CLASS 10 BIOLOGY (22-23 SESSION)
LESSON 10 REPRODUCTIVE SYSTEM
Solutions to the Exercise questions of Reproductive System by BYJUS is provided in the link
given below:
https://byjus.com/icse-selina-solution-concise-biology-class-10-chapter-13-the-reproductive-system/
Video links:
https://youtu.be/D-gPmMCOKeg
https://youtu.be/bOHu9AI9OQE
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What is reproduction?
Reproduction is the process of producing new individuals by an organism of
the same kind which in turn can repeat the process.
Types: Asexual, Sexual.
M ALE REPRODUCTIVE SYSTEM
Also called the male uro-genitalsystem as sperms and urine have a
common passage from urethra which is called penis.
A) PRIMARY REPRODUCTIVE ORGANS: TESTES (singular testis)
1. Paired, oval organs, situated outside abdominal cavity in loose sacs called
scrotum/ scrotal sacs.
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2. Testes descend into scrotum through the inguinal canal a little before birth
as scrotum has a lower temperature than abdominal cavity which is
suitable for production and maturation of sperms by testes.
3. Each testis divided into 200-350 lobules. Each lobule has 2 parts:
a) Seminiferous tubules- produces sperms by a process called
spermatogenesis (gametogenesis in general).
b) Interstitial cells of Leydig- producing male hormone testosterone. This
hormone helps in sperm maturation, growth and development of male
reproductive organs, development of male secondary sexual
characteristics.
Note: 1.Testes are considered as endocrine tissue as it has endocrine function
of secreting the hormone testosterone and also non-endocrine function of
spermatogenesis (producing sperms).
2. Hernia- a condition in which the intestine bulges into the scrotum
through the inguinal canal due to pressure exerted by abdomen usually after
any surgical procedure.
B) ACCESSORY REPRODUCTIVE ORGANS:
1) DUCTS: From the testes, the sperms move through a system of ducts to
finally reach the urethra.
Testes→ Rete testis (network of tubules)→ Vasa efferentia (12-14
ducts)→Epididymis→ Vas deferens (sperm duct)→ Urethra
Epididymis- highly coiled duct, begins from the upper part of testis,
traverses along its back and joins the vas defenens. Its function is
storage and maturation of sperms.
Vas deferens- travels up from the testes through the inguinal canal into
the abdominal cavity, loops over the ureters and opens into the urethra.
Its function is to transfer sperms from epididymis to urethra.
2) ACCESSORY GLANDS:
a) Seminal vesicle: paired, located between urinary bladder and rectum.
Each gives out a duct that joins the vas deferens to form a 2cm long
ejaculatory duct before opening into the urethra. Produces a secretion for
providing a medium for transportation of sperms.
b) Prostate gland: single, bilobed, surrounding the urethra at the base of the
bladder. Produces an alkaline secretion to neutralize the acidic
environment of the female reproductive tract.
c) Bulbo-urethral gland/ Cowper’s gland: Paired, located below the prostate
gland. Its secretion lubricates the penis.
Note: Semen- an alkaline, milky and sugary fluid which is a mixture of
sperms and secretions of the accessory glands.
 Alkaline nature neutralizes the acidic environment of the female
tract so that sperms can survive.
 Sugar present provides energy for the movement of sperms.
3) SUPPORTIVE STRUCTURE: PENIS: Cylindrical, highly vascular, made
of erectile tissue, becomes rigid and erect under sexual stimulation.
Serves as a passage for both sperms and urine.
STRUCTURE OF SPERM
Head: contains a specialized lysosome that secretes an enzyme called
hyaluronidase for dissolving the outer membrane of ovum for easy
penetration by the sperm. Also contains a nucleus.
Midpiece: contains mitochondria that gives energy to the sperm for
locomotion. Also has centrioles.
Tail: helps in propagation of the sperm along its course.
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FEM ALE REPRODUCTIVE SYSTEM
A) PRIMARY REPRODUCTIVE ORGANS: OVARIES
1. Paired, oval bodies, located one on either side of the uterus in the
pelvic cavity of female.
2. Only one matured egg is produced by each ovary alternately every
month.
3. Consists of ovarian follicles at various stages of maturity like
primary, secondary etc.
4. A fully matured ovarian follicle is called Graafian follicle
containing a matured ovum.
5. Ovary produces ova (singular ovum) by a process called oogenesis.
6. Graafian follicle secretes a hormone called oestrogen.
7. It ruptures to release the matured ovum which penetrates the
ovarian wall and lies outside in the pelvic cavity/ abdominal
cavity. This process is called ovulation.
8. The remainings of the Graafian follicle transform into an yellow
mass of endocrine tissue called corpus luteum.
9. Corpus luteum secretes the hormones Oestrogen, progesterone and
relaxin.
Note:
Ovary can be called as endocrine tissue as it has endocrine
function of producing hormones as well as non-endocrine function
of producing ova by oogenesis.
Ovulation is the release of mature ovum from the ovary into the
pelvic cavity by the rupture of the Graafian follicle.
B) ACCESSORY REPRODUCTIVE ORGANS:
1. Oviducts:
➢ Also called as Fallopian tubes, paired, originating one from
each ovary.
➢ Carries the ovum from the ovary to the uterus.
➢ Oviduct has inner lining of ciliated epithelium, fluid current
and shows peristalsis of the muscles in its wall. All these
help in movement of ovum along the oviduct.
2. Uterus:
 Hollow, pear-shaped organ situated in the pelvic cavity
between urinary bladder and rectum.
 It has 3 parts- upper dome-shaped head called fundus, body
and a lower narrowed part called cervix.
 Its walls have 3 layers of muscles. From outside inwards
these are- perimetrium, myometrium and innermost
endometrium.
