Which extraembryonic membrane in humans prevents desiccation of the embryo inside the uterus?
Chorion
Allantois
Yolk sac
Amnion
D.
Amnion
Amnion is an extraembryonic membrane that surrounds embryo in reptiles, birds and mammals. It provides a kind of private aquarium to the embryo and protects it from mechanical shock and desiccation.
Chorion (serosa) is the outermost extra - embryonic membrane in reptiles, birds and mammals. It surrounds the whole embryonic system of the embryo.
Yolk sac contains yolk in reptiles and birds. In mammals, the yolk sac is also known as an umbilical vesicle. It is connected to enter one of the embryo by a slender yolk stalk. Allantois functions as an embryonic urinary bladder or as a respiratory extension of hindgut in reptiles and birds. In mammals, it is modified to carry blood vessels to and from the placenta.
In human, during fertilization, a sperm firstly comes in contact with which layer of the ovum
Zona pellucida
Vitelline membrane
Jelly coat
Zona radiata
The number of chromosomes in a primary spermatocyte is
Same as in spermatid
Same as in spermatogonium
Help of that in spermatogonium
Same as in secondary spermatocyte
Due to alcohol abuse, brain-related disease Korsakkoff’s syndrome occurs. Which nutrient is responsible for this syndrome?
Vitamin-B12
Fat
Protein
Vitamin-B1
How many sperm cells are present in an average (3 mL) ejaculation?
200 million
300 million
400 million
500 million
