UPPER RESPIRATORY TRACT - ENGLISH
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UPPER RESPIRATORY TRACT-
• RESPIRATORY
SYSTEM-The respiratory system includes the organs which provides the route by
which the oxygen present in the atmospheric air enters the body, and it
provides the route of excretion for carbon dioxide. The parts of
respiratory system are divided into two
groups-
• Upper
Respiratory Tract.
• Lower
Respiratory Tract.
UPPER RESPIRATORY TRACT- Upper Respiratory Tract is
divided into-
• Nose
• Pharynx
and
• Larynx
NOSE- Nose is the
anterior part of nasal cavity which is made up of
nasal bones, cartilage, skin and
mucus membrane. It is the main route of air entry, and consists of a large
irregular nasal cavity which is divided into two equal passages by a septum.
• The
roof of nasal cavity is formed by the
ethmoid bone and the sphenoid bone, frontal bone and nasal bones. The
floor is formed by the roof of the mouth and consists of the hard
palate the soft palate . The medial wall is formed by the
septum. The lateral walls are formed by the maxilla, the ethmoid bone
and the inferior conchae. The nose is lined with very vascular ciliated
columnar epithelium which contains mucus-secreting goblet cells
FUNCTIONS OF NOSE-
• The
function of the nose includes-
• Warming
of air- This is due to the immense vascularity of the mucosa.
• Filtering
and cleaning-Hairs at the anterior nares trap larger particles. Smaller
particles such as dust and bacteria settle and adhere to the mucus.
• Humidification-As air travels over the
moist mucosa, it becomes saturated with water vapour. The sense of smell
• Olfaction-
The nose is the organ of the sense of smell which is completed with the
help of olfactory nerve.
PHARYNX-
• The
pharynx is a tube 12 to 14 cm long that extends from the base of the skull to
the level of the 6th cervical vertebra. It has three parts-
• Naso-pharynx- The nasal part of the
pharynx lies behind the nose above the level of the soft palate. On its lateral
walls are the two openings of the auditory tubes one leading to each middle ear. On the
posterior wall are the pharyngeal tonsils (adenoids), consisting of
lymphoid tissue. They are most prominent in children up to approximately 7
years of age. Thereafter they gradually atrophy.
• Oro-pharynx- The oral part of the
pharynx lies behind the mouth, extending from below the level of the soft
palate to the level of the upper part of the body of the 3rd cervical vertebra.
During swallowing, the nasal and oral parts are separated by the soft palate
and the uvula.
• Laryngopharynx- The laryngeal part of
the pharynx extends from the oropharynx above and continues as the oesophagus
below . from the level of the 3rd to the 6th cervical vertebrae. The wall of
pharynx is made up of muscles, submucosa and mucosa. The mucosa varies slightly
in the different regions. In the nasopharynx it is continuous with the lining
of the nose and consists of ciliated columnar epithelium; in the oropharynx and
laryngopharynx it is formed by tougher stratified squamous epithelium, which is
continuous with the lining of the mouth and oesophagus.
FUNCTIONS OF PHARYNX-
• Passageway
for air and food- The pharynx is involved in both the respiratory and the
digestive systems: air passes through the nasal and oral sections, and food
through the oral and laryngeal sections.
• Warming
and humidifying- By the same methods as in the nose, the air is further
warmed and moistened as it passes through the pharynx.
• Taste-
There are olfactory nerve endings of the sense of taste in the epithelium
of the oral and pharyngeal parts.
• Hearing-
The auditory tube, extending from the nasopharynx to each middle ear,
allows air to enter the middle ear. Satisfactory hearing depends on the
presence of air at atmospheric pressure on each side of the tympanic
membrane
• Protection-
The lymphatic tissue of the pharyngeal and laryngeal tonsils produces
antibodies in response to antigens,
• Speech-
The pharynx functions in speech; by acting as a resonating chamber for
sound ascending from the larynx,
LARYNX-The larynx or ‘voice box’ lies between
laryngopharynx and the trachea. Until puberty there is little difference in the
size of the larynx between both the sexes. Thereafter, it grows larger in the
male, and becomes the prominence of the ‘Adam’s apple’ and the generally
produce deeper voice.
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 cricoid cartilage
·
2 arytenoid cartilage
·
1 epiglottis
·
THYROID CARTILAGE- This is the most prominent of
the laryngeal cartilages. It is made of hyaline cartilage, it lies to the front
of the neck. Its anterior wall projects into the soft tissues of the front of
the throat, forming the laryngeal prominence or Adam’s apple, which is
easily felt and often visible in adult males. The anterior wall is partially
divided by the thyroid notch. The cartilage is incomplete posteriorly,
and is bound with ligaments to the hyoid bone above and the cricoid cartilage
below.
·
CRICOID CARTILAGE- This lies below the thyroid
cartilage and is also composed of hyaline cartilage. It is shaped like a signet
ring, completely encircling the larynx with the narrow part anteriorly and the
broad part posteriorly. It is lined with
ciliated columnar epithelium and there are muscles and ligaments attached to
its outer surface
• ARYTENOID
CARTILAGE- These are two roughly pyramid-shaped hyaline cartilages situated on
top of the broad part of the cricoid cartilage forming part of the posterior
wall of the larynx They give attachment
to the vocal cords and to muscles and are lined with ciliated columnar
epithelium
EPIGLOTTIS -
·
This is a leaf-shaped fibro-elastic cartilage
attached on a flexible stalk of cartilage to the inner surface of the anterior
wall of the thyroid cartilage immediately below the thyroid notch . It rises
obliquely upwards behind the tongue and the body of the hyoid bone. It is
covered with stratified squamous epithelium.
INTERIORS OF
LARYNX -
The vocal cords are two
pale folds of mucous membrane with cord-like free edges, which extend from the
inner wall of the thyroid prominence anteriorly to the arytenoid cartilages
posteriorly . When the muscles controlling the vocal cords are relaxed, the
vocal cords open and the passageway for air coming up through the larynx is
clear; the vocal cords are said to be abducted (open). The pitch of the
sound produced by vibrating the vocal cords in this position is low.
• When
the muscles controlling the vocal cords contract, the vocal cords are stretched
out tightly across the larynx and are
said to be adducted (closed). When the vocal cords are stretched to this
extent, and are vibrated by air passing through from the lungs, the sound
produced is high pitched. The pitch of the voice is therefore determined by the
tension applied to the vocal cords by the appropriate sets of muscles. When not
in use, the vocal cords are adducted. The space between the vocal cords is
called the glottis.
FUNCTIONS OF
LARYNX -
• Production
of sound- Sound is produced by vibration
of vocal cords. Pitch of the voice depends upon the length and tightness
of the cords. Volume of the voice depends upon the force with which
the cords vibrate which depend upon force of expired air .
• Speech-This
is produced when the sounds produced by the vocal cords are manipulated by the
tongue, cheeks and lips.
• Protection
of the lower respiratory tract-During swallowing the larynx moves upwards,
blocking the opening into it from the pharynx.
• Passageway
for air-The larynx links the pharynx above with the trachea below and provide clear
pathway for air to pass.
• Humidifying,
filtering and warming- These processes continue as inspired air travels
through the larynx because larynx is also
lined with mucus membrane.
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