5.

Reproduction
3ºESO
How can we adapt to different
environments?
1 Human reproduction
1.1 Characteristics of human reproduction
Humans reproduce sexually thanks to the gametes→ male and female
reproductive systems
● Procesess

1. Gamete formation
2. Fertilisation
3. embryonic development
4. Birth
1. Gamete formation

● Human are unisexual→ each type of gamete is produced by a

particular sex.
● We can also appreciate sexual dimorphism→ physical
differences between the two sexes
● Gametes contain half of the genetic information (23
chromosomes) of each progenitor
■ Ova→ female
■ Espermatozoa→ male
2. Fertilisation
Is the union of the gametes→ form the zygote
Happen in the female reproductive system

3. Embryonic development
It is the complete development of the zygote
inside the mothers body.

4. Birth
The development has been completed→
leaves the mothers body and develops the
vital functions by itself
1.2 Sexual maturity
● When an individual is born has the main characteristics asociated with a
particular sex (chromosomes) but the maturity of the organs happen
later in life.
● During puberty the levels of sexual hormones increase→ sexual and
reproductive abilities
● Which are the hormones
that regulate the
development of sexual
characteristics?

● Why do you think men tend

to develop greater muscles
in adulthood? Why their
voice changes?

● Why women tend to develop

greater amount of body fat
and widen the hips?
2. reproductive system
2.1 The male reproductive system
The main goal→ introduce the
spermatozoa into the female
reproductive system
Parts:
● Testes
● Reproductive tract
● Penis
● Glands
Testes:

● Are the male gonads

● Are located outside of the
abdominal cavity covered by
scrotum.
● They are also endocrine glands→
male sex hormones
● Each one is composed by→
seminiferous tubules where
spermatozoa is produced
The reproductive tract

● The epididymis: is a tube

situated in the upper part of the
testicles. The tubules of the testes
converge there an is where the
spermatozoa are stored.
● The vasa deferentia→ connect
the epididymis with the urethra
● the urethra→ semen and urine
leave the body
Penis

● Through penetration the spermatozoa is deposited in the female organ.

● The end is wider and is known as glans. Is protected by the foreskin.

Accessory glands:

Release secretions into vasa deferentia joining spermatozoa and forming

semen.

● Seminal vesicles→ release nutrients for sperm

● Prostate gland→ motility of sperm
● Cowper´s gland→ lubricating secretion that neutralises acidity in uretra
and vagina
2.2 The female reproductive system
The function of the reproductive system in female:
● Contact between the ova and spermatozoa.
● Feed and protect the embryo
● Give birth
Parts:
1. Ovaries
2. Female reproductive tract
3. Vulva
Main parts of the female reproductive system
1. The ovaries: are the female
gonads
● Located in the pelvic
areas.
● Certain amount of ova
since the birth.
● They act as a endocrine
system as well→
oestrogen/progesterone
2. The female reproductive tract

The fallopian tubes→ 2 tubes that connects the

ovary→ uterus. The inside part of the tubes are ciliated
cells→ directs the ova to the uterus.

Uterus

● Size and shape of a pear

● Two layers→ External: muscular and thick wall
● Internal→ epithelial layer→ endometrium. The
embryo attaches to this layer after fertilisation

Cervix→ lower part of the uterus which connect with

the vagina

The vagina→ flexible walls connect the uterus with the

external environment.

3. The vulva→ two fold of skin called labia

Activity: sexual dimorphism
● What is sexual dimorphism?
● When does the development of sexual
characteristics begin in humans?
● Which hormonal/endocrine axis
regulates sexual maturity?
● Testosterone and estrogen can only be
found in male/female respectively?
● What are aromatase and 5-alfa
reductase and why are key in sexual
development?
3. Human Gametes
● Gametes are the cells responsibles for the
human reproduction:
● Spermatozoa (male) → formed in the
testis, half of the genetic information of
human being(23 chromosomes)
● Ova (female) → formed in the ovary, half of
the genetic information of the specie (23
chromosomes)
3.1 Spermatozoa
Spermatozoa, main characteristics:
● Formed in the seminiferous
tubules in the testis
● The process that created is a
meiosis called→
spermatogenesis
Parts:
● Head→ the nucleus (genetic
information)
● Middle piece→ mitochondria→
releases energy→ movement of
the tail
● The tail→ long flagellum
Spermatogenesis:

Produced in the walls of the seminiferous tubules→ constant meiotic

divisions that form sperm throughout the lifespan.
 3.2 Ova
● Female gametes that are formed in the ovaries→
oogenesis
● Immobile cells which contains nutritious substances →
embryo
Main parts:
● Nucleus→ half of the genetic information of the specie (23
chromosomes in human beings)
● Cytoplasm→ vitelline membrane (nutrients), first stages of
the embryo
● The membrane, covered by two layers
● Zona pellucida and corona radiata→ attracts the sperm,
block secondary fecundation
Ovogenesis:

Ova are form in the ovaries in the

uterine period (while still a fetus) but
they are immature.

