Students should refer to Reproductive System ICSE Class 10 Biology notes provided below designed based on the latest syllabus and examination pattern issued by ICSE. These revision notes are really useful and will help you to learn all the important and difficult topics. These notes will also be very useful if you use them to revise just before your Biology Exams. Refer to more ICSE Class 10 Biology Notes for better preparation.
ICSE Class 10 Biology Reproductive System Revision Notes
Students can refer to the quick revision notes prepared for Chapter Reproductive System in Class 10 ICSE. These notes will be really helpful for the students giving the Biology exam in ICSE Class 10. Our teachers have prepared these concept notes based on the latest ICSE syllabus and ICSE books issued for the current academic year. Please refer to Chapter wise notes for ICSE Class 10 Biology provided on our website.
Reproductive System ICSE Class 10 Biology
TOPIC-1
Reproductive Organs and Accessory Glands
Quick Review
➢ Reproduction is a process by which each of the living Organism multiplies to form new individuals of its own Kind. Animals and plants reproduce enormously to continue their race.
➢ Animals reproduce in three ways –
(i) Asexually
(ii) Sexually
(iii) Parthenogenesis
➢ Asexual reproduction involves no formation and fusion of gametes. It occurs by method like budding, fission, fragmentation etc.
➢ In sexual reproduction both male and female gametes are produced. They are fused to form a zygote. It develop into a complete individual. It may be isogamous (isogamy) and anisogamous (anisogamy).
➢ In isogamy the fusing male and female gametes are similar.
➢ In anisogamy the fusing male and female gametes are dissimilar. Male gamete is motile and small, called microgamete. Female gamete is large, non-motile and laden with food is called macrogamete.
➢ Parthenogenesis involves development of an unfertilized ovum into a fully fledged haploid organism.
➢ Reproduction in human beings occurs with the help of organs of reproductive system.
These organs are divided into following two main parts –
(i) Primary Reproductive Organs – These include the gonads of both male (testes) and female (ovaries) which are responsible for producing gametes i.e. sperms (in males) and eggs (in females). The process is know as gametogenesis.
(ii) Accessory Reproductive Organs – These include all the structures which help in the process of reproduction. These parts have distinct roles from fertilization to growth, development and birth of the baby.
➢ The reproductive organs in males comprises of following reproductive parts –Testes, Epididymis, Vasa deferentia, Ejaculatory duct, Urethra and Penis.
➢ Testes are a pair of pinkish, oval bodies present in sacs called scrotum. Testes are held in position by spermatic cord. The cavity of scrotal sac is connected abdominal cavity through inguinal canal. The scrotal sac acts as thermoregulator, maintaining testes at a temperature 2°C lower than the normal body temperature.
➢ There are about 250 testicular lobules present in each testis. Each lobule contains long and very much coiled seminiferous tubules which are lined with germinal epithelium. The germinal epithelium produces spermatids which get food from sertoli cells and develop into sperms.
➢ Leydig’s cells or Interstitial cells are spherical cells arranged in groups inside testes. These acts as endocrine gland. These cells secrete testosterone hormone which is concerned with the formation of secondary sexual characters in males.
➢ Epididymis is a very long and highly convoluted tube which lies along the side of testes. Here the sperm undergoes maturation and acquire fertilizing capacity and increased motility. In the lower tail of the epididymis the sperms are stored for a short period of time before entering the vas deferens.
➢ Vasa deferentia is long narrow muscular structure which start from epididymis, joins with ejaculatory duct and urethra.
➢ Ejaculatory ducts are two in number. Each have a length of 2 cm and they open into urethra. They pass through prostate gland.
➢ Urethra arises from urinary bladder. It receives prostate ducts and ejaculatory ducts. It continues downward and receives duct from cowper’s gland. The urethra open out at the tip of penis.
➢ Penis is cylindrical copulatory organ. It is supported by erectile tissue. The tip is called glans penis. It is highly sensitive.
➢ Associated with male reproductive organs, the following glands are present – Seminal vesicles, Prostate gland, Cowper’s glands.
