The peculiarities of optic nerve

The peculiarities of optic nerve

1.      It is not a peripheral nerve but a prolongation of white matter of the brain

2.      Peripheral neuropathies like Guillain–Barré syndrome do not affect the optic nerve.

3.      the epineurium, perineurium, and endoneurium found in peripheral nerves but not is optic nerve

4.      optic nerve are incapable of regeneration, and, hence, optic nerve damage produces irreversible blindness..

5.      It is  covered by three meninges of brain with subdural and subarchnoid spaces

6.      Myelination of the optic nerve is derived from the oligodendrocyte and not from the Schwann cells

7.      Plial sheath projects into the substances of the nerve as numerous septa.

8.      The subject of the blood supply of the optic nerve. The circulation of the posterior ciliary artery is the main source of blood supply to the optic nerve, except for the surface nerve fiber layer which is supplied by the retinal circulation.

Syncytotrophoblast

Syncytotrophoblast

Outer layer of trophoblast, It is not stem cells so it can not differentiated to other cell types.

It invades the wall of uterus and establishes nutritional supply between mother to fetus

It produces terminally differentiated cell. This tissue is specialized and it is  multinucleated with no individual cell

The syncytiotrophoblast secretes progesterone and leptin in addition to human chorionic gonadotropin (hCG) and human placental lactogen (HPL); hCG prevents degeneration of the corpus luteum.

Cytotrophoblast

Cytotrophoblast

it is the inner layer of trophoblast . It is situated into interior of  the syncytiotrophoblast and external to the wall of the blastocyst in a developing embryo.

It is the trophoblastic stem cells which has  important role in implantation. It is not establishes nutritional supply between mother to fetus

It can differentiated into other types of cells. This tissue  is formed by individual cells.

This layer does not produce hormones

Formation and fate of trophoblast

Formation and fate of trophoblast

As cleavage proceeds the ovum comes to have 16 cells. this is known as morula.
The morula consists of an inner cell mass that is completely surrounded by an outer layer of cells. The cells of the outer layer later give rise to trophoblast

Fate :
It divides into two layers outer and inner. The inner one is cellular and called as cytotrophoblast. The outer one having no cell boundary is termed syncytotrophoblast . these two together with primary mesoderm constitute chorion .

Sign of mature fetus

Sign of mature fetus

• Dry, loose, peeling skin,smooth, pink and covered with vernix caseosa
• Overgrown nails.
• Large amount of hair on the head.
• Visible creases on palms and soles of feet.
• Small amount of fat on the body.
• Green, brown, or yellow coloring of skin from baby passing stool in the womb.
• More alert and "wide-eyed", moves and cries vigorously when born
• Creases on baby’s palm and sole
• Lanagu absent from most situations