AFGALALY محمد عبد الفتاح جلال
AFGALALY محمد عبد الفتاح جلال
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Nasal Cavity, Paranasal Sinuses, Maxillary Division of Trigeminal NerveCan't stress enough, ORIENT YOURSELF
Bones of the Nasal Cavity
Nasal Septum
Lateral Nasal WallORIENT YOURSELF!
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| The major sensory innervation to the nasal cavity is from branches of the maxillary division of the trigeminal (nasopalatine, infraorbital, greater palatine). Other sensory branches are from the ophthalmic division (anterior ethmoidal nerve). Any secretory glands of the nasal cavity are supplied by branches of the pterygopalatine ganglion. The olfactory epithelium in the roof of the nasal cavity is innervated by the olfactory nerve (I) and receives smell sensations. |
| The major arterial supply to the nasal cavity are from the ophthalmic and maxillary arteries by way of anterior and posterior ethmoidal branches and sphenopalatine branches respectively. |
Muscle |
Origin |
Insertion |
Action |
Nerve supply |
| tensor palati | scaphoid fossa of pterygoid fossa | aponeurosis of soft palate | elevates and tenses soft palate | V3 |
| levator palati | apex of petrous temporal bone and auditory tube | aponeurosis of soft palate | pulls soft palate up and back | X |
| palatopharyngeus | aponeurosis of soft palate | wall of pharynx | elevates pharynx | X |
| salpingopharyngeus | cartilage of auditory tube | wall of pharynx | elevates pharynx | X |
Bones
nasal
frontal
ethmoid
crista galli
perpendicular plate
superior concha
middle concha
sphenoid body
medial pterygoid plate
hamulus
inferior concha
maxilla
palatine processes
palatine bone
horizontal process
Air sinuses
frontal
sphenoid
ethmoid
maxillary
Muscles
tensor palati
levator palati
palatopharyngeus
salpingopharyngeus
Muscles
tensor palati
levator palati
palatopharyngeus |
Nerves
V2
greater palatine
lesser palatine
nasopalatine
infraorbital
posterior sup. alveolar
Muscles
tensor palati
levator palati
palatopharyngeus
Nerves
V2
greater palatine
lesser palatine
nasopalatine
infraorbital
posterior sup. alveolar
Nerves
V2
greater palatine
lesser palatine
nasopalatine
infraorbital
posterior sup. alveolar
Arteries
sphenopalatine
descending palatine
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 | lungs |
| heart |
The other structures are:
| aorta and its branches |
| superior and inferior vena cavae |
| trachea and primary bronchi |
| sympathetic trunks and their associations |
| azygos and hemiazygos venous systems |
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| True ribs have direct attachment between the vertebrae and
the sternum. Each rib attaches to the sternum by its own costal cartilage
False ribs attach to the sternum by way of costal cartilage above it.
Floating ribs do not have an anterior attachment at all
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Sternum
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A Typical Rib |
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| The first rib is atypical. It is found to be short, flat and more
sharply curved than any of the others. It has upper and lower surfaces,
with outer and inner borders, and on its head there is one articular
facet only.
The upper surface has two grooves for the subclavian artery and
subclavian vein, separated by the scalene tubercle for the attachment
of the scalene anterior muscle.
This rib has very little movement during respiration and serves as a
base attachment for the intercostal muscles and the ribs below. In
other words, during respiration, the muscles in the first
intercostal space contract, drawing up on the rib below, which in
turn allows its muscles to pull up on the rib below it and so forth,
until all ribs have moved through a small distance. The combined
movements increase the transverse and anteroposterior diameters of
the thoracic cavity.
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Characteristics of a typical thoracic vertebra include:
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| Transverse section through the thorax. |
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| When you examine the thorax in cross section, you will notice that it is kidney shaped in form. You can also appreciate the anterior, posterior and lateral boundaries. We will refer to this view of the thorax as we continue. | ||
The thoracic wall is supplied by three sources of blood supply:
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The thoracic wall is supplied by the intercostal nerves which are
the anterior primary rami of spinal nerves. A typical spinal nerve is
shown in the adjacent diagram.
