M1.1 — 1 Embryology

Question 1

What part of the head is the viscerocranium?

Answer 1

facial bones

Question 2

What part of the head is the Neurocranium?

Answer 2

Skull vault + base

Question 3

what is the viscerocranium derived from embryologically? and what bones are involved? what type of ossification?

Answer 3

from neural crest cells from 1st and 2nd pharyngeal arch

1st pharyngeal arch - mandible, maxilla, zygoma, palatine, lacrimal, nasal, vomer - intramembranous ossification

2nd pharyngeal arch - styloid process, stapes, hyoid - endochondral ossification

Question 4

what is the neurocranium derived from embryologically? and what bones are involved? what type of ossification?

Answer 4

from neural crest cells and paraxial mesoderm

membranous (intramembranous ossification) - neural crest cells = frontal, squamous portion of temporal; paraxial mesoderm = intraparietal portion of occipital and parietal

cartilaginous (endochondral ossification) - neural crest cells = anterior sella turcica; paraxial mesoderm = posterior sella turcica, ethmoid, sphenoid, petrous portion of temporal, mastoid portion of occipital bone

Question 5

What is grastrulation?

Answer 5

2-3 weeks after fertilization the 2 layered Blastula becomes to the 3 layered gastrula

Question 6

What are the layers of the Gastrula?

Answer 6

endoderm, mesoderm, ectoderm

Question 7

What layer of the Gastrula becomes the spine?

Answer 7

Mesoderm -> 42 somite -> sclerotome -> vertebral column

Question 8

What does the Mesoderm become?

Answer 8

Paraxial - separates into 42 pairs of somites in craniocaudal direction. Differentiates into dermomyotome (muscle and dermis) and sclerotome (vertebral column)

Lateral - other organ systems (cardiac/pulmonary)

Intermediate areas (urogenital system)

Question 9

How does the sclerotome become the vertebral body?

Answer 9

sclerotome migrates to surround the notochord

the caudal cluster of one sclerotome fuses with the cranial cluster of the adjacent sclerotome to form the vertebral body

Question 10

How does the vertebral disc form?

Answer 10

sclerotome migrates to surround the notochord

a disc develops between each cluster. The notorchord becomes the nucleus pulposus. The sclerotome forms the annulus fibrosis

Question 11

How do the vertebral arches form?

Answer 11

cells from the sclerotome migrates around the neural tube and fuse dorsally forming the vertebra arch

Question 12

What layer of the gastrula forms the central nervous system?

Answer 12

ectoderm

surface = epidermis, hair
neural = neural tube + neural crest = brain ,spinal cord , peripheral nerves)

Question 13

What happens during weeks 2-8 of embryogenesis in the ectoderm?

Answer 13

The primitive streak appears from the thickened region of the ectoderm in the caudal to cranial direction. The ectoderm then invaginates as cells migrate to form the primitive node and primitive pit

Question 14

What is the primitive pit?

Answer 14

the depression at the center of the primitive node that is the opening of the notochordal canal

Question 15

what is neurulation? what does it form?

Answer 15

folding of the neural plate to form the neural tube which forms the CNS (brain from cranial 2/3rds and spinal cord from caudal 1/3rd)

Question 16

what do the neural crest cells form?

Answer 16

PNS - DRG and connective tissues of head and neck

Question 17

what forms the nucleus pulposus?

Answer 17

notochord

Question 18

What are the layers of the neural tube? what does each layer form?

Answer 18

ventricular layer, mantle layer, marginal layer

Question 19

What are the membranous layers covering the CNS? What are they derived from?

Answer 19

dura matter - derived from mesenchyme
arachnoid matter - derived from neural crest
pia matter - derived from neural crest

Question 20

What are the three primary brain vesicles?

Answer 20

brain vesicles of a 3-4 week old embryo =
prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain)

Question 21

What secondary brain vesicle(s) the procencephalon become? what does it’s secondary brain vesicle(s) become?

Answer 21

• Telencephalon (Cerebrum)
• Diencephalon (eye cup, thalamus, hypothalamus, epithalamus)

Question 22

What secondary brain vesicle(s) the mecencephalon become? what does it’s secondary brain vesicle(s) become?

Answer 22

Mecencephalon (midbrain)

Question 23

What secondary brain vesicle(s) the rhombencephalon become? what does it’s secondary brain vesicle(s) become?

Answer 23

• metencephalon (pons and cerebellum)
• myelencephalon (medulla oblongata)

Question 24

What are the 5 secondary brain vesicles?

Answer 24

brain vesicles of a 5 week old embryo =
telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon

Tel Di, Mes Met My