➢ Seminal vesicles are a pair of long highly muscular pouch like organs placed between the bladder and rectum. They secrete a viscous fluid which is alkaline in nature and contains fructose for energy.
➢ Prostate gland are present in the first part of urethra. It secrete a thin milky alkaline fluid. Its secretion activate the spermatozoa to swim.
➢ Cowper’s gland is a pair of small pea shaped gland which lie beneath the urinary bladder. It secretes alkaline mucus into the urethra.
➢ Female reproductive system consists of a pair of ovaries, oviduct, uterus and vagina.
➢ Ovaries are primary sex organs located in pelvic cavity. Ovary is lined by germinal epithelium. Ovary contain fibrous, vascular connective tissue called stroma. Stroma contain groups of germinal epithelial cells called follicles. One cell from each follicle develop into ovum and the developing ovum then enclosed by a striated membrane called zona pellucida or zona radiate. A mature follicle is known as graafian follicle.
➢ Mature follicle rupture and soon swept into nearest fallopian tube. The process of liberation of ovum from ovary is known as ovulation.
➢ The empty follicle is filled with follicular cells and blood clot. These structures soon formed into yellowish glandular material, called corpus luteum.
➢ Corpus luteum secretes progesterone, which is responsible for the preparation of uterus for the development of zygote ( if fertilization takes place ).
➢ There are a pair of oviduct (Fallopian tube) which is about 12 cm in length. It is present above urinary Bladder. The secretory cells of oviduct produces a viscous liquid which protect and provide nourishment to ovum.
➢ Uterus is a hollow pear- shaped organ located in the pelvic cavity between the urinary bladder and rectum. It is also known as womb because it is the place where development of embryo takes place.
➢ Uterus is about 10 cm long. It provides a passage for menstrual flow, serve as receptacle for sperms and it is a part of birth canal.
➢ Menstrual cycle is a series of changes that occurs in the reproductive tract of human females with a periodicity of 28 days. It is characterized by menses or loss of blood for a few days. Menstrual cycle consists of the following phases –
Menstrual phase.
Post-menstrual or Follicular phase.
Fertility phase or Ovulation.
Pre-Menstruation, Luteal or Secretory phase.
➢ Menstrual phase is the phase of menstrual flow or menses which continues for 3-5 days. It involve discharge of blood and cast of endometrial lining due to reduced level of both estrogen and progesterone hormones.
➢ Follicular phase is completes in 14 days. The anterior lobe of the pituitary gland secretes FSH which stimulates follicular cells of graafian follicle to secrete estrogen. Estrogens enhances proliferation of cells of endometrium of uterus. Oestrogen hormone goes to anterior lobe of pituitary gland inhibits the secretion of FSH and stimulates luteinizing hormone (LH).
➢ In ovulatory phase, rupture of graafian follicle occurs as a result egg get released to travel the oviduct. It occurs on about 13-14th day of the menstrual cycle.
➢ Luteal phase continues for around 15-28 days. During this phase uterus lining gets thickened and the remaining part of the graafian follicle transforms into the corpus luteum an endocrine gland / tissue which secrete progesterone hormone.
➢ If there is no fertilization during this period, the uterus lining again start shedding on the 28th day.
➢ If the egg gets fertilized it gets fixed in the uterus and there will be no menstrual flow because the level of progesterone increases (preventing the growth and maturation of another follicle).
TOPIC-2
Fertilization and Development of Embryo
Quick Review
➢ Fertilization is the penetration of a mature ovum by the spermatozoon or the fusion of the respective female and male gamete in order to produce a zygote.
➢ Fertilization takes place in the oviduct. Male discharge about 300 million sperm into female vagina. The sperm travel to the uterus. Contraction of the uterus and oviduct assist in sperm movement.
➢ Secondary oocyte can be fertilized within 24 hours after its release from ovary. After acrosomal reaction the sperm plasma membrane fuses with plasma membrane of secondary oocyte.
➢ Sperm entry stimulate secondary oocyte. The head of sperm separates from its body. The male and female pronucleus move towards each other and fusion takes place. The fertilized ovum is called zygote.
