The respiratory system consists of the nose, pharynx, larynx, trachea, bronchi, bronchioles and lungs. The nose and pharynx warm and humidify air before it reaches the lungs. The trachea divides into the right and left bronchi which enter the lungs and continue dividing into smaller bronchioles and alveoli where gas exchange occurs. Breathing is driven by the contraction of the diaphragm and intercostal muscles which expand the lungs to draw in air. Oxygen diffuses into the blood in the alveoli and carbon dioxide diffuses out, supported by the lungs, pleura and respiratory muscles.

1. Anatomy And
Physiology of
Respiratory System

3. Introduction
● The body cell continually use oxygen for the metabolic
reaction that release energy from nutrient molecule and
produce ATP.
● At the same time , these reaction release carbon-di-oxide
● Because of excessive amount of carbon di oxide produces
acidity that can be toxic to the cell, excess CO2 must be
eliminated quickly and efficiently
● The respiratory system supports to supply oxygen and
eliminate carbon-di-oxide

4. Definition
• The respiratory system (also respiratory apparatus,
ventilatory system) is a biological system, consisting of
specific organs and structures used for gas exchange in
human.

6. • Organs of Respiratory System:
• Nose and nasal cavity.
• Pharynx (throat)
• Larynx (voice box)
• Trachea (wind pipe)
• Bronchi
• Bronchioles
• Lungs
Conducting zone
Alveolar ducts
Alveolar sac
Alveoli
Respiratory zone

7. NOSE AND NASAL CAVITY
• POSITION AND STRUCTURE
• Main route of air entry.
• Especially
● Two cavities divided by a SEPTUM.
● Anteriorly consist hyaline cartilage.
● The roof is formed by ethmoid bone
● The floor is formed by roof of the mouth.
● The medial wall formed by the septum.
● The lateral wall formed by the maxilla.

9. RESPIRATORY FUNCTIONS OF THE NOSE
• The first of the respiratory passages.
• Warming- Due to the immense vascularity of the mucosa.
• Filtering and cleaning- This occurs due to hairs which trap
larger particles.
• Humidification - As air travels over the moist mucosa, it
becomes saturated with water vapour.

10. Pharynx
• The pharynx is the part of the throat that is behind the
mouth and nasal cavity and above the esophagus and the
larynx.
● Length- 12-14cm (extends from the base of the skull to the
level of 6th cervicalvertebra.)
● Position
● Superiorly-Base of the skull.
● Inferiorly-Continuous with the oesophagus.
● Anteriorly-Incomplete wall because of the
nose, mouth and larynx opening.
● Posteriorly- Areolar tissue & first 6 vertebra.

12. • For descriptive purposes the pharynx is
divided into three parts:
• The Nasopharynx
• The oropharynx
• The laryngopharynx
• The nasopharynx - The nasal part of the
pharynx lies behind the nose.
• The oropharynx - The oral part of the pharynx
lies behind the mouth.
• The laryngopharynx - The laryngeal part of
the pharynx extends from the oropharynx.

14. • STRUCTURE
• The pharynx is composed of three layers: Mucous
membrane lining
● Fibrous tissue
● Smooth muscle
● Blood supply
Facial artery
● Facial vein
● Internal jugular veins
● Nerve supply
● Vagus nerve
● Glossopharyngeal nerve

15. Functions
• Passageway for air and food.
• Warming and humidifying.
• Taste.
● There are olfactory nerve endings.
• Hearing.
●The auditory tube,extending from the nasopharynx to each
middle ear.
• Protection.
●The lymphatic tissue of the pharyngealtonsils produces
antibodies.
• Speech.
●Act as a resonating chamber for sound ascending from the
larynx.

16. Larynx
• POSITION
• The larynx or voice box extends from the root of the tongue.
• It lies in front of the laryngopharynx at the level of 3rd , 4th,5th
and 6th cervicalvertebra.
• Until the puberty there is little difference in the size of the
larynx between the sexes.
• It grows larger in the male.
● Superiorly-The hyoid bone & roof of the tongue.
● Inferiorly-Continuous with the trachea.
● Anteriorly-The muscle of the neck.
● Posteriorly-.The laryngopharynx and 3rd to 6th cervical
vertebra.

