Class 12th Biology Chapter 2 - Human Reproduction

NCERT Solutions for Class 12 Biology Chapter 2 : This chapter is about Human Reproduction. We are going to cover the topics like Flower structure, Development of gametophytes, seeds, Pollination, Double Fertilization,etc. We have prepared this article very carefully and tried to include all those important topics and notes from the chapter which you can use in your preparation for 12th exam or any other upcoming competitive exams.

 

In this chapter we have covered all the topics related to Human Reproduction  which are listed below:-

 

Human Reproduction

Types of reproduction

Morphology

Gametogenesis

Spermatogenesis

Puberty

Menstrual cycle

Oestrus cycle

Menarche

Menopause

Embryonic development

Parturition

Placenta 

 

                                     HUMAN REPRODUCTION

 

Reproduction 

The process by which the formation of new individuals of same kind with slight genetic , structural and physiological variation  is known as reproduction.

Life span

Life span is the time period of an organism from it’s birth to natural death.

Types of reproduction in organism

1.Asexual reproduction

2.Sexual reproduction

1. Asexual reproduction

 When a single organisms is capable of producing its own kind and are genetically identical then this process is known by asexual reproduction.

It takes place through budding , fragmentation, spores , etc

2 . Sexual reproduction

The development  of the new individual which takes place by the fusion of two sex cells ,one male gamete and the other one which is female gamete .

The Zygote is formed by the fusion of sperm ( male)

Ovum (female) gametes and when they meet they form embryo.

Human Reproductive system

There are two sex one is male and the other is female .The male one is testes and female is ovaries.They also have accessory structure & reproductive ducts.

Male reproductive system

The male reproductive system has external genitalia , penis which contains urethra, accessory gland seminal vesicles, prostate & bulbourethral gland, duct system vasa efferentia, epididymis, ductus deferens and pair of one sex glands which is called as testis.

The testis is responsible for the production of spermatozoa (male sex cells) which is done by many ducts and is ejected by urethra.

The fluid vesicle nourish the spermatozoa during passing the passage which is produced by the secretion of glands.It is whitish in colour viscous fluid which is known as semen or seminal fluid.

Ejaculaton

When the semen is expulsed from the urethra then this process is known as ejaculation.

Spermatozoon is about 60μm long , flagelleted motile cell.

The shape is described as a long narrow tail and flat oval head.

In a pair of glands the sperm is produced called testes.

Location

The male testes are suspended in a pouch known as scrotum.

In the abdominal cavity they develops near the kidney.

At the time of birth testes migrates to scrotum.

Structure

There is a dense fibrous membrane in the testes at the outmost layer called tunica albuginea.

The testis are divided into lobules known as testicular lobules.

The number of tiny and highly convoluted tubules is contained in lobule Called seminiferous tubules.

Interestial cells and leydig cells are present between the seminiferous tubules.

Epididymis

The uncoiled long above 6 meters tube which is resting upon and on the testis side.

Ampula

The ductus deferens have the terminal dilated part which is called ampula.

Female reproductive system

The Female reproductive system has pair of mammary glands and are accessory genital glands, vagina, uterus ,a pair of oviduct (fallopian tube) , a pair of ovary and duct system.

The secretion of female sex hormone , estrogens & progesterone is done by ovary and ovary also produces ova.

The ovum is carried by ovarian follicle by several layers of granularr cells or follicular granulosa. The primordial follicle is constituted by primary ovum and follicular granulosa.The graffian follicle is the follicle which bulges into the surface of ovary.

Urethra

It is 18 to 20 cm long which passes from the prostate gland from the urinary bladder and it extends through the penis, the urethral meatus is the external opening.

Accessory glands

It includes three glands two seminal vesicles, two bulbourethral gland and prostate.

Prostate gland

It lies below the neck of urinary bladder.

Cowper’s gland is also known as bulbourethral gland.

Uterus is also known as womb.

Cervix

In the uterus the lower part is very narrow which is known as cervix.

Two disorder associated with sterility are

1.Oligospermia

Spermatozoal count is low in this.

2.Azoospermic

Spermatozoal count is totally absent in semen.

Shedding of ovum is known as ovulation and it starts from 14 days before onset of nest menstrual cycle.The primary oocyte is divided and it becomes secondary oocyte after shedding.

Corpus luteum

The graffian follicle remains after the extrusion of ovum is known as Corpus luteum.

The rich yellow pigment in cytoplasm of Corpus luteum is known as lutein.

When the Corpus luteum is  degenerated then it is converted into mass of fibrous tissue called Corpus albicans.

Antrum

A fluid filled cavity is known as antrum.

The uterus has three wall

1. External thin membrane perimetrium.

2.middle thick layer myometrium.

3.inner glandular layer endometrium.

Hymen

A thin mucous membrane which also covers the opening of vagina . sometimes it breaks by the initial act of sexual intercourse or by physical activity.It is moistened by bartholin’s gland.

In females the external genital organs is known as vulva.

The pad of fatty tissue is round in shape which is known as mons pubis.

 

Areola

The dark pigmentated circular area in breast over the centre of elevation is known as areola.

Nipple

A projection which is over the centre part of the areola is known as nipple.

Alveoli

The glandular tissue is divided 15 to 20 mammary glands which contains the milk producing glands is known as alveoli.

The oestrus cycle is divided into four phases.

Proestrus The swelling and increasing of vascularity of vulva occur.The organs of females is brought in a favourable condition for the reception of spermatozoa and fertilization of ovum.

Estrus-It is the period when the female receives the male.

Metestrus -In this phase the implantation of Fertilized ovum in the uterus is anticipatoty.

