Head and neck Flashcards
State the borders of the anterior and posterior triagles of the neck
- Anterior triangle -> ant=midline, post =ant SCM, sup=mandible, floor=vertebrae
- Posterior triangle-> ant=post SCM, post=ant trapezius, inf=clavicle, floor=scalene
State the contents of the anterior and posterior triangles
- Ant = carotid sheath (CCA, IJV, CNX), CNXII, submandibular, thyroid and parathyroid, lymph nodes
- Post = CNXI, subclavian a, EJV, brachial plexus trunks, lymph nodes
Where does the CCA bifurcate?
-C4
What are the advantages of the neck being separated by fascial planes?
-Allows ease of movements of individual compartments, limits infection
Describe the hyoid bone, state its functions and describe the muscles associated with it.
- Horseshoe shaped bone situated at c3 anchored by strap muscles. Elevates and depresses the larynx in order to aid swallowing
- Elevation by suprahyoid muscles -> digastric, stylohyoid, mylohyoid and geniohyoid
- Depression by infrahyoid muscles -> omohyoid, thyrohyoid, sternohyoid and sternothyroid
Name the layers of the neck
- Skin
- Superficial fascia
- Deep Cervical fascia
- Pretracheal fascia
- Carotid sheaths
- Prevertebral fascia
What lies within the deep fascia of the neck?
- SCM
- Trapezius
- Submandibular gland
- Parotid glands
State the layers of the pretracheal fascia and what is contained within this layer. Why is it beneficial that these structures are separated?
- Muscular and visceral layers
- Trachea, oesophagus, thyroid and infrahyoid muscles
- Allow independant movement during swallowing
What are superficial infections like cellulitis limited to the superficial space?
-Cannot cross deep investing fascia
What is the retropharyngeal space? Why is there a danger space within here?
- Area between pretracheal fascia and paravertebral fascia
- Split into two by alar fascia which joins carotid sheath
- Behind alar fascia lies danger space which connects to diaphragm and therefore would allow infections to spread into the thorax
Why would a parapharyngeal abscess be potentially life threatening?
-Could compress the carotid sheath and lead to IVC thrombosis
State the muscles of facial expression, the nerve which innervate them (and its branches), which pharyngeal arch its related to and state 2 diseases which can affect these muscles
- Frontalis, orbicularis oculi, orblicularis oris, zygomatic mj and mn, buccinator
- CNVII (temporal, zygoatic, buccal, mandibular, cervical)
- PhA 2
- Stroke and Bells palsy
State the muscles of mastication, the nerve which innervate them, which pharyngeal arch its related to
- Massater, Temporalis, med and lateral pterygoids
- CNV(3)
- PhA1
What are the branches of the ECA?
- Superior thyroid
- Ascending pharyngeal
- Lingual
- Facial
- Occipital
- Posterior auricular
- Superior temporal
- Maxillary
Name the branches of trigem and state their functions
- Opthalmic ->sensory to forehead, upper eyelids and dorsum of nose
- Maxillary -> sensory to cheeks, wings of nose, upper lip/teeth,hard palate and sinuses
- Mandibular -> sensory to temple, mandible, lower lip/teeth, motor to MoM
What is the most common cause of non-traumatic facial palsy? How does facial palsy present?
- Inflammation of CNVII near exit through stylomastoid foramen
- Total unilateral facial paralysis including forehead, inability to close eyelid, loss of integrity of oral cavity
Describe the pharyngeal arch system
- 5 external buldges which have a mesenchymal core, ectodermal covering and endodermal lining
- In between each arch exteriorly there is a pharyngeal cleft and interiorly there is a pharyngeal pouch
- Undergo extensive modification to become embryonic head and neck
- Each arch as an associated artery, nerve and cartilage bar
State the borders of the sections of the pharynx
- Naso = Back of nasal cavity to soft palate in line with C1
- Oro = soft palate to epiglottis in line with c2/3
- Laryngo = epiglottis to inferior border of cricoid cartilage in line with c3-c6
Briefly describe the formation of the neural tube. What disease occurs when there is defects in neural tube formation?
- The notochord signals to overlying ectoderm to become neuroectoderm. Neuroectoderm thickens and the edges elevate out of the neural plate and curl towards each other. Fuse to form the neural tube.
- Expanstion of the cranial end produces 3 vesicles named proencephalon, mesencephalon and rhombencephalon which become the forebrain, midbrain and hindbrain respectively.
Where is the facial skeleton derived from?