➢ A mature sperm is a microscopic, tadpole-shaped structure of about 2.5-3.5 μm in diameter and 60 μm long. The sperm has following four parts – head, neck, middle part and tail.
➢ Head is of large size and has a anterior end, acrosome. The acrosome is formed from golgi complex. When the sperm comes in contact with the egg then acrosome secretes enzyme which dissolves egg membranes and sperm enters into egg. The head contains a large nucleus (contained DNA) and little cytoplasm.
➢ Neck is of small size. It contains two centrioles. One is proximal and the second distal. The distal centriole produces axial filament.
➢ Middle piece lies below neck. It has in centre an axial filament. Surrounding it there are large number of mitochondria arranged spirally. These mitochondria provides energy to sperm into the female reproductive tract.
➢ Tail is a long, slender structure which acts as the locomotory organ of the sperm.
➢ Ovum is the female non-motile gamete having the genetic material in the nucleus. As soon as one sperm enter the ovum (egg), the entry of other sperm is prevented by some chemical barriers.
➢ Implantation is the phenomenon of attachment of developing embryo within the uterus. It leads the state of pregnancy. The uterus continues to develop to take care of the developing embryo.
➢ Placenta is a connection between the foetus and uterine wall of mother to exchange the material. The outer surface of chorion develops a number of finger like projections known as chorionic villi which penetrate tissue to make up placenta.
➢ Amnion is thin, double layered membranous structure enclosing an embryo. The space between the amnion and foetus in the embryo is filled with the amniotic fluid. This fluid helps in protecting embryo from mechanical shock and physical damage.
➢ Gestation is the time period during which the embryo remains in the uterus. The gestation period is of about 9 months or 280 days in human females.
➢ Parturition is the phenomenon of delivery of a baby which occurs due to the vigorous contractions of the uterus at the end of pregnancy. Oxytocin is the hormone which is responsible for these contractions in human female resulting into the child birth.
➢ In human beings only one foetus develops at a time. Sometimes two foetus are formed and these are termed as twins and rarely 3 to 4 are formed.
➢ Non-identical or dizygotic or fraternal twins forms when 2 eggs are released and are fertilized by two sperms, producing two zygotes. Each zygote produces a young one. Each foetus has its separate placenta. Since two different eggs produce two young ones, they will have different physical and mental traits and may or may not be of the same sex.
➢ Identical or monozygotic twins forms from a single zygote during first cleavage divides into two cells which separate off and each behave like a zygote producing a young one. Since the two embryos are produced from one zygote, the two young one resemble each other in physical and mental traits and necessarily of the same sex, both being male or female. The twins share the same placenta.
Know the Terms
➢ Acrosome : A pointed structure at the tip of the sperm nucleus, which helps sperm in entering the ovum and produces lytic enzymes.
➢ Animal pole : Region of the egg from where polar bodies are released.
➢ Binary fission : Asexual reproduction in which parent body divides into two daughter cell.
➢ Breasts : Accessory sex organs of female, consist mammary gland.
➢ Cervix : Lower part of uterus.
➢ Clitoris : a sensitive structure in the female which is homologous to penis.
➢ Cleavage : Cleavage is a unique embryological process which transforms the single fertilized egg cell into a sphere of closely aggregated multitude of cells.
➢ Capacitation :The changes in a mammalian sperm which prepares it to fertilize the ovum is termed as capacitation.
➢ Colostrum : The first milk secreted by the mammary glands on the first day following parturition.
➢ Copulation : The sexual union of two individuals resulting in insemination of male gametes in close proximity to the female gamete.
➢ Corona radiata : Radiating rows of follicle cells surrounding the ovum at the time of ovulation.
➢ Embryonic development : Structural and physiological changes in a zygote (or foetus) till the formation of an adult.
➢ Holoblastic cleavage : Cleavage division that divide egg (zygote) completely.
➢ Implantation : The embedding of blastocyst in the endometrium of uterus.
➢ Gametes : Specialized sex-cells with haploid number of chromosomes. Produced from the gonads. Male gamete is called sperm and female gamete is called ovum.
