أسئلة المحاضرة السابعة امبريولوجي (قبل التعديل)

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Questions and Answers

What is the process that leads to the development of the nervous system during the third week of development?

Neurulation (correct)

Folding

Primitive streak formation

Gastrulation

Which part of the ectoderm thickens to form the neural plate during neurulation?

Mesoderm

Lateral margins of the ectoderm

Central ectoderm (correct)

Peripheral ectoderm

What closes on the 27th day of development during neurulation?

Neural plate

Caudal neuropore (correct)

Cranial neuropore

Neural tube

Which of the following structures develops from the neural crest cells?

Ganglia Signup and view all the answers

Which anomaly is caused by the failure of closure of the cranial neuropore?

Anencephaly Signup and view all the answers

What is the effect of folic acid supplementation during pregnancy related to neural tube defects?

Prevents 70% of defects Signup and view all the answers

What is the main driving force behind embryonic folding during the fourth week?

Rapid growth of the neural tube Signup and view all the answers

Which diagnostic methods are used to identify neural tube defects?

Alpha-fetoprotein levels and ultrasound Signup and view all the answers

What role does the notochord play during neurulation?

It induces the formation of the neural plate. Signup and view all the answers

Which structure is formed when neural folds fuse during neural development?

Neural tube Signup and view all the answers

What characterizes spina bifida occulta among the types of spina bifida?

It is typically asymptomatic. Signup and view all the answers

At what stage does the cranial neuropore closure occur?

On the 25th day Signup and view all the answers

Which neural crest cell derivative is involved in pigment production?

Melanocytes Signup and view all the answers

What is the primary consequence of anencephaly resulting from neural tube defects?

Absent skull and most brain parts Signup and view all the answers

What triggers the rapid growth that leads to embryonic folding during the fourth week?

Development of the neural tube and mesoderm Signup and view all the answers

Which of the following conditions is known to help prevent neural tube defects during pregnancy?

Folic acid supplementation Signup and view all the answers

Explain the role of the notochord in the process of neurulation.

The notochord acts as an inducer for neurulation, signaling the ectoderm to thicken and form the neural plate. Signup and view all the answers

Describe one key structural change that occurs during the fusion of neural folds.

During the fusion, the elevated edges of the neural plate converge and form the neural tube. Signup and view all the answers

What is a critical time frame for the closure of the caudal neuropore and its significance?

The caudal neuropore closes on the 27th day, and its closure is crucial to prevent defects in the lower spinal cord. Signup and view all the answers

Identify the types of spina bifida and their primary distinction.

Spina bifida can be classified as occulta, meningocele, or meningomyelocele, with occulta being asymptomatic. Signup and view all the answers

Which nutrients are suggested to help mitigate neural tube defects, and how do they function?

Folic acid (vitamin B9) supplementation helps prevent neural tube defects by promoting proper neural tube closure. Signup and view all the answers

Summarize the consequences of anencephaly and its developmental basis.

Anencephaly results in the absence of a skull and brain parts due to the failure of cranial neuropore closure. Signup and view all the answers

Discuss how embryonic folding occurs and its significance in development.

Embryonic folding occurs as the trilaminar embryo folds ventrally due to the rapid growth of the neural tube and mesoderm. Signup and view all the answers

What are the derivatives of the neural crest cells and their functions?

Neural crest cells give rise to ganglia, Schwann cells, and melanocytes, serving functions such as nerve signal transmission and pigmentation. Signup and view all the answers

What role do neural crest cells play during embryonic development?

Neural crest cells give rise to various structures, including ganglia, Schwann cells, and melanocytes. Signup and view all the answers

What anatomical change occurs during the process of neurulation?

During neurulation, the neural plate elevates to form neural folds and creates a neural groove. Signup and view all the answers

How does spina bifida manifest, and what are its causes?

Spina bifida is characterized by incomplete closure of the caudal neuropore, leading to spinal cord defects. Signup and view all the answers

What condition results from the failure of the cranial neuropore to close?

Anencephaly results from this failure, leading to the absence of most of the brain. Signup and view all the answers

What is the significance of the notochord during neurulation?

The notochord acts as an inducer for neurulation, signaling the ectoderm to thicken and form the neural plate. Signup and view all the answers

In what time frame does the cranial neuropore close, and why is this significant?

The cranial neuropore closes on the 25th day of development, marking the completion of an essential stage in neural development. Signup and view all the answers

What role does folic acid play in preventing neural tube defects?

Folic acid supplementation during pregnancy can prevent approximately 70% of neural tube defects. Signup and view all the answers

Describe one potential outcome of a neural tube defect detected during pregnancy.

One outcome could be the diagnosis of spina bifida through elevated alpha-fetoprotein levels. Signup and view all the answers

Study Notes

Neurulation and Folding

Neurulation is the development of the nervous system
The notochord induces neurulation
Primitive streak formation occurs between days 15 and 16
Gastrulation follows primitive streak formation
Notochord forms
Three germ layers differentiate
Ectoderm thickens to form neural plate
Neural folds form from the edges of the neural plate
Neural folds fuse in the craniocaudal direction to form neural tube
Neural crest is a lateral portion of the neural plate

Fate of Neural tube

Cranial neuropore closes on day 25
Caudal neuropore closes on day 27
Upper part of the neural tube forms brain vesicles
Lower part elongates to form spinal cord

Neural Crest Cells

Form various structures including ganglia, pia and arachnoid mater, Schwann cells, chromaffin cells, and melanocytes

Neurulation Anomalies

Anencephaly: Failure of the cranial neuropore to close, resulting in absent skull and brain parts. Incompatible with life.
Spina Bifida: Incomplete closure of the caudal neuropore. Classified into occulta (asymptomatic), meningocele, and meningomyelocele.
Diagnosis: Elevated alpha-fetoprotein levels and ultrasound.
Prevention: Folic acid (vitamin B9) supplementation during pregnancy can prevent 70% of neural tube defects.

Embryonic Folding

Occurs during the fourth week
The cause is rapid growth of the developing neural tube and paraxial mesoderm
The amniotic cavity expands and surrounds the embryo
The yolk sac is constricted into the primitive gut and definitive yolk sac
The connection between the primitive gut and definitive yolk sac is the vitellointestinal duct
Results:
- Foregut develops in head folds
- Midgut develops in lateral folds
- Hindgut develops in tail folds
- Yolk sac and Vitello intestinal duct degenerate
- Lateral body folds fuse to form ventral abdominal wall.

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