Unit 3 embryology

Question 1

what is the pharyngeal apparatus

Answer 1

bilateral growth of embryonic tissues in the ventrolateral region of the head
**5 pairs of pharyngeal arches, primarily driven by the migration and proliferation of neural crest cells

Question 2

anatomy of the pharyngeal arch

Answer 2

outside covering: ectoderm
Inside lining: endoderm (however arch 1 is covered mostly by ectoderm in the inside>oral ectoderm). The core of each arch is made of mesenchyme: neural crest, mesoderm (paraxial), nerve, blood vessel

Question 3

pharyngeal cleft/groove

Answer 3

separates pharyngeal arches from the outside (ectoderm lined)

Question 4

pharyngeal pouch

Answer 4

separates pharyngeal arches from the inside (endoderm lined)

Question 5

pharyngeal membrane

Answer 5

where ectoderm and endoderm come together at clefts/grooves

Question 6

neural crest derivatives from the maxillary prominence of pharyngeal arch 1 become

Answer 6

maxillary bone, zygomatic and squamous portions of the temporal bone

Question 7

neural crest derivatives from the mandibular prominence of pharyngeal arch 1 become

Answer 7

meckel’s cartilage, mandible, malleus, incus, anterior ligament of the malleus

Question 8

neural crest derivatives from pharyngeal arch 2 become

Answer 8

lesser cornu of hyoid, stylohyoid ligament, styloid process (styloid process of temporal bone, superior hyoid), stapes

Question 9

neural crest derivatives from pharyngeal arch 3 become

Answer 9

body and greater cornu of the hyoid bone (inferior hyoid)

Question 10

neural crest derivatives from pharyngeal arch 4/6 become

Answer 10

laryngeal cartilages

Question 11

paraxial mesoderm derivatives from pharyngeal arch 1 become

Answer 11

muscles of mastication: temporalis, masseter, mylohyoid, anterior belly of digastric, tensor tympani

Question 12

paraxial mesoderm derivatives from pharyngeal arch 2 become

Answer 12

muscles of facial expression: stylohyoid, post belly of the digastric

Question 13

paraxial mesoderm from pharyngeal arch 3 becomes

Answer 13

stylopharyngeus

Question 14

paraxial mesoderm from pharyngeal arch 4/6 becomes

Answer 14

pharyngeal constrictors, soft palate m., laryngeal m.

Question 15

pharyngeal arch 1 innervation (mandibular)

Answer 15

trigeminal nerve (V)

Question 16

pharyngeal arch 2 innervation (hyoid)

Answer 16

facial nerve (VII)

Question 17

pharyngeal arch 3 innervation

Answer 17

glossopharyngeal nerve (IX)

Question 18

pharyngeal arch 4/6 innervation

Answer 18

Vagal (X)

Question 19

pharyngeal pouch 1 gives rise to

Answer 19

Middle ear cavity, auditory tube: tubotympanic recess: tympanic cavity, mastoid antrum, auditory tube

Question 20

pharyngeal pouch 2 gives rise to

Answer 20

palatine tonsilar bed> induces lymphoid tissue invasion and together form the palatine tonsil

Question 21

pharyngeal pouch 3 gives rise to

Answer 21

ventral bud: thymus

dorsal bud: inferior parathyroid

Question 22

pharyngeal pouch 4 gives rise to

Answer 22

ventral bud: ultimopharyngeal body (parafollicular cells in thyroid that produce calcitonin)
dorsal bud: superior parathyroid

Question 23

pharyngeal groove 1

Answer 23

external acoustic meatus

Question 24

pharyngeal groove 2-4

Answer 24

coalesce into cervical sinus as arch 2 and 4 expand as folds toward each other and once the folds fuse, the sinus becomes the cervical vesicle.
-The neck line becomes
smooth and cervical vesicle degenerates over time

Question 25

cervical (branchial) cyst

Answer 25

persistent cervical vesicle, presents as asymptomatic swelling on lateral neck, anywhere along the anterior border of the SCM

Question 26

cervical (branchial) sinus

Answer 26

persistent cervial sinus or any cleft/pouch

Question 27

cervical (branchial) fistula

Answer 27

continuous duct between pharynx and neck surface

Question 28

development of the thyroid gland

Answer 28

- endoderm between pharyngeal arch 1 and 2 form a thyroid primordium and invaginate caudally. -As the thyroid primordium grows caudally, it is still open to the pharynx via the thyroglossal duct which opens into the pharyngeal space at foramen cecum (the thryoglossal duct degenerates, may become the pyramidal lobe of thyroid) - thyroid primordium: continues to grow caudally below the hyoid bone and takes residence anterior to the trachea, caudal to larynx

Question 29

what does the foramen cecum become

Answer 29

a remnant (indentation) between anterior and posterior tongue

Question 30

Clinical correlation: if the thryoglossal duct doesn't go away...

Answer 30

it can form a cyst: present at the level of the hyoid, may contain ectopic thryroid tissue.

