General Organisation of the Head and Neck Flashcards
How many cranial bones are there?
22
Which vertebrae does the thyroid gland span between?
C5-T1
What does the platysma muscle lie in?
Superficial cervical fascia
Describe the location of the platysma muscle
Runs from lower mandible, over clavicle and attaches to the chest wall
What is the action of platysma?
Depresses corners of mouth and assists in depression of the jaw
What nerve supplies the platysma?
Cervical branch of the facial nerve
What are the attachments of sternocleidomastoid?
Arises from sternum and clavicle, inserts into mastoid process
What are the actions of sternocleidomastoid?
Rotation of the head to the opposite side and flexion of the neck
What nerve supplies sternocleidomastoid?
Accessory nerve
What are the origins of trapezius?
External occipital proruberance, superior nuchal line, spinal processes of vertebrae
Where does trapezius insert?
Spine of scapula and lateral 1/3 of clavicle
What do the superior fibres of trapezius do?
Elevate shoulders
How is trapezius innervated?
Accessory nerve
What are the borders of the anterior triangle of the neck?
Superiorly - inferior border of mandible
Laterally - anterior margin of sternocleidomastoid
Medially - imaginary midline of neck
What are the four suprahyoid muscles?
Stylohyoid, digastric, mylohyoid and geniohyoid
What are the four infrahyoid muscles?
Omohyoid, sternohyoid, thyrohyoid and sternothyroid
What are the borders of the carotid triangle?
Superiorly - posterior belly of digastric
Laterally - medial border of sternocleidomastoid
Inferiorly - Superior belly of omohyoid
What are the contents of the carotid triangel?
Common carotid artery (which bifurcates in the triangle)
External jugular vein
Hypoglossal and vagus nerves
What is the carotid sinus?
A dilated portion of the common carotid and internal carotid arteries that contains baroreceptors which monitor blood pressure
What does the superficial cervical fascia include?
Fat, platysma, cutaneous nerves, lymph nodes and superficial blood vessels
Where is the superficial cervical fascia?
Between dermis and deep cervical fascia
What are the layers of the deep cervical fascia?
Investing layer
Carotid sheath
Pre tracheal layer
Pre vertebral layer
Which is the most superficial layer of the deep cervical fascia?
Investing layer
Where is the pretracheal layer situiated?
Anteriorly in the neck - spans between hyoid bone and thorax
What things are enclosed by the pretracheal fascia?
Trachea, oesophagus, thyroid, infrahyoid muscles
What two parts can the pretracheal fascia be divided into?
Muscular - encloses infrahyoids
Visceral - encloes thyroid, trachea and oesophagus
What is the posterior aspect of the visceral fascia formed by?
Contributions from the buccopharyngeal fascia (fascial covering of the pharynx)
What does the prevertebral fascia surround?
Vertebral column and its associated muscles
What are the borders of the posterior triangle?
Anteriorly - posterior border of the scm
Posterorly - anterior border of trapezius
Inferiorly - middle 1/3 of clavicle
What is the floor of the posterior triangle formed by?
Prevertebral fascia
What is the axillary sheath?
Sheath that encloses the axillary artery and the axillary vein and the three cords of the brachial plexus
What is the carotid sheath formed by?
Contributions from the pretracheal, prevertebral and investing fascia layers
What are the contents of the carotid sheath?
Common carotid artery (bifurcates in sheath)
Internal jugular vein
Vagus nerve
Cervical lymph nodes
How can an infection that occurs posterior to the prevertebral fascia get to the thorax?
It can erode through the prevertebral fascia and drain into the retropharyngeal space which extends down into the thorax
What is the retropharyngeal space?
Space between the pretracheal and prevertebral fascial layers
Which spaces in the neck extend inferiorly into the mediastinum?
Retropharyngeal space and pre-tracheal space
What two types of muscle are there in the face and how are these innervated?
Muscles of facial expression - facial nerve
Muscles of mastication - trigeminal nerve
What are the three key branches of the trigeminal nerve?
Opthalmic, maxillary and mandibular
What is the main sensory nerve of the face and scalp?
Trigeminal
What is the motor function of the trigeminal nerve?
Motor innervation to muscles of mastication
What are the five key branches of the facial nerve?
Temporal, zygomatic, buccal, mandibular and cervical
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What are the layers of the scalp?
Skin Connective tissue (dense) Aponeurosis (epicranial) Loose connective tissue Periosteum (outer layer of skull bones)
Where does the periosteum become continuous with the endosteum?
At the suture lines
What is the danger area of the scalp and why?
Loose connective tissue - pus and blood can spread easily within it and pass into the cranial cavity along emissary veins
Describe the arterial supply of the scalp
Exxternal carotid artery and opthalmic
Why do deep lacerations to the scalp tend to bleed profusely?
1) The pull of the occipitofrontalis muscle prevents closure of the bleeding vessel and skin
2) Blood vessels to the scalp are adhered to the dense CT so prevents the vasoconstriction that usually occurs
3) Blood supply to the scalp consists of many anastomoses which contribute to profuse bleeding
Why doesn’t loss of blood supply to the scalp lead to bone necrosis?
Blood supply to the skull comes from the middle meningeal artery
