The Reproductive System Class 10 ICSE Notes
ICSE Class 10 Biology Chapter 13 The Reproductive System Notes, Summary, Definition, Diagram. The Reproductive System Notes.
INTRODUCTION-
Reproduction
→ Process of producing new individuals of same kind.
→ Essential for continuance of life.
Mode of reproduction
i.) Asexual –
→ No gametes are formed
→ No variation
→ More offsprings
→ Only single/one parent involved
→ Rapid process during favourable conditions
ii.) Sexual –
→ Gametes are formed
→ Increased variation
→ Fewer offsprings
→ Two parents (male and female) are involved
→ Slower process
The gametes must normally fertilize to produce a “zygote”, which produce offprings.
Secondary sexual characters
→ Distribution of hair on body and face (beard and moustaches in male)
→ Breasts in female
→ Muscularity – stronger built in males
→ Skeletal structure
→ Psyche and behaviour
→ Deeper voice in males
Reproduction in humans –
A.) Primary reproductive parts – includes gonads (testis in males which produces sperms and ovaries in female which produces eggs).
B.) Accessory reproductive parts – includes structure, ducts and glands which help transfer and meeting of two kinds of sex cells.
I.) Male reproductive system –
a) Testis –
→ (one pair) produces sperms.
→ Oval organs found inside the scrotum.
→ Scrotum is present outside the body as the testis require temperature lower than our body temperature to produce sperm.
→ Internally partitioned into around 250 lobules. Each lobule contains
1.) Seminiferous tubules- where sperms are produced known as spermatogenesis.
2.) Interstitial cells (leydig cells) – produce male hormone testosterone.
b) Sperm ducts (vas deferens)
→ From each testis travel upward into abdomen passing through an inguinal canal.
→ The 2 sperm ducts loop over the ureters of their sides join the median duct/urethra at back of urinary bladder.
c) Accessory glands-
i.) Seminal vesicles-
→ Produce a secretion which serves a medium for transportation of sperms.
→ The mixture of this fluid and sperms produce a milky fluids, the semen.
ii.) Prostate gland –
→ Bilobed structure
→ Pours an alkaline secretion into semen and neutralises acid in female’s vagina.
iii.) Bulbo-urethral glands (cowper’s glands) –
→ Two small ovoid glands which opens into urethra just before it enters the penis.
→ The secretion serves as a lubricant.
iv.) Penis –
→ Passage for both semen and urine.
→ Highly vascular organ, erectile tissues and vascular spaces.
→ Erection- during sexual stimulation, blood flows in a large amount into the penis and enters into vascular spaces or sinuses, which makes it rigid and erect, thus blood cannot drain out.
Course of sperms in male
II.) Female reproductive system
a) Ovaries –
→ Pair of ovaries, which produces ova or eggs.
→ only one egg mature in each ovary every alternate month.
→ Follicle – maturing egg contained in a cellular sac
→ Graafian follicle – the enlarged follicle which get filled with fluid
→ Oogenesis- process in which ova -producing cells give rise to mature ovum.
→ Ovulation – rupture of the follicle releasing the egg
→ The remnant of follicle persists for sometime to convert into yellow mass called Corpus luteum.
→ 2 hormone secreted –
i.) Oestrogen (secreted prior to ovulation)
ii.) Progesterone
b) Oviducts –
→ Also called fallopian tubes or uterine ducts are 12cm long.
→ Funnel shaped opening called oviducal funnel
→ The waves of muscular contraction (peristalsis) of wall of oviduct push the egg down into uterus.
c) Uterus –
→ Hollow pear shaped organ
→ 2 region- upper wider region receives the two oviducts and smaller lower region the cervix or neck.
d) Vagina –
→ Muscular tube
→ Receives the male penis during copulation
→ Elasticity of its wall allows the passage of baby during childbirth.
→ Hymen (vaginal knot) – a thin membrane which partially closes the vagina in young female. It is frequently ruptured in childhood due to strenuous physical exercise or disease.
e) Vulva –
→ External female genitalia.
→ Contains independent openings of urethra and vagina.
→ 2 small fleshy folds-
Labia minora (lesser lip)
Labia majora (greater lips)
Clitoris
Role of hormones in reproduction –
1.) Oestrogens – responsible of bodily changes like growth of mammary glands, widening of hips, growth of pubic and armpit hairs, increase in size of uterus and vagina.
2.) Corpus luteum and progesterone – prepares the uterus for receiving the embryo.
Menstrual cycle –
→ The reproductive period of female starts from 13th age to 40-45 years.
→ It is a cycle of 28 days with minor variation in every month in the form of menstrual flow.
→ The menstrual cycle is counted from the day of onset of the flow to next onset after 28 days.
i.) Menstrual phase –
→ Lasts 3-5 day during which blood is discharged.
→ Bleeding caused due to shredding of endometrium (innermost) layer.
→ Starting onset of menstruation flow, the ovary begins to form a new egg in follicle.
ii.) Follicular phase –
→ Continues from 5th to 12th day.
→ As follicles grow, amount of oestrogen produced by ovary increases.
→ Oestrogen acts on uterus and thickens its lining and develops more blood vessels.
