Ocular Embrology Flashcards
(17 cards)
What are the germinal cell layers and their contributions to ocular development?
Germinal cell layers:
* Ectoderm (outer) – neural tissue, skin, nails, hair
* Mesoderm (middle) – muscle, bone, connective tissue, circulatory system
* Endoderm (inner) – internal organs
Ectoderm gives rise to the lens and cornea, mesoderm contributes to extraocular muscles and vascular structures, while endoderm does not contribute to ocular development.
What is the first key event in ocular development?
Day 22: the optic primordia appear in the neural folds.
This marks the beginning of the formation of the eye structures.
At what stage does the optic vesicle induce the surface ectoderm to thicken?
By day 27: lens placode, optic vesicle attached to optic stalk.
This is crucial for lens formation.
What structures are formed from the optic cup?
Optic cup forms:
* Neurosensory retina
* Retinal pigment epithelium
The optic cup consists of a thick inner layer and a thin outer layer.
What is the significance of the ora serrata in the eye?
The demarcation between the anterior fifth and posterior four fifths of the inner layer of the optic cup is visible as the ora serrata in the adult eye.
This structure is present by 6 months of gestation.
Fill in the blank: The _______ provides the lens with blood supply during development.
hyaloid artery
The hyaloid artery is a branch of the ophthalmic artery.
What happens to the hyaloid artery by the end of the 6th week?
The choroidal fissure closes, and the primary vascular vitreous starts to develop.
This marks a transition in the eye’s vascular development.
What does a cone-like structure known as Bergmeister’s papilla consist of?
Bergmeister’s papilla consists of glial cells and remnants of hyaloid vessels.
It may persist at the optic nerve head in some individuals.
What are the derivatives of neuroectoderm in ocular development?
Neuroectoderm derivatives:
* Retina
* Optic nerves
* Epithelium of the iris
* Epithelium of ciliary body
* Iris smooth muscle (sphincter and dilator pupillae)
These structures are crucial for the functioning of the eye.
What are some ocular defects associated with PAX6 gene mutations?
Ocular defects include:
* Anophthalmia
* Anterior segment dysgenesis
* Congenital glaucoma
* Peter’s anomaly
* Axenfeld-Rieger’s anomaly
PAX6 is a master control gene involved in eye development.
What is coloboma?
Coloboma is a defect in the inferonasal quadrant of the iris, ciliary body, or choroid due to failure of the inferonasal optic fissure to close.
It can also affect the retina.
Fill in the blank: Neural crest cells and mesoderm together are called _______.
mesenchyme
This term refers to the embryonic connective tissue that contributes to various ocular structures.
What is the connection between maternal rubella infection and congenital defects in the child?
Rubella virus is a potent teratogen; can cause congenital cataracts, hearing loss, and heart defects.
This transmission typically occurs before the 7th week of gestation.
What is the diagnosis for a small notch on the iris that has been present since birth?
Diagnosis: small coloboma of the left eye.
This results from a failure of closure of the optic fissure.
True or False: Strabismus can be a congenital anomaly.
True
Congenital strabismus can arise from an imbalance of extraocular muscles.
What is the embryological explanation for a child’s congenital cataract due to maternal infection?
Congenital cataract results from placental transmission of the rubella virus before the 7th week.
This can lead to multiple congenital defects.
