OPT1210 Exam 3 Flashcards
What is the joining of an ovum and a sperm called?
fertilized zygote
What are the six stages of development?
Fertilization (Day 1) Pre-embryonic (Weeks 1-2) Embryonic (Weeks 2-9) Fetal (Weeks 9-Delivery) Neonate (first 4 weeks after birth) Infant (after 4 weeks)
What are the stages of Embryogenesis?
Fertilization 2-cell zygote 4-cell zygote 8-cell zygote 16-cell zygote....... Morula (64-cells) Blastula (100 cells) Gastrula Embryo
In what stage does the Zona Pellucida disintegrate to release the blastocyst?
Pre-embryonic
What does the gastrula initially separate into?
Epiblast - Primitive streak
Hypoblast
When the Zona Pellucida disintegrates, what is released?
Blastocyst
What do the inner and outer layers of the blastocyst develop into?
Trophoblast - outer cells form placenta
Embryoblast - inner cells develop into embryo
The gastrula divides into three primary germ layers. What are they?
Ectoderm - epidermis, brain neuron, pigment
Mesoderm - muscle cells, RBCs
Endoderm - pancreas, lung, thyroid
Embryonic mesoblast consists of what 3 layers?
Outer Neuroectoderm
Middle Mesoderm
Inner Endoderm
By what day does the embryo have a head to tail orientation?
Day 19
By Day 19, the Neuroepithelium shows polarity and has what orientation?
Apex up, Base down
By Day 22, the Neuroepithelium has what orientation?
Cell apex inside, call base out
By what Day do the neural folds fuse and become neural tube?
Day 22
By what Day does the optic primordium form?
Day 22
What appears by Day 23 as an evagination of forebrain (prosencephalon)?
Optic Pit
By what day does the neural tube close?
Day 23
The optic stalk develops into what?
optic nerve
The optic vesicle develops into what?
Globe
The eye fields for optic vesicle at what day?
Day 25
The optic vesicle induces the lens placode in what week?
Weeks 3-4
When does the right and left optic primordia meet at the optic chiasma?
Weeks 5-6
Stage 11
When does the optic cup and lens vesicle invaginate?
Day 27
Stage 11
When does the embryonic fissure close?
Day 33
What feeds the lens and fills the embryonic fissure in Weeks 5-6?
Hyaloid artery
What are floaters?
Remnants of the hyaloid artery
When do eyelid folds appear?
Weeks 5-6
Stage 11
What do the eyelid folds become?
layers of the retina
In what weeks do the eyelids form?
Weeks 8-10
In what weeks are the lens placode indented by lens pit?
Weeks 8-10
When is the cornea formed?
Weeks 7-8
When is the anterior chamber formed?
Weeks 7-8
What are the ocular stages of development termed?
Carnegie Ocular Stages
What occurs in Stage 10?
Optic Primordia
What occurs in Stage 11?
Right and Left Optic primordia meet at optic chiasma
What occurs in Stage 12?
Optic neural crest is at maximum
Optic vesicle covered by sheath
What occurs in Stage 13?
Optic Vesicle close to surface ectoderm causes thickening to form lens
What occurs in Stage 14?
Lens placode indented by lens pit
What occurs in Stage 15?
Lens pit is closed
Lens vesicle and optic cup close to surface ectoderm
What happens in Stage 16?
Growth of the lens body into d-shaped cavity
perilental blood vessels (Tunica vasculosa lentis)
Eyelid groove is formed
What is formed in Stage 17?
Retinal pigment visible
Retinal fissure closed
eyelid grooves deepen
eyelid folds develop first below, then above eye
What occurs in Stage 18?
Mesenchyme invades between lens epithelium and surface ectoderm
What occurs in Stage 19-22?
Eyelid folds develop into eyelids
Palpebral fissure takes shape
Upper and lower eyelids meet at outer canthus
What occurs in Stage 20?
Lens cavity is lost
Lens suture begins to form
Inner canthus is established
What occurs in Stage 23?
Retina is comprised of many layers
What layers comprise retina?
Pigmented layer External limiting membrane Proliferative zone external neuroblastic layer transient fiber layer internal neuroblastic layer nerve fiber layer internal limiting membrane eyelids closure is complete
What occurs in Stage 22?
Lens sutures
Retina forming
When is optic vesicle fully developed?
Day 25
When is the optic cup formed?
Day 27
What forms to allow the hyaloid artery to enter the inner eye and the ganglion cell axons to exit?
Embryonic fissure
What day does the embryonic fissure close?
Day 33
What starts the formation of the basic structure of the eye?
The closure of the embryonic fissure
What becomes retina and retinal pigment epithelium?
The lips of the optic cup (inner and outer neuroepithelium)
What occurs when the retinal pigment epithelium does not fuse?
Coloboma
What is a coloboma that occurs anteriorly?
An iris defect
What is the lens derived from?
