Development of the head and neck week 1 Flashcards
What are the 3 componetns of the branchial (pharyngeal) apparatus?
What is the embryological origin of each? If applicable, what are the general components?
The Branchial (Pharyngeal) Apparatus consists of:
- Grooves (clefts). These are on the outside and they are lined with ectoderm.
- Arches. Each arch has unique skeletal, muscle, nerve and arterial elements.
- Pouches, These are on the inside and they are lined with endoderm.
1-4 in picture: clefts/grooves
Only one cleft remains open. What number cleft is it? (options are 1-4)
What does the remaining open cleft/groove form?
Which arch grows over the remaining clefts? If this process does not occur, what is the result?
Only the 1st pharyngeal cleft remains open forming the external canal.
Normally, the 2nd arch grows over clefts 2,3 and 4. These spaces usually close, but persistence of these closures can appear as a cervical sinus.
How many arches are there?
There are 6 arches, however, arches 4,5, and 6 can be considered as one arch.
What skeletal, muscular, nervous, and arterial structures develop from arch 1?
Skeletal
- Maxilla
- Mandible
- Malleus
- Incus
Muscles
- Muscles of mastication (4)
- Mylohyoid
- Digastric (anterior belly)
- Tensor palatini
- Tensor tympani (tenses middle ear during chewing and swallowing)
Nerves
- Trigeminal (CN V)
Arteries
- Regresses (do not persist)
If a person has arch 1 syndrome, they may have issues with chewing and swallowing. May have a recessed mandible. May also have conductive deafness (which can be repaired).
What skeletal, muscular, nervous, and arterial structures develop from arch 2?
Skeletal
- Stapes
- Styloid process
- Hyoid bone (upper part)
Muscle
- Facial expression
- Stapedius
- Digastric (posterior belly)
- Stylohyoid
Nerves
- Facial (CN VII)
Arteries
- Regress
What skeletal, muscular, nervous, and arterial structures develop from arch 3?
Skeletal
- Hyoid bone (lower part)
Muscles
- Stylopharyngeus (retraction and elevation of the tongue
Nerves
- Glossopharyngeal (CN IX)
Arteries
- Carotids
What skeletal, muscular, nervous, and arterial structures develop from arches 4-6?
Skeletal
- Laryngeal cartilages (thryoid and cricothyroid cartilages)
Muscles
- Cricothyroid
- Intrinsic laryngeal muscles
- Levator palatini
- Pharyngeal constrictors
Nerves
- Vagus (CN X)
Arteries
- Aorta
- Subclavian
What is the name of the cartilage that gives rise to the malleus, incus, and mandible?
What is the name of the cartilage that gives rise to the stapes of the middle ear, styloid process, and upper part of the hyoid bone?
- 1st arch. Meckel’s cartilage gives rise to the malleus, incus and future mandible.
- 2nd arch. Reichert’s cartilage gives rise to the stapes of the middle ear, the styloid process and upper part of the hyoid bone.
- 3rd arch. No named cartilage. Gives rise to the lower part of the hyoid bone.
- 4th – 6th arches. No named cartilage. Give rise to the cartilages of the larynx.
What cells migrate to form muscles of the branchial arches? From where do these cells migrate?
Myoblasts migrate from the occipital myotomes to the branchial arches. Cells then migrate to various parts of the head and neck to form the muscles of mastication, facial expression, etc.
Each branchial arch contains an artery called an ____ ____.
Which of the branchial arch arteries persists in an altered form in the adult?
Do all of these arteries exist at the same time?
Each branchial arch contains an artery called an aortic arch. Only certain aortic arches remain in the adult.
Not all aortic arches are present at the same time. By the time the sixth pair of arches has developed, the first two pairs have degenerated. Only aortic arches that remain in an altered form in the adult are the 3rd, 4th and 6th.
How many pharyngeal pouches are there? What structures are formed from each pharyngeal pouch?
- 1st pouch: This depression forms the Eustachian tubes, tympanic cavity (middle ear), and mastoid cavity
- 2nd pouch: Located in this depression are the palatine tonsils which develop from local accumulations of lymphocytes.
