Blood supply and Beginning of the Skull Flashcards
What are the 3 layers of the deep cervical fascia from superficial to deep?
From superficial to deep
- Investing layer
- Carotid sheath
- Pre tracheal layer
- Pre vertebral layer
Which structures are enclosed by the investing layer?
Sternocleidomastoid
Trapezius
Submandibular
Parotid salivary glands
What are the complications of an infection that develops in the retropharyngeal space?
Can potentially spread from the neck into the thorax as far down as the posterior mediastinum risking development of a mediastinitis
Where does the retropharyngeal space lie?
Between the Pre-vertebral layer of fascia and the buccopharyngeal fascia (surrounding the pharynx)
Impingement of which nerve leads to loss of mastication?
Cranial Nerve 5 - Trigeminal nerve
Mandibular division supplies the muscles of mastication
Impingement or damage of which nerve leads to loss of facial expression?
Facial nerve
Only Motor Sign if impinged in Stylomastoid foramen
What is Bell’s palsy?
Inflammation of the facial nerve. Inflammation causes oedema and compression of the facial nerve as it runs through the internal acoustic meatus in the petrous part of the temporal bone
What can be used to examine the sternocleidomastoid?
Put hand on the patients neck and ask them to look over their shoulder
What can be used to test the accessory nerve?
Shrug against resistance to test damage to nerve that supplies the trapezius
What are the borders of the anterior triangle?
Superiorly: inferior border of the mandible
Laterally: Medial border of the sternocleidomastoid
Medially: Imaginary saggital line down the midline of the body
What are the borders of the posterior triangle?
Anterior: Posterior border of the sternocleidomastoid
Posterior: Anterior border of the trapezius muscle.
Inferior: Middle 1/3 of the clavicle.
What does inserting surgical airways carry the risk of?
Infection of the pre tracheal space
What are the 3 branches of the trigeminal nerve?
- Opthalmic division
- Maxillary division
- Mandibular division
Loss of sensation in the scalp correlates with which nerve?
- Trigeminal nerve which provides main sensory innervation to scalp and face
- Cervical nerve
What is the main arterial supply of the head and neck?
-Common carotid artery which is the main arterial supply via its terminal branches
What are the main venous drainage from the face, head and neck?
- Internal jugular vein which is the main venous drainage of head and neck structures.
- External jugular vein which also receives veins draining the scalp and face and runs more superficially than the IJV
What are the branches of the common carotid artery?
- Internal carotid artery
- External carotid artery (facial artery branch supplies the face)
Why is swallowing, movement of thence typically difficult and painful for a patient with a retropharyngeal abscess?
Compression of oesophagus causes pain to be elicited when moving the neck or swallowing
What are the extra-cranial branches of the facial nerve?
Superior to inferior
- Temporal (above the eyes at side of head)
- Zygomatic (nose region)
- Buccal (mouth region above the lip)
- Mandibular (mouth region below lip)
- Cervical (neck region)
How can the trigeminal nerve be tested?
- Movement of the jaw
- Sensation of the face
How can the facial nerve be tested?
- Smile
- Frown
- Closing eyes
- Raising eyebrows
How can the orbicularis oculi be tested?
-Close the eyes tightly and resist me trying to open them
How can the levator palpebrae superioris be tested?
Elevation of the upper eyelid (CN3)
What is the examination for for occipitofrontalis muscle?
Raise the eyebrow against resistance
What is the examination for the orbicularis oris?
Purse lips and try to pull it up
What is the examination for the buccinator?
Blow out cheeks and resist expulsion of air
What is the action of the Buccinator?
- Keeps food from spilling into the cheek to prevent it pooling between the cheeks
- Flattens cheek and holds the cheek close to the teeth when chewing.
Which muscles are innervated by the mandibular branch of the trigeminal nerve?
- Medial pterygoid
- Masseter
- Temporalis
- Lateral pterygoid
What is the examination for the temporalis?
Palpation during jaw clench
What layers would the scalpel penetrate before it reached the bone of the scalp?
- Skin
- Dense Connective tissue
- Epicranial aponeurosis
- Loose areolar connective tissue
- Periosteum
How is spread of bleeding within the subperiosteal layer limited?
There are membranous gaps in the sutures which the blood goes into which limits the spread of bleeding within the sub-periosteal layer.
Which suture can be found between the parietal bones?
