UNSW Embryology ANAT 3311 Notes Session 2 SYSTEMATIC EMBRYOLOGY					Embryology Home Page
	Lecture notes from the Anat 3311 1997 Science Embryology course compiled and written by Dr Mark Hill. Some notes derived from historic class notes.
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DEVELOPMENT OF THE ORGANS OF SPECIAL SENSE (ORGANS OF VISION, AUDITION, EQUILIBRIUM AND OLFACTION).

Reading Moore Ch19: p423-439 Larson Ch12: p309-359

Computer Activities

Embryo Images Unit: Eye Development, Ear Development

UNSW Embryology: Human Systems, Human Selected(optic nerve, optic retina, lens), Head Set

Pig Head Set,

Listed selected sections (Eye, Ear)

Objectives

1. Understand the early development of the eye, defining optic vesicles, optic stalks, optic fissure, optic cups, lens placodes and lens vesicles.

2. Understand the development of the retina, ciliary body, iris, lens, choroid, sclera and cornea.

3. Understand the development of external, middle and internal ear, including otic placode, otocyst, endolymphatic duct and semicircular canals.

Learning activities

1. Identify the eye in the 6mm pig, and 27mm human embryo microfiche cards.

2. Examine developing eye in slide No.56.

3. Identify the developing ear (external, middle and inner) in the 6mm pig and 27mm human embryo microfiche cards.

Self Assessment Questions

1. Describe the main steps in the development of the lens.

2. Describe the development of the retina.

3. Compare the optic nerve with other cranial nerves.

CENTRAL NERVOUS SYSTEM REVIEW EXERCISES

1. Using simple sketches describe the development of the spinal cord, the dorsal root ganglia and spinal nerves.

2. Construct and label simple diagrams showing the early development of the C.N.S. Define the following terms :

Term	Definition
Neural plate
Neural groove
Neural folds
Neural crest
Neuropores
Primary and secondary brain vesicles

3. Illustrate the development of the pituitary.

4. Prepare labelled diagrams of the early development of eyes. Define the following terms:

Term	Definition
Optic grooves
Optic vesicles
Optic stalks
Optic fissures
Optic cups
Lens placodes

5. Briefly describe the development of the retina.

6. Briefly describe the development of the Inner, Middle and External Ears. Define the terms:

Term	Definition
Otic placode
Otic pit
Otic vesicle (otocyst)
Endolymphatic duct and sac
Semicircular ducts

7. What elements of the C.N.S. and peripheral nervous system are derived from the neural crest?

EYE

Human Embryo

A7: Mesencephalon. Rostral extensions of superior cardinal vein

B1: Developing diencephalon. Rathke's pouch. Lens pit (derived from thickened ectoderm of lens or "optic" placode).

B2,B3: Optic cup with optic ventricle. Note unequal thickness of walls of optic cup (inner wall; sensory retina: outer wall; pigment epithelium). Lens pit. Note position of eye with respect to maxillary arch. Hyaloid vessels near ventral margin of optic cup.

B4: Junction of optic stalk to wall of prosencephalon (diencephalon). Small branches of hyaloid blood vessels in region between lens pit and optic stalk.

B5: Continuity of optic ventricle and single forebrain ventricle via optic stalk. Note proximity of eye to nasal placode (R).

B6: Hyaloid vessels ventral to optic stalk. Optic mesenchyme (mesectoderm) arising directly from epithelium of dorsal surface of optic cup. Nasal placodes.

B7: Tangential section through optic cup, with surrounding optic mesenchyme. Nasal

placode Interorbital ligament. Bridge of nose.

A6:Interorbital ligament. Nose. uppereyelids. Cornea. Anteriorchamber. Lens. Vitreous body. Sensory retina. optic ventricle (artefact). Pigment epithelium. Conjunctival

sac. Primordium of lacrimal glands (near lateral fornix of conjunctival sac).

A7: Medial rectus m. Primordium of nasolacrimal ducts. Upper eyelid (lateral). Lower eyelid (medial).

B1: Optic nerve. Note extensive temporal region of retina. Primordium of nasolacrimal ducts.

