S 1.2 Eyeball - pt.1 - A

Question 1

The wall of the eyeball has three concentric coats which enclose three compartments, namely:

Answer 1

anterior, posterior and vitreous chambers

Question 2

What are the three coats found in the eyeball?

Answer 2

A. Outer fibrous coat / Sclerocorneal layer
B. Middle vascular coat / Uveal tract
C. Inner photosensitive coat / Retina

Question 3

This coat consists of the opaque posterior four-fifth, the sclera and the anterior transparent one-fifth, the cornea. The sclera and cornea become continuous with each other at the limbus or the sclerocorneal junction.

Answer 3

Outer Fibrous Coat / Sclerocorneal Layer

Question 4

Outer Fibrous Coat / Sclerocorneal Layer

Answer 4

• Sclera
• Cornea
• Sclerocorneal Junction / Limbus

Question 5

• It is a dense regular connective tissue resembling that of ligaments and tendons, provides rigid structural support for the eyeball
• It is composed mostly of dense collagen fibers and few elastic fibers
• It is separated externally from Tenon’s capsule (fascial sheath of eyeball) by episcleral layer of loose connective tissue (Tenon’s space) and internally from the choroid by lamina fusca (suprachoroidal lamina) of dark pigmented fibroelastic tissue.
• Posteriorly it is pierced by axons of ganglionic cells of retina at lamina cribrosa to form optic
  nerve.

Answer 5

Sclera

Question 6

Sclera:
- a _______ ________ connective tissue resembling that of ligaments and tendons, provides rigid structural support for the eyeball

Answer 6

dense regular

Question 7

Sclera:
It is composed mostly of dense _________ fibers and few ______ fibers.

Answer 7

collagen; elastic

Question 8

Sclera:
It separated externally from ________ _______ (fascial sheath of eyeball) by episcleral layer of loose connective tissue (Tenon’s space) and internally from the
_________ by lamina fusca (suprachoroidal lamina) of dark pigmented fibroelastic tissue.

Answer 8

Tenon’s capsule; choroid

Question 9

Sclera:
Posteriorly it is pierced by axons of ganglionic cells of _______ at _________ _______ to form optic nerve

Answer 9

retina; lamina cribrosa

Question 10

• It is a dense connective tissue with a layer of epithelium on both sides—is about 0.5 mm thick, 11.5 mm in diameter, transparent, and resistant to deformation.
• It occupies one-fifth of the ocular surface, with its radius of curvature less than that of the rest of the eyeball.
• Its anterior surface is nonkeratinized stratified squamous epithelium, about 50 µm thick and consisting of 3-6 layers of cells, except near the periphery, where it is 8-10 layers.
• Basal cells are polygonal, but the most superficial cells, which retain nuclei, are flattened.
• The epithelium continuously replicates, and it regenerates in response to wear and tear.

Answer 10

Cornea

Question 11

Cornea:
It is a dense connective tissue with a layer of epithelium on both sides—is about ____ mm thick, ____ mm in diameter, transparent, and resistant to deformation

Answer 11

0.5; 11.5

Question 12

Cornea:
Its anterior surface is ___________ ___________ __________ epithelium, about 50 µm thick and consisting of _____ layers of cells, except near the periphery, where it is _____ layers.

Answer 12

nonkeratinized stratified squamous; 3-6; 8-10

Question 13

Cornea:
Basal cells are __________, but the most superficial cells, which retain nuclei, are _________.

Answer 13

polygonal; flattened

Question 14

Cornea:
The epithelium continuously replicates, and it regenerates in response to wear and tear. Its rich sensory nerve supply (from the ___________ branch of cranial nerve V) is sensitive to _______ and _______.

Answer 14

ophthalmic; touch; pain

Question 15

Cornea:
A layer of tears lubricates the ________surface

Answer 15

anterior

Question 16

Cornea:
Deep to the epithelium is ___________________

Answer 16

Bowman’s membrane

Question 17

Cornea:
—a prominent basement membrane, 8-15 µm thick—that binds epithelium to underlying connective tissue

Answer 17

Bowman’s membrane

Question 18

Cornea: Bowman’s membrane
a prominent basement membrane, _____ µm thick—that binds _________ to underlying connective tissue

Answer 18

8-15; epithelium

Question 19

Cornea:
The thick central region, the ___________, contains 60-70 layers of type I collagen fibers, which are uniform in diameter and embedded in a proteoglycan-rich extracellular matrix

Answer 19

substantia propria

Question 20

This is misnamed corneal endothelium—lines the posterior surface

Answer 20

Simple cuboidal epithelium

Question 21

Cornea:
Its basement membrane (10-12 µm thick) is __________________.

Answer 21

Descemet’s membrane

Question 22

Cornea:
Most of it relies on ____________ of oxygen and nutrients from aqueous humor.

Answer 22

diffusion

Question 23

The boundary between cornea and sclera (white of the eye) is an abrupt transitional zone, the _______, where mucous membranes covering the sclera (_______ conjunctiva) and underside of the
eyelid (________ conjunctiva) join the anterior corneal epithelium.

Answer 23

limbus; bulbar; palpebral

Question 24

-It is marked by a shallow depression externally and it is the place where the transparent cornea becomes continuous with the opaque sclera.
- It contains an important circular canal lined by endothelium called canal of Schlemm or scleral venous sinus concerned with drainage of aqueous humour as this canal is connected externally to the anterior ciliary veins and internally to the anterior chamber through spaces of Fontana at iridocorneal angle.

Answer 24

Sclerocorneal Junction / Limbus

Question 25

Sclerocorneal Junction / Limbus: It is marked by a shallow depression externally and it is the place where the transparent _______ becomes continuous with the opaque ________.

Answer 25

cornea; sclera

Question 26

Sclerocorneal Junction / Limbus: It contains an important circular canal lined by endothelium called canal of ________ or __________ ________ _________ concerned with drainage of aqueous humour as this canal is connected externally to the anterior ciliary veins and internally to the anterior chamber through spaces of ________ at iridocorneal angle.

Answer 26

Schlemm; scleral venous sinus; Fontana

Question 27

Sclerocorneal Junction / Limbus: ______________ ________ is dialysate of blood. It is a clear watery fluid (similar to CSF in composition) produced by the ciliary epithelium, covering the ciliary processes into the posterior chamber.

Answer 27

Aqueous humour

Question 28

Sclerocorneal Junction / Limbus: __________ ___________ serves as a medium for exchange of metabolites to and from the avascular lens and cornea. It is also responsible for the intraocular pressure (normal pressure is 20 mmHg).

Answer 28

Aqueous humour