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