18. ● STRUCTURE
• The larynx is composed of several irregularly shaped
cartilages attached to each other by ligaments and
membranes.
• The main cartilages are:
• 1 thyroid cartilage
● 1 cricoid cartilage hyaline cartilage
● 2 arytenoid cartilage
● 1 epiglottis elastic-fibro cartilage

19. ●The thyroid cartilage - This is the most prominent &
consists of 2 flat pieces of hyaline cartilage & fused
anteriorly forming the Adam’s apple.
●The cricoid cartilage - This lies below the thyroid
cartilage & composed of hyaline cartilage.
●The arytenoid cartilages - These are two roughly
pyramid-shaped hyaline cartilages situated on top of the
broad part of the cricoid cartilage.
●The epiglottis - This is a leaf-shaped fibroelastic
cartilage attached to the inner surface of the anterior
wall of the thyroid cartilage.
● Blood and nerve supply
• Superior and inferior laryngeal arteries.
• Thyroid veins.
• Superior laryngeal nerves.

21. FUNCTIONS
• Production of sound
• Speech
• Protection of the lower respiratory tract During
swallowing the larynx moves
● upwards and hinged epiglottis closes over the larynx.
• Passageway for air
• Humidifying
• Filtering
• Warming

22. Trachea
• Position
• The trachea or windpipe is a continuation of the larynx &
extends downwards to about the level of T-5 where it divides
into right & left primary bronchi.
• Length-10-11cm
• Relation
● Superiorly- the larynx
● Inferiorly- the right & left bronchi
● Anteriorly- upper part- the thyroid gland, lower part- the
arch of aorta & the sternum.
● Posteriorly-.the oesophagus
● Laterally- the lungs

25. ● STRUCTURE
• Composed of 3 layers of tissue.
• (i) fibrous & elastic tissue
• (ii) smooth muscle
• (iii) ciliated columnar epithelium
• Held open by between 16-20 incomplete cartilage rings (C-
shaped)
● Blood supply
● Inferior thyroid artery
● Bronchial artery
● Venous drainage Inferior thyroid veins
● Nerve supply Laryngeal nerve

26. ● FUNCTIONS
• Support and patency
• Mucociliary escalator
• Cough reflex
• Warming
• Humidifying
• Filtering

27. Bronchi and Bronchioles
• The two primary bronchi when the trachea divides about
the level of T-5.
• The right bronchus
• This is wider,shorter and more vertical than the left
bronchus.
• Length-2.5cm
• After entering the right lung,it divides into 3 branches,one
to each lobe.

28. • The left bronchus
• This is narrower than the right
• Length-5cm
• After entering the left lung, it divides into 2 branches, one to each
lobe.
● STRUCTURE
• The bronchi are composed of the same issues as the trachea.
• Are lined with ciliated columnar epithelium.
• Ciliated columnar mucous membrane changes gradually to non-
ciliated cuboidal-shaped cells in the distal bronchioles.

30. Division
Division of bronchi
Bronchioles Terminal
Bronchioles
Respiratory bronchioles
Alveolar ducts
Alveoli

33. • The wider passages are called conducting airways
• Conducting airways,bring air into the lungs & their walls
are too thick to permit gas exchange.
• Blood supply
• Bronchial arteries
• Venous drainage
• Bronchial veins
• Nerve supply
• Vagus nerve
• Lymph drainage
• The Thoracic duct

34. ● FUNCTIONS
• Control of air entry
• Warming & humidifying
• Support & patency
• Removal of particulate matter
• Cough reflex

35. • RESPIRATORY BRONCHIOLES & ALVEOLI
• Each lobule is supplied with air by a terminal
bronchiole
• Which further subdivides into respiratory bronchioles,
alveolar ducts and large numbers of alveoli (air sacs)
• About 150 million alveoli in the adult lung
• In these structures that the process of gas exchange occurs.
• As airways progressively divide & become smaller & smaller, their
walls gradually become thinner.
• These distal respiratory passages are supported by a loose
network of elastic connective tissue.
• Exchange of gases in the lungs takes place in alveoli

37. • Nerve supply
• Vagusnerve
• FUNCTIONS
• External respiration
• This is exchange of gases by diffusion between the alveoli and the
blood.
• Defence against microbes
• Protective cells present within the lung tissue, include
lymphocytes & plasma cells, which produce antibodies.
• Exchange of gases

38. Lungs
• There are two lungs,one lying on each side.
• Shape-cone
• Weight-600-700gms
• Length-20-24cm
• Colour-pinkish
• Lobes- three lobes in the right lung
• two lobes in the left lung
• Lobes are separate by the fissures
• The area between the lungs is the mediastinum.

