Download Topic 17: Reproduction

Topic 17: Reproduction
17.3 Sexual reproduction in humans
•Identify
and name on diagrams of the male reproductive system:
the testes, scrotum, sperm ducts, prostate gland, urethra and penis,
and state the functions of these parts
• Identify and name on diagrams of the female reproductive system: the
ovaries, oviducts, uterus, cervix and vagina, and state the functions of these
parts
• Describe fertilisation as the fusion of the nuclei from a male gamete
(sperm) and a female gamete (egg cell/ovum)
•State
•State
the adaptive features of sperm and egg cells
that in early development, the zygote forms an embryo which is a ball
of cells that implants into the wall of the uterus
Sexual Reproduction in
Animals
Reproduction - Ability to produce
individuals (offspring) of the same
species
 Most animals reproduce sexually. In
sexual reproduction male and female
parents produce sex cells or gametes,
the nuclei of which contain the genetic
material.
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Sexual reproduction in humans
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Humans are characterized by:
Internal fertilization: means that the gametes
(sex cells) fuse inside the body of the female
Internal development: means that the
embryo grows inside the body of female
Gonads are the organs responsible for
producing gametes
Male gonads are testis
Female gonads are ovaries
Male sex cell
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Male gamete = sperm – produced in
testes and deposited though intercourse
(mating) into female reproductive tract by
male reproductive system
Female sex cell
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Female gamete – egg (ovum) – produced in
ovaries – fuses with male sperm to form a
zygote (which develops into a baby) in the
female reproductive tract. The egg cell has
energy stores and a jelly coating that changes
after fertilisation
A human egg surrounded by sperm
- one of which will fertilise it
fertilization
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Each gamete contains half the number of parental
chromosomes. The two gametes fuse together during
fertilisation to make a new individual with a full set of
chromosomes
The sperm has flagellum for swimming to reach the
ova and the presence of enzymes to digest the wall of
ova
Reproductive system
Male reproductive system
Carries urine
from kidney
to bladder
Secretes fluid known as the
seminal fluid to mix with
the sperm, this fluid
consists of:
•Mucus: facilitate
copulation and swimming
of sperms
•Sugars(fructose) : provide
energy for sperm
•Alkaline material to
neutralize the acidity of
urethra and vagina
Coiled tube,
Storage of
sperm
Site of sperm
maturation
Carries sperm from
epididymis to urethra in
penis by wave-like muscular
contractions (peristalsis) to
help in ejaculation
Sac of skin, containing testes –
hold it outside the body
At lower temperature (below
body temperature of 370C)
for sperm formation
Sperm cannot survive for long
at 370C
Produces sperm
and the hormone
testosterone (sex
hormone)
Common passage for both urine and
semen
(semen is the sperms plus the fluid
produced by prostate gland and
seminal vesicles)
Has muscular wall to contract to help
in ejaculation
Male reproductive system
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Penis:
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Organ of copulation
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Contains erectile tissue which has blood cavities, when penis is stimulated blood fills
the cavities making the penis long and strong enough for copulation, this is known
as erection
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Covered with a piece of fore skin which is removed in the process of circumcision
Female reproductive organ
•Narrow tube
carrying eggs from
the ovaries to the
uterus
•Has ciliated cells to
push the ova into
the uterus
•Site of fertilisation
Muscular organ
site of implantation of
fertilises egg and embryo
Site of formation of
placenta
Are two , right one and left
one
•Produces and releases ova
(singular: ovum) into the
oviduct
•Produces hormones
•Oestrogen – repairs uterine
lining after menstruation
•Progesterone – maintains
uterine lining after repair
Organ of copulation
Muscular and elastic
tube into which male
penis is place during
intercourse
Expand during birth
Muscular ring that
separates the uterus
and vagina
Secretes mucus to
help the sperm to
swim
Some adaptations:
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Uterus:
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the lining is soft and spongy with many blood vessels to supply the
embryo with food and oxygen
In the lining implantation of the embryo takes place (where the
emvbryo fixes itself to the lining of uterus
If there is no fertilization the lining is broken down releasing blood ,
this is called menstruation
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Some adaptations:
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Vagina:
Expands during birth
 Secretes mucus to facilitate the movement of male
organ during copulation
 Secrets acid to kill bacteria and other microorganism
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Intercourse
