Development of Head, Neck and Oral Cavity Flashcards
Craniocaudal folding occurs ________
Ventrally
This is longitudinal.
Lateral folding is ___________.
Left and right sides of embryo folding ventrally towards midline, fuse and form a cylindrical embryo
This is what forms the body cavity!
Embryonic Folding is _______ and ________
Ventral Craniocaudally
Grows laterally and folds towards midline (transverse)
What folding of the embryo is responsible for the tube in tube structure of the embryo?
Lateral Folding
(Gut tube is inner and out wall is body tube)
Neurulation occurs _____________.
as lateral edges of neural plate fold dorsally to create the midline of the neural groove
Folded edges of neural plate meet and fuse at dorsal midline and groove is converted to tube
Originates from ectoderm
What induces the neural plate to form into a groove that eventually closes off to form the neural tube?
Sonic Hedgehog being released from NOTOCHORD
Neural crest cells develop from the __________.
ectoderm
What actually touches when the neural groove fuses?
The Neural crest cells.
Once the fusion takes place, the neural crest cells will migrate away from the closed tube
What can neural tubes do?
Form external parts of the heart
Pigment in Skin
Peripheral Nervous System
Ganglion form from ________.
Neural crest cells
Somites form from the _________ and are ___________
paraxial mesoderm and are epithelial balls of cells along the neural tube that make up the vertebrae, muscles of back and body, dermis of skin
The first parts of the neural tube to fuse are the _______ followed by the ________.
5th Somite pair
Cranial and Caudal ends
The conversion of the neural plate into a neural tube occurs on _________ at the __________.
Day 22
Count from Cervical region -the 5th somite
In an embryo, the “cervical” region where the 5th somite will fuse on Day ___ will look like it is in the MIDDLE of the embryo. Why is this?
Day 22
The caudal end grows SLOWER than the cranial end. As a result, the cervical region appears more in the middle until growth has got up.
Fusion of the neural tube proceeds ___________.
At Day 23, _____________ are still open to the amniotic cavity
Cranially and Caudally
Cranial and Caudal neuropores
At Day 23, the neural tube is exposed to ________ because __________.
What SHOULD remain in the neural tube after fusion is complete?
Amniotic Fluid because the cranial and caudal ends have not closed
Cerebrospinal fluid should remain
The cranial neuropore closes at Day ____.
The caudal neuropore closes at Day ______.
25
28
Day 22- Fusion Starts from 5th Somite
Day 23- Neuropores still open
If the cranial neuropore does not close, what happens?
Anencephaly
There is NO forebrain
What is annencephaly?
A condition resulting in the lack of a forebrain/brain due to the incomplete closure of the cranial neurpore.
What happens if the caudal neuropore doesn’t close?
Spina Bifida
Incomplete closure of the cranial neuropore can cause ___________
Incomplete closure of the caudal report can cause
_______.
Anencephaly
Spina Bifida
Describe spina bifida as it relates to bone.
A regular vertebra has 3 main processes
- Transverse
- Process B (Dont need to know)
- Spinous Process
The spinous process is formed during fusion. Failure of the caudal neuropore to close does not allow opposing sides of bone around neural tube to close
Hence the name “split spine”
What is spina bifida occulta? What are signs of it?
It is spina bifida hid under skin!
Small patch of hair or discoloration around the area
How is Anencephaly caused by the incomplete ________?
What is a preventative measure for it?
closer of neural tube
The neural tube is exposed to amniotic fluid during development which causes necrosis of neural tissue within.
Folic Acid
Folic Acid is important to _____________.
Decrease the incidence of neural tube defects during development
What is fortification?
A process by which , in this case, folic acid was added to cereal. Over time, neural tube defects decreased.
What are pharyngeal arches?
At Week 4, there will be 3 pharyngeal arches on either side of the embryo.
At Week 5 there will be 4.
The pharyngeal arches will come together to create the path around the developing pharynx.
What is a placode?
A thickening of ectoderm that will develop into one of our sensory organs.
Where is the nose placode located from the ventral view?
What about lens placode?
Nose Placode will appear as two indentations
Lens placode cannot be seen from ventral view because placodes are located extremely lateral on the side of the head.
When looking ventrally,
Under the frontonasal prominence is a _____________.
Where does this structure originate from and what will it eventually turn into?
