Human respiratory system

HUMAN RESPIRATORY SYSTEM
JAI NARAIN VYAS UNIVERSITY, JODHPUR
ASSISTANT PROFESSOR:-ASHWIN SINGH CHOUHAN
DEPARTMENT:- PHARMACOLOGY
E-MAIL:- anshukavya1993@gmail.com

RESPIRATORY SYSTEM
ASC JNVU PHARMACY, JODHPUR
The primary function of the respiratory system is to oxygenate the
blood enabling the supply of oxygen to all parts of the body. It is a
complex process involving multiple organs at micro and macro levels.
This chapter describes the anatomy and physiology of the human
respiratory system. A brief description of respiratory volume
parameters, Lung cancer, pulmonary nodules and its causes,
similarities and differences between benign and malignant nodules
are presented. The purpose of the CAD tool being proposed in the
thesis is to identify the morphological changes that happen in the
lungs and correlate them for identification and classification of
abnormalities resulting in lung cancer. Such a tool necessitates the
understanding of the anatomy of the system being diagnosed and in
this thesis lungs are considered.

Cells of the body require oxygen for the oxidation of food materials to
obtain energy. CO2 is released as a result of cellular respiration which
combines with water to form carbonic acid. Carbonic acid will lower
the blood pH , so CO2 must be eliminated from the body. Breathing
in and breathing out of air is known as respiration. Respiration
includes Ventilation (or) breathing: Flow of air into and out of lungs.
External respiration: Exchange of air in alveoli and blood in
pulmonary capillaries. Transport of gas: Transport of gas by blood
between lungs and tissues. Internal respiration: Exchange of air or
gas between the blood in systematic capillaries and tissue cells.
FUNCTIONS OF RESPIRATION
 Exchange of O2 and CO2 .
 Maintenance blood PH by eliminating CO2. 41
 Maintains temperature of the body by removing some heat through
exhaled air.
 Respiration draws blood from inferior parts of the body to
abdomen.

PRINCIPAL ORGANS OF
RESPIRATORY SYSTEM

THE RESPIRATORY SYSTEM IS DIVIDED INTO TWO
DIVISIONS
Conducting division contain thick walls (no gas exchange to
capillaries) and including the nasal cavities, pharynx, larynx, trachea,
bronchi, and bronchioles.
Respiratory division containing thin walls (permitting gas exchange
to blood capillaries) and including respiratory bronchioles, alveolar
ducts, artia (space from which the alveoli of the sacs arise), and
alveolar sacs.

NOSE
The nose is divided into two parts, external nose and internal nose.
External nose External nose is formed by bones and hyaline
cartilage. The two openings of external nose are called nostrils.
Internal nose It consists of large cavity known as nasal cavity.
Nasal septum divides the nasal cavity into right and left halves. Roof
of the nasal cavity is formed by – sphenoid, ethmoid, frontal and
nasal bones. Floor of the nasal cavity is formed by a hard palate
which contains Palatine bones. Lateral walls of the nasal cavity are
formed by Marilla, ethmoid and inferior nasal conchae. Air filled
cavities called paranasal sinuses opens into nasal cavity.
FUNCTIONS OF NOSE
 Warming of air close to body temperature.
 Mucous secreted by goblet cells trap the dust particles.
 Olfactory epithelium detects the olfactory stimuli.
 Paranasal sinuses act as resonance chambers for speech.

PHARYNX
It is also known as throat. It lies behind the nasal cavity, oral
cavity and larynx. It is divided into three parts.
1. Nasopharynx It is present behind the nasal cavity. Nasal
cavity opens into nasopharynx through two openings known as
internal nares.
2. Oropharynx It lies behind the oral cavity. It contains palatine
and lingual tonsils.
3. Laryngopharynx It is present behind the larynx.
FUNCTIONS OF PHARYNX
 Used for both respiration and digestion.
 Tonsils protect against microbes.
 Humidify the warm and humid air from the nose.
 It consists of olfactory nerve endings which provide taste.

LARYNX
It is also called the voice box. It is a tube like structure supported by
cartilages. It consists of following cartilages
a) Thyroid cartilage It is the largest cartilage. It is formed by two
broad plates of nyalin cartilage which are fused incompletely. It
forms the ventral and lateral walls.
b) Cricoid cartilage Behind the thyroid cartilage there is a ring like
structure called cricoid cartilage.
c) Arytenoids cartilage On the dorsal side of larynx a pair of
arytenoids cartilage is present.
d) Corniculate cartilage These are located above the each
arytenoids cartilage.
e) Cuneiform cartilage They are two in number and lie anterior to
circulate cartilage.
the Function of the Larynx
The respiratory and digestive systems separate at the larynx, making
it a vital organ in the function of both. Another primary function of
the voice box is producing sounds and speech.

