Congenital Lesions of the Face and Neck Flashcards
The majority of the facial structures originate from what cells created during embryology?
- cranial neural crest cells
- migrate from the neural tubes at the back of the foetus
Following the formation of the trilaminar germ disk, around 3-4 weeks, a cord is formed from the ectoderm and runs into the mesoderm. What is this cord called?
- notochord
Following the formation of the trilaminar germ disk, around 3-4 weeks, a cord is formed from the ectoderm and runs into the mesoderm, called the notochord. What does this cord then do to the ectoderm?
- causes cells in ectoderm to thicken forming the neural plate at the back of the embryo
- neural plate edges fold forming the neural folds and then form the neural tube
Following the formation of the trilaminar germ disk, around 3-4 weeks, a cord is formed from the ectoderm and runs into the mesoderm, called the notochord. The notochord then causes cells in ectoderm to thicken forming the neural plate at the back of the embryo. The neural plate edges then fold forming the neural folds and then form the neural tube. What cell is present along the edges of the whole neural tube?
- neural crest cells
Following the formation of the trilaminar germ disk, around 3-4 weeks, a cord is formed from the ectoderm and runs into the mesoderm, called the notochord. The notochord then causes cells in ectoderm to thicken forming the neural plate at the back of the embryo. The neural plate edges then fold forming the neural folds and then form the neural tube. Neural crest cells then form along the edges of the whole neural tube, and depending on where the neural crest cells are determines their name and what they go on to develop. What are the neural crest cells of the head/cranial region called?
- cranial neural crest cells
- go on to form the features of the face
What are the pharyngeal arches?
- paired structures formed in the ventrolateral (front to the side) parts of the head of the embryo
- formed of mesenchymal tissue (connective tissue from the mesoderm)
- in the cranial region of the embryo the formation of arches, separated by clefts and pouches
The pharyngeal arches are paired structures formed in the ventrolateral parts of the head of the embryo from mesenchymal tissue (connective tissue from the mesoderm) in the cranial region of the embryo. How many arches will be formed?
- 6 arches in total (although arch 5 is not present in humans)
- 1 is highest cranially and 6 is lowest (caudally)
- these will form the head and neck structures
The pharyngeal arches are paired structures formed in the ventrolateral parts of the head of the embryo from mesenchymal tissue (connective tissue from the mesoderm) in the cranial region of the embryo. 6 pharyngeal arches form (although 5 is not present in humans). What separates each of the pharyngeal arches?
- clefts and pouches
- clefts are outside embryo (think cleft lip) and part of ectoderm (4 in total)
- pouches are inside the embryo as part of endoderm (4 in total)
The 4 pharyngeal pouches that are formed from endoderm line the inside of the 6 pharyngeal arches containing mesenchymal tissues originating from the mesoderm. What do the pharyngeal pouches go on to form from embryo development?
- foregut
- gut tube
Each pharyngeal arch (bulge containing mesenchymal tissue) receives an influx of neural crest cells and is formed from what 2 components of the mesoderm?
1 - paraxial plate mesoderm
2 - lateral plate mesoderm
Each pharyngeal arch (bulge containing mesenchymal tissue) receives an influx of neural crest cells and is formed from paraxial and lateral plate mesoderm. What 4 components does each pharyngeal arch contain?
1 - artery
2 - nerve
3 - connective tissue cells
4 - muscle cells
What is rhombomere?
- a transiently divided segment of the developing neural tube, within the hindbrain region
Rhombomeres are transiently divided segment of the developing neural tube, within the hindbrain region. Which pharyngeal arch do the neural crest cells of rhombomeres 1 and 2 migrate to?
- 1st pharyngeal arch
At week 4 a depression on the surface of the future face forms. What is this depression called?
- stomodeum
At week 4 a depression called the stomodeum forms on the surface of the future face forms. As the embryo continues to develop what will this depression eventually become?
- it will become the mouth
- continuous with the gut tube
The first pharyngeal arch surrounds the stomodeum and can be divided into 2 processes, what are these processes called?
1 - dorsal maxillary process
2 - ventral mandibular process
The mandibular process of the 1st pharyngeal arch contains a special type of cartilage. What is this cartilage called?
- Meckels cartilage
- important for providing the horse shoe shaped model for the mandible to form
- important for also forming the incus and malleus of the middle ear
The mandible forms bone through ossification. Is this intramembranous or endochondral ossification?
- intramembranous ossification
- most bones of the skull form this way
Which cranial nerve and branch will innervate the products created by the pharyngeal arch number 1?
