The respiratory system is a biological system consisting of the organs and tissues responsible for gas exchange in animals and plants. In humans, the main components of the respiratory system are the nose, pharynx, larynx, trachea, bronchi, and lungs, which work together to inhale oxygen and exhale carbon dioxide. The respiratory system helps to supply oxygen to the body's cells and remove waste products, allowing to produce energy and the maintenance of life.
The
respiratory system comprises of the following parts:
·
Nose:
filters, warms, and moistens inhaled air
·
Pharynx:
common passage for air and food
·
Larynx:
houses the vocal cords, prevents food from entering the trachea
·
Trachea:
conducts air to the lungs
·
Bronchi:
two branches of the trachea that enter the lungs
·
Bronchioles:
smaller air passages within the lungs
·
Alveoli:
tiny air sacs where gas exchange occurs between air and blood.
·
Diaphragm:
muscle that helps regulate breathing by changing the size of the thoracic
cavity.
The physiological functions of the respiratory system can be described as follows:
·
Inhalation:
The diaphragm contracts and the ribcage expand, increasing the volume of the
chest cavity. This creates a pressure difference that draws air into the lungs.
·
Gas exchange:
Oxygen from inhaled air diffuses into the blood vessels surrounding the
alveoli, while carbon dioxide from the blood diffuses into the alveoli to be
exhaled.
·
Exhalation:
The diaphragm relaxes, and the ribcage decreases in size, reducing the volume
of the chest cavity. This creates a pressure difference that pushes air out of
the lungs.
·
Regulation of breathing:
The respiratory system is regulated by a complex network of nerves and hormones
that respond to changes in oxygen and carbon dioxide levels in the blood, as
well as changes in physical activity and emotional state.
· Defence mechanisms:
The respiratory system also has several defence mechanisms to protect against
foreign particles and microorganisms, including mucus production, cilia
movement, and coughing.
The
details about parts of respiratory system are as follows: -
1. Nose
The nose plays a vital role in the
respiratory system by filtering, warming, and moisturizing inhaled air. When
air enters the nose, it first passes through the nostrils, which are lined with
tiny hairs and mucus-secreting glands that help to filter out dust and other
particles. The air then enters the nasal cavities, where it is warmed and
humidified by the blood vessels in the nasal tissues. the nose can be allocated
into numerous parts:
Nostrils:
the external openings of the nose.
Septum:
a thin wall of cartilage and bone that divides the nose into two halves.
Nasal cavity:
the air-filled space inside the nose.
Olfactory mucosa:
the lining in the upper part of the nasal cavity responsible for the sense of
smell.
Conchae:
scroll-like bones that help to increase the surface area of the nasal cavity,
improving the filtration of inhaled air.
Nasal hairs:
fine hairs in the nostrils that trap dust and other particles from inhaled air.
Paranasal sinuses:
air-filled spaces in the bones surrounding the nasal cavity that help to reduce
the weight of the skull and improve resonance of the voice.
The nose also plays a role in the sense of
smell, which is important for detecting potential dangers and triggering
memories and emotions.
2. Pharynx
The pharynx, also known as the throat, is
a muscular tube-like structure that serves as a common passage for both air and
food. It is located in the neck, behind the nasal cavities and mouth, and
extends from the base of the skull to the level of the 6th cervical
vertebra.
The pharynx is divided into three regions:
the nasopharynx, the oropharynx, and the laryngopharynx.
Nasopharynx:
The uppermost part of the pharynx, located behind the nose. It communicates
with the nasal cavities and contains the openings of the Eustachian tubes,
which equalize pressure in the middle ear.
Oropharynx:
The middle part of the pharynx, located behind the mouth. It is continuous with
the oral cavity and contains the palatine tonsils.
Laryngopharynx:
The lower part of the pharynx, located below the oropharynx and above the
larynx. It is continuous with the esophagus and functions as a passage for both
air and food.
The pharynx also plays a role in the
production of speech by serving as a resonating chamber for the vocal cords
located in the larynx. The pharynx is also involved in swallowing, which is the
process of moving food from the mouth to the stomach through the esophagus.
3. Larynx
The larynx, also known as the voice box,
is a structure located in the upper part of the trachea. It is composed of
several cartilages, muscles, and mucous membranes, and it serves as a critical
component of the respiratory and digestive systems.
The main cartilages of the larynx include
the thyroid cartilage, the cricoid cartilage, and the arytenoid cartilages. The
thyroid cartilage, which forms the front part of the larynx, is commonly known
as the "Adam's apple." The cricoid cartilage forms the lower part of
the larynx, and the arytenoid cartilages are small triangular structures that
help to move the vocal cords.
The vocal cords, or vocal folds, are two
folds of mucous membrane located within the larynx. They are responsible for
producing sound during speech and singing by vibrating as air passes over them.
The larynx also contains several muscles
that control the position of the vocal cords and help to regulate breathing.
The most important of these muscles is the cricothyroid muscle, which is responsible
for changing the tension of the vocal cords and controlling the pitch of
speech.
The larynx is an important structure that
helps to prevent food and other foreign objects from entering the trachea and
lungs. Additionally, it plays a critical role in producing speech and allowing
humans to communicate with one another.
4. Trachea
The trachea, also known as the windpipe,
is a tubular structure that extends from the larynx to the bronchi in the
lungs. It is approximately 10-12 cm long and 2.5 cm in diameter in adults.