EPIGLOTTIS
It arises from thyroid cartilage. Extending between thyroid and
arytenoids cartilage two fibroclastic strands called vocal cords are
present.
FUNCTIONS OF EPIGLOTTIS
Sound is produced due to vibrations of the vocal cords.
Acts as passage for air.
It filters, warm and humidifies the air.
TRACHEA
It is also called wind pipe. It is a thin walled tube that passes through
the neck on ventral side of oesophagus. It is supported by C-shaped
cartilagenous rings which are incomplete dosally. They keep the
trachea open. Histologically wall of trachea consists of Aaventitia and
Hyaline cartilage followed by sub mucosa and then mucosa.
FUNCTIONS OF TRACHEA
 Conduct air between larynx ad bronchi.
 C-Shaped rings prevent the collapse of trachea.

LUNGS
The lungs are a pair of cone shaped organs placed one on either side
within the thorax, and separated from each other by the heart and
other contents of the mediastinum. The substance of the lung is of a
light, porous, spongy texture; it floats in water, and crepitates when
handled, owing to the presence of air in the alveoli. it is also highly
elastic hence the retracted state of these organs when they are
removed from the closed cavity of the thorax. The surface is smooth,
shining, and marked out into numerous polyhedral areas, indicating
the lobules of the organ. Superior portion of lungs is known as apex
and inferior portion is known as base. Each lung is covered by double
layered peritoneum called pleural membrane. Outer layer is known as
parietal layer and inner layer is called visceral layer. Between the two
layers pleural cavity is 45 present which contains pleural fluid. Right
lung is divided into three lobes and left lung is divided into two lobes.
Inside each lung alveolar ducts ends in alveolar sacs. Each alveolar
sac is formed by alveoli. Each alveolus is lined by simple squamous
epithelium. Simple squamous epithelium of alveolus and one layer of
endothelium and their base membranes form respiratory membrane.

The main function of the lungs is the process of gas
exchange called respiration (or breathing). In respiration,
oxygen from incoming air enters the blood, and carbon
dioxide, a waste gas from the metabolism, leaves the blood.
A reduced lung function means that the ability of lungs to
exchange gases is reduced

ALVEOLI
The alveoli (alveolus, singular) are tiny round (balloon-like) sacs that
are connected to larger tubes of the lungs by tiny tubes known as
alveolar ducts and bronchioles. The alveoli are so small that there are
billions in adult lungs. This very small size produces a maximum
surface area through which external respiration takes place. External
respiration is the actual exchange of gases between the air in the
alveolar spaces and the adjacent blood capillaries through their walls.
The inner surfaces of the alveoli must be kept wet in order for this
transfer of gases to be possible
FUNCTION OF ALVEOLI
The function of the alveoli is to get oxygen into the blood
stream for transport to the tissues, and to remove carbon
dioxide from the blood stream.

BRONCHI AND BRONCHIOLES
Trachea on entering into thorax, it divides into two primary bronchi.
Each primary bronchi on entering into the lung, is divided into
secondary bronchi which is further divided into teritiary bronchi.
Teritiary bronchi divides into many branches called bronchioles. They
are in the order of primary bronchioles, secondary, teritiary, terminal
and respiratory bronchioles.
THE FUNCTION OF THE BRONCHIOLES is to deliver air to a
diffuse network of around 300 million alveoli in the lungs.5As you
inhale, oxygenated air is pulled into the bronchioles. Carbon dioxide
collected by the alveoli is then expelled from the lungs as you exhale.

DIAPHRAGM
The diaphragm, the chief muscle of respiration, is a thin, but strong,
domeshaped muscular membrane. It separates the abdominal and
thoracic cavities. The diaphragm is attached to the inferior margin of
the rib cage and to the bodies of the lumbar vertebrae behind. As a
muscular membrane, it domes upward into the thoracic cavity. Upon
contraction, the fibers of the diaphragm shorten and pull downward.
This downward motion produces a piston-like pressure on the
contents of the abdominopelvic cavity.
DIAPHRAGM FUNCTION
The diaphragm is a thin skeletal muscle that sits at the base of the
chest and separates the abdomen from the chest. It contracts and
flattens when you inhale. This creates a vacuum effect that pulls air
into the lungs.

