The Respiratory System
by
Dr. Ghizal Fatima
ERA UNIVERSITY,
LUCKNOW, INDIA
ghizalfatima8@gmail.com

 The respiratory system consists of all the organs
involved in breathing.
 These include the
nose, pharynx, larynx, trachea, bronchi & lungs.
 The respiratory system does two very important
things:
 it brings oxygen into body, which we need for
our cells to live and function properly;
 and it helps us get rid of carbon dioxide, which is
a waste product of cellular function.
The respiratory system

Tips for short learning
 Breathing is the process that brings oxygen in
the air into lungs and moves oxygen through out
body.
 lungs remove the oxygen and pass it through
our bloodstream, where it's carried off to the
tissues and organs that allow us to walk, talk,
and move.
 lungs also take carbon dioxide from blood and
release it into the air when we breathe out.

 The SINUSES are hollow spaces in the bones of your head. Small
openings connect them to the nasal cavity.
 The sinuses help to regulate the temperature and humidity of air
your breathe in, as well as to lighten the bone structure of the head
and to give tone to your voice.
 The NASAL CAVITY (nose) is the best entrance for outside air into
your respiratory system.
 The hairs that line the inside wall are part of the air-cleansing
system.
 Air can also enters through ORAL CAVITY (mouth), especially if
you have a mouth-breathing habit or your nasal passages may be
temporarily blocked.

 The ADENOIDS are overgrown lymph tissue at the top
of the throat. When adenoids interfere with breathing,
they are sometimes removed.
 The lymph system, consisting of nodes (knots of cells)
and connecting vessels, carries fluid throughout the
body.
 This system helps body resist infection by filtering out
foreign matter, including germs, and producing cells
(lymphocytes) to fight them.
 The TONSILS are lymph nodes in the wall of
pharynx. Tonsils are not an important part of the germ-
fighting system of the body. If they become infected,
they are sometimes removed.

 The PHARYNX (throat) collects incoming air
from nose and passes it downward to trachea
(windpipe).
 The EPIGLOTTIS is a flap of tissue that guards
the entrance to trachea. It closes when anything is
swallowed that should go into the esophagus and
stomach.
 The LARYNX (voice box) contains vocal cords.
When moving air is breathed in and out, it creates
voice sounds.

 The ESOPHAGUS is the passage leading from mouth and
throat to stomach.
 The TRACHEA (windpipe) is the passage leading from
pharynx to the lungs.
 The RIBS are bones supporting and protecting chest cavity.
They move a small amount and help the lungs to expand and
contract.
 The trachea divides into the two main BRONCHI (tubes),
one for each lung.
 The bronchi, in turn, subdivide further into bronchioles.

 The RIGHT LUNG is divided into three LOBES, or
sections.
 The left lung is divided into two LOBES.
 The PLEURA are the two membranes that surround each
lobe of lungs and separate the lungs from chest wall.
 The bronchial tubes are lined with CILIA (like very small
hairs) that have a wave-like motion.
 This motion carries MUCUS (sticky phlegm or liquid)
upward and out into the throat, where it is either coughed
up or swallowed.
 The mucus catches and holds much of the dust, germs,
and other unwanted matter that has invaded lungs.
 lungs get rid of the mucus through coughing.

 The DIAPHRAGM is the strong wall of muscle that separates
chest cavity from abdominal cavity. By moving downward, it
creates suction to draw in air and expand the lungs.
 The smallest section of the bronchi are
called BRONCHIOLES, at the end of which are the alveoli
(plural of alveolus).
 The ALVEOLI are the very small air sacs that are the
destination of air that you breathe in.
 The CAPILLARIES are blood vessels that are imbedded in
the walls of the alveoli.
 Blood passes through the capillaries, brought to them by
the PULMONARYARTERY and taken away by
the PULMONARY VEIN.
 While in the capillaries, the blood moves carbon dioxide into
the alveoli and takes up oxygen from the air in the alveoli.

