Week 2- osteology, radiology and common disorders and branchial arches Flashcards Preview

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Flashcards in Week 2- osteology, radiology and common disorders and branchial arches Deck (140):

What is the difference between the neurocranium and the viscerocranium. What are the subdivisions of the neurocranium?

  • The neurocranium is made up of 8 bones and houses the brain. It is subdivided into:
    • Calvaria 
    • Base of the skull 
  • The viscerocranium is made up of 14 bones forming the facial skeleton 


Which bones make up the viscerocranium?

  • Nasal bones (L+R) 
  • Maxilla (L+R)
  • Lacrimal bones (L+R) 
  • Zygomatic bones (L+R) 
  • Inferior nasal choncha (L+R)
    • Increase surface area of the nose for warming and humidification 
  • Palatine bones (L+R) 
  • Mandible 
  • Vomer 
    • Makes up part of the nasal septum 


Label the viscerocranium 


Which bones make up the neurocranium?

  • Parietal bones (L+R)
  • Temporal bones (L+R) 
  • Occipital bone 
  • Frontal bone 
  • Sphenoid bone 
  • Ethmid bone 


Label the bones of the neurocranium 


Describe the two types of joints found in the skull 

  • Immobile joints:
    • Most of the skull joints 
    • Joined by a strong fibrous tissue aka sutures
  • Mobile joints:
    • Only one freely moveable joint in the skull: temporomandibular joint (TMJ) 


Why are most of the joints in the skull immoveable?

  • To increase protection of the brain as it forms a firm cage 


Name the different sutures between 2 bones in the skull and name which bones they separate

  • Coronal:
    • Separates parietal and frontal bones 
  • Squamous suture
    • Separates parietal and temporal 
  • Lambid
    • Separates parietal and occipital
  • Saggital suture
    • Separates the two parietal bones 


name the 3 sustures in the skull which mark the point between 3/4 bones and name which bones they are

  • Bregma:
    • Frontal and two parietal bones 
  • Pterion:
    • Sphenoid, temporal,  parietal and frontal
  • Lambda 
    • Occipital and 2 parietal bones 


What runs under the pterion? 

  • The anterior branch of the middle meningeal artey 
  • It is a common site of bleeding in extradural haemorrhage


Label the following sutures 

  1. Coronal suture 
  2. Lamboid 
  3. Squamous 
  4. Pterion 


Label the following sutures

  1. Coronal 
  2. Bregma 
  3. Saggital 
  4. Lambdoid 
  5. Lambda 


What are fontanelles? Where are they found?

  • Membranous areas of un-fused skull which will close in the first 2 years of life
  • Anterior fontanelle will fuse to form the bregma 
  • The posterior fontanelle will fuse to form the lambda 


What is the purpose of fontanelles?

  • Allow flexibility of the skull which:
    • Eases passage through the birth canal 
    • Allows for brain growth 


what is indicated if fontanelles are:

  • Sunken 
  • Bulging 
  • Enlarged (this is when the fontanelle becomes more than a spot and can spread round) 

  • Sunken 
    • Sign of dehydration 
  • Bulging
    • Sign of raised intracranial pressure 
  • Enlarged 
    • This can cause compression of the brain leading to brain damage 


What do the following colours indicate:

  • Yellow 
  • Green 
  • Orange 
  • Dark purple 
  • Light purple 
  • Red 

  • Yellow 
    • Outer table 
  • Green 
    • Inner table 
  • Orange 
    • Coronal suture 
  • Dark purple:
    • Cranial cavity 
  • Light purple:
    • Orbit
      • The eye and some muscles lie here
  • Red 
    • Sella turcica
      • pituitary gland sits here 


What is between the inner and outer table?

  • Diploe (spongy cancellous bone) 


Label it yeh 

  1. Frontal sinus 
  2. Sphenoid sinus 
  3. Ethmoidal air cells 
  4. Maxillary sinus 
  5. Hard palate 
  6. Mandible 
  7. Hyoid
  8. Axis with dens (C2)
  9. Atlas (C1) 


Which bones make up the hard palate?

Maxillary and palatine 


What is shown by the following colours?

