Differentiation of the Ectoderm

Parts of the Central Nervous System

Brain and Spinal Cord

Parts of the brain

cerebrum, cerebellum, and brainstem

Parts of the brainstem

midbrain, pons, and medulla

Formation of the Neural Tube

Neurulation

Primary Neurulation – the cells surrounding the neural plate direct the cells to (blank), (blank), & (blank) from the surface to form a hollow tube

proliferate, invaginate, pinch off

Secondary Neurulation – the neural tube arises from a (blank) that sinks into the embryo & subsequently hollows out (cavitates) to form a hollow tube

solid cord of cells

Steps in Primary Neurulation

Initial epithelium, columnarization, rolling/folding, closure, neural tube complete

Steps in Secondary Neurulation

dispersed mesenchyme, mesenchymal condensation, medullary cord/neural rod, epithelial transition/cavitation, neural tube complete

Neurulation in fish

exclusively secondary

Neurulation in Birds

the anterior portions of the neural tube are constructed by primary neurulation, while the neural tube caudal to the twenty-seventh somite pair (i.e., everything posterior to the hindlimbs) is made by secondary neurulation

Neurulation of amphibians

mostly, the neural tube is made by primary neurulation but the tail neural tube is derived from secondary neurulation.

Neurulation in mammals

both but secondary neurulation (begins at or around the level of somite 35)

Differentiation of the neural tube

gross anatomical level, tissue level, cellular level

what happens in gross anatomical level

the neural tube and its lumen bulge and constrict to form the chambers of the brain and the spinal cord

what happens in tissue level

the cell populations within the wall of the neural tube rearrange themselves to form the different functional regions of the brain and the spinal cord

what happens in cellular level

the neuroepithelial cells differentiate into the numerous types of nerve cells (neurons) and supportive cells (glia) present in the body

what forms in the gross-anatomical level?

lateral ventricles, third ventricle, cerebral aqueduct, fourth ventricle, and central canal of the spinal cord

what forms in the tissue level

lateral sulcus, frontal lobe, precentral Gyrus, central sulcus, postcentral Gyrus, parietal lobe, occipital lobe, temporal love, cerebellum, medulla oblongata, and pons

what forms in the cellular level?

neuron, oligodendrocyte, microglia, astrocyte

early mammalian neural tube is in what structure?

straight structure

before the posterior portion of the tube has formed, what starts undergoing drastic changes?

anterior portion

the neural tube balloons into three primary vesicles, what are those?

forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon)

3 primary vesicles

forebrain, midbrain, hindbrain

5 secondary vesicles

telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon

the forebrain forms what secondary vesicles?

telencephalon and diencephalon

the midbrain forms what secondary vesicle?

mesencephalon

the hindbrain forms what secondary vesicles?

metencephalon and myelencephalon

the telencephalon has 3 adult derivatives, what are these and their function?

olfactory lobes - smell

hippocampus - memory storage

cerebrum - association (“intelligence”)

the diencephalon has 4 adult derivatives, what are these and their function?

optic vesicle - vision (retina)

epithalamus - pineal gland

thalamus - relay center for optic and auditory neurons

hypothalamus - temperature, sleep, and breathing regulation

the mesencephalon has 1 adult derivative, what is this and its function?

midbrain - fiber tracts between anterior and posterior brain, optic lobes, and tectum

the metencephalon has 2 adult derivatives, what are these and their function?

cerebellum - coordination of complex muscular movements

pons - fiber tracts between cerebrum and cerebellum (mammals only)

the myelencephalon has 1 adult derivative, what is this and its function?

medulla - reflex center of involuntary activities

what are the parts of the vertebrate eye?

anterior chamber aqueous humor, choroid, cornea, fovea, iris, lens, optic nerve, retina, sclera, suspensory ligaments, vitreous humor, and vitreous chamber

The major sensory organs of the head develop from the interactions of the neural tube with a series of epidermal thickenings called the (blank)

cranial ectodermal placodes

the most anterior of the cranial ectodermal placodes are the

two olfactory placodes

what does the two olfactory placodes do?

form the ganglia for the olfactory nerves, which are responsible for the sense of smell

what cranial ectodermal placodes invaginate to form the inner ear labyrinth?

auditory placodes

the neurons of auditory placodes form the (blank), which enables us to hear

acoustic ganglion

what is in direct contact with the optic vesicle?

presumptive lens placode

what does the optic vesicle acocmplish?

the activation of the head ectoderm's latent lens-forming ability and the positioning of the lens in relation to the retina

what does the optic vesicle turn into?

two-walled optic cup, whose two layers differentiate in different directions

the cells of the outer layer of the optic cup produce (blank)

melanin pigment

the melanin pigment produced becomes the?

pigmented retina

one of the few tissues other than the neural crest cells that can form this melanin pigment

outer layer of the optic cup

The cells of the inner layer proliferate rapidly and generate a variety of (blanks - 4)

glia, ganglion cells, interneurons, and light-sensitive photoreceptor neurons

the glia, ganglion cells, interneurons, and light-sensitive photoreceptor neurons collectively constitute what?

neural retina

these are neurons whose axons send electrical impulses to the brain

retinal ganglion cells

the axons of the retinal ganglion cells meet at the base of the eye and travel down the optic stalk called?

optic nerve

other term for goosebumps

piloerection, cutis anserina, and horripilation

define the parts numbered

1. epidermis

2. arrector pili muscle

3. hair follicle (root)

4. dermis

in most vertebrates it shortly becomes a two-layered structure

presumptive epidermis

explain the image

This image illustrates an experiment showing how embryonic cells can self-organize based on their identities. Scientists took two types of cells from an early embryo—presumptive epidermal cells (which will form skin) and neural plate cells (which will form the nervous system)—and separated them. After mixing these dissociated cells together, the cells were allowed to reaggregate on their own. Remarkably, the cells sorted themselves out: the neural cells moved to the inside, and the epidermal cells moved to the outside, forming a layered structure similar to how tissues naturally organize during development. This demonstrates that cells have intrinsic properties and recognition mechanisms that guide them to assemble into the correct structures, even without external instructions.

the outer layer of the epidermis gives rise to the?

periderm

a temporary covering that is shed once the inner layer differentiates to form a true epidermis

periderm

the periderm is a temporary covering that is shed once the inner layer differentiates to form a (blank)

true epidermis

the inner layer of epidermis is called?

basal layer or stratum germinativum

the basal layer is a (blank) that gives rise to (blank) of the cells

a germinal epithelium that gives rise to all the cells of the epidermis

the basal layer divides to form what?

spinous layer

what are the two epidermal layers of the Malpighian layer?

basal layer and spinous layer

the cells of the Malpighian layer divides to produce what?

granular layer

granules of the protein keratin

granular layer

the cells of the granular do not divide, but differentiates into epidermal skin cells called?

keratinocytes

the keratin granules become more prominent as the keratinocytes of the granular layer (blank) and (blank) to form the what?

age and migrate outward; cornified layer or stratum corneum

the cornified layer becomes what of keratin protein?

flattened sacs of keratin protein

what happens to the nuclei of the cornified layer?

nuclei are pushed to one edge of the cell

what are the parts of the dermis?

keratohyaline granule, desmosome, desquamating cell, stratum corneum, granular layer, spinous layer, and basal layer