- 3rd pouch: This is not a typo. The inferior parathyroid and thymus develop and descend to their adult positions.
- 4th pouch: The superior parathyroid is derived from the 4th pouch!
- 5th and 6th pouches: rudimentary
Pharyngeal pouches are out pockets of the _____ in the head and neck.
foregut
What is the beginning site of the thyroid? What does this site lie between?
How may the thyroid maintain connection with its beginning site?
THE THYROID GLAND
- The site of the beginning of the thyroid is the foramen cecum which lies between the tuberculum impar and the copula.
- The thyroid may maintain a connection with the foramen cecum by thyroglossal duct. This duct normally atrophies and closes off before birth but can remain open in some people. A thyroglossal duct that fails to atrophy is called a persistent thyroglossal duct, a condition that may lead to the formation of a thyroglossal duct cyst.
T or F: The development of the face follows a general pattern of structures on either side meeting in the midline. Any midline defect must take these structures into account and most always includes neural crest cells.
True.
What is the name of the primitive mouth? What embryonic layer does it arise from?
What are the 5 primorida that the face develops from?
The primitive mouth begins as a depression of surface ectoderm called the stomodeum.
The face develops from 5 primordia:
1 unpaired frontonasal prominence
2 paired maxillary prominences
2 paired mandibular prominences
Describe the development of the nose. What embryological tissue layer is involved?
Nasal placodes derived from surface ectoderm develop on each side of the frontonasal prominence. Ridges called medial and lateral nasal prominences then develop around these placodes. The nasal placodes are then positioned in the floor of depressions known as nasal pits and later are opened to connect the nasal cavity with the outside world.
What are the 3 primordia that the palate develops from? Explain the development of the palate.
What is the incisive canal? What does it indicate?
The palate develops from 3 primordia:
1 - primary palate (anterior) from medial palatine process
2 - posterior part (secondary palate) from the lateral palatine processes
The primary palate is derived from the medial palatine process. The secondary palate develops as the lateral palatine processes grow medially. The incisive canal is located just behind the two medial incisor teeth in the maxilla and indicates the division between the parts of the palate. The posterior part of the palate remains soft tissue and ends at the uvula.
Explain the development of the lip.
What are the most common congenital malformations fo the face? What are issue in development are these almost always associated with?
The medial nasal prominences that help form the nose extend as soft tissue to form the upper lip and philtrum (indentation in upper lip). The medial prominences merge at the center line of the philtrum.
Cleft Lip and Cleft Palate are the most common and important of all congenital malformations of the face. These malformations may occur separately or in combination and result from multi factorial inheritance (i.e.. multiple factors, genetic and non-genetic). These midline defects almost always are associated with a problem with neural crest cell migration to embryonic facial primordia.
What does the oral part of the tongue develop from?
What branchial arch does the mensenchyme of this part of the tongue develop from?
What CN provides GSA innervation to the oral part of the tongue?
What CN provides SSA innervation to the oral part of the tongue?
The oral part of the tongue develops from 2 lateral lingual swellings and a median tongue bud called the tuberculum impar.
Mesenchyme in this part of the tongue is derived from the 1st pair of branchial arches.
Thus, the anterior 2/3 of the tongue receives general sensation from Cranial Nerve V (Trigeminal). Cranial nerve VII (Facial) supplies taste sensation (SSA) to the anterior 2/3 of the tongue.
The pharyngeal part of the tongue develops from structures behind the ____ ____ which is centered on the ____ ____.
What gives rise to the pharyngeal part of the tongue?
Mesenchyme in this part of the tongue is from what branchial arches?
What CN provides GSA innervation to this part of the tongue?
What CN provides SSA innervation to this part of the tongue?
The pharyngeal part of the tongue develops from structures behind the terminal sulcus which is centered on the foramen cecum.
Swellings from the copula (hypobranchial eminence) give rise to this part of the tongue.
Mesenchyme in this part of the tongue is from the 2nd 3rd and 4th branchial arches.
The posterior 1/3 of the tongue receives GSA and SSA innervation from the Glossopharyngeal nerve (CN IX).