  • Yellow 
  • Orange 
  • Green 
  • Blue 
  • Red 
  • Purple 

  • Yellow 
    • Frontal sinus 
  • Orange 
    • Mastoid air cells 
  • Green 
    • Ethmoid sinus 
  • Blue 
    • Maxillary sinus 
  • Red
    • Vomer 
  • Purple 
    • Cranial cavity 


If you suspect a skull fracture which imaging method should you use? 

  • CT 
  • Often the extent of fractures cannot be seen on x-rays 
  • MRIs show brain damage really well but aren't so good for fractures
  • We can do MRA after a CT if we suspect damage to a vessel 


What is MRA?

  • Magnetic resonance angiogram 


What is the lucid interval?

  • Sometimes after a head injury there is a lucid interval where the person feels fine
  • They then deteriorate rapidly so we cannot assume that it is a sign that they are okay 


How do extradural (epidural) and subdural haemorrhages appear on CT?

  • blood appears as a white area 
  • Extradural is like a lemon in shape 
  • Subdural is like a banana in shape 


Describe what happens in an extradural haemorrhage

  • Blood collects between the skull periosteum and the outermost meningeal layer (dura mater)
  • Associated with trauma and skull fractures 
  • Blood usually comes from an artery 


Describe what happens in a subdural haematoma 

  • Blood collects between the dura and arachnoid mater 
  • Bleeding is usually from veins so lower pressure 


What are the examination signs associated with a basilar skull fracture?

  • Rhinorrhoea- clear fluid (CSF) running from the nose
  • Haemotympanum- blood in the middle ear 
  • Periorbital ecchymoses- dark circles around the eyes 
  • Battle sign- mastoid bruising (behind the ear) 


How common are basilar skull fractures?

  • <5% of skull fractures


What complications can arise as a result of a basilar skull fracture?

  • Meningeal tears can cause:
    • Leakage of CSF
    • Bleeding in soft tissues/sinuses/tympanic cavity 
  • Cranial nerve palsies 
  • Risk of meningitis and brain abscesses 
  • There is a high risk of neurosurgical intervention 


Which areas are fractured when we get the following signs?

  • Rhinorrhoea 
  • Haemotympanum
  • Blood in the cranial cavity

  • Rhinorrhoea:
    • Cribriform plate 
  • Haemotympanum 
    • Between the occipital bone and the petrous temporal bone 
  • Blood in the cranial cavity 
    • Between temporal and sphenoid bone


Which cranial nerves run through the internal auditory meatus?

  • Facial nerve 
  • Cochlear nerve 
  • Inferior and superior vestibulocochlear nerve 


How does CN VII nerve palsy present?

  • This is facial nerve palsy and affects muscles of facial expression. It presents as:
    • Smoothing out of the forehead
    • Eyebrow droop 
    • Drooping of the corner of the mouth 


If you suspect a C-spine injury what should you do?

  • Immobilise the patient to avoid further damage to the spinal cord which could cause paralysis 
  • Must determine the mechanism of injury 
  • Must check for symptoms e.g. neck pain, abnormal neurology such as pins and needles/loss of function 


How can we clear the C-spine? (this means that you have made sure it is not injured and so does not need to be immobilised) 

  • We can clear it clinically e.g. if no symptoms present 
  • Or need imaging to rule out C-spine fracture:
    • CT in adults 
    • X-ray/MRI in paeds 
      • avoids high dose of radiation which can affect developing areas e.g. thymus 


What are the main types of pathology involving the C-spine?

  • jefferson's fracture 
  • Hangman's fracture 
  • Vertebral crush fractures 
  • Degenerative disease 
    • Cervical spondylotic radiculopathy 
    • Cervical spondylotic myelopathy


What is a Jefferson's fracture? What is the common mechanism? What is the difference between a stable and unstable Jefferson's fracture?

  • It is a 'burst facture' of C1 in which the size of the vertebral foramen is increased
  • It is a combination of anterior and posterior arch fractures 
  • Mechanism:
    • Often axial compression 
    • e.g. diving head first into shallow water 
  • Stable vs. unstable 
    • If transverse ligament is ruptured it is unstable 
    • Unstable requires surgery 


What is a hangman's fracture? What is the mechanism behind it? What is the difference between a stable and unstable Hangman's fracture?