-Frontonasal prominences and neural crest of PhA1
Describe the derivatives of the 1st pharayngeal arch (artery, nerve, muscles, cartilage, cleft and pouch)
-Artery regresses, nerve is CNV, muscles of mastication, cartilage is meckels and produces the mandible, malleous and incus, cleft forms external auditory meatus and pouch forms middle ear cavity and eustachian tube
Describe the derivatives of the 2nd pharayngeal arch (artery, nerve, muscles, cartilage, cleft and pouch)
- Artery regresses
- CNVII
- Muscles of facial expression
- Reicherts cartilage -> Stapes, styloid process, lessercornu and upper body of hyoid bone
- Cleft -> obliterated by growth of 2PA
- Pouch -> Palatine tonsil
Describe the derivatives of the 3rd pharayngeal arch (artery, nerve, muscles, cartilage, cleft and pouch)
- Artery becomes internal carotid
- Nerve -> glossopharyngeal
- Muscles -> stylopharyngeus
- Cartilage -> greater cornu and lower body of hyoid bone
- Cleft -> Obliterated by growth of 2nd arch
- Pouch -> Thymus and parathyroid gland
Describe the derivatives of the 4th and 6th pharayngeal arch (artery, nerve, muscles, cartilage, cleft and pouch)
- 4th artery = L Arch of aorta, Right Brachiocephalic
- 6th artery -> pulmonary trunk
- Nerve -> Vagus
- Muscles -> Intrinsic muscles of the larynx and epiglottis
- Cartilage -> Thyroid, artynoid and cricoid cartilage
- Cleft -> obliterated by the growth of the 2nd PA
- Pouch -> 4th contributes to parathyroid gland
Describe the function of CNIX
- Innervates stylopharyngeus and provides special sensation to posterior 1/3 tongue
- Provides sensation to external and middle ear,pharynx, tonsils and soft palate
- Carotid bodies and carotid sinus
- Parasymp to parotid (lesser petrosal nerve)
Describe the course of the vertebral arteries
-Arise from the base of the L and R subclavian and ascend through transverse foramina of C1-6 and unite to form basilar artery
Which vessels anastamose to form the circle of willis?
-Basilar and ICA
Which vessels arise from the base of the subclavian?
-Vertebral, thyrocervical trunk and internal thoracic
Give the branches of the thyrocervical trunk
- Ascending and transverse cervical
- Suprascapular
- Inferior thyroid
What is the carotid sinus and carotid body?
- Sinus is a swelling at bifurcation which has baroreceptors for bp
- Body is separate to artery and has peripheral chemoreceptors
What are the boundaries of the carotid triangle in the neck? What is in it? What clinical significance does the catorid triangle bear?
- Sup = posterior digastric
- Lat=anterior SCM
- Med= superior omohyoid
- IJV, CCA bifurcation, Deep LNs and vagus nerve
- Site of central line in IJV, site of carotids for pulse or surgical access, carotid sinus massage
Describe the layers of the scalp? Which layer are the bvs in and why is this significant? Name the vessels of the scalp
- Skin
- Connective tissue dense
- Aponeurosis
- Loose connective tissue
- Periosteum
- The vessels lie in the dense connective tissue which if lacerated holds the vessels open and thus constriction to prevent bleeding is limited
- Supraorbital, supra trochlear, superficial temporal, posterior auricular, occipital
What is the main blood supply to the skull? What is a common cause of rupture? Why is this the case? What type of haemorrhage is produced?
- MMA
- Blow to the pterion
- The point of fusion of 4 bones of the skull making it a weak area
- Extradural
What are dural venous sinuses?
- Endothelial lined spaces between the periosteal and meningeal layers of dura mater
- They receive blood from large veins of the brain and drain into IJV
What structures run through cavernous sinus?
- ICA
- CN III, IV, V1,V2 and VI
Why is it clinically significant that face veins are valveless?
-Allows infection to track back into the skull/brain
Where are lymphatics not present?
-cornea/lens, inner ear, bone marrow
Describe how lymph is formed. What is its purpose?
- Balance between hydrostatic and oncotic pressure -> net movement = tissue fluid
- Some small proteins in tissue fluid and cannot re-enter circ -> enter porous lymphatic capillaries and water follows -> now termed lymph
- Allows tissue fluid ot rejoin systemic circ
How can lymphatic channels contribute to disease?
-Can allow spread of malignancy and disease
State the order of lymphatic flow from tissue fluid to rejoin circulation. How is the flow of lymph maintained?
- Tissue fluid -> afferent lymph vessel -> LN -> efferent lymph vessel -> lymphatic trunk -> lymphatic duct -> subclavian artery
- Valves ensure flow is in one direction and passive constriction by muscles and arteries make lymph flow
What is lymphoedema? Give some causes
- Fluid retention and tissue swelling due to a comprimised lymphatic system.
- Removal of LNs, infection, chemo, immobility
What separates superficial and deep cervical LNs? Name the deep LNs, which are of particular importance?
