Chapter 16 Flashcards
_______ are temporary local thickenings of the ectoderm in head and neck
cranial placodes
Cranial placodes are formed from cells near the anterior borders of the forming ___1___, between the prospective ___1___ and the _______
neural tube
epidermis
The cells surrounding the neural plate can be specified to one of several fates depending on the timing and extent of _______ and _______ signals
Wnt
BMP
Neural plate specification:
both Wnt and BMP for extended period of time forms _______
epidermis
Neural plate specification:
If Wnt induces BMP and then is down-regulated, _______ cells will form
placodal
What are the 3 placodal specifier genes?
1) six1
2) six4
3) Eya2
Neural plate specification:
If Wnt induces BMP and then remains active, _______ cells will form
neural crest
What are the three neural crest cell specifier genes?
1) Pax7
2) Snail 2
3) Sox9
Neural plate specification:
If just wnt is received, ________ cells will form
neural cells
Otic (ear) placode of Gallus gallus:
1) _______ is secreted by a portion of the pharyngeal endoderm
2) This induces the overlying cranial paraxial mesoderm to secrete_______
3) Then this induces the neural plate to secrete the paracrine factors _______ and _______
4) These two paracrine factors synergistically activate _______ and others that allow the cells to produce the otic placode and become sensory cells
1) fgf8
2) fgf19
3) wnt8c, fgf3
4) snail2
People who are known to have _______ syndrome, an X-linked disease characterized by anosmia, small genitalia, and sterile gonads
kallmann
The small gonads and genitalia are the result of a lack of _______, which is a peptide hormone secreted by the hypothalamus that instructs the anterior pituitary to secrete luteinizing hormone, the hormone required for gonadal development and genital maturation.
gonadotropin-releasing hormone (GnRH)
- originate in the olfactory epithelium, the same place as olfactory receptor neurons
During neurulation, extension of the optic vesicle from the _______ to just beneath the head ectoderm, induces the competent ectoderm to form a localized thickening called the _______
diencephalon
lens placode
The optic vesicle bends to form the 2 layered optic cup:
1) The outer layer produces melanin and becomes the _______
2) the inner layer proliferates to generate neurons and glial cells forming the _______
pigmented retina
neural retina
The lens placode invaginates to form the _______
lens
- originates from the ectoderm
The lens continues to round into its final shape allowing it to focus light on the retina, and it contains a transparent protein called _______
crystallin
Lens shaping is balanced by:
_____-generated constriction of microfilaments
_____-generated actin polymerization extends microtubules
1) Rho
2) Rac
The _______ is induced from surface ectoderm by the lens forming beneath it
Cornea
Mesenchymal Neural crest cells secrete a cornea-specific ECM into a layer of _______ laid down by the initial Corneal cells
collagen
_______ protects the cornea from reactive oxygen throughout life
ferritin
- an iron binding protein
All the components of the retina (ex rods, cones, ganglion, bipolar cells, horizontal cells, amacrine cells) are generated by _______ of the early retina
neuroblast
On the tips of the optic cup on either side of the lens, a muscular _______ forms between the lens and cornea, which allows the amount of light entering the eye to be controlled.
Iris
- from ectoderm
_______ is formed at the junction of neural retina and iris, which secretes _______
ciliary body
aqueous humor
- nutrition for lens
- creates pressure needed to stabilize the curvature of the eye and maintain distance between lense and cornea
What are 2 reasons why babies can’t see that well?
1) less photoreceptors
2) photoreceptors are bigger
