Pharyngeal, Ob Final Prep

Front 1

What apparatus is seen during week 4 of development?

Back 1

• bilateral apparatus • also called branchial apparatus • consists of arches, pouches, grooves and membranes

Front 2

What are the 4 pairs of temporary embryonic structures that form the pharyngeal apparatus?

Back 2

1. pharyngeal Arches – 6 (the 5th is rudimentary- no derivatives) Arches are defined by clefts and pouches that partially separate
them internally and externally
2. pharyngeal pouches –4 well defined (5th absent or incorporated) – internal aspect, formed by outpocketings of the endoderm
3. pharyngeal grooves (clefts) –external aspect (ectoderm- epidermis)
4. pharyngeal membranes

Front 3

What does each arch bein as?
What cells migrate into the arches?

Back 3

•
• •
each arch begins as a thin condensation of mesoderm at the most cranial portion of the pharyngeal endoderm
neural crest cells migrate into the arches myotomes, cranial nerves are also migrating into the arches

Front 4

Where does skeletal muscle form, and what calls are involved in this process?

Back 4

Skeletal muscle forms in the arches from invading myotome cells from the paraxial mesoderm (somitomeres and occipital somites)

Front 5

1st Pharyngeal Arch
(also called the manibular arch) consists of 2 prominences:

Back 5

1. maxillary- dorsal, beneath the eye
2. mandibular – ventral
• the mandibular arch is the major contribution to the formation of the face

Front 6

Each prominence gives rise to a named cartilage:

Back 6

• cartilage in the maxillary prominence completely regresses
• cartilage in the mandibular arch largely regresses- but leaves some adult structures
• formation of the cartilages is essential for creating enough initial mass and for the correct relationship of arch prominences to one another

Front 7

1. Meckel’s cartilage gives rise to:
2. The perichondrium of Meckel’s cartilage forms:

Back 7

1. • incus • malleus

Front 8

Where is the sphenomandibular ligament and what's the function?

Back 8

Location: Spine of the sphenoid bone to the lingula of the manible
Function: provides the primary passive support for the mandible (muscles of mastication are the main active support of the mandible)

Front 9

Intramembranous ossification occurs in the maxillary prominence and forms the:

Back 9

1. squamous portions of the temporal bone
2. maxillary bone 3. zygomatic bone 4. palantine bone

Front 10

Intramembranous ossification occurs in the mandibular prominence and forms the:

Back 10

Mandible

Front 11

Muscle components of the 1st pharyngeal arch include:
Muscles of mastication:

Back 11

1. temporalis 2. masseter 3. lateral pterygoid 4. medial pterygoid
• tensor veli palatini (soft palate)
• tensor tympani
• anterior belly of the digastric
• mylohyoid

Front 12

Describe the attachments and actions of the temporalis, masseter, medial and lateral pterygoids

Back 12

1. Temporalis- temporal fossa to coronoid process and ramus of mandible- elevates and retracts
2. masseter-zygomatic bone and arch to angle and ramus of the mandible- elevates and protrudes
3. medial pterygoid- lateral pteryoid plate and maxilla to mandibular ramus- elevates and protrudes
4. ateral pterygoid- sphenoid bone and lateral pterygoid plate to joint capsule and articular disc of the TMJ and condyle of the mandible- depresses and protracts the mandible (bilateral), swings jaw to contralateral side (unilateral)

Front 13

What's the nerve of the 1st pharyngeal arch?

Back 13

• mandibular branch of the trigeminal nerve (CNV) supplies the muscles of the 1st pharyngeal arch.
• mesenchyme form the 1st arch gives rise to the dermis of the face and sensory supply to the skin of the face is through ophthalmic, maxillary, mandibular branches

Front 14

What does 2nd pharyngeal arch form?

Back 14

• named the hyoid arch
• develops in a line from the developing ear (dorsal) to the (ventral) neck
• arch II bone and cartilage are derived from an original cartilage called Reichert’s cartilage
• all bones are formed by endochondral ossification

Front 15

The cartilage (Reichert’s) of the 2nd arch leaves the following adult derivatives:

Back 15

• stapes • styloid process • stylohyoid ligament • lesser horn of the hyoid bone • upper body of the hyoid bone

Front 16

Where's the hyoid bone and what's the function?

Back 16

•does not articulate with any other bone •suspended from the styloid process by
the stylohyoid ligament •firmly bound to the thyroid cartilage by the
thyrohyoid membrane
Function: • attachment for anterior neck muscles • assists in chewing, swallowing, vocalization • assists in maintaining an open airway

Front 17

What's the difference of hyoid bone in younger and older people?