➢ Gonads : The organs that produce gametes. Testes are male gonads and ovaries are female gonads.
➢ Isogamy : Fusion of two similar gametes.
➢ Menopause : Stoppage of menstrual cycle and ovulation at the age of 40-45 years.
➢ Oogenesis : Formation of ova in the ovaries.
➢ Semen : Fluid that contains the secretions of accessory glands and the sperms.
➢ Spermatogenesis : Formation of sperm in the testes.
➢ Anisogamy : Fusion of two dissimilar gamete.
➢ Castration : Removal of testes in male and ovaries in female.
➢ Endometrium : The inner lining of uterus.
Modes of Reproduction
Do you know what reproduction is?
Reproduction is the process by which an organism produces individuals of its own kind. Reproduction is important as it helps in the perpetuation, or continuation of species.
But how do organisms reproduce? Do they produce an offspring who resembles them or do they produce an offspring who does not resemble them? Why is it that some organisms reproduce on their own, while others need a partner for reproduction? Let us explore.
There are two modes of reproduction in both plants and animals- Sexual and Asexual reproduction.
Sexual reproduction
Sexual reproduction involves the fusion of male and female gametes to produce an offspring. A number of animals, including humans and plants undergo sexual reproduction.
Asexual reproduction
Asexual reproduction does not involve the fusion of male and female gametes. It requires only one parent. As a result, the offsprings produced are exact copies of their parents. This mode of reproduction is very common in plants.
Have you ever seen gardeners propagating roses through stem cuttings? This is an example of asexual reproduction.
Similarly, many other plants can be propagated with the help of their vegetative parts like stems, leaves, buds, etc. Some animals also reproduce asexually. For example, Hydra reproduces through the process of budding.
Some Interesting Facts:
• Do you know that sexual reproduction makes organisms more fit to survive in their environment?
• Do you know that some organisms like Plasmodium, and many plants can reproduce both sexually and asexually?
Male Reproductive System
Human beings reproduce sexually and are viviparous.
In humans, the reproductive phase starts after puberty. It involves:
• Gametogenesis
• Insemination
• Fertilisation
• Implantation
• Gestation
• Parturition
The Male Reproductive System
• It is located in the pelvic region.
• It consists of:
• A pair of testes
• Accessory glands and ducts
• External genitalia
Testes
• Situated within the scrotum, which protects the testes and also helps in maintaining the temperature.
• Each testis is 4 to 5 cm in length, and 2 to 3 cm in width, and has about 250 compartments called testicular lobules.
• Testicular lobules have seminiferous tubules which are the sites of sperm formation.
• Seminiferous tubules are lined by two types of cells:
• Male germ cells − They undergo meiosis to form sperms.
• Sertoli cells − They provide nourishment to the germ cells.
• Region outside the seminiferous tubules is called the interstitial space, which contains Leydig cells (interstitial cells). The Leydig cells produce androgens.
• Apart from producing sperms, testes also produce a hormone called testosterone. This hormone is responsible for the development of male sex organs like penis and testes. It also brings about secondary sex characteristics in boys during puberty
Sperm
A sperm consists of four main regions:
• Head: It contains a nucleus, that carries the genetic material. It also contains a large secretory vesicle called acrosome. It secrets hyaluronidase enzyme, that helps in the entry of sperm into the egg by dissolving the ovum wall.
• Neck: It joins the head and middle part.
• Middle Piece: It contains several mitochondria that provide energy (ATP) to the sperm.
• Tail: It helps in the movement of the sperm.
Accessory Ducts and Glands
• Accessory ducts include:
• Rete testis
• Vasa efferentia
• Epididymis
• Vas deferens
• The seminiferous tubules open into the vasa efferentia through the rete testis.
• The vasa efferentia open into the epididymis, which leads to the vas deferens. The vas deferens opens into the urethra along with a duct from the seminal vesicle called the ejaculatory duct.
• The ejaculatory duct stores the sperms and transports them to the outside.
• The urethra starts from the urinary bladder, extends through the penis and opens via the urethral meatus.