- deep cervical fascia
- Jugulo-digastric (tonsillitis), jugulo-omohyoid, supraclavicular (left is significance of gastric carcinoma)
Describe the structure of a lymph node, state its function. Give 2 differentials of an enlarged lymph node and how you would differ between them
- Connective tissue structure which has a tough fibrous capsule and reticular inside. Several afferent vessels enter and one leaves -> Made of several follicles surrounded by a cortex with a germinal centre
- immune surveillance with macrophages and lymphocytes, filter
- Infection -> tender, smooth, firm and mobile
- Malignancy -> non-tender, hard, craggy and matted
What are neural crest cells?
-Specialised population of cells that originate laterally in the neuroectoderm, become displaced after neural tube fusion and migrate throughout the body
State where the skeletal structures of the face are deived from
- The frontonasal prominence develops into the forehead, nose and filtrum
- The maxillary portion of PhA1 develops into cheeks, lateral upper jaw and lateral upper lip
- The mandibular portion of PhA1 develops into mandible
How are the oral and anal apertures created?
-No mesoderm in these areas means the membranes rupture as no blood supply develops there
Describe the development of the nose
- Thickening of ectoderm on either side of FNP produces 2 nasal placodes
- Nasal placodes sink into nasal pits
- Lateral apsects of the pits raise out of the plane and form medial and lateral nasal prominences
- Expansion of the maxillary prominence drives the nasal prominences close together until the medial prominences fuse
- Also fuses with maxillary prominence forming intermaxillary segment which contains philtrum, 4 inscisors and primary palate
- Nasal septum grows down and fuses with palatal shelves
Describe the formation of the palate
- Primary palate forms from FNP
- Maxillary prominence of PhA1 develops 2 palatal shelves which grown vertically into oral cavity at either side of tongue
- Mandible grows sufficiently large and allows tongue to drop out of the way and the palatal shelves fuse forming the secondary palate
- Primary palate and secondary palate fuse to give definitive palate
How can a cleft lip or palate occur?
- Failed fusion of the primary and secondary palate
- Failed fusion of the palatal shelves of secondary palate
- failed fusion of the medial nasal prominences with maxillary prominence (cleft lip)
Describe the development of the eye and its anatomical positioning
- Outpocketings of forebrain become the optic vesicle and grow outwards to make contact with overlaying ectodermal covering
- This contact induces the formation of the lens placode
- Optic vesicle begins to invaginate bringing the lens placode with it
- The two surfaces of the optic vesicle meet and form the optic cup and then the retina
- The lens placode develops into the lens vesicle and then the lens
- Primordia begin on side of head and as facial prominences grow they are pushed into anatomical position
Describe the development of the external ear
- The external auditory meatus comes from the 1st Ph cleft
- The auricles develop from the 1st and 2nd arches which surround the EAM
- Begin development in the neck region and ascend as the mandible grows
What is fetal alcohol syndrome
- Neural crest migration and brain development is extremely sensitive to alcohol
- Produces deformities including underdeveloped jaw, flattened face, smooth philtrum, small palpebral fissures and possible learning or developmental defects
Describe a typical cervical vetebrae
How is C7 different?
Describe atlas and axis and state which movements they make possible
- Bifid spinous process with transverse foramina and large triangle vertebral foramen
- Spinous process not bifid
- Atlas has no vertebral body or spinous process -> yes movement
- Axis has odontoid process to support atlas -> no movement
In an AP plane of the cervical spine from which vertebrae can you see?
What is a burst fracture?
What is a hangmans fracture?
- C3
- Jeffersons fracture -> 2-4 fractures in atlas caused by the occipital condyles being driven into c1 (fall on head)
- Hyperextension of the head on the neck causes a bilateral fracture of C2 and compresses the brainstem
Name the sutures of the skull and the points of joins. Why are they serrated?
What is the mental symphysis?
- Coronal, saggital and lamboid, bregma and lambda
- Allow interlocking of the cranium
- Point of mandible fusion
How is the skull specialised for its function?
- Dense strong flat bones for protection
- Trilaminar structure with the middle bony layer being spongy bone to make it light weight
Which cranial nerves relate to which cranial fossas?
- 1,2 in anterior fossa
- 3-6 in middle fossa
- 7-12 in posterior fossa
What is a consequence of fracture to the ethmoid bone and why?
- Anosia or CSF rhinorrhoea
- Anosia because olfactory fibres run through ethmoid to supply olfactory mucosa
- CSF rhinorrhoea because csf can now leak out if there is also damage to the meninges
How does the neonatal skull differ from adult skull?
- Cranial sutures wide in the neonate spanned by thick connective tissue called fontanelles to allow movement of bones during childbirth
- Temporarily interlock during birthing to protect the brain