510-3 Flashcards
In which two directions does an embryo fold?
Cephalocaudally and laterally
What are the three components of the embryonic pharynx?
Pharyngeal arches, clefts, and pouches
Instead of “PHARYNGEAL arches”, you might hear:
“BRANCHIAL Arches”
The gastrointestinal tract of an embryo is lined by _________ .
Endoderm
Pharyngeal arches are separated from each other by _____ ______ ______ and _____ _____ _____. Each pharyngeal arch develops its own ______ , _______ , ______ , and ______ elements of the head and neck.
internal pharyngeal pouches, external pharyngeal clefts, artery, nerve, muscle, skeletal
Pharyngeal CLEFTS are also called:
Pharyngeal GROOVES
What is the name of the structure containing the hollow developing brain? It is also continuous with the _____ _____ _____ ____.
The Frontal Prominence (FP). It is continuous with the Dorsal Hollow Nerve Cord (DHNC).
Mesenchyme is composed of these two things:
mesoderm and neural crest cells
Name the three example signaling molecules responsible for guiding Neural Crest Cells into the pharyngeal arches.
Sonic hedge hog (Shh), Bone morphogenic proteins (Bmp), and Fibroblast growth factors (Fgf). Side note: Each of the pouches gets a population of neural crest cells
How do migrating neural crest cells regulate differentiation of different head and neck tissues?
By establishing regional growth factors gradients that are regulated temporally and spatially by expression of Hox genes.
Main derivatives of the First Arch:
Mandible, Maxilla, Meckel’s Cartilage
Meckel’s Cartilage is responsible for setting up the development of:
Mandible, Malleus, Incus, Stapes
Main derivatives of the Second Arch:
- Reichert’s Cartilage
a. styloid process of temporal bone
b. stylohyoid ligament
c. lesser horns of the hyoid bone
d. upper part of the body of the hyoid bone
Main derivatives of the Third Arch:
- lower part of the body of the hyoid bone
2. greater horns of the hyoid bone
Main derivatives of the Fourth Arch:
Cartilages of the larynx
Main derivatives of the First Groove:
External Auditory Meatus
Main derivatives of the First Pouch:
tympanic membrane, tympanic cavity, mastoid antrum, eustachian tube
Main derivatives of the Second Pouch:
Contributes to tonsil
Main derivatives of the Third Pouch:
inferior parathyroid gland, thymus
Main derivatives of the Fourth Pouch:
superior parathyroid gland, ultimobranchial body
Some derivatives of the Neural Crest:
CT and bones of the face and skull, C cells of the thyroid gland, Odontoblasts, Dermis of the face and neck, schwann cells, glial cells, melanocytes, smooth muscles to blood vessels of the face and brain
What connects the ectoderm to the endoderm in the stomodeum that prevents the growth of mesodermal tissue in that area?
The Buccopharyngeal membrane
Pharyngeal arches are lined with:
Endoderm.
Remember that when looking at a picture, the first pharyngeal arch has both a maxillary ______ and a mandibular _________.
prominence, prominence
The name of the cartilage found in arch #2:
Reichert’s Cartilage
The name of the cartilage found in arch #1:
Meckel’s cartilage
The cartilages of the first and second pharyngeal arches are derived from ____ ____ ____. While the cartilages of the 3rd-6th arches are derived from ______ .
neural crest cells, mesoderm
Thyroid cartilage is derived from Pharyngeal Arch #___
4
Cricoid cartilage is derived from Pharyngeal Arch #___
6
By what process do the maxillary bones develop from?
Intramembranous ossification
What does condensed mesenchyme in the maxillary process of the first arch produce?
The maxilla.
What does condensed mesenchyme lateral to Meckel’s cartilage develop?
A part of the mandible.
The ramus and condyle growth of the mandible takes place by which process?
Endochondral Ossification
What is housed within the mandibular canal?
The inferior alveolar nerve
What happens to most of the condylar cartilage of the mandible?