Back 17

• In young people, the greater horns are usually united to the body by (fibro) cartilage
• In older people the horns are united by bone

Front 18

Injury to the nerve of the second pharyngeal arch distal to its point of exit in the skull could result in:
A. Hyperacusis B. Inability to elevate the mandible C. Inability to open the eyes D. Inability to close the eyes E. All of the above

Back 18

D. Inability to close eyes

Nerve to 2nd pharyngeal is facial nerve.

Front 19

Where's the stylomastoid foramen?

Back 19

-lies posterior to the base of the styloid process -transmits the facial nerve (CN VII)

Front 20

Name the muscles of the 2nd pharyngeal arch

Back 20

• muscles of facial expression
• stapedius
• stylohyoid
• posterior belly of the digastric

Front 21

3rd pharyngeal arch
cartilage
muscle
nerve

Back 21

Cartilage:
• gives rise to the remaining portions of the hyoid bone (greater horn and lower body)
Muscle:
• Stylopharyngeus
Nerve:
• CN IX (glossopharyngeal)

Front 22

What are some characteristics of the 4th and 6th pharyngeal arch skeletons?

Back 22

• never as large as the other arches
• merge together
• arch 5, if ever present, has regressed.
• form the laryngeal cartilages (except the epiglottis)
• all formed from lateral plate mesoderm
• ossification does not occur in these cartilages

Front 23

Name the 3 pairs and unpaired cartilages of the larynx

Back 23

Three unpaired cartilages:
1. thyroid 2. epiglottis 3. cricoid
Three paired cartilages: 1. arytenoid 2. corniculate 3. cuneiform

Front 24

Muscles of arches 4 and 6
1. Soft palate
2. Pharynx
3. Intrinsic muscles of larynx

Back 24

Muscles of the soft palate: • levator veli palatini • palatoglossus • palatopharyngeus
• uvulae
Muscles of the pharyx:
• superior, middle and inferior constrictor muscles
• palatopharyngeus • salpingopharyneus
Intrinsic muscles of the larynx: • cricothyroid (external laryngeal nerve) • thyroarytenoid • posterior crico-arytenoid • lateral cricoarytenoid • transverse and oblique arytenoids • Vocalis

Front 25

What's the nerve component of the arch 4 and 6?

Back 25

Vagus nerve

Front 26

What's a vestige and a branchial vestige?

Back 26

Vestige-
• a degenerate structure
• a remnant or trace of a rudimentary structure in the embryo
Branchial vestige-
• remnant of pharyngeal cartilages that do not disappear
• can be cartilage or bone
• usually right below the skin at the inferior portion sternocleidomastoid

Front 27

1. What lines the internal aspects of the pharyneal arches?
2. What are the pouches?
3. Which pouches are paired structures?

Back 27

• endoderm of the pharynx lines the internal aspects of the pharyngeal arches
• pouches are evaginations or diverticulum of the endoderm lining the pharyngeal foregut
• pouches (1,2,3 and 4) are paired structures

Front 28

1. What does the first pharyngeal pouch expand to form?
2. What does the distal end of it wide to form?
3. How about the proximal part?

Back 28

First Pharyngeal Pouch
• the first pharyngeal pouch expands to form the tubotympanic recess.
• the distal end widens to form the tympanic (middle ear) cavity and mastoid antrum
• the proximal part remains narrow and forms the auditory tube.

Front 29

For the 2nd pharyneal pouch..
1. What does the mesoderm tissue invade the bud in order to form?
2. What does the tissue differentiate into?
3. What is the covering of the palatine?

Back 29

• epithelial lining proliferates and forms buds that extend into the mesenchyme.
• mesodermal tissue invades the buds forming the palatine tonsil.
• the tissue differentiates into lymphatic tissue
• epithelium covering palatine tonsils is formed by the 2nd pouch

Tonsil itself is not derived from 2nd pouch.

