RESPIRATORY SYSTEM
It consists of the following parts:
A- Nose:
It is formed of external nose and nasal cavity.
External nose: Pyramidal in shape having a root and free apex, formed of
upper bony part and lower cartilaginous part.
Nasal cavity:
There are two nasal cavities separated by a nasal septum. Each cavity opens
on the face through the anterior nasal opening and opens posteriorly in the
nasopharynx through the posterior nasal opening.
Each nasal cavity is partially divided by three curved bony projections from the
lateral wall called nasal conchae into a localized spaces called nasal meatuses.
Functions of the nose:
1- Smell.
2- Filtration and warming of the inspired air.
3- Nasal conchae increase the surface area of the nasal cavity which magnifies
the turbulence of air and thus improves olfaction.
Paranasal sinuses: They are air-filled spaces in the skull bones surrounding
the nose (pneumatic bones) and open in the nasal meatuses.
Functions:
1- Decrease the weight of the skull.
2- Increase the resonance of voice.
3- They act as air cushions for the brain, eye and pituitary gland.
Paranasal sinuses are:
1- Frontal sinus present in the frontal bone.
2- Maxillary sinus: The largest air sinus present in the maxilla.
3- Sphenoidal sinus: It occupies the body of the sphenoid bone below pituitary
gland.
4- Ethmoidal sinuses: 3 groups of sinuses (anterior middle-posterior) present
in the ethmoid bone in the medial wall of the orbit.
B- Pharynx. (See digestive system)
C- Larynx:
It is a tube consisting of 9 cartilages (3 single and 3 paired) connected together by
membranes and ligaments and moved by special muscles.
The large and single cartilages of the larynx are: thyroid, cricoid and epiglottis.
It extends from the root of the tongue till the beginning of trachea at the level of C6
vertebra. It contains the vocal cords which are responsible for production of voice.
Function:
1. Passage of air to trachea and lungs.
2. Production of voice by vocal cords.
3. Reflex expulsion of foreign bodies.
D- Trachea:
10 cm patent tube, transmits the air from the larynx to the lungs. It consists of 16-20
C-shaped cartilages.
It lies in the midline, its upper 1/2 in the neck while its lower 1/2 in thorax.
It ends in thorax behind the sternal angle (lower border of T4 vertebra) by dividing into
two bronchi.
E- Lungs:
Each lung is nearly half cone shaped structure having an apex above and base below
and 2 surfaces (lateral convex and medial concave containing the hilum through which
the structures enter and leave the lung). It is covered by the pleura which is a closed sac
formed of 2 layers: visceral and parietal with pleural cavity in-between.
A- Right lung B- Left lung
1. Short and wide
2. weight: 625 g
3. Formed of three lobes (upper, middle
and lower)
4. Has two fissures (oblique-horizontal)
5. Has 10 segments
6. Has no cardiac notch
1. Long and narrow
2. weight: 565 g
3. Formed of two lobes (upper and
lower)
4. Has one fissure (oblique)
5. Has 8-segments
6. Has cardiac notch