 The nose, pharynx, larynx, trachea and bronchi all
work like a system of pipes through which the air is
funnelled down into lungs.
 There, in very small air sacs called alveoli, oxygen is
brought into the bloodstream and carbon dioxide is
pushed from the blood out into the air.
 When something goes wrong with part of the
respiratory system, such as an infection
like pneumonia, it makes it harder for us to get the
oxygen we need and to get rid of the waste product
carbon dioxide.
 Common respiratory symptoms
include breathlessness, cough, and chest pain.

The Upper Airway and Trachea
 During breathing in, air enters body through nose or
mouth.
 From there, it travels down throat through the larynx
(or voicebox) and into the trachea (or windpipe)
before entering lungs.
 All these structures act to funnel fresh air down from
the outside world into body.
 The upper airway is important because it must
always stay open for you to be able to breathe.
 It also helps to moisten and warm the air before it
reaches lungs.

Morphology of the upper airways
 Nose:
 The nose is the external protuberance of an internal
space, the nasal cavity.
 It is subdivided into a left and right canal by a thin
medial cartilaginous and bony wall, the nasal septum.
 Each canal opens to the face by a nostril and into the
pharynx
 The floor of the nasal cavity is formed by the palate,
which also forms the roof of the oral cavity.

 The complex shape of the nasal cavity is due to
projections of bony ridges, the superior, middle, and
inferior turbinate bones from the lateral wall.
 The passageways thus formed below each ridge are
called the superior, middle, and inferior nasal meatuses.
 On each side, the intranasal space communicates with a
series of neighbouring air-filled cavities within
the skull (the paranasal sinuses) and also, via the
nasolacrimal duct, with the lacrimal apparatus in the
corner of the eye.
 The duct drains the lacrimal fluid into the nasal cavity.
 This fact explains why nasal respiration can be rapidly
impaired or even impeded during weeping: the lacrimal
fluid is not only overflowing into tears, it is also
flooding the nasal cavity.

 They clean, moisten, and warm the inspired air,
preparing it for intimate contact with the delicate
tissues of the gas-exchange area.
 During expiration through the nose, the air is dried and
cooled, a process that saves water and energy.
 Two regions of the nasal cavity have a different lining.
The vestibule, at the entrance of the nose, is lined
by skin that bears short thick hairs called vibrissae.
 In the roof of the nose, the olfactory bulb with its
sensory epithelium checks the quality of the inspired
air. About two dozen olfactory nerves convey the
sensation of smell from the olfactory cells through the
bony roof of the nasal cavity to the central nervous
system.

The pharynx
 For the anatomical description, the pharynx can be
divided into three floors.
 The upper floor, the nasopharynx, is primarily a
passageway for air and secretions from the nose to the
oral pharynx.
 It is also connected to the tympanic cavity of the
middle ear through the auditory tubes that open on
both lateral walls.

 The act of swallowing opens briefly the normally
collapsed auditory tubes and allows the middle ears to
be aerated and pressure differences to be equalized.
 In the posterior wall of the nasopharynx is located a
lymphatic organ, the pharyngeal tonsil.
 When it is enlarged it may interfere with nasal
respiration and alter the resonance pattern of the
voice.
 Air from the nasal cavity flows into the larynx, and
food from the oral cavity is routed to
the esophagus directly behind the larynx.
The epiglottis, a cartilaginous, leaf-shaped flap,
functions as a lid to the larynx and, during the act of
swallowing, controls the traffic of air and food.

The Lungs
 The lungs are paired, cone-shaped organs which take
up most of the space in our chests, along with the
heart.
 Their role is to take oxygen into the body, which we
need for our cells to live and function properly, and to
help us get rid of carbon dioxide, which is a waste
product.
 We each have two lungs, a left lung and a right lung.

 These are divided up into ‘lobes’, or big sections of
tissue separated by ‘fissures’ or dividers.
 The right lung has three lobes but the left lung has only
two, because the heart takes up some of the space in the
left side of our chest.
 The lungs can also be divided up into even smaller
portions, called ‘broncho-pulmonary segments’.
 These are pyramidal-shaped areas which are also
separated from each other by membranes. There are
about 10 of them in each lung. Each segment receives
its own blood supply and air supply.