Once you have the names down, you should try to understand what is going on in each of the branches.
Starting at the spinal cord, we can work our way out to the periphery
describing how a spinal nerve is formed and how it branches.
When the spinal cord is examined in cross section you can usually pick
out two colors on its surface: white and gray. This is called the
white matter and the gray matter of the spinal cord. The gray matter
forms a butterfly-like image with dorsal horns and ventral horns.
The white matter is made up mostly of nerve fibers running up and down
the spinal cord. The gray matter is made up mainly of cell bodies of
nerve cells, this giving a grayer appearance.
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| PA - posteroanterior |
| Lateral |
| In a PA view, the anterior chest is placed forward onto a film
holder. The x-ray machine then shoots x-rays through the body and
onto the film. In this way, the anterior thoracic structures
should have the best resolution. Most of you have had a general PA
radiograph taken. Remember that they always have you take in a
deep breath and hold it and also to place you hands on your hips
with your shoulders pressed against the film. What this does is to
pull the thorax as far forward as possible and the air in the
lungs will give a better contrast to muscular structures and
viscera because it will be black.
Identify the following structures:
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| The lateral view gives a different appearance to the shadow of
the heart and aorta.
Identify:
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These cross sections are arranged so that the right side of the body is on your left. This is how you will examine CAT scans and MRI's if you are heading for the clinical profession. This is difficult for many people but it is something you have to set your mind to at the very beginning of studying cross sections. It might help if you pretend that you are looking at a person, patient or a cadaver lying on a bed. You are standing at their feet and looking up towards their head. Now imagine a section taken from any part of the body, in this case the thorax, and keep in mind where that person's or cadaver's right and left arms are. With practice, it will become second nature to you. Knowing left from right is very important, particulary if you are going to be in a medical profession. I am sure you wouldn't want to cut off the wrong limb or remove the wrong kidney. It has happened, but fortunately rarely.
| Cross section through the thorax at vertebra T2
This section cuts through the superior mediastinum above the aortic
arch.
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| Cross section through the thorax at vertebra T3.
This section is also through the superior mediastinum but a little
lower than the one above. You are looking up and into the aortic
arch.
Although not labeled, you should be able to make out the openings
of the brachiocephalic, left common carotid and left subclavian
arteries.
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| Cross section through the thorax at vertebra T5.
This section cuts through the anterior, middle and posterior
mediastina.
You now see the ascending and descending aortae as well as the
pulmonary trunk.
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| Cross section through the thorax at vertebra T8.
This section cuts through the heart in such a way that all four
chambers of the heart are seen. You should also be able to
differentiate the anterior, middle and posterior parts of the
inferior mediastinum.
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| Cross section through the thorax at vertebra T9.
This section is taken just below the one above except that you are
now beginning to cut into the abdomen. On the right side, you can
see a piece of the liver which is just beneath the diaphragm. The
dome of the right diaphragm is usually higher because of the massive
liver below it.
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The pleural cavity is a closed space (like the inside of a balloon) within
which the lung has grown. As the lung grows into the space, it picks up a
layer of pleura (outside of balloon) and this is called the visceral pleura.
The remainder of the pleura is called the parietal pleura. Pleura is a
membrane that is single celled. Normally it produces a small amount of fluid
that fills the gap between the parietal and visceral layers of pleura.
The best way to see the various aspects of the pleura is to examine a cross
section of the thorax and a frontal (coronal) section.
This is a cross section through the thorax showing the various parts
of the parietal pleura. Notice that the visceral and parietal pleura are
continuous at the root of the lung.
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This is a frontal or (coronal) section through the thorax showing the
various parts of the parietal pleura. Notice again that the visceral and
parietal pleurae are continuous at the root of the lung.
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| The lungs fill the pleural cavities and are divided into lobes.
