Explore topic-wise InterviewSolutions in .

The embryonic stage that gets implanted in the uterine wall of human female Blastocyst.

(d) Blastocyst

Trophoblast is the outer layer of blastocyst which helps in the attachment of blastocyst to the endometrium of the uterus.

Blastocyst/blastula.

Blastula ...

(d) Insemination, Fertilization, Implantation, Placentation and Parturition.

After implantation, finger-like projections appear on the trophoblast called chorionic villi which surround the uterine tissue and maternal blood. The chorionic villi and uterine tissue become interdigitated with each other and jointly form a structural and functional unit between developing embryo and maternal body called placenta. The placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from embryo. The inner cell mass differentiates into the three germ layers—outer ectoderm, middle mesoderm and inner endoderm. These primary germ layers give rise to all the tissues and organs, starting as the primordia.

(i) Signals originate from the fully developed foetus and placenta.

(ii) Induce mild uterine contractions (foetal ejection reflex).

(iii) Triggers release of oxytocin (from maternal pituitary).

(iv) Oxytocin acts on uterine muscles and causes stronger uterine contractions.

(v) Stimulatory reflex between the uterine contraction and oxytocin secretion continues resulting in stronger and stronger contraction.

(vi) Expel the baby from the uterus.

Detailed Answer:

• Parturition is the process of giving birth to a baby.
• The physical activities like uterine and abdominal contractions, dilation of cervix for passage of baby are involved in this process which are collectively called as labour and the discomfort or agony caused by it in known as labour pains.
• Parturition is controlled by a complex neuroendocrine mechanism 
• Signals originate from fully formed foetus and placenta which induce mild uterine contractions called foetal ejection reflex. This causes the release of oxytocin from maternal pituitary.  
• Oxytocin causes stronger uterine muscle contraction which in turn stimulate further secretion of Oxytocin. This Process is continued leading ultimately to expulsion of baby out of the uterus through the birth canal. 
• After parturition, the umbilical cord is tied and cut off the placenta separated from uterus and is expelled out due to series of strong uterine contractions.

(a) From the fully developed foetus / placenta / foetal ejection reflex.

(b) It contains antibodies (IgA), provides immunity to the child.

Detailed Answer: 

(a) The signals for parturition in humans originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex. This causes the release of oxytocin from maternal pituitary.

(b) The milk that comes out of the mammary glands during initinal period of lactation and after parturition is called colostrum. It contains several antibodies and nutrients and is low in fat contents. It provides immunity to the child. Therefore, it is important to feed the new born babies on colostrum. Breast feeding also recommended by doctors for bringing up a healthy baby.

After implantation interdigitation of maternal and foetal tissues results in formation of structural and functional unit between embryo and maternal body called placenta. 

It facilitates supply of oxygen and nutrients to the embryo, removal of carbon dioxide and excretory material and also acts as an endocrine tissue and produces hormones like HCG, hPL, estrogen, progesterone and relaxin.

Oxytocin acts on uterine muscle, and cause stronger uterine contraction, leading to expulsion of the foetus & baby out of uterus.

The signals from fully formed foetus and the placenta which induce mild uterine contraction/foetal ejection reflex triggers release of oxytocin.

After implantation interdigitation of maternal and foetal tissues results in formation of structural and functional unit between embryo and maternal body called placenta. 

It facilitates supply of oxygen and nutrients to the embryo, removal of carbon dioxide and excretory material. Also acts as endocrine tissue and produces hormones like hCG, hPL, estrogen, progesterone, relaxin.

Estrogen influences the uterus in the follicular phase. The endometrin is regenerated through protection. Progesterone influences the uterus in the luteal phase, the endometrin becomes further thickened and vascular for implantation

Menstrual phase – flow follicular phase – follicular growth regeneration of endometrium Ovulation , secretary phase – corpus luteum LH ,FSH role.

This is because of a neural signal given by the maternal endometrium to its hypothalamus in presence of a zygote to sustain the gonadotropin (LH) secretion, so as to maintain the corpus luteum as long as the embryo remains there. In the absence of a zygote, therefore, the corpus luteum degenerates.

(a) Fertilization :

• Sperm comes in contact and enters the secondary oocyte.
• Activates/induces secondary oocyte to complete meiosis II leads to formation of ovum/ootid.
•  The haploid nucleus of sperm and that of ovum fuse to form a diploid zygote completing the process of fertilization.

