Embryology 1 Flashcards
1
Q
What does the NS form from?
A
The ectoderm.
2
Q
What does the musculoskeletal system form from?
A
The mesoderm.
3
Q
What process occurs after gastrulation?
A
Neurulation.
4
Q
What is neurulation?
A
The formation of the neural tube from the ectoderm.
5
Q
What will the neural tube become?
A
The brain and spinal cord of the CNS.
6
Q
How does the embryo know when to begin neurulation?
A
Factors will be produced by the notochord that will induce ectoderm folding.
7
Q
What is the notochord?
A
A midline rod in the mesoderm.
8
Q
What are the steps of neurulation?
A
- Neuroectoderm cells will migrate towards the center and form a thick neural plate
- These cells will proliferate, causing the neural plate to buckle. This forms a neural groove with lateral neural folds
- Cells continue to proliferate until the ends fuse at the dorsal midline
- Fusion begins at the cervical region and will occur bidirectionally towards the cranial and caudal ends
- At the cranial and caudal ends, there are areas that are unfused called neuropore
- Neuropores will close at the end of Week 4
- Neuroepithelium cells will proliferate and differentiate into neurons and neuroglia of the CNS
9
Q
Where do the neural crest cells detach from?
A
They detach from the dorsolateral edges of the neural tube.
10
Q
What do the neural crest cells eventually form?
A
The neural crest cells will form the neurons and neuroglia of the PNS.
11
Q
What do neural tube defects result from?
A
The failure of neuropore fusion at the end of week 4.
12
Q
How can these defects be prevented?
A
Folic acid in diet.
13
Q
What do neural tube defects result in?
A
Abnormal development of skull and vertebrae from the mesoderm.
14
Q
Failure of the cranial neuropore to fuse results in?
A
Anencephaly.
15
Q
Failure of the caudal neuropore to fuse results in?
A
Spina bifida.
16
Q
What are the defects of spina bifida?
A
Defects in the vertebral arches of L4-S1.
17
Q
What is spina bifida occulta?
A
Spina bifida occulta is when there are defects in the vertebral arches covered by skin WITHOUT the involvement of the neural tissue.
18
Q
What is spina bifida cystica?
A
Spina bifida cystica is when there are defects in the vertebral arches WITH the involvement of the neural tissue.
19
Q
What is spina bifida cystica w/ meningocele?
A
Protusion of the meninges.
20
Q
What is spina bifida cystica w/ meningomyelocele?
A
Protusions of the meninges and the neural tissue.
21
Q
What is spina bifida cystica w/ rachischisis?
A
Permanently damaged neural tissue due to the amniotic fluid.
22
Q
The spinal cord will develop from what end of the neural tube?
A
The caudal end of the neural tube.
23
Q
In a 3 month old fetus, the spinal cord is equal to the length of the…
A
Vertebral column.
24
Q
In a 3 month old fetus, the spinal nerves will exit..
A
At the same level of their spinal cord origin.
25
In 3 month + fetus to adult, the spinal cord is ________ compared to the vertebral column.
Shorter.
26
In 3 month old + fetus to adult, the spinal nerves will exit...
At a level inferior of their spinal cord origin.
27
In newborns, the conus medullaris is located at..
L3-L4
28
In children and adults, the conus medullaris is located at...
L1-L2
29
What are the precursors to the spinal cord neurons?
The neuroblasts.
30
What is one main feature of neuroblasts?
Once they differentiate from the neuroepithelium, they are unable to divide.
31
Neuroblasts will migrate to the...
Mantle layer.
32
Where is the mantle layer located?
Superficial to the neuroepithelium layer.
33
The alar plate of the mantle layer will become...
The dorsal horn of the spinal cord grey matter (sensory).
34
The basal plate of the mantle layer will become...
The ventral and lateral horns of the spinal cord grey matter (motor).
35
The marginal layer with myelinated processes of the neurons will form...
The white matter.
36
What does the dorsal root ganglion contain?
The DRG contains the cell bodies of sensory neurons.
37
These sensory neurons in the DRG send out 2 processes...
1 process goes to the CNS (centrally located) and the other process goes to the sensory receptors (peripherally located).
38
The dorsal sensory root contains..
The centrally located process to the CNS.
39
What does the autonomic ganglion contain?
The autonomic ganglion contains the cell bodies of the postsynaptic parasympathetic and sympathetic motor neurons.
40
What does the ventral root normally contain?
The ventral root normally contains the somatic motor neurons from the ventral horn.
41
In the thoracolumbar region, what does the ventral root contain?
The ventral root will contain the presynaptic sympathetic motor neurons from the lateral horn.
42
What is the musculoskeletal system composed of?
Skeletal muscle and connective tissue.
43
What are the two types of connective tissue?
1. Connective tissue proper
| 2. Specialized connective tissue
44
What are the components of connective tissue proper?
Dermis, tendon, and ligament.
45
What are the components of the specialized connective tissue?
Bone and cartilage.
