EYE & EAR ALL CONTENT IS COPYRIGHT © OF DR. STEEVNS M.B KISAKA THIS CONTENT MAY ONLY BE USED FOR EDUCATIONAL PURPOSES BY CURRENT STUDENTS OF MAKERERE

EYE & EAR

ALL CONTENT IS COPYRIGHT © OF DR. STEEVNS M.B KISAKATHIS CONTENT MAY ONLY BE USED FOR EDUCATIONAL PURPOSES BY CURRENT STUDENTS OF MAKERERE

Objectives1. Recognise and describe a section of neural retina, identifying areas of

histogenesis with lamination/stratification and the adjacent choroid and scleral layers.

2. Recognise and describe a section of cornea, distinguishing areas of limbus-like character, as well as Descemet’s and Bowman’s membranes.

3. Be able to describe and recognise various stages in the development of optic vesicles, the differentiation of the optic cup, lens and adjacent structures, including : developing ciliary body and anterior and posterior chambers of the eye.

4. Distinguish between otic vesicles at various stages of their development and their spatial relationship with portions of the pharynx and developing cochlea in histological section.

SLIDE 200 Retina dog

Examine this section at low magnification and identify :

1. Cornea. 5. Non- neural retina. 9. Anterior chamber.

2. Iris. 6. Neural retina. 10. Posterior chamber.

3. Ciliary apparatus. 7. Choroid. 11. Cavity of vitreous humor.

4. Corneal limbus. 8. Sclera.

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910

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7

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910

11

SLIDE 200 Cornea dogIdentify :1. Cornea. 4. Anterior chamber.2. Iris. 5. Posterior chamber.3. Corneal limbus.

250 µm

External eye – Dog▪ Left eye. Note pigmented epidermis of eyelids.

▪ Identify : Medial canthus Lateral canthus 3rd eyelid Cornea Iris Pupil

SLIDE 200 Cornea dogIdentify :1. Cornea. 4. Anterior chamber.2. Iris. 5. Posterior chamber.3. Corneal limbus.

250 µm

iris

cornea

corneal limbus

anterior chamber

posterior chamber

SLIDE 200 Cornea dogExamine the cornea at higher magnification.

The function of the cornea is …….

100 µm

SLIDE 200 Cornea dogExamine the cornea at higher magnification.

The function of the cornea is …….

The cornea has an important role in image formation, it forms a primary refractive

element in the eye.

100 µm

anterior posterior

SLIDE 200 Cornea dog

100 µm

Five layers can be identified in the cornea :

1. anterior epithelium 2. anterior sub-epithelial membrane (lamina)

3. stroma 4. posterior limiting membrane (Descemet’s)

5. posterior epithelium (corneal endothelium)

SLIDE 200 Cornea dog

100 µm

stroma

anterior epithelium

anterior lamina

posterior limiting lamina Descemet’s

posterior epithelium

Five layers can be identified in the cornea :

1. anterior epithelium 2. anterior sub-epithelial membrane (lamina)

3. stroma 4. posterior limiting membrane (Descemet’s)

5. posterior epithelium (corneal endothelium)

SLIDE 200 Cornea dogIdentify : Anterior epithelium and anterior sub-epithelial basement membrane.What type of epithelium covers this surface?

25 µm


25 µm

Identify : Anterior epithelium and anterior sub-epithelial basement membrane.What type of epithelium covers this surface?Non-keratinised stratified squamous epithelium.

stroma

anterior epithelium

sub-epithelial basement membrane


25 µm

Identify : Anterior epithelium and anterior sub-epithelial basement membrane.What type of epithelium covers this surface?Non-keratinised stratified squamous epithelium.Consider the cellularity and the extent of the extracellular matrix in these compartmentsand the cornea ‘proper’.

stroma

anterior epithelium

sub-epithelial basement membrane

SLIDE 200 Cornea dogIdentify : Posterior epithelium (corneal endothelium) and posterior limiting membrane (Descemet’s membrane).What type of epithelium covers this surface?

25 µm

SLIDE 200 Cornea dogIdentify : Posterior epithelium (corneal endothelium) and posterior limiting membrane (Descemet’s membrane).What type of epithelium covers this surface?

25 µm

Identify : Posterior epithelium (corneal endothelium) and posterior limiting membrane (Descemet’s membrane).What type of epithelium covers this surface?Simple squamous epithelium. Note the lack of vasculature in the cornea.

stroma

Descemet’s membrane

posterior epithelium or corneal endothelium

SLIDE 200 Cornea dogWhat is the corneal limbus?