• Accessory glands include:
• A pair of seminal vesicles
• Prostate gland
• A pair of bulbourethral glands
• The secretions of these glands make up the seminal plasma, and provide nutrition and a medium of motility to the sperms.
The Female Reproductive System
It is located in the pelvic region. It includes:
• A pair of ovaries
• A pair of oviducts
• Uterus
• Cervix
• Vagina
• External genitalia
Ovaries
• They are the primary female sex organs. They produce the ovum and other ovarian hormones.
• They are located in the lower abdomen, and are 2 to 4 cm in length.
• They are connected by ligaments to the pelvic walls and to the uterus.
• Each ovary is covered by epithelium, and contains the ovarian stroma.
• The ovarian stroma is made up of:
• Peripheral cortex
• Inner medulla
Oviducts
• They are also called fallopian tubes.
• They are 10 to 12 cm long, and extend from the ovary to the uterus.
• The part of each oviduct lying towards the ovary is funnel shaped, and is called infundibulum. It has finger-like projections called fimbriae.
• The infundibulum leads to the ampulla, and then to the isthmus, which has a narrow lumen opening into the uterus.
• Ovaries producs two hormones – oestrogen amd progesterone. Oestrogen is required in the development of female sex organs.
• It is also required to bring about the secondary sexual characteristics in females during puberty.
• Progesterone on the other hand plays an important role in pregnancy and in the maintanence of pregnancy.
Uterus
• It is also called womb, and is pear shaped.
• It is connected to the pelvic walls by ligaments.
• The uterine wall consists of:
• External perimetrium
• Middle myometrium
• Internal endometrium, which lines the uterine cavity
• The endometrium undergoes changes during the menstrual cycle.
Cervix and Vagina
• The cervix connects the uterus to the vagina.
• The cervix and the vagina constitute the birth canal.
External Genitalia
• Consists of:
• Mons pubis − Fatty tissue covered by skin and pubic hair
• Labia majora − Extends from mons pubis and surrounds the vaginal opening
• Labia minora − Fold of skin beneath the labia majora
• Hymen − Partially covers the vaginal opening
• Clitoris − Lies at the junction of labia minora
Mammary Glands
• Present in all female mammals
• It is paired and is glandular.
• Each breast contains 15 to 20 mammary lobes with alveoli which secrete milk.
• The alveoli open into the mammary tubules, which unite to form a mammary duct.
• Many mammary ducts constitute the mammary ampulla, which is connected to the lactiferous duct.
Menstrual Cycle
• Menstrual cycle is the reproductive cycle in all primates and begins at puberty (menarche).
• In human females, menstruation occurs once in 28 to 29 days. The cycle of events starting from one menstruation till the next one is called the menstrual cycle.
• During the middle of the menstrual cycle, one ovum is released (ovulation).
• The cycle starts with the menstrual flow (3 to 5 days), caused due to the breakdown of the endometrium of the uterus. Blood vessels in liquid state are discharged, but this occurs only when the ovum is not fertilised.
• It is followed by the follicular phase. In this phase, the primary follicles mature into the Graffian follicles. This causes the regeneration of the endometrium. These changes are brought about by ovarian and pituitary hormones. In this phase, the release of gonadotropins (LH and FSH) increases. This causes follicular growth and the growing follicles produce oestrogen.
• The LH and FSH are at their peak in the middle of the cycle (14th day), and cause the rupture of the Graffian follicles to release ovum. This phase is called the ovulatory phase.
• The remains of the Graffian follicles get converted into the corpus luteum, which secretes progesterone for the maintenance of the endometrium.
• In the absence of fertilisation, the corpus luteum degenerates, thereby causing the disintegration of the endometrium and the start of a new cycle.
• In humans, the menstrual cycle ceases to operate at the age of 50 years. This phase is known as the menopause
Fertilisation Events
Fertilisation and Implantation
• During coitus, the semen is released into the vagina, passes through the cervix of the uterus and reaches the ampullary-isthmic junction of the fallopian tube.
• The ovum is also released into the junction for fertilisation to occur.
• The process of fusion of the sperm and the ovum is known as fertilisation.
