When and where do chorionic villi appear in humans? State their function.


Chorionic villi appear on the trophoblast after implantation. Chorionic villi interdigitate with the uterine tissues and jointly forms the placenta which is a structural and functional unit between developing embryo and maternal body.

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Write the location and function of the sertoli cells in humans. 


Sertoli cells are found in testis. Its function is to provide nourishment to the germ cells.

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Write the function of each one of the following:

(a) (Oviducal) Fimbriae

(b) Coleoptile

(c) Oxytocin

(a) Fimbriae are the finger-like processes present at the end of the fallopian tubes

(b) Coleoptile is a conical sheath present in the monocot seeds; its function is to protect the developing plumule.

(c) Oxytocin is a hormone secreted by the posterior pituitary and it stimulates the contraction of uterine muscles during child birth (parturition).

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Describe the process of Parturition in humans.


Parturition is the process of childbirth or the delivery of the foetus because of vigorous contraction of uterus at the end of the pregnancy which is after the 9 month gestation period. It is induced by a complex neuroendocrine mechanism. Fully developed foetus gives the signal which induces mild uterine contraction called foetal ejection reflex. This triggers results in release of oxytocin from maternal pituitary. The oxytocin results in stronger contractions of the uterine walls and the secretion of more and more oxytocin. The effect of oxytocin and uterine wall contraction leads to stronger contraction which leads to the expulsion of the foetus through the birth canal or parturition.

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Draw a diagram of the microscopic structure of human sperm. Label the following parts in it and write their functions.

(a) Acrosome

(b) Nucleus

(c) Middle piece


Microscopic structure of human sperm



Function of Acrosome -

It contains enzymes that help the sperm to enter and to fertilise the ovum.

Function of Nucleus -

It stores the genetic information. It carries 23 chromosomes, out of which one is sex chromosome (either X or Y). Thus, it is responsible for determining the sex of the individual.

Function of Middle piece -

The middle piece contains several mitochondria, which produce energy for the movement of the tail and motility of the sperm.

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