Block 3: Embryology

I. proliferative period

II. embryonic period

III. fetal period

List the periods of prenatal development.

proliferative period

Which period of prenatal development takes place from days 0-14 and includes fertilization, implantation, and formation of the bi-laminar (embryonic) disk?

embryonic period

Which period of prenatal development takes place on days 15-56 (weeks 2-8) and includes tissue differentiation, organogenesis, heart development, and development of face and oral structures?

embryonic period

Which period of prenatal development is the period of greatest sensitivity to teratogens (e.g. toxins, environmental factors, maternal factors, etc.)?

week 4 - week 7

During what time range within the embryonic period do the face and oral structures develop?

fetal period

Which period of prenatal development takes place from week 8 to birth and is when organs enlarge, differentiate, and begin to function?

in the ampulla of the oviduct (AKA Fallopian tube)

Where does fertilization occur?

on the posterior uterine wall

Where does implantation occur?

implantation

What is it called when the blastocyst embeds in the posterior uterine wall on day 6 or 7 of the proliferative period?

inner cell mass (= bi-laminar disk), outer cell mass, blastocyst cavity

What 3 obvious structures make up the blastocyst? (and which one is also called the bi-laminar disk?)

top: epiblast

bottom: hypoblast

What are the top and bottom pieces of bread of the bi-laminar disk?

embryonic

During what period of human development would a mother's offspring's prolonged exposure to higher concentrations of heavy metals such as lead most likely result in the MOST severe congenital defect?

c) development of 3 distinct germ layers

Gastrulation can be accurately described by what event?

a) attachment to the inner wall of the ampulla

b) development of a second cavity that replaces the first

c) development of 3 distinct germ layers

d) differentiation and migration of epiblast cells to form mesoderm

e) differentiation of the inner cell mass into 2 cell layers

paraxial/lateral plate mesoderm (dentin); definitive ectoderm (enamel)

What are the developmental origins of dentin and enamel, respectively?

c) hyoid bone (greater horn), stylopharyngeus muscle

*arch 3

List the derivative structures of the pharyngeal arch associated with deglutition.

a) arytenoid cartilages, laryngeal muscles

b) cricoid cartilage, cricothyroid muscle

c) hyoid bone (greater horn), stylopharyngeus muscle

d) incus, digastric muscle (anterior belly)

e) stapes, digastric muscle (posterior belly)

d) incus, digastric muscle (anterior belly)

*arch 1

List the derivative structures of the pharyngeal arch associated with mastication.

a) arytenoid cartilages, laryngeal muscles

b) cricoid cartilage, cricothyroid muscle

c) hyoid bone (greater horn), stylopharyngeus muscle

d) incus, digastric muscle (anterior belly)

e) stapes, digastric muscle (posterior belly)

e) stapes, digastric muscle (posterior belly)

*arch 2

List the derivative structures of the pharyngeal arch associated with facial expression.

a) arytenoid cartilages, laryngeal muscles

b) cricoid cartilage, cricothyroid muscle

c) hyoid bone (greater horn), stylopharyngeus muscle

d) incus, digastric muscle (anterior belly)

e) stapes, digastric muscle (posterior belly)

b) cricoid cartilage, cricothyroid muscle

List the derivative structures of the pharyngeal arch 4.

a) arytenoid cartilages, laryngeal muscles

b) cricoid cartilage, cricothyroid muscle

c) hyoid bone (greater horn), stylopharyngeus muscle

d) incus, digastric muscle (anterior belly)

e) stapes, digastric muscle (posterior belly)

a) arytenoid cartilages, laryngeal muscles

List the derivative structures of the pharyngeal arch 6.

a) arytenoid cartilages, laryngeal muscles

b) cricoid cartilage, cricothyroid muscle

c) hyoid bone (greater horn), stylopharyngeus muscle

d) incus, digastric muscle (anterior belly)

e) stapes, digastric muscle (posterior belly)

d) pharyngeal clefts 2-4

A lateral cervical cyst persists in an adult human as a vestigial remnant of which of the following embryological structures?

a) pharyngeal arch 1

b) pharyngeal arches 2-4

c) pharyngeal cleft 1

d) pharyngeal clefts 2-4

e) pharyngeal pouch 1

f) pharyngeal pouches 2-4

palatine tonsil

The second pharyngeal pouch gives rise to what derivative adult structure?