It is replaced by bone through endochondral ossification.
What would a disruption of Neural Crest Cells cause?
Treacher Collins Syndrome. (Mandibulofacial dysostosis)
Which gene is likely the cause of Treacher Collins Syndrome?
Treacle. It is responsible for preventing apoptosis and maintaining proliferation in neural crest cells, but NOT for regulating their migration.
Name and number the four important cranial nerves:
- Trigeminal (assoc. with Arch #1)
- Facial (assoc. with Arch #2)
- glossopharyngeal (assoc. with Arch #3)
- Vagus (assoc. with Arch #4)
Nerve 5 (Trigeminal) innervates muscles:
relating to mastication (ex: temporal, masseter, mylohyoid)
Nerve 7 (Facial) innervates muscles:
relating to facial expression (ex: frontalis, orbicularis oris)
Nerve 9 (glossopharyngeal) innervates muscles:
stylopharyngeus
Nerve 10 (vagus) innervates muscles:
Cricothyroid, levator, intrinsic muscles of larynx
Arch 1 mesoderm develops into the muscles of ______.
mastication.
Arch 2 mesoderm develops into the muscles of ______.
facial expression
Arch 3 and Arch 4 mesoderm develops into ______.
strap muscles of neck
What do the second, third, and fourth clefts fuse to temporarily form that eventually disappears?
The cervical sinus.
What is the ultimobranchial body responsible for?
It comes from the 4th pouch and is incorporated into the thyroid gland. It gives rise to the parafollicular, or C-cells of the thyroid gland that secrete the hormone calcitonin (regulates blood calcium levels).
These types of cysts are formed on the lateral side of the sternocleidomastoid muscle:
Lateral Cervical Cysts. Typically are not dangerous and formed from the cervical sinus.
These types of cysts will always form on the midline:
Thyroglossal Cyst. Formed by oral ectoderm tissue along the migration pathway from the foramen cecum towards the larynx/trachea.
Name the five prominences that make up the face:
Frontonasal (no pair), maxillary (pair), medial nasal (pair), lateral nasal (pair), mandibular (pair)
What is the name of the flat areas that appear on the frontonasal prominence that will eventually become the nose?
Nasal placodes
The nasal ______ invaginate to form nasal ____ and are surrounded by elevated ridges called the medial and lateral _____ _______.
placodes, pits, nasal prominences
Fusion of which prominences form the upper lip?
The two medial nasal prominences and the two maxillary prominences
Fusion of which prominences form the lower lip and jaw?
The mandibular prominences
Which is more difficult and more commonly leads to error? Fusion of the mandibular processes or fusion of the maxillary/palatal processes?
Fusion of the palatal processes
Medial growth of the two maxillary prominences compresses the medial nasal prominences into the intermaxillary segment. This forms the:
- philtrum of the upper lip
- the part of the maxilla that holds the 4 upper incisors
- the triangular primary palate
The main part of the palate develops from the palatine shelves which then fuse to create the _____.
secondary palate
The _____ ______ is at the midline junction where the primary palate joins the fused palatal shelves.
incisive foramen or incisive fossa
Is cleft lip more common in males or females?
Males
Is cleft palate more common in males or females?
Females
Is cleft palate heritable?
Yes, to a small degree
Can certain teratogens increase the risk of having a baby born with a cleft palate?
Yes
Can a baby be born with cleft lip and not a cleft palate?
Yes
Can a baby be born with a cleft palate and not a cleft lip?
You betcha
What does the body of the tongue develop from?
Fusion of the lateral lingual swellings and the tuberculum impar of the 1st Arch.
What does the root of the tongue develop from?
The copula of the 3rd Arch.
What does the epiglottis develop from?
The epiglottal swelling of the 4th Arch.
Name the two defects that can occur with formation of the tongue:
Bifid tongue, which is basically an incomplete fusion down the middle. Ankyloglossia (tongue-tie) in which the frenulum may still be connected in the wrong place due to a problem with apoptosis.
