Embryology Chapter 6: Facial Development

Questions and Answers

What structures constitute the primary palate?

Two maxillary and two medial nasal processes (correct)

Frontonasal prominence and two mandibles

Two maxillary and two lateral nasal processes

Two medial nasal processes and the palatine uvula

During which weeks of development does the secondary palate form?

Between the 8th and 10th weeks

Between the 6th and 8th weeks (correct)

Between the 4th and 6th weeks

Between the 10th and 12th weeks

What is the role of cranial neural crest cells in facial development?

They contribute to the formation of facial prominences (correct)

They form the primary palate only

They are involved in the fusion of the palate only

They create the nasal pits exclusively

What is formed when the lateral and medial nasal processes fuse?

Nostril Signup and view all the answers

How is the definitive palate formed?

From the primary and secondary palates together Signup and view all the answers

At what point in development does the palate begin to form?

At the end of the 5th week Signup and view all the answers

Which time period is most critical for palate development?

From the end of 6th week to the beginning of 9th week Signup and view all the answers

What is the primary palate developed from?

The intermaxillary segment Signup and view all the answers

Where does the secondary palate develop from?

The internal aspect of the maxillary processes Signup and view all the answers

What anatomical part lies behind the premaxillary part of the maxilla?

Primary palate Signup and view all the answers

During which weeks do the lateral palatine processes elongate and ascend to a horizontal position above the tongue?

7th and 8th weeks Signup and view all the answers

What structure do the lateral palatine processes fuse with during their development?

The posterior part of the primary palate Signup and view all the answers

When does fusion with the nasal septum begin and complete during fetal development?

Begins in the 9th week and completes by the 12th week Signup and view all the answers

What is primarily responsible for the changes in the appearance of the face during the fetal period?

Changes in the proportion and positioning of facial structures Signup and view all the answers

Which of the following is considered a craniofacial anomaly?

Cleft lip and palate Signup and view all the answers

What results from the failure of the medial nasal prominences to merge?

Cleft lip Signup and view all the answers

Which type of cleft results from the maxillary prominence failing to fuse with the lateral nasal prominence?

Oblique facial cleft Signup and view all the answers

What is a common result of cleft palate?

Swallowing difficulties Signup and view all the answers

Which cleft involves both the lip and palate?

Cleft lip and palate Signup and view all the answers

Which cleft type is characterized by the failure of maxillary prominences to meet on both sides?

Bilateral cleft lip Signup and view all the answers

What generally does not result from a cleft lip?

Difficulty in chewing Signup and view all the answers

What type of cleft leaves the nasal and oral cavities connected?

Cleft palate Signup and view all the answers

What cleft arises specifically from the failure of the maxillary prominence to merge with the medial nasal prominence on one side?

Unilateral cleft lip Signup and view all the answers

Study Notes

Development of Facial Structure

Development of the face in mammals originates from five facial prominences around the primitive mouth: frontonasal, maxillary (two), and mandibular (two).
Cranial neural crest cells, which migrate from the dorsal edge of the rostral neural tube, populate these facial prominences.
The frontonasal prominence divides into medial and lateral nasal processes due to the formation of nasal pits.
Fusion of lateral and medial nasal processes leads to nostril formation and the upper lip forms where medial nasal processes meet maxillary prominences.

Palate Development

The palate separates the nasal and oral cavities, consisting of the primary and secondary palate.
The primary palate is formed by the maxillary and medial nasal processes and begins development in the 6th week, completing by the 12th week.
Secondary palate forms between the 6th and 8th weeks from lateral palatine processes of the maxillary processes, eventually creating bilateral fusion to form the definitive palate.

Critical Periods

The main development of the palate occurs from the end of the 6th week to the beginning of the 9th week.
The primary palate represents a small portion of the adult hard palate, lying anterior to the incisive fossa.

Changes During Fetal Period

Changes in facial proportions and positioning occur during the fetal period, resulting in a prominent forehead and characteristic features.
Nasal and mandibular structures undergo significant changes; initially flat noses become shaped, and the mandible develops further.
The enlargement of the brain influences the movement of the eyes medially and the ascent of the ears.

Craniofacial Anomalies

Craniofacial anomalies are congenital deformities affecting the head and facial bones, varying from mild to severe.
Common examples include cleft lip and palate, caused by improper fusion of embryonic facial prominences, leading to issues in breathing, feeding, swallowing, and speech.
Types of cleft conditions include median cleft lip, unilateral cleft lip, bilateral cleft lip, oblique facial cleft, and cleft palate, each resulting from distinct developmental failures.
Unilateral and bilateral cleft lips occur due to failure of maxillary prominence fusion with the medial nasal prominence on one or both sides, respectively. Oblique facial clefts arise from the lack of fusion with the lateral nasal prominence.

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Description

This quiz covers the key concepts of facial development in mammals as detailed in Chapter 6 of embryology. It focuses on the formation of the five facial prominences and the role of cranial neural crest cells during this critical phase of morphology. Test your understanding and retention of these foundational concepts in embryonic development.