Head and Neck Embryology

Question 1

RECAP- what happens after the sperm fertilises the egg?

Answer 1

Zygote divides to form blastocyst

Question 2

RECAP- the blastocyst flattens. What does this form?

Answer 2

Bilateral disc which then develops into three layers = trilaminar disc

Question 3

RECAP- name the three layers of the trilaminar disc.

Answer 3

Ectoderm
Mesoderm
Endoderm

Question 4

RECAP- name the space above the ectoderm/.

Answer 4

Amniotic cavity

Question 5

RECAP- name the space below the endoderm.

Answer 5

Yolk sac

Question 6

RECAP- the notochord forms in the trilaminar disc. This is the axis for many developments. However, the notochord does not fully extend from the very top of trilaminar disc to the very bottom.
What happens in these sections?

Answer 6

No mesoderm so ectoderm and endoderm fuse.

There are two areas with no mesoderm and these form the mouth and the anus.

Question 7

RECAP- describe the development of the neural tube.

Answer 7

Notochord releases chemicals which causing thickening of ectoderm epithelium. This forms neural crests.
The ends of the neural crests come together and closes, forming the neural tuber which then sinks down away from the ectoderm.

->if you don’[t understand this, watch the Part 1 of Head and Neck Embryology, goes over a recap of what we know so far and might be useful before exam!

Question 8

RECAP- what forms from the neural tube?

Answer 8

Brain and spinal cord

Question 9

RECAP- in the process of neural tube formation, what else is produced?

Answer 9

Neural crest cells which migrate and give rise to many different structures.

Question 10

RECAP- what comes from the paraxial mesoderm?

Answer 10

Somites

Question 11

What do somites go onto develop?

Answer 11

Axial skeleton
Muscles

Question 12

RECAP- how many somites are formed in human embryos?

Answer 12

33

Question 13

RECAP- what does the ectoderm develop into?

Answer 13

Skin

->think, the ectoderm goes around everything

Question 14

RECAP- what does the mesoderm develop into?

Answer 14

Muscle, connective tissue

Question 15

RECAP- what does the endoderm develop into?

Answer 15

Gut tube

Question 16

RECAP- where does the respiratory tract develop from?

Answer 16

Foregut regions

Question 17

What are the pharyngeal/brachial arches?

Answer 17

Series of arches which develop around the future mouth and pharynx.

Question 18

When in the process of embryological development do the pharyngeal/branchial arches develop?

Answer 18

Late week 4- week 6

Question 19

How many branchial arches develop?

Answer 19

5

->six start to develop but no.5 disappears leaving us with 1,2,3,4,6

Question 20

What makes up the branchial arches?

Answer 20

Ectoderm- makes outside
Mesoderm- bulky middle section + neural crest cells
Endoderm- lines inside of arch

Question 21

Which structures develop in the mesoderm of the branchial arches?

Answer 21

Blood vessels
Nerves
Skeletal elements

(think about what arises from mesoderm in general)

Question 22

What else can the ectoderm form in the branchial arches as well as forming the outer layer?

Answer 22

Forms clefts between the arches
These clefts can develop into structure like the tongue

Question 23

What else can the endoderm form in the branchial arches as well as forming the inner layer?

Answer 23

Forms pouches between the arches

Question 24

Cranial nerves form from the branchial arches.
Which nerve develops from the first branchial arch?

IMPORTANT TO REMEMBER, COMMON EXAM QUESTION

Answer 24

Mandibular branch of Trigeminal nerve (CN V3).

Question 25

Cranial nerves form from the branchial arches. Which nerve develops from the second branchial arch? IMPORTANT TO REMEMBER, COMMON EXAM QUESTION

Answer 25

Facial nerve (CN VII)

Question 26

Cranial nerves form from the branchial arches. Which nerve develops from the third branchial arch? IMPORTANT TO REMEMBER, COMMON EXAM QUESTION

Answer 26

Glossopharyngeal nerve (CN IX).

Question 27

Cranial nerves form from the branchial arches. Which nerve develops from the fourth branchial arch? IMPORTANT TO REMEMBER, COMMON EXAM QUESTION

Answer 27

Superior laryngeal branch of the Vagus nerve (CN X)

Question 28

Cranial nerves form from the branchial arches. Which nerve develops from the sixth branchial arch? IMPORTANT TO REMEMBER, COMMON EXAM QUESTION

Answer 28

Recurrent laryngeal branch of the Vagus nerve (CN X)

Question 29

Which nerve innervates all the muscles of face expression of the face?

Answer 29

Facial nerve (CN VII)

Question 30

Therefore, which branchial arch does nerve supplying the face come from?

Answer 30

Second branchial arch

Question 31

What is the anterior belly of the digastric muscle innervated by?

Answer 31

Mandibular branch of trigeminal nerve

Question 32

What is the posterior belly of the digastric muscle innervated by?

Answer 32

Facial nerve

Question 33

Which nerve innervates the muscles of mastication (chewing)? Which branchial arch will this be developed from?

Answer 33

Submandibular branch of trigeminal nerve (CN V3). Therefore, the muscles of mastication are developed from the first branchial arch.