250 µm

iris

corneal stroma

corneal limbus

anterior chamber

posterior chamber

SLIDE 200 Cornea dogWhat is the corneal limbus?

250 µm

iris

corneal stroma

corneal limbus

anterior chamber

posterior chamber

What is the corneal limbus?The corneo-scleral junction.Here the collagen fibres of the corneal stroma become irregular and blood vesselssupplying nutrients to the cornea are seen.The anterior epithelium becomes the conjunctival epithelium.

iris

corneal stroma

corneal limbus

anterior chamber

posterior chamber

posterior epithelium

anterior epithelium

conjunctival epithelium

sclera

SLIDE 200 Iris dog

250 µm

iris

corneal limbus

anterior chamber

posterior chamber

The iris is the most anterior part of the vascular tunic (uvea) a continuation of

the choroid layer.

cornea

SLIDE 200 Iris dog

250 µm

iris

corneal limbus

anterior chamber

posterior chamber

The iris is the most anterior part of the vascular tunic (uvea) a continuation of

the choroid layer.

cornea

SLIDE 200 Iris dog

Examine the iris at higher magnification.

50 µm

SLIDE 200 Iris dog

The iris at higher magnification.

50 µm

anterior surface of iris

pars iridica retinae

myoepithelial cells

sphincter muscle

BV : blood vessels

M : melanocytes

BVBV

M

connective tissue stroma

posterior chamber

anterior chamber

SLIDE 200 Retina dogThrough examination observe whether different areas of the retina exhibits neural (thicker) and non neural (thinner) organisation approaching the iris.

100 µm

SLIDE 200 Retina dogThrough examination observe whether different areas of the retina exhibits neural (thicker) and non neural (thinner) organisation approaching the iris.

100 µm

towards iris

non-neural retina edge of neural retina close to edge of neural retina neural retina

SLIDE 200 Retina dogThis non neural portion of the retina approaching the iris consists of two layers of non-light sensitive epithelium.

This epithelium is continuous with that covering the ciliary body and iris.

50 µm

SLIDE 200 Retina dogThis non neural portion of the retina approaching the iris consists of two layers of non-light sensitive epithelium.

This epithelium is continuous with that covering the ciliary body and iris.

50 µm

epithelium of non-neural retina

choroid

SLIDE 200 Retina dogThis area shows the sudden increase in thickness of the retina as it becomes the neural retina.

The junction is called the ora ciliaris retinae.

50 µm

SLIDE 200 Retina dogThis area shows the sudden increase in thickness of the retina as it becomes the neural retina.

The junction is called the ora ciliaris retinae (arrowed).

50 µm

choroid

sclera space artefact

retina

SLIDE 200 Retina dogA comparison of the neural retina close to the periphery (left) and at its full thickness (right).Larger blood vessels may be seen in the nerve ganglion cell layer towards the edge of the retina.The individual layers are more easily recognised (right).Note the much thicker layer of rods and cones.

50 µm

SLIDE 200 Retina dogA comparison of the neural retina close to the periphery (left) and at its full thickness (right).Larger blood vessels may be seen in the nerve ganglion cell layer towards the edge of the retina.The individual layers are more easily recognised (right).Note the much thicker layer of rods and cones.

50 µm

BV : blood vessel

layer of rods & cones

choroid

sclera

BV

SLIDE 200 Retina dogExamine the neural retina in more detailObserve a full depth portion of this area and identify the different zones.

1. Inner limiting membrane.2. Nerve fibre layer.3. Ganglion cell layer.4. Inner plexiform layer.5. Inner nuclear layer.6. Outer plexiform layer.7. Outer nuclear layer.8. Outer limiting membrane.9. Layer of rods and cones.10. Pigmented epithelium.11. Choroid layer.12. Scleral layer.

50 µm

SLIDE 200 Retina dogExamine the neural retina in more detailObserve a full depth portion of this area and identify the different zones.

1. Inner limiting membrane.2. Nerve fibre layer.3. Ganglion cell layer.4. Inner plexiform layer.5. Inner nuclear layer.6. Outer plexiform layer.7. Outer nuclear layer.8. Outer limiting membrane.9. Layer of rods and cones.10. Pigmented epithelium.11. Choroid layer.12. Scleral layer.

50 µm

1

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4

5

6

7

89

10

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SLIDE 11 Developing head coronal section at level of diencephalon and developing eyes.

