General Organisation Flashcards
What is the definition of fascia? What purpose does it serve? Why is it important to know about? Give some examples of fascia.
FASCIA = connective tissue (therefore mesenchymal origin) forming layers of variable thickness in all regions of the body. Superficial fascia is found immediately beneath the skin. Deep fascia envelops organs and tissues
- eases movement of muscles by reducing friction
- lines all organs, separating tissues of the body into compartments
- binds tissues together (therefore spaces do not exist normally; potential spaces exist)
Determines spread of infection
Loose connective tissue (superficial fascia) = adipose tissue
Dense regular connective tissue (muscle) = tendons/aponeurosis
Dense irregular connective tissue (dermis) = deep fascia
What are the anatomical boundaries of the anterior triangle of the neck?
Anterior: median vertical line of the neck
Superior: inferior margin of the mandible
Posterior: anterior margin of sternocleidomastoid
What are the anatomical boundaries of the posterior triangle of the neck?
Anterior: posterior margin of the sternocleidomastoid
Posterior: anterior margin of trapezius
Inferior: middle 1/3 of the clavicle
What are the major contents of the anterior triangle of the neck?
Major structures that pass between the head and thorax:
- major arteries (e.g. common carotid) and veins (e.g. internal jugular vein)
- oesophagus
- larynx
- pharynx
- thyroid gland
What are the major contents of the posterior triangle of the neck?
Structures passing into and out of the upper limb (axillary inlet - brachial plexus under facial floor):
- fat
- lymph nodes
- spinal accessory nerve
- external jugular vein
- suprascapular artery
Outline the attachments and innervation of the trapezius and sternocleidomastoid.
TRAPEZIUS attaches to:
- vertebrae C1-C7 by ligamentum nuchae
- external occipital protruberance
STERNOCLEIDOMASTOID attaches to:
- mastoid process (bilateral)
- sternum (one head)
- clavicle (one head)
Both innervated by spinal accessory nerve (CNXI)
What are the subdivisions of the anterior triangle of the neck?
Submandibular/digastric triangle
Submental triangle
Carotid triangle
Muscular/visceral triangle
What are the muscles of the anterior triangle of the neck?
SUPRAHYOID: elevate hyoid and larynx during swallowing
Superficial:
- digastric (2 heads, change angle under fibrous band)
- stylohyoid
Intermediate: mylohyoid
Deep: geniohyoid
INFRAHYOID: depress hyoid and larynx during speech or swallowing
Superficial:
- sternohyoid
- omohyoid (2 heads, change angle under fibrous band)
Deep:
- sternothyroid
- thyrothyroid
What are the different layers of the neck?
Skin
Subcutaneous fat/superficial fascia
Platysma muscle: thin band-like muscle extending from mandible to clavicle on both sides of ANTERIOR neck (but deficient in the middle)
Investing/deep cervical fascia: tight “collar” of fascia separating compartments (increases tension —> allows continuity of movement)
What are the different types of fascia present in the neck beneath the deep cervical fascia?
Pretracheal fascia: encloses trachea, oesophagus, and thyroid
Carotid sheath: contains common carotid artery (ant. -> med.), internal jugular vein (ant. -> lat.), vagus nerve (post.), deep cervical lymph nodes
note: pretracheal fascia and carotid sheath are fused
Prevertebral fascia: contains muscles surrounding the vertebrae (base of skull -> T2/T3
Describe how infection would spread in each space within the fascia of the neck, and what the consequences of this might be.
Superficial infections (outside the deep cervical fascia): e.g. cellulitis, abscesses —> fluctuant spread
Within retropharyngeal space: skull base —> diaphragm (mediastinitis)
note: rare; 2-4yrs, keeps head still, lymph node involvement
e.g. retropharyngeal abscess: pus accumulates in retropharyngeal space, between prevertebral fascia and the buccopharyngeal membrane —> compresses pharynx —> dysphagia and dysarthria (unclear pronunciation)
Within parapharyngeal space: skull base —> mediastinum (T2/T3)
note: rare; due to dental abscesses/tonsillitis spread, & can affect carotid sheath structures e.g. jugular vein thrombosis
Name the branches of the internal carotid artery present in the neck.