Anestrus-In monoestrus animals the resting period lasts untill the next mating season while in polyestrous animals it lasts only to next cycle.

 

Ovarian cycle

Series of changes which begins with the formation of ovarian follicle and end with the degeneration of Corpus luteum is known as ovarian cycle.

Gametogenesis

It is the formation of gamete in the sexualy reproducing animals.

Spermatogenesis

It is the formation of spermatozoa (male gametes) in the testis.

Oogenesis

It is the development of ova ( female gamete) in the ovaries.

Puberty

When a boy and a girl is capable of reproducing and their reproductive system becomes mature.

Menstrual cycle

The changes in woman and female primates from puberty to menopause which occurs after every 28 days throughout the reproduction life is known as menstrual cycle.

 Menstrual period or menstruation

From the uterus the monthly flowing of blood is known as menstrual cycle.

Gonadotropin-releasing hormone (GnRH), Follicle stimulating hormone (FSH), Lutenizing hormone (LH) , Estrogens & progesterone are the five hormones which regulates woman’s menstrual cycle.

Oestrus Cycle

In non primates, the phase when only at certain periods of year the female receives the male is known as breeding season.

The females do not have any sexual activity unless the sexual activities occurs cyclically. Is called oestrus cycle.

Menarche

In the life of a girl the appearing of first menstrual flow is called menarche. It occurs between 11&13 years.

Menopause

In the life of a woman the permanent stopage of menstrual cycle is known as menopause.It occurs between 45 and sometimes over 50 years.

Embryonic development

In embryonic development the structural changes of zygote leads to formation in form of adult is called embryonic development.

Fertilization in mammals

As a example  , in female (human) the process in which the Fertilization takes place in the fallopian tube.

In aquatic organisms syngamy occurs outside the body of organisms and this is known as external Fertilization.

In plants and animals the gamete fusion takes place inside the body it is known as internal fertilization.

 

The process is divided into five heads:-

1.Maturation and capacitation of spermatozoa.

2.Structure of ovum

3. Coitus

4.Passage of spermatozoa in female genital tract.

5.Ovum sperm interaction in fallopian tube.

 

Animal pole

When polar body is extrudes from the region of ovum and it receives the sperm is called animal pole.

Vegetal pole

The animal pole which is opposite of the pole of ovum is known as vegetal pole.

Corona radiata

It is a layer which is surrounds  the zona pellucida.

Zona pellucida

It is 100µm in diameter and it is surrounded by a non cellular layer.

Telolecithal

At one pole small amount of cytoplasm is concentrated and dispersed volume of yolk of Ovum.

 Spermiogenesis

The circular spermatid is transformed to spermatozoon.

Sexual cycle

The physiological and structural changes which are associated with sex. Like Menstrual and oestrus cycle.

Primitive streak

In morphogenetic movements and in proliferation of mesoderm & notochord there is a opaque ,dense band of ectoderm in bilaminar blastoderm  which is associated with it, which indicates first trace of vertebrate embryo.

Placenta

The uterine wall of mammal and the foetal membrane there is a established intimate connection between them.

It is also serves the nourshiment to the baby through mother’s blood and the waste products disposal through baby blood to mother’s.

Parturition

At the end of gestation from the mother’s uterus the expelling of full term foetus.

Monestrous

In one year there is only one estrous cycle.

Meroblastic

Because of large amount of yolk the pertaing to an ovum undergoes through cleavage which is incomplete.

Menorrhea

It is defined as the flow of the blood or the menses.

Isolecithal

It is defined as the distributed yolk which is present in the eggs is in small amount.

Insemination

In the female genital tract the depositing of male sperm in it.

Implantation

In the uterine wall the blastocyst is attached with it.

Hensen’s node

In vertebrate gastrula the thickening is formed at the anterior end of primitive streak by a group of cells.

Gestation period

From the Fertilization period to birth period in mammals is called gestation period.

Germ layer

In early aminal embryo there is one cell layer which is primitive and by this , the body of embryo is made.

Gastrulation

During development the endoderm is formed this process is known as gastrulation.

Epiboly

In the upper hemisphere of blastula the growing of one part and in the lower hemisphere in embryogenesis.

Endometrium

In uterus the lining of mucous membrane is called endometrium.

Colostrum

Following parturition during the first day, the first milk which is secreted by the mammary glands is known as colostrum.

Clitoris

In the anterior portion of vulva in females there is a homolog of penis is present.

Circumcision

In this procedure the prepuce or the part is removed through surgical method.

Chorion

The extraembryonic membrane of amniotes from the outermost is enclosing the other membranes and it’s embryo.

Castration

The removal of testis from male through surgical method.

Amnion

 Around the embryo of a  birds, reptiles and mammals there is a thin extraembryonic membrane which forms a closed sac.

Amenorrhea

At reproductive age the menstrual period is absence in woman’s.

Allantois

The amnion and chorion of mammalian embryos and birds there is a fluid filled, sac like extraembryonic membrane lying between it.

Alecithal

A egg which do not have yolk inside it or the placental mammals eggs.

Lactation

The secretion of milk from the mammary glands is known as laction.

The hormone which promotes laction is the Prolactin.

Umbilical cord

The rope like cord which is attached with the baby is called umbilical cord.

There is two placenta –

One which is shared by mother is maternal placenta.

The one which is contributed by chorionic villi is called foetal placenta.

 

In this article, we have tried to give you all the important information related to 12th Biology Chapter 2, you can also join our WhatsApp channel for regular updates where we are the first to give information about new articles or mock tests. Live. Click here to join the WhatsApp channel.