→ Prepare uterus to receive fertilized egg and assist in early implantation of embryo and its development.
iii.) Ovulatory phase –
→ On 13th or 14th day
→ Follicles ruptures (ovulation) and release egg from oviduct.
→ Follicle stimulating hormone (FSH) and luteinizing hormone (LH) from pituitary gland, promote the maturation and release ovum.
iv.) Luteal phase –
→ Day 15th to 28th.
→ Uterus lining thickens further
→ The emptied follicle in ovary after release of ovum turns into hormone- producing tissue called corpus luteum.
If ovum fertilized, the corpus luteum continues to release progesterone to keep uterus in a suitable state for implantation.
If no fertilization, ovum disintegrates and corpus luteum stops producing progesterone.
As a result, the thick uterus lining shreds off on 28th day and release blood from cervix and vagina.
Fertilisation (union of egg nucleus and sperm nucleus)
→ Fusion of male gamete (sperm) and female gamete (ovum) to form a zygote.
→ A single ejaculation by human male contains 400 millions sperms.
→ Most favourable for conception ( becoming pregnant) is on 12th and 13th.
Functions of the main parts of a sperm
→ Acrosome – top of head of sperm secretes an enzyme (hyaluronidase) which facilitates entry of sperm into egg by dissolving the wall of the ovum.
- Nucleus contains genetic material (22 + X or 22 + Y chromosomes) , during fertilisation , combines with nucleus of the egg containing 22+X chromosomes, restoring the normal number of 23 pairs.
→ Mitochondria – middle piece, provide energy (ATP) for activity of sperm to swim.
→ Tails – makes lashing movements for propulsion.
→ During fertilisation, Only one sperm enters the egg (ovum), the entry of other sperms is prevented by a chemical barrier.
Implantation (conception) and Pregnancy
→ Fertilised egg (zygote) soon divide (cleavage) into 2,4,8,16 cells and so on .
→ Small hollow ball of numerous cells (blastocyst)
→ This kind of embryo which forms a pit in the endometrial lining of uterus and gets fixed in it about a week’s (5-7 days) time after ovulation called implantation and produces the state of pregnancy.
Amnion and amniotic fluid
→ The membranes are amnion, chlorion, allantois and placenta.
→ They play a vital role in the development of the foetus and present right upto the time of birth.
→ Amnion is sac which develops around the embryo even before the formation of allantois.
→ Amniotic fluid fills the space between the amnion and embryo.
Function of amniotic full –
→ Protects the embryo from physical damage by jerks or mechanical shocks. For example- when the mom falls over.
→ Keep an even pressure all around the embryo
→ Allows the foetus some restricted movement
→ Prevents sticking of foetus to the amnion
Placenta
→ The growing embryo/foetus needs food and oxygen which passes through it.
→ It excretes nitrogenous wastes and carbon dioxide.
→ Placenta is a disc-like structure attached to uterine wall.
→ Umbilical cord – contain blood vessels connects the placenta with foetus.
→ Villi – finger -like projections helps in easy movement
Function of placenta-
→ Permeability of placenta – permeable to respiratory gases, nutrient and also antibodies but not germs from mother to foetus.
→ Also acts as endocrine glands.
→ Produces oestrogens and progesterone
Parturition (birth)
→ Full term of the development of the embryo in the uterus is called gestation.
→ Lasts in human for 280 days.
→ During birth, baby pushed out by powerful contraction of uterus muscle, headfirst.
→ Blood vessels in umbilical cord shrink and can be tied and cut.
→ Uterus contracts and become normal in few days.
Twins – Fraternal and Identical
a.) Fraternal twins –
→ Produced from two eggs
→ Two eggs are released from ovaries at same time and both fertilised to produce 2 individuals.
→ Either both boys, either both girls or one boy and one girl.
i.) Diovular – meaning produced from 2 ova
ii.) Dizygotic – meaning produced from 2 zygotes ( 2 fertilised eggs)
b.) Identical twins –
→ Produced from one egg
→ Single fertilised egg may get split and separated into two parts during its early stages of cell division.
→ After division each becomes individual egg
→ Either both boys or both girls.
More than 2- the Triplets, Quadruplets, etc
→ Triplets – 3 born at a time , either from one single zygote, splitting into two, and one of the split parts again splitting into two, or triplets maybe produced from two eggs .
→ Quadruplets – 4 born at a time, 2 pairs of identical from 2 eggs or in other combinations of identical and fraternal twins.
Glossary-
→ Due to pressure in abdomen, the intestine bulges into the scrotum through the inguinal canal and causes “Hernia”.
→ Puberty – period during which immature reproductive system of both boys and girls matures and become capable of reproducing. Girls (at age 10) and boys (at age 11).
→ Menarche – first menstrual cycle
→ Menopause – permanent stoppage of menstruation.
→ Embryo – a growing egg after fertilisation until the main parts of body and the internal organs started take shape.
→ Foetus – when embryo starts having a look of a baby (from 7 weeks of gestation and onwards)
→ Pregnancy – the state of carrying the unborn young one inside the body.
The first cry of baby is sharp cry as it is a clearing process of the baby’s respiratory passage.
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