The trachea is composed of several layers
of tissue, including smooth muscle, connective tissue, and a mucous membrane
that lines the interior of the tube. The smooth muscle in the walls of the
trachea helps to regulate the diameter of the airway and control air flow.
The trachea is supported by a series of
C-shaped cartilages that give it a semi-rigid structure and prevent it from
collapsing. These cartilages are connected by smooth muscle and fibrous tissue
and are arranged in a series of rings that encircle the trachea.
The trachea is lined with mucous membranes
that produce a thin layer of mucus, which helps to trap inhaled dust, bacteria,
and other foreign particles. The cilia, tiny hair-like structures on the
surface of the tracheal epithelium, move in coordinated, rhythmic motions to
help move mucus and trapped particles upward, towards the mouth and out of the
respiratory system.
The trachea is also responsible for
conducting air to the lungs. As air is breathed in through the nose or mouth,
it passes through the larynx and into the trachea. From there, the air is
carried to the bronchi, which branch into smaller airways called bronchioles
and eventually reach the alveoli, where gas exchange between air and blood
occurs.
5. Bronchi
The bronchi are two main branches of the
trachea that enter the lungs and subdivide into smaller and smaller airways,
eventually forming the bronchioles, which lead to the alveoli. The bronchi are
lined with mucous membranes and are supported by rings of cartilage, similar to
the trachea. Like the trachea, the bronchi are composed of smooth muscle and
cartilage, which help to keep the airways open and prevent them from
collapsing. The bronchial walls are also lined with mucous membranes, which
produce mucus that traps inhaled particles and foreign substances.
The bronchi are also responsible for
regulating airflow into the lungs. During inhalation, the bronchial smooth
muscle relaxes, allowing for the airways to widen and air to flow in more
easily. During exhalation, the smooth muscle contracts, narrowing the airways
and slowing the flow of air out of the lungs.
The bronchi play an important role in gas
exchange, delivering oxygen-rich air to the alveoli and carrying carbon
dioxide, a waste product, out of the lungs. The bronchial smooth muscle and
cilia also help to protect the lungs from inhaled irritants and pathogens, such
as dust, pollen, and bacteria.
6. Bronchioles
Bronchioles are the small airways that
branch off from the bronchi in the lungs. They are lined with smooth muscle and
do not contain cartilage, which allows for greater flexibility and the ability
to constrict and dilate in response to changes in airway resistance.
The bronchioles are responsible for
regulating airflow and directing air to different areas of the lungs. They are
divided into terminal bronchioles, which are the smallest airways that lack
alveoli, and respiratory bronchioles, which contain alveoli and are involved in
gas exchange.
The smooth muscle in the bronchioles can
contract and relax, which affects the resistance to airflow in the lungs. This
process is regulated by the autonomic nervous system, which can cause
bronchoconstriction, or narrowing of the airways, in response to irritants or
allergens. Bronchodilation, or widening of the airways, can also occur in
response to medications or other stimuli.
7. Alveoli
The alveoli are the small, thin-walled
sacs in the lungs where gas exchange occurs between the air and the blood. The
alveoli are surrounded by tiny blood vessels called capillaries, which allow
for the exchange of oxygen and carbon dioxide between the air and the blood.
The walls of the alveoli are very thin,
which allows for the efficient exchange of gases. The alveoli are also
surrounded by a network of elastic fibres that help to maintain the shape and
structure of the air sacs.
During inhalation, oxygen-rich air enters
the alveoli and diffuses across the alveolar wall into the capillaries, where
it binds to haemoglobin and is transported to the rest of the body. At the same
time, carbon dioxide from the blood diffuses across the capillary wall and into
the alveoli, where it is exhaled during exhalation.
The alveoli are also lined with a layer of
fluid that helps to keep the air sacs moist and prevents them from collapsing
during exhalation. This fluid is produced by cells in the alveolar wall and is
regulated by a variety of factors, including hormones, nervous signals, and
mechanical stress.
In addition to their role in gas exchange,
the alveoli are also important for immune function. They contain a variety of
immune cells, including macrophages, which help to protect the lungs from
infections and other foreign substances.
8. Diaphragm
The diaphragm is a dome-shaped, sheet-like
muscle located at the base of the thoracic cavity that separates the chest from
the abdominal cavity. It plays a crucial role in respiration by contracting and
relaxing to change the volume and pressure within the chest cavity.
During inhalation, the diaphragm contracts
and moves downward, which increases the volume of the chest cavity and creates
negative pressure within the lungs. This negative pressure causes air to flow
into the lungs, filling the alveoli with oxygen-rich air. During exhalation,
the diaphragm relaxes and moves upward, decreasing the volume of the chest
cavity and creating positive pressure that forces air out of the lungs.
The diaphragm is innervated by the phrenic
nerve, which originates in the spinal cord and runs through the neck to reach
the muscle. It is controlled by the respiratory centre in the brainstem, which
coordinates the rhythmic contraction and relaxation of the diaphragm and other
respiratory muscles.
In addition to its role in respiration,
the diaphragm also plays a role in other bodily functions, including coughing,
sneezing, and vomiting. It also helps to support the abdominal organs and
maintain intra-abdominal pressure. Dysfunction of the diaphragm can lead to a
variety of respiratory and gastrointestinal problems, including shortness of
breath, acid reflux, and abdominal pain.