Question 34

The glossopharyngeal nerve innervates a single muscle. Name it and tell me the branchial arch it developed from.

Answer 34

Stylopharyngeus muscle. This muscle must have developed from the third branchial arch :) ->this makes sense to me when I am writing this but if you need a recap, go over part 2 of the lecture, so well explained!!

Question 35

The superior and recurrent laryngeal nerves (both branches of Vagus nerve) supply the muscles of the vocal cord. Where will these muscles have developed from?

Answer 35

Branchial arches 4&6

Question 36

Skeletal elements also develop from the branchial arches. Which bones would form from the first branchial arch?

Answer 36

Mandible, malleus and incus.

Question 37

Skeletal elements also develop from the branchial arches. Which bones would form from the second branchial arch?

Answer 37

Upper hyoid bone Stapes Stylohyoid ligament Styloid process

Question 38

Skeletal elements also develop from the branchial arches. Which bones would form from the third branchial arch?

Answer 38

Lower part of hyoid bone

Question 39

Skeletal elements also develop from the branchial arches. Which bones would form from the fourth branchial arch?

Answer 39

Thyroid cartilages

Question 40

Skeletal elements also develop from the branchial arches. Which bones would form from the sixth branchial arch?

Answer 40

Lower thyroid cartilage Cricoid cartilage

Question 41

The clefts and pouches which are formed by the endoderm and ectoderm give rise to structures. Name them.

Answer 41

Tongue Thyroid gland Parathyroid gland Part of pituitary gland

Question 42

The face develops from five processes/prominences. Please name them.

Answer 42

1 frontonasal process 2 maxillary processes 2 mandibulae processes

Question 43

Where do the two maxillary processes develop from?

Answer 43

Maxillary part of first branchial arch

Question 44

Where do the two mandibular processes develop from?

Answer 44

First branchial arch

Question 45

Where does the frontonasal process develop from?

Answer 45

The mesenchyme superior to the future mouth

Question 46

What happens to the 2 mandibular processes?

Answer 46

They fuse together in the midline

Question 47

There is ectodermal thickening in the frontonasal process. What does this form?

Answer 47

Nasal placode

Question 48

What happens to the nasal placode?

Answer 48

Invaginates to form nostrils

Question 49

The invagination of the nasal placode divides the frontonasal process into two parts. Name them.

Answer 49

Lateral nasal process Medial nasal process

Question 50

What separates the nasal opening from the mouth?

Answer 50

Philtrum

Question 51

What do the lateral nasal processes form?

Answer 51

Lateral parts of nose

Question 52

What do the medial nasal processes form?

Answer 52

Bridge and pointy bit of nose

Question 53

What do the maxillary processes form?

Answer 53

Join and form upper lip

Question 54

What do the mandibular processes form?

Answer 54

Lower lip

Question 55

What needs to develop in order to separate the nasal and mouth cavities?

Answer 55

Palate

Question 56

Describe the formation of the primary palate.

Answer 56

Medial nasal process grows downwards and forms the philtrum which forms the primary palate.

Question 57

What happens to the maxillary processes in the development of the palate?

Answer 57

Two primary palatine shelves grow inwards

Question 58

How is the secondary palate formed?

Answer 58

Palatine shelves meet in the midline to form secondary palate which separates the nasal and oral cavities.

Question 59

Which congenital issue may arise if the maxillary processes do not fully fuse with the philtrum?

Answer 59

Cleft lip (harelip)

Question 60

Apart from cosmetic reasons, why would you want to make a diagnosis of cleft lip?

Answer 60

No separation between oral and nasal cavities meaning food and drink may be aspirated in the baby

Question 61

Name the three regions of the skull.

Answer 61

Cranial vault Base of skull Viscerocranium

Question 62

Which type of bones make up the cranial vault of the skull?

Answer 62

Flat bones

Question 63

Which type of bones make up the base of the skull?

Answer 63

Irregular bones

Question 64

How are the cranial vault bones formed?

Answer 64

Formed by membranous ossification calvaria as are membranous bones.

Question 65

How are the base bones of the skull formed?

Answer 65

Endochondral ossification

Question 66

What does the viscerocranium do?

Answer 66

Forms capsules around sensory special sense organs e.g. eyes

Question 67

Describe the bones of the cranial vault of the skull at birth.

Answer 67

Not fully formed Soft sutures between them Deformation during birth may occur

Question 68

At what age does the anterior fontanelle close?

Answer 68

Approx. 1.5yrs

Question 69

What is meant by a fontanelle?

Answer 69

Softer spots on an infant's head where the bone has not fully fused together

Question 70

What happens if the fontanelles fuse too quickly?

Answer 70

Does not provide space for facial skeleton and brain to grow, leading to deformities.

Question 71

Name some deformities seen when the fontanelles fuse too quickly.

Answer 71

Craniosynostosis

Question 72

What can happen in craniosynostosis.

Answer 72

Abnormal face shape Sometimes mental retardation

Question 73

How do the base bones of the skull get formed?

Answer 73

Initially cartilage which then becomes ossified in the process of endochondral ossification

Question 74

Where do the sensory capsules for the sensory organs develop from?

Answer 74

The mesoderm of somites