The left lung has 2 lobes and the right lung has 3 lobes. The bulk of
the lung surface is against the ribs and is called the costal surface.
Other surfaces include the diaphragmatic and mediastinal. Each lung
also has 3 borders: anterior, posterior and inferior. The lobes can be
seen in the two adjacent figures. The costal (lateral) surfaces of the
lungs are shown. In both lungs, the superior and inferior lobes are
separated by the oblique fissure. In the right lung, the superior lobe
is further divided into the superior and middle lobes, which are
separated by the horizontal fissure. The anterior border of the left lung is pushed out by the heart and this notch is called the cardiac notch. If you follow this notch inferiorly, you will find a small lingular lobe. |
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In cadaveric lung specimens, grooves are sometimes left on the
mediastinal aspect of the lungs and these are formed by structures
near the lung. On the mediastinal surface of the right lung, you
will find these structures:
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On the mediastinal surface of the left lung, you will find
these structures:
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| external layer -- external intercostal |
| internal layer -- internal intercostal |
| innermost layer -- transversus thoracic (anterior), innermost (lateral) and subcostal (posterior) |
The diaphragm is the most important muscle of the thoracic wall. During normal respiration, this muscle is the primary component.
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diaphragm as seen from below |
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| Subdivisions of thorax as seen on cross section
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| Subdivision of mediastinum as seen on cross section
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| Subdivision of mediastinum as seen on sagittal section
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| superior mediastinum (1)
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| inferior mediastinum (2)
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Clinical radiologists have described the subdivisions of
the mediastinum in the following way:
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Bones
Muscles
Arteries
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Lungs
Heart
Other Viscera
Miscellaneous
Radiographs
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| ribs | ||||||||
| clavicle | ||||||||
| scapula
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| greater tubercle |
| crest of greater tubercle |
| lesser tubercle |
| crest of lesser tubercle |
| intertubercular sulcus (groove) |
| pectoralis major |
| pectoralis minor |
| subclavius |
| serratus anterior |
| subscapularis |
| teres minor |
| teres major |
| latissimus dorsi |
| tendon of long head of biceps brachii |
Muscle Details |
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| Muscle | Origin | Insertion | Nerve supply | Action |
| pectoralis major | medial half of clavicle sternum costal cartilages aponeurosis of external oblique |
lateral lip of intertubercular sulcus | medial and lateral pectoral nerves |
flexes, adducts, and rotates arm medially |
| pectoralis minor | anterior surface of 2nd thru 5th ribs |
coracoid process of scapula |
protracts scapula pulls it forward onto the thorax elevates ribs when scapula is held steady |
medial pectoral nerve |
| subclavius | costal cartilage of first rib |
lower surface of clavicle | nerve to subsclavius | depresses lateral end of clavicle pulls clavicular head into sternoclavicular joint |
| serratus anterior | lateral surface of 1st to 8th or 9th ribs |
vertebral (medial) border of scapula |
long thoracic | protract scapula pulls it forward rotates scapula laterally |
| teres minor | axillary (lateral) border of scapula |
inferior aspect greater tubercle of humerus |
axillary | rotates arm laterally |
| teres major | posterior aspect inferior angle of scapula |
crest of lesser tubercle of humerus |
lower subscapular | adducts and rotates arm medially |
| latissimus dorsi | spinous processes lower 6 vertebra thoracolumbar fascia iliac crest |
floor of intertubercular fossa |
thoracodorsal | adducts, extends medially rotates humerus |
Axillary artery
In this lesson, we will first examine the pectoral region. This region is
of clinical importance in the female because of the mammary gland and its
implication in cancer.
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The muscles of the pectoral region are muscles that act on the upper limb.
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Bones of the Pectoral Region
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Muscles of the Pectoral Region
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The vessels and nerves of the pectoral region are branches of the subclavian and axillary arteries and the intercostal nerves.