Implantation:

• Trophoblast layer of blastocyst attaches to the endometrium (of the uterus).
• The uterine cells divide rapidly and cover the blastocyst.
• The blastocyst becomes embedded in the endometrium and the implantation is completed.
• (b)  hCG (human chorionic gonadotropin)
• hPL (human placental lactogen)
• estrogen
• progestogens

Detailed answer : 

(b) The placenta also acts as an endocrine gland because it produces many hormone-like human Chorionic- Gonadotropin (hCG), human placental Lactogen (hPL), Oestrogen and progesteron and estrogen etc. In the later phase of pregnancy a hormone called as relaxin is also secreled by the ovary, hCG, hPL and relaxin hormone are produced in women only during pregnancy.

(c) endometrium

The secretion of the acrosome help the sperm enter into the cytoplasm of ovum through zona pellucida and the piasira membrane, this induces the completion of second meiotic division of the secondarv oocyte, forming second polar body and a haploid ovum, soon the haploid nucleus of the sperm and that of the ovum fuse together to form a diploid zygote.

In the absence of fertilisation, corpus luteum degenerates and this causes disintegration of the endometrium of ovary, leading to menstruation.

1. Spermiogenesis : Transformation of spermatids into mature sperm. 

2. Spermiation : Release of mature sperm into the lumen of seminiferous tubule.

The secretion of the acrosome help the sperm enter into the cytoplasm of ovum through zona pellucida and the plasma membrane. This induce the completion of second meiotic division of the secondary oocyte, forming second polar body and a haploid ovum. Soon the haploid nucleus of the sperm and that of the ovum fuse together to form a diploid zygote.

The chromosome number of secondary oocyte is 22 + X

During fertilisation a sperm head comes in contact with zona pellucida layer of ovum and induces changes in the membrane that block the entry of additional sperms.

Correct option is d. Capacitation

During fertilization, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes in the membrane that block the entry of additional sperms.

Prophase I ..

1.  The primary follicle .grows and becomes fully mature graafian follicles.

2.  Secretion of estrogen hormone.

3.  Endometrium of uterus regenerates through proliferation.

The mammary glands of the female undergo differentiation during pregnancy and starts producing milk towards the end of pregnancy by the process called lactation. The milk produced during the initial few days of lactation is called colostrum which contains several antibodies absolutely essential to develop resistance for the new bom babies. Breast-feeding during the initial period of infant growth is recommended by doctors for bringing up a healthy baby.

For fertilization to take place the sperm and ovum must reach the ampullary-isthmic junction simultaneously. If sperms and ovum do not reach the site of fertilization (ampullary-isthmic junction) no fertilization (fusion of sperm and ovum) occurs inspite of the fact that copulation has taken place.

Morula is a mulberry like solid mass of 8-16 cells called blastomeres, formed by cleavage of zygote, while the blastocyst is a hollow sphere of 64 cells formed by the rearrangement of blastornr.res of morula. It has a cavity called blastocoel and an inner cell mass within. It also has an outer envelope of cells called the trophoblast.

(A)

(B) The two accessory glands are: 

(i) Prostate gland: It surrounds the urethra and produces a milky secretion which forms a considerable part of semen. This secretion contains citric acid, lipids and enzymes. The secretion nourishes and activates the spermatozoa to swim. 

(ii) Seminal vesicles: These secrete mucous and a watery alkaline fluid that contains fructose which provides energy to the sperms.

(i)  sexually

(ii) viviparous

(iii) internal

(iv) haploid

(v) diploid

(vi) ovulation

(i) fertilization

(ii) ampullary isthmus in fallopian tube

(iii) Blastocyst

(iv) umbilical cord.

Highly coiled in testicular lobule,male germ cells sertoli cells, sperm formation provide nutrition.

At puberty /embryonic development,four sperms /one egg,equal division /unequal division.

(a) sprmatogonia

The wall of the uterus has three layers of tissues. The outermost thin membranous serous layer called the perimetrium, the middle thick muscular layer called myometrium and the inner glandular layer called endometrium. The endometrium undergoes cyclic changes during the menstrual cycle while myometrium exhibits strong contractions during parturition.

Perimetrium, myometrium and endometrium.

(a) Luteinizing hormone (LH) stimulate leydig cell to secrete androgens which in turn stimulate spermatogenesis.

(b) There are numerous mitochondria in the middle piece of sperms which produce energy and required for the movement of sperms.

It is present at the tip or head of the sperm. It helps to penetrate through the zona pellucida in human ovum.