Neural Crest, Eye, and Ear Development

Eyes develop from four sources: neuroectoderm, surface ectoderm, mesoderm, and neural crest cells.

A pair of shallow grooves appear on the sides of the forebrain in a 22-day embryo.

Shallow grooves close and form optic vesicles which are outpocketings.

Optic vesicles touch the surface ectoderm inducing changes to form Lens vesicle.

Optic Vesicles invaginate to form a double-walled optic cup.

A gap in the developing eye that allows the hyaloid vessels to pass through.

Blood vessels that connect to the developing retina and later disappear.

A thickened area of surface ectoderm that develops into the lens.

The invaginated lens placode, which forms the lens.

Outer layer of the optic cup, that is colored and important for protecting the neural layer.

Inner layer of the optic cup, containing nerve cells and is essential for vision.

Part of the eye that adjust the shape of the lens to focus light.

Highly vascular, pigmented layer which nourishes the retina.

Specialized cells at the border of the developing neural tube that migrate to various locations in the body, forming diverse tissues.

The active movement of neural crest cells from the neuroectoderm to their target locations.

A congenital disease caused by the failure of neural crest cells to migrate properly to the intestines, resulting in an absence of nerves in a portion of the bowel, leading to constipation.

A condition where the large intestine is dilated (or enlarged), often due to absence of neurons in its wall, and affects bowel function.

Structures in the body derived from neural crest cells, including connective tissues, bones, nerve ganglia, and others.

Intestinal nerve networks crucial for proper bowel function; deficient in Hirschsprung's disease.

The region of the bowel lacking nerve cells in Hirschsprung's disease.

An embryological eye defect; a gap or fissure in the structures that develop into the lens or retinal parts.

The optic nerve, a tract of the diencephalon, isn't fully myelinated until 3 months after birth.

The optic nerve cannot regenerate if damaged.

The ear develops from thickened ectodermal placodes in the hindbrain, plus tissue from the first and second pharyngeal arches.

The first pharyngeal arch develops into the malleus and incus bones of the middle ear.

The second pharyngeal arch develops into the stapes bone of the middle ear.

The eardrum (tympanic membrane) is made of ectoderm from the first pharyngeal cleft, endoderm from the first pharyngeal pouch, and neural crest cells.

The inner ear's membranous labyrinth develops through the interaction of the rhombencephalon and surface ectoderm, which forms the otic placode.

The eardrum is made of three layers derived from two different germ layers.

The auricle (outer ear) develops from six mesenchymal swellings around the first pharyngeal cleft.

Deafness can be caused by defects in the inner ear, middle ear, or external ear.

Congenital abnormalities of the outer ear can include extra cartilage, underdevelopment, or complete absence.

Pharyngeal arches contribute to the formation of the neck and face.

Each arch has mesenchymal core, surface ectoderm, endoderm lining, neural crest cells, and mesoderm.

Pharyngeal arches give rise to muscles, nerves, and skeletal components of the face and neck.

The first pharyngeal arch has two parts - a dorsal maxillary process and a ventral mandibular process containing Meckel's cartilage.

The eye develops from contributions of neuroectoderm (retina, optic nerve, iris), surface ectoderm (lens, cornea), mesoderm (vascular and fibrous coats), and neural crest cells (choroid, sclera, cornea endothelium).

The earliest sign of eye development is seen in a 22-day embryo as a pair of shallow grooves on each side of the forebrain.

The optic vesicles come in contact with the surface ectoderm and induce changes, forming the lens vesicle. This vesicle ultimately differentiates into the lens of the eye.

Neural crest cells migrate into the mesenchyme and differentiate into the choroid, sclera, and corneal endothelium.

Each pharyngeal arch has a core of mesenchymal tissue, an outer layer of surface ectoderm, an inner lining of endoderm, migrating neural crest cells, and mesoderm.

Pharyngeal arches contribute to the formation of the neck and face, developing muscles, nerves, and skeletal components.

Meckel's cartilage is a structure found in the mandibular process of the first pharyngeal arch. It's a precursor to the lower jawbone.

The eardrum, or tympanic membrane, is formed by the interaction of the first pharyngeal cleft (ectoderm), first pharyngeal pouch (endoderm), and neural crest cells.

Pharyngeal clefts are grooves on the outer surface of the pharynx, separating the pharyngeal arches. Only the first cleft contributes to the formation of the external auditory meatus.

Pharyngeal pouches are inward folds of the pharyngeal wall, located on the inside of the pharynx. They develop into various structures like the middle ear and parathyroid glands.

The second pharyngeal cleft loses contact with the outside as it merges with the epicardial ridge in the lower neck. It's then overlaid by the second pharyngeal arch.

Auricular hillocks are six mesenchymal proliferations located around the first pharyngeal cleft. They contribute to the formation of the auricle (outer ear).

The double-walled cup formed from the invagination of the optic vesicle. The inner layer will become the neural layer of the retina, and the outer layer will become the pigmented layer.

The anterior portion of the inner wall of the optic cup that forms the inner layer of the iris.

The anterior portion of the inner wall of the optic cup that forms the ciliary body, which controls the shape of the lens.

The tough, white outer layer of the eye. It develops from the outer layer of mesenchyme surrounding the eye primordium.

The ear is formed from multiple sources. Thickened ectodermal placodes in the hindbrain contribute to the inner ear, while the first and second pharyngeal arches provide structures for the middle and outer ear.

The rhombencephalon, or hindbrain, plays a crucial role in inducing the development of the inner ear by interacting with the surface ectoderm.

The membranous labyrinth, the fluid-filled inner ear structure, originates from the ventral cochlear region of the otic vesicle. It develops into key components like the cochlear duct, saccule, utricle, and semicircular canals.

The first pharyngeal arch contributes to the malleus and incus bones of the middle ear, while the second arch forms the stapes. These bones are essential for transmitting sound vibrations.

The eardrum, or tympanic membrane, is a complex structure formed from ectoderm, endoderm, and neural crest cells. This intricate composition allows it to effectively transmit sound vibrations.

The malleus and incus, two of the three bones in the middle ear, are formed from the first pharyngeal arch. These bones play a critical role in transmitting sound vibrations from the eardrum to the stapes.

Specialized cells at the border of the developing neural tube that migrate to various locations in the body, forming diverse tissues.

Neural crest cells contribute to the formation of a wide range of structures, including connective tissues of the face and skull, various nerve ganglia, certain thyroid cells, the heart's conotruncal septum, odontoblasts, and more.

An embryological eye defect; a gap or fissure in the structures that develop into the lens or retinal parts.

Deafness that is present at birth, often caused by defects in the inner ear, middle ear, or external ear.

Each arch gives rise to distinct muscles, nerves, and skeletal components of the face and neck.