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Nervous System > Embryology > Flashcards

Embryology Flashcards

1
Q

What are the components of the pharyngeal apparatus?

A

1) 4 Pharyngeal pouches
2) 4 Pharyngeal arches
3) Pharyngeal cleft

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2
Q

1st Pharyngeal arch:
a) bones
b) muscles
c) nerve
d) artery

A

1st Pharyngeal arch:
a) bones
i) Maxilla
ii) Mandible
iii) Malleus
iv) Incus
v) Squamous part of temporal bone
vi) Zygomatic bone
vii) Palatine bones

b) muscles
i) Muscles of mastication
ii) Anterior belly of digastric
iii) Tensor veli palatini
iv) Tensor tympani

c) nerve
- trigeminal

d) artery
- maxillary

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3
Q

2nd Pharyngeal arch:
a) bones
b) muscles
c) nerve
d) artery

A

2nd Pharyngeal arch:
a) bones
i) Stapes
ii) Styloid process
iii) Lesser horn
iv) superior part of hyoid bone body

b) muscles
i) Muscles of facial expression
ii) Stapedius
iii) Mylohyoid
iv) Posterior belly of digastric

c) nerve
- facial

d) artery
i) Hyoid
ii) Stapedial

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4
Q

3rd Pharyngeal arch:
a) bones
b) muscles
c) nerve
d) artery

A

3rd Pharyngeal arch:
a) bones
- (i) greater horn and (ii) inferior part of hyoid bone

b) muscles
- stylopharyngeus

c) nerve
- glossopharyngeal

d) artery
i) common carotid
ii) 1st part of internal carotid artery

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5
Q

What are the layers of the pharyngeal arches and what do they respectively form?

A

Each composed of mesoderm

External covering: ectoderm → pharyngeal clefts

Internal covering: endoderm → pharyngeal pouches

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6
Q

4th/6th Pharyngeal arch:
a) bones
b) muscles
c) nerve
d) artery

A

4th/6th Pharyngeal arch:
a) bones
i) Thyroid
ii) Cricoid
iii) Arytenoid
iv) Corniculate
v) cuneiform

b) muscles
4th:
i) cricothyroid
ii) levator veli palatini
iii) pharyngeal constrictors

6th:
- intrinsic muscles of larynx (except cricothyroid)

c) nerve
4th: superior laryngeal
6th: recurrent laryngeal

d) artery
4th: left aortic arch, right subclavian
6th: pulmonary arteries

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7
Q

What does the 1st pharyngeal pouch form?

A

Eustachian tube

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8
Q

What does the 2nd pharyngeal pouch form?

A

Palatine tonsil

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9
Q

What does the 3rd pharyngeal pouch form?

A

1) Inferior parathyroid
2) Thymus

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10
Q

What does the 4th pharyngeal pouch form?

A

1) Superior parathyroid
2) Ultimobranchial body

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11
Q

What does the 1st pharyngeal cleft form?

A

1) External auditory meatus
2) Outer tympanic membrane

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12
Q

What do the 2nd-4th pharyngeal cleft form?

A

1) Side of neck
2) Mesenchymal component
3) Cervical sinus (eventually obliterates)

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13
Q

What is Meckel’s cartilage and what is its function?

A

Part of mandibular prominence of 1st pharyngeal arch
- provides U shaped template/scaffold for mandible to form

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14
Q

What is an example of a congenital disorder associated with malformation of pharyngeal apparatus structures?

A

Treacher Collins Syndrome

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15
Q

What is laryngomalacia?

A

Congenitally Omega shaped epiglottis → stridor

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16
Q

What is Reichert’s cartilage and what is its function?

A

Part of 2nd pharyngeal arch
- forms:
i) Stapes
ii) Styloid process
iii) Stylohyoid ligament
iv) Lesser and upper part of hyoid bone

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17
Q

What are 2 classifications of skull bones?

A

1) Neurocranium
- 2 temporal
- 2 parietal
- 1 frontal
- 1 occipital
- 1 sphenoid
- 1 ethmoid

2) Viscerocranium
- 2 nasal
- 2 lacrimal
- 2 zygomatic
- 2 palatine
- 2 maxillae
- 2 inferior nasal conchae
- 1 vomer
- 1 mandible

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18
Q

True or false:
Unlike long and axial bones, the bones of the skull are all formed by intramembranous ossification.

A

False.
Both by intramembranous and endochondral

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19
Q

What is the stomodeum?

A

Rudimentary mouth
- forms opening between future oral cavity and foregut
- surrounded by 5 facial prominences

20
Q

What lines the stomodeum?

A

Bucco(Oro)pharyngeal membrane
- stops developing during 4th week to form opening between future oral cavity and foregut.

21
Q

Where are the nasal placodes located and what do they form?

A

Bilateral on frontonasal prominences

Form → Nasal pits → medial/lateral nasal prominences → (i) lip philtrum (ii) lateral sides of nostrils (iii) primary palate

22
Q

What are the embryological structures that form the upper lip?

A

2 medial nasal prominences and 2 maxillary prominences

23
Q

Facial development fml

A

1) Maxillary prominences grow → compress medial nasal prominence towards midline → fuse (lose cleft)

2) Nasolacrimal groove (formed between maxillary and lateral nasal prominence) form epithelial cord → canalise → nasolacrimal (eventual tear) duct

3) Upper end of nasolacrimal duct widens → lacrimal sac

4) Epithelial cord detaches → maxillary and lateral nasal prominences merge

5) Maxillary prominence form cheek and maxilla

6) Lateral nasal prominences form ala of nose

7) Mandibular prominences cross midline and fuse → lower lip and mandible

8) Maxillary and mandibular prominences fuse → angles of mouth

9) Superior portion of frontonasal prominences → forehead

24
Q

What are the structures formed by the frontonasal prominences?