39. • Surfaces
• Apex
• A base
• Costal surface
• Medial surface
• Apex – rounded and rises into the root of the neck.
• A base-this is concave & semilunar in shape, lies on the
● thoracic surface of the diaphragm.
• Costal surface-this surface is convex & lies against the costal
cartilages.
• Medial surface-this surface is concave & has a roughly triangular-
shaped area,called the hilum.The pulmonary artery supplying the
lung & two pulmonary veins draining it.

43. • The pleura consists of a closed sac of serous membrane,one for
each lung which contains a small amount of serous fluid.
• The lung is invaginated or pushed into this sac.
• It forms two layers:
• (i)The visceral pleura
• (ii)The parietal pleura
• (i)The visceral pleura - This is adherent to the lung,covering each
lobe & passing into the fissures that separate them.
• (ii)The parietal pleura - This is adherent to the inside of the chest
wall & the thoracic surface of the diaphragm.

44. ● The pleural cavity
• The two layers of pleura are separated by a thin film of serous
fluid which allows them to glide over each other.
• Preventing friction between them during breathing.
• The serous fluid is secreted by the epithelial cells of the
membrane.

46. (i)
(ii)
(iii)
● RIGHT LUNG
• The right lung has more lobes and segments than the left.
• It is divided into three lobes:
Upper or superior lobe
Middle lobe
Lower or inferior lobe
• They separate by two fissures
i. One oblique fissure which separates middle & lower lobe
ii. One horizontal fissure which separates middle & upper
lobe

47. ● LEFT LUNG
• The left lung is divided into two lobes
• (i) upper lobe
• (ii) lower lobe
• They separate by the oblique fissure
• Left lung does not have a middle lobe
• The mediastinal surface of the left lung has a large cardiac
impression or cardiac notch where the heart sits.

48. ● BLOOD SUPPLY
• Bronchial arteries
• Pulmonary capillaries,where there is exchange of oxygen &
carbon dioxide take place between blood & tissues.
• VENOUS DRAINAGE
• Bronchial vein
• NERVE SUPPLY
• Vagus nerve

49. ● FUNCTION
• Control of air entry
• Warming & humidifying
• Support & patency
• Removal of particulate matter
• Cough reflex

50. respiration
• The term respiration means the exchange of gases between body
cells and the environment.
• Breathing or pulmonary ventilation
• This is movement of air into and out of the lungs.
• Exchange of gases:
• This takes place:
• In the lungs: external respiration.
• In the tissues: internal respiration.

51. breathing
• Breathing supplies oxygen to the alveoli and eliminates carbon
dioxide.
• MUSCLES OF BREATHING
• Expansion of the chest during inspiration occurs as a result of
muscular activity partly voluntary and partly involuntary.
• The main muscles used in normal quiet breathing are the
INTERCOSTAL MUSCLES and the DIAPHRAGM.
• During difficult or deep breathing they are assisted by muscles of
the neck shoulders and abdomen.

52. ● INTERCOSTAL MUSCLES
• There are 11 pairs of intercostal muscles that occupy the spaces
between the 12 pairs of ribs.
• They are arranged in two layers,the external
● and internal intercostal muscles
• The first rib is fixed.
• Therefore, when the intercostal muscles contract they pull all the
other ribs towards the first rib.Because of the shape and sizes of
the ribs they move outwards when pulled upwards,enlarging the
thoracic cavity.

54. ● DIAPHRAGM
• The diaphragm is a dome-shaped muscular structure
separating the thoracic and abdominal cavities.
• It forms the floor of the thoracic cavity and the roof of the
abdominal cavity and consists of a central tendon from which
muscle fibres radiate to be attached to the lower ribs and
sternum and to the vertebral column by two crura.
• When the muscle of the diaphragm is relaxed ,the central tendon
is pulled downwards to the level of the T-9,enlarging the thoracic
cavity in length.
• This decreases pressure in the thoracic cavity and increases it in
the abdominal and pelvic cavities.