  • Bilateral fracture of the posterior arch of C2 and disruption of the C2-3 junction 
    • If it extends to the transverse foramina it can affect arteries running through them
  • Mechanism= hyperflexion of the neck 
  • All of them are unstable- there is a high risk of C2 displacement and spinal cord damage 


Which vessels run through the transverse foramina in the cervical spine vertebrae?

  • Vertebral artery and vein
  • They go through all of them except C7 which has only the vertebral vein


Describe vertebral crush fractures. What is the mechanism? What are they associated with? What is seen on x-ray in a cervical wedge fracture?

  • Fractures of the vertebral bodies 
  • Mechanisms are various e.g. hyperflexion 
  • Associated with weak bones and spinal degenerative disease e.g. osteoporosis 
  • Cervical wedge fracture:
    • Loss of height of vertebral body seen on x-ray 
    • May be stable if only one vertebra is involved


What can osteoarthritis of the C-spine lead to? Who is it most likely to affect?

  • Can lead to cervical spondylosis 
  • Affects the older population (very common) 


What are the features of degenerative disease (osteoarthritis) of the C-spine?

  • Osteophytes (bony spurs)
  • Facet joint hypertrophy
  • Disc herniation 
  • Disc space narrowing 
  • Sclerosis of end plates 



What is cervial spondylotic radiculopathy? What does it cause?

  • Nerve root impingement 
  • Causes dermatomal pain +/- mild weakness and sensory loss 


What is cervical spondylotic myelopathy? What does it cause?

  • Spinal cord compression 
  • Causes loss of function, often loss of fine motor skills in the upper limbs (doesn't really affect lower limbs) 


What are the major differences between the foetal/infant and adult skull?

  • Fontanelles present in foetus/infant but not adults 
  • In foetus/infant neurocranium is bigger than the viscerocranium; in adults there are roughly the same size
  • In foetus/infant there is no mastoid or styloid process 
  • In foetus/infant there are smaller paransal sinuses than in adults 
  • In the foetal skull there are no erupted teeth


What do the fontanelles fuse by? When do they fuse?

  • Fuse by intramembranous ossification 
  • Posterior fuses by 2-3 months
  • Anterior fuses by 18-24 months 


What are the two major features of the ethmoid bone?

  • Cribriform plate 
    • Cribriform foramina 
  • Crista Galli 


There are lots of little holes (cribriform foramina) in the cribriform plate of the ethmoid bone. What are these for?

  • These allow the passage of the olfactory nerve 


What is the crista galli?

  • It is a protrusion from the cribriform plate 
  • It is the anterior attachment for the dura that runs down the midline separating the 2 halves of the brain 


Describe the relationship between the crista galli (part of ethmoid bone) and CSF rhionorrhoea

  • A blow to the face e.g. nose can transmit force through the crista galli and dura and so blood can pass through holes in the cribriform plate into the nasal cavity 
  • This causes CSF rhinorrhoea (sign of damage to the anterior cranial fossa 


What are the foramina of the sphenoid bone?

  • Optic canal 
  • Superior orbital fissure
    • (this is the big slit at the back of the eye) 
  • Foramen rotundum 
  • Foramen ovale 
  • Foramen spinosum 


What passes through the optic canal?

  • The optic nerve passes through to the orbital cavity into the back of the eye 


What does the supeiror orbital fissure transmit?

  • A number of strucutres into the orbit 
  • Number of cranial nerves go through to supply muscles that move the eye and blood vessels that supply the eye 


What does the foramen rotundum pass into? What passes through foramen rotundum?

  • Passes into a tiny space between the sphenoid and maxilla called the pterygopalatine fossa
  • A number of nerves and vessels pass through before supplying the rest of the face e.g. maxillary branch of trigeminal nerve 


What does the foramen ovale pass into? What passes through it?

  • Passes into a space below the temporal bone, medial to the mandilble known as the infratemporal fossa
  • Within the fossa we have some muscles of mastication (pterygoid muscles) and the mandibular branch of the trigeminal nerve 


What passes through the foramen spinosum?