B2: Medial and lateral rectus m. Pigment epithelium. Note relationship of eye to nasal capsule, sphenoid cartilage and trigeminal ganglion. Primordium of nasolacrimal ducts (cut obliquely).

B3: On L, note course of maxillary division of trigeminal in relation to position of eye (superior to this level).

Human Embryo (selected sections)

A3,A4: Optic ventricle (artefactually enlarged). Optic nerve. Sensory retina. Pigment epithelium. Choroid and sclera (not separable).

A5: Sensory retina with optic nerve fibre layer and young retinal ganglion cells. note radial orientation of deeper retinal cells. Pigment epithelium. Sclera plus choroid.

A6: Anterior corneal epithelium and posterior corneal endothelium. Corneal stroma. Angle of anterior chamber with developing trabecular meshwork. Anterior and posterior lens epithelium. Note change in height of lens cells at the equator of the lens. Double-layered epithelium of iris arising from rim of optic cup. Stroma of iris lies anteriorly across lens. Kink in internal wall of optic cup indicates site where the ciliary body will form.

EAR

Pig Embryo

Al: Thin caudolateral walls of rhombencephalon.

A2: Otocyst (R). Apex of otocyst (anlage of L endolymphatic sac)

A3: Otocyst; surrounding mesenchyme = otic capsule. Note proximity of otocyst to wall

of rhombencephalon. Superior glossopharyngealganglion. Vestibulo-cochlear-facial ganglion complex (R). Trigeminal ganglion.

A4: Indentation in rostral margin of otocyst = anlage of utriculosaccular canal. Note alignment of superior cardinal vein (LS) in relation to the nerve trunks (XS). Trigeminal ganglion. Dorsal end of 1st pharyngeal arch and groove. Note variation in height of cells of L otocyst wall.

A5: Facial ganglion (R). "Floor" of L otocyst. Note on R, the former position of the otocyst in relation to the 2nd pharyngeal arch.

A6: 1st, 2nd arches, grooves and pouches on R. Inferior glossopharyngeal and facial ganglia on L.

A7,B1: 1st pharyngeal pouch opening into pharynx.

Human Embryo

B3: Rhombic lip (developing cerebellum). IVth ventricle. Trigeminal ganglion. Adenohypophysis. Sphenoid cartilage.

B4: Cochlear duct and temporal cartilage. Semicircular duct (ampulla on L). precartilage

of auricle (pinna). malleus (medial, L). Incus (lateral, L).

B5: Extemal auditory meatus. Auricle. Incus (dorsal). Malleus (ventral). Tubotympanic

recess (auditory rube). Tensor tympani m. (L). Utricle. Semicircular ducts. Intemal auditory meatus (R), containing vestibular and spiral ganglia. Endolymphatic sac (L). Note proximity of sac to choroid plexus of 4th ventricle.

B6: External auditory meatus. Primordium of tympanic membrane (L). Manubrium of malleus

(L). Basal turn of cochlea duct (L). Endolymphatic sac (R). Common crus (R). Junction of utricle and saccule (R). Meckel's cartilage. Stapes (R). Auditory tube.

Human Embryo (selected sections)

B3,B5: Cochlear duct. Spiral ganglion. Tubotympanic recess (auditory tube). Internal carotid artery. Malleus and incus. Meckel's cartilage. Tensor tympani muscle. Crista ampullaris of a semicircular duct. Semicircular duct. Utricle with macula. Saccule (cut tangentially) adjacent to utricle. Otic capsule.

B6: Turns of cochlea duct. Note changes in height of the wedge-shaped epithelial cells at different sites in wall of cochlear duct; the region of tallest cells is the anlage of Corti's organ and the clear luminal cytoplasm is the origin of the tectorial membrane; the thickening on the outer wall of the cochlear duct is the origin of the stria vascularis; the thinnest part of the wall is the origin of the vestibular membrane. Spiral ganglion in modiolus. Vestibular ganglion (collectively VIII cranial nerve ganglion - both parts composed of bipolar neurones). Saccule. Temporal cartilage. Internal auditory meatus.