3. Vagina:
✓ Muscular tube, serving as lower end of the birth canal.
✓ Receives the penis during copulation.
4. Vulva: External female genitalia corresponding to penis in males.
Note: Puberty is the period during which reproductive organs of
humans mature and they become capable of reproduction.
The course and fate of the egg/ovum inside the female’s body
since its production can be outlined as follows:
Ovulation→ Fertilisation→ Implantation→ Gestation→ Parturition
These events will be now briefly discussed:
 A matured ovum is released from the ovary by ovulation as already defined.
 It will be soon picked up by finger-like projections surrounding the mouth of the
oviducal funnel (expanded anterior end of oviduct/Fallopian tube) called fimbriae.
 If the ovum meets a sperm in the oviduct, then fertilization occurs in the oviduct.
Fertilisation is defined as the fusion of sperm and ovum to form a zygote.
 The zygote divides by mitosis to form a solid ball of cells called morula, which further
divides to form a hollow ball of cells called blastocyst. By this time, it has already
reached the uterus.
 The blastocyst fixes itself to the endometrium (innermost muscle wall) of the uterus.
The fixation of the blastocyst to the endometrium of the uterus 7-8 days after
fertilization is called implantation.
 This is done to obtain required nutrition from the mother by the developing embryo.
 When the embryo is 8 weeks old, it is called the foetus. It needs food and oxygen, it
also needs to eliminate nitrogenous wastes. This work is done through the placenta.
 The placenta is a disc-like structure attached to the wall of uterus. It is formed by 2
sets of villi (finger-like projections)- one set formed by uterine wall and the other set
formed by a membrane covering the embryo called allantois. The 2 sets of villi
interlock but never fuse.
 There is never any mixing of foetal blood and maternal blood.
 A cord or rope-like structure connects the placenta with the abdomen of the foetus.
This blood-vascular connection between the mother and the foetus is called
umbilical cord.
 Functions of placenta:
1. Tranfers nutrients from mother to foetus.
2. Tranfers wastes from foetus to mother.
3. Acts as a barrier against microbes which might enter from maternal to foetal
blood.
4. Acts as an endocrine gland- secretes hormones oestrogen, progesterone and
relaxin which were so long secreted from corpus luteum. After pregnancy, this
work is done by the placenta.
 The full term development of the embryo inside the mother’s uterus for a period of
280 days is called gestation.
 During this gestation period, the embryo develops many coverings around itself
called extra-embryonic membranes like amnion, chorion, allantois.
 The amnion develops around the embryo and encloses a fluid called amniotic
fluid in which the foetus remains floating.
 Functions of amniotic fluid to be studied from the book directly.
 The act of expulsion of the full term foetus from the uterus of the mother at the end
of gestation is called parturition.
ROLE OF HORMONES IN REPRODUCTION
PITUITARY HORMONES:
1. Follicle-stimulating hormone (FSH)→ helps in development of ovarian follicles
from primary to secondary to Graafian follicle. These follicles start secreting
oestrogen.
2. Luteinising hormone (LH)→ helps in growth and development of corpus luteum.
The latter secretes oestrogen, progesterone and relaxin.
OVARIAN HORMONES:
1. Oestrogen-stimulates growth of uterus, vagina, mammary glands, and also
development of secondary sexual characteristics.
3. Progesterone- prepares the uterus for implantation, growth and development
of foetus. So it is called the “pregnancy hormone”.
4. Relaxin- Relaxes/dilates the uterine cervix during childbirth.
NOTE:
➢ IDENTICAL/ MONOZYGOTIC TWINS:
Forms when a single fertilized egg splits into two parts, they share a
common placenta, usually of the same sex but may be different, each
part grows as a separate individual.
➢ NON-IDENTICAL/ DIZYGOTIC/FRATERNAL TWINS:
If 2 ova are released by the same or different ovaries at the same time
and are fertilized by two different sperms, then two individuals are
formed, they have their own placenta, may or may not be of the same
sex.
MENSTRUAL CYCLE
A cyclical event that occurs in females during the reproductive period of
13 to 45-50 years. Here, there is a periodical shedding of blood
alongwith unfertilized ovum after every 28 days.
Menarche- onset of menstrual cycle in a young female at about 13
years.
Menopause- permanent stoppage of menstruation.
The menstrual cycle is a series of changes in the endometrium of a
non-pregnant female that prepares the lining of the uterus to
receive a fertilized egg.
Note: Along with changes in the uterine wall, changes also occur
in the ovary during this cycle. These changes are influenced by
pituitary and ovarian hormones.
It can be divided into 4 phases:
1. Menstrual phase- day 1 to 5, characterized by shedding of
endometrial lining and elimination of blood, mucous, wornout epithelial cells and unfertilised ovum. Ovary starts
developing a new follicle. Low level of Oestrogen and FSH
secretion.
2. Follicular phase- day 6 to 13, endometrium starts to thicken
and develop more blood vessels, ovarian follicle matures to
form Graafian follicle, FSH and oestrogen secretions rise to
a peak.
3. Ovulatory phase- day 13 or 14, ovulation occurs by rupture
of the Graafian follicle. LH secretion suddenly rises.
Oestrogen falls temporarily.
4. Luteal phase- corpus luteum develops due to high levels of
LH. Both oestrogen and progesterone level rise considerably.
Note: If the ovum is not fertilized, it disintegrates , corpus
luteum stops producing progesterone. The endometrium is
shed and a menstrual cycle begins.
If the ovum is fertilized, the corpus luteum persists and
secretes hormones till the placenta is formed. The uterus is
maintained in a state suitable for implantation.
Video courtesy: SHIKSHA HOUSE