Podcast
Questions and Answers
During which day of gestation in the dog are the optic sulci visible?
During which day of gestation in the dog are the optic sulci visible?
- Day 17
- Day 13 (correct)
- Day 19
- Day 15
What happens concurrently with the transformation from optic sulcus to optic vesicle in the dog?
What happens concurrently with the transformation from optic sulcus to optic vesicle in the dog?
- Enlargement of the optic vesicle
- Closure of the neural tube (correct)
- Development of the optic stalk
- Formation of the lens placode
What is the role of the optic vesicle in the development of the dog's palpebral fissure and orbital structures?
What is the role of the optic vesicle in the development of the dog's palpebral fissure and orbital structures?
- Enlargement of the optic vesicle
- Formation of the lens placode
- Invagination through differential growth
- Induction and size determination (correct)
Which structure develops from mesenchyme in the optic fissure?
Which structure develops from mesenchyme in the optic fissure?
What happens if the optic fissure fails to close normally?
What happens if the optic fissure fails to close normally?
What is the role of the optic vesicle in lens formation?
What is the role of the optic vesicle in lens formation?
What is the initial event leading to the formation of the chambers of the ocular anterior segment?
What is the initial event leading to the formation of the chambers of the ocular anterior segment?
Which structure surrounds the lens vesicle and will become the lens capsule?
Which structure surrounds the lens vesicle and will become the lens capsule?
What is the embryonic lens nucleus composed of in the adult?
What is the embryonic lens nucleus composed of in the adult?
What continues to develop from the anterior cuboidal epithelial cells in the lens?
What continues to develop from the anterior cuboidal epithelial cells in the lens?
What is the term used for the zonule fibers in the lens?
What is the term used for the zonule fibers in the lens?
Which structure is responsible for promoting primary lens fiber formation in the lens epithelial cells?
Which structure is responsible for promoting primary lens fiber formation in the lens epithelial cells?
What is the term used for the central sphere inside the 'Y' sutures in the adult lens?
What is the term used for the central sphere inside the 'Y' sutures in the adult lens?
What is the origin of the zonule fibers in the lens?
What is the origin of the zonule fibers in the lens?
What could result in congenital ectopia lentis?
What could result in congenital ectopia lentis?
What is the shape of the lens fibers in the lens?
What is the shape of the lens fibers in the lens?
What is the term used for the elongation of lens epithelial cells nearest the presumptive retina?
What is the term used for the elongation of lens epithelial cells nearest the presumptive retina?
What is the embryonic lens nucleus composed of in the adult lens?
What is the embryonic lens nucleus composed of in the adult lens?
What happens if the optic fissure fails to close normally?
What happens if the optic fissure fails to close normally?
What is the term used for the secondary lens fibers that course anteriorly and posteriorly around the embryonal nucleus?
What is the term used for the secondary lens fibers that course anteriorly and posteriorly around the embryonal nucleus?
What is the term used for the localized absence of zonules in the lens?
What is the term used for the localized absence of zonules in the lens?
During which day of gestation in the dog do the optic sulci become visible?
During which day of gestation in the dog do the optic sulci become visible?
What is the term used to describe the transformation from optic sulcus to optic vesicle?
What is the term used to describe the transformation from optic sulcus to optic vesicle?
What contributes to the expansion of the optic vesicle?
What contributes to the expansion of the optic vesicle?
At approximately which day of gestation in the dog can an external bulge indicating the presence of the enlarging optic vesicle be seen?
At approximately which day of gestation in the dog can an external bulge indicating the presence of the enlarging optic vesicle be seen?
What is the role of the optic vesicle in the development of the palpebral fissure and orbital structures in the dog?
What is the role of the optic vesicle in the development of the palpebral fissure and orbital structures in the dog?
What occurs during the invagination of the optic vesicle?
What occurs during the invagination of the optic vesicle?
What structure forms when the surface ectoderm in contact with the optic vesicle thickens?
What structure forms when the surface ectoderm in contact with the optic vesicle thickens?
What happens as the space within the optic vesicle collapses during lens formation?
What happens as the space within the optic vesicle collapses during lens formation?
