Respiratory System

Respiratory system having specific organs and structure which

are essential for the respiration
 Respiration – Inhalation + Expiration
 Inhalation – The passage of air into the lung to supply the
body with O2.
 Expiration - The passage of air out of the lungs to expel CO2.
 Respiratory system includes Nose, Nasopharynx, Larynx, Trachea,
Bronchus, Bronchioles, Alveoli, Lungs and Diaphragm.

The Nose
 It has 2 parts - External nose & Nasal cavity
1. External nose – Made by Nasal bone, maxillary
bone & Cartilage
2. Nasal cavity –
 It extends from external nostrils to the pharynx
 Nasal cavity is divided into right & left half by
nasal septum
 Nasal septum made by ethmoid bone,
Vomer bone & Septal Cartilage

 Function –
1. Respiration
2. Smell
3. Acts as an air conditioner – It warms, cools and clean the air
before enters into the lungs

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 Nasopharynx
 Upper part of the pharynx located behind
the nasal cavity
 Relations - Anteriorly - Nasal cavity
Posteriorly - Atlas
Inferiorly - Oropharynx

The Larynx (Voice box)

 It is a organ for the production of voice
 Location – Middle of the neck
Present b/w tongue and trachea
Extends from C3 to C6
 Length – 44 mm in males & 36 mm in females
 It also allows an air passage to the lower respiratory tract
 Made up of 9 cartilages - 3 unpaired & 3 paired (6)

Unpaired cartilages – Thyroid, Cricoid & Epiglottic

Paired cartilages – Arytenoids (2), Corniculate (2) &
Cuneiform (2)

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o Thyroid cartilage –
o “V” shaped cartilage on cross section
o Having right & left lamina
o Each lamina having anterior and posterior
borders
o Lower part of the anterior borders of
lamina fuse to form “laryngeal
prominence”
o The upper part of the anterior borders of
lamina are separated by “thyroid notch”
o Posterior borders are free
o Posterior borders are extended upwards
(superior horn) and downwards (inferior
horn)
o Superior horn connected to hyoid bone
o Inferior horn connected to Cricoid cartilage

o Cricoid cartilage –
o Ring shaped cartilage
o Thicker and stronger then thyroid cartilage
o Ring has
 Narrow anterior part – Arch
 Broad posterior part – Lamina – Superiorly
articulates with arytenoids cartilage.
Thyroid cartilage articulates with side of
the posterior part of the Cricoid cartilage

o Epiglottic cartilage / Epiglottis –

o Leaf shaped cartilage
o Location – Anterior wall of the upper part of
the larynx
o Upper end is broad & free
o Lower end is pointed & attached to the upper part of thyroid
cartilage
o Anterior surface attached to tongue and hyoid bone

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o Arytenoids cartilage -
o Pair of small pyramid shaped
cartilage
o Location – Upper border of the
posterior part of the Cricoid
cartilage
o Apex articulates with
Corniculate cartilage
o Base articulates with Cricoid
cartilage

o Corniculate cartilage –
o Pair of small conical nodules
o Articulates with apex of the arytenoids cartilage

o Cuneiform cartilage –
o Pair of rod shaped cartilage
o Location – Just ventral to the
Corniculate cartilage

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 The Trachea (Wind pipe)
 It is a wide pipe located lower & middle part of
the neck
 Made by “C” shaped cartilage, posteriorly trachea
is made by muscle which allows expansion of
oesophagus
 Length - 10 to 15 cm long & 2 cm in diameter
 Extends - It extend from C6 to T4
 It has 2 ends –
 Upper end – Present in cervical region
At the level of C6
 Lower end – Present in thoracic region
At the level of T4 vertebrae
 At the level of T4 the trachea is divided into
“Right and Left principal bronchus”.

 Relations – Anteriorly – Thyroid gland &

Manubrium sterni
Posteriorly – Oesophagus & Vertebral column
Right side – Right lobe of the
thyroid gland & Right lung
Left side – Left lobe of the
thyroid gland & Left lung
 Blood supply - “Bronchial artery”
“Brachiocephalic vein”
 Nerve supply – “Recurrent laryngeal”

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 Bronchial Tree
1. At the level T4 the trachea is divided into
right (2.5cm long) and left (5cm long)
“principal bronchi”.
2. Each principal bronchus enters the lung
through the “hilum” (root of the lung) and
divided into “lobar bronchi” one for each

lobe of the lungs.

3. As the right lung having 3 lobes, there
are 3 lobar bronchi on the right side
and only 2 on the left side (left lung
having 2 lobes).
4. Each lobar bronchus divided into
“segmental bronchi” one for each
bronchopulmonary segment – 10
segments on each lung.
5. The segmental bronchi divide
repeatedly to form “terminal bronchioles” then “respiratory
bronchioles” finally ends by opening into the “alveoli” for
exchange of gases.