- cranial nerve V (5) the trigeminal nerve
- mandibular branch (provides motor fibres for chewing)
- maxillary branch
Label the bones that are formed from the 1st pharyngeal arch and the nerve that innervates the components created by the 1st pharyngeal arch using the labels below:
temporal bone zygomatic bone trigeminal nerve mandible maxillary malleus incus
1 - maxillary 2 - mandible 3 - trigeminal nerve 4 - incus 5 - malleus 6 - temporal bone 7 - zygomatic bone
The 1st pharyngeal arch creates the muscles associated with chewing. What are the 3 key chewing muscles?
1 - temporalis
2 - masseter
3 - pterygoids
Which artery provides the blood supply for the structures created by the 1st pharyngeal arch?
- maxillary artery
The first pharyngeal cleft is formed from the ectoderm and separates pharyngeal arches 1 and 2. By week 5 what will the 1st pharyngeal cleft form?
- external auditory meatus of the ear
- forms a foreman
The 1st cleft forms the external auditory meatus, but what happens to pharyngeal clefts 2-4?
- form the cervical sinus
- this will eventually disappear
The malleus and incus bones of the inner ear are formed from the 1st pharyngeal arch. Which arch forms the stapes bone of the inner ear?
- 2nd pharyngeal arch
The first pharyngeal pouch is formed from the endoderm and separates pharyngeal arches 1 and 2. By week 5 what will the 1st pharyngeal pouch form?
- forms a lengthy ingrowth which becomes the tubotympanic precess
- the 1st pharyngeal pouch extends towards the first cleft connecting with the foreman formed by the 1st pharyngeal cleft
The first pharyngeal pouch is formed from the endoderm and separates pharyngeal arches 1 and 2. By week 5 the 1st pharyngeal pouch forms a lengthy ingrowth which becomes the tubotympanic precess. The the 1st pharyngeal pouch extends towards the first cleft connecting with the foreman formed by the 1st pharyngeal cleft. What 2 areas will the tubotympanic precess form?
- dorsal (closer to the back) part forms the middle ear cavity
- ventral (closer to the front) part forms the auditory tube
In addition to forming the tubotympanic precess, the 1st pharyngeal pouch also forms what in the ear?
- pharyngotympanic tube, also known as the eustachian tube
If the cranial neural crest cells from rhombomers 1 and 2 failed to migrate, what could happen to the components created by pharyngeal arch 1?
- could form congenital abnormalities/birth defects
What is Treacher Collins Syndrome?
- syndrome linked to mutation in gene on chromosome 5
- gene mutation prevents neural crest cells from migrating
- can be inherited or random mutation
Treacher Collins Syndrome is a syndrome linked to mutation in gene on chromosome 5 that prevents neural crest cells from migrating. What can this then present as?
- can affect anything formed by pharyngeal arch 1
- craniofacial abnormalities
- cleft palate, small mandible and malformed or absent ears
What is Pierre Robin sequence?
- not a known genetic cause
- altered sequence of development form pharyngeal arch 1
Pierre Robin sequence is a syndrome that does not have a known genetic cause, but there is an altered sequence of development form pharyngeal arch 1. How can this present in patients?
- small mandible (bottom of jaw), cleft palate and upper airway obstruction
- need to be treated with nasopharyngeal cannulation for breathing and feeding
Pharyngeal arch 2 is responsible for forming 1 bone in the ear, in conjunction with a pharyngeal arch 1 which forms 2 bones in the ear. Which bones does each pharyngeal arch make?
- pharyngeal arch 1 = malleus and incus
- pharyngeal arch 2 = stapes
Pharyngeal arch 2 is responsible for forming the stapes bone of the middle ear. What other 3 key structures does pharyngeal arch 2 create:
1 - incus, stapes, styloid process (SP), cricoid cartilage
2 - stapes, SP, hyoid, stylohyoid ligament (connects hyoid and SP)
3 - stapes, hyoid, cricoid cartilage, incus
4 - stapes, hyoid, thyroid cartilage stylohyoid ligament (connects hyoid and SP)
2 - stapes, SP, hyoid, stylohyoid ligament (connects hyoid and SP)
Pharyngeal arch 2 is responsible for forming the stapes bone of the middle ear. What muscle associated with the stapes bone does pharyngeal arch 2 create, also the smallest muscle in the body?
- stapedius muscle
Which 2 pharyngeal arches go on to form the hyoid bone?
- pharyngeal arches 2 and 3
Which cranial nerve is formed from pharyngeal arch 2?
- cranial nerve VII (7) facial nerve
- run through middle ear which is associated with pharyngeal arch 2
Cranial nerve (CN) VII (7) the facial nerve is formed from pharyngeal arch 2 as it runs the through middle ear which is formed from pharyngeal arch 2. What is the main function of CN VII?