• During fertilisation, the sperm induces changes in the zona pellucida and blocks the entry of other sperms. This ensures that only one sperm fertilises an ovum.
• The enzymatic secretions of the acrosomes help the sperm enter the cytoplasm of the ovum.
• This causes the completion of meiotic division of the secondary oocyte, resulting in the formation of a haploid ovum (ootid) and a secondary polar body.
• Then, the haploid sperm nucleus fuses with the haploid nucleus of the ovum to form a diploid zygote.
• Mitosis starts as the zygote moves through the isthmus of the oviduct (cleavage) and forms 2, 4, 8, 16 daughter cells called blastomeres.
• The 8−16 cell embryo is called a morula, which continues to divide to form the blastocyst. The morula moves further into the uterus.
• The cells in the blastocyst are arranged into an outer trophoblast and an inner cell mass.
• The trophoblast gets attached to the uterine endometrium, and the process is called implantation. This leads to pregnancy.
• The inner cell mass gets differentiated to form the embryo.
You must have heard about twins. Lets know a little bit more about them.
Twins refers to offsprings which are produced from the same pregnancy. Twins are of two types –
• Identical twins – Identical twins are produced when a fertilised ovum (egg) splits into two and each of them develops into a new baby. They are genetically similar to each other.
• Fraternal twins – These type of twins are produced when two ovums are fertilised by two sperms and leads to the development of two babies which are genetically unique from each other.
Pregnancy, Parturition and Lactation
Pregnancy
• After implantation, the trophoblast forms finger-like projections called chorionic villi, surrounded by the uterine tissue and maternal blood.
• The chorionic villi and the uterine tissue get integrated to form the placenta, which helps in supplying the developing embryo with oxygen and nutrients, and is also involved in the removal of wastes.
• Placenta acts as a permeable membrane and allows diffusion of a variety of substances through it. However it does not allow passage of most of the germs from the mother to the foetus.
• Substances that pass through placenta from mother to the foetus (for utilisation)
• Oxygen
• Nutrients (glucose, amino acids, vitamins, mineral ions)
• Some drugs
• Antibodies
• Viruses
• Substances that pass through placenta from foetus to the mother (for elimination)
• CO2
• Urea and other wastes
• The placenta is connected to the embryo by the umbilical cord. The placenta also acts as an endocrine gland, and produces the human chorionic gonadotropins, human placental lactogen, oestrogen, progesterone and relaxin (later stages of pregnancy).
• These hormones support foetal growth and help in the maintenance of pregnancy. Hormones like oestrogen, progestogen, cortisol, prolactin, etc., are increased several folds in the maternal blood.
• The foetus is covered with membranes which are collectively termed as foetal membranes. These membranes are – amnion and chorion.
• Amnion and chorion together form the amniotic sac which surrounds and protects the foetus.
• The amniotic sac contains the amniotic fluid which protects the foetus and acts as a shock absorber.
• Immediately after implantation, the inner cell mass (embryo) gets differentiated into the ectoderm, mesoderm and endoderm, which give rise to the different tissues. This ability of the inner cell mass is due to the presence of multi-potent cells called stem cells.
• Most of the major organs are formed at the end of 12 weeks of pregnancy; during the 5th month, the limbs and body hair are formed; by the 24th week, the eyelids separate and eyelashes are formed. At the end of nine months, the foetus is fully formed.
Parturition and Lactation
• Human pregnancy has the duration of 9 months. This duration is called the gestation period.
• At the end of this period, vigorous uterine contractions lead to the delivery of the foetus. This process is called parturition.
• Parturition is a neuro-endocrine mechanism, and is started by the signals from the developed foetus and the placenta, which produce the foetal ejection reflex.
• This causes the release of oxytocin from the pituitary, which causes stronger uterine contractions.
• This leads to the expulsion of the baby along with the placenta.
• During pregnancy, the mammary glands undergo differentiation, and milk is produced during the end of pregnancy. • The milk produced during the first few days of lactation is known as colostrums. It contains several antibodies that aid the newborn to develop resistance.
