Week 2: Embryology Flashcards
(133 cards)
1
Q
Mammalian brains are all quite ____.
A
similar
2
Q
Provide some examples of mammals.
A
rats, mice, cats, primates
3
Q
Most experimental studies of the brain are done on which type of mammals?
A
rodents (rats/ mice)
4
Q
What are some key differences between the rat and human brain?
A
- convolutions (rat brain very small)
- size of cerebral hemispheres
5
Q
For the mostpart, the CNS of humans has ________ symmetry, meaning what?
A
bilateral symmetry.
This means the left and right hand sides are mirror images of each other; which is true for both the brain and spinal chord (for the most part, variation exists to small degree)
6
Q
Explain what is meant by the following general terms:
ipsilateral
A
structures which are on same side
ie. left eye is ipsilateral with left ear
7
Q
Explain what is meant by the following general terms:
contralateral
A
structures are on opposite sides
ie. left eye and right eye
8
Q
The whole of the CNS is derived from the walls of a ____ filled ____.
A
fluid filled tube
9
Q
The neural tube starts forming from what day post conception?
A
17/18
10
Q
What are the 3 primary germ layers?
A
endoderm
ectoderm
mesoderm
11
Q
What does the ectoderm form?
A
- epidermis
- hair
- nails
- nervous system
12
Q
What does the endoderm form?
A
-lining viscera (digestive, respiratory)
-
13
Q
What does the mesoderm form?
A
- CT (bones)
- muscle
14
Q
What are the alternative name(s) for the primitive nervous system? Why?
A
neuroectoderm
OR
neural plate.
The NS develops from the ectoderm, thus the NS primal form may be referred to as the neuroectoderm.
This primal form is essentially just a band of ectodermal tissue that gives rise to the NS. Thus it may also be referred to as a neural ‘plate’.
15
Q
Explain what is meant by the following general term(s):
neural plate
A
- flat sheet of cells
- forms by day 18 of embryo development
- initiated by notochord
- forms all neurophil
16
Q
Explain what is meant by the following general term(s):
neurophil
A
- neurons
- astrocytes
- oligodendrocyte
- ependymal cells
17
Q
The neural plate develops a neural groove, in a process known as _______.
A
neurulation
18
Q
Neurulation occurs by what day?
A
day 20
19
Q
Where does the neural groove exist?
A
Within the midline of neural plate, on the posterior surface.
20
Q
- (germ layer)
A
Endoderm
21
Q
- (germ layer)
A
Mesoderm
22
Q
- (germ layer)
A
Ectoderm
23
Q
1
A
Future Neural Crest
24
Q
2
A
Neural plate and groove
25
3
Ectoderm
26
4
Mesoderm
27
5
Notochordal plate
28
6
Endoderm
29
At what day of embrological development would you expect this to be? why?
Day 18. Because the neural groove has not formed yet, the germ layers are still "flat" rather than forming the proper tube structure that will occur in the following days.
30
At what day of embryological development would you expect this to be? why?
Day 20. Because neuralation has occured; you can clearly distinguish the neural groove but no somites are present yet.
31
At what day of embryological development would you expect this to be? why?
day 21. Neurelation has occured AND development of somites has begun.
32
2
Neural groove
33
4
Mesoderm
34
5
Notochord
35
6
Endoderm
36
2
Neural tube
37
3
Neural Crest
38
1
Ectoderm
39
2
Neural Fold
40
3
Mesoderm
41
5
Endoderm
42
A
Rostral
43
B
Caudal
44
1
Prosencephalon
45
2
Mesencephalon
46
3
Rhombencephalon
47
4
Spinal Cord
48
Explain what is going on in this image
Neural Crest cells are migrating from a rostral to caudal/lateral direction to eventually form the cell types for the:
- Sensory neurons in spinal & some cranial nerve ganglia (CN V, VII, VIII, IX, X)
- Postganglionic neurons of ANS
- Schwann cells of PNS
- Adrenal medulla
- Some cartilage, bone and connective tissue
- pigment cells
49
1
Spinal Cord
50
2
Myencephalon
51
3
Metencephalon
52
4
Mesencephalon
53
5
Diencephalon
54
6
Telencephalon
55
7
Cervicle flexure
56
8
Cephalic flexure
57
9
pontine flexure
58
1
Forebrain
59
2
Telencephalic vesicles
60
3
Diencephalon
61
4
Optic vessicles
62
5
Midbrain
63
6
Hindbrain
64
Explain what is happening in this image.