Front 30

1. What 2 wings does the 3rd pharyngeal pouch form?
2. What does each wing form?

Back 30

The 3rd pouch develops a dorsal and ventral wing:
• dorsal wing = inferior parathyroid gland (the glandular epithelial cells- chief cells that secrete PTH)
• ventral wing = stroma of the

Front 31

1. What begins to migrate down, and what does it pull with it?
2. What 2 strcutres fuse?

Back 31

• thymus and the inferior parathyroid gland loose their connection with the pharyngeal wall
• migrate medially and caudally.
• right and left thymus fuse
• inferior parathyroids position on the posterior thyroid

Front 32

1. What do the 2 wings of the 4th pharyngeal pouch form?

Back 32

• dorsal wings give rise to superior
parathyroid glands
• caudal migration places them on the superior, posterior thyroid gland
• gives rise to the ultimobranchial body.
• the ultimobranchial body is incorporated into the thyroid gland
• differentiate into parafollicular cells of the thyroid gland
• neural crest cell derived

Front 33

Describe the ectopic parathyroid glands

Back 33

• can be variable in number and location
• more common for the inferior parathyroid glands to be out of position
• most often seen near the bifurcation of the common carotid or in the final position of the thymus

Front 34

Thymus review
1. Where is it located?
2. When does peak development occur?
3. Describe the stroma and parenchyma of the thymus
4. What is it's function?

Back 34

• located in mediastinum
• peak development is during youth (undergoes involution beginning at puberty)
• Stroma : endoderm derived epithelial reticular cells
• Parenchyma: immature T- cells that migrate from the bone marrow to the thymus
• Function: Primary lymphoid organ....T-cell maturation
• Diagnostic feature: Hassall’s corpuscles in the medulla

Front 35

Week 5
1. Where do clefts and grooves appear?
2. What are they derived from?

Back 35

• clefts or grooves appear on the external surface of the embryo
• the clefts are ectoderm derived (epithelium)

Front 36

What is the only definitive structure to arise from the 1st pharyngeal cleft

Back 36

• only definitive structure arise from the first pharyngeal cleft
• cleft 1 = epithelial lining of the outer ear canal (external
auditory meatus)

Front 37

1. What arch grows over the clefts caudally? What does this overgrowth leave?

Back 37

• ectoderm of clefts 2,3,4 do not form mature structures
• arch 2 obliterates the clefts by growing over them (caudally) as the muscles of facial expression are developing
• The overgrowth leaves an ectoderm lined cavity that eventually regresses and disappears
• small cavities can persist forming cysts or sinuses (larger cavity)

Front 38

Where do branchial cysts or fistulas form?

Back 38

• fistula: abnormal passage between hollow organ and the exterior body or another organ
• lateral, often found along the anterior border of the sternocleidomastoid
• may not appear until later in childhood when the epithelial lining forms fluid and debris in the sinus

Front 39

What does the pharyngeal membranes give rise to?

Back 39

• appear where the epithelia of the cleft and pouches meet each other.
• pharyngeal membrane 1 = tympanic membrane
• the other membranes degenerate and leave no adult derivatives

Front 40

Name the derivatives of the following:
1. Pouch and cleft 1 (and membrane)
2. Pouch 2
3. Pouch (and cleft) 3 (ventral)
4. Pouch 3 (dorsal)
5. Pouch 4 (dorsal)
6. Pouch 4 (ventral)

Back 40

Pouch and cleft 1 (and membrane): epithelial lining of middle and outer ear canals and tympanic membrane

Pouch 2: epithelial lining of palatine tonsil
Pouch (and cleft?)3: ventral:epithelial components of thymus
Pouch 3 dorsal: glandular cells of inferior PTG.

Pouch 4 dorsal: glandular cells of superior PTG

Pouch 4 ventral: parafollicular cells

Front 41

What is one birth defect that involves the pharyngeal arches?

Back 41

• may be from insufficient migration of neural crest cells during the 3rd and 4th week of development.
• neural crest cells are vulnerable and can be destroyed by teratogens (retinoic acid and alcohol)
• amount of neural crest cells and ability to migrate is critical for normal development

Front 42

What is first arch syndrome?

Back 42

• abnormal development of of the first arch
• results from insufficient migration of neural crest cells
• usually occurs during the fourth week of
development
Two main manifestions;
1. Treacher Collins syndrome
2. Robin sequence

Front 43

Describe Treacher Collins syndrome

Back 43

• malar hypoplasia
• mandibular hypoplasia
• eye, ear malformations
• autosomal dominant trait- but has been replicated in labs with teratogens (retinoic acid)

Front 44

Describe Robin syndrome

Back 44

• alters first arch structures-mandible is most severely affected
• may have a genetic and/or environmental basis triad complex:
• primary defect: poor growth of the mandible
which results in:
• high, posteriorly placed tongue
• prevents the palatine shelves from fusing- cleft palate

•may also result from deficiencies of amniotic fluid resulting in poor positioning of the chin

