EMBRYONIC MEMBRANES -

Such animals are called amniota. Embronic membranes are of 4 types -

(i) Yolk sac -

It is formed below the embryo. It contains fluid (no yolk)

It is double layered, made up of outer mesoderm and inner endoderm. First organ to form R.B.C.

(ii) Amnion -

It encloses a fluid filled space amniotic cavity. It surrounds complete embryo.

The embryo is suspended in the amniotic cavity by an umbilical cord.

The main b.v. from the placenta reach the foetus through the umbilical cord.

Amniotic fluid is derived from the foetal kidneys & bladder i.e. it is foetal urine.

Amniocentosis is method to detect sex of foetus & chromosomal defects.

(iii) Allentoise -

A small sac., consists of endoderm inside & mesoderm outside. It is excretory in nature, stores nitrogenous waste.

(iv) Chorion -

It completely surrounds embryo, outerly made up of ectoderm & inner of mesoderm.