Question 31

What is the median sulcus on the tongue derived from?

Answer 31

the line of fusion between the two lingual swellings

Question 32

What is the terminal sulcus on the tongue derived from?

Answer 32

the line of fusion between arch 1 and hypopharyngeal eminence

Question 33

The skeletal muscle of the tongue is derived from...

Answer 33

Occipital somites, which migrate into the tongue after the 5th week, pulling in the motor innervation of the hypoglossal nerve.

Question 34

Anterior 2/3 of the tongue is innervated by...

Answer 34

``` Somatosensory: mandibular of trigeminal Special sensory(taste): facial nerve ```

Question 35

Posterior 1/3 of the tongue is innervated by...

Answer 35

``` Somatosensory: glossopharyngeal and vagus Special sensory (taste): glossopharyngeal ```

Question 36

The muscles of the tongue are innervated by...

Answer 36

hypoglossal nerve

Question 37

the types of papillae on the tongue are...

Answer 37

filiform, fungiform, folliate, circumvallate (all but the filiform contain taste buds)

Question 38

Tastebuds

Answer 38

multicellular receptor organs in fungiform, folliate, and circumvallate papillae. functional in utero.

Question 39

week 4 of face formation

Answer 39

face begins as five facial primordia around the stomodeum: 1. Frontonasal prominence 2. Paired maxillary prominences (from pharyngeal arch 1) 3. Paired mandibular prominences (from pharyngeal arch 1)

Question 40

nose formation

Answer 40

``` nasal placodes (ectodermal thickening) form on frontonasal prominence. Underlying mesenchyme around nasal placodes proliferate, creating elevations around the placodes> The placodes become nasal pits>nasal sacs. Elevated regions around the nasal pit are called nasal prominences> divided into medial and lateral portions ```

Question 41

Week 6-10 of face formation

Answer 41

paired maxillary prominences grow and enlarge, pushing the nasal prominences toward midline of the face, and they fuse giving rise to the bridge of the nose.

Question 42

The Intermaxillary segment becomes

Answer 42

(ventral portion) the smooth portion of the upper lip, upper jaw with 4 incisors, and (dorsal region) the primary palate

Question 43

development of the nasal cavity

Answer 43

- Two nasal pits> nasal sacs - Nasal sacs fuse in the midline, forming a single nasal cavity separated from oral cavity by a thing oronasal membrane - oronasal membrane ruptures dorsal to primary palate> oral and nasal cavity becomes continuous - formation of secondary palate separates nasal cavity from oral cavity - nasal septum separates right and left nasal cavities

Question 44

What do nasal conchae develop from?

Answer 44

the lateral walls of the nasal cavities

Question 45

What does the olfactory epithelium develop from?

Answer 45

cranial ectoderm in the nasal cavity differentiate and specialize

Question 46

Development of the palate

Answer 46

palate: separates nasal cavity from oral cavity, preventing aspiration of food. Anatomical division: Hard palate: anterior bony portion majority of the palate. Soft palate: small fleshy posterior portion term, terminating at the uvula.

Question 47

Primary palate is derived from and gives rise to

Answer 47

derived from intermaxillary segment (fused medial nasal prominences) and gives rise to anterior, triangular portion of the hard palate.

Question 48

Secondary palate is derived from and gives rise to

Answer 48

derives from the fusion of palatine shelves that grow from the paired maxillary prominences. Gives rise to the majority of the hard palate and all of the soft palate.

Question 49

Development of the secondary palate

Answer 49

palatal processes form from the paired maxillary prominences internally, grow caudally on either side of the developing tongue. week 9 growth of the mandible drops the tongue, allowing the palatine shelves to swing up and fuse with the primary palate anteriorly and each other in the midline. (Formation is complete at 12 weeks!)

Question 50

cleft palate is the result of

Answer 50

- Primary cleft palate: failure of fusion of lateral palatine processes with median process. - Secondary cleft palate: lateral shelves of the maxillary processes fail to meet and fuse.

Question 51

Treacher Collins Syndrome

Answer 51

malformed or absent ossicles> conductive deafness, cleft palate sometimes. low set, malformed pinna

Question 52

DiGeorge Syndrome: defects in what embryonic germ layer and structures?

Answer 52

3rd, 4th pouch, neural crest, arch 1 and 2.

Question 53

tooth devo

Answer 53

The dental lamina forms in the epithelium of the mandible and maxilla. The ectodermal epithelium then invaginates to form dental buds - 10 per jaw (8 wks). The bud epithelium then invaginates, forming a cap around condensing dental papilla mesenchyme, which is derived from neural crest (10 wks). During the bell stage, neural crest mesenchyme cells become odontoblasts, destined to produce dentin, and outer epithelial/ectodermal cells differentiate as ameloblasts, which will produce enamel (3 months +) Ameloblasts are sloughed off when the teeth erupt postnatally. Baby/deciduous teeth erupt in a typical sequence.