  • The middle meningeal artery
  • This has anterior and posterior branches and these supply the dura 


Describe the position of the greater and lesser wings of the sphenoid bone

  • Lesser wing 
    • This is a ridge between the frontal and sphenoid bone 
  • Greater wing 
    • This is a flatter surface and is kind of like a dip below the lesser wing 


The sella turcica is a dip in the body of the sphenoid with a ridge at the front and the back. On either sides of these ridges are protuberances; what are these called?

  • The posterior ridge is also called the dorsum sellae 
    • Has posterior clinoid processes (protuberances)
  • The protuberances on the anterior ridge are the anterior clinoid processes. 
    • They are more prominent than the posterior ones 


What is the deepest part of the sella turcica called? What sits in this space? 

  • Deepest part is called the hypoglossal fossa 
  • The pituitary gland sits in this 


What are the foramen of the temporal bone? 

  • Foramen lacerum 
  • Carotid canal 
  • Internal auditory meatus 


What runs through the foramen lacerum?

  • Nothing; it is covered in cartilage
  • It is basically a gap between the petrous part of the temporal bon and the sphenoid 


Where does the carotid canal run?

  • It starts off at like the oblique bit of foramen lacerum 
  • It arises at the base of the skull and runs through the petrous part of the temporal bone 


Where is the internal auditory meatus? What does it transmit?

  • It is on the posterior aspect of the ridge of the petrous temporal bone 
  • Carries nerves which carry sensation of balance and hearing to the brain stem- vestibular cochlear nerve 
  • Also transmits facial nerve which goes through petrous bone and exits  the base of the skull though the stylomastoid foramen (between mastoid and styloid process) then comes to run into substance of the parotid gland giving 5 terminal branches 


What does the frontal bone make up? 

  • The forehead and then it kind of folds under to form the orbital plates (roof of the orbits) 


If there is damage to the orbital plates, what can occur?

  • Blood from the intracranial passage can pass into the tissue around the orbits; this can lead to periorbital ecchymosis (this is a sign of a fracture involving the ethmoid/orbital plate) 


What are the main features of the occipital bone? 

  • Clivus 
  • Internal occipital protuberance 
  • Foramen magnum 
  • Hypoglossal canal 
  • Jugular foramen 


What is the clivus?

  • Part of the occipital bone behind the dorsum sellae (posterior ridge of body of sphenoid)
  • It is a shallow depression which slopes obliquely downwards 


What does the internal occipital protuberance mark?

  • The point of intersection of the 4 divisions of the cruciate eminence


What does the foramen magnum transmit?

The spinal cord


Where does the hypoglossal canal run? What does it transmit?

  • Runs through the occiptal bone 
  • Transmits the hypoglossal nerve allowing it to run down and supply the muscles of the tongue 


What does the jugular foramen transmit? Where does it exit?

  • Transmits the internal jugular vein (continuation of the sigmoid sinus which drains the brain (you can see a grooving of the base of the skull where the sigmoid sinus runs))
  • Also transmits the glosspharyngeal, vagus and accessory nerve 
  • Exits very close to the exit of the carotid canal so the artery and vein run down the neck close together in the carotid sheath 


Which bone of the base of the skull does each of the colours represent?


What are these 3 general areas of the base of the skull called?


label the cribriform plate and the and the crista galli

  • They are part of the ethmoid bone 


  • Label the following features of the sphenoid bone:
    • Optic canal 
    • Superior orbital fissure 
    • Foramen rotundum 
    • Foramen Ovale 
    • Foramen spinosum 
    • Lesser wing of sphenoid 
    • Greater wing of sphenoid 
    • Sella turcica 
    • Body of sphenoid 
  • And these features of the temporal bone:
    • Foramen lacerum 
    • Carotid canal 


Label the following parts of the temporal bone:

  • Internal auditory meatus 

And the following parts of the occipital bone:

  • Clivus 
  • Internal occiptal protuberance 
  • Foramen magnum 
  • Hypoglossal canal 
  • Jugular foramen 


Label the following parts of the temporal bone 

  • Articular fossa for mandible 
  • External auditory meatus
  • Styloid process 
  • Zygomatic process of temporal bone
  • Mastoid process
  • Squamous part of temporal bone 
  • Petrous part of temporal bone 


Where is the temporal fossa?

