Histology II: the eyes

Question 1

Main purpose of the sense organs?

Answer 1

provide the connection between central nervous system and outer and inner environment.

Question 2

What basic components do sense organs consist of?

Answer 2

receptors,
pathways and
center in the central nervous system.

Question 3

Receptors contain?

Answer 3

sensory cells

Question 4

Sense organs are divided into what three groups, depending on the nature of the sensory cells?

Answer 4

1. sense organs with primary sensory cells with central processes (axon)
2. sense organs with only secondary sensory cells (dendrites)
3. sense organs with nerve endings are located diffusedly in the tissues

Question 5

Name 2 sensory systems.

Answer 5

external (exteroception) and internal (interoception) sensory systems

Question 6

Give an example of a sense organ with primary sensory cells.

Answer 6

eyes and nose

Question 7

Give an example of sense organs with only secondary sensory cells.

Answer 7

hearing organ, vestibular organ, and gustatory receptors

Question 8

Give an example of a sense organ with nerve endings diffused throughout.

Answer 8

skin

Question 9

What layers does the wall of the eye consist of?

Answer 9

The outer fibrous layer or corneoscleral coat,
The middle uvea (layer) or vascular coat,
The inner layer or retina

Question 10

Another name for the outer fibrous layer of the eye.

Answer 10

corneoscleral coat

Question 11

Another name for the uveal layer of the eye.

Answer 11

vascular coat

Question 12

What 3 main structures does the uveal layer contain?

Answer 12

choroid, ciliary body and iris

Question 13

What is the choroid?

Answer 13

is the vascular layer that provides nutrients to the retina.

Question 14

What is the ciliary body?

Answer 14

is a circular structure that is an extension of the iris, it produces the aqueous humor. It also contains the ciliary muscle

Question 15

Difference between vitreous- and aqueous humor?

Answer 15

Vitreous humor is the fluid which is between the lens and retina, the aqueous humor is the fluid between the cornea and lens.

Question 16

Purpose of the ciliary muscle?

Answer 16

changes the shape of the lens/ controls accommodation for viewing objects and regulates the flow of aqueous humor into Schlemm’s canal.

Question 17

What is the iris?

Answer 17

The iris is a contractive diaphragm that extends over the anterior surface of the lens.

Question 18

What is the canal of Schlemm?

Answer 18

also known as the scleral venous sinus

is a circular canal found within the posterior part of the corneoscleral junction.

Question 19

What is the function of Schlemm’s canal?

Answer 19

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.

Question 20

What main two parts can we describe the retina as consisting of?

Answer 20

the neural retina and the pigment epithelium

Question 21

What is the neural retina?

Answer 21

an inner layer the contains light sensitive receptors and a complex of neuronal networks.

Question 22

What is the retinal pigment epithelium?

Answer 22

an outer layer composed of simple cuboidal melanin-containing cells.

Question 23

Name the chambers of the eye.

Answer 23

anterior chamber
posterior chamber
vitreous chamber

Question 24

Where is the anterior chamber?

Answer 24

the space between the cornea and the iris

Question 25

Where is the posterior chamber?

Answer 25

the space between the iris and the lens

Question 26

Where is the vitreous chamber?

Answer 26

the space between lens and retina

Question 27

The site where the optic nerve joins the retina is called ?

Answer 27

the optic disc

Question 28

What is the optic disc?

Answer 28

The site where the optic nerve joins the retina

Question 29

The shallow depression located lateral to the optic disc is called?

Answer 29

The fovea centralis

Question 30

What is the fovea centralis?

Answer 30

a shallow depression located lateral to the optic disc

Question 31

A yellow-pigmented zone surrounding the fovea centralis is called?

Answer 31

macula lutea

Question 32

What is the macula lutea?

Answer 32

the small yellowish area of the retina near the optic disk

Question 33

What is the function of the macula lutea?

Answer 33

its the part of the retina that is responsible for visual acuity. It contains a very high concentration of cones.

Question 34

What is the function of the fovea centralis?

Answer 34

is responsible for high-acuity vision it is densely saturated with cone photoreceptors.

Question 35

What is the purpose of the optic disc?

Answer 35

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.

Question 36

What two regions can be found in the neural retina?

Answer 36

``` the non-visual part (nonphotoreceptive region) optic part (photosensitive region) ```

Question 37

Where is the nonphotosensitive region of the neural retina located?

Answer 37

anterior to the ora serrata

Question 38

Where is the photosensitive region of the neural retina located?

Answer 38

posterior to the ora serrata except where it is pierced by the optic nerve.

Question 39

What is the ora serrata?

Answer 39

The ora serrata is the serrated junction between the choroid and the ciliary body.

Question 40

The retina's neurons and supporting cells can be classified into what 4 groups?

Answer 40

Photoreceptors Conducting neurons Association cells Supporting neuroglial cells

Question 41

Examples of photoreceptors

Answer 41

retinal rods and cones

Question 42

Examples of conducting neurons

Answer 42

bipolar and ganglion cells

Question 43

Example of association cells

Answer 43

horizontal cells

Question 44

What path does reception of light take

Answer 44

photoreceptor -> bipolar neuron -> multipolar neurons

Question 45

Another name for multipolar neurons.

Answer 45

ganglion cells

Question 46

Describe the ocular lense.

Answer 46

a transparent, avascular, biconvex structure

Question 47

What are the 3 principal components of the lens.

Answer 47

Lens capsule Subcapsular epithelium Lens fibers

Question 48

Describe the lens capsule.

Answer 48

a thick basal lamina, produced by the anterior lens cells.

Question 49

Describe the lens' subcapsular epithelium.

Answer 49

a cuboidal layer of cells present only on the anterior surface of the lens.

Question 50

Describe the lens fibers.

Answer 50

structures derived from subcapsular epithelial cells.

Question 51

What 5 layers does the cornea consist of?

Answer 51

three cellular and two noncellular layers: ``` Corneal epithelium Anterior basement membrane (Bowman´s membrane) Corneal stroma (substantia propria) Posterior basement membrane Corneal endothelium ```

Question 52

What does the corneal epithelium consist of?

Answer 52

nonkeratinized stratified squamous epithelium.

Question 53

What is the anterior basement membrane?

Answer 53

a homogeneous-appearing layer on which the corneal epithelium rests. It acts as a barrier to the spread of infections.

Question 54

What does the corneal stroma consist of?

Answer 54

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.

Question 55

What is the posterior basement membrane?

Answer 55

4th layer of cornea, a thick basal lamina.

Question 56

What is the corneal endothelium?

Answer 56

the innermost layer or the cornea that provides for metabolic exchange between the cornea and aqueous humor.

Question 57

What are the 3 cellular layers of the cornea?

Answer 57

corneal epithelium corneal stroma corneal endothelium

Question 58

What are the 2 noncellular layers of the cornea?

Answer 58

anterior basement membrane | posterior basement membrane