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Respiration is the process of exchanging O2 with CO2. In order to get the oxygen into the lungs, all of the structures that you have just learned act together to increase the area of the thoracic cavity. The ribs and diaphragm move in such a way that three dimensions of the thoracic cavity are increased:
Lateral Dimension |
AnteroPosterior and SuperoInferior Dimensions  |
During inspiration, the lateral dimensions of the thoracic cavity are increased by the 7-10th ribs moving laterally (similar to bucket handles). The anteroposterior dimension is increased by the sternum being pushed forward by the true ribs (1-6). The superoinferior dimension is increased by the diaphragm contracting and becoming lower. During restful breathing, the diaphragm probably does most of the work, although small movement in all directions probably occur. During increased need for oxygen (exercise, pathology), the lateral and anterioposterior movements will be increased. When the thoracic muscles can no longer do the job, other muscles attaching to the thorax will be called into action (pectoralis major and minor, sternomastoid, etc.) During expiration, the intercostal muscles and the diaphragm relax and the elastic fibers of the lung and the costal cartilages recoil to their original state before inspiration. The automatic nature of the respiratory cycle is controlled in the respiratory centers of the brain stem.
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In Lesson 3, we discussed the subdivisions of the mediastinum as described by anatomists. As a summary, remember that the mediastinum is subdivided into superior and inferior parts. The inferior mediastinum is further subdivided into anterior, middle and posterior parts.
| As you work your way from anterior to posterior in the
posterior mediastinum, your first task will be to clean away the
posterior wall of the pericardial cavity. After the heart has been
removed, you will see the cut borders of the major vessels
entering and leaving the heart. The oblique pericardial sinus is
clearly seen within the four pulmonary veins and inferior vena
cava at this point.
The arrow at the top represents the division between the
superior mediastinum above and the inferior mediastinum below.
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| In Level 2, the pericardium has been removed and the esophagus
can seen along with its plexus derived from the left and right
vagus nerves as well as branches from the sympathetic chain.
As the esophagus passes through the diaphragm to enter the
abdomen, the left vagus emerges from the plexus as the anterior
vagal trunk and the right vagus becomes the posterior vagal
trunk.
You can also see that the trachea splits into the right and
left primary bronchi at the level of the junction between the
superior and inferior mediastinae.
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| Once the esophagus has been studied, the next level to check
out is the thoracic aorta. The thoracic aorta starts at the T4-T5
junction and extends the full length of the posterior mediastinum
passing through the aortic hiatus of the diaphragm into the
abdomen.
The thoracic aorta gives rise to the posterior intercostal
arteries which pass posterior and lateral to join the posterior
intercostal veins and intercostal nerves to form the
neurovascular bundle that travels along the inferior border of a
rib or the upper aspect of an intercostal space, however you
want to remember it. It also gives rise to bronchial branches
that enter the root of the lung to supply the bronchi and lung
tissue.
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| Behind and between the esophagus and thoracic aorta, you will
find the thoracic duct, a fragile lymphatic duct that begins in
the abdomen as the cisterna chyli.
At the T4-T5 level, it veers to the left and travels through the
superior mediastinum on its way into the neck, where it will
enter the venous system at the junction of the internal jugular
and left subclavian veins.
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| Alongside and behind the thoracic duct, you will find the
veins that drain the walls of the thorax, the azygos and
hemiazygos veins. Each of these veins begin in the abdomen as the
ascending lumbar veins. The ascending lumbar veins drain parts of
the posterior abdominal wall.
The azygous vein begins at the junction of the ascending lumbar
vein and the subcostal vein and passes deep to the right crus of
the diaphragm to enter the posterior mediastinum. It continues
upward along the right side of the bodies of the thoracic
vertebrae and to the right of the descending aorta receiving
posterior intercostal veins along the way. At about T8, it forms
an arch that passes over the root of the right lung and then
enters the posterior aspect of the superior vena cava. The arch
receives the left superior intercostal vein that drains the
upper 2 or 3 posterior intercostal spaces.
