<span>The afferent nerve fibres of the olfactory receptor neurons transmit nerve signal about odours to the CNS. From the olfactory mucosa (inside the nasal cavity), the nerve travels up through the cribriform plate of the ethmoid bone where the fascicles enter the olfactory bulb<span>. The olfactory</span> bulb is a structure which contains specialised neurones, called mitral cells and the nerve fibres synapse with those mitral cells, forming collections known as synaptic glomeruli. From the glomeruli, second order nerves then pass into the olfactory tract which runs to the CNS (</span>primary olfactory cortex).
In humans, the yolk sac is the
site of origin for blood cells and primordial germ cells. The human yolk sac is
a membrane located outside the embryo and it is connected by a tube through the
umbilical opening to the embryo's midgut. The yolk sac serves as an early site
for the formation of blood and in time, is incorporated into the primitive gut
of the embryo.
It's because of hydrogen bonding among water molecules