- facial expression
What happens to the blood vessels that are originally formed from the pharyngeal arch 2?
- they disappear
The stapedial artery is formed from the pharyngeal arch 2. Which 2 important arteries does this initially connect before it disappears forming a foreman?
- internal and external arteries
The stapedial artery is formed from the pharyngeal arch 2. It forms a connection between the internal and external arteries before it disappears forming a foreman. In some patients this artery does not disappear and remains. if a patient has this artery what do they complain of and how can this be treated?
- complain of hearing pulse in their ears
- can cause deafness
- can be treated with surgery
What is a key artery that is associated with the formation of pharyngeal arch 1 and 2?
middle meningeal artery
In addition to the stapedial artery that is formed from pharyngeal arch 2, which other artery is formed by pharyngeal arch 2?
- hyoid artery
The pharyngeal clefts are what separate the pharyngeal arches on the outside of the foetus and are formed by ectoderm. Pharyngeal cleft 2 becomes isolated from the outside environment and merges with pharyngeal clefts 3 and 4 to form what?
- cervical sinus (but disappears with normal growth)
- lines with aectodermal epithelia
The pharyngeal clefts are what separate the pharyngeal arches on the outside of the foetus and are formed by ectoderm. Pharyngeal cleft 2 becomes isolated from the outside environment and merges with pharyngeal clefts 3 and 4 forming the cervical sinus (but disappears with normal growth) which is lined with aectodermal epithelia. The ectodermal epithelia are involved in the formation of the Hassall’s corpuscles, which are part of what organ?
- thymus
The pharyngeal pouches are what separate the pharyngeal arches on the inside of the foetus and are formed by endoderm. What happens to the endoderm of the 2nd pharyngeal pouch and what does this form?
- proliferates and enters mesenchymal tissue below
- forms lymphoid tissue made from mesoderm, specifically the palatine tonsils
The pharyngeal pouches are what separate the pharyngeal arches on the inside of the foetus and are formed by endoderm. The endoderm of the 2nd pharyngeal pouch proliferates and enters mesenchymal tissue below forming lymphoid tissue made of mesoderm. Specifically what lymphoid tissue does this form?
- palatine tonsils
Generally the pharyngeal clefts, which separate the pharyngeal arches on the outside of the foetus and are composed of ectoderm disappear throughout foetal development. However, if the the pharyngeal clefts remain what can this form and where is this located?
- pharyngeal cysts
- under the platysma muscle
- anteriorly to the sternocleidomastoid muscle
- treatment is through surgery
Generally the pharyngeal clefts, which separate the pharyngeal arches on the outside of the foetus and are composed of ectoderm disappear throughout foetal development. However, if the the pharyngeal clefts remain this can form pharyngeal cysts under the platysma muscle and anteriorly to the sternocleidomastoid muscle. What can the pharyngeal cysts do?
- swell and enlarge
- generally asymptomatic
- BUT can open externally as a sinus and can cause paralysis and loss of facial expression
Generally the pharyngeal clefts, which separate the pharyngeal arches on the outside of the foetus and are composed of ectoderm disappear throughout foetal development. However, if the the pharyngeal clefts remain this can form pharyngeal cysts under the platysma muscle and anteriorly to the sternocleidomastoid muscle. This can cause Goldenhar syndrome, what is this syndrome?
- pharyngeal cysts development cause facial paralysis
- can cause bone deformation including maxilla and zygomatic bones
When does the 3rd and 4th pharyngeal arches form in foetal development?
- > 28 days
Are the 3rd and 4th pharyngeal arches larger than the 1st and 2nd arches?
- no
Which cranial nerve is formed by the 3rd pharyngeal arch?
- cranial nerve IX (9) the glossopharyngeal nerve
- innervates the sylopharyngeus muscle and is important in swallowing
Which muscle is formed by the 3rd pharyngeal arch?
- stylopharyngeus muscle
- runs between the styloid process and the pharynx
- important for swallowing
Which bone along with the 2nd pharyngeal arch is formed by the 3rd pharyngeal arch?
- hyoid bone
CN IX (9) the glossopharyngeal nerve supplies the stylopharyngeus muscle and is important in swallowing. It also provides the motor fibres and sensory fibres to the pharyngeal plexus for innervation of the muscles and mucosa of the pharynx. What cranial nerves contribute towards the pharyngeal plexus?
- glossopharyngeal nerve (CN IX (9))
- vagus nerve (CN X (10)) fibres
Generally the pharyngeal pouches, which separate the pharyngeal arches on the inside of the foetus and are composed of entoderm. The 3rd pharyngeal pouch is involved in the formation of endocrine glands in the neck. Specifically what endocrine tissue does the 3rd pharyngeal pouch form?
