EYEBy: Kamel

IrisCorneaCiliary BodyRetinaChoroid

Competence: Eyes in face

Vertebrate EyeWhat inductive event initiates eye formation?

Tunica Vasculosa Lentis

Lens placoda is a result of series inductive interaction with pharyngeal endoderm, heart mesoderm, neural crest, and optic vesicle

Vertebrate EyeHow does cornea and lens differentiate?

Organization of Lens Epithelial And Differentiating Fiber Cells

12.32 Differentiation of the lens and the anterior portion of the mouse eye (Part 1)

12.32 Differentiation of the lens and the anterior portion of the mouse eye (Part 2)

IrisThe ciliary muscle develops from paraaxial mesoderm. The ciliary muscles become evident by third month and is gradually differentiated into longitudinal, oblique and circular muscles. The ciliary epithelium is neuro ectodermal in origin. It develops from the lips of the optic cup. The outer layer is pigmented while the inner layer is non pigmented the ciliary epithelium give rise to 70-75 ciliary processes

Vertebrate EyeInto what type of structure does the neural retina differentiate?

EAR

Development of the otocyst.Barald K F , Kelley M W Development 2004;131:4119-4130

Development of the otocyst :(A) Cross-section through a developing embryo at the level of the hindbrain (dorsal towards the top). The otic placode forms as a thickening of the surface ectoderm (blue) adjacent to the hindbrain (HB) and notochord (NC). The space between the hindbrain and the surface ectoderm is populated by periotic mesenchymal cells and some neural crest cells (pink). (B) As development continues, the placodes pinch off to form otic vesicles (purple). (C) Soon after closure of the otocyst (purple), neuroblasts (yellow), which give rise to the statoacoustic ganglion, delaminate from the anteroventral surface of the otocyst. (D) Next, the otocyst undergoes elaborate morphogenetic changes, including the dorsal extension of the endolymphatic ducts (ED), which will terminate in the endolymphatic sacs (not shown), in the dorsal region of the developing otocyst and the cochlear duct (CD) in the ventral region. (E) As development continues, the cochlear duct begins to coil and the semicircular canals (SSC) begin to form in the dorsal region of the ear. Developing sensory patches are illustrated in green. At the same time, periotic mesenchymal cells (pink) condense around the developing ear to form the bony labyrinth.

Kelley Nature Reviews Neuroscience 7, 837849 (November 2006) | doi:10.1038/nrn1987

All the structures in the inner ear develop from an otic placode that invaginates to form the spherical otocyst by E9.5. Soon after closure of the otic pit to form the otocyst, neuroblasts delaminate from its ventral region. These neuroblasts will coalesce adjacent to the developing inner ear and begin to form the statoacoustic ganglion (SAG). By E10.5, the otocyst begins to change shape as a result of the formation of dorsal and ventral protrusions that will ultimately develop as the endolymphatic duct (ED) and the cochlear duct (CD). By E12.5, the developing semicircular canals, anterior (ASC), posterior (PSC) and lateral (LSC) can be identified. Each canal forms as a flattened outgrowth from the otocyst. The central portion of each outgrowth ultimately undergoes a period of cell resorption (speckled regions) to form the mature canal phenotype. In addition, the positions of the developing sensory patches can be identified, and the developing cochlear duct begins to form a spiral. At E13.5, the cochlear duct has completed approximately three-quarters of one turn and the neurons in the developing SAG have extended dendrites that will form contacts with developing hair cells in all of the sensory epithelia. Between E15.5 and E17.5, different regions of the inner ear continue to grow and expand, including the cochlea, which reaches its mature length of approximately one and three-quarter turns, and the semicircular canals. Modified, with permission, (1998) Society for Neuroscience

Development of the scala tympani and scala vestibuli. A. The cochlear duct is surrounded by a cartilaginous shell. B. During the 10th week large vacuoles appear in the cartilaginous shell. C. The cochlear duct (scala media) is separated from the scala tympani and the scala vestibuli by the basilar and vestibular membranes, respectively. Note the auditory nerve fibers and the spiral (cochlear) ganglion.

Ectodermal PlacodeSeveral area of ectoderm in the head region are induced by underlying parts of the brain to form Placodes

The Otic Placode Forms the Inner Ear

*Pax6 : protein appears to be important in making the ectoderm competent to respond to the inductive signal from the optic vesicle

*Optic vesicle extending from diencephalon induces formation of lens placode from overlying head ectodermoptic vesicle become two-layered optic cup pigmented and neural retinaaxons of ganglion cells of retina form optic nervethree transcription factors, Six3, Pax6 and Rx1 expressed in anterior end of neural plate where optic vesicles formseparation of single eye field into two fields is accomplished by sonic hedgehog protein believed to suppress Pax6 expression in center of embryoOptic (choroid) fissure sulcus on ventral aspect optic cup/stalk(allows passage of vasculature to lens & layers of cup)*Vessels of pupillary membrane**rounded up lens induces overlying ectoderm to differentiate into cornea intraocular fluid pressure needed for proper curvature of cornea to focus light on retinadifferentiation of lens into transparent membrane involves changes in cell shape, size and synthesis of crystallins*devbio8e-fig-12-32-1.jpg *devbio8e-fig-12-32-2.jpg *three layers of cells are formed, photoreceptor cells (rods and cones), bipolar neurons, and ganglion cellsDevelopment of the otocyst. (A) Cross-section through a developing embryo at the level of the hindbrain (dorsal towards the top). The otic placode forms as a thickening of the surface ectoderm (blue) adjacent to the hindbrain (HB) and notochord (NC). The space between the hindbrain and the surface ectoderm is populated by periotic mesenchymal cells and some neural crest cells (pink). (B) As development continues, the placodes pinch off to form otic vesicles (purple). (C) Soon after closure of the otocyst (purple), neuroblasts (yellow), which give rise to the statoacoustic ganglion, delaminate from the anteroventral surface of the otocyst. (D) Next, the otocyst undergoes elaborate morphogenetic changes, including the dorsal extension of the endolymphatic ducts (ED), which will terminate in the endolymphatic sacs (not shown), in the dorsal region of the developing otocyst and the cochlear duct (CD) in the ventral region. (E) As development continues, the cochlear duct begins to coil and the semicircular canals (SSC) begin to form in the dorsal region of the ear. Developing sensory patches are illustrated in green. At the same time, periotic mesenchymal cells (pink) condense around the developing ear to form the bony labyrinth.Patches columnar ephitelium in a more squamous backgroundPlacode form parts of eye, ear, & nose**