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Z OLD Tissues of the Body > The Fate of the Mesoderm > Flashcards

The Fate of the Mesoderm Flashcards

1
Q

What has happened by the end of the third week post fertilisation?

A

NAME?

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2
Q

What ist he most plastic of the germ layers?

A

Mesoderm

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3
Q

What is meant by the mesoderm being the most plastic?

A

It gives rise to the biggest number of tissues

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4
Q

What is the notochord responsible for?

A

Releasing signals to surrounding ectoderm

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5
Q

What does the notochord undergo?

A

Neurulation

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6
Q

What forms the nervous system?

A

Notochord-driven induction of the ectoderm

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7
Q

What happens to the neural plate?

A

It folds up to form the tube which develops into the brain and spinal cord

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8
Q

What is the tube that develops into the brain and spinal cord called?

A

The neural tube

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9
Q

What is the formation of the neural tube key to?

A

Normal development of the CNS

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10
Q

What can result in problems with neural tube formation?

A

Spinabifida

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11
Q

When does neural tube formation occur?

A

23 days post fertilisation

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12
Q

What is the structure of the notochord during neurulation?

A

Solid rod of cells running in midline

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13
Q

What is the role of the notochord in neurulation?

A

Signalling

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14
Q

Where does the notochord run?

A

Between ectoderm and endoderm

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15
Q

What is the result of the notochord running between the ectoderm and endoderm?

A

Signals can reach the ectoderm

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16
Q

What does the notochord direct?

A

Conversion of overlying ectoderm to neuroectoderm

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17
Q

How does ectoderm become neuroectoderm?

A

Differentiation

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18
Q

What is neuroectoderm?

A

A type of tissue that goes on to give the CNS

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19
Q

What do notochord signals cause?

A

Overlying ectoderm to thicken

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20
Q

What does the thickening of overlying ectoderm lead to?

A

Slipper-shaped neural plate

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21
Q

How is the neural tube formed for the neural plate?

A

The edges elevate out of the plane of the disk, and curl towards each other

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22
Q

What causes the edges of the plate to rise up?

A

The cells grow faster at the edge

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23
Q

What gives rise to the majority of tissues?

A

Mesoderm

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24
Q

What is required for the mesoderm to give rise to the majority of tissue?

A

Rapid differentiation

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25
What does mesoderm have lots of?
Discreet zones
26
What does each zone of the mesoderm have?
Separate tasks
27
What are the 4 types of mesoderm?
- Paraxial  - Intermediate - Somatic - Splanchnic
28
Where is paraxial mesoderm found?
Either side of the axis
29
What is the somatic mesoderm to do with?
Body, and body structures, including skeletal muscle
30
What is the splanchnic mesoderm to do with?
Viscera and organs
31
What exists in additional to the 4 types of mesoderm?
Intraembyronic coalom
32
What is intraembryonic coalom?
Spaces inside the embryo that form a new cavity
33
How is paraxial mesoderm organised?
Into segments
34
When do the first pair of somites appear?
Day 20
35
Where do the first pair of somites appear?
In the occipital region
36
What is the advantage of the first pair of somites being a very predictable presentation?
It can be used to age foetus
37
Where do more somites appear following the first?
The craniocaudal sequence
38
How quickly do more somites appear?
3 pairs a day
39
How many somites pairs are eventually present?
42 to 44
40
What happens to some of the somite pairs?
They disappear
41
What is the ultimate number of somite pairs?
31
42
How do somites appear?
As regular block of mesoderm cells arranged around a small cavity
43
What is the appearance of somites followed by?
‘Organised degradation’
44
What happens in organised degradation?
The ventral wall of somite breaks down
45
What does organised degradation lead to?
The formation of sclerotome
46
What does organised degradation represent?
A loss of a clearly defined block structure, but still kept very ordered
47
What does further organisation of dorsal portion form?
The dorsal dermomyotome
48
How does the dermomyotome differ from the sclerotome?
It is even more organised
49
What does the dorsal dermomyotome contribute to?
Formation of skin and muscular formation
50
What does the myotome do?
Proliferates and migrates
51
What does the dermotome do?
Disperses
52
What does the myotome and dermatome remain affiliated to?
The parent somite
53
What are somite derivatives the beginning of?
Development of musculoskeletal system
54
What is the dermatome?
‘Skin section’
55
What is the myotome?
‘Muscle section’
56
What is the sclerotome?
‘Hard tissue’ section
57
What is the implication of segmentation?
- Organisation of mesoderm into somites give rise to repeating structures  - Guides innervation
58
What repeating structures rise form somites?
- Vertebrae  - Ribs  - Intercostal muscles  - Spinal cord segments
59
What is the epimere innervated by?
Dorsal branch of spinal nerve for that segment
60
What is the hypomere innervated by?
Vental branch
61
What is the significance of there being 31 somites?
Means there a 31 segments and therefore 31 pairs of spinal nerves
62
Developmentally, what is the dermatome?
The part of the somite that gives rise to the dermis
63
Developmentally, what is the myotome?
Gives rise to the muscle
64
Clinically, what is the dermatome?
A strip of skin supplied by a single spinal nerve
65
Clinically,
A muscle/group of muscles supplied by a single spinal nerve
66
Clinically, what is the dermatome and myotome the basis of?
Examination of musculoskeletal and nervous systems
67
What does mesoderm differentiate into?
- Notochord - Paraxial  - Intermediate  - Somatic  - Splanchnic
68
What does the paraxial mesoderm develop into?
- The axial skeleton - Dermis  - Muscles of A/L body wall  - Some limb muscles
69
What does the axial skeleton consist of?
Vertebral column and ribs
70
What does the intermediate mesoderm develop into?
Urogenital system
71
What does the urogenital system consist of?
- Kidneys - Ureters  - Gonads
72
What does the somatic mesoderm develop into?
Connective tissue of limbs
73
What does the splanchnic mesoderm develop into?
- Smooth musculature  - Connective tissue  - Vasculature of gut
74
What will the buccopharyngeal membrane become?
The mouth
75
What will the cardiogenic area become?
The heart
76
Where on the embryonic disc is the cardiogenic zone of mesoderm?
Cranial end
77
What kind of folding does the embryonic disc undergo?
#NAME?
78
What is meant by cephalocaudal folding?
Folding at cranial (head) end and tail
79
What is cephalocaudal folding driven by?
Size of the neural tube
80
What is meant by lateral folding?
Folding of sides
81
What is lateral folding driven by?
Size of developing somite
82
What does folding create?
A pocket, with an opening into the umbilical cord
83
What is the result of of cephalocaudal folding?
A layer of mesoderm between ectoderm and endoderm, with future pericardial cavity next to it
84
What causes an expansion of the ectoderm?
The size of the neural tube
85
What does the expansion of the ectoderm do?
Pushes the head and tail under the layer of ectoderm, endoderm and mesoderm, leading to little pockets of yolk sac being pinched up into the embryonic body
86
What does the expansion of the amniotic sac downwards mean?
The whole embryo is wrapped in the amniotic sac, making sure whatever is facing outwards is ecroderm
87
What is the result of cephalocaudal folding on the heart?
It is now in the right place
88
What happens as the amniotic sac moves down?
- Get two ‘leaves’ at the lateral edges  | - Somites forming in paraxial mesoderm
89
What are the two ‘leaves’ at the lateral edges?
Somatic and splanchnic
90
What happens to the lateral edges of the disk?
They are forced down by growth of somites
91
What opens up between somatic and splanchnic layers?
Increasing space
92
What happens to the somatic and splanchnic ‘leaves’?
They develop downward, eventually meeting
93
What happens when the leaves meet?
They pinch off a bit of yolk sac
94
What is the result of the pinching off of yolk sac?
Results in cavity inside the embryo from the yolk sac
95
What does the cavity from the yolk sac allow for?
Development of systems
96
What does folding achieve?
- Draws together margins of disk  - Creates ventral body wall - Pulling amniotic membrane around disc, so embryo becomes suspended in it  - Pulling connective stalk ventrally  - Creates the primordium of the gut  - Puts heart and primordium of diaphragm in right place - Creates new cavity within embryo
97
Is the creation the ventral body wall an active or automatic process?
Active
98
What is the primordium of the gut created from?
The yolk sac

Z OLD Tissues of the Body (19 decks)

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