The hemiazygous veins are quite variable in their makeup but the
classic description is that the upper intercostal spaces are
drained by the superior hemiazygos vein and the lower the
inferior hemiazygos vein. These two veins may join as one
hemiazygos vein that passes behind the thoracic duct to empty
into the azygos vein. The two veins may just as frequently pass
into the azygos separately, forming two hemiazygos veins. Or,
there may be multiple veins crossing into the azygos vein,
whereby a true hemiazygos vein doesn't exist at all.
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| If you could reflect or remove the azygos system of veins, the next structures in the posterior mediastinum would be the splanchnic nerves, specifically the greater splanchnic nerves. These nerves are derived from the sympathetic chains, thoracic ganglion T5 to T10. There is also lesser splanchnic nerves that are derived from ganglion T10 and T11. Some people may even describe a least splanchnic that is derived from ganglion T12. Remember, according to anatomists, the sympathetic chain is not part of the posterior mediastinum. |
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| The most posterior item in the posterior mediastinum is the anterior longitudinal ligament which completely covers the anterior surfaces of the bodies of the vertebrae. This extends from the sacral part of the vertebral column all the up to the skull. |
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The image on the right is a colorized picture of an actual
dissection of the paravertebral region of the thorax. You should
be able to identify the following:
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| This would also be a good time to describe what is going on
in the sympathetic nervous system.
First, the sympathetic trunk and ganglion belong to the
autonomic nervous system. The internal structure of the
autonomic nervous system is made up of a series of two
neurons:
The path of the neurons are:
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Boundaries of the superior mediastinum (1)are:
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If it helps to remember what is in the superior mediastinum, you can visualize the contents in planes from anterior to posterior:
| glandular plane |
| venous plane |
| arterial-nervous plane |
| visceral plane |
| lymphatic plane |
| This image shows the structures of the superior mediastinum in tact. Then we will start from the anterior boundary and work our way through the superior mediastinum from anterior to posterior. |
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| With the thorax in tact, the first thing you see when you get ready to study the superior mediastinum is the manubrium of the sternum and the cartilage of the first rib. These structures make up the anterior boundary. |
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| The first plane is the glandular plane. The gland is what is left of the thymus. It consists of two lobes and is mainly fat in the adult with small islets of active thymic cells scattered throughout. |
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The second plane is the venous plane and consists of the:
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The third plane is the arterial-nervous plane and consists
of the:
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The fourth plane is the visceral
plane and includes the:
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| Trachea |
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| Esophagus |
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The fifth plane is the lymphatic plane and consists of the:
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| The larynx is a special part of the body that functions as an airway to the lungs as well as providing us with a way of communicating (vocalizing). These functions are all possible because of the skeletal components and the muscles that act on them. Before learning the details, memorize the various parts of the skeleton so that you can then visually place the muscles in the correct places and appreciate how they do their jobs. |
| The skeleton of the larynx is made up of the hyoid bone and several
cartilages.
The thyroid cartilage is made up of two laminae that fuse anteriorly
for form the laryngeal prominence (Adam's apple). The angle that they
make is usually more acute in males and therefore, is more prominent.
The inferior horns articulate with the sides of the cricoid cartilage and form the cricothyroid joint where the thyroid cartilage rocks back and forth at this point.
The cricoid cartilage is the only complete cartilage of the larynx.
Anteriorly is the cricoid arch. The arch expands as you trace it
posteriorly where it forms a square-shaped lamina.
The arytenoid cartilages sit on top of the cricoid lamina,
posteriorly and articulate there at the cricoarytenoid joints. The
arytenoid cartilages slide medially and laterally, anteriorly and
posteriorly and rotate at these joints. The cartilage is pyramidal
in shape with the base being triangular in shape with 3 processes.
The vocal process extends anteriorly, the muscular process lies
laterally and third process is not well defined. The vocal ligament
(cord) extends from the vocal process to the back side of the
thyroid cartilage. You can appreciate that any movement of the
arytenoid cartilage will have an effect on the placement of the
vocal cords (making them loose or taut, bring them together or
spreading them apart).
