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 Dr.Shreen, Sheet #4 - 14\2\2012

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Majed Sharayha

Posts : 130
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Join date : 2011-08-23
Age : 26

PostSubject: Dr.Shreen, Sheet #4 - 1422012   Fri Feb 17, 2012 1:00 am

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Anterior triangle
The Neck has been already divided into two main triangles:
Anterior triangle.
Posterior triangle.
A quick review to the posterior triangle: -
Anteriorly: posterior border of sternomastoid muscle .
Posteriorly: anterior border of trapezius muscle.
Base: middle one third of the clavicle bone.
Apex: The overlapping between the two muscles
{Sternomastoid & Trapezius}
Floor :
Prevertebral muscles covered by prevertebral fascia.
Contents :
Brachial plexus (Roots & Trunks with their branches).
Subclavian artery.
Subclavian vein.
The 1st and 2nd contents of the floor are behind scalenous anterior muscle {one of the prevertebral muscles} which is covered by prevertebral fascia, so all the contents that are behind scalenous anterior muscle are also covered with prevertebral fascia, except:
Subclavian vein, because it is anterior to scalenous anterior muscle.
Spinal part of accessory nerve which lies in the roof of the posterior triangle (in the investing layer of deep fascia).
Remember from the 1st semester: Accessory nerve is cranial nerve (XI) that has two roots:
Cranial Root.
Spinal Root That innervates Trapezius muscle .
The Prevertebral fascia continues as Axillary fascia in the axillary region.
Thus, axillary fascia is the continuation of prevertebral fascia that also covers the brachial plexus and the arteries in the axilla.

Anterior triangle
Anteriorly : midline
Posteriorly : anterior border of sternomastoid
Superiorly : base of the mandible
Roof :
Platysma muscle.
Anterior jugular vein.
Note: There are small veins under the chin called submental veins; the union between these small veins will result in the formation of the Right & Left Anterior Jugular veins.
{jugular veins = veins related to the neck}
Anterior Jugular vein continues behind the sternomastoid muscle and eventually it drains in the External Jugular vein.
Cutaneous Innervation Transverse Cervical Nerve (Root Value: C2,C3).

Due the numerous floor contents of the Anterior Triangle it is further divided into another 4 main Triangles:
Submental triangle ( One Single Triangle in the midline).
Submandibular triangle (Right and Left Pairs).
Carotid triangle (Right and Left Pairs).
Muscular triangle (Right and Left Pairs).

{Submental Triangle}
This is a single triangle in the midline beneath the chin.
Boundaries :
In the both sides: (Right and Left sides) the Anterior bellies of digastric muscle.
Inferiorly: Hyoid Bone
Digastric muscle: has anterior & posterior bellies joined by intermediate ligament.
Hyoid bone.
Small isolated U-shaped bone in the neck.
It is isolated because it has no boney attachment fixed by muscles and ligaments.
Muscles above hyoid bone are called Suprahyoid muscles.
Muscles below hyoid bone are called Infrahoid muscles.
These muscles are responsible for fixation the hyoid bone.
Mylohyoid muscle (the muscle of the floor of the mouth).
Submental lymph nodes.
Submental artery {Supply the mylohoid muscle}.
Submental veins {That give rise for anterior Jugular vein that will drain on the External Jugular Vein}.
{Submandibular triangle}
Anteriorly: anterior belly of digastric muscle.
Posterior belly of digastric muscle.
Stylohyoid muscle:
A muscle that is situated on the upper border. of the posterior belly of digastric.
Origin: styloid process.
Insertion: hyoid bone.
Base : base of the Mandible.
Floor : Mylohyoid muscle (Continuation from the submental triangle).
Note: Since that the Submandibular triangle is surrounded by the Digastric muscle Anteriorly and Posteriorly; it can be also called: {Digastric Triangle}.
Submandibular salivary gland.
Facial Artery:
The most important arterial supply of the face.
It is a branch from the External Carotid Artery.
Course {In the Neck}:
Begins in the submandibular triangle {Digastric Triangle} and forms a groove on the posterior aspect of the submandibular salivary gland.
Then it situated between the gland and the mandible.
Then it pierces the deep fascia of the neck at the antero-inferior angle of masseter muscle.
Then it continues its course on the face (As Explained Before).
Facial vein:
As known, the union of supratrochlear and supraorbital veins give rise to Anterior facial vein.
Anterior facial vein unites with anterior division of retro-mandibular vein and form the common facial vein accompany with facial artery.
then drains in the internal jugular vein.
Submandibular lymph nodes.
Hypoglossal nerve (Cranial nerve number XII) motor innervation to the muscles of the tongue (glossal = tongue) .
Course :
It goes out from skull pass inside the submandibular triangle and then deep to the mylohyoid muscle then it reaches the tongue.
{Carotid triangle}
Superiorly: posterior belly of digastric.
Posteriorly : anterior border of sternomastoid.
Anteriorly : superior belly of omohyoid muscle.
Omohyoid muscle:-
It has two bellies:-
Superior belly of omohyoid Attached to the Hyoid Bone.
Inferior belly of omohyoid Attach to the scapula.

