In humans, at the end of the first meiotic division, the male germ cells differentiate into the
Primary spermatocytes
Secondary spermatocytes
spermatids
spermatids
B.
Secondary spermatocytes
At sexual maturity, the germ cells in human male divide several times by mitosis to produce a large number of spermatogonia. In the growth phase, each spermatogonium actively grows to a larger primary spermatocyte by obtaining nourishment from the nursing cells. In maturation phase, each primary spermatocyte undergoes two successive division called maturation divisions. The primary spermatocyte undergoes first maturation division (meiotic) to producing tow haploid daughter cells called secondary spermatocytes undergo second maturation division to form four haploid spermatids. The transformation of spermatids into spermatozoa is called spermiogenesis or spermateliosis.
The correct sequence of spermatogenetic stages leading to the formation of sperms in mature human testis is
spermatocyte-spermatoogonia-spermatid-sperms
spermatogonia-spermatocyte-spermatid
spermatid-spermatocyte-spermatogonia-sperms,
spermatid-spermatocyte-spermatogonia-sperms,
B.
spermatogonia-spermatocyte-spermatid
In spermatogenesis, during growth phase some spermatogonia either due to growth or due to food storage become 2 or 3 times larger to their original size and are known as primary spermatocytes, which undergo meiosis- I and as result2 haploid secondary spermatocytes are formed.Further, meiosis-II takes place that results in the formation of 4- spermatids. Then, these round, non-motile and haploid spermatids are transformed into thread-like motile, haploid sperms (four).
In human adult females, oxytocin
is secreted by the anterior pituitary
stimulates the growth of mammary glands
stimulates pituitary to secrete vasopressin
stimulates pituitary to secrete vasopressin
D.
stimulates pituitary to secrete vasopressin
Oxytocin hormone is secreted from the posterior lobe of pituitary gland. It promotes contraction of the uterine muscle and myoepithelial cells of lactating breast, squeezing milk into the large ducts behind the nipple. Because of its role oxytocin is called birth hormone.
The anterior lobe of pituitary gland secretes a somatotropic hormone, thyroid stimulating hormone, adrenocorticotropic hormone and gonadotropic hormones.
The prolactin hormone or luteotropic hormone is secreted from the anterior lobe of pituitary gland. It activates the growth of breasts during pregnant and secretion of mammary glands after childbirth.
Which extraembryonic membrane in humans prevents desiccation of the embryo inside the uterus?
Chorion
Allantois
Yolk sac
Yolk sac
D.
Yolk sac
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 extraembryonic 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 yolk, the sac is also known as a umnillical vesicle. It is connected to enter on of the embryo by a slender yolk stalk.
Allantois functions as an embryonic urinary bladder or as a respiratory extension of a handgun in reptiles and birds. In mammals, it is modified to carry blood vessel to and from the placenta.
Seminal plasma in human is rich in
fructose, calcium and certain enzymes
fructose and calcium but has no enzymes
glucose and certain enzymes but has no calcium
glucose and certain enzymes but has no calcium
A.
fructose, calcium and certain enzymes
Seminal plasma is composed of the fluid and sperms from the vas deferens (about 10% of the total), fluid from the seminal vesicles (almost 60 percent), fluid from the prostate. gland (about 30 percent) and a few mucous glands, especially the bulbourethral glands. It contains calcium citrate ion, phosphate ion, a clotting enzyme, profibrinolysin, fructose, citrate, inositol, prostaglandins several proteins, etc,