The epiglottis is attached inferiorly to the thyroid cartilage
by a small stem. Its lateral and superior borders are free. The
superior border can be seen through the oral cavity.
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Anterolateral View 
Posterior View |
| Various parts of the larynx area closed by connective tissue
membranes. The thyrohyoid membrane was seen in the study of the neck and is pierced by the internal laryngeal nerve and superior laryngeal artery. It extends from the upper border of the thyroid cartilage to the greater wing of the hyoid bone. The quadrangular membrane is free at the top and bottom but attached posteriorly to the arytenoid cartilage and anteriorly to the side of the epiglottis. The lower free margin forms the false vocal cord (or vestibular fold). The cricothyroid membrane (or conus elasticus) extends from the upper margin of the cricoid cartilage to attach to the back of the thyroid cartilage anteriorly and the arytenoid cartilage posteriorly. Its upper free margin is the vocal ligament (true vocal cord). |
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| The muscles of the larynx can be difficult to clean and identify. They
consists of muscles that change the opening of the glottis as well as the
tenseness of the vocal cord, thereby keeping it open for respiration and
helps us vocalize. The cricothyroid muscle lies anterior and external to the larynx and was identified in the study of the muscular triangle of the neck. It arises from the cricoid cartilage and attaches into the inferior horn and lower margin of the thyroid cartilage. When it contracts, it pulls the thyroid cartilage forward, increasing the distance between the thyroid and arytenoid cartilages and tensing the vocal cord. It is supplied by the external laryngeal branch of the superior laryngeal nerve (X). |
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| By removing one lamina of the thyroid cartilage, you can see the lateral cricoarytenoid muscle. As can be seen in the diagram, this muscle arises from the upper border of the cricoid cartilage and inserts onto the muscular process of the arytenoid cartilage. |
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| The remainder of the major muscles can be seen from the back of the
larynx. Located in the upper part of the aryepiglottic fold is the
aryepiglottic muscle. It is attached to the lateral border of the
epiglottis and becomes the oblique arytenoid which then attaches into the
arytenoid cartilage. This muscle works as a purse string to close the
opening of the larynx when swallowing, protecting the larynx. Running from arytenoid to arytenoid cartilages is the transverse arytenoideus muscle. This muscle pulls the arytenoids together when they contract. Lastly, we have the posterior cricoarytenoid muscles. They arise from the expanse of the cricoid lamina and insert into the muscular process of the arytenoid cartilages. These are the only muscles that open the space between the vocal cords (abduct). Another muscle, not shown, is the thyroarytenoideus. This muscle extends from the back of the thyroid cartilage to the front side of the arytenoid cartilage. It pulls the arytenoid cartilage forward when it contracts, thus loosening the vocal ligament. The deep upper part of this muscle is the vocalis muscle. This muscle can change the tenseness of small segments of the vocal cord in order to vary tonal qualities of our voice. |
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| I consider that the major function of the larynx is to keep the airway
open. This means keeping the space between the vocal cords (rima
glottidis) open. If it isn't open, we don't breathe so the second function
doesn't matter. The second important function is vocalization and this is a very complicated procedure that requires a variety of parts of the body to function together. Figure 1 points out the parts of the larynx involved in breathing and vocalization.
Figure 2 shows the movements that take place between the arytenoid and
cricoid cartilages (cricoarytenoid joints). The dot in the arytenoid
cartilage is the vertical axis around which the arytenoid cartilage
rotates.
Figure 3 shows the action of the transverse arytenoideus muscle. The arytenoid cartilages are pulled towards each other, thus closing the rima glottidis.
Figure 4 shows that the lateral cricoarytenoid muscles adduct the
arytenoid cartilages to close the rima glottidis.
Figure 5 demonstrates that the thyroarytenoideus muscle pulls the
arytenoid cartilages forward, thereby loosening the vocal cord.
Figure 6 shows the only abductor, the posterior cricoarytenoideus
muscle. This muscle rotates the arytenoid cartilages laterally
(abduct), causing the vocal cords to separate from one another,
opening the rima glottidis.