  • It is the site of origin for temporalis muscle
  • The temporal, sphenoid, parietal and frontal bone contribute to its wall 
  • It is bound by the superior temporal line (above) and zygomatic arch (below) 


Label the following:

  • External occipital protuberance  
  • Zygomatic arch of zygoma 
  • Zygomatic process of maxilla 
  • Mandible:
    • head of mandible 
    • Neck of mandible 
    • Body of mandible 
    • Coronoid process of mandible
    • Ramus 
    • Angle of mandible 


Where is the infratemporal fossa? What communicates with this space? Which muscles are found here?

  • Behind and medial to the zygomatic arch
  • Inferior orbital fissure and pterygopalatine fossa communicate with this space 
  • Medial and lateral pterygoid muscles found here 


Label the following parts of the mandible:

  • Mandibular foramen 
  • Mental foramen 
  • Mental protuberance 


What do the mandibular foramen and the mental foramen transmit?

  • Mandibular foramen 
    • Transmits divisions of the mandibular nerve and blood vessels 
  • Mental foramen 
    • Transmits terminal branches of the inferior alveolar nerve and vessels 


Label the following:

  • Superior orbital fissure
  • Inferior orbital fissure
  • Frontal process of maxilla 
  • Middle nasal concha 
  • Inferior nasal concha
  • Alveolar process of maxilla 
  • Infraorbital foramina 
  • Vomer
  • Nasal bone 
  • Lacrimal bone 


What does the alveolar process of the maxilla contain?

  • The tooth sockets 


What does the infraorbital foramen transmit?

  • The infraorbital artery and vein and the infraorbital nerve (branch of maxillary) 


Label the:

  • Perpendicular plate of the ethmoid bone 
  • Following parts of the frontal bone:
    • Orbital plate 
    • Supraorbital ridge 
    • Supraorbital notch (foramina) 


What does the supraorbital notch (foramina) transmit?

  • The supraorbital nerve passes through then splits into superficial and deep branches to provide sensory innervation to the forehead
  • It is a branch of the ophthlamic division of the trigeminal nerve 


Label the following:

  • Sphenoid bone:
    • Pterygoid process
  • Temporal bone:
    • Styloid process
    • Mastoid process
    • Stylomastoid foramen 
  • Maxilla:
    • Palatine process (hard palate)
  • Occipital:
    • Articular condyles for atlas 



Where is pterygopalatine/pterygomaxillary fossa? What opens into it?

  • It is between the paltine process of maxilla (hard palate) and the pterygoid plate of sphenoid 
  • The foramen rotundum opens into it 


What is the skull a collective term for?

  • The cranium:
    • Neurocranium 
    • Viscerocranium 
    • Cranial cavity= space in cranium which holds the brain 
  • The mandible 


The calvaria (skull/cranial cap) is made up of an inner table and outer table with diploe in between. Describe the inner table. Why do we have this tri-laminar arrangement?

  • Innermost layer of compact bone is brittle
  • Tri-laminar arrangement adds strength without adding considerable weight 
    • Severe blows to the skull may still result in local depression and splintering of bone or a series of linear fractures radiating away from the initial point of injury 


Why are sutures hard to dislocate? What happens to them as we age? 

  • They are interlocking 
  • As we age they ossify 


why is the cranial floor vulnerable to fracture if significant force is transmitted through the skull base? 

  • Due to the large number of foramina 


What are the most common causes of injury to the facial skeleton? What are the most common facial fractures? Which bones require significant force to fracture?

  • Most common causes: road traffic collisions, fights and falls 
  • Most common fractures: 
    • Nasal bones (due to prominence of nose)
    • Zygomatic bones 
    • Mandible 
  • Significant force:
    • Maxillary 
    • Frontal 


what does a hard blow to the lower jaw often result in?