Front 45

Describe DiGeorge syndrome

Back 45

Primary cause: failure of the third and fourth pharyngeal pouch to differentiate and due to poor neural crest cell migration
• infants are born without (or hypoplasia) thymus (neural crest contributes to connective tissue of thymus)
• absence of parathyroid glands
• cardiovascular defects
• facial anomalies including cleft palate
• severity and anomalies vary
• poor prognosis
• significant link to teratogens (especially retinoids and alcohol) during the third week of development

Front 46

1. When does the tongue appear?
2. What gives rise to the swellings?
3. What do the swellings give rise to?

Back 46

• appears during week 4 of development
• proliferation of swellings of endoderm and underlying arch mesenchyme of the first 4 pharyngeal arches gives rise to swellings
• swellings form the mucous membrane (epithelium) of the tongue

Front 47

What part of the tongue does arch 1 form?
2. Where does the median swelling appear?
3. Lateral swellings?

Back 47

• median swelling appears rostral to the foramen cecum (median tongue bud, tuberculum impar)
• two lateral swellings develop on each side of the median tongue bud
• lateral swellings overgrow the median swelling
• lateral swellings merge to form the anterior 2/3 of the tongue

Front 48

1. Name the 2 elelvations that develop caudal to the foramen cecum? (part of posterior 1/3 of tongue)

Back 48

two elevations develop caudal to the foramen cecum: 1. copula (blue)- arch II endoderm and mesenchyme
2. hypobranchial eminences- endoderm and mesenchyme of arch III and IV (yellow and green)

Front 49

What arch tissue overgrows another arch tissue? What is the posterior part of the tongue only formed by?

What occurs at the terminal sulcus?

Back 49

• tissue of the arch III overgrows arch II
• posterior part of the tongue is only formed by tissue from arch III and IV
• anterior and posterior tongue fuse at the terminal sulcus

Front 50

Where can we find all the named papilla?

Back 50

All found on the body of the tongue, lining the terminal sulcus.

Front 51

1. When does the lingual papillae form?
2. When do taste buds develop, and how?

Back 51

• develop at the end of the embryonic period and the beginning of the fetal period
• taste buds develop during weeks 11-13 by interaction between the epithelial cells of the tongue and the sensory afferent nerve they are associated with

Front 52

What do muscles of the tongue arise from?

Back 52

muscles of the tongue arise from the myotomes of the occipital somites that migrate forward, taking the nerve with them.

Note: muscles of tongue are not from arch structures

Front 53

What tongue muscle is the only one not innervated by CNXII?

Back 53

palatoglossus. This is innervated by CNX

Front 54

Describe the sensory innvervation of the tongue.

Back 54

Anterior 2/3:
General sensation- lingual of CN V
Special sensation (taste)- chorda tympani CN VII
Posterior 1/3
General sensation –
glossopharyngeal and vagus (small portion)
Special sensation (taste)- glossopharyngeal

Front 55

What is ankyloglossia?

Back 55

• frenulum is short
• extends to the tip of the tongue
• also called “tongue-tie”
• very low incidence
• no intervention required, usually stretches after birth
• frenulum- fold of mucous membrane attaching inferior surface of tongue to floor of mouth
• ankylosis- rigidity, stiffening or immobility of a joint

Front 56

1. When does the thyroid gland develop?
2. What gives rise to this?
3. What does the thyroid diverticulum form?

Back 56

• development begins day 24
• thickening of endoderm on the floor of the upper pharynx (between the 1st and second arch)
• the thyroid diverticulum forms the glandular cells that produce/secrete thyroid hormone

Front 57

1. As the embryo and tongue grow, the thryoid gland descends in front of _______ ventral to _____ and _______

Back 57

pharyngeal gut; ventral to hyoid and larynx

Front 58

1. The thyroid gland remains attached to the tongue by the _____
2. This degenerates and disappears. The proximal portion of this persists as a pit in the tongue __________

Back 58

• the thyroid gland remains attached to the tongue by the
thyroglossal duct
• the duct will degenerate and disappear • the proximal portion of the duct persists as a pit in the tongue-
the foramen cecum.
• the thyroid gland reaches its final position in front of the trachea during the seventh week of development

Front 59

1. By week 10, what appears and what fills in the follicular cells?
2. When does thyroid hormone production begin?

Back 59

• the solid thyroid primordium eventually breaks up into cords of epithelial cells invaded by vascular networks
• by week 10, a lumen appears between the cells and by week 11 colloid fills the lumen
• synthesis of thyroid hormones begins by week 12

Front 60

What is a thyroglossal cyst?