Muscles of the floor of this triangle are the middle and inferior constrictors of the pharynx which help in closing the pharynx.
The Carotid sheath that covers the vessels has 3 contents .(Artery, vein, Nerve):-
Artery: Common carotid artery (Medially).
Vein: Internal jugular vein (Laterally).
Nerve: Vagus nerve (Cranial nerve number X)
{Located in between and posterior to 1 and 2}.
Also, there is a nerve that is anterior to the carotid sheath and a nerve that is posterior to the carotid sheath.
The Anterior Nerve U-shape (Loop Like) called Ansa Cervicalis (Root Value: C1, C2, C3).
The Ansa Cervicalis is a union of two limbs:-
Anterior descending limb.
Posterior descending limb.
Anterior descending limb:
It is the Cervical nerve Number 1 (C1), it comes from the back (vertebral column).
It innervates muscles in the anterior aspect of the neck, thus we call it descendens hypoglossi.
The journey of C1 root from the back to the anterior aspect of the body is accompanied with the hypoglossal nerve until both nerves reach the carotid triangle and then they separate.
The Hypoglossal goes to the lung.
The C1 root descends as descendens hypoglossi.

Posterior descending limb
Arises From the cervical plexus and another limb descends from it called descendens cervicalis (Root Value: C2+C3).
In Summary (descendens hypoglossi+ descendens cervicalis=Ansa Cervicalis)
The Ansa Cerviclais Innervates infrahyoid muscles.
The Posterior Nerve Group of Sympathetic Ganglia (Will be explained later on).
Now we will discuss the contents of the carotid sheath in more details:-
Common carotid artery:-
Right Common Carotid Artery Originated from Brachiocephalic Artery.
Left Common Carotid Artery Originated from Aortic Arch.

It Continues inside the carotid sheath; at the level of (C3,C4) it divides into two terminals.
Internal common carotid artery Run inside the skull.
External common carotid artery Run outside the skull.
The Internal common carotid has NO branches in neck; because it will supply the intracranial cavity.
The External common carotid has many branches in the neck {Distinguishing Feature between the two arteries}.
The Internal carotid artery stays inside the carotid sheath, unlike the External carotid artery which moves outside the carotid sheath to give its branches.
The Branches of the External Carotid Artery (From Downwards to Upwards).

Some Superior thyroid Artery
{supply Thyroid gland}
American Ascending pharyngeal Artery
{supply pharynx}
Ladies Lingual Artery {Supply the tongue}
Found Facial Artery
Our Occiptal Artery
Pyramids Posterior auricular Artery
So Superficial temporal Artery
Magnificent Maxillary Artery

Internal Jugular Vein:-
Runs from the base of the skull inside the carotid sheath.
At the beginning, it is lateral to the internal carotid artery.
After that, it will be lateral to the common carotid artery.
Then the Internal Jugular vein will unite with the Subclavian Vein forming the Brachiocephalic vein.
The Right and Left Brachiocephalic veins will form the Superior Vena Cava (As known from the First Semester).

The Tributaries of the Internal Jugular Vein:-

Some Superior thyroid vein

Magnificent Middle thyroid vein

Polish Pharyngeal vein

Ladies Lingual vein

Found common facial vein

Eyes inferior petrosal vein

{Muscular triangle}
In the middle : midline.
Superiorly: Superior belly of omohyoid .
Inferiorly: Anterior. border of sternomastoid.
Floor & contents:-
Infrahyoid muscles:-
sternohyoid muscle:-
Origin: back of the manubrium sterni.
Insertion :hyoid bone.
sternothyroid muscle:-
Origin :back of the manubrium sterni.
Insertion :oblique line of thyroid cartilage.
thyrohyoid muscle:-
Origin :oblique line of thyroid cartilage.
Insertion: hyoid bone.
Omohyoid muscle.
As we said before it has two bellies:-
Superior belly, originated from hyoid bone.
Inferior belly, originated from upper border of scapula.
Both Bellies join in an intermediate tendon that is deep to the sternomastoid muscle.
The Intermediate tendon is fixed by a loop of deep fascia around the omohyoid muscle.

Innervation (of the Infrahyoid Muscles):-
Ansa cervicalis innervates the infrahyoid muscles (all the mentioned muscles, except thyrohyoid muscle, which is innervated from C1).
Action (of the infrahyoid Muscles):-
We know that hyoid bone and thyroid cartilage are attached to the larynx’s cartilage.
The muscles that are attached to the hyoid bone and thyroid cartilage, can do elevation and depression to the larynx.
The muscle that Elevates the Larynx is: {Thyrohyoid}.
The Thyrohyoid Muscle, which is located above the thyroid cartilage, is the only muscle that elevates the larynx during the 2nd stage of deglutition, thus helping in closing the larynx with the epiglottis during deglutition of the bolus, avoiding it (the bolus) from entering the respiratory tract.
The Muscles that Depress the Larynx are: {Sternohyoid, Sternothyroid, Omohyoid}.
These muscles help in pulling the larynx downwards during the 3rd stage of deglutition.
All these muscles are important in the fixation of larynx during the movement of the tongue.
{PS: Refer to the Atlas for clear and full understanding.}
Sorry For Any Mistakes
Done by: Anfal Hassan
Special Thanks to:
Fahad Al-Aswad
Designed by: Khaldoon AlQaddumi
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Dr.Shreen, Sheet #4 - 14\2\2012
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