A

1) Forehead
2) Nose bridge
3) Frontal and nasal bones

25
Q

What are the structures formed by the maxillary prominences?

A

1) Upper cheek
2) Lateral upper lip
3) Maxilla
4) Zygomatic bone
5) Secondary palate

26
Q

What are the structures formed by the mandibular prominences?

A

1) Mandible
2) Chin
3) Lower lip
4) Lower cheek

27
Q

What are the structures that are formed by the medial nasal prominces?

A

1) Midline of nose
2) Lip philtrum

28
Q

What do the lateral nasal prominences form?

A

Nasal ala

29
Q

How does the nasal and oral cavity become continuous during embryonic development?

A

Rupturing of oronasal membrane lining the stomodeum → continuous nasal and oral cavity via primitive choanae

30
Q

Describe the process of neurulation.

A

Formation of neural tube from ectoderm:
1) Formation of notochord
- migrating mesenchymal cells collect in midline of embryo → notochordal process → fuse with endoderm → notochordal plate → detach from endoderm → notochord

2) Thickening of ectoderm → neural plate

3) Elevation of lateral edges of neural plate → neural groove

4) Further elevation → canalisation of neural groove → neural tube

5) Spinal crest cells (from lateral edges) migrate to form other structures (eg. PNS)

31
Q

Where do neural tube defects tend to present and why?

A

Cranial and caudal ends (last to close)

32
Q

What are 3 examples of neural tube defects?

A

Caudal:
1) Spinal bifida occulta
- gap anywhere from L5-S1 → tufting of hair
- asymptomatic

Vertebral fusion failure:
2) Spinal bifida meningocoele
- protrusion of meninges

3) Spinal bifida myelomeningocoele
- protrusion of meninges + nerve endings

Cranial:
4) Execephaly
- brain outside of skull
- can progress to anencephaly

5) Anencephaly
- missing parts of brain/skull

33
Q

Describe the formation of the cauda equina.

A

During development vertebral column grows much faster than spinal cord
→ at birth, spinal cord stretches to L3
→ during development pulled back to L2 but meninges still extend to S2
→ nerves suppling lower than L2 extend from conus medullaris → cauda equina

34
Q

What are the 2 cell types that arise from the neurocoele/central canal of the neural tube and what do they form?

A

1) Neuroblasts
- neurons
(Marginal layer → white matter, mantle layer → grey matter)

2) Glioblasts
- neuroglial cells

35
Q

The spinal cord forms from the (cranial/caudal) portion of the neural tube.

A

Caudal

36
Q

Describe the formation of the primary, secondary and final brain vesicles.

A

1) Prosencephalon
a) Telencephalon
→ (i) Cerebral cortex (ii) Basal ganglia
b) Diencephalon
→ (i) Optic cup (ii) Stalk (iii) Pituitary gland (iv) Thymus (v) Hypothalamus (vi) Pineal body

2) Mesencephalon
→ midbrain

3) Rhombencephalon
a) Metencephalon
→ (i) pons (ii) cerebellum
b) Myelencephalon
→ medulla oblongata

37
Q

Describe the formation of the ventricles.

A

Formed from cavtity of neural tubes:
1) Lateral ventricle
- telencephalon

2) Third ventricle
- telencephalon + diencephalon

3) Future cerebral aqueduct
- mesencephalon

4) Fourth ventricle
- metencephalon + myelencephalon

38
Q

How are the lateral and third ventricles connected?

A

Foramen of monro

39
Q

What is the encephalocoele?

A

Congenital defect → herniation of intracranial contents

40
Q

What is hydrocephalus?

A

Enlarged head due to ventricles filled with extra fluid (excess CSF)

41
Q

How does the tongue form?

A

Anterior 2/3: 1st pharyngeal arch
1) proliferation of mesoderm → lateral lingual swellings + tuberculum impar (5th wk)

2) Lateral lingual swellings grow larger than tuberculum impar → fuse at median sulcus

Posterior 1/3: 3/4th pharyngeal arch
1) proliferation of mesoderm → Copula + Hypopharyngeal eminence

2) Hypopharyngeal eminence grower larger than copula → fuse to anterior 2/3 at terminal sulcus

42
Q

What are 2 malformations of the tongue?

A

1) Ankyloglossia
- frenulum extends to tip of tongue

2) Bifid tongue
- Inadequate fusion of lateral swellings
- a/w cleft lower lip

43
Q

How does the primary palate form and what does it give rise to?

A

Medial growth of maxillary prominences → union of medial nasal prominences

Forms:
1) Labial components (philtrum)
2) Upper jaw component (4 incisors)
3) palatal component

44
Q

How does the secondary palate form?

A

1) Outgrowths of maxillary process → Palatine shelves

2) Tongue moves downwards + mandible grows down and out

3) Palatine shelves fuse → secondary palate

4) Nasal septum fuse with secondary palate → hard palate

45
Q

What is the malformation of the palate formation called?

A

Cleft palate
eg. cleft lip, uvula, palate, full palate

Nervous System (14 decks)

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