Journey of sperms from the vagina to the ampulla of uterine tube is facilitated by –
A. Hyaluronidase B. Calcium concentration of endometrial fluid C. Oxytocin D. Glycoproteins of Zona pellucida
Ans. C. Oxytocin
The prostaglandins cause powerful contraction of uterine muscle, which is substantiated by oxytocin released by neurohypophysis. Uterine contractions create a negative pressure in the uterine cavity. Consequently the sperms are sucked in from the vagina into the uterine cavity.
During fertilization which part of sperm doesn’t enter the oocyte
A. Head B. Axial sheath C. Tail D. Nuclear material
Ans. B. Axial sheath
The plasma membranes of sperm and oocytes come in contact and break down at the site of fusion. The head and tail of sperm enter the cytoplasm of the oocyte but its plasma membrane and mitochondrial sheath are left behind on the oocyte surface.
Which of the following is not a result of fertilization
A. Formation of secondary oocyte B. Extrusion of the second polar body into the perivitelline space. C. Restoration of diploid number of chromosomes D. Formation of male and female pronucleus
Ans. A. Formation of secondary oocyte
The first meiotic division of primary oocyte is unequal forming secondary oocyte and polar body. It happens before ovulation. Only the second meiotic division of the female gamete is completed after fertilization.
Which is not a feature of cleavage stage of embryo
A. Repeated mitotic divisions B. Cells become smaller with each successive cleavage division. C. Zona pellucida thinning D. Rapid increase in number of cells
Ans. C. Zona pellucida thinning
During cleavage the zygote is surrounded by a rather thick zona pellucida. It prevents inappropriate implantation of embryos while passing through the fallopian tube. The most important function of zona pellucida is to prevent implantation of the blastocyst at sitesother than the normal, thus preventing ectopic pregnancy.
Which is not true about germ layers
A. The nervous system and sense organs are formed by the ectoderm B. Adenohypophysis of the pituitary gland is from mesoderm C. Pancreas (acinar and islet cells) are from endoderm D. Auditory tube and middle ear cavity forms from endoderm
Ans. B. Adenohypophysis of the pituitary gland is from mesoderm
Adenohypophysis of the pituitary gland and adrenal medulla develop from ectoderm whereas Pancreas (acinar and islet cells), Thyroid (follicular cells), Parathyroid (principle and oxyphil cells) develop from endoderm. Adrenal cortex and Testes and ovaries are derived from mesoderm.
Which is not a part of gastrulation process
A. Trophoblast differentiates into two layers: cytotrophoblast and syncytiotrophoblast B. Embryoblast differentiates into two layers: ectoderm and endoderm C. Extraembryonic mesoderm splits into two layers: somatopleure and splanchnopleure D. Formation of embryoblast and trophoblast
Ans. D. Formation of embryoblast and trophoblast
Embryoblast is otherwise known as inner cell mass which is formed before implantation. At the same time those cells that are present at the periphery of the morula are called outer cell mass or trophoblast.
Hydatidiform mole is an abnormal or blighted blastocyst after death of the embryo.
This is followed by an excessive (hyperplasia) proliferation of trophoblast to form a vesicular or polycystic mass called hydatidiform mole.
Actually when the embryo dies, the developing villi could not develop further (e.g., tertiary villi) due to lack of blood supply. They start degenerating and cystic swellings develop in degenerating villi.
Moles secrete higher levels of human chorionic gonadotrophins (HCG).