The Respiratory System And Function

The Respiratory System

The vast majority of this
vitality is gotten from substance responses which can just happen within the
sight of oxygen (O.). The primary waste result of these responses is carbon
dioxide (CO).
The Respiratory System And Function

The respiratory framework gives the
course by which the inventory of oxygen present in the air picks up the passage
to the body and it gives the course of discharge. The state of the climatic air
entering the body differs significantly as indicated by the outside condition,
for example, It might be dry, cold and contain dust particles or it might be
clammy and hot.
As the air taken in travels through the
air entries to come to the lungs, it is warmed or cooled to internal heat
level, soaked to get immersed with water fume and cleaned as particles of
residue adheres to the bodily fluid which covers the coating Blood gives the
transport framework to these gases between the lungs and the cells of the body.
The exchange of gases between the blood and the lungs is called
external respiration and that between the blood and cells is called internal
The organs of the respiratory
system are:

  1. Nose

  2. Pharynx

  3. Larynx

  4. Trachea

  5. Bronchi

  6. Alveoli


The nasal cavity is the first of the
respiratory organs. The posterior bony part of the septum is formed by
the perpendicular plate of the ethmoid bone interiorly it consists of hyaline
cartilage. The hard palate is composed of the maxilla and palatine bones
and the soft palate consists of involuntary muscle.

Function Of Nose

The function of the nose is to start the
process by which the air is warmed, moistened, and filtered. The projecting
conchae, increase the surface area and cause turbulence spreading inspired over
the whole nasal surface. The large surface area maximizes warming,
humidification, and filtering
Filtering and cleaning of air – Smaller particles such as dust and microbes
settle and adhere to the mucus. Mucus protects the underlying epithelium from
irritation and prevents drying.
Humidification – This occurs as air travels over
the moist mucosa and becomes saturated with water vapor.

2. Pharynx
  • Superiorly -The inferior surface of the base of the skull.
  • Inferiorly -It is continuous with the esophagus
  • Interiorly -The wall is incomplete with the esophagus
  •  Posterior – Areolar tissue,
    involuntary muscle and the bodies of the first six cervical vertebrae.

The Nasopharynx

On its lateral wall are the two openings of the auditory tubes,
one leading to each middle ear. On the posterior wall, there are the pharyngeal
tonsils (adenoids), consisting of lymphoid tissue. They are most prominent in
children up to approximately 7 years of age.

Function Of Pharynx

A passageway for air and food

The pharynx is an organ
involved in both the respiratory and digestive systems; air passes through the
nasal and oral parts and food through the oral and Functions laryngeal parts.


The pharynx functions in
a speech by acting as a resonating chamber for the sound g from the larynx, it
helps to give the voice its individual characteristics.

3. Larynx

The larynx
or voice box stretches out from the foundation of the tongue and the hyoid of the issue that remains to be worked out trachea. It lies before the laryngopharynx
at the degree of the third, fourth, fifth, and 6 cervical vertebrae.


The thyroid cartilage is incomplete
posteriorly and the posterior border of each lamina is extended to form two processes called the superior and inferior corny.

  •  Superiorly
    – The hyoid bone and the root of the tongue
  • Inferiorly  –  It is continuous with
  • Anteriorly –  The muscle attached to the
    hyoid bone and the muscle of the neck.
  • Posteriorly –  The laryngopharynx and
    3″ and 6 cervical vertebrae.
  • Laterally     –  The lobes of
    the thyroid gland


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 cricoids cartilage
2 arytenoids cartilages hyaline cartilage
1 epiglottis elastic fibrocartilage.

The Thyroid Cartilage

The thyroid cartilage is incomplete posteriorly and the
posterior border of each lamina is extended to form two processes called the
superior and inferior cornu. The upper part of the thyroid cartilage is lined
with stratified squamous epithelium like the larynx, and the lower part with
ciliated columnar epithelium like the trachea. There are many muscles attached
to its outer surface. 

The Cricoid Cartilage

The broad posterior part articulates with ciliated columnar
epithelium and there are muscles and ligaments attached to its outer surface.
The lower border of the cricoid cartilage marks the end of the upper
respiratory tract.

Function Of Larynx

Production of Sound

Sound has the properties of the pitch, volume, and
reverberation. The Pitch of the fed like aloe depends upon the length and
tightness of the cords. The volume of the voice depends upon the force with
which the cords vibrate.


trachea or windpipe is a continuation of a larynx and extends up to the level
of the 5th thoracic vertebrae where it divides into left and right bronchus. One of the bronchi is going to each lung.

 It is 10-13 cm long and 2.5 cm in diameter and
lies in front of the esophagus. The cartilages are incomplete posteriorly and
consist of mucous membrane unsupported by cartilage. The functions of the rings
of cartilage are to keep the windpipe permanently open so that its walls don’t


The two bronchi are formed when the trachea divides into two main
bronchi(right and left) opposite to the level of T5. the right bronchus is a
winder shorter about 25 cm long and it lies move vertically to the midline. the
right bronchus after entering the right lung at the Hilum.
 It divides into three branches.
1. Superior
2. Middle
3. Inferior

The right branches longer to 5 cm long it lies more oblique to the
midline after entering the lungs each branch then subdivides
into smaller branches.


The alveoli are closely invested with a network of capillaries.
The exchange of gases during respiration takes place across the two membranes the
alveolar membrane and the capillary membrane.


There are two lungs on each side of the midline in the thoracic
cavity. The area between the two lungs is the mediastinum occupied by the heart
great vessels, trachea, right and left bronchioles, esophagus, lymph node,
lymph vessels, and nerves.
The lungs are cone shape and are described as having an apex and a
base two surfaces.

1. Costal Surface
2. Medial Surface

apex is rounded and extended up to the root of the neck for about 1 inch above
the mid clavicle. The base is concave and semilunar in shape and is related to
the upper surface of the diaphragm. The costal surface is concave and has a
roughly triangular-shaped area called Hilum or Hilus at the level of 5,6 and 7
thoracic vertebrae.

Cycle Of Respiration


1. Inspiration

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 and diaphragm.

This stretches the lungs and the pressure
within the alveoli and in the air, passages fall drawing air into the lungs in
an attempt to equalize the atmospheric and alveolar air press The process of
inspiration is active as it requires the expenditure of energy for muscle
contraction The negative pressure created in the thoracic cavity aids venous
return to the heart as the respiratory pump.

2. Expiration

As this occurs, the pressure inside the lung exceeds that in the
atmosphere and therefore air is expelled from the respiratory tract. The lung
still contains some air and is prevented from complete collapse by the intact
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