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Embryology > Lecture 14 - Differentiation of the Ectoderm + Organ Development > Flashcards

Lecture 14 - Differentiation of the Ectoderm + Organ Development Flashcards

1
Q

What part of the ectoderm makes up the neural ectoderm and what does the neural ectoderm give rise to? (2)

A

The part of the ectoderm that is closer to the midline becomes the neural ectoderm

Neural system

Neural crest cells

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2
Q

What part of the ectoderm becomes the non-neural ectoderm and what does the non-neural ectoderm give rise to? (4)

A

The part of the ectoderm that is further away from the midline

Epidermis of skin

Associated structures:

  • hair
  • nails
  • tooth enamel
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3
Q

Describe the formation of the neural plate

A

Cells on the ectoderm placed along/near the midline change shape to become tall + columnar (3rd week of development)

This raised/elevated appearance is the neural plate

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4
Q

Describe the appearance of the neural plate in regards to width along the embryo and what each end will eventually give rise to

A

Wider at the rostral end - brain

Narrower towards more caudal levels - spinal cord

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5
Q

Describe the process of primary neurulation

A

The central area of the neural plate shifts downwards (neural groove)

Outer edges of the neural plate rise + curl upwards and inwards (neural folds)

Neural folds eventually meet at midline and fuse

When neural plates fuse, a neural tube is formed

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6
Q

Describe the process of the closure of the neural tube

A

Begins at neck level and proceeds causally and rostrally (like a zipper)

The neural tube does not initially close fully

  • rostral neuropore
  • caudal neuropore
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7
Q

What condition occurs when the rostral neuropore fails to close?

A

Anencephaly - lethal - majority of brain does not form

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8
Q

What condition occurs when the caudal neuropore fails to close?

A

Spina bifida - treatable depending on severity - sac filled with spinal fluid and sometimes part of the spinal cord formed on external lower back

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9
Q

How many births does failure of neuropore closing affect?

A

1 in 1000 live births

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10
Q

How does the neural crest arise?

A

As neural folds arose, a small group of cells differentiate at the place that will become the tip of the neural folds - neural crest cells

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11
Q

What do neural crest cells do?

A

Neural crest cells become mesenchymal and migrate out of the lateral edges to invade different parts of the embryo and contribute to the production of a variety of tissues

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12
Q

What contribution does neural crest cells give at the level of the spinal cord (trunk neural crest)?

A
  • gives rise to the PNS by producing neurons that carry sensory information from the body to the CNS and the neurons that will carry motor information to the gut
  • hormone secreting cells of the adrenal gland
  • melanocytes
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13
Q

What contribution does cranial neural crest cells give to the body?

A

Gives rise to cartilage, bone and muscles of the face + neck

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14
Q

What is the brain and spinal cord derived from?

A

The neural plate

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15
Q

What does the rostral region of the neural tube exhibit by the 4th week of development?

A

3 fluid filled brain vesicles/enlargements + a narrow tube behind these that will give rise to the spinal cord

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16
Q

Name the 3 brain vesicles and what they correspond to

A

Telencephalic vesicle - forebrain

Mesencephalic vesicle - midbrain

Rhombencephalic vesicle - hindbrain

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17
Q

What cells is the formation of the head primarily the result of?

A

Cranial neural crest cells

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18
Q

_____ neural crest cells give rise to a larger variety of tissue types than _____ crest cells

A

Cranial neural crest cells give rise to a larger variety of tissue types than trunk crest cells

19
Q

What structures do cranial neural crest cells give rise to? (6)

A

Neurons

Glia

Melanocytes

Muscle, bone and cartilage of lower face

20
Q

Where and when do the paryngeal arches form?

A

Develop on either side of the embryo at the level of the future head and neck during embryonic folding

21
Q

What is the inside, middle and outside of the arches composed of?

A

Inside - endoderm
Middle - mesoderm
Outside - ectoderm

22
Q

What 3 structures can be found inside each pharyngeal arch?

A

Cartilage, blood vessel, nerve

23
Q

What separates the pharyngeal arches on the inside of the embryo?

