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Questions and Answers
What structures contribute to the formation of the upper jaw and cheeks during facial development in the sixth week?
What structures contribute to the formation of the upper jaw and cheeks during facial development in the sixth week?
What role does the foramen ovale play in fetal circulation during the sixth week of embryonic development?
What role does the foramen ovale play in fetal circulation during the sixth week of embryonic development?
Which process is essential for the separation of digits in limb development during the sixth week?
Which process is essential for the separation of digits in limb development during the sixth week?
During the sixth week, what is the main anatomical change that occurs in the cardiac development?
During the sixth week, what is the main anatomical change that occurs in the cardiac development?
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What does the emergence of nasal pits indicate during the sixth week of embryonic development?
What does the emergence of nasal pits indicate during the sixth week of embryonic development?
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What is developed by the merging of the mandibular processes during facial development in week six?
What is developed by the merging of the mandibular processes during facial development in week six?
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What characterizes the heartbeat detection process during the sixth week?
What characterizes the heartbeat detection process during the sixth week?
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What developmental process indicates the beginning of segmentation for fingers in the limb buds during week six?
What developmental process indicates the beginning of segmentation for fingers in the limb buds during week six?
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What significant change occurs at week 6 in the development of upper limb buds?
What significant change occurs at week 6 in the development of upper limb buds?
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What is the purpose of apoptosis in the interdigital regions of the upper limbs?
What is the purpose of apoptosis in the interdigital regions of the upper limbs?
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Which of the following events is first observed in the upper limb development before lower limbs?
Which of the following events is first observed in the upper limb development before lower limbs?
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What do digital rays in the hand plates signify?
What do digital rays in the hand plates signify?
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At week 6, what is the overall status of the lower limb development compared to the upper limbs?
At week 6, what is the overall status of the lower limb development compared to the upper limbs?
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What critical feature do hand plates provide for future limb development?
What critical feature do hand plates provide for future limb development?
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What occurs as a result of the midgut's elongation at week 6?
What occurs as a result of the midgut's elongation at week 6?
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What does the term 'foot plates' refer to in lower limb development?
What does the term 'foot plates' refer to in lower limb development?
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What does the cranial limb of the midgut loop develop into?
What does the cranial limb of the midgut loop develop into?
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What is the direction of the initial rotation of the midgut loop?
What is the direction of the initial rotation of the midgut loop?
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Which structure remains connected to the herniated loop during its development?
Which structure remains connected to the herniated loop during its development?
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What eventually happens to the caudal limb of the midgut?
What eventually happens to the caudal limb of the midgut?
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During the herniation of the midgut, where does the midgut bulge into?
During the herniation of the midgut, where does the midgut bulge into?
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What is the significance of the rotation of the midgut loop?
What is the significance of the rotation of the midgut loop?
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During which week does the herniation of the midgut typically occur?
During which week does the herniation of the midgut typically occur?
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What role does the vitelline duct play during midgut development?
What role does the vitelline duct play during midgut development?
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Study Notes
Human Embryology - Week 6
- The sixth week of embryonic development brings significant changes, including the growth of pharyngeal arches (nasal, maxillary, and mandibular processes).
- Cardiac morphogenesis is crucial, involving atrial and ventricular septation.
- The foramen ovale plays a role in fetal circulation.
- Hand and foot plates form, and apoptosis sculpts digits, crucial for upper limb differentiation.
- Herniation of the midgut occurs accommodating rapid growth.
- Cranial and caudal limbs form, contributing to the development of the small and large intestines.
Facial Development - Week 6
- Facial features undergo rapid morphological changes in the face, influenced by the pharyngeal arches.
- Key components are the frontonasal prominence, maxillary, and mandibular processes.
- Nasal pits originate as depressions on the frontonasal prominence, developing into nasal cavities.
- Surrounding mesenchymal tissue forms nasal structures.
- Maxillary processes grow medially to form the upper jaw and cheeks.
- Mandibular processes merge to form the lower jaw and chin.
Cardiac Development - Week 6
- The heart continues morphogenesis, becoming more complex structurally.
- Atrial septation occurs, with the septum primum and septum secundum refining the separation between the right and left atria.
- A notable structure, the foramen ovale, assists fetal blood flow by bypassing the non-functional fetal lungs.
- Ventricular septum develops, dividing the ventricles into right and left chambers.
- Ultrasound can detect coordinated heart contractions, typically around 100–160 beats per minute during transvaginal scans.
Limb Differentiation - Week 6
- Limb buds become more defined, and finger segmentation begins.
- Hand plates form from the distal ends of upper limb buds, flattening into paddle-like structures.
- These are precursors to hands.
- Digital rays (thickened ridges) emerge in the hand plates, marking the future fingers.
- Apoptosis shapes digits.
- Lower limbs show initial signs of elongation and differentiation; they lag behind upper limb development.
- Foot plates form, acting as precursors to the feet..
Midgut Development - Week 6
- Midgut elongates, forming a loop that temporarily protrudes into the umbilical cord to accommodate rapid growth due to its insufficient abdominal space.
- This protrusion connects to the yolk sac via the vitelline duct.
- Cranial limb of the midgut forms parts of the small intestine (duodenum, jejunum, and ileum). This segment is critical for nutrient absorption and digestive function.
- Caudal limb forms parts of the large intestine (cecum, appendix, and colon). This part deals with water absorption and fecal matter formation.
- Midgut loops rotate 90 degrees counterclockwise around the superior mesenteric artery, positioning the small and large intestines correctly within the abdominal cavity.
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Description
Explore the significant changes during the sixth week of embryonic development, including the growth of pharyngeal arches and cardiac morphogenesis. This week is vital for the formation of facial features, hand and foot plates, and the development of the gastrointestinal tract. Discover how these changes set the stage for further differentiation in the embryo.
