Class notes
Respiratory System
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Notes on the lungs, gas exchange and the anatomy and physiology of the lungs, capillaries.
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The Respiratory System• Respiratory system anatomy
o Nose
§ Divided into internal and external portions
• External - bone and hyaline cartilage covered with
muscle and skin, lined by a mucous membrane
• Internal - interior structures of external nose have 3
functions
o Warming, moistening and filtering incoming air
o Detecting olfactory stimuli
o Modifying speech vibration as they pass
through the large, hollow resonating chambers
• On the under surface of the external nose are two
openings – the nostrils or also called, the external
nares
• The Internal noses emerge with the external nose
and communicates with the pharynx through 2
openings called the internal nares or conchae. The
nasal conchae subdivide into each side of the nasal
cavity into a series of groovelike passageways the
superior, middle and inferior meatuses
• Ducts from the paranasal sinuses (frontal,
sphenoidal, maxillary and ethmoidal sinuses and the
nasolacrimal ducts also pen into the internal
nose) The lateral walls are formed by the ethmoid,
maxilla, lacrimal, palatine and inferior nasal conchae
bones, the ethmoid also forms the roof, the floor of the
internal nose is formed mostly by the palatine bones
and palatine processes of the maxilla which together
constitute the hard palate
• The space inside the internal nose is called the
nasal cavity divided into the right and left divided by a
vertical partition called the nasal septum. The anterior
portion is called the vestibule
• When air first comes into the nose It enters the
nostrils, it passes first through the vestibule which is
lined by skin containing coarse hairs that filter out
large dust particles. Mucus membranes lines the
cavity where the olfactory receptors lie in the
membrane lining the superior nasal conchae and the
adjacent septum, this region is the olfactory
epithelium
, §
o Pharynx (throat)
§ Muscular funnel shaped tube about 13cm long leading from
the oral and nasal cavities to the oesophagus and larynx
§ Function - permits the passage of swallowed solids and liquids
into the oesophagus (or gullet) and conducts air to and from the
trachea during respiration
§ Pharynx - thick fibres of muscle and connective tissue attach
the pharynx to the base of the skull and surrounding structures
§ Both circular and longitudinal muscles occur in the walls of the
pharynx; the circular muscles form constrictions that help push
food to the oesophagus and prevent air from being swallowed,
while the longitudinal fibres lift the walls of the pharynx during
swallowing.
§ Main divisions of the pharynx
• Nasopharynx - top part, made of respiratory epithelium
(protective mucus membrane) connects to nasal cavities,
lets air pass through (adenoid and part of your tonsils)
• Oropharynx - middle, connects to the mouth, allows air,
food and fluid to pass through, contains part of the tonsils
(rest are in the tongue)
• Laryngopharynx - bottom part, near the larynx,
regulates the passage of air to the lungs and food and fluid
to the oesophagus
o Larynx (voice box)
, § Hollow structure formed of 3 large sections of unpaired
cartilage - the thyroid, cricoid and epiglottis cartilage as well as 6
smaller cartilages
§ Function - essential for breathing vocalising and ensuring food
does not get stuck in the trachea and cause choking
§ Sit anterior to the oesophagus at the level of the 3rd - 6th
cervical vertebrae (in its normal position)
§ Here, the vocal folds are located
§ Sig. medical conditions i.e. bacterial infection (laryngitis),
laryngeal cancer, vocal fold paralysis (VFP) - all seriously
compromise function
§ Larynx visibly moves up and down when people swallow
§ Thyroid cartilage
• Susceptible to bacterial infection
• Largest, composed of front and side portions
• Right and left halves (laminae) fuse in the midline to
create a projection forward - the laryngeal prominence
(adam’s apple)
• Function - supports and protects the vocal cord, helps
create the sound of a person’s voice
• Hyaline cartilage ring fully encircles the trachea and
composes the inferior-most boundary of the laryngeal
skeleton
• Function - maintain airway patency, provides an
attachment point for the key muscles, ligaments and
cartilage involved with phonation
• Responsible for creating the sound of a person’s voice
o Patency = condition of being open and
unobstructed
o Laryngeal skeleton - 9 cartilages: thyroid,
cricoid, epiglottis, arytenoid, corniculate and
cuneiform cartilages
o Cricoid cartilage - clinically, the cricoid cartilage
is important anatomical landmark for procedures
like cricothyroidotomy (used to establish a viable
airway in an emergency setting)
§ Epiglottis cartilage
• A flap of cartilage located in the pharynx posterior to
the tongue and anterior to the larynx
• Function - usually upright at rest
o Allows air to pass into the larynx and lungs
o When a person swallows, the epiglottis folds
backwards to cover the entrance of the larynx so
food and liquid do not enter the trachea and lungs
o Trachea
§ Delivers air from the upper respiratory tract to the bronchi.
Warms and moisturises the air and catches debri/microbes before
they enter the lungs
§ Tubular passageway, lower part of the respiratory tract
§ About 12cm long, 2.5cm in diameter
§ Connected to the larynx via a ring of cricoid cartilage and
surrounded by 16-22 U or C shaped rings of cartilage
§ Trachealls muscle lines the posterior wall, allowing for
flexibility
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