  • Fracture of the neck of the mandible and its body 
  • May be associated with dislocation of the TMJ 


The bony skeleton of the neck is made up of 7 cervical vertebrae with intevertebral discs between them. What is the exception? 

  • No disc between C1/C2 as C1 has no vertebral body 


The vertbral foramina in cervical vertebrae are bigger than other vertebrae, why is this? Why do they get smaller as you move caudally?  

  • Bigger to accomodate the thicker spinal cord 
  • Gets smaller as nerves leave the spinal cord to innervate tissues


C1 and C2 are atypical cervical vertebrae. Describe their features. 

  • C1 (atlas)
    • Ring shaped
    • Supports skull at the atlanto-occipital joint 
    • Inferiorly articulates with the axis 
  • C2 (axis)
    • Strongest cervical vertebrae as C1 (carrying the skull) rotates on it
    • The dens is held in place by a strong trnasverse ligament of the atlas.
      • This prevents horizontal displacement of the atlas and stabilises the atlanto-axial joint 


Why are cervical vertebrae more likely to dislocate than others? Why might slight dislocation not damage the spinal cord? 

  • The articular surface between cervical vertebrae is more horizontal than others so less force is needed for them to 'slip off'/dislocate 
  • Slight dislocation may not damage the spinal cord due to the large vertebral canal in the cervical region 


Where are the most common sites for cervical spine injury? Where do the most severe injuries often occur? 

  • Most common sites 
    • C1/C2 
    • C6 
    • C7 
  • Most severe injuries:
    • In upper part of spine (C1-C4), where damage can lead to quadriplegia (paralysis of all 4 limbs) and cessation of respiratory movements 


what can hyperflexion injuries of the neck e.g. head on car collisions lead to? Which part of the cervical spine do they involve?

  • Involve the lower part of the cervical spine 
  • Can lead to:
    • Crush fractures of vertebral body 
    • Rupture of supraspinous ligament (makes spine unstable)
    • Rupture of lower intervertebral discs (e.g. C5/C5 and C6/C7) can cause compression of spinal nerve roots C6 and C7 


what can hyperextension injuries of the neck e.g. read-end vehicle collisions lead to? Which part of the cervical  spine is often involved? What can minimise range of hyperextension possible?

  • Commonly effect upper cervical spine
  • Can lead to:
    • Vertebral fracture
    • Disc prolapse
    • Cervical spinous process or dens process fracture
    • Tearing of anteior longitudinal ligament 
    • Kinking of posterior longitudinal ligament 
  • Car seat headrests can limit hyperextension 


What emerges through intevertebral foramina? What can cause narrowing of the intervertebral foramina? what can this cause?

  • Spinal nerves emerge through them
  • Causes of narrowing:
    • Osteoarthritis of the facet joints of vertebral arches
    • Age related changes cause bulging of intervertebral discs
  • Narrowing causes compression of spinal nerve leaving at that level:
    • Pain along dermatome 
    • Muscle weakness in muscles in affected myotome 


Label the following features of the C1 vertebra:

  • Posterior arch 
  • Anterior arch 
  • Lateral mass
  • Posterior tubercle 
  • Anterior tubercle 


Label the following features of a typical cervical vertebra:

  • Articular facet
  • Posterior tubercle
  • Anterior tubercle 
  • Body
  • Pedicle
  • Transverse foramina
  • Vertebral foramen (canal)
  • Lamina
  • Bifid spinous process 


What is the boundary between the middle and posterior cranial fossa?

The superior ridge of the petrous part of the temporal bone 


The pharyngeal arches are a system of mesenchymal proliferations in the neck region of the embryo. How may of them are there?

  • They are numbered 1,2,3,4,6 (the 5th does not form in humans)
  • The first is v large with 2 bumps in it; they get smaller as you go through the numbers 


What is located above the pharyngeal arches? What else is in close proximity with the arches?

  • Above the pharyngeal arches is the FNP (frontonasal prominence), under the ectoderm here is the brain and so this is why it is prominent and enlarged 
  • The pharyngeal arches are in close proximity to the developing heart, especially the outflow tract. 
  • Also in close proximity to the developing brain 


What is located cranial to the area where the brain is developing? 

