Eye

Question 1

Where are more than half the sensory receptors of human body contained?

Answer 1

the eye

Question 2

What protects the eye?

Answer 2

accessory structures

• eyelids
• extraoccular muscles
• lacrimal apparatus

Question 3

What are the layers of the eyeball? What type of tissues are they?

Answer 3

• fibrous layer (tunica)
• vascular layer (middle layer)
• nervous layer
• these are connective tissues

Question 4

What is 5/6ths of the posterior part of the fibrous layer? What does it do?

Answer 4

• the posterior 5/6ths of it is made up of whitish dense connective tissue called the sclera
• it protects the inner parts of the eyeball and serves as the attachment site for extraocular muscles and maintains the shape of the eyeball

Question 5

Where does the optic nerve and blood vessels penetrate the fibrous layer?

Answer 5

the posterior aspect of the sclera

Question 6

What is the anterior 1/6th of the fibrous layer?

What does it do?

Answer 6

• called the cornea
• transparent and lacks blood vessels
• covered by conjunctiva
• anteriorly convex so it helps focusing the light onto the retina

Question 7

What are the parts of the vascular layer of the eyeball?

Answer 7

• choroid
• ciliary body
• iris

Question 8

What forms the 5/6ths of the vascular layer?

What does it do?

Answer 8

• choroid
• lines the inner surface of the sclera
• highly vascularized and nourishes the retina
• the choroid carries melanin pigments that absorb the light rays and prevents the reflection of light within the eyeball

Question 9

What is the anterior continuation of the choroid layer of the vascular layer? What does it do? What is it composed of?

Answer 9

• the ciliary body
• secretes aqueous humour
• modifies the convexity of the lens
• the core is formed by the circular smooth muscle fibres, the ciliary muscle
• suspensory ligaments stretch between the inner surface of the ciliary body and the circumference of the lens

Question 10

What is the suspensory ligament? Where is it?

Answer 10

• it is a delicate fibre

- located between the inner surface of the ciliary body and the circumference of the lens of the eye

Question 11

What causes the lens to adapt to near vision? What about far vision?

Answer 11

• contractions of the ciliary muscles alters the convexity of the lens to allow for near vision
• relaxation of the muscle causes far vision

Question 12

What forms the anterior 1/6th of the vascular layer of the eye? How is it made? What does it do?

Answer 12

• the iris
• forms a vertical disk in front of the lens and behind the cornea
• the core of iris is made by smooth muscle fibers that are arranged in circular or radial manner
• the iris carries melanin pigments that determines the colour of the eye based upon the amount of pigment there is

Question 13

How is the pupil altered? What does this do?

Answer 13

• via contraction of the muscle fibers of the iris
• the parasympathetic activation contracts the circular muscle fibers that entails constriction of the pupil
• the sympathetic activation contracts the radial muscle fibers that leads to dilation of the pupil
• determines the amount of light entering the eyeball

Question 14

What the parts to the nervous layer of the eye?

Answer 14

• retina

- anterior 1/4th

Question 15

What makes up the posterior 3/4ths of the nervous layer? What is it composed of?

Answer 15

• the retina

- carries photoreceptors

Question 16

Where is the optic nerve in the eye? What is its’ effect on vision?

Answer 16

• it is the optic disc of the retina

- causes a blindspot in vision

Question 17

What does the macula lutea do in the eye? What is it composed of? Where is it located?

Answer 17

• very sensitive to light
• it is composed of color detecting photoreceptors
• situated lateral to the optic disc

Question 18

Where is the highest concentration of photoreceptors?

Answer 18

the fovea which is the center of the macula lutea

Question 19

What does the anterior 1/4th of the the nervous layer do? What is it made of?

Answer 19

• has no photoreceptors
• carries pigments
• lines the ciliary body and the posterior surface of the iris

Question 20

What is the lens made of?

Answer 20

• transparent, biconvex, elastic body

- lacks blood vessles

Question 21

Where is the lens located?

Answer 21

posterior to the iris

Question 22

How is the lens held in place?

Answer 22

by suspensory ligaments that act as the tendons of the ciliary muscles

Question 23

What are the 3 chambers of the eye?

Answer 23

• anterior
• posterior
• vitreous

Question 24

Where is the anterior chamber located?

Answer 24

between the cornea and the iris

Question 25

What is aqueous humour?

Answer 25

- it is a clear fluid that cushions the lens and cornea and provides a transport system for nutrients and waste materials - located in the anterior chamber of the eye and the posterior chamber

Question 26

Where is the posterior chamber located?

Answer 26

- behind the iris and in front of the lens | - continuous with the anterior chamber through the pupil

Question 27

Where is the aqueous humour secreted from?

Answer 27

- ciliary body | - fills the posterior chamber flows through the pupil and fills the anterior chamber

Question 28

Where does the aqueous humour drain?

Answer 28

scleral venous sinus via the canal of schlemm

Question 29

Where is the canal of schlemm located?

Answer 29

at the junction of the sclera and cornea

Question 30

Where is the vitreous chamber located?

Answer 30

between the lens and the retina

Question 31

What is the vitreous body?

Answer 31

- It is a clear jelly-like substance in the vitreous chamber | - helps maintains the shape of the eyeball, cushions the lens, and holds the retina against the choroid

Question 32

What does the iris do?

Answer 32

protect the eye against excessive light and foreign objects

Question 33

What is the tarsal plate?

Answer 33

a fibroelastic plate and skeletal muscles that forms the core of the eyelid

Question 34

What is conjunctiva?

Answer 34

a mucous membrane that reflects on the eyeball to cover the cornea and lines the inner surface of the eyelids

Question 35

Where are the eyelashes, sweat glands, and sebaceous gland found?

Answer 35

in the free margin of the eyelids

Question 36

What are the components of the lacrimal apparatus?

Answer 36

- lacrimal gland - lacrimal canaliculi - lacrimal sac - nasolacrimal duct

Question 37

What does the lacrimal apparatus do?

Answer 37

produce and drain tears

Question 38

Where is the lacrimal gland?

Answer 38

superolateral part of the orbital cavity

Question 39

What does the lacrimal gland do?

Answer 39

releases the tears on the surface of the eye

Question 40

Where are tears collected?

Answer 40

- swept by the blinking movements of the eye | - collected in the medial corner of the eye

Question 41

What makes up the lacrimal canaliculi?

Answer 41

a pair of small tubes

Question 42

Where are the lacrimal canaoliculi located?

Answer 42

medial corner of the eye

Question 43

What does the lacrimal canaoliculi do?

Answer 43

drain the tears into the lacrimal sac

Question 44

What is the lacrimal punctum?

Answer 44

the opening to the lacrimal canaoliculi

Question 45

What is the lacrimal sac made of?

Answer 45

a membranous sac

Question 46

Where is the lacrimal sac located?

Answer 46

fills the lacrimal groove of the lacrimal bone

Question 47

What does the lacrimal sac do?

Answer 47

receives the tears from the lacrimal canaliculi

Question 48

What is the nasolacrimal duct?

Answer 48

is the distal continuation of the lacrimal sac

Question 49

Where does the nasolacrimal duct empty into?

Answer 49

lateral wall of the nasal cavity at the inferior nasal meatus

Question 50

What are the smooth muscles of the iris and ciliary body classified as?

Answer 50

intrinsic muscles of the eye