Mechanism of breathing
 Air enters lungs through a system of pipes called the
bronchi.
 These pipes start from the bottom of the trachea as the
left and right bronchi and branch many times
throughout the lungs, until they eventually form little
thin-walled air sacs or bubbles, known as the alveoli.
 The alveoli are where the important work of gas
exchange takes place between the air and blood.

 Covering each alveolus is a whole network of
little blood vessel called capillaries, which are very
small branches of the pulmonary arteries.
 It is important that the air in the alveoli and the
blood in the capillaries are very close together, so
that oxygen and carbon dioxide can move (or
diffuse) between them.
 So, when you breathe in, air comes down the
trachea and through the bronchi into the alveoli.

 This fresh air has lots of oxygen in it, and some of this
oxygen will travel across the walls of the alveoli into
bloodstream.
 Travelling in the opposite direction is carbon dioxide,
which crosses from the blood in the capillaries into
the air in the alveoli and is then breathed out.
 In this way, you bring in to your body the oxygen that
you need to live, and get rid of the waste product
carbon dioxide.

Blood Supply
The lungs are very vascular organs, meaning
they receive a very large blood supply.
This is because the pulmonary arteries, which
supply the lungs, come directly from the right
side of your heart.

 They carry blood which is low in oxygen and high
in carbon dioxide into your lungs so that the
carbon dioxide can be blown off, and more oxygen
can be absorbed into the bloodstream.
 The newly oxygen-rich blood then travels back
through the paired pulmonary veins into the left
side of your heart.
 From there, it is pumped all around your body to
supply oxygen to cells and organs.

The Work of Breathing
 The Pleurae
 The lungs are covered by smooth membranes that we
call pleurae.
 The pleurae have two layers, a ‘visceral’ layer which
sticks closely to the outside surface of your lungs, and a
‘parietal’ layer which lines the inside of your chest wall
(ribcage).
 The pleurae are important because they help you
breathe in and out smoothly, without any friction.
 They also make sure that when your ribcage expands on
breathing in, your lungs expand as well to fill the extra
space.

The Diaphragm and Intercostal
Muscles
 When you breathe in (inspiration), your muscles need
to work to fill your lungs with air.
 The diaphragm, a large, sheet-like muscle which
stretches across your chest under the ribcage, does
much of this work.
 At rest, it is shaped like a dome curving up into your
chest. When you breathe in,
 the diaphragm contracts and flattens out,
 expanding the space in your chest and drawing air into
your lungs.

 Other muscles, including the muscles between your
ribs (the intercostal muscles) also help by moving
your ribcage in and out.
 Breathing out (expiration) does not normally require
your muscles to work.
 This is because lungs are very elastic, and when
muscles relax at the end of inspiration your lungs
simply recoil back into their resting position, pushing
the air out as they go.

Respiratory System
 Exchange of gases between the atmosphere and
the blood
 Homeostatic regulation of body pH
 Protection from inhaled pathogens and irritating
substances

Respiratory System
Overview of external and cellular respiration
Figure 17-1

Figure 17-2a
Respiratory System

Figure 17-2b
Muscles Used for Ventilation

Figure 17-3
The Respiratory System
The relationship between the pleural sac and the lung

Figure 17-2e
Branching of Airways

Figure 17-2g
Alveolar Structure

Pulmonary Circulation
 Right ventricle  pulmonary trunk  lungs 
pulmonary veins  left atrium
Animation: Respiratory System: Anatomy ReviewPLAY

Figure 17-9a
Movement of the Diaphragm

Figure 17-9b
Movement of the Diaphragm

Figure 17-9c
Movement of the Diaphragm

Figure 17-10a
Movement of the Rib Cage during
Inspiration

Summary
 Respiratory system
 Cellular respiration, external respiration, respiratory
system, upper respiratory tract, pharynx, and larynx
 Lower respiratory tract, trachea, bronchi, bronchioles,
alveoli, Type I and Type II alveolar cells
 Diaphragm, intercostal muscles, lung, pleural sac, and
plural fluid