NONE
1st branch of internal carotid artery is the occipital, which does not enter the neck
How might the sternocleidomastoid muscle be damaged in newborns? How does this damage manifest?
Torticollis
Causes:
- congenital: fibrous tissue tumour in sternocleidomastoid
- acquired: torn during difficult birth/damaged by compression or pulling by forceps in delivery/damaged due to spending too long lying on back (why babies’ heads need to repositioned regularly)
Contraction/shortening of cervical muscles (dystonia) makes neck twist and head tilt (on affected side)
Contrast the neurocranium and the viscerocranium.
NEUROCRANIUM = cranial skeleton (calvaria + cranial base)
- supplied by internal carotid artery
note: calvaria = “skullcap”; dome-like superior portion of cranium (superior portions of frontal, parietal, and occipital bones)
VISCEROCRANIUM = facial skeleton (ethmoid, mandible, maxilla, zygomatic, nasal, lacrimal, palatine)
- supplied by external carotid artery
How does the neonatal skull differ to an adult skull?
- facial skeleton small at birth
- alveolar processes & paranasal sinuses rudimentary at birth
- fontanelles present (large membranous, unossified gaps between skull bones) which allow the head to deform during passage through birth canal, + open sutures
What occurs when the frontal bones fail to fuse? What occurs when the frontal bones fuse prematurely?
Persistent metopic suture (median frontal suture)
note: no clinical significance, but can be mistaken for cranial fractures
Premature fusion = metopic synostosis —> trigonocephaly
What complications can occur during childbirth resulting from the relative small size of the foetal mastoid processes?
Facial nerve emerges directly from the stylomastoid foramen onto the lateral surface of the skull
+ mastoid air cells do not develop until aged 2-3yrs
= facial nerve exposed —> increased risk of damage —> increased risk of facial nerve palsy/paralysis
note: after birth there is an increased risk of otitis media with effusion when the mastoid air cells are particularly small
What is the antrum of the facial skeleton?
Maxillary sinus
What is Paget’s disease of the bone? How does it affect the skull?
Osteitis deformans
Grossly disordered bone remodelling (irregular, woven trabecular bone with large osteoclasts) where formation exceeds resorption —> skull enlargement —> bone of middle cranial fossa remodelled —> progressive loss of hearing
Inflammation of periosteum of cranial bones —> headaches
Unknown aetiology
note: teeth can be displaced/fused with bone —> risk of severe haemorrhage during oral surgery
Why might a fracture of the lower mandible cause numbness of the lower lip?
Mandibular nerve (CNV3) splits into inferior alveolar nerve as it moves over the mandible
Inferior alveolar nerve exits via mental foramen to supply the mucous membranes of lower lip and chin
Blocked during dental surgery
What is the function of ligamentum nuchae? Where does it attach?
Continuation of interspinous and supraspinous ligaments of thoracic and lumbar vertebrae
Thickened fibroelastic tissue
Attaches to:
- external occipital protruberance
- posterior border of foramen magnum
- spinous processes of cervical vertebrae
Preserves the normal curvature of the cervical spine
Why are cervical vertebrae prone to dislocation in whiplash injuries?
Articular facets of the cervical vertebrae are more horizontally orientated, so the vertebrae are less tightly interlocked
Less energy required to dislocate than fracture
note: due to large vertebral foramina, slight dislocations can occur without damaging the spinal cord
note: whiplash injuries can be caused by both hyperextension of the neck (can tear ant. longitudinal ligament) and hyperflexion of the neck (can dislocate vertebral arches)
How can severe whiplash injuries cause death?
Fracture of the vertebral arch of the axis (C2) - hangman’s fracture:
If the body of C2 is displaced anteriorly with respect to the body of C3, this compresses the spinal cord, which can cause quadriplegia or death (if spinal cord compressed above phrenic nerve outflow —> respiration ceases)
Ruptured ant. longitudinal ligament & annulus fibrosus of C2-C3 intervertebral disc —> cranium, C1, & dens and body of C3 separated from rest of axial skeleton —> severs spinal cord
By which route might you aspirate a subdural haematoma in a baby?
