. It is calculated by multiplying
tidal volume and respiratory rate per minute. (500ml x
12= 6000ml/minute)

52. INSPIRATION

53. EXPIRATION

54. PHONATION
• It is the production of sound. It is the non-respiratory
function of larynx

55. MOUNTAIN SICKNESS
• When a person living on plains ascends and stays on a
mountain about 8000 feet from sea level, he develops
mountain sickness. Its symptoms are nausea, headache,
breathlessness, dizziness, mental fatigue and a bluish
tinge on skin, nails and lips.
• Rate of breathing increases with altitude. Hill people
have more RBC’s.

56. MECHANISM OF RESPIRATION
• External respiration
• Transport of gases by blood
● Transport of CO2
• In the form of carbonic acid
• In the form of ions and bicarbonates
• In the form of carbaminohaemoglobin
● Transport of O2
• As solution in plasma
• Through RBC as oxyhaemoglobin
• Internal respiration and cellular oxidation

57. AIR-BLOOD BARRIER
• The alveolar-capillary membrane acts as the air-blood
barrier. This is due to the membrane with air on the
alveolar side and blood on the capillary side

58. LUDWIG (1872);
• He described gaseous exchange in blood.

59. CHRISTIAN BOHR (1904)
• He put forth Bohr’s effect in 1909
• According to this” the affinity of haemoglobin to O2
reduces with increased concentration of CO2”

60. HALDANE EFFECT
• Carbaminohaemoglobin is produced more readily when
the haemoglobin is deoxygenated. Therefore binding of
O2 to Hb reduces its affinity for CO2. This effect is called
Haldane effect.

61. ROSE FEVER
• Hay fever is even known by the name rose fever or
Rhinitis or Pollenosis.

62. EMPHYSEMA
▪ It is one of the diseases along with bronchitis and asthma,
coming under COPD (chronic obstructive pulmonary
diseases).
▪ The meaning of emphysema is fully blown out.
▪ It is a disorder of the pulmonary system characterized by
destructive changes of alveolar walls resulting in loss of
lung elasticity and reduces the ventilation of alveoli.

63. BARREL CHEST
• Emphysema and smoke inhalation makes the lungs to
loose their elasticity. The lungs become permanently
inflated. To adjust to the increased lung size, size of
thoracic cavity also increases. This condition is called as
Barrel chest.

64. BIOPSY
• It is a technique of detecting abnormal malignant cells in
a tissue.

65. METASTASIS
• It is a state in which malignant tumour cells move from
the site of formation to other parts through transport
system (blood and lymph)

66. HYPOXIA
• Reduced supply of oxygen to the tissues.
• Types of hypoxia;
● Hypoxic hypoxia; It is a state where PO2 of the arterial blood is
extremely low.
● Anemic hypoxia; It is a state where the arterial PO2 is normal but
the amount of haemoglobin available to carry O2 is reduced.
● Stagnant or Ischemic hypoxia; It is a state where the blood flow to
a tissue is so low, that adequate O2 is not delivered to it inspite of
normal PO2 and haemoglobin concentration.
● Histotoxic hypoxia; It is a state where the amount of O2 delivered to
a tissue is adequate but because of the action of toxic agents, cells
cannot make use of the O2. Cyanide poisoning leads to histotoxic
hypoxia, as the poison blocks electron transport chain.

67. ANOXIA
• An absence of oxygen supply to the tissues is known as
anoxia

68. HYPERCAPNIA
• Increased concentration of CO2 in blood is known as
hypercapnia

69. APNOEA
• The complete cessation of breathing is known as apnoea

70. DYSPNOEA
• The forceful breathing (i.e. difficulty in breathing) is
known as dyspnoea.

71. EUPNOEA
• It is the process of normal breathing

72. HYPOPNOEA
• Slower breathing rate

73. HYPERPNOEA
• Rapid i.e. increased breathing caused by emotions,
exercise etc.

74. ASPHIXIA (BREATHING ARREST)
• Paralysis of respiratory centre due to excessive CO2.
• It is commonly due to irreversible combination of CO
with haemoglobin to form carboxyhaemoglobin. It
results in death.
• It is common in closed rooms with coal burning, kerosine
lamp etc.

75. EPISTAXIS
• Nose bleeding
• It may be due to scratching of nasal membranes or
hypertension.

76. BOOK LUNG
• It is a terrestrial respiratory organ similar to the purse
with a number of compartments.
• It occurs in spiders and scorpions

77. BOOK GILL
• It is an aquatic respiratory organ found in Limulus. It
consists of a number of leaf-like structures , between
which water circulates.

78. THE LYMPH
• The lymph flows in lymphatic vessels very slowly. Only
about 10-20 liters of lymph passes into the blood in a
day.

79. HICCOUGH (HICCUP)
• Inspiratory spasm caused by sudden contraction of
diaphragm accompanied by loud closure of glottis.

80. PHARYNGITIS
• Inflammation of pharynx.

81. LARYNGITIS
• Inflammation of larynx.

82. SNEEZING
• An involuntary, sudden, violent and audible expulsion of
air through mouth and nose.

83. YAWNING
• A deep involuntary inspiration with mouth open, often
accompanied by act of stretching.

85. SARS
• It is a killer typical pneumonia called “SEVERE ACUTE
RESPIRATORY SYNDROME”.
• It is caused by a variant of common cold Corona virus.