56. • The intercostals muscles and the diaphragm
contract simultaneously, enlarging the thoracic
cavity in all directions.
• CYCLE OF BREATHING
• The average respiratory rate is 12 to 15
breaths/minute.
• Each breath consists of three phases:
•
•
• (i)Inspiration
(ii)Expiration
(iii)Pause.

57. Inspiration
• When the capacity of the thoracic cavity is increased by
simultaneous contraction of the intercostal muscles and the
diaphragm.
• The parietal pleura moves with the walls of the thorax & the
diaphragm.
• This reduces the pressure in the pleural cavity to a level
considerably lower than atmospheric pressure.
• The visceral pleura follows the parietal pleura
● ,pulling the lungs with it.
• This expands the lungs and the pressure within the alveoli and
in the air passages drawing air into the lungs in attempt to
equalise the atmospheric and alveolar air pressure.

58. • The process of inspiration is ACTIVE as it needs energy for
muscle contraction.
• Inspiration lasts about 2 seconds.
• (ii)Expiration
• Relaxation of the intercostal muscles and the diaphragm results
in downward and inward movement of the rib cage and elastic
recoil of the lungs.
• As this occurs pressure inside the lungs exceeds that in the
atmosphere and so air is expelled from respiratory tract.
• The still contain some air are prevented from collapse by
the intact pleura.
• This process is PASSIVE as it does not require the expenditure
of energy.

59. Lungs Volume and Capacity
• Respiratory cycles-15/minute
• Tidal volume (TV)- this is the amount of air passing
into and out of the lungs during each cycle of
breathing.
• About 500ml is tidal volume.
• Minute ventilation(MV)- the total volume of air inhale
and exhale each minute
• It is calculated by respiratory rate multiply by tidal
volume

60. ● E.g.- if respiratory rate is 12 breath per minute.
● MB=12 br/min X 500 ml/br=6 lit./min.
● The lower than normal minute ventilation usually is a sign of
pulmonary mal-function.
● The apparatus commonly used to measure the volume of
air exchanged during breathing and the respiratory rate is a
spyrometer or respirometer.
●

61. Anatomic (Dead Space)
● Tidal volume varies from one person to another person and
in same person at different time.
● About 70% of the tidal volume (350ml) actually reaches the
respiratory zone of the respiratory system.
● The other 30% (150ml) remain in the conducting airway
with air that does not undergo respiratory exchange are
known as anatomical respiratory dead space.

62. Alveolar ventilation rate
● It is the volume of air per minute that actually reaches the
respiratory zone is known as alveolar ventilation.
● Alveolar ventilation rate is tidal volume – respiratory dead
space (500-150=350ml/br).
● Alveolar ventilation rate (avr)=breath/min x alveolar
ventilation.
● E.g.- if respiratory rate is 12 br/min.
● Avr=12 x 350=4200ml/min

63. Inspiratory Reserve Volume
● While taking a very deep breath, person can inhale good
deal more than 500ml and this additional inhale air is called
the inspiratory reserve volume.
● In average adult male=3100ml.
● In average adult female=1900ml.

64. Expiratory Reserve Volume
● Inhale normally and then exhale as forcly as possible one
should be able to push out consideriable more air in
addition to the 500ml of tidal volume is called expiratory
reserve volume.
● In males =1200ml
● In females=700ml

65. Forced expiratory volume
● The volume of the air that can exhale from the lung in 1
sec. with maximum following the maximal inhalation.

66. Residual volume
● After the expiratory reserve volume is exhaled, air remain in
the lungs because some atmospheric intra-pleural pressure
keep the alveoli slightly inflated, and some air also remain
in the non-collapsible airway this volume which cannot be
measured by spyrometry is called residual volume.
● In males = 1200ml
● In female = 1100ml

67. Minimal volume
● If the thoracic cavity is opened the inta-pleural pressure
rises to equal that atmospheric presure and fore out some
of the residual volume the air remains is called minimal
volume

68. Lung Capacities
● Lung capacities are combination of specific lung volume.
● Inspiratory capacity=tidal volume+inspiratory reserve
volume
● In males= 500ml+3100ml=3600ml
● In females= 500ml+1900ml=2400ml
● functional residual capacity= residual volume+expiratory
reserve volume
● In males= 1200ml+1200ml=2400ml
● In females= 1100ml+700ml=1800ml