Stomodeum
The stomodeum develops as the oropharyngeal cavity breaks down. It will eventually turn into the mouth.
The stomodeum turns into the ________.
Mouth
Endoderm derived structures include __________
Head and Neck Anatomy!
Trachea
Bronchi
Lungs
Pharynx
Thyroid Gland
Tympanic Cavity
Pharyngotympanic Tube
Tonsils
Parathyroid Glands
Mesoderm derived structures include ___________.
MUSCLES of head- Paraxial
Connective Tissue - Paraxial
Connective tissue and muscle of viscera - Lateral
Ectoderm derived structures include ______________.
Surface
Skin
Anterior pituitary
Enamel of Teeth
Internal Ear
Lens of Eye
Neural Crest
Cranial and Sensory Ganglia and Nerves
Pharyngeal arch cartilage
Head mesenchyme and connective tissue
Neural Tube
Retina
Posterior Pituitary
The head and neck will arise from the _____________. What is it?
Mesenchyme
Embryonic connective tissue
Where does mesenchyme come from?
The anterior part of the skull also known as ____________ comes from the __________ produced by the ________. ________ also come from this same germ layer.
The posterior part of the skull also known as ____________ comes from the ______.
Ectoderm or Mesoderm.
Viscerocranium, Neural Crest Cells produced by the ectoderm. Placodes
Neurocranium comes from the paraxial mesoderm
Neural crest cells derived from the ectoderm travel into the _________.
A neural crest cell is basically a ________!
Each _________ travels to _____________.
Nerves: ___,____, ____,____
Arch: ____,_____,____,____
pharyngeal arches
cranial nerve
cranial nerve a specific pharyngeal arch
Nerves: 5,7,9,10
Arch: 1,2,3,4-6
Each pharyngeal arch has its own ___________.
- Cranial Nerve
- Blood Supply
- Cartilage
Describe the numbering of the pharyngeal arch from Cranial to Caudal.
Why is it numbered the way it is?
1
2
3
4-6
The aortic arch system develops from the pharyngeal arches.
The 5th arch is TRANSIENT or much much smaller than the other arches. As a result, sometimes it will disappear or never develop at all. The 4 and 6th aortic arches fuse together causing the 4-6 numbering.
What provides the pathway for the neural crest cells to leave the _______ and approach the _____?
hindbrain, pharyngeal arches for face development
Aortic Arch!
What is Digeorge Syndrome?
It is the failure of neural crest cells to migrate to their proper locations.
Neural crest cells are important for the development of the pharyngeal arches as well as the cardiac system and direct development of face and heart.
The cells not migrating to the right place can result in facial and cardiac deformities.
TEMPLE DOC
What are two other names for DiGeorge Syndrome?
Velocardiofacial Syndrome
Catch-22 : 22nd chromosome issue where microdeletion of a portion of it is often what direct neural crest cells.
What disease can be caused by a microdeletion of the 22nd chromosome?
DiGeorge Syndrome
Facial and Cardiac Abnormalities
What are the two major outflow channels of the heart?
Aorta
Pulmonary Trunk
What is the aortico-pulmonary septum?
It is the initial stages of the outflow channels of the heart where the neural crest cells build a wall between the aorta and pulmonary trunk forming a spiral pattern as they eventually divide
This pattern can be seen in our body!
What is the Transposition of the Great Arteries?
TGA is when neural crest cells reach the aortic arches and form the aortico-pulmonary septum, divide the pulmonary trunk and aorta BUT FAIL to create the spiral pattern
This means, deoxygenated blood can travel back to the HEART but it won’t oxygenate it and rather, pump it right back out to the body.
This also means that the side of the heart that just got oxygenated blood from the lungs will pump it right back into the lungs
- Deoxygenated blood into heart and right back out to body
- Oxygenated blood from lungs into heart and right back into lungs
BIG Picture: Oxygenated blood is sequestered to heart
Is there treatment for TGA?
Yes! Surgery, they will have to reroute your system to where the aorta is coming from left ventricle and pulmonary trunk is coming off right.
They can also poke a hole through the right and left atrium as a temporary fix to allow oxygenated blood into the right ventricle so it can be pushed out to the body.
Each pharyngeal arch contains ________ derived from the ________ and __________.