Figure 7 shows the cricothyroid muscle. As mentioned before, this
muscle is external to the larynx and can be seen in the muscular
triangle of the neck. This muscle rotates the thyroid cartilage
forward around an axis through the cricothyroid joint. This action
stretches the vocal cord, thereby tensing it.
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Figure 1. Figure 2.  
Figure 3. Figure 4.  
Figure 5. Figure 6 
Figure 7. |
| In considering the process of speech, you must first understand that
sounds are produced by blowing air past the vocal cords. The air produces
vibrations in the vocal cords, forming the sounds that come out of the
mouth. The air is pushed out of the lungs by relaxing the diaphragm and
contracting muscles of the abdominal wall. The abdominal muscles are
supplied by the lower intercostal nerves.
The tonal and pitch variations occur when the vocal cord is made more
tense or looser. Tense cords produce higher pitch, loose cords form
lower pitch. The muscles involved are supplied by the
recurrent laryngeal and
external laryngeal nerves.
Also changing the vocal cords, we have the
stylopharyngeus muscles that pull the pharynx and larynx upward. This
serves to shorten the tubal length of the air passage between the base
of the skull (body of sphenoid) and the vocal cords. As found in an
organ, longer pipes are low pitch and shorter pipes are high pitch.
The stylopharyngeus are supplied by the
glossopharyngeal nerves.
The suprahyoid muscles (digastrics,
geniohyoid) pull the hyoid bone up and the larynx follows it. The
anterior digastric is supplied by the
nerve to mylohyoid. The posterior belly
of the digastric is supplied by the
facial nerve. The geniohyoid muscle is
supplied by C1.
The infrahyoid muscles (sternothyroid,
omohyoid) pull the larynx down. They are supplied by branches of
the ansa cervicalis (C1-C3).
The tongue is used to add various
inflections to our voice by varying its surface contour
(intrinsic muscles) supplied by the
hypoglossal nerve.
Muscles of facial expression, especially
around the mouth and cheeks, are also used to vary the quality
of our speech, facial nerve.
Finally, if you notice what must move
when we speak, the mandible moves up and down by contraction
of the muscles of mastication,
mandibular division of trigeminal nerve.
This description of speech
production is an oversimplification, but gives you an idea
of just how many nerves and muscles are involved in
providing us with the ability to speak.
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Another function of the muscles of the larynx is protection of the airway. The major muscle that performs this protection is the aryepiglottic muscle. When you swallow, the aryepiglottic muscle closes off the entrance to the larynx through a purse-string action. It pulls the sides of the epiglottis back and narrows the inlet to the larynx. Muscle responsible is supplied by the recurrent laryngeal nerve. To help in this protection, all muscles that adduct or tense the vocal cord can also narrow the rima glottidis protecting the trachea and lungs.
The cough reflex is also designed to protect the air way. Should
something get into the vestibule of the larynx, sensory fibers from the
internal laryngeal nerve
carries a signal to the central nervous system and from there an impulse
is sent to the abdominal muscles which then force a blast of air through
the larynx which expels the foreign object.
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| The sagittal view of the larynx reveals relationships that aren't
otherwise seen. The aryepiglottic folds form the borders of the opening to the larynx. You can see that they extend from the epiglottis to the arytenoid cartilages. The first space in the larynx is called the vestibule which extends down to the vestibular fold (false vocal cord). Just beneath the vestibular fold is the ventricle which extends laterally and is connected anteriorly to a small sac called the saccule. The saccule has special secretory cells that produce a secretion to keep the vocal cords moist. Beneath the ventricle is the true vocal cord that extends from the vocal process of the arytenoid cartilage to the back side of the thyroid cartilage. The thin space between the left and right vocal cords is called the rima glottidis through which air must pass in order to vocalize and breathe. The area below rima glottidis is called the infraglottic cavity. Below the infraglottic cavity is the trachea. |
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Motor innervation
Sensory innvervation
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