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 The Lungs
 A pair of respiratory organs
 Location – Thoracic cavity
 Color – Brown in color, gradually they become spotted black
 Shape – Conical
 Weight – Right lung – 700g
Left lung – 600g
 Texture (feel) – Spongy in texture
External features:
 Apex – Blunt & 2.5cm above the
level of clavicle
 Base – Concave & Resting on the
diaphragm
 3 Borders – Anterior, Posterior &
Inferior borders
 2 Surfaces – Costal & Medial surfaces
Lobes –
 Right lung having 3 lobes – Upper, Middle &
Lower
 Left lung having 2 lobes – Upper & Lower

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Root of the Lung: (Hilum)
 This is an area present on medial surface
of the lung through which structures enter
the lung and leaves the lung.
 Contents –
1. Principal Bronchus
2. Bronchial arteries
3. Bronchial veins
4. Lymphatic vessels
5. 2 Pulmonary veins
6. 1 Pulmonary artery

Arterial supply –
Bronchial arteries
Venous drainage –
Bronchial veins
Nerve supply - Vagus nerve

Difference b/w Right & Left Lung:

Right Lung Left Lung
2 fissures Only one fissure
3 Lobes 2 Lobes
Heavier Lighter
Shorter & Broader Longer & Narrower
Cardiac notch is
Straight anterior
present on anterior
border
border

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Bronchopulmonary Segments:
Each lung has 10 Bronchopulmonary segments and each
segment is aerated by a segmental bronchus.

Right Lung Left Lung

Lobes Segments Lobes Segments
Apical Apical
Upper Posterior Posterior
Anterior Upper Anterior
Medial Superior lingular
Middle
Lateral Inferior lingular
Superior Superior
Anterior basal Anterior basal
Lower Lateral basal Lower Lateral basal
Medial basal Medial basal
Posterior basal Posterior basal

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 Pleura
There are 2 pleural sacs (bag) on either side of the
mediastinum. Each pleural sac is invaginated from its medial side
by the lung, so that it has –
1. Outer Parietal Pleura
2. Inner Visceral Pleura
1. An outer Parietal pleura
 Thick layer
 Attached to chest wall
 It has 4 divisions – Cervical
Costal
Diaphragmatic
Mediastinal
2. An inner Visceral pleura–
 Thinner than parietal layer
 Tightly attaches to the lung except at the hilum.

 The gap present between parietal and visceral pleura is called

“Pleural cavity”
 Normally pleural cavity contains a small amount of pleural fluid,
but in some diseases the cavity may filled with –
 Air – Pneumothorax
 Blood – Hemothorax
 Fluid – Pleural effusion
 Pus – Empyema
Blood supply – Bronchial artery
Internal thoracic artery
Venous drainage by Azygos vein
Nervous supply – Phrenic nerve

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 The Diaphragm
(In Greek – Partition)
 It is a dome shaped musculotendinous organ
 It separates thoracic cavity from the
abdomen
 Function – Respiration
Origin: The muscle fibers of diaphragm are
grouped into 3 parts – Sternal, Costal & Lumbar
 Sternal part - Originated from the back of the
“xiphoid process”.
 Costal part - Originated from the inner
surface of the lower 6 ribs & cartilages.
 Lumbar part - Originated from the “lumbar vertebrae” as
“right & left Crus”.
Insertion: All these muscle fibers
inserted into “central tendon” which
is located below the pericardium.
Openings of the Diaphragm:
1. Aortic opening
2. Oesophageal opening
3. Venacaval opening
4. Small openings for nerves & blood vessels
Relations:
Superiorly – Pleura, Lungs, Pericardium & Heart
Inferiorly – Liver, Stomach, Spleen & Kidneys
Blood supply – Phrenic arteries & veins
Nervous supply – Phrenic nerves

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 Respiratory Muscles & Moments
The lung expands during inhalation and retracts during
expiration. The following list of organs responsible for this act.

Muscles of respiration (Inhalation & Expiration):

 Diaphragm  Pectoralis minor
 Intercostal muscles  Muscles of the abd. wall
 Sternocleidomastoid  Latissimus dorsi

Movements of Respiration:
1. Quite Inhalation:
 Done by the diaphragm & intercostal muscles
 The anteroposterior & transverse diameter of the thorax is
increased.

2. Forced Inhalation:
 Done by the diaphragm, intercostal muscles,
Sternocleidomastoid and Pectoralis minor
 All the movements described above are exaggerated (amplify).

3. Quite Expiration:
 Done by elastic recoil of the pulmonary alveoli and thoracic
wall.

4. Forced Expiration:
 Done by the strong contraction of abdominal muscles &
Latissimus dorsi.

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 Paranasal Sinuses
These are air filed spaces present within some bones around
the nasal cavity. All these are opens into the nasal cavity.
Function - To make the skull lighter and add resonance to the voice
1. Frontal Sinus
2. Ethmoidal Sinus
3. Maxillary Sinus
4. Sphenoidal Sinus
1. Frontal Sinus – (above the eyes)
 A pair of sinuses lies in the frontal
bone
 Right & Left sinuses are unequal in
size
 Absent at birth

2. Ethmoidal Sinus – (between the eyes)

 These are numerous small spaces
 Lies within the ethmoidal bone

3. Maxillary Sinus – (below the eyes)

 Lies in the maxillary bone

4. Sphenoidal Sinus - (behind the eyes)

 A pair of sinuses lies within the
sphenoid bone
 Right & Left sinuses are equal in size

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