46
What is mesenchyme?
Mesenchyme is immature embryonic connective tissue that will give rise to all connective tissue cells.
47
What is a good explanation of the innervation of muscles in the upper and lower limbs?
The nerves follow the course of the migrating myotome cells.
48
Where do the sclerotome mesenchymal cells migrate to?
The sclerotome mesenchymal cells will migrate to surround the notochord and the neural tube.
49
What do the vertebrae develop from?
The vertebrae develop from the sclerotome of adjacent somites.
50
What happens to the sclerotomes of adjacent somites?
The sclerotomes will split and recombine.
51
What happens to the cells at the region where the sclerotomes split and what will they form?
These cells will encircle around the notochord and form the annulus fibrosus.
52
What does the notochord form?
The notochord will form the nucleus pulposus.
53
What do the mesenchymal cells of the vertebrae form first?
They form hyaline cartilage from the chondroblasts.
54
What happens to the hyaline cartilage model?
The hyaline cartilage model is then replaced by the bone via endochondral ossification.
55
What are the ribs derived from?
The ribs are derived from sclerotome cells.
56
How many pairs of costal processes are there?
There are 12 pairs of costal processes.
57
What does the sternum develop from?
The sternum develops from the somatic mesoderm.
58
What do the ribs fuse with as they grow towards the ventral midline?
The ribs fuse with the costal cartilage.
59
What type of ossification forms the ribs and the sternum?
Endochondral ossification.
60
What is thoracic outlet syndrome?
Thoracic outlet syndrome is having an extra rib on C7.
61
What are the effects of having an extra rib?
An extra rib may impinge on the nerve or arteries of the upper limb.
62
What does cleft sternum result from?
Cleft sternum results from the incomplete fusion of the the sternal mesenchyme bars.
63
What is the effect of the cleft sternum?
The heart is less protected.
64
What are most of the flat bones of the skull derived from?
The flat bones of the skull are derived from somite mesoderm.
65
What type of ossification leads to the formation of the flat bones of the skull?
Intramembranous ossification.
66
The limb buds project from the _________________ body wall.
Anterolateral body wall.
67
The mesenchyme of the limb bud originates from what mesoderm?
Somatic mesoderm.
68
The myoblast cells of the limb bud originate from what mesoderm?
Somite mesoderm.
69
What type of ossification forms the skeleton of the limbs?
Endochondral ossification.
70
What forms the dermis of the developing skin?
The somite dermatome and the somatic mesoderm.
71
What forms the epidermis and epidermal derivatives (hair, nails, and sweat glands)?
Ectoderm.
72
What forms the dermis CT in the face and neck?
Neural crest cells form the mesenchyme that will become the dermis of face and neck.
73
What mesoderm are skeletal muscles derived from?
Skeletal muscles are derived from paraxial mesoderm --> somite mesoderm --> myotome.
74
What are myotomes composed of?
Myotomes are made of myoblasts.
75
Myoblasts will either...
Stay put in the somite mesoderm or migrate to the somatic mesoderm.
76
The myoblasts that stay put are called?
Primaxial.
77
The myoblasts that migrate are called?
Abaxial.
78
The primaxial muscles include?
The back and shoulder muscles.
79
The abaxial muscles include?
The limb muscles.
80
Myoblasts will fuse to form a?
Syncytium.
81
What is the function of satellite cells?
Satellite cells serve as stem cells and provide limited regeneration for skeletal muscle.
82
What is Poland's sequence?
Poland's sequence is missing the pectoral muscle.
83
What are the effects of Poland's sequence?
Flat pectoral region, unpleasant is displaced, and missing anterior axillary fold.
84
What is prune belly syndrome?
Absence of abdominal muscles.
85
What is lateral embryonic folding?
Lateral folding is when the lateral ends of the flat embryo fuse ventrally.
86
The lateral folding of the embryo results in...
Two tubes: a gut and a neural tube.
87
What is cephalo-caudal folding?
Cephalo-caudal folding is when the flat embryo folds into a C-shape.
88
What is ectopia cordis?
Incomplete fusion of the thorax resulting in the heart on the outside.
89
Limbs develop in what direction?
A proximal to distal direction.
90
What is the apical ectodermal ridge?
The apical ectodermal ridge is a thick region of ectoderm surface cells at the distal end of the limb.
91
What is the function of the AER?
The AER will produce factors that signal to the mesenchyme to proliferate rapidly without differentiating.
92
What is the area of mesenchyme proliferation called?
The progress zone.
93
What happens to the cells that are further away from the AER?
These cells will differentiate into cartilage and bone.
94
What is responsible for the formation of a pinky and thumb side?
The zone of polarizing activity (ZPA).
95
The further away from ZPA, the more you'll have the...
Thumb side.
96
At birth, the ______ of bones are completely ossified.
Diaphyses of bones.
97
What is achondroplasia?
Achondroplasia is reduced chondrocyte proliferation resulting in shortened limb bones and premature closure of growth plates.
