embryology

Question 1

what forms somites and what forms from it

Answer 1

paraxial mesoderm

forms axial skeleton and cranial head skeleton and muscles

Question 2

pharyngeal/branchial branches form what? and where?

Answer 2

they are series of arches that develop to form gill-like structures - form face and neck

Question 3

how many branchial arches?

Answer 3

5
(1,2,3,4,6)
number 5 disappears

Question 4

structure of the branchial branches?

Answer 4

ectoderm lines outside - form clefts between arches

mesoderm in middle

endoderm in inside - pouches formed in between arches

Question 5

nerves that arise from 1st arch?

Answer 5

mandibular branch of trigeminal V3

Question 6

nerve that arises from 2nd arch?

Answer 6

facial nerve

Question 7

nerve that arises from 3rd arch?

Answer 7

glossopharyngeal nerve

Question 8

nerve that arises from 4th arch?

Answer 8

superior laryngeal branch = branch of vagus

Question 9

6th arch nerve that arises?

Answer 9

recurrent laryngeal branch of vagus nerve

Question 10

what else forms from 1st arch?

Answer 10

jaw line -along mandible

Question 11

what else forms from 2nd arch?

Answer 11

upper part of hyoid bone

Question 12

what else forms from 3rd arch?

Answer 12

thyroid cartilage

Question 13

what else forms from 4th arch?

Answer 13

cricoid cartilage

Question 14

what does face develop from?

Answer 14

from 5 processes -

1 frontonasal
2 maxillary
2 mandibular

Question 15

stages of face development?

Answer 15

1. 2 mandibular fuse
2. thickening of frontonasal process pushing inwards and invaginated to form nasal pits
3. frontonasal process divide into lateral nasal process and medial nasal processes
4. medial nasal processes fuse at midline
5. and grow down and laterally to from philtre

Question 16

philtrum for?

Answer 16

separates nasal pit from mouth and forms primary plate that separates oral and nasal cavity

Question 17

how does plate form to separate nasal and oral cavity?

Answer 17

1. philtrum grows a bit inwards

2. maxillary process - from which two palatine shelves grow inwards and meet midline to form secondary plate

Question 18

what is name of abnormality of fusion in developing philtrum etc?

Answer 18

cleft lip and palate

Question 19

skull vault formed how?

Answer 19

mesenchyme from mesoderm
and ossify by membranous ossification

to form 2 fontanelles though

Question 20

base of skull how it forms?

Answer 20

mesenchyme around notochord - from neural crest cells

form cartilage first
that ossify by endochonral ossification

Question 21

how is viscerocranium of skull formed?

Answer 21

skeleton of face

from sensory capsules and branchial arches

sensory capsules are from mesoderm - form cartilage - then ossify to form bone of face

Question 22

cleft lip fail in fusion of what processes ?

Answer 22

frontonasal process and maxillary process