- migrate to posterior where the thyroid gland would be
- become inferior parathyroid glands (from ventral wing of 3rd pharyngeal pouch)
- become thymus (from ventral wing of 3rd pharyngeal pouch)
Generally the pharyngeal pouches, which separate the pharyngeal arches on the inside of the foetus and are composed of entoderm. The 4th pharyngeal pouch is involved in the formation of endocrine glands in the neck. Specifically what endocrine tissue does the 4th pharyngeal pouch form?
- forms the superior parathyroid glands
If there is any congenital defects that affect the normal development of pharyngeal pouch 3, this would affect the inferior parathyroid and thymus glands. What is common hypo condition that can form form congenital abnormalities in pharyngeal pouch 3?
- congenital hypoparathyroidism
- often undiagnosed until 2 years of age
- can cause seizures and poor growth
If there is any congenital defects that affect the normal development of pharyngeal pouch 3, this would affect the inferior parathyroid and thymus glands. Any parathyroid tissue that remains during migration can form what?
- ectopic parathyroid tissue
Neural crest cells from which rhombomeres will migrate into the 3rd and 4th pharyngeal arch?
- rhombomere 6
Label the cartilages that form from pharyngeal arches 4 and 6 using the labels below:
cricoid
arytenoid
thyroid
cuneiform
1 - thyroid
2 - arytenoid
3 - cricoid
4 - cuneiform
The 3rd and 4th pharyngeal arch will form which muscles?
- intrinsic muscles of the larynx
- constrictors of the pharynx
Which cranial nerve develops from pharyngeal arches 4 and 6?
- cranial nerve X (10) the vagus nerve
The vagus nerve develops from the pharyngeal arches 4 and 6. What other nerve develops from pharyngeal arch 6?
- recurrent laryngeal
- branch of the vagus nerve
The pharyngeal arches, also called aortic arches contribute towards blood vessels. What do the left (L) and right (R) 4th pharyngeal arches form:
1 - R = R subclavian artery and L = arch of adult aorta
2 - R = R pulmonary artery and L = L pulmonary artery
3 - R = R subclavian artery and L = L subclavian artery
4 - R = R subclavian artery and L = L pulmonary artery
1 - R = R subclavian artery and L = arch of adult aorta
The pharyngeal arches, also called aortic arches contribute towards blood vessels. What do the left (L) and right (R) 4 pharyngeal arches form:
1 - R = R subclavian artery and L = arch of adult aorta
2 - R = R pulmonary artery and L = L pulmonary artery
3 - R = R subclavian artery and L = L subclavian artery
4 - R = R subclavian artery and L = L pulmonary artery
2 - R = R pulmonary artery and L = L pulmonary artery
Any deformities or abnormalities in the development of pharyngeal arches 4 and 6 can cause a number of conditions, one of which is abnormal development of the cartilages depicted below. What can this cause?
- tracheal stenosis which requires surgery to treat
- can affect normal breathing
Any deformities or abnormalities in the development of pharyngeal arches 4 and 6 can cause a number of conditions, one of which is Laryngomalacia. What is Laryngomalacia?
- translates as soft cartilage
- common cause of noisy breathing in infants
- larynx (or voice box) is soft and floppy
- breathing can be temporarily blocked
- generally babies grow out of this
What is DiGeorge syndrome?
- also known as hypoparathyroidism
- causes by congenital defects in the 4 pharyngeal arch
- can cause heart defects, learning difficulties, muscle cramps, pain in the face, dry hair
- treated with Ca2+, vitamin D and synthetic parathyroid hormone
The structure of the face and mouth mainly occur when in foetal development?
- first 3 months
Around the fifth to sixth week of pregnancy is when the two sides of a baby’s upper lip fuse together. If there is any problem in this process, what can be formed?
- cleft lip
By the eighth to ninth week of pregnancy, the roof of the palate should be formed including:
- the hard palate
- the firm and bony plate
- the flexible, fleshier tissue that spans the back of the mouth
The two sides of a baby’s palate fuse, but if there is any problem in this process, what can be formed?
- cleft palate
Cleft lip and palate are due to abnormalities in the face and mouth development during foetal development. Are boys or girls more at risk?
- boys
- affects 1/700 babies
Cleft lip and palate are due to abnormalities in the face and mouth development during foetal development. Which ethnicities are more at risk?
- Asian, Latino, and Native American descent
Cleft lip and palate are due to abnormalities in the face and mouth development during foetal development. Can this be treated?
- yes
- very treatable but may need multiple surgeries