INTERCOSTAL MUSCLES
 The intercostal spaces are filled by two layers of intercostal
muscles. The intercostal muscles extend from the vertebrae
behind to the sternum in front. A strengthening "plywood effect"
is created by the arrangement of the two layers at a right angle to
each other. These muscles help maintain the "solid-wall" condition
of the thorax. For this reason, a pressure gradient can be
maintained between the inside and outside of the thorax.
 The intercostal muscles play a part in the mechanics of breathing.
Quiet breathing takes place due to the alternate contraction and
relaxation of the diaphragm and the internal intercostal muscles.
As an individual breathes in, the diaphragm contracts and, at the
same time, the external intercostal muscles contract causing the
ribs to be pulled upward and the sternum to be pushed forward.
This increases the anterior-posterior diameter of the thoracic
cavity. (The volume of the chest cavity increases.) When the
individual breathes out, the external intercostal muscles relax, the
ribs move downward, and, as the diaphragm relaxes, the thoracic
cage moves upward. These movements decrease the vertical and
anterior-posterior diameters of the thoracic cavity. The thoracic
cavity (smaller in volume) returns to its resting size.

PLEURA
Surrounding each lung individually is a serous cavity called the
pleural cavity (figure 1-9). The minute quantity of serous fluid in the
cavity serves as a lubricant. This serves to minimize friction for the
expansion and contraction of the lungs during breathing.
 Each lung is covered with a serous membrane called the visceral
pleura. The outer wall of the pleural cavity is lined with another
serous membrane known as the parietal pleura. Areas of the
parietal pleura are variously named according to their location.
The mediastinal pleura form the lateral wall of the mediastinum.
The diaphragmatic pleura cover the superior surface of the
diaphragm. The costal pleura line the inner surface of the rib
cage. The cupolar pleura form a dome-like extension into the root
of the neck. It contains the apex of the lung.
 When each lung is in its smaller volume, its corresponding
diaphragmatic pleura lies close to the lower costal pleura. The slit-
like cavity between them is called the costophrenic sinus. Fluids of
each pleural cavity tend to collect in this sinus since it is the
lowest area for each. When the diaphragm contracts and flattens
out, each costophrenic sinus opens up, and the inferior portion of
the expanding lung occupies this space

FUNCTION OF PLEURA
The pleural cavity, with its associated pleurae, aids optimal
functioning of the lungs during breathing. The pleural cavity also
contains pleural fluid, which acts as a lubricant and allows the pleurae
to slide effortlessly against each other during respiratory movements.

PHYSIOLOGY OF RESPIRATION
Breathing involves taking air into the lungs and sending it out of the
lungs. Thoracic cavity is bound dorsally vertebral column ventrally
sternum, posteriorly dome shaped diaphragm and laterally ribs.
Breathing is brought about by diaphragm and intercostals muscles. It
involves two steps, inspiration and expiration.
INSPIRATION
Taking air into lungs. It is brought about by the contraction of the
muscles of diaphragm and external intercostals muscles. By the
contraction of muscles diaphragm, dome shaped diaphragm becomes
flattened, so, volume increases anteroposteriorly. By the contraction
of external intercostal muscles, rib cage moves forward and
downward so volume of thoracic cavity increases dorsoventrally.
Finally, by the contraction of these muscles volume increases and
then 75% of air enters into the lungs.
EXPIRATION
It is by the relaxation of muscles of diaphragm and external
intercostal muscles. By the relaxation of muscles of diaphragm it
becomes dome shaped, so, volume of thoracic cavity decreases. By
the relaxation of external intercostal muscles, rib cage move to its
original position, so, volume of thoracic cavity decreases and air will
be expelled out.

EXCHANGE OF GASES

1. Pulmonary gas exchange also called external respiration (P-partial
pressure) Due to difference in PO2 and PCO2 in lungs and
pulmonary capillaries. There is an exchange of O2 from lungs to
pulmonary capillaries and diffusion of CO2 in opposite direction.
2. 2. Systemic gas exchange Exchange of O2 from systemic
capillaries (oxygenated blood) into tissues and diffusion of CO2 in
the opposite direction.
MECHANISM
Respiratory muscles (diaphragm and intercostals muscles)
contract and relax by receiving nerve impulse from respiratory
centre. Respiratory centre is located in medullaoblongata and
pons veroli. Respiratory centre includes Inspiratory centre and
Expiratory centre.
 Inspiratory centre sends impulses to diaphragm and external
intercostal areas then contract. As a result volume of thoracic
cavity increases and then inspiration occurs.
 Whenever these impulses cease relaxation of diaphragm and
external intercostal muscles result in expiration

