Histology II: the eyes Flashcards
Main purpose of the sense organs?
provide the connection between central nervous system and outer and inner environment.
What basic components do sense organs consist of?
receptors,
pathways and
center in the central nervous system.
Receptors contain?
sensory cells
Sense organs are divided into what three groups, depending on the nature of the sensory cells?
- sense organs with primary sensory cells with central processes (axon)
- sense organs with only secondary sensory cells (dendrites)
- sense organs with nerve endings are located diffusedly in the tissues
Name 2 sensory systems.
external (exteroception) and internal (interoception) sensory systems
Give an example of a sense organ with primary sensory cells.
eyes and nose
Give an example of sense organs with only secondary sensory cells.
hearing organ, vestibular organ, and gustatory receptors
Give an example of a sense organ with nerve endings diffused throughout.
skin
What layers does the wall of the eye consist of?
The outer fibrous layer or corneoscleral coat,
The middle uvea (layer) or vascular coat,
The inner layer or retina
Another name for the outer fibrous layer of the eye.
corneoscleral coat
Another name for the uveal layer of the eye.
vascular coat
What 3 main structures does the uveal layer contain?
choroid, ciliary body and iris
What is the choroid?
is the vascular layer that provides nutrients to the retina.
What is the ciliary body?
is a circular structure that is an extension of the iris, it produces the aqueous humor. It also contains the ciliary muscle
Difference between vitreous- and aqueous humor?
Vitreous humor is the fluid which is between the lens and retina, the aqueous humor is the fluid between the cornea and lens.
Purpose of the ciliary muscle?
changes the shape of the lens/ controls accommodation for viewing objects and regulates the flow of aqueous humor into Schlemm’s canal.
What is the iris?
The iris is a contractive diaphragm that extends over the anterior surface of the lens.
What is the canal of Schlemm?
also known as the scleral venous sinus
is a circular canal found within the posterior part of the corneoscleral junction.
What is the function of Schlemm’s canal?
The function of Schlemm’s canal is to collect the aqueous humor from the anterior chamber of the eyeball and deliver it to the veins of the eyeball.
What main two parts can we describe the retina as consisting of?
the neural retina and the pigment epithelium
What is the neural retina?
an inner layer the contains light sensitive receptors and a complex of neuronal networks.
What is the retinal pigment epithelium?
an outer layer composed of simple cuboidal melanin-containing cells.
Name the chambers of the eye.
anterior chamber
posterior chamber
vitreous chamber
Where is the anterior chamber?
the space between the cornea and the iris
Where is the posterior chamber?
the space between the iris and the lens
Where is the vitreous chamber?
the space between lens and retina
The site where the optic nerve joins the retina is called ?
the optic disc
What is the optic disc?
The site where the optic nerve joins the retina
The shallow depression located lateral to the optic disc is called?
The fovea centralis
What is the fovea centralis?
a shallow depression located lateral to the optic disc
A yellow-pigmented zone surrounding the fovea centralis is called?
macula lutea
What is the macula lutea?
the small yellowish area of the retina near the optic disk
What is the function of the macula lutea?
its the part of the retina that is responsible for visual acuity. It contains a very high concentration of cones.
What is the function of the fovea centralis?
is responsible for high-acuity vision it is densely saturated with cone photoreceptors.
What is the purpose of the optic disc?
is the point of exit for ganglion cell axons leaving the eye.
Because there are no rods or cones overlying the optic disc, it corresponds to a small blind spot in each eye.
The ganglion cell axons form the optic nerve after they leave the eye.
What two regions can be found in the neural retina?
the non-visual part (nonphotoreceptive region) optic part (photosensitive region)
Where is the nonphotosensitive region of the neural retina located?
anterior to the ora serrata
Where is the photosensitive region of the neural retina located?
posterior to the ora serrata except where it is pierced by the optic nerve.
What is the ora serrata?
The ora serrata is the serrated junction between the choroid and the ciliary body.
The retina’s neurons and supporting cells can be classified into what 4 groups?
Photoreceptors
Conducting neurons
Association cells
Supporting neuroglial cells
Examples of photoreceptors
retinal rods and cones
Examples of conducting neurons
bipolar and ganglion cells
Example of association cells
horizontal cells
What path does reception of light take
photoreceptor -> bipolar neuron -> multipolar neurons
Another name for multipolar neurons.
ganglion cells
Describe the ocular lense.
a transparent, avascular, biconvex structure
What are the 3 principal components of the lens.
Lens capsule
Subcapsular epithelium
Lens fibers
Describe the lens capsule.
a thick basal lamina, produced by the anterior lens cells.
Describe the lens’ subcapsular epithelium.
a cuboidal layer of cells present only on the anterior surface of the lens.
Describe the lens fibers.
structures derived from subcapsular epithelial cells.
What 5 layers does the cornea consist of?
three cellular and two noncellular layers:
Corneal epithelium Anterior basement membrane (Bowman´s membrane) Corneal stroma (substantia propria) Posterior basement membrane Corneal endothelium
What does the corneal epithelium consist of?
nonkeratinized stratified squamous epithelium.
What is the anterior basement membrane?
a homogeneous-appearing layer on which the corneal epithelium rests. It acts as a barrier to the spread of infections.
What does the corneal stroma consist of?
it constitutes 90% of corneal thickness composed of numerous thin lamellae.
Each lamellae consists of parallel bundles of collagen fibrils and flattened fibroblasts between them.
What is the posterior basement membrane?
4th layer of cornea, a thick basal lamina.
What is the corneal endothelium?
the innermost layer or the cornea that provides for metabolic exchange between the cornea and aqueous humor.
What are the 3 cellular layers of the cornea?
corneal epithelium
corneal stroma
corneal endothelium
What are the 2 noncellular layers of the cornea?
anterior basement membrane
posterior basement membrane
