Sem 1

ventricles

4 fluid filled cavities that produce, store and circulate cerebrospinal fluid to cushion and protect the central nervous system. CSF surrounds the brain, forming a protective layer and suspedns brain in fluid.

formation of primitive streak

zygote

initial, diploid cell when sperm cell fuses with egg cell

holds whole genetic blueprint for child, and is the ultimate stem cell “the mother cell” where it is capable of dividing and differentiating itno every. cell type in the human body,

no longer a zygote when it undergoes its first cell division, roughly a day to a day annd a half after conception

phase 1 of embryonic journey (days 1-6)

-sperm fertilizes egg in fallopian tube (zygote!)

• travels through fallopian tube towards uterus, undergoing cell division without becoming larger

• becomes a mulberry, solid ball of 16-32 cells called a morula

  • the morula enters the uterus, fluid pumps into it and a cavity is created. now a blastocyst

  • blastocyst, divided into two disticnt parts of inner (embryo) and outer (placenta)

phase 2: days 7-14, landing and organizing

• blastocyst hatches and implants itself onto uterus

• inner cell mass flattens itself into a two layered pancake called the bilaminar embryonic disc

• the epiblast, top layer, faces the yolk sac

  • hypoblast, bottom later, faces the amniotic sac

phase 3: days 15-18

3 weeks from conception, primitive streak appears on the surface of epiblast layer, caudal end. establishes axis of the body (left, right, head and tail)

3 spaces- front (yolk, digestive), back (amniotic, spine), fluid surround (chorion)

cells move to and organize within the groove of primitive streak.

the 3 layers of cells within the primitive streak make up the 3 derms. this is gastrulation

3 derms

endoderm - inner layer inside primitive streak, GUT, digestive tract, organs

mesoderm- middle layer, HEART, connective tissues, notochord, muscles, reproductive

ectoderm - top layer, HEAD, hair, nails, teeth, nervous system

days 19-22, setting the axis and rod

notochord formation - cells create a solid, flexible, midline rod made of cartilage like tissue in the mesoderm.

primitive streak starts to dissolve, pull back towards the tail

ectoderm thickens into a neural plate

neuralation

formulation of the neural tube, which gives rise to neural tissue.

flat neural plate begins to elevate, rising up like waves to create neural folds

the gap between the rising folds, the waves, is the neural groove.

these neural folds eventually meet in the middle and zip shut, forming a hollow cylinder that is the neural tube

• neural tube forms brain and spinal cord

• somites develop around the neural tube to create the spine

  • gut tube created by downward wave

dermatome

dermis

myotome

skeletal muscle

sclerotome

vertebrae

transverse foramen

bony canal on cervical vertebrae, within transverse process

transmit the vertebral artery, vertebral vein, sympathic nerve plexus