Back 60

• • •
the thyroglossal duct should degenerate by week 7 of development a thyroglossal cyst is a remnant of the thyroglossal duct may be found at any point of the migration path- but always midline can form a sinus (large cavity) or fistula (open channel)

Front 61

Name the 2 parts of the skull..

Back 61

• neurocranium – forms a
protective case around the brain (cranial vault and cranial base)
• viscerocranium- forms the skeleton of the face

Front 62

What are the bone and cartilages of the skull derived from?

Back 62

cranial somitomeres
occipital somites
lateral plate mesoderm
Neural crest cells

Front 63

Why does the skull develop the way it does?

Back 63

Allows for adjustment to birthing canal and to allow for grwoth of braind during prenatal and postnatal development

Front 64

1. What are 2 parts that come from neurocrenuam?

Back 64

1. Membranous part - cranial vault
cartilaginous part - cranial base

largely derived from tissues cranial to arches

Front 65

What is the viscerocranium largely forrmed from?

Back 65

derived from tissues of pharyngeal arches

-has membranous and cartilaginous parts

Front 66

1. What is membranous neurocranium derived from?
2. What does the mesenchyme undero to form this, and what bones do this form?
3. What radiates from the primary centers of ossification toward periphery?

Back 66

• derived from NCC’s
• mesenchyme undergoes
intramembranous ossification to form flat bones with needle- like bone spicules
• spicules radiate from the primary centers of ossification toward periphery
• includes frontal, parietal bones and part of the occipital bone

Front 67

1. When does the frontal bone develop and how?
2. What seperates the right and left frontal bones?
3. When does the suture fuse?

Back 67

• the frontal bone develops from two membranous ossification centers during the 7th week of development
• at birth, right and left frontal bones are present, separated by a midline inter-frontal suture
• the suture begins to fuse during the first year of life
• the suture is usually completely obliterated by age 6

Front 68

1. What is molding?
2. What are fontanelles and what are the largest ones?

Back 68

• permit the skull to expand as the brain grows
• deform/adapt/overlap during the birthing process (molding)
• At points where more than two bones meet, sutures are wide and called fontanelles
• most prominent is anterior fontanelle (2 parietal, 2 frontal bones meet)

Front 69

1. What is the small facial region due to?
2. What part of the skull grows rapdibly in the first 2 years, and when does this growth change?
3. What does rapid growth of face and jaws coincide with?

Back 69

The small facial region is due to the:
• small size of the jaws
• absence of paranasal sinuses
• underdevelopment of the facial bones
The calvaria grows rapidly within the first 2 years, then gradually until approximately age 19 or 20
Rapid growth of the face and jaws coincide with the eruption of the primary and secondary teeth.

Front 70

What are 3 components of the cartilaginous neurocranium?

Back 70

1. neural crest cell derived
mesenchyme
2. cranial somitomeres
3. occipital sclerotomes

area around the oropharyngeal membrane is a precordal plate. Between the epiblast and hypoblast, some mesenchyme invaded the area, and gave rise to some of the cartilages in the skull development.

Front 71

Name 4 things that the cartilage gives rise to..

Back 71

-base of occipital bone
-sphenoid
-ethmoid
-petrous and mastoid portions of temporal bone

Front 72

When is the bse of hte skull formed and how do they form?

Back 72

•the base of the skull is formed when the cartilages fuse and ossify by endochondral ossification (leaving foramen for cranial nerves, the spinal cord and vessels to exit)

Front 73

What pharyngeal arches give rise to teh viscerocranium?

Back 73

• formed mainly from the first two pharyngeal arches
• the mesenchyme for the formation of the bones of the face is neural crest cell derived.

Front 74

In which prominence of the face does intramembranous ossificiation give rise to?

Name all the components that it gives rise to..

Back 74

Intramembranous ossification occurs in the maxillary prominence and gives rise to:
• squamous temporal bone (becomes part of the neurocranium)
• maxillary bone
• zygomatic bone
• palatine bone, nasal bone, vomer and lacrimal bone
Intramembranous ossification of mandibular prominence gives rise to the mandible

Front 75

What components are part of the cartilaginous viscerocranium?

Back 75

Thyroid cartilage
hyoid
malleus, incus, stapes

Front 76

What is acrania?

Back 76

failure of rostral/cranel end of neural tube to close during 3rd week of development or day 25 of development.
-calvaria is absent