Superficial Structures of the Neck 3 Flashcards
Where do strap muscles get their nerve supply from?
From the upper cervical ventral rami.
Which upper cervical ventral rami hitch hike along the hypoglossal nerve?
The ones from C1.
What do fibres from C1 leave the hypoglossal nerve as?
They leave the nerve as the superior root of the ansa cervicalis.
What do the other upper cervical ventral rami form?
They form the inferior root of the ansa cervicalis.
When do the superior and inferiro root of the ansa cervicalis join?
They join as a U shaped loop on the common carotid artery and the internal jugular vein.
Where do branches of the ansa enter?
They enter the strap muscles.
Describe how a nerve containing only C1 fibres works independently of the ansa for the strap like muscle.
A small nerve containing only C1 fibres leaves the hypoglossal nerve separately and enters the thyrohyoid muscle and the geniohyoid muscle.
What do the strap muscles act on?
They act on they hyoid bone and the larynx.
What can the strap muscles do to the hyoid?
- depress the hyoid
- with the muscle on the floor of the mouth, they can fix the hyoid
Why is fixation of the hyoid significant?
It is significant because it provides a stable bony basis on which the tongue can move.
When can we see the action of the strap muscles on the larynx?
We can see their action during swallowing.
- thyrohyoid elevates the thyroid cartilage towards the hyoid
- sternothyroid depresses the larynx
- rise and fall of the larynx can be seen during swallowing
Which are the 2 muscles in the neck that have 2 bellies?
- digastric
- omohyoid
How are the 2 bellies of the digastric and omohyoid muscles united?
They are united by a small intermediate tendon.
What does the small intermediate tendon slide through?
It slides through a small fibrous fascial sling.
Where does the anterior belly of the digastric muscle arise from?
It arises from a depression on the mandible beneath the chin.
Where does the posterior belly of the digastric muscle arise from?
It arises from a notch on the medial side of the mastoid process on the cranial base.
Where is the fibrous pulley that the intermediate tendon attached to?
It is attached to they hyoid bone.
What is the synovial tendon surrounded by?
They are surrounded by a synovial sheath to minimize friction.
Describe the nerve supply to the 2 bellies of the digastric muscles.
They are supplied by 2 different nerves and this shows that they have differing developmental origins.
Where does the anterior belly of the digastric muscle recieve its nerve supply from?
From a small branch of the mandibular division of the trigeminal nerve.
Aside from the anterior belly of the digastric nerve, what other muscle does the mandibular division of the trigeminal nerve (Viii) supply?
Supplies the mylohyoid muscle in the floor of the mouth.
What is the posterior belly of the digastric nerve supplied by?
It is supplied by the facial nerve (VII)
What does the action of the digastric muscle depend on?
It depends on whether or not the hyoid bone is fixed.
What is the action of the digastric muscle when the hyoid bone is unfixed?
The muscle raises that bone – this action is seen during swallowing.
What is the action of the digastric muscle on the fixed hyoid bone?
The digastric muscle + infrahyoid strap muscles on a fixed hyoid bone –> opens the mouth by lowering the mandible.
What are the bellies of the omohyoid muscle called?
They are called the superior and inferior belies and these are united by a small intermediate tendon as well.
Where does the inferior belly arise from?
It arises from the upper part of the scapula and passes forwards over the root of the neck.
Where does the superior belly of the omohyoid arise from?
It arises from the inferior border of the hyoid bone.
Where does the fascial sling that the intermediate tendon of the omohyoid muscle passes through attach to?
It attaches to the fascia on the deep surface of the sternocleidomastoid muscle.
How does the omohyoid muscle act on the hyoid bone?
In the same way as the strap muscles and it also has the same nerve supply as the strap muscles.
What do the lymph nodes in the neck lie in close relationship with?
They lie in close relationship with the jugular vein and either the digastric or omohyoid muscles.
Where do lymph nodes lying above the digastric muscles belong to?
They belong to the floor of the mouth.
Where is a deep group of cervical lymph nodes strung along?
Strung along the internal jugular vein and carotid sheath.
Where do the deep group of cervical lymph nodes recieve blood supply from?
From more superficial groups of regional lymph nodes in the neck.
How are the superficial groups of regional lymph nodes in the neck divided?
They are divided descriptively into 4 groups.
What are the regional nodes behind the internal jugular vein called?
They are called the posterior nodes.
What are the regional nodes in front of the internal jugular vein called?
They are called the anterior nodes.
What are the regional nodes that are the upper members of each group called?
They are called superior nodes.
What are the regional nodes that are the lower members of each group called?
They are called inferior nodes.
What is the jugulodigastric node?
This is the node that lies in the angle between the digastric and the jugular vein.
What drains into the jugulodigastric node?
Lymphatics from the tonsil and the back of the tongue.
Therefore this node can become painful and enlarged during tonsilitis.
What group of nodes does the jugulodigastric nodes belong to?
It belongs to the anteroposterior group.
Where does the anteroinferior group lie?
Lies just above the clavicle.
What is the anteroinferior group of nodes also called?
It is also called the supraclavicular nodes.
Why are the supraclavicular nodes important?
Because some of the trunk and the upper limb lymph drains through them on its way to the great neck veins.
What can we say about cancer of the breast that has a secondary deposit in a supraclavicular node?
We can say that it has already invaded the thoracic cavity through the internal thoracic nodes.
What other type of cancer other than breast cancer can we find a secondary deposit of in the supraclavicular nodes?
Carcinoma of the stomach.
What is another named node of the postero-inferior group?
The jugulo-omohyoid node.
How does venous drainage from the lower facial region and the temple pass into the neck?
Through the retromandibular vein and the posterior auricular vein.
Where does the retromandibular vein divide?
It divides deep to the parotid gland.
