(c) Cleavage in the human zygote is holoblastic i.e. it divides the zygote and the blastomeres completely into daughter cells.
But it is unequal as the blastomeres differ in size.
(b) An organizer is a signal aligning center that directs the development of embryo or part of embryo, e.g. in amphibians, it is dorsal tip of blastophore.
(b) Foetal ejection reflex in human female is induced by fully developed foetus and placenta.
When a woman is in a lithotomy or semi-sitting position, the Foetal Ejection Reflex is impaired and the increased pain caused by the sacrum's inability to move as the baby descends can be intolerable.
(c) Sertoli cells in seminiferous tubules provide nutrition and support to developing spermatids.
(b) In human beings, after one month of pregnancy, the embryo's heart is formed.
By end of second month pregnancy, the foetus develops limbs and digits.
By end of 12 weeks, major organ systems are formed.
After fifth month, the first movement of foetus and appearance of hair on its head are observed.
By the end of 24 weeks, the body is covered with hairs, eye lids separate and eyelashes are formed.
(b) Parturition is the process of delivery of the foetus.
The signals for parturition originate from the fully developed foetus and placenta that induce uterine contraction called foetal ejection reflex.
This triggers the release of oxytocin hormone from pituitary.
This in turn leads to expulsion of the baby out of uterus.
(a) In vitro fertilization is a process where fertilization of an egg occurs outside the mother's womb.
This method is used as a major treatment for infertility.
This method involves the removal of eggs from the female ovaries.
This egg is then allowed to fertilize with sperm in a fluid medium in a test tube.
The zygote is allowed to develop for a week.
Either zygote or early embryo up to 8 blastomeres is then transferred into the uterus to complete its further development.
If the embryo is with more than 8 blastomeres, it is transferred into uterus for successful pregnancy.
A baby conceived by fertilization that occurs outside mother body is called test tube baby.
(b) Correct sequence: Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Urethral meatus.
Identify the human developmental stage shown below as well as the related right place of its occurrence in a normal pregnant woman, and select the right option for the two together.
Developmental stage Site of occurrence
(c) Blastocyst is a thin-walled hollow structure in early embryonic development that contains a cluster of cells called the inner cell mass from which the embryo arises.
The outer layer of cells gives rise to the placenta and other supporting tissues needed for fetal development within the uterus while the inner cell mass cells give rise to the tissues of the body.
The blastocyst reaches the womb (uterus) around day 5 , and implants into the uterine wall on about day 6 .
(a) The signals for child birth (parturition) originate from the fully matured foetus and placenta which induce mild uterine contractions called foetal ejection reflex.
