Where do placodes originate?

Olfactory epithelium The placodal precursor cells are initially located in the lateral anterior neural plate and form as identifiable placodes by anterior convergence. Thus, it appears that the olfactory placodes originate in the neural plate, rather than the ectoderm.

What do ectodermal placodes become?

A neurogenic placode is an area of thickening of the epithelium in the embryonic head ectoderm layer that gives rise to neurons and other structures of the sensory nervous system. Placodes are embryonic structures that give rise to structures such as hair follicles, feathers and teeth.

How do placodes form?

The cranial placodes are localized ectodermal thickenings that develop by apicobasal elongation of cuboidal cells in the inner layer of the ectodem in the head of vertebrate embryos. They are involved in formation of sense organs (eye, nose, ear) and cranial sensory ganglia.

Is the olfactory Placode a neurogenic Placode?

20.1. Almost all placodes can be classified into two groups, namely (a) the neurogenic placodes and (b) the olfactory, lens, and otic placodes that contribute to sensory organs. The olfactory placode emerges in front of the neural plate adjacent to the forebrain and invaginates to form olfactory pits.

Is dermis an ectoderm?

Organs derived from ectoderm. The surface ectoderm (or external ectoderm) forms the following structures: Skin (only epidermis; dermis is derived from mesoderm) (along with glands, hair, and nails) Epithelium of the mouth and nasal cavity and glands of the mouth and nasal cavity.

How Prechordal plate is formed?

The prechordal plate is a thickening in the endodermal layer which is formed by mesendodermal cells from the primitive node that migrate rostrally along the midline between the ectoderm and endoderm layers. These same cells also form the notochord.

What is the Neuroectoderm?

: embryonic ectoderm that gives rise to nervous tissue.

What is a neurogenic placode?

Neurogenic placodes are specialized regions of the embryonic ectoderm that are central to the development of the cranial sensory systems of vertebrates. These structures generate many of the sensory neurones of the head and also, in some instances, the associated sensory receptor cells.

What is derived from mesoderm?

The mesoderm gives rise to the skeletal muscles, smooth muscle, blood vessels, bone, cartilage, joints, connective tissue, endocrine glands, kidney cortex, heart muscle, urogenital organ, uterus, fallopian tube, testicles and blood cells from the spinal cord and lymphatic tissue (see Fig. 5.4).

Which is derived from ectoderm?

The tissues derived from the ectoderm are: some epithelial tissue (epidermis or outer layer of the skin, the lining for all hollow organs which have cavities open to a surface covered by epidermis), modified epidermal tissue (fingernails and toenails, hair, glands of the skin), all nerve tissue, salivary glands, and …

What is the prechordal plate derived from?

mesendodermal cells
The prechordal plate is a thickening in the endodermal layer which is formed by mesendodermal cells from the primitive node that migrate rostrally along the midline between the ectoderm and endoderm layers. These same cells also form the notochord.

What does placode stand for in medical terms?

The term placode refers to ectoderm thickenings in the cranial region that have important roles in development of special sensory and other systems. There are also integumentary placodes that are involved with hair follicle development covered on a separate content page.

When does the ectodermal placode begin to develop?

Note that a second, later developing, form of ectodermal placode development occurs with the development of hair, gland, feather (other species), follicles associated with integumentary specialisations. This topic does not directly relate to the specialised placodes of the head region covered here. (More? hair | integumentary )

Where do neural crest and cranial placodes come from?

Some Recent Findings. These structures are primarily derived from two embryonic cell populations the neural crest and cranial placodes, respectively. Anos1 was identified as a target of Pax3 and Zic1, two transcription factors necessary and sufficient to generate neural crest and cranial placodes.

Where are the placodes located in the developing head?

Note that their initial postion on the developing head is significantly different to their final position in the future sensory system. Otic placodes – the first placodes visible on the surface of the embryo. Olfactory (Nasal) placodes – has 2 components (medial and lateral) and will form the nose olfactory epithelium.