The disproportionate growth of cortex is creating a c-shape
65
4
Cerebellum
66
5
Fourth ventricle
67
6
Pons
68
4
Tectum
69
5
Cerebral Aquaduct
70
6
Tegmentum
71
4
Fourth ventricle
72
5
Medulla
73
6
Medullary pyramids
74
1
Epyndyma
75
2 (what is it and what will it become)
Alar plate: will become dorsal horn
76
3
Sulcus Limitans
77
4 (what is it and what will it become)
Basal Plate: Will become ventral horn
78
How does the neural groove deepen?
as the neural plate folds inwards
79
After the neural fold deepens, the walls of the neural groove begin to form whats known as _____ \_\_\_\_\_.
neural folds.
80
Briefly explain how & when the neural tube develops?
By day 22, the neural folds fuse together dorsally.
This occurs for the most of the length EXCEPT the very cranial and very caudial ends of the tube (the far ends).
81
The neural folds dont fuse together at the very cranial and very caudal ends of the neural tube, allowing the formation of unclosed sections called what?
Neuropores.
82
The cranial neuropore closes by which day?
24
83
The caudal neuropore closes by which day?
26
84
The entire CNS develops from the walls of what?
The walls of the neural tube.
85
Which end of the neural tube develops into the brain?
Rostral end
86
Aside from the rostral end, the rest of the neural tube develops into what?
The spinal cord.
87
The lumen of the neural tube develops into into what 2 structures?
1. ventricles of the brain
2. central canal of the spinal chord
88
Explain what is meant by the following general terms:
neural crest cells
neural crest cells develop during neural tube fusion, towards the top (crest) of the neural tube. These cells dissociate from the tube and subsequently migrate away from it laterally.
ALL neurons with cells in the PNS develop from these neural crest cells - that is, neural crest cells are the origin of the PNS.
89
The population of neural crest cells may be... (3)
1. transient
2. multipotent
3. migratory
90
Neural crest cells may become one of 5 different cell types. What are these 5 cell types?
1. melanocytes
2. craniofacial cartilage and bone
3. smooth muscle
4. peripheral and enteric neurons
5. glia
91
Neural crest cells develop in close association with the underlying \_\_\_\_\_\_\_\_.
mesoderm
92
What are somites? What may somites develop into?
Somites are parts of the mesoderm (specifically they are the paraxial mesoderm), which bulge around on either side of the neural tube. Somites develop into...
1. 33 individual vertebrae of spinal cord
2. includes related skeletal muscle
3. includes nerves that innervate this muscle
93
In what way are somites vital to the organisation of vertebrate embryos?
Somites are responsible for organising the **segmental nature** of vertebrate embryos.
94
In which week does brain development begin?
Fourth.
95
Brain development begins by the fourth week. This development includes...
a. ) Enlargements -
b. ) Bends -
a. ) Enlargements - vesicles
b. ) Bends - flexures
96
The primary vesicles develop at the _____ end of the neural tube.
rostral
97
What are the 3 primary vesicles, and what region of brain do they develop into?
1. prosencephalon - forebrain
2. mesencephalon - midbrain
3. rhombencephalon - hindbrain, merges with spinal cord component of neural tube
98
The entire brain is derived from the _ \_\_\_\_ \_\_\_\_
3 primary vesicles.
99
When do secondary vesicles develop?
5th week
100
In general, where do secondary vesicles develop?
as off shoots of the primary vesicles
101
Secondary vesicles develop as off shoots of the primary vesicles. What are the secondary vesicles developing off of the prosencephalon?
1. Telencephalon
2. Diencephalon
102
Secondary vesicles develop as off shoots of the primary vesicles. What are the secondary vesicles developing off of the mesencephalon?
1. Mesencephalon (same name)
103
Secondary vesicles develop as off shoots of the primary vesicles. What are the secondary vesicles developing off of the rhombencephalon?