They form in ______ pairs and are covered by ________ externally and ________ internally.
bars of mesenchyme derived from mesoderm and neural crest cells
4 pairs, ectoderm , endoderm
What does the mesenchyme of the the pharyngeal arch differentiate into?
Cartilage that will be ossified into bone
From the dorsal view, describe what the pharyngeal arches look like and structures.
Cranial to Caudal
Arches will appear in a V orientation with the widest arch being 1 followed by 2,3,4-6.
There are 3 major bumps.
The second and third near Arch 3 and 4 turn into the tongue and larynx respectively.
At the stage where there are pharyngeal arches, where was the relative location of the oropharyngeal membrane?
Ectoderm will actually wrap around Arch 1 ONLY.
Think about drawing a line through the end of that ectoderm on arch one separating it from the other arches.
That is where the oropharyngeal membrane would have been.
Where is the mandible located when looking at the pharyngeal arch from the dorsal view?
Arch 1 area with stomodeum on top
What are the 3 main elements found in each pharyngeal arch pair?
- Pharyngeal Arch Nerve - Cranial Nerve
- Pharyngeal Arch Artery - Develops aortic arches
- Cartilaginous element - From mesenchyme
The internal indentation of pharyngeal arches (in the _______) is called a ________.
The external indentation of pharyngeal arches (in the _______) is called a _______.
Which structure is most important to us?
endoderm / Pharyngeal pouch
Ectoderm/ Pharyngeal cleft
First pharyngeal CLEFT
What would happen if there was continuity between the development of pharyngeal pouches and clefts?
We would have gills.
The term Branchial refers to gills
Branchial is synonymous with _______.
It is just an older term.
Pharyngeal
Meckel Cartilage comes from the ___________ in our ____________.
Remember from Tooth Development Lecture: We can see these as small circles in the mandible histologically
bar of mesenchyme in our first pharyngeal arch
Two ossicles of the ______ develop from the _______. The third ossicle called the _____ develops from the ________.
ear, First Pharyngeal Arch
Stapes, Second Pharyngeal Arch
Associate the pharyngeal arches with their cranial nerves
Arch
1 - 5 - Trigeminal
2- 7 - Facial
3- 9 - Glossopharyngeal
4-6: 10 - Vagus
The first pharyngeal crest develops into the ____________. The pouch develops into the _______.
Describe the process and what extra structure is formed.
External auditory foramen (ear hole)
Eustachian Tube (Auditory canal)
The cleft bulges its way closer towards the pouch and creates an ALMOST continuity. The EARDRUM is what is formed to separate the pouch from the cleft.
We know the first pharyngeal arch forms the _________. What happens to the remaining arches?
Ear hole and Auditory Canal
The second arch overgrows the 3rd,4th-6th arches. As a result the CLEFTS of the arches get diminshed down to a tiny cervical sinus which will eventually go away.
Cervical sinus is like a dot
What happens if the cervical sinus doesn’t close?
Pharyngeal Cleft Pathology
Cervical sinus can fill up with fluid and pharyngeal clefts can show up later in life forming
LATERAL CERVICAL CYSTS
How can we diagnose Pharyngeal Cleft Pathology?
The sternocleidomastoid muscle along the neck may have remnants of the 2nd,3rd or 4-6th pharyngeal clefts.
Aside from a lateral cervical cyst, what are two other types of pathologies that could form from Pharyngeal Cleft Pathology
External Branchial/Pharyngeal FISTUAL which is a communication between two hollow organs or something from the inside trying to come out.
Internal Pharyngeal Fistula where lateral cervical cyst communicates with inside of future throat region
KEY: Any pharyngeal cleft abnormalities will be found _______ to the ______.
Anterior to the sternocleomastoid
What happens to each of the pharyngeal pouches?
1- Auditory Canal
- Paltaine Tonsil
- Inferior Parathyroid Gland and Thymus Gland
- Superior Parathyroid Gland and Ultimobranchial body
Ultimobranchia bodies make parafollicular C cells
The thymus gland originates from the _______ and travels to the _______.
3rd pharyngeal pouch and travels to the chest cavity
Parafollicular C cells are responsible for ________.
Calcium Regulation
The thyroid gland is invaded by the ___________ from the ________ and the _________from the _____which grows around the _________. The _______ also insert them selves into the ______.
Where does the main thyroid gland come from?
superior thyroid gland from the 4th pouch
inferior thyroid gland from the 3rd pouch which grows around the superior.
