1019DOH - Applied Oral Biology (HEAD AND NECK ANATOMY)

only the true goats will read this ;) part 2 of the oral biology flashcard series! please study these unshuffled:) happy studying

the CNS (central nervous system) begins developing when the embryo is __1__ WIU and at the ___2__ end of the embryo

• note: central nervous system will be referred to as CNS from this point onwards

1. 4

2. head

the CNS development in the embryo begins as a thickening in the ectoderm in the…

• neural plate

flip card over for visualiser of CNS embryonic development

at 4 WIU, how long is the embryo?

• 3-4mm long

describe the embryonic development of the CNS neural tube

• the edges of the neural plate begin to thicken, producing raised margins to the structure. between these margins lies the neural groove

• neural folds continue to develop until they meet on top of the neural fold to produce a neural tube.

• this will become the ventricles and central canal of the nervous system

what does the neural tube eventually become?

• the spinal cord

during development of the CNS, when do neural crest cells (NCC’s) form?

• form after the fusion of the 2 edges of the neural folds

after formation of the neural tube, the NCC’s give rise to…

• embryonic connective tissue of the facial region and to branchial arch cartilage

what is ectomesenchyme?

• the name for the embryonic connective tissue given rise to by the NCC’s.

• called ectomesenchyme to differentiate it from the mesenchyme produced at the primitive streak (think back to the visualiser card)

• called ‘ecto’ to account for ectodermal origin of NCC’s - not pure connective tissue anymore

why is ectomesenchyme regarded as the 4th germ layer by some authors?

• it influences the structures of the oral cavity and human body

• has properties slightly different to mesenchymal structures elsewhere in the body

• eg) bones of face and cranium (except base of skull) form by intravenous ossification rather than the endochondral method common in other bones

of 6 branchial arches, how many survive in man?

5

as the first branchial arch is lined by ectoderm on the inside and outside, at which branchial arch does the inner lining of endoderm start?

• arch #2

each branchial arch contains:

1. portion of primitive striated muscle tissue

2. some nervous tissue from the neural crest

3. some vascular tissue

4. bar of cartilage in mesodermal core

∴ each arch contains an artery and a nerve

branchial arches support the…

• lateral wall of the primitive pharynx

the first branchial arch (mandibular arch) forms the mandibular division of the ________ nerve

• trigeminal

3 divisions of the trigeminal nerve

1. opthalmic

2. maxillary

3. mandibular

how do bones of the maxilla and mandible form (as they don’t form from remnants of Meckel’s cartilage?

• from intramembranous ossification following degeneration of the cartilage

muscle tissue from the first branchial arch forms what 4 structures?

where do these structures get their motor nerve supply from?

1. masticatory muscles

2. tensor tympani + tensor veli tympani

3. mylohyoid muscle

4. anterior belly of the digastric

• motor nerve supply of these four structures are from branches of the mandibular division/nerve of the trigeminal nerve

does the artery of the first branchial arch survive?

no

the maxillary and mandibular nerve are both supplied by which artery for blood?

the maxillary artery

the 2nd branchial arch (the hyoid arch) develops around the future _____ bone

• hyoid

what is the cartilage in the second (hyoid) arch called?

Reichert’s cartilage (after the anatomist who first described it)

the muscles of facial expression all share a common…

• nerve supply - the facial nerve

muscle tissue of the first branchial arch forms…

1. stapedius muscle

2. stylohyoid muscle

3. posterior belly of the digastric

the face develops from _ embryonic tissue masses, also known as _____

• 5

• processes

name the 5 processes for facial development

1. frontonasal process (1 part)

2. maxillary process (2 parts)

3. mandibular process (2 parts)

all processes (embryonic tissue masses) all arise by what?

• rapid multiplication of NCC’s (neural crest cells) which originate from ectoderm

the 5 processes split to form how many processes that contribute to facial development?

7

3 processes (4 parts) that make up the lips

MIDDLE OF UPPER LIP: frontonasal process

LATERAL PARTS OF UPPER LIP: maxillary processes

LOWER LIP (all): mandibular process

the stomodeum/stomatodeum appears as a ___1___ on the embryonic surface at around _2_ weeks of development. the stomodeum is formed around the same time as the _3_

1. depression

2. 4

3. CNS

the floor of the stomodeum (as it appears as a depression) pushes against what? what is the wall that separates these two structures called? what does it represent?