Surface ectoderm
What is the retina derived from?
Neuroectoderm
What is the vascular endothelium derived from?
Mesoderm
What is the vitreous (hyaloid vessels, collagen fibrils, hyaluronic acid) derived from?
Neuroectoderm
When is retinal vascularization completed?
8 months
When do the eyelids unfuse?
22 weeks
When does a fetus open its eyes?
26-28 weeks
What is an absence of the iris called?
aniridia
How many bones make up the orbit?
7
What are the bones of the orbit?
Frontal (roof of orbit) Sphenoid Zygomatic Ethmoid Palatine Lacrimal Maxillary (floor of orbit)
How many wall of the orbit are there and what are they?
4; Superior Medial Inferior Lateral
What shape is the orbit and how is it oriented?
Pyramidal
Base is anterior
Apex is posterior
How does orbital entrance sit in skull?
45 degree angle
Rotated laterally
What “hole” carries the sensory nerves from upper part of face - 1st division of trigeminal nerve (V)?
Supraorbital foramen (may or may not be true foramen…usually a notch)
What “hole” carries the 2nd division of trigeminal nerve (V)?
Infraorbital Foramen (true foramen)
What “hole” do most nerves in skull go through?
Superior Orbital Fissure
What “hole” does the optic nerve go through?
Optic Foramen
The trochlear is what?
The “pulley” that holds the superior oblique muscle
How do we maintain the primary position of gaze?
Constantly firing medial recti muscles
How does the globe sit within the orbit?
laterally 23 degrees with respect to the midline
Orbital muscles only pull globe in natural primary position
What are two functions of eyelids?
Protect eye (eyelid skin) Distributes tears and contribute to tear film
Where do the orbital muscles insert?
On the globe
Where is the origin of the orbital muscles?
Annulus of Zinn
What muscle lifts the upper eyelid?
Levator Palpebrae Superioris
Where are the Meimobian glands and what do they secrete?
Embedded in the tarsal plates in the eyelids
Oily component of tear film around eyelids
Which way do muscle fibers of orbicularis oculi run?
Laterally
What is the dense fibrous connective tissue beneath the muscle layer in the eyelid?
Tarsal plates
Eyelid tendons
What muscle closes the eyelids?
Orbicularis oculi
What are the 3 glands of the eyelids and their function?
Meibomian glands - largest glands, oily secretion
Glands of Zeis - sebaceous glands at base of eyelashes
Glands of Moll - apocrine or sweat glands at base of eyelashes
What part of tear film does lacrimal gland secrete?
Aqueous
What are the cilia follicles?
eyelashes
What are the 3 portions of the orbicularis oculi?
Preseptal
Pretarsal
Orbital
What muscle is innervated by the autonomic nervous system (sympathetic and inserts beneath the tendon of the levator on the tarsal plate?
Mullers Muscle
What is overstimulation of Mullers muscle called?
Eyelid Stare
How many Meibomian glands are embedded in upper tarsus? Lower tarsus?
25 Upper
20 Lower
What are the tendons of the eyelid that insert laterally and medially?
Canthal tendons
What are the lacrimal bones?
Lacrimal
Inferior Concha
Ethmoid
Maxillary
What does the lacrimal system do?
Produce and drain tears
What are the parts of the lacrimal system?
Lacrimal glands (2) - produce tears
Superior and inferior puncta - drain tears to canaliculi
Lacrimal sac - hold tears from canaliculi
Lacrimal canal - to nose
What is the path of tears?
Orbital and Palpebral lacrimal gland (aqueous tears)
Superior and Inferior puncta
Superior and Inferior canaliculi (vertical)
Lacrimal sac
Nasolacrimal duct
Inferior concha (turbinate)
What are the 3 components of the tear film?
Oil from meibomian glands (outermost layer) and glands of Zeis
Aqueous from lacrimal gland (middle layer)
Mucus from goblet cells of conjunctiva (innermost layer)
Where does tear film pool?
lower eyelid margin
Lacrimal gland has how many portions, how many ducts?
2 portions: Orbital and Palpebral
12 ducts - pass from Orbital to Palpebral
How many types of tears are there and what are they?
Basal
Reflex
Emotional
What triggers tears? and blinking?
osmolarity - senses salt concentration
What is the composition of tears?
Water, Electrolytes, Lipids, Mucin, Proteins, enzymes Inflammatory Mediators Cytokines Growth factors WBCs Antigens Signaling molecules Complement Remodeling enzymes
Explain the blink
As upper eyelid descends, the punctal papillae elevate and touch each other to prevent reflux of previous tears
Lid closure squeezes the fluid out of the drainage system into the sac and canal
As eyelid opens, a vacuum is created (by negative pressure) and tears are sucked into the drainage system
Which puncta drains 85% of tears?
Inferior puncta (gravity)
When do babies produce tears?
After 6 weeks of age when lacrimal gland ducts are formed
