Lecture 1/19 Flashcards
vitreous humor occupies what percent of the internal aspect of the eye?
2/3
volume of the vitreous humor
3.9 cc
big depression on anterior side of vitreous called
patellar fossa
or hyloid fossa
vitreous bounded posteriorly by the
retina
vitreous bounded anteriorly by the
ciliary body, zonules, and posterior capsule of the lens
functions of vitreous
- maintains shape of the eye
- supports the retina up against its tissue
- materials exchange (diffusion)
strongest attachment of the vitreous is where?
anterior at the ora serrata and pars plana (about 6mm)
-called virtual base of Salzmann
what is the vitreous base of Salzmann?
strongest attachment of the vitreous anteriorly at the ora serrata and pars plana
where is the posterior strong vitreous attachment?
around optic nerve head
peripapillary
what is the peripapillary?
strong attachment of the vitreous around the optic nerve head
what is the weaker anterior attachment of the vitreous?
periphery of posterior lens (ring of 8-9mm) called hyaloideo-capsular
where is the hyaloideo-capsular attachment of the vitreous?
periphery of posterior lens about 8-9mm in diameter
where is the capillary space of Berger
area of potential space (non-attachment) in the center of hyaloideo-capsular ligament
hyaloideo-capular ligament clinical importance
in cataract surgery- can pull vitreous with this ligament, which can make contact with anterior chamber which is bad
microanatomy of vitreous is
semifluid, 99% water and a little hyaluronic acid and collagen fibers
purpose of the micro anatomy of the vitreous
-medium for substance exchange and structure
vitreous is what type of tissue?
modified connective tissue- a matrix of collagen fibers with water in between
primary embryological divison
hyaloidean vitreous
hyaloid artery runs:
through middle of embryonic vitreous canal (supplies anterior structures during development)
where is the anterior dilation of the hyaloidean vitreous
just behind (posterior) to the lens at that time
where is the posterior dilation of the hyaloidean vitreous
around the optic nerve
blood vessel in the hyaloidean vitreous is
hyaloid artery
what happens to the hyaloid artery as embryonic development continues?
it disintegrates because other circulation is taking place that will supply the anterior portion of the eye
the hyaloid artery disintegrating leaves:
a canal through the center of the adult vitreous called Cloquet’s canal
secondary vitreous called
definitive vitreous
definitive vitreous is:
the adult vitreous, what you are born with (the main mass)
tertiary zonules are called:
zonules (anatomists used to think they were composed of vitreous)
what are zonules formed by?
the ciliary body
what structure is at the edge of the vitreous
an envelope with cells underneath (100 microns)
location of cells at the edge of the vitreous
within a thin zone of 100 microns
shape and name of the cells at the edge of the vitreous
round cells called hyalocytes
what type of cell are hyalocytes
connective tissue type of cell which have macrophages
source of hyalocytes
cells come from the ciliary body
3 categories of ocular muscles
- intrinsic
- extrinsic
- accessory
intrinsic ocular muscles
iris (smooth), ciliary body
extrinsic ocular muscles
EOMs (4 recti, 2 oblique)- voluntary
accessory ocular muscles
eyelids
EOMs are what kind of muscle
striated, voluntary
compared to other skeletal muscles, the nerve and vascular supply in EOMs is
more rich
what is a motor unit
the ratio of number of nerves to muscle fibers
what is the EOM motor unit ratio and how does it compare to other striated muscle
EOMs have 1:6 ratio which is low, and other striated muscle has 1:100- 1:150 ratio range
what does the EOM low motor unit ratio mean?
EOMs have finer control
fibers sizes are ____ in EOMs compared to other skeletal muscles
smaller
what is the anatomical origin?
site where the muscle is attached to the bone (blending of the tendon or origin and covering of the bone, periosteum)
-strong
what is the physiological origin?
where the muscle acts from (mechanical)
5 of the 6 EOMs have their origin at:
the apex of the orbit
all except IO
the 4 rectus muscle’s origins form what at the apex?
a ring called the annulus of Zinn
the annulus of Zinn ring is formed from a special blending of what 3 tissues
- tendon of origin
- periorbital (periosteum) tissue
- dura mater (meninges)
the hole in the middle of the Annulus of Zinn is the:
oculomotor foramen
nerves and vessels can come in to the orbit through what routes?
directly through the superior orbital fissure or through the oculomotor foramen
what are the 2 aspects of the Annulus of Zinn?
- superior tendon of Lockwood (upper 1/2)
2. inferior tendon of Zinn (lower 1/2)
superior tendon of lockwood (upper 1/2) contains
- superior rectus
- upper halves of medial and lateral rectus
inferior tendon of zinn (lower 1/2) contains:
- inferior rectus
- lower halves of the medial and lateral rectus
anatomical origin of superior oblique
on sphenoid near optic foramen
physiological origin of superior oblique
fovea trochlearis (anterior on the medial wall)
what are the 2 types of anatomical insertions
primary and secondary
what are the primary insertions for the 4 recti?
insert at the anterior portion of the eye and it forms a spiral (spiral of Tillaux)
in the spiral of Tillaux, how far is each recti muscle away from the limbus
MR: 5.5 mm
IR: 6.0 mm
LR: 7.0 mm
SR: 8.0 mm
what is the primary insertion for the superior oblique
posterior quadrant, lateral and superior (1/4)
what is the primary insertion for the inferior oblique
on the posterior quadrant, lateral and inferior (1/4)
what is the purpose of secondary insertions?
stabilization, mechanical support
list 3 types of secondary insertions
- recurrent fibers
- lateral expansion
- check ligaments
path of recurrent fibers
run from belly of the muscle down to the sclera
path of lateral expansions
go sideways from the tendon to the sclera (helps prevent wobble)
path of check ligaments
connects from tendon to bone (solid insertion)