Ultimobranchial Body
The thyroid gland develops from the floor of the developing pharynx at a location called the foramen cecum. The structure migrates inferiorly and places itself ventral to the trachea by the 7th week.
Defects in the middle of the throat are attributed to ________.
Defects on the more lateral portion of the throat are directed to ________.
ThyrOID issues
Cervical Cleft Pathology
At the ________ between __________ and ______ of the tongue there is a _________. As the thyroid gland descends down the midline, it can be marked by the __________. This tissue can get __________ and be found along the path of descent.
border between the anterior 2/3rd and posterior 1/3rd of the tongue there is the foramen cecum which secretes the thyroid gland.
Thyroglossal Duct
Stuck
Thyroid Gland Pathology
Adams Apple - Thyroid tissue stuck on hyoid bone possibly
Thyroid tissue buildup at foramen cecum
Describe Tongue Development
Our cranial nerves have developed by 5 weeks. However, by the 5th month the 5th and 7th cranial nerves get swirled around in the anterior 2/3rds of the tongue.
Pain is sensed by __________. Taste is sensed by _______.
Name the cranial nerve
Cranial 5
Cranial nerve 7
Cranial Nerve 9
General sensation and taste will be sensed by glossopharyngeal nerve.
In the epiglottis from Arch ____ is the _____ which develops the ______nerve.
Does the epiglottis have taste buds?
4-6 is the 10th cranial nerve
Taste and general sensation
Vagus Nerve
YES
What is the landmark between the posterior 1/3 of the tongue and anterior 2/3rds of the tongue ?
Foramen Cecum
At 5 weeks, what is happening to the embryo in the head/neck/oral cavity?
- Nasal placodes are developing a pit in the middle which will come the future nostril.
- Eminences will form medial and lateral to the pit.
At 6 weeks, what is happening to the embryo in the head/neck/oral cavity?
- Eyes are moving more ventral *** REMEMBER WE ARE LOOKING AT EMBRYO FROM VENTRAL VIEW)
- The medial nasal pit will grow towards the lateral.
- The frontal nasal prominence will regress to forehead territory.
What is happening at 7 weeks and 10 weeks.
The mesial nasal eminences have converged in the midline and eyes are moving closer to the center of the face
At 10 weeks the medial nasal prominences is incorporated into the __________.
What does it include?
Intermaxillary Segment
- Labial - Philtrum - Top lip divet
- Jaw - Premaxilla - 4 incisors
- Primary Part Palate
What can the philtrum tell us?
The shape of the philtrum on the lip can hint at congenital issues.
Once the intermaxillary segment has formed the __________ it integrates with the _________.
Philtrum
Primary first palate
Maxilla (4 incisor teeth section)
maxillary process
The nasal septum will grow _________.
Maxillary Prominences create __________ which grow __________ (they are ______ tongue) and then develop a __________ growth pattern where it will be _______ to the tongue.
Eventually the _______ growth from the _________and __________ should ________.
Inferiorly (like down the roof of the mouth if looking at it directly)
Maxillary Prominences create right and left palatine shelves which grow INFERIORLY (they are under the tongue) and then develop a horizontal growth pattern where they will grow superiorly to the tongue.
Eventually the down growth from the nasal septum and the palatine shelves should fuse.
The intermaxillary segment is marked by what feature?
Incisive Foramen where the
- L and R palatal shelves fuse
- Palatal shelves and nasal septum do NOT fuse
What emerges from the incisive foramen?
Nasopalatine nerve that we use to nerve block!
Which teeth will be affected if the _________ nerve located at the incisive foramen is numbed?
Maxillary Incisors!
Nasopalatine
Anterior Cleft Palate is the result of _________.
failure of maxillary process to fuse with
soft tissue portion of intermaxillary segment
Failure of lateral palatine shelf to fuse with intermaxillary segment
ANTERIOR TO INCISIVE FORAMENT
Cleft lip is a _____
soft tissue defect
Posterior Cleft Palate is a result of _____
Failure of L and R lateral palatine processes to fuse with each other AND nasal septum
POSTERIOR TO INCISIVE FORAMEN so anterior portion is probably fine
What is a mark of posterior cleft malformations?
Bifid Uvula
This malformation extends all the way from hard palate to soft.
What are the three types of salivary glands?
