Johny's A&P structure and function of respiratory system
Mr. Johny Kutty Joseph
Asstt. Professor, SMVDCoN
The respiratory system is the set of organs that
allows a person to breathe and exchange oxygen
and carbon dioxide throughout the body.
The integrated system of organs involved in the
intake and exchange of oxygen and carbon
dioxide between the body and the environment
and including the nasal passages, larynx, trachea,
bronchial tubes, and lungs.
The respiratory system performs two major tasks
such as external respiration (exchanging air
between the body and the outside environment)
and internal respiration (exchange of air from
The respiratory system is divided into upper
respiratory tracts and lower respiratory tracts.
The organs of upper respiratory tracts are located
outside the thorax whereas the lower are located
The upper respiratory tract is composed of nose,
nasopharynx, oropharynx, laryngipharynx, and
The lower respiratory tracts consist of trachea,
bronchial tree and lungs.
The nose has two structures/ nares such as
internal and external nares.
The external part is protruding from the face and
is divided into two halves by the nasal septum.
Contains the paranasal sinuses where air is
warmed. Paranasal sinuses are a group of paired
air-filled spaces that surround the nasal cavity.
The maxillary sinuses are located under the eyes;
the frontal sinuses are above the eyes; the
ethmoidal sinuses are between the eyes and the
sphenoidal sinuses are behind the eyes.
The Nares also contains cilia which is responsible
for filtering out foreign bodies.
Paranasal air sinuses
The maxillary sinuses:
under the eyes; frontal
sinuses: above the eyes;
the ethmoidal sinuses :
between the eyes and the
sphenoidal sinuses :
behind the eyes.
The functions are
decreasing weight of
resonance of the voice,
heating air and
• The internal nose lies over the roof of the mouth.
The palate separates mouth and nose.
• The roof of nose is separated from the cranial
cavity by a portion of ethmoid bone called
cribiform plate. The olfactory nerves enter
through opening on cribiform plate.
• The air pass further to nasal mucous membrane.
This is made of ciliated columnar epithelium rich
in goblet cells. The olfactory epithelium which
contains olfactory nerves. This lining is further
extended to bronchial tree.
• In addition to olfactory neurons the nasal mucosa
is also imbedded with a structure called VNO
(Vomero Nasal Organ). This helps in sensing sex
signaling chemicals called pheromones.
• Filtration , warmth, moistened, and chemical
screening is done by nose and paranasal air
• The hollow sinus also helps in decreasing the
weight of the skull.
• The pharynx (plural: pharyng
es) is the part of
the throat that is behind
the mouth and nasal
cavity and above
the oesophagus and
• The pharynx has three
• The nasopharynx, is the
upper portion of the pharynx
extends from the base of
the skull to the upper surface
of the soft palate.
• It includes the space
between the internal
nares and the soft palate and
lies above the oral cavity.
The auditory tube is
connected to middle ear
through the pharyngeal
opening of the auditory
tube. The opening and
closing of the auditory tubes
serves to equalize the
barometric pressure in the
middle ear with that of the
• The pharyngeal
tonsils are located in
• The oropharynx lies
behind the oral
from the uvula to the
level of the hyoid
bone. Uvula prevents
the entry of food into
nasal cavity. The
palatine tonsils are
• The laryngopharynx, also known as
hypopharynx, is the caudal part of the pharynx;
it is the part of the throat that connects to the
esophagus. It lies inferior to the epiglottis and
extends to the location where this common
pathway diverges into the respiratory (larynx)
and digestive (esophagus) pathways.
• The pharynx serve as common pathway for the
respiratory and digestive tracts.
Voice box is a short,
airway starts from the root
of the tongue and ends in
Located between third and
sixth cervical vertebrae.
materials from entering the
lower respiratory tract.
Conducts air into the lower
respiratory tract and
It is triangle shaped
It consists of cartilages and
attached to one another by
It is lined by ciliated
The mucous membrane
forms folds laterally and
inferiorly which is called ac
Nine cartilages forms
Three Thyroid cartilages:
largest cartilage of larynx, its
gives the triangular shape.
The anterior laryngeal
eminence formed by thyroid
cartilage is called Adam’s
Apple. It is larger in men
(fat deposition) and lesser in
The cricoid cartilages: they
are singe paired structures
such as Arytenoid cartilage
(Pyramid shaped & attached
to vocal folds), corniculate
and cuneiform cartilages.
One epiglottis: a small leaf shaped cartilage attached
to thyroid cartilage and has free superior border and it
prevents the entry of food and liquids into trachea.
Larynx has two types of muscles such as intrinsic
muscles (they originate and insert in larynx. They
regulate length, tension and shape of laryngeal inlet.)
and extrinsic muscles( this helps in the movement of
larynx such as in respiration vocalization and
Larynx helps in purification of air from dust,
It prevents the food and liquid entry to lungs.