middle ear cavity and musculotubal canal

The first pharyngeal pouch gives rise to what derivative adult structure?

thymus gland and inferior parathyroid glands

The third pharyngeal pouch gives rise to what derivative adult structures?

superior parathyroid glands

The fourth pharyngeal pouch gives rise to what derivative adult structure?

ultimobranchial body

What does the fifth pharyngeal pouch give rise to?

a) mandible

Which of the following bones, at some point in its development, comprises both the neurocranium and the viscerocranium due to its derivation from cartilage and definitive connective tissue, respectively?

a) mandible

b) maxillary bone

c) nasal bone

d) premaxillary bone

e) zygomatic bone

d) medial nasal swellings

Which of the following structures give rise to the crest and tip of the nose, philtrum of the upper lip, labial tubercle, 4 incisor teeth, gingiva, and primary palate (premaxilla)?

a) frontonasal prominence

b) mandibular swellings

c) maxillary swellings

d) medial nasal swellings

e) lateral nasal swellings

a) frontonasal prominence

Which of the following structures give rise to the forehead, bridge of nose, and upper eyelid?

a) frontonasal prominence

b) mandibular swellings

c) maxillary swellings

d) medial nasal swellings

e) lateral nasal swellings

e) lateral nasal swellings

Which of the following structures give rise to the alae of the nose?

a) frontonasal prominence

b) mandibular swellings

c) maxillary swellings

d) medial nasal swellings

e) lateral nasal swellings

c) maxillary swellings

Which of the following structures give rise to the cheeks, lateral margins and angle of the upper lip, and lower eyelid?

a) frontonasal prominence

b) mandibular swellings

c) maxillary swellings

d) medial nasal swellings

e) lateral nasal swellings

b) mandibular swellings

Which of the following structures give rise to the lower part of the first arch and the lower lip?

a) frontonasal prominence

b) mandibular swellings

c) maxillary swellings

d) medial nasal swellings

e) lateral nasal swellings

a) intermaxillary segment

Which of the following structures is formed when the premaxilla merges with the maxillary arch component housing the 4 incisor teeth?

a) intermaxillary segment

b) maxilla

c) primary palate

d) secondary palate

e) soft palate

e) taste from root of tongue

During the formation of the tongue, the fourth pharyngeal arch contributes which of the following cranial nerve functions?

a) secretomotor function of the sublingual gland

b) sensation from anterior 2/3 of tongue

c) taste from anterior 2/3 of tongue

d) taste from posterior 1/3 of tongue

e) taste from root of tongue

b) sensation from anterior 2/3 of tongue

*CN V

During the formation of the tongue, the first pharyngeal arch contributes which of the following cranial nerve functions?

a) secretomotor function of the sublingual gland

b) sensation from anterior 2/3 of tongue

c) taste from anterior 2/3 of tongue

d) taste from posterior 1/3 of tongue

e) taste from root of tongue

c) taste from anterior 2/3 of tongue

*CN VII

During the formation of the tongue, the second pharyngeal arch contributes which of the following cranial nerve functions?

a) secretomotor function of the sublingual gland

b) sensation from anterior 2/3 of tongue

c) taste from anterior 2/3 of tongue

d) taste from posterior 1/3 of tongue

e) taste from root of tongue

d) taste from posterior 1/3 of tongue

*CN IX

During the formation of the tongue, the third pharyngeal arch contributes which of the following cranial nerve functions?

a) secretomotor function of the sublingual gland

b) sensation from anterior 2/3 of tongue

c) taste from anterior 2/3 of tongue

d) taste from posterior 1/3 of tongue

e) taste from root of tongue

c) thyroid gland

Which of the following structures' origin begins at the foramen cecum of the tongue?

a) ultimobranchial body

b) superior parathyroid gland

c) thyroid gland

d) thymus gland

e) inferior parathyroid gland

morula

What's another name for the 16 cell stage (on day 4 of the proliferative period)?