During puberty ova begin to mature

cyclically→ release of a mature ova
monthly → breaks the follicles
 4.1 The ovarian cycle
● Growth of the follicles ● Ovulation ● Corpus luteum

(Day 1-14) (Day14+-) (Day 14-28)

the hypophysis releases FSH (Follicles one of the follicles gets fully mature→ forming the corpus luteum that
Stimulating Hormone) → maturity of release a ovum. High levels of FSH and releases oestrogen and progesterone
the ova inside the follicles. Oestrogen is LH → prepare the uterus for the embryo. If
also released in this stage it is not fertilised→ restart the cycle
 4.1 Uterine cycle

Menstruation Growth of Secretory phase

endometrium
Day 1-5 Day 15-28
Day6-14

The surface of the Starts right after the end of If the ova is fertilised the corpus
endometrio is expelled out menstruation. luteum→ hormones that sustain
of the body→ vagina the endometrium→ embryonic
Regrowth of the development
It is known as the period, endometrium
and is related to the
degeneration of the corpus
luteum
Activity: sexual hormones and health
Sex hormones play a key role in sexual
development. This requires proper nutrition and
lifestyle habits,
Research:
● What is the precursor molecule of sex
hormones.
● What foods are harmful to the correct
formation of sex hormones.
● What are the long-term effects of consuming
steroids?
● How does the "day after" pill work and what
effect does it have on hormonal balance?
5. Fertilisation pregnancy and birth
5.1 Fertilisation and embryonic development

● Fertilisation→ union of the ova and the sperm to form a zygote.

● The process occurs in the fallopian tubes → directed to the uterus.

● Embryonic development→ developmental period since the zygote is

formed until birth.
1. After fertilisation the zygote travels to the uterus.
2. The first cell divisions happen in this trip, the zygote is now known as
embryo.
3. When the embryo reaches the endometrium (inner part of the uterus)
→ implantation

Once the implantation take place:

- Development of placenta → organ that provides nutrients and

exchange of waste with the mother → umbilical cord.
- Amnion→ sac filled with amniotic fluid→ protects the embryo
Development of the embryo
1t trimester → development of the organs, including the brain that starts its
formation around day 18→ we call it foetus

2nd trimester → the skeleton ossifies and the nervous system matures→ first
neural reflexes. Ex: first senses→ hearing 18 weeks

3rd trimester → growth and maturity of the organs. Lungs become functional
Labour and Birth
After 40 weeks of gestation (9 complete months) →
birth. Steps:

- The pituitary/hypophysis of the mother release

oxytocin→ contraction of the uterus→ labour
- Labour main stages:
- Dilatation: expansion of the cervix so the child can get out.
In this stage the amniotic sac breaks.
- Expulsion: contraction are more frequent and regular→
expulsion of the baby. Cut umbilical cord→ lung stimulation
- Afterbirth: detach the placenta and expel it from the body.
6. Birth control
There are many ways in order to prevent undesired
conception:
● Physical barriers→ prevents not only conception but the
transmission of many other illnesses like Hepatitis→
condoms/diaphragm

● Chemical methods→ the pill/ day after pills/ spermicides

● Surgical methods→ vasectomy/ tubal ligation

STI: sexually transmited illnesses
● Some of this illnesses can be caused by
bacteria→ chlamydia, gonorrhoea,
syphilis (can cause death and
neurological damages)

● Some can be caused by viruses→

herpes (blisters in the genitals), AIDS
(immunosupression), HPV
(papillomavirus→ uterine cancer)
DEBATE
Divide the class into 4 groups:
Research arguments in the following areas:
● Genetic engineering in agriculture.
● Genetic engineering and farming
● Genetic engineering and health
● Genetic engineering and vaccines
1. Each group should research on one of the points
and defend its project as an advantageous
advance for society;
2. Each group has to find also the weaknesses and
problems derived from the rest of the topics.
3. The winner will be the group that better defend
itself against the counterarguments of the class
Debate- aborto

Anticonceptivos orales y efecto largo plazo

hepatitis cancer cuello utero

Estres y reaccion emