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Head and Neck > Head and Neck Embryology > Flashcards

Head and Neck Embryology Flashcards

1
Q

What is mesenchyme?

A

Mesenchyme is embryonic connective tissue

Has the same properties as a connective tissue and develops into bone, cartilage, blood vessels etc.)

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2
Q

What do you need to revise?

A

Last years embryology.

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3
Q

What does the head and neck develop from?

A

Branchial/Pharyngeal Arches

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4
Q

What are the Branchial Arches?

A

Series of Arches which develop around the primitive mouth (stomatodeum) and pharynx.

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5
Q

Why can the Branchial arches also be called the pharyngeal arches?

A

They support the primitive pharynx.

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6
Q

How many Branchial arches are there?

A

6 arches initially form, however the 5th one disappears. Leaving behind the 1st, 2nd, 3rd, 4th and 6th arches.

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7
Q

What embryological tissues make up the Branchial arches?

A

Each arch is lined on the outside by ectoderm.

On the inside by endoderm. And in between these layers is the mesoderm.

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8
Q

What is the name of the depression found between each of the branchial arches?

A

The depression is known as a cleft. (As they are found in the endoderm they can also be called the endodermal crests.)

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9
Q

What cells are also found in between the ecto and endoderm (along with the mesoderm)? Outline what these cells are?

A

Neural crest cells - these are temporary cells that can go on to form various different components, such as smooth muscle, bones cartilage etc.

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10
Q

What is the nerve of the 1st branchial arch?

A

Mandibular division of the trigeminal nerve.

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11
Q

What is the nerve of the 2nd branchial arch?

A

Facial nerve

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12
Q

What is the nerve of the 3rd branchial arch?

A

Glossopharyngeal nerve

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13
Q

What is the nerve of the 4th branchial arch?

A

superior laryngeal branch of the vagus nerve

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14
Q

What is the nerve of the 6th branchial arch?

A

Recurrent laryngeal nerve branch of the vagus.

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15
Q

The muscles of facial expression are innervated by what nerve?
What does this indicate about the embryological origin of these muscles?

A

The facial nerve.

As they are innervated by the facial nerve, which arises from branchial arch number 2, we known that these muscles have also arisen from the second branchial arch.

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16
Q

What is the innervation of the digastric muscle? Therefore, what branchial arches must the muscle have developed from?

A

The digastric muscle have 2 different innervations. The anterior belly is innervated by the mandibular branch of the trigeminal, whereas the posterior belly is innervated by the facial nerve.

Therefore we know that the anterior belly will have developed from the 1st branchial arch. And the 2nd from the 2nd branchial arch.

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17
Q

Which muscles have developed from the 1st branchial arch? How do we know this?

A

The muscles of mastication.

We known this because they are innervated by the mandibular division of the trigeminal nerve.

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18
Q

What muscles are derived from the 2nd branchial arch? How do we known this?

A

The muscles of facial expression. We know this because they are innervated by the facial nerve. Which itself is derived from the 2nd arch.

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19
Q

What muscle is derived from the 3rd branchial arch?

A

The stylopharyngeal, this is innervated by the glossopharyngeal.

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20
Q

What muscles do the 4th and 6th give rise too? How can you tell?

A

They give rise to the muscles of the larynx.

21
Q

What skeletal features form from the 1st pharyngeal arch?

A

Mandible, malleus and incus of the middle ear.

22
Q

What skeletal features form from the 2nd pharyngeal arch?

A

Body of the Hyoid, styloid process (also giving rise to a stylohyoid ligament) and the stapes of the middle ear.

23
Q

What cartilaginous feature of the head and neck froms from the 4th branchial arch?

A

The thyroid cartilage.

24
Q

What cartilaginous feature of the head and neck forms from the 6th branchial arch?

A

Cricoid cartilage

25
Q

What skeletal feature forms from the 3rd branchial arch?

A

The greater and lesser horn of the hyoid bone.

26
Q

In terms of the branchial arches, how does the tongue form? What other structures form?

A

The tongue forms from the various pouches/clefts of the branchial arches, (branches 1 & 2) this shows why the innervation of the tongue is so complex.

Just inferior to this the thyroid, parathyroid and parts of the pituitary gland also form.

27
Q

From what does the face develop?

A

The face develops from 5 processes/prominences.

28
Q

What are the names of the prominences from which the face develops?

A
  • 1 frontonasal process
  • 2 maxillary processes
  • 2 mandibular processes
29
Q

Where does the frontonasal process develop from?

A

Develops from mesenchyme superior to the future mouth.

30
Q

Where do the 2 maxillary processes come from (in facial development)?

A

From the maxillary part of the 1st branchial arch mesoderm.

31
Q

Where do the 2 mandibular processes of the embryological face develop from?

A

From the mesoderm of the 1st branchial arch.

32
Q

Which of the 2 facial processes fuse in the midline?

A

The 2 mandibular processes.

33
Q

How does the nostril form?

A

Forms through ectodermal thickening (nasal placode) which pushes inwards, or invaginates to form a nasal pit (nostril)

34
Q

The invagination of the nasal placode divides what?

A

Divides the frontonasal process into:

  1. Lateral nasal process
  2. Medial nasal process
35
Q

What happens to the 2 medial nasal processes that are formed as a result of invagination?

A

The two nasal processes fuse with each other in the midline.

36
Q

After the nasal processes have fused what then happens?

A

The medial nasal process further grows downwards and laterally, to form a process called the Philtrum. (think the wee lines connecting upper lip and nose).

37
Q

Movement of the facial process downwards and laterally has what end result?

A

Separation of the nostrils and the primitive mouth.

38
Q

The development of the palate occurs in three stages. What is stage 1?

A

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

39
Q

What is stage 2 in the formation of the palate?

A

From the maxillary processes, two palatine shelves grow inwards

40
Q

What is stage 3 in the formation of the palate?

A

The palatine shelves meet in the midline and form the secondary palate.

41
Q

Formation of the palate has what end result?

A

The nasal and oral cavities are now separate.

42
Q

Abnormal formation of the philtrum and the palate can have what clinical impact?

A

Can result in a cleft lip and palate.

43
Q

What is the cranial vault? How does it form?

A

The flat bones of the skull.

Formed by membranous ossification. (from mesechyme derived from the mesoderm that lies above the developing brain)

44
Q

What type of bones are the base of the skull? How do these form?

A

Irregular bones

Bones are formed by endochondral ossification.

45
Q

What is the viserocranium and how does this form?

A

Skeleton on the face.

Partly from branchial arches, and partly from sensory (special sense) capsules.

46
Q

What is the condition of the skull vault at birth?

A

Not fully formed at birth

Sutures between them soft allow deformation during passage through birth canal

6 membrane covered fontanelle of clinical significance (such as the anterior frontalle, on top of the skull, which closes arounf 1.5 years)

47
Q

What is Craniosynostosis?

A

Abnormally prematural fusion of the cranial sutures, leading to abnormal development of the skull and brain.

48
Q

Generally outline the formation of the bones of the base of the skull?

A
  • Mesenchyme around notochord is dervied predominatly from neural crest cells.

Preformed initlaly as cartilage, which then later ossifys.

49
Q

From where are the sensory capsules derived and what do they form?

A

Sensory capsules are derived from mesoderm of ‘somites’ in head and neck region.

These preform in cartilage and ossify to form bones around the sense organs – ie nose, eye and ear

They form partly base of skull, partly viscerocranium.

Head and Neck (13 decks)

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