• the floor of the stomodeum pushes against the developing gut

• the wall that separates these two is called the buccopharangeal membrane

• represents meeting of ectoderm and endoderm

why does the buccopharangeal membrane need to be broken?

• so that direct connection/access between mouth and guts can be established

• the stomodeum can then open directly into the primitive pharynx of the foregut

the face develops between the ___th and the ____th day of gestation

24th, 38th

in the early stages, face development is dominated by changes that create the….

from which processes do these changes occur from?

• primitive nasal cavities

• nasal pits (primitive nostrils), medial and lateral nasal processes from the frontonasal processes

eventually, the maxillary processes will push the __1___ and __2___ processes together, so there will be _3__ medial nasal process/es and __4_ lateral nasal process/es

1. medial

2. lateral

3. 1 process

4. 2 processes

think back to the card that said the 5 processes split into 7…

which process splits so this can happen?

• the frontonasal process

• (frontonasal → 2 lateral and 1 medial process)

• maxillary (2 parts)

• mandibular (2 parts)

• altogether, that’s 7 parts

1. the frontonasal process develops 2 ___ (1)____. tissue builds up around them in a horseshoe shape to form the ___(2)___ and ____(3)_____ nasal processes.

1. nasal pits

2. lateral

3. medial

2. the maxillary process grows medially and approaches the lateral and medial nasal processes. at this stage, it is separated from them by a _____

• groove

3. the continued central growth of the _____ process pushes the ______ nasal process towards the midline

1. maxillary

2. medial

4. from the process of pushing the medial nasal processes together, they fuse to create….

1. the middle part of the nose

2. the middle part of the upper lip

3. the anterior part of the maxilla

4. the primary palate

the primary palate is formed by what? what does the primary palate carry? what else can you refer this structure to as?

• formed by horizontal shelves which fuse together

• carries odontogenic epithelium for maxillary incisors

• can refer to as ‘pre-maxilla’

what does the secondary palate form as a result of?

• the fusion of palatine process (horizontal shelves from the maxillary process)

• end up with Y-shape fusion

the primary palate is formed as a bonus/extra together during the facial development and fusion of the 2 ____ ____ processes into 1

medial nasal

the secondary palate will form as a result of the fusion of the _______ _______. these processes are horizontal shelves extending from the _____ ______. the end result will be a _-shape line of fusion.

1. palatine process

2. maxillary processes

3. Y

only after the formation of WHAT can the distinction between the oral and nasal cavities be seen?

the secondary palate

formation of the secondary palate takes place between the ___th and ___th weeks of development

• 7th

• 8th

the nerve of the primary palate is the….

(broke the answer into bits because reading all that in one sentence is making my head spin ahah)

• incisive branch of the

• long nasopalatine branch of the

• maxillary division of the

• trigeminal nerve

the nerve of the secondary palate is the…

• greater palatine branch of the

• maxillary division of V

what is the tuberculum impar?

• a mesenchymal swelling in the midline of the mandibular process of the first branchial arch

how many other swellings appear either side of the tuberculum impar, and what do these swellings do?

• 2 other swellings appear

• these enlarge rapidly and merge with each other and with the tuberculum impar to cover it and form a large mass

the tongue, during its development, has elements from which arches? what structures do these arches contribute to?

• elements from first, second and third arches

FIRST ARCH

• formation of anterior 2/3rds of the tongue

SECOND ARCH

• eventually disappear and get overpowered by the 1st and 3rd branchial arches

• mainly contribute to taste sensation

• smaller elements compared to 1st and 3rd branchial arches

THIRD ARCH

• posterior 1/3rd of the tongue

all the tongue’s cell divisions, multiplications and swellings are all due to the…

NCC’s

what is median rhomboid glossitis?

• where tuberculum impar isn’t fully covered (incomplete fusion of 2 lateral swellings)

• results in rhomboidal shape on dorsal surface of the tongue at the junction of the anterior 2/3rds and the posterior 1/3rd

• congenital condition

once lateral swellings fully cover the tuberculum impar, what is formed? what branch is this formed from and why?

• the mucous membrane structures of the anterior 2/3rds of the tongue is formed

• all elements of the first branchial arch

• all supplied by lingual nerve (branch of mandibular division of trigeminal nerve → 1st arch)

the anterior 2/3rds and the posterior 1/3rd of the tongue gets its motor nerve supply from…

what muscles does this motor nerve supply for?

