1.1: Embryology Flashcards

1
Q

What do the pharyngeal arches contribute to?

A

Much of the face and neck

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2
Q

When do the pharyngeal arches develop?

A

In weeks 4 and 5

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3
Q

What are the names of the pharyngeal arches?

A

They are number 1, 2, 3, 4, and 6 There is no 5

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4
Q

Describe the order of the pharyngeal arches (anatomically and how they develop)

A

1 is most cranial They develop in this order

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5
Q

What are the components of the pharyngeal arches?

A
  • Mesenchymal Core - Neural Crest Cells - Cranial Nerve Component - Aortic Arch Component
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6
Q

What layers of the mesoderm make up pharyngeal arches?

A

All layers

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7
Q

Describe the structure of the pharyngeal arches (what separates them?)

A

The arches are separated by clefts (ectoderm) and pouches (endoderm)`

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8
Q

Name the cranial nerves that are associated with each pouch?

A

Pouch 1 = CN V (Trigeminal, Only mandibular and maxillary) Pouch 2 = CN VII (Facial) Pouch 3 = CN IX (Glossopharyngeal) Pouch 4 and 6 = CN X (Vagus) Cranial nerves 5, 7, 9 and 10

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9
Q

Describe Arch 1: Bone

A

Different from the others - divided into two components: The maxillary process of the 1st arch contributes to - Maxilla - Zygoma - Part of temporal The mandibular process of the 1st arch contributes to - Mandible - Two ossicles (Incus and malleus)

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10
Q

Describe Arch 1: Muscle

A

Muscles of mastication Anterior Belly of Digastric Mylohyoid Tensor Timpani (Middle Ear) Tensor Palatini (Involved in palate)

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11
Q

Describe Arch 1: Nerves

A

Supplied by Cranial Nerve 5 (Trigeminal) V1 = Opthalamic V2 = Mandinbular V3 = Maxillary Provides sensory supply to the skin of the face

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12
Q

Describe Arch 2: Bone

A

Stapes Styloid Process of Temporal Bone Stylohyoid Ligament Lesser Horn of Hyoid Upper Part of Hyoid Body

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13
Q

Describe Arch 2: Muscle and Nerve

A

Muscles of Facial Expression Stapedius Stylohyoid Posterior Belly of Digastric Auricular Muscles All supplied by VII (Facial Nerve)

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14
Q

Describe Arch 3: Bone Muscle Nerve

A

Greater horn of hyoid Lower part of hyoid Stylopharyngeus Muscles Glossopharyngeal nerve (IX)

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15
Q

Describe arches 4 and 6:

A

There are no bony components Gives rise to the laryngeal cartilages Muscles: 4: Cricothyroid, Levator Palatini and Pharyngeal Constrictors Supplied by Superior Laryngeal Nerve (From Vagus X) 6: Intrinsic laryngeal Supplied by recurrent laryngeal Nerve (From Vagus X)

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16
Q

What is the only muscle innervated by glossopharyngeal nerve?

A

Stylopharyngeus

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17
Q

What are pouches?

A

Pouches are the indentations in the ENDODERM between adjacent arches

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18
Q

Describe pouch 1?

A

This engulfes the bony structures of arch 1 and 2 to give us the middle ear cavity, the eustachian tube and contributes to the tympanic membrane

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19
Q

Describe pouch 2?

A

Becomes the palatine tonsil

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20
Q

Describe pouch 3?

A

Becomes the inferior parathyroid gland and thymus

21
Q

Describe pouch 4?

A

Becomes the superior parathyroid gland and ultimobranchial body

22
Q

Describe the movement of pouch 3 and 4?

A

Both have to move to get to their final position in the body. All move inferiorly following the thyroid. The ultimobranchial body populates the thyroid, the parathyroid glands become associated

23
Q

Describe the clefts?

A

The indents in the ectoderm

24
Q

Describe Cleft 1?

A

Becomes the external auditory meatus

25
Q

Describe clefts 2-4?

A

DIsappear

26
Q

Describe how the first cleft and the first pouch meet?

A

They meet to form the tympanic membrane and the ear canal

27
Q

What are the two functions of the inner ear?

A

Balance (Semicircular Canals) Hearing (organ of corti)

28
Q

Describe otic placodes?

A

These are an indentation ectoderm They invaginate to form otic pits They pinch off to form otic vesicles The otic vesicles give rise to the inner ear structures

29
Q

Describe the formation of the inner ear from the otic vesicles?

A

The saccular part becomes the cochlear The utricular part becomes the semi circular canals

30
Q

Describe the three regions of the otic vesicles?

A

Endolymphatic Duct Saccular Part Utricular Part

31
Q

How many semicircular canals? Names?

A

Three Superior Posterior Lateral

32
Q

Describe the semicircular canals function and how they shape/layout helps them achieve this?

A

Involved in balance They are all at right angles to each other This allows them to detect movement on all planes

33
Q

Describe the ends of the semicircular canals?

A

The dilated bit is called the CRUS AMPULLARE The non dilated bit is called the CRUS NONAMPULLARE

34
Q

Describe the ampullae?

A

Within the ampullae is the CRISTA AMPULLARIS This contains the sensory cells for balance which respond to movement. They are innervated by the vestibular fibres of cranial nerve VIII (vestibulocochlear)

35
Q

Describe the cochlear duct - where does it develop from? - Another name? - Surrounded boy? - Supported by?

A

Develops from the saccular part of the otic vesicles Another name is the Scala Media Surrounded by two cavities important for sound conduction called Scala Vestibuli and Scala Tympani Supported by a bony strut called the Modiolus

36
Q

Describe the Modiolus?

A

A bony strut that supports the Cochlear Duct/Scala Media Contains spiral ganglion and auditory nerve fibres

37
Q

Look at this diagram

A

Done

38
Q

Describe the Organ of Corti?

A

This is the organ that allows us to hear It sits on the basilar membrane Contains inner hair cells and outer hair cells The cells are covered by the TECTORIAL MEMBRANE This vibrates and the sensations are detected by the hair cells Signals are sent to the brain via the auditory nerve fibres of the vestibulocochlear nerve

39
Q

Describe where the ossicles of the middle ear come from?

A

The Malleus and Incus come from arch 1 The stapes comes from arch 2

40
Q

Describe the development of the middle ear in regards to the first pouch? - Bones/Ligaments - Tympanic Membrane

A

The pouch extends towards the ossicles and encloses them This forms the tympanic cavity proper Ligaments appear to support the bones The pouch forms part of the tympanic membrane

41
Q

Describe the development of the outer ear?

A

The external auditory meatus develops from the 1st pharyngeal cleft. A meatal plug is formed which develops after 7months to become part of the tympanic membrane

42
Q

What is the auricle?

A

The external ear

43
Q

Describe the origins of the auricle?

A

It is composed of mesenchymal proliferation called HILLOCKS 3 comes from the 1st arch 3 come from the 2nd arch They fuse to form the auricle

44
Q

Describe movement of the auricle?

A

Auricles are originally lower in the neck They move superiorly due to development of the mandible

45
Q

Describe Microtia/Anotia

A

Microtia is a very small ear Anotia is no ear at all

46
Q

Describe preauricular appendages?

A

This is extra appendages on the ear

47
Q

Describe a preauricular pit?

A

This is a small indentation in the ear

48
Q

Link between common external ear defects and other congenital abnormalities?

A

Congenital abnormalities are more common in those with external ear defects