24 hours into development (proliferative period)

When does the zygote become an embryo?

amniotic cavity

What is the name of the second cavity that forms, in addition to the blastocyst cavity, on day 8 of human development?

cavity on top: amniotic cavity

top piece of bread: definitive ectoderm

meat: 3 divisions of mesoderm

bottom piece of bread: definitive endoderm

cavity on bottom: definitive yolk sac

When gastrulation is complete, you have...

cavity on top: ___________

top piece of bread: _________

meat: _________

bottom piece of bread: _________

cavity on bottom: __________

ectoderm

What is the developmental origin of cutaneous glands (salivary glands and sweat glands)?

ectoderm

What is the developmental origin of sensory epithelium of the eye, ear, and nose?

ectoderm

What is the developmental origin of the epithelium of sinuses, oral cavity, and nasal cavity?

ectoderm

What is the developmental origin of intra-oral glands?

mesoderm

What is the developmental origin of pulp?

mesoderm

What is the developmental origin of cementum?

mesoderm

What is the developmental origin of the PDL?

endoderm

What is the developmental origin of the parenchyma of thyroid and parathyroid glands?

endoderm

What is the developmental origin of the epithelial lining of the tympanic cavity (middle ear) and auditory (Eustachian) tube?

arches

Pharyngeal ________ contribute to face soft tissues, muscles of mastication, nasal cavity and septum, primary and secondary palates, and the tongue.

definitive endoderm; definitive ectoderm

Each pharyngeal arch is lined on the inside by _________ and on the outside by _________.

mesenchyme

Each pharyngeal arch contains a ________ core.

Neural crest

________ cells migrate into the connective tissue in the mesenchyme core of a pharyngeal arch and differentiate.

cartilage, bone, and dentin

In the head region, what structures can neural crest cells differentiate into?

neural crest cells

What cells contribute to teeth and ligaments of the face?

-cartilage skeletal element (derived from neural crest cells)

-skeletal muscle

-cranial nerve

-aortic arch artery

What 4 things does each pharyngeal arch contain?

arch 1

The function of which pharyngeal arch is mastication?

arch 2

The function of which pharyngeal arch is facial expression?

arch 3

The function of which pharyngeal arch is deglutition (swallowing)?

arches 4 and 6

The function of which pharyngeal arch is vocalization?

arch 5

Which pharyngeal arch regresses and disappears and has no derivatives?

incus (maxillary swelling) and malleus (mandibular swelling)

What 2 bones are derived from pharyngeal arch 1?

stapes, styloid process, lesser horn of hyoid

What 3 bones/bony structures are derived from pharyngeal arch 2?

arch 6 (+ arytenoid cartilage)

Cuneiform and corniculate cartilages are derived from which pharyngeal arch?

arch 4 (+ cricoid cartilage)

Thyroid cartilage is derived from which pharyngeal arch?

arch 1

The sphenomandibular ligament, muscles of mastication, mylohyoid, tensor tympani muscle, and tensor veli palatini muscle are derived from which pharyngeal arch?

arch 2

The stapedius muscle, stylohyoid muscle, and 5 facial nerve branches are derived from which pharyngeal arch?

pharyngeal clefts

externally located separations between pharyngeal arches

clefts 2, 3, and 4

Which pharyngeal clefts normally are overgrown to form an ectodermally lined lateral cervical sinus, which normally disappears, and the remnants form a cyst?

pharyngeal pouches

internally located endodermally lined invaginations

chondrocranium

the skull base, which develops by endochondral ossification

calvarium

the cranial vault, which develops by intramembranous ossification

basioccipital cartilage

Which cartilage of the skull base/face is useful in orthodontic treatment?

mesenchyme

Bones of the calvarium develop directly from ____________.

viscerocranium

Bones of the facial skeleton (___________) develop directly from connective tissue.

medial nasal swellings

The intermaxillary segment is formed by the fusion of what swellings?

primary and secondary palates

Failure of what 2 things to fuse results in a cleft palate?

primary palate

Anterior part of final palate derived from intermaxillary segment during prenatal development

secondary palate

posterior part of final palate formed by fusion of two palatal shelves

shelves

During secondary palate formation, maxillary swellings develop palatine _________.

maxillary

During secondary palate formation, ________ swellings develop palatine shelves.

parallel; 90; midline

Palatine shelves form ______ to the tongue and rotate _______ degrees toward the ________.

incisive papilla

To what landmark does the primary palate extend posteriorly in the midline?

soft palate

Posteriorly, the secondary palate fuses with the soft tissue to form the _________, including the uvula.

midline cleft palate

Failure of the palatine shelves to fuse in the midline results in a ________ ________ ________.