Identify at low magnification :

1. Oral cavity.

2. Tongue.

3. Developing eyes.

4. Developing nasal cavity.

5. Mandible.

6. Other bones of skull.

7. Developing enamel organs.

8. Developing brain.

9. Eye-lids.

1.0 mm


Identify at low magnification :

1. Oral cavity.

2. Tongue.

3. Developing eyes.

4. Developing nasal cavity.

5. Mandible.

6. Other bones of skull.

7. Developing enamel organs.

8. Developing brain.

9. Eye-lids.

1.0 mm

1

2

33 4

5

6

7 7

5

8

69

9


Identify the main regions of the eye.

Care should be taken to distinguish between eye chambers and ‘space artefacts’.

250 µm

Identify : 1. Lens. 2. Cornea. 3. Iris. 4. Developing retinal layers. 5. Ciliary body. 6. Eye-lid. 7. Anterior chamber. 8. Vitreous humor. 9. Optic nerve, (may not be visible in all sections).


Identify the main regions of the eye.

Care should be taken to distinguish between eye chambers and ‘space artefacts’.

250 µm

Identify : 1. Lens. 2. Cornea. 3. Iris. 4. Developing retinal layers. 5. Ciliary body. 6. Eye-lid. 7. Anterior chamber. 8. Vitreous humor. 9. Optic nerve, (may not be visible in all sections). 9

8 7

6

5*

4

3*

21

6A : space artefacts

A

A

* Unclear due to distortion of tissue during fixation.


At a higher magnification identify:

1. Equator of developing lens. 4. Developing retina.

2. Lens anterior surface epithelium. 5. Cornea.

3. Optic nerve (may not be visible on all sections).

100 µm


At a higher magnification identify:

1. Equator of developing lens. 4. Developing retina.

2. Lens anterior surface epithelium. 5. Cornea.

3. Optic nerve (may not be visible on all sections).

100 µm

cornea

anterior epithelium of lens

E : equator of lensdeveloping retina

optic nerve

E

A : space artefacts

A

A


100 µm

How is the diameter of the lens controlled?


100 µm

How is the diameter of the lens controlled?

By the contraction and relaxation of the ciliary muscle.

cornea

lens capsule

cuboidal lens epithelium

developing retina

distortion due to fixation; developing iris and ciliary body displaced

artefact

proliferating cells at equator of lens


At high magnification identify: note the spatial differentiation of the lens fibre cells.

50 µm

The surrounding lens capsule is composed of basal lamina and collagen fibres.The cuboidal epithelial cells on the anterior surface have their bases facing the lens capsule and their apices facing the lens fibres.At the equator of the lens the cells elongate and differentiate into lens fibres forming the body of the lens. These run in an anterior-posterior direction.The fully differentiated fibres are hexagonal in cross section and have lost their nucleus and most cell organelles.

Demonstration slides with green labels

This set of slides is available during classes from the front bench in the teaching lab (or by request).

These slides are serial sections through the the head region of developing embryos.

They show stages in the early development of the eye and the ear.In the set can be found :

1. Very early stage in development of the eye.2. Slightly later stage of eye development.3. Very early stage in development of ear.4. Slightly later stage in ear development.

Remember; if you look at the slides, you will need to search for the section which shows best either the eye or ear. Try also to recognise some of the other developing structures sectioned.

SLIDE (green label) Early stage of developing eye

In the early embryo, the eyes arefirst seen as diverticulae developinglaterally from the diencephalon.

In this section only the opticdiverticulum on the right side can beseen.

These specimens are often cut at anoblique angle, so the eye on oneside will appear before its partner.

At this stage of development, the prominent flexure of the head regioncan result in the section going through both hind-brain and fore-brain (and sometimes the spinalcord).

250 µm


In the early embryo, the eyes arefirst seen as diverticulae developinglaterally from the diencephalon.

In this section only the opticdiverticulum on the right side can beseen.

These specimens are often cut at anoblique angle, so the eye on oneside will appear before its partner.

At this stage of development, the prominent flexure of the head regioncan result in the section going through both hind-brain and fore-brain (and sometimes the spinalcord).

250 µm

spinal cord

diencephalon

developingoptic vesicle

diocoel*

pharyngeal pouch

* diocoel ═ lumen of diencephalon


A few sections along on the same

slide and both developing optic

vesicles can be seen.

250 µm


A few sections along on the same

slide and both developing optic

vesicles can be seen.