What is the embryonic lens nucleus composed of in the adult?
What is the embryonic lens nucleus composed of in the adult?
What surrounds the lens vesicle and will become the lens capsule?
What surrounds the lens vesicle and will become the lens capsule?
During which day of gestation in the dog does the hyaloid artery develop from mesenchyme in the optic fissure?
During which day of gestation in the dog does the hyaloid artery develop from mesenchyme in the optic fissure?
What is the consequence of the failure of the optic fissure to close normally?
What is the consequence of the failure of the optic fissure to close normally?
What is the protein content in the embryonic vitreous humor derived from?
What is the protein content in the embryonic vitreous humor derived from?
What is the role of the optic vesicle in lens formation?
What is the role of the optic vesicle in lens formation?
What is the initial event leading to the formation of the chambers of the ocular anterior segment?
What is the initial event leading to the formation of the chambers of the ocular anterior segment?
What may result from faulty keratolenticular separation?
What may result from faulty keratolenticular separation?
What is the consequence of abnormal orientation of the optic vesicle as it approaches the surface ectoderm?
What is the consequence of abnormal orientation of the optic vesicle as it approaches the surface ectoderm?
What is the size of the lens vesicle determined by?
What is the size of the lens vesicle determined by?
What is aplasia a result of in lens development?
What is aplasia a result of in lens development?
What is one of the characteristics of teratogen-induced anterior segment dysgenesis in animal models?
What is one of the characteristics of teratogen-induced anterior segment dysgenesis in animal models?
Study Notes
Development of the Optic System in Dogs
- Optic sulci become visible around day 22 of gestation in dogs.
- The transformation from optic sulcus to optic vesicle occurs concurrently with the folding of the neural ectoderm.
- Optic vesicle plays a crucial role in the development of the palpebral fissure and surrounding orbital structures by influencing the growth and positioning of these tissues.
- Mesenchyme in the optic fissure gives rise to the hyaloid artery.
- If the optic fissure fails to close normally, it can result in congenital defects such as coloboma.
- The optic vesicle is instrumental in lens formation by inducing the overlying ectoderm to thicken and form the lens placode.
Lens Development and Structure
- Initial events leading to the formation of the chambers of the ocular anterior segment begin with the invagination of the lens placode.
- The lens vesicle is surrounded by a structure that will develop into the lens capsule.
- The embryonic lens nucleus consists of cells that mature to form the central, transparent core of the lens.
- Anterior cuboidal epithelial cells in the lens continue to develop into secondary lens fibers.
- Zonule fibers, also known as zonules of Zinn, connect the ciliary body to the lens.
- Primary lens fiber formation in lens epithelial cells is promoted by growth factors from the optic vesicle.
Lens Fiber Characteristics
- The central sphere inside the 'Y' sutures in the adult lens is termed the embryonic lens nucleus.
- Zonule fibers originate from the periocular mesenchyme during development.
- A congenital condition known as ectopia lentis may arise due to improper formation of zonules.
- Lens fibers are elongated, providing structural support and transparency.
- Elongation of lens epithelial cells nearest the presumptive retina is referred to as lens fiber differentiation.
- Secondary lens fibers extend anteriorly and posteriorly around the embryonal nucleus, complementing lens formation.
Spatio-temporal Aspects
- At approximately day 24 of gestation, an external bulge indicating the enlarging optic vesicle can be observed.
- Invagination of the optic vesicle results in the formation of the lens vesicle.
- Failure of optic fissure closure can lead to significant ocular anomalies, disrupting normal eye development.
- Abnormal orientation of the optic vesicle can hinder proper lens and surrounding structure formation.
- The size of the lens vesicle is determined by interactions with the surrounding tissues, including the optic vesicle.
- Aplasia in lens development occurs due to genetic factors or teratogens disrupting normal signaling pathways.
Teratogenic Influences
- Teratogen-induced anterior segment dysgenesis in animal models exhibits various characteristics like abnormal lens and corneal development.
- The protein content of the embryonic vitreous humor is derived from cellular components and signals within the developing eye structures.
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Test your knowledge on the development of optic sulci and the transformation into optic vesicles in dogs.