  • A lens sensory placode that will become the eyes
  • A nasal sensory placode which will become the nose 


On the external part of the pharyngeal arches are called arches; the internal bit are called pouch and there is a core between them. Which tissue is each of these parts developed from? 

  • The arch 
    • Ectoderm 
  • The pouch 
    • Endoderm 
  • The core
    • Mesoderm 
    • This very quickly starts to differentiate to mesenchymal tissue which is basically primitive connective tissue 


What migrates into the mesoderm core of the pharyngeal arches?

  • Neural crest cells migrate in from elsewhere 
  • They are very important for development of the head and neck region 


What are the dips inwards between arches and pouches called?



What is associated with each pharyngeal arch?

  • Artery 
  • Nerve 
  • Cartilage bar 


Describe the development of the neural tube

  • The notochord signals to overlying ectoderm causing it to thicken
  • The edges of the slipper shaped neural plate elevate out of the plane of the disc and curl towards each other, creating the neural tube  


The anterior end of the neural tube begins to form the brian. There are 3 vesicle stages, what are these?

  • Prosencephalon = forebrain 
  • Mesencephalon= midbrain
  • Rhombencephalon= hindbrain 


What does the caudal end of the neural tube give us?

The spinal cord 


What are the cranial nerves of the pharyngeal arches? 

  • All have mixed sensory and motor function 
  • They supply the derivatives of the pharygeal arches

N.B. CNXI and CNXII also have a relationship with the pharyngeal arch system 


What is the nerve of the first pharyngeal arch? What are its main functions?

  • CNV - trigeminal 
  • Principal sensory nerve of the face and lining of the mouth and nose 
  • Motor innervation to the muscles of mastication and muscles derived from the mandibular process (these are derived from the first arch) 


What is the nerve of the 2nd pharyngeal arch? Where does it pass? What are its main functions?

  • CNVII- facial nerve
  • Passes through the stylomastoid foramen and parotid gland 
  • Mostly motor: muscles of facial expression and muscles derived from the 2nd arch 
  • Small sensory: taste buds in the anterior 2/3rds of the tongue 


What is the nerve of the 3rd arch? What is its main function? 

  • CNIX- glossopharyngeal nerve 
  • Innervates stylopharyngeus muscle and provides general and specific sensory innervation to posterior 1/3 of the tongue 


What is the nerve of the 4th and 6th arches? What nerve is the 4th arch branch? What about the 6th arch branch? What do these innervate?

  • The vagus nerve
  • 4th arch branch is the superior laryngeal nerve 
    • Cricothyroid
    • Constrictors of the pharynx
  • 6th arch branch is the recurrent laryngeal nerve
    • intrinsic muscles of the larynx 


Different parts of the face are derived from different things, explaining their different innervation. What are the following derived from?

  • facial skeleton 
  • Muscles of mastication 
  • Muscles of facial expression 

  • Facial skeleton 
    • Frontonasal prominence and 1st pharyngeal arch 
  • Muscles of mastication 
    • Pharyngeal arch 1 derivatives
  • Muscles of facial expression 
    • Pharyngeal arch 2 derivatives 


What are the derivatives of the 3rd-6th pharyngeal arches?

  • 3rd arch
    • stylopharyngeus 
  • 4th arch 
    • Cricothyroid 
    • Levator palantini
    • Constrictors of the pharynx
  • 6th arch 
    • Intrinsic muscles of the pharynx 

N.B. As we move through the arches they get smaller and so does the list of derivatives 


The development of the cartilagenous bar by each arch occurs under the influence of the neural crest. Generally, what does it go into the formation of?

  • The skeletal elements of the head and neck 


What does the cartilage of the 1st pharyngeal arch develop to give?

  • This is Meckel's cartilage
  • Divides into maxillary and mandibular prominences to give upper and lower jaw
  • Mandibular prominence develops prominent Meckel's cartilage and this remodels to give malleus and incus (bones of the middle ear). 
    • This cartilage also gives template for mandible development which forms by intramembranous ossification 


What does the cartilage of the 2nd pharyngeal arch develop to give?