250 µm

optic vesicle optic vesicle

diencephalon

blood vessels

SLIDE (green label) Early stage of developing eyeTwo adjacent sections from another of the slides showing the early stages in the

development of the eye.

The optic vesicles are well developed and due to the flexure in the head an area of

mid-hind brain can be seen.

Note the embryonic membranes.

100 µm

SLIDE (green label) Early stage of developing eyeTwo adjacent sections from another of the slides showing the early stages in the

development of the eye.

The optic vesicles are well developed and due to the flexure in the head an area of

mid-hind brain can be seen.

Note the embryonic membranes.

100 µm

wall ofdiencephalon

optic vesiclesamnion amniotic cavity

branches of vitelline vein

SLIDE (green label) Later stage of developing eyeThe diverticulae (seen in the previous

slide), invaginate to form the optic cup.

Producing the retina, ciliary layers and

iris.

The lens is formed from modified

epithelial cells; the surface ectoderm

overlying the optic cup.

250 µm

The apparent discontinuity betweenthe diencephalon and the retinal layer of the optic cup is because of the shape of the cup and the plane of the section.

SLIDE (green label) Later stage of developing eyeThe diverticulae (seen in the previous

slide), invaginate to form the optic cup.

Producing the retina, ciliary layers and

iris.

The lens is formed from modified

epithelial cells; the surface ectoderm

overlying the optic cup.

250 µm

The apparent discontinuity betweenthe diencephalon and the retinal layer of the optic cup is because of the shape of the cup and the plane of the section.

diencephalon

diocoel

anterior cardinal vein

lensoptic cup

retina

choroid layer

amniotic cavity

myelencephalon (with thin roof)

SLIDE (green label) Early stage of developing earThe otic vesicles arise from otic (auditory) placodes (areas of thickened ectoderm)

level with the posterior part of the brain.

These sink below the surface to form auditory pits becoming auditory or otic vesicles.

100 µm

SLIDE (green label) Early stage of developing earThe otic vesicles arise from otic (auditory) placodes (areas of thickened ectoderm)

level with the posterior part of the brain.

These sink below the surface to form auditory pits becoming auditory or otic vesicles.

100 µm

myelencephalon

OV : otic vesicles

amniotic cavity

neural tube

OV

OV

developing heart

SLIDE (green label) Early stage of developing ear

Again see how the appearance of the otic vesicles can vary in these serial sections.

100 µm


Previous section at a slightly higher magnification showing some of the associated

structures.

100 µm


Previous section at a slightly higher magnification showing some of the associated

structures.

100 µm

otic vesicle myelencephalon with thin roof

notochord

pharynx

internal carotid artery

anterior cardinal vein

vesicle closing

SLIDE (green label) Later stage of developing earThe auditory or otic vesicles, have lost their connection to the surface and are now

forming the inner portion of the ear.

The first pharangeal (hyomandibular) pouch will give rise to the Eustachian tube and

the chamber of the middle ear.

0.5 mm

SLIDE (green label) Later stage of developing earThe auditory or otic vesicles, have lost their connection to the surface and are now

forming the inner portion of the ear.

The first pharangeal (hyomandibular) pouch will give rise to the Eustachian tube and

the chamber of the middle ear.

0.5 mm

pharyngeal pouch

visceral arch

myelencephalon

OV : otic vesicles

OV OV

OVOV

pharyngeal pouch

SLIDE (green label) Later stage of developing ear

Note the close proximity of the first pharyngeal pouch to the otic vesicle.

Also note developing nerve fibres in the vicinity of the otic vesicle.

250 µm 100 µm


Note the close proximity of the first pharyngeal pouch to the otic vesicle.

Also note developing nerve fibres in the vicinity of the otic vesicle.

250 µm 100 µm

P : pharyngeal pouch

P

N : nerve fibre

N

N

otic vesicle


The same specimen, but a few sections along the slide.

Note the change in shape of the otic vesicle; early stages in the formation of the

semicircular canals.

Also note the more prominent nervous tissue/ganglia (arrowed).

250 µm 100 µm

Lecturer: Dr. MBS KisakaSlides and Stains: Monica Nambi

Documents

EYE & EAR ALL CONTENT IS COPYRIGHT © OF DR. STEEVNS M.B KISAKA THIS CONTENT MAY ONLY BE USED FOR EDUCATIONAL PURPOSES BY CURRENT STUDENTS OF MAKERERE