RESPIRATORY VOLUME PARAMETERS
The parameters of respiration are measurements that indicate the
state of respiratory function, including lung volumes and capacities,
airway resistance, lung compliance and elasticity, and intrathoracic
pressure. Only a portion of air entering the respiratory system
actually reaches the alveoli. The volume of air that is not available for
gas exchange with the blood resides in the conducting spaces. This is
known as dead air and fills dead space, consisting of 150ml . The
instrument used to measure respiration rate is called spirometer or
respirometer.
Tidal volumes
Volume of air inhaled or exhaled during breathing. Normally 500 ml
is tidal volume only 350 ml enter into respiratory zone and remaining
150 ml does not reach respiration zone
Inspiratory Reserved
Volumes (3100 ml - males / 1900 ml - females) Amount of air
inhaled after forceful inspiration.
Expiratory Reserve Volume
(1200 ml in males / 700 ml – in females) Amount of air that can be
exhaled after forceful expiration.
Residual Volume
Volume of air that remains in the lungs after forceful expiration.

VITAL CAPACITY
Vital capacity is the sum of the tidal volume, the inspiratory reserve
volume, and the expiratory reserve volume.
Vital capacity = T.V + IRV + ERV
Males = 500 ml + 3100 ml + 1200 ml = 4800 ml
Females = 500 ml + 1900 ml + 700 ml =3100 ml
Inspiratory capacity(IC) Amount of air that can be breathed by
forced inspiration.
IC = Tidal volume + Inspiratory reserve volume.
Total lung capacity It is the sum of vital capacity and residual
volume. It is 6 litres in males and 4.2 litres in females.

DISEASE OF RESPIRATORY SYSTEM
(1) Lung cancer:- People inhale many irritating substances as a
part of ordinary breathing. Inhaled smoke and almost all pollutants
have an irritating effect on the bronchial tubes and lungs. These
pollutants act as stresses or irritating stimuli. A common lung cancer,
bronchogenic carcinoma, starts in the walls of the bronchi and is
caused by stress and irritation.
(2) Nasal polyps:- These polyps, protruding growths of mucous
membrane hanging down from the posterior wall of the nasal
septum, are bluish-white tumors. As they become larger, they may
fill the nasopharynx making breathing through the nose difficult. A
doctor can remove these polyps easily.
(3) Bronchial asthma:- Usually, bronchial asthma is caused by an
allergy to edible or air-borne substances--for example, wheat or dust.
Muscles in the walls of the small bronchi and bronchioles go into
spasms caused by the allergy. Also, the smaller bronchi and
bronchioles may be clogged with excessive amounts of mucous
making breathing difficult.

(4) Bronchitis. Bronchitis is inflammation of the bronchi. The most
important cause of chronic bronchitis is cigarette smoking. (Chronic
bronchitis is bronchitis that lasts for at least three months of the year
for two successive years.)
(5) Emphysema. In this disease, the alveolar walls lose their
elasticity and remain filled with air during expiration. The word
"emphysema" means "blown up" or "full of air." A person with
emphysema must actively work to exhale. Also, as a result of
damage to the alveolar-capillary membrane, the respiration rate
slows down. Removing the irritating stimuli-- air pollution,
occupational exposure to dust, cigarette smoking--can slow down the
progressive deterioration
(6) Pneumonia. Pneumonia is an acute infection or inflammation of
the alveoli. The amount of air space in the lungs is reduced because
the alveolar sacs fill up with fluid and dead white cells. A bacteria
called pneumococcus bacterium is the most common cause of this
disease, but other bacteria or a fungus may also cause pneumonia.
Several viruses may cause viral pneumonia.

(7) Tuberculosis. Tuberculosis is caused by a bacteria--
Mycobacterium tuberculosis--which destroys parts of the lung tissue.
Tuberculosis bacteria are spread by inhaling, can live through some
disinfectants, but are killed by sunlight. This disease is sometimes
associated with crowded, poorly lit housing. A person with
tuberculosis must have rest, sunlight, and good diet.
(8) Coryza (common cold) and Influenza (flu). Common colds
are caused by viruses and typical symptoms include sneezing,
excessive nasal secretion, and congestion. (A fever is not usually one
of the symptoms.) A virus also causes influenza (flu) with
accompanying symptoms of chills, fever (usually higher than 101ºF),
headache, and muscular aches. As the fever subsides, cold-like
symptoms appear.

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