  • This is Reichert's cartilage 
  • It contributes to middle ear development: Stapes
  • Also forms:
    • Styloid process
    • Hyoid bone 
      • lesser horn and upper body (upper half of bone basically)


What do the cartilages of the 3rd and 4th pharyngeal arch develop to give?

  • 3rd 
    • Remainder of hyoid bone 
  • 4th 
    • Thyroid cartilage 
    • Arytenoid cartilage 
    • Cricoid cartilage 


Where does the aortic sac lie? 

  • In the floor of the pharynx 


There is an aortic arch for each of the pharyngeal arches. When remodelling occurs, what happens to each of these arches? What also happens during this remodelling? 

  • 1st and 2nd arches disappear 
  • 3rd arch artery 
    • Internal carotid 
  • 4th arch artery 
    • arch of aorta (L)
    • Brachiocephalic (R) 
  • 6th arch artery 
    • Pulmonary arch 

During this remodelling the left recurrent laryngel nerve loops around the arch of aorta 


What do the pharyngeal pouches generally develop to give?

Glandular derivatives 


  • What do the following give rise to?
    • The cleft between the 1st and 2nd pharyngeal arch 
    • The cleft between the 1st and 2nd pharyngeal pouches 
    • The 2nd pouch 
    • The 3rd and 4th pouches 

  • Cleft between 1st + 2nd arches
    • Gives external auditory meatus 
  • Cleft between 1st + 2nd pouches
    • Gives auditory tube 
  • 2nd pouch 
    • undegoes epithelial proliferation, followed by colonisation by lymphoid precursors
  • 3rd and 4th pouches
    • Divide into dorsal and ventral components
    • 3rd and 4th dorsal: parathyroid
    • 3rd ventral: thymus 


In regard to the middle ear what are the following derivatives of?

  • Ossicles 
  • Tympanic cavity and auditory tube 

  • Ossicles
    • cartilage bar derivatives
  • Tympanic cavity and auditory tube
    • 1st pharyngeal pouch derivatives  


The 1st of the clefts if all that remains. What happens to the rest of the clefts?

  • The 2nd arch gorws down to cover the others, obliterating them 
  • There can be remnants:
    • If cervical sinus is not obliterated, cysts or fistulae can occur 
    • These can occur anywhere along the anterior border of sternocleidomastoid 


Give an overview of what the 1st pharyngeal arch develops to give

  • nerve
    • CNV- trigeminal 
  • Muscles 
    • Muscles of mastication, digastric, mylohyoid 
  • Skeletal 
    • Meckel's cartilage:
      • Mandible 
      • Malleus
      • Incus
  • Sensory:
    • Skin of face and lining of mouth and nose and part of tongue 


Give an overview of what the 2nd pahryngeal arch develops to give?

  • Nerve 
    • CN VII - facial 
  • Muscles 
    • Muscles of facial expression 
  • Skeletal 
    • Reichert's cartilage:
      • Stapes
      • Upper body and lesser horn of hyoid 
      • Styloid process
      • Stylohyoid ligament 
  • Sensory:
    • Part of the tongue 


Give an overview of what the 3rd pharyngeal arch develops to give?

  • Nerve 
    • CN IX- glossopharyngeal 
  • Muscles 
    • Stylopharyngeus 
  • Skeletal 
    • Lower body of hyoid and greater horn 
  • Sensory
    • Part of the tongue 



Give an overview of what the 4th pharyngeal arch develops to give

  • nerve 
    • CNX- vagus (superior laryngeal branch)
  • Muscles 
    • Pharyngeal muscles 
    • Cricothyroid 
  • Skeletal 
    • Thyroid cartilage 
    • Cricoid cartilage 


Give and overview of what the 6th pharyngeal arch develops to give

  • Nerve:
    • CNX- vagus (recurrent laryngeal branch)
  • Muscles:
    • Intrinsic muscles of the larynx
  • Skeletal 
    • Arytenoid cartilage 


when do the pharyngeal arches develop and where?

  • About 4 weeks 
  • In the lateral walls of the embryonic pharynx towards cranial end of the neural tube 


What are the pharyngeal arches, grooves (clefts) and pouches collectively known as?

Pharyngeal apparatus