Parotid
Submandibular
Submaxillary
How is the parotid gland formed?
- Ectodermal groove forms a sulcus between maxillary and mandibular prominences.
- Groove gets incoporated into buccal wall
- Differentiates into glandular acini and tubular duct.
The glandular acini makes the parotid gland.
The tubular duct (carotid duct) emanates from that in an anterior direction and dives into the oral cavity.
What makes the parotid gland?
The glandular acini that results from the differentiation of the ectoderm groove once it has been incorporated into the buccal wall
Serous only
What causes mumps?
Inflammation of parotid gland
Submandibular glands are located ___________ and form within a _______. The ______ will open _______.
on the right and left side of the mandible in the jaw
Alveolingual groove ( between tongue and tooth socket). The duct will open ADJACENT to the lingual frenulum
Serous and Mucus
A salivary ______ can be formed in the ________ glands.
stone/calculus
submandibular
Sublingual glands form as ___________. _____ converge to ________ but retain ___________ opening into the _____________.
individual buds. Buds converge to form a gland but retain separate openings into the FLOOR of the oral cavity
The cranial neuropore will close completely around Week ___.
Is it open or closed at Week 3?
6
OPEN
The neural tube will form _______ to create the ______ _________.
Describe organization of what the neural tube forms at 3 week and at 6 weeks.
dilations and contrictions (like bulges) to create the brain vesicles.
Primary ones at the 3 week embryo are
Prosencephalon ( will divide into Telen and Dien)
Mesencephalon (future midbrain)
Rhombencephalon (will divide into Meten and Myeln)
Secondary vesicles at 6 weeks are
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon
The prosencephalon differentiates into _____________.
Telencephalon : Forebrain and future hemispheres
Diencephalon: Eyes and the thalumus’s
Eyes are formed by what two things?
Lens placode and diencephalon
Where is the epithalamus?
- Located the large thalamus at the posterior part of the brain.
- Locate a small y-shaped structure at the inferior portion of the thalamus
What is the function of the pineal gland?
Modulate endocrine and behavior rhythms affected by light/darkness we experience through our eyes
What is the pineal gland?
The important part of the epithalamus that is formed from an epithelial thickening at the caudal end of the diencephalon
The pineal gland can accumulate _______.
Calcium
This helps it show up in the x-ray as a BRIGHT white spot.
Where is the hypothalamus ?
- Locate the thalamus. It should be in the center of a sagittal view under a bright white marker.
- The hypothalamus will be directly below that.
Where is the pituitary gland?
BELOW the hypothalamus attached by a stalk.
The pituitary gland sits in a ______ called _______ which is a depression in the ________.
The pituitary gland sits in a bony fossa called stella turcica which is a depression in the sphenoid bone.
The pituitary gland has ______ lobes. What are they and their respective names?
2
Anterior Lobe: Adenohyophysis
Posterior Lobe: Neurohypophysis
Which pituitary lobe is more glandular?
Anterior
Adenohyophysis
The pituitary gland develops from _________
Which lobe does it form?
Describe the rest of pituitary gland development.
the ectoderm that has curved over the 1st pharyngeal arch.
It will ascend to the future anterior lobe of our pituitary.
The hypothalamus will have down growth which will interact with the anterior lobe. The components are initially hollow but eventually grow to fill the space.
The anterior lobe of the pituitary gland develops from the oral _______. The posterior lobe is derived from ______ from _____
ectoderm
neuroectoderm from hypothalamus
What is Raffey’s Pouch?
Oral ectoderm that acends to form the anterior lobe
How does the oral ectoderm ascend to the _______?
Stella turcica
The anterior sphenoid bone and posterior sphenoid bone have not yet fused to each other which allows it to squeeze to the gap into the stella turica
Pharyngeal Hypothesis
Left over pituitary gland in roof of mouth
Macroadenoma
What can macroadenoma cause?
Pushing on Cranial Nerve II - VISION
It will push between the optic chiasm between R and L Cranial Nerves
How can pituitary tumors be removed?
Surgeon can enter through the nasal or oral cavity and hit a piece of bone at the posterior aspect of the pharynx and enter the sphenoid sinus.
This spot is INFERIOR to the stella turcica and can suck up the adenoma.
Is the trans-sphenoidal approach to the the pituitary gland for tumor touching brain tissue?
NO!