It is the voice box. The vibration of vocal folds creates
The trachea is a flexible tube
also called windpipe.
It is 11cm long and extend
from larynx to primary
Extends through the
mediastinum and lies anterior
to the esophagus and inferior
to the larynx.
Cartilage rings reinforce and
provide rigidity to the
tracheal wall to ensure that
the trachea remains open at
level of the sternal
angle, the trachea
bifurcates into two
smaller tubes, called
the right and left
laterally toward each
The trachea is lined by
consists of ciliated
Bronchi and Alveoli
The trachea divides into
two primary bronchi.
Each primary bronchus
divides into secondary
and tertiary bronchi.
It further divides into
This together called as
The right primary
bronchus divides into
three secondary bronchi
such as to supply three
lobes. The left branch
divides into two
Bronchi and Alveoli
divide into alveolar
ducts which ends in
300 million alveoli are
estimated to be in the
The alveoli has a
sponge like structure
and are the primary gas
Bronchi and Alveoli
which is in contact
capillaries and gas
place across the
Each alveoli is
Thus the purified air
enters blood stream.
The lungs are cone shaped
organs large enough to fill
the pleural portion of
They extend from clavicle
The medial surface of each
lung is concave to occupy
the organs of mediastinum.
The root of lung consist of
pulmonary vessels and
bronchi which is connected
by a connective tissue and
it enters medially through
the space called hilum.
Functions of Lungs
The left lung has a
concavity called cardiac
notch where the apex of
the heart lies.
Air distribution to the
alveoli is the function of
the tubes of the
Gas exchange between
air and blood is the joint
function of the
capillaries and alveoli.
They have enormous
surface area which is
called as respiratory
Each lung is
divided into lobes
The left lung is
The right lung is
and inferior lobes.
The lobes are
further divided into
The outer surface of each lung and the adjacent
internal thoracic wall are lined by a serous
membrane called pleura.
The outer surface of each lung is tightly covered
by the visceral pleura.
while the internal thoracic walls, the lateral
surfaces of the mediastinum, and the superior
surface of the diaphragm are lined by the
The parietal and visceral pleural layers are
continuous at the hilus of each lung
The potential space between the serous
membrane layers is a pleural cavity.
The pleural membranes produce a thin, serous
pleural fluid that circulates in the pleural cavity
and acts as a lubricant, ensuring minimal friction
Pleural fluid is a serous fluid produced by the
serous membrane covering normal pleurae.
Most fluid is produced by the parietal
circulation (intercostal arteries) via bulk flow
and reabsorbed by the lymphatic system.
Rhinitis: Inflammation of nasal mucosa
Pharyngitis: Inflammation of Pharynx.
Laryngitis: Inflammation of Larynx.
Tonsilitis: Inflammation of tonsils:
Sinusistis: Inflammation of air sinus
Deviated nasal septum: obstruction due to
anatomical defect: septoplasty.
Bronchitis: Inflammation of Bronchi.
Pneumonia: Inflammation of lung paranchyma.
Tuberculosis: Infection by bacteria.
Lung Cancer: malignancy: Lobectomy
Muscles of Respiration
The muscles of respiration are those muscles
that contribute to inhalation and exhalation by
aiding in the expansion and contraction of the
The diaphragm and, to a lesser extent, the
intercostal muscles drive respiration during
Additional 'accessory muscles of respiration' are
typically only used under conditions of high
metabolic demand (e.g. exercise) or respiratory
dysfunction (e.g. an asthma attack).
• It is the major muscle responsible for breathing.
• It is a thin, dome-shaped muscle that separates the
abdominal cavity from the thoracic cavity.
• During inhalation, the diaphragm contracts, so that
it's centre moves downward and its edges move
upward. This compresses the abdominal cavity, and
expands thoracic cavity. This draws air into the lungs.
• When the diaphragm relaxes, elastic recoil of the
thoracic wall causes the thoracic cavity to contract,
forcing air out of the lungs.
• The diaphragm is also involved in non-respiratory
functions, helping to expel vomit, feces, and urine
from the body by increasing intra-abdominal
• Along with the diaphragm, the intercostal muscles
are one of the most important groups of
• These muscles are attached between the ribs and
are important in manipulating the width of the rib
• External intercostal muscles aid in quiet and
• Internal intercostal muscles aid in forced
• The innermost intercostal muscle is a layer of
intercostal muscles deep to the plane that contains
the intercostal nerves and intercostal vessels. It
does not have a direct role in respiration.
• "Accessory muscles" refers to muscles that assist,
but do not play a primary role, in breathing.
• The sternocleidomastoid (a paired muscle in the
superficial layers of the side of the neck) helps in
• The scalene muscles (group of three pairs of
muscles in the lateral neck, namely the anterior
scalene, middle scalene, and posterior scalene) also
help in respiration.
• They are typically considered accessory muscles of
• Other muscles of neck and chest also support