A

Pharyngeal pouches

24
Q

What separates pharyngeal arches on the outside of the embryo?

A

Pharyngeal clefts

25
Q

What do the pharyngeal arches give rise to? (3)

A

Muscles of facial expression

Bones + muscles in theist

Cartilage in pharynx

26
Q

What contribution does cranial neural crest cells give to the pharyngeal arches? (3)

A

Formation of the skeleton

Connective tissue

Some of the sensory ganglia of the PNS

27
Q

What does the endoderm layer of the pharyngeal arch contribute to? (2)

A

Some glands

Epithelium of pharynx

28
Q

What does the mesoderm layer of the pharyngeal arch contribute to? (2)

A

Head and neck muscles

Blood vessels

29
Q

What does the ectoderm layer of the pharyngeal arch contribute to? (2)

A

Epithelium of the mouth and face

Some sensory ganglia of the PNS

30
Q

Derivatives of the first pharyngeal arch: bones (6)

A

Maxilla (upper jaw)

Mandible (lower jaw)

Maleus and incus of the middle ear

Alisphenoid bone

Squamous part of temporal

Zygomatic

31
Q

Derivatives of the first pharyngeal arch: muscles of mastication

A

Masseter

Temporalis

32
Q

Derivatives of the first pharyngeal arch: nerves (2)

A

Mandibular nerve

Maxillary nerve

(Both are branches of the trigeminal nerve)

33
Q

How many swellings are formed by the end of the 4th week?

A

Five

34
Q

What are the five initial swellings formed by?

A

Neural crest + some mesenchyme originating from the cranial somitomeres corresponding primarily to the first branchial/pharyngeal arch

35
Q

Name the 5 facial prominences and what they eventually give rise to

A

Fronto-nasal prominence - forehead

Medial nasal prominence - medial pit fuses to form the central pit of the upper lip (philtrum); middle (bridge) of nose

Lateral nasal prominence - sides of the nose and nostrils

Maxillary prominence - increases in size and pushes medial nasal prominences towards midline, forms upper lip with 2 medial prominences + 2 maxillary prominences

Mandibular prominence - lower lip and jaw formed by 2 mandibular prominences growing towards midline and eventually fusing

36
Q

What is cleft lip the result of?

A

Failure of the medial nasal process + maxillary nasal process to fuse, affects 1/1000 live births

37
Q

What are abnormalities in the outer and middle ear the result of?

A

Defects in development of the 1st pharyngeal arch

38
Q

What is the first functional organ to develop in the embryo?

A

The heart

39
Q

Describe the formation of the primitive heart

A

Cells that will give rise to the heart found as two patches (heart fields) near the rostral end (anterior third) of the primitive streak

Primitive heart cells organise into two tubes, move towards midline and fuse

At 3 weeks - fusion of two heart primordial tubes = one tube, able to contract

At 4-5 weeks - heart has two chambers - primitive atrium + primitive ventricle

A series of morphogenetic events (heart looping) transforms primitive heart into four-chambered heart

40
Q

Describe the process of heart looping

A

Initially, blood flows in at the caudal end via sinus venosis, pumped out at cranial end via bulbus cordis

Rostral end

BC
PV
PA
SV

Caudal end

Tube folds:
PV moves caudally
PA moves rostrally
PA + SV both moved dorsally too

Two ventricles formed by the formation of the internal interventricular septum

PA - LA + RA

41
Q

What is the purpose of the embryonic circulatory system?

A

Access to gases and nutrients in the absence of functional lungs + intestines

42
Q

Name the 3 embryonic circuits and their functions

A

Intraembryonic circuit - serves tissue of the embryo

Vitelline circuit - gathers nutrients from the yolk sac

Umbilical circuit/Allantois - gets rid of nitrogenous wastes into the allantois, brings in nutrient and oxygen rich blood from the placenta

43
Q

What happens to the aortic arches one the pharyngeal arch they’re associated with disappears?

A

The aortic arches give rise to the artery that supplies blood to the derivatives of their respective pharyngeal arches

Embryology (5 decks)

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