Due to stimulation, the blood
pressure increases in the
penis and becomes stiff and
erect
 The penis is inserted in the
vagina and moves rhythmically
 The muscles of epididymis,
sperms ducts and urethra
contract in a wave motion to
push sperms
 Seminal vesicle and prostate
gland produce seminal fluid to
be mixed with sperms and
form the semen
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Fertilization
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Sperms are deposited on the top of vagina below the
cervix
Sperms swim using their tails through the cervix and
the film of moisture lining the uterus
Sperms are attracted to the ovum due to chemicals it
produces
Many sperms reach the egg, each sperm produces
enzymes from its head to digest a way into the egg
The sperm leaves the tail outside then the nucleus of
the sperm and that of ovum fuse together to form
the zygote
Once a sperm has succeeded in penetrating the egg ,
a fertilization membrane is formed quickly to prevent
any other sperm enter the ovum
Some definitions
Zygote: a cell formed due to the fusion of
a male gamete and a female gamete
 Embryo: a ball of cells formed due to
division of the zygote by mitosis
 Fetus: a mammalian embryo in advanced
stage of development
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embryo
Implantation (read only)
Formation of embryo due to successive
division of the zygote by a method of division
called mitosis
 Menstrual cycle stops, until after the baby is
born
 Implantation takes place, the process by which
the embryo attach to the lining of uterus
 Formation of amnion and placenta
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What will
happen if no
fertilization ?
Next slide
Reproduction
Sexual reproduction part 2
 State the functions of the umbilical cord,
placenta, amniotic sac and amniotic fluid
 Outline the processes involved in labour
and birth
 Describe the ante-natal care of pregnant
women, limited to special dietary needs
and the harm from smoking and alcohol
consumption
Menstruation
It is the break down of
the lining of the uterus
in case there is no
fertilization
 It takes place due to a
drop in the level of
hormone called
progesterone (the
function of this
hormone is to
maintain the lining of
the uterus)
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Menstruation and ovulation
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Ovulation is the release of ova into the
oviduct, it takes place at day 14 of the
menstrual cycle
menstruation
estrogen
ovulation
Amnion(amniotic sac or water sac)
Secretes amniotic fluid
which:
1. Act as shock
absorber
2. Protects the embryo
against adhesion of
organs.
3. facilitates the
movement of fetus
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placenta
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The placenta is an organ that connects the
developing fetus to the uterine wall
Blood in placenta includes:
Maternal blood from uterine artery
Fetal blood from umbilical artery and the umbilical vein
in the umbilical cord
Importance of placenta:
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Exchange of gases:
Oxygen from mother’s blood diffuses into fetal blood
CO2 from the fetal blood diffuses into mother’s blood
Nutrition:
Food such as glucose and amino acids diffuses into fetal blood
Excretion:
Waste products such as urea diffuses from fetal blood into
mother’s blood
Secretion of hormones:
Secretes estrogen and progesterone to:
Keep the uterine lining support the embryo
Stimulate the growth of milk-producing tissues in the woman’s
breast
Prevent anymore to be released during pregnancy
Importance of placenta:
Fetal blood and maternal blood never mix in
the placenta so :
 Protects the fetus against high blood pressure
 Protects the fetus against bacteria from mother’s
blood(but viruses like HIV can pass because they
are very small)
5.
Umbilical cord
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Connects the placenta and fetus
It contains:
Umbilical artery: carries CO2 and other waste products
of the fetus to placenta
Umbilical vein: carries O2 and food materials from
placenta to fetus
How to care for the baby
Ante-natal care
Diet:
 Must include protein for building cells
 More carbohydrates and fats for energy
 More minerals as calcium for bones and iron
to form hemoglobin
2. Drugs:
 Extra precautions
 Drugs must be avoided because they can
pass through the placenta to fetal body and
cause abnormalities
1.
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How to care for the baby
Ante-natal care
Smoking:
 Must be avoided, it can result in small and
less healthy body because:
 CO (carbon monoxide) can reduce the
oxygen supply as it combines with
hemoglobin forming stable
carboxyhemoglobin
 Nicotine makes the fetal heart beats
more quickly
3.
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Smoking abnormalities
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How to care for the baby
Ante-natal care
Alcohol:
 Should be avoided because it causes
 Abnormalities in fetus
 Premature baby
 Miscarriage
4.
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Alcohol abnormalities
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