Through open suture and anterior fontanelle of cranium (percutaneously) —> through dura mater and into subdural layer
Direct needle laterally, i.e. between the membranous portions of the frontal and parietal bones
What are the most important orbital muscles of facial expression? (More needed?)
Orbicularis oculi: protects cornea by closing eyes
- orbital: forceful closure of eyelids
- palpebral: gentle closure of the eyelids
Corrugator supercili: draws eyebrows medially and downwards (vertical wrinkles on bridge of nose)
What are the most important nasal muscles of facial expression? (More needed?)
Nasalis:
- alar: opens nares
- transverse: compresses nares
Procerus: pulls medial angle of eyebrows downward to produce transverse wrinkles in nose
Depressor septi nasi: pulls nose inferiorly (opens nares)
What are the most important oral muscles of facial expression? (More needed?)
Orbicularis oris: purses the lips (closes and protrudes lips)
- loss of —> mouth droops & drools
Buccinator: pulls cheek inwards against the teeth (preventing accumulation of food in that area) & compresses distended cheeks
Motor innervation = mandibular branch of motor root of facial nerve
List some of the minor facial muscles. (More needed?)
Upper:
- risorius
- zygomaticus major & minor
- levator labii superioris
- levator labii superioris alaeque nasi
- levator anguli oris
Lower:
- depressor anguli oris
- depressor labii inferioris
- mentalis
+ ant., sup., & pos. auricular (ear upwards & backwards)
+ occipitofrontalis
- frontal belly: wrinkles forehead, raises eyebrows
- occipital belly: draws scalp backwards
Which nerves provide the sensory innervation of the face and neck?
Face = cutaneous branches of trigeminal nerve (CNV):
- ophthalmic (CNV1)
- maxillary (CNV2)
- mandibular (CNV3)
Neck = cutaneous branches of cervical plexus (neck, parotid region, angle of mandible) - transverse cervical nerve (C1 & C2)
What nerve branches run through the parotid gland?
Facial nerve extracranial branches: To Zanzibar By Motor Car
- temporal
- zygomatic
- buccal
- mandibular
- cervical
(+ posterior auricular?)
Why does parotidectomy/parotid gland carcinoma cause facial weakness and impaired sensation? (More needed?)
Facial nerve compression
Muscles of facial expression affected
What are the muscles of the posterior triangle of the neck?
- sternocleidomastoid
- trapezius
- omohyoid
- levator scapulae
- anterior, middle, and posterior scalene muscles
- splenius capitis
What are the contents of the carotid sheath?
- common carotid artery —> internal carotid artery (superior part of sheath only)
- internal jugular vein
- vagus nerve
- deep cervical lymph nodes
note: carotid sheath closely related to pretracheal, prevertebral, and investing layers of deep fascia
What are the boundaries and contents of the carotid triangle?
Superior boundary: posterior belly of digastric
Medial boundary: superior belly of omohyoid
Lateral boundary: anterior border of sternocleidomastoid
- internal jugular vein
- bifurcation of common carotid (therefore can palpate carotid pulse)
- vagus nerve
- hypoglossal nerve
What anatomical structures in the head and neck are derived from somites?
Platysma
Orbicularis oris
Other lower lip muscles
What is the key difference between muscles of facial expression and other skeletal muscles?
Face is lacking in deep fascia, so the muscles insert deep into the skin —> contraction results in changes in facial expression
Reminder: what is the definition of a motor unit?
Combination of a motor nerve and the muscle fibres it supplies
How can C1-C6 be discerned?
C1 = hard palate
C2 = angle of mandible
C3 = hyoid bone
C4 = upper border of thyroid cartilage
C5 = lower border of thyroid cartilage
C6 = cricoid cartilage
What are some important landmarks present at C6 in the neck?
- junction of larynx with trachea & junction of pharynx with oesophagus
- vertebral arteries enter transverse foramina of C6 vertebrae
- carotid pulse (felt by pressing common carotid artery against carotid tubercle of transverse process of C6 vertebra)
- inferior border of cricoid cartilage
- superior belly of omohyoid crosses carotid sheath
- inferior thyroid artery enters thyroid gland & middle thyroid vein emerges from thyroid gland
- middle cervical sympathetic ganglion