Sagittal Suture
Which suture can be found between the frontal bone and parietal bones?
Coronal Suture
What suture can be found between the occipital bone and parietal bone?
Lambdoid suture
What are the 3 bowl shaped depression formed on the cranial floor?
- Anterior Cranial Fossae
- Middle Cranial Fossae
- Posterior Cranial Fossae
What is the trilaminar arrangement of the calvaria?
Outer Table (compact bone) Diploeic Cavity (spongy bone) Inner table (compact bone)
When does growth at sutures stop?
Puberty
Why are the edges of the bones of the skull serrated?
To prevent slippage and movement
Periosteum covering the outer table is continuous through to the periosteum covering the inner table. True/False
True
Where does a cephalohaematoma occur?
Occurs between the periosteum and outer table of bone
Can bleeding in a cephalohaematoma pass the suture lines?
It cannot cross the suture lines
What are the purposes of fontanelles?
- To allow for altering of the skull size and shape during child birth
- To permit growth of infant brain
When do the fontanelles fuse?
Posterior = 1 month to 3 months Anterior = 18 months to 2 years
What is early fusion of fontanelles and sutures called?
Craniosyntosis
What is the shape of the fontanelles?
Slightly convex shape in a healthy baby
What should be performed in all partients with known or suspected skull fractures?
CT scanning should be performed to identify intra cranial injuries
Why is the pterion particularly at risk of fracture?
It is the thinnest area of the skull. Fusion between parietal, temporal, frontal and sphenoid
What are the two main types of fractures?
Linear - pass full thickness of skull. It is failed strains and involve no bone displacement
Depressed - Fragment is displaced inwards towards the brain
What are basilar skull fractures and what are their risks and signs?
Fractures involving the cranial base
Risks
- Associated with cranial nerve injuries
- Prone to causing cerebrospinal fluid leaks
Signs
- Raccoon eyes
- Battle signs
- Haemotympanum
- CSF otorrhea
- CSF rhonorrhea
What is the risk with the pterion?
Intracranial Haemorrhage due to the injury to the middle meningeal artery. Extradural haematoma
What the 3 sacs around the brain and their properties?
Dura: tough fibrous membrane
Arachnoid: soft translucent membrane
Pia: microscopically thin, delicate and closely adherent to surface of brain
What are the layers of the dura?
Periosteal = endosteum lining the inner bones of skull Meningeal = Layers adjacent to arachnoi
What is the purpose of the dural folds?
Helps to stabilise the brain and act as Rigid dividers
What can a rise in pressure inside the skull lead to?
Compression and displacement of the brain against the rigid folds and/or through foramen magnum. (herniation)
- Subfalcine herniation
- Uncal herniation
- Tonsillar herniation
What are the effect of a rise in pressure on the cranial nerves?
Their roots have a close relationship with the dural folds so they can get squashed
What are dural venous sinuses?
Venous blood filled spaces created by separation of meningeal from periosteal layer of the dura.
Where does venous blood from the brain drain to?
Venous sinuses via the cerebral veins
Where is the confluence of sinuses found?
Deep to the protuberance of the occipital bone
Meeting of the superior Sagittal, straight sinus and the transverse sinus
How do cerebral veins within the subarachnoid space drain into the dural venous sinuses?
Bridging veins
What is a common cause of extradural haemorrhage and where does it occur?
Arterial bleed via the middle meningeal artery.
Bleeding occurs between the inner table of bone and periosteal
What is a common cause of subdural haemorrhage?
Venous bleed through the bridging veins.
What is subdural haemorrhage?
-Bleeding between the meningeal layer of the dura and the arachnoid mata.
Why doesn’t the bleed frimm a subdural haemorrhage spread across the brain?
Falx cerebri (dural folds) stops the spread across the side of the brain
Why are older people more susceptible to subdural haemorrhage?
- The Brian gets smaller as you get older
- Increase tension of the bridging veins
- A slight knock could cause the veins to rupture as a result
What usually cause a subarachnoid haemorrhage?
-Usually a branch of the circle of willis
Secondary to trauma or spontansous rupture of the blood vessel
What are the parts of the temporal bone?
- Squamous part
- Petromastoid part
- Tympanic plate
- Styloid process
What is the mastoid process?
- Palpable landmark posterior to the pinna
- Cavity of the mastoid antrum extends into the mastoid process and communicates with air cells
