Cranial Placodes Found in Humans
The cranial placodes that have neurogenic potential (i.e. give rise to neurons) can be divided into two groups, the dorsolateral places and the epibranchial placodes.
- dorsolateral placodes includes:
- The trigeminal placode, which consists of ophthalmic and maxillomandibular parts, and gives rise to the cells of the trigeminal ganglion
- The otic placode forms the otic pit and the otic vesicle, giving rise eventually to organs of hearing and equilibrium.
- The epibranchial or epipharyngeal placodes generate the distal portion of the ganglia of cranial nerves VII, IX and X:
- The geniculate placode, associated with the first branchial cleft, generates the geniculate ganglion and distal parts of cranial nerve VII
- The petrosal placode, associated with the second branchial cleft, generates the glossopharyngeal ganglion and distal parts of cranial nerve IX
- The nodosal placode, associated with the third branchial cleft, generates the nodose ganglion and distal parts of cranial nerve X
- The olfactory placode (or nasal placode) gives rise to the olfactory epithelium of the nose.
- The cranial placodes that do not give rise to neurons are:
- The lens placode under the direction of the optic vesicle gives rise to the lens of the eye.
- The adenohypophyseal placode, which forms the anterior lobe of the pituitary gland.
Read more about this topic: Neurogenic Placodes
Famous quotes containing the word humans:
“So they took soot from the kiln, and stood before Pharaoh, and Moses threw it in the air, and it caused festering boils on humans and animals.”
—Bible: Hebrew, Exodus 9:10.