CN V (trigeminal) — general sensation from anterior 2/3

Which cranial nerve carries general sensation from the anterior two-thirds of the tongue?

trigeminal nerve (CN V)

Which cranial nerve is associated with the first pharyngeal arch?

facial nerve (CN VII)

Which cranial nerve is associated with the second pharyngeal arch?

glossopharyngeal nerve

Which cranial nerve is associated with the third pharyngeal arch?

CN X (vagus), superior laryngeal branch

Which cranial nerve is associated with pharyngeal arch 4?

e) thymus and parathyroid glands

A child is born with a cleft palate and diagnosed with DiGeorge's Sequence, a syndrome affecting the 3rd and 4th pharyngeal pouches. It results in the partial or total absence of which of the following structures?

a) external auditory meatus and pinna

b) neural crest cells

c) palatine tonsils

d) parafollicular cells of thyroid gland

e) thymus and parathyroid glands

C: creates a trilaminar embryonic disk composed of definitive ectoderm, mesoderm and definitive endoderm.

The process of gastrulation:

A: begins with the appearance of the primitive streak in the hypoblast layer of the embryo.

B: contributes to the formation of the primary yolk sac at day 13

C: creates a trilaminar embryonic disk composed of definitive ectoderm, mesoderm and definitive endoderm.

D: ends with the appearance of the notochordal process and the prechordal plate on day 54

E: is under the influence of the FSH surge from the basophil gonadotrophs

E: styloid process of the temporal bone

The second pharyngeal arch cartilage, known as Reichert's cartilage, forms the:

A: cricoid cartilage

B: hyoid bone body

C: lingula of mandible

D: malleus

E: styloid process of the temporal bone

C: receives sensory and taste nerve fibers form CNs V, VII, and IX.

The tongue:

A: tip and body arise from mesenchymal tissue in pharyngeal arch II

B: has taste buds in the posterior region that arise from ectodermal tissue in pharyngeal arch I

C: receives sensory and taste nerve fibers form CNs V, VII, and IX.

D: has an epithelium that contributes to the development and proliferation of the thymus gland.

E: has a masticatory mucosa on its ventral surface.

c) posterior to the terminal sulcus, arises from cells associated with pharyngeal arch III

The tongue:

a) has taste buds on the anterior one half that develop from the second pharyngeal cleft

b) is characterized by a specialized mucosa, which contributes to the development and proliferation of the thymus

c) posterior to the terminal sulcus, arises from cells associated with pharyngeal arch III

d) root arises from neural crest tissue in the ultimobranchial body

e) tip and body epithelium arise from ectomesenchymal tissue in pharyngeal arch IV

E: tensor veli palatini muscle and pharyngeal arch I

Which muscle: pharyngeal arch pairing is correct?

A: anterior digastric muscle and pharyngeal arch III

B: lateral pterygoid muscle and pharyngeal arch II

C: posterior digastric muscle and pharyngeal arch IV

D: stylopharyngeus muscle and pharyngeal arch V

E: tensor veil palatini muscle and pharyngeal arch I

E: the intermaxillary segment contains components listed in A, B and C.

Which of the following best describes the components of the intermaxillary segment?

A: a bony, palatal component that develops into the triangular-shaped, primary palate (premaxilla).

B: a maxillary arch component that houses the 4 incisor teeth, associated alveolar bone, periodontal ligament (PDL) and gingiva.

C: a soft tissue, labial component that gives rise to the philtrum and labial tubercle of the upper lip.

D: the Tessier cleft, a point of fusion between the primary and secondary palates.

E: the intermaxillary segment contains components listed in A, B and C.

D: The viscerocranium develops from neural crest cells via the process of intramembranous ossification.

Which statement accurately describes the formation of the neurocranium or the face?

A: Flat bones of the calvarium are joined by fibrous joints classified as diarthrosis, commonly referred to as synovial joints.

B: Ossification of the premaxillary cartilage gives rise to the primary palate (premaxilla).

C: The chondrocranium forms from undifferentiated mesenchymal cells in the intermediate mesoderm.

D: The viscerocranium develops from neural crest cells via the process of intramembranous ossification.

A: contains involuntary cardiac muscle developed from somitomeres and somites

Which statement completion is NOT correct? Each pharyngeal arch:

A: contains involuntary cardiac muscle developed from somitomeres and somites

B: is supplied by nerve fibers associated with a specific cranial nerve

C: has a skeletal element derived from neural crest cells

D: receives blood via a specific aortic arch artery