• the hyperglossal nerve (cranial nerve #12)

• supply for all intrinsic and extrinsic muscles of the tongue except for the palatoglossus muscle

sensory sensation, special sensation and motor sensation of the tongue definitions

SENSORY

• temperature

• pain

• pressure

• touch

SPECIAL

• taste sensation

MOTOR

• contraction of muscles

• tongue movement

the nerve of the second arch contributes _____ _______ to the anterior 2/3rds of the tongue via the _____ _______

1. taste fibres (for taste sensation)

2. chorda tympani

what is the chorda tympani?

• branch of the facial nerve

• nerve supply for the second branchial arch

the posterior part of the tongue arises from a __________(1)_ __________ (a large midline swelling in the 3rd branchial arch).

the nerve of which becomes the ______(2)_______ nerve (cranial nerve #_(3)__). this is the main nerve supply for the __(4)_rd branchial arch.

the posterior part of the tongue comes to be supplied by _(5)___, and develops from __(6)__ piece, unlike the anterior 2/3rds which develop from __(7)__ pieces.

1. hypobrachial eminence

2. glossopharangeal

3. 9

4. 3 (3rd)

5. IX

6. 1 (1 piece)

7. 3 (3 pieces)

what is the sulcus terminalis?

• fusion of the anterior and posterior parts of the tongue

• V-shape line

what is the last tissue to develop during embryological life?

• bone

list the order that tissues form during embryological life?

1. nerves

2. blood vessels

3. some muscles (fill in spaces between first two structures)

4. bone (will form tubes, lamina, canals etc around vessels)

how does the mandible form?

• under influence of NCC’s, the 2 mandibular processes fuse in the midline to form a mandibular arch

• line of fusion is called symphisis menti

• the bone of the mandible begins to form in the mesenchymal tissue that condenses laterally to the cartilage

• the cartilage (Meckel’s) begins to disappear

• there will be bony islands around the developing tooth germs (start forming the crypts)

~ link between oral histology and head and neck anatomy ~

• link the formation of the mandibular crypts to the tooth germ

• in the tooth germ: enamel organ, dental papilla and dental sac

• from dental sac, there will be mesenchymal condensations from developing tooth germs (bits of bone fuse and form the crypt where developing tooth germs sit)

• once the tooth erupts, the crypts turn into sockets (accommodating for roots)

by __ weeks of age, the rudimentary mandible is formed almost entirely from ____________ __________ with little direct involvement from _______ _______.

1. 10

2. intramembranous ossification

3. Meckel’s cartilage

although Meckel’s cartilage does not contribute much to mandible formation, what structures’ development does it contribute to?

1. malleus of the ear and its ligament

2. sphenomandibular ligament

the maxilla also develops from a ________ of ______ from the ____ branchial arch

1. condensation

2. mesenchyme

3. first

is there cartilage present in the maxillary process?

what is bone formation made entirely by?

• no cartilage

• made entirely by intramembranous ossification

when does the maxillary sinus form?

• in the 16th week

do the mandible and the maxilla develop at the same time? if not, which develops earlier?

• not at the same time

• mandible always ahead of maxilla in development

• think about eruption dates of teeth!

what are congenital defects?

• malfunctions in the development of a person

• defects can be genetically or environmentally caused

list the 5 groups of environmental factors that affect the embryo

1. infectious agents

2. ionising radiation

3. drugs

4. hormones

5. nutritional deficiences

• they could exaggerate an existing genetic factor, or trigger failure in a step of embryological development

________ clefts are among the most common congential defects

• orofacial

what is the difference between a complete and an incomplete cleft lip?

• complete extends into the nasal cavity

• incomplete does not

what is a unilateral cleft upper lip?

• the failure/incomplete fusion of the maxillary process and the lateral nasal processes

• can be uni or bilateral

• can never have a midline cleft, however, because 1 solid piece of medial nasal process in the middle

are…

• unilateral or bilateral cleft lips more common?

• left or right unilateral cleft lips more common? why?

• unilateral

• left - defects tend to occur in the nondominant side of the individual, as there are more right-handed people globally, unilateral left is more common

can cleft palates and cleft lips occur together?

• yes

what is a cleft palate?

• the 2 palatine processes fail to fuse together

if a lower lip cleft lip occurs (as its very rare), where would it be present on on the lip?

• in the midline