69. ● Vital capacity= inspiratory reserve volume+ tidal volume+
expiratory reserve volume.
● In males=3100ml+500ml+1200ml=4800ml
● In females= 1900ml+500ml+700ml=3100ml
● Total lung capacity= vital capacity + residual volume
● In males= 4800ml+1200ml=6000ml
● In females= 3100ml+1100ml= 4200ml

70. Pulmonary Ventilation
● The process of gas exchange in the body for respiration
has 3 basic steps-
1. Pulmonary ventilation (breathing) is a inhalation exhalation
of air and involves the exchange of air between the
atmosphere and the alveoli of the lung.
2. External respiration is the exchange of gases between the
alveoli of lungs and the blood in pulmonary capillaries
across the respirtory membrane. In this process pulmonary
capilary blood gains O2 and looses CO2

71. 1. internal respiration- It is the exchange of gases between
blood in systemic capillaries and tissue cells. In this step
the blood looses O2 and gain CO2
2. In pulmonary ventilation air flows between the atmosphere
and the alveoli of the lungs because of altering pressure
difference created by contraction and relaxation of
respiratory muscles.

72. Pressure change during pulmonary ventilation
● Air moves into the lungs when the air pressure inside the
lung is less then the air pressure in the atmosphere.
● Air moves out of the lung when the air pressure inside the
lung is greater than the air pressure in the atmosphere
● Inhalation- the air pressure inside the lungs is equal to the
air pressure in the atmosphere which at sea level is about
7600 mm Hg or one atm.
● For air to flow into the lung, the pressure inside the alveoli
must become lower than the atmospheric pressure this
condition is achieved by increasing the size of lung.

73. ● Exhalation – it is also due to pressure gradient but in this
case the gradient is in the opposite direction.
● The pressure in the lungs is greater than the pressure in
the atmosphere
● Normal exhalation during quite breathing unlikely inhalation
it is a passive process because no muscular contraction are
involved.
● Exhalation result from elastic recoil of the chest wall and
lung both of which have a natural tendency to spring back
after they have been stretched

75. Factor affecting pulmonary ventilation
● Surface tension of alveolar fluid.
● Compliances of the lung.
● Airway resistance.

76. EXCHANGE OF GASES
• Inhaled oxygen enters the lungs and reaches the
alveoli. The layers of cells lining the alveoli and the
surrounding capillaries are each only one cell thick and
are in very close contact with each other.
• Oxygen passes quickly through air-blood barrier
into the blood in the capillaries.
• Similarly, carbon dioxide passes from the blood
into the alveoli and is then exhaled.

77. • Diffusion of oxygen & carbon dioxide depends on
pressure differences.
• DIFFUSION OF GASES
• External respiration
• External respiration refers to gas exchange across the
respiratory membrane in the lungs.
• Each alveolar wall is one cell thick and sourrounded by a
network of tiny capillaries.
• Carbon dioxide diffuses from venous blood down its
concentration gradient into the alveoli.
• By the same process, oxygen diffuses from the alveoli into
the blood.

78. Internal respiration
• Internal respiration refers to gas exchange across the respiratory
membrane in the metabolizing tissues, like your skeletal muscles,
for example.
• Blood arriving at the tissues has been cleansed of it’s CO2 &
saturated with O2 during it’s passage through the lungs therefore
has a higher O2 & lower CO2 than the tissues.
• This concentration gradients between capillary blood and the
tissues lead gases exchange.
• O2 diffuses from the bloodstream through the capillary
wall into the tissues.
• CO2 diffuses from the cells into the extracellular fluid then into
the bloodstream towards the venous end of capillary.

79. • Transport of blood oxygen & carbon dioxide is essential for
internal respiration to occur.
• OXYGEN
• Oxygen is carried in the blood in as combination
with haemoglobin as oxyhaemoglobin.
• CARBON DIOXIDE
• It is excreted by the lungs & transported by combined with
haemoglobin as carbaminohaemoglobin.
• CONTROL OF RESPIRATION
• The respiratory centre: Medulla oblongata

80. Thank you