1. Myelencephalon
2. Metencephalon
104
In total, how many secondary vesicles exist?
5
105
By which week does a prominent cephalic flexure form? At what level does this form?
3rd week; level of mesencephalon
106
By which week does a second, cervical flexure appear?
5th
107
The second, cervical flexure appears by the 5th week. Where does this cervical flexure appear?
At the boundary between the hindbrain and spinal cord.
108
What is the third flexure called? By what week does it develop?
The third flexure is the pontine flexure, which develops by week 7.
109
The pontine flexure is the third to develop, and it develops in week 7. Where does the pontine flexure appear?
between the metencephalon and the myelencephalon.
110
The neural tube becomes what 3 structures?
The primary vesicles...
prosencephalon,
mesencephalon, &
rhombencephalon
111
The prosencephalon (primary vesicle) develops into the telencephalon and diencephalon (secondary vesicles). What does the telencephalon become?
The cerebral hemispheres AND telencephalic vesicles also give rise to optic vesicles, which subsequently form optic stalks and cups, and eventually optic nerves and retina.
112
The prosencephalon (primary vesicle) develops into the telencephalon and diencephalon (secondary vesicles). What does the diencephalon become?
- thalamus
- hypothalamus
- epithalamus
- subthalamus
113
The mesencephalon (as a secondary vesicle) becomes what?
The midbrain.
114
The rhombencephalon (primary vesicle) becomes the metencephalon and myelencephalon (secondary vesicles). What does the metencephalon become?
- pons
- cerebellum
115
The rhombencephalon (primary vesicle) becomes the metencephalon and myelencephalon (secondary vesicles). What does the myelencephalon become?
The medulla.
116
Are the optic nerves and retina part of the CNS or PNS?
CNS
117
Do telencephalonic vesicles grow anteriorly or posteriorly?
posteriorly
118
Are telencephalic vesicles lateral or medial to diencephalic?
lateral
119
Another vesicle pair bud off the ventral surface of the cerebral hemispheres. What do these form?
olfactory bulbs and other smell related structures.
120
Cells of the telencephalon wall divide and differentiate into many structures. Amongst these, ____ \_\_\_\_ systems develop, which carry axons to and from the neurons of the telencephalon.
white matter
121
Explain the position of the telencephalon relative to the diencephalon.
The telencephalon is found lateral to the diencephalon. The telencephalon expands over and covers the diencephalon.
122
Explain what is meant by the following general term(s):
ventricle
fluid filled space
123
Where are lateral ventricles of the brain found?
Within the cerebral hemispheres.
124
Where is the third ventricle of the brain found?
Within the centre of the diencephalon.
125
Briefly explain the shape/ structure of the third venrtricle.
Elongated; slit like.
126
As the telencephalon proliferates, 2 different types of gray matter develop become apparent. What are these?
(note: this is regarding gray matter which has developed from the TELENCEPHALON ONLY! The diencephalonic gray matter is different)
1. cerebral cortex (superficial gray matter)
2. basal telencephalon (deep gray matter)
127
The diencephalon differentiates into 2 types of gray matter, what are these structures?
1. thalamus
2. hypothalamus
128
Cortical white matter involves ____ major white matter systems.
What are these systems?
3.
1. cortical white matter
2. corpus callosum
3. internal capsule
129
Cortical white matter involves 3 major white matter systems - one of these is the cortical white matter system. Elaborate on this.
Simply the myelinated axons between neurons in the cerebral cortex (superficial; however not more superficial then the layer of gray matter in cerebral cortex).
130
Cortical white matter involves 3 major white matter systems - one of these is the corpus callosum. Elaborate on this.
- links neurons between cerebral hemispheres
- continuous with cortical white matter
- an 'axon bridge'.
131
Cortical white matter involves 3 major white matter systems - one of these is the internal capsule. Elaborate on this.
- continuos with cortical white matter
- links cortex to brainstem (thalamus)
132
t/f: the optic vesicle is a secondary vesicle which sprouts off of the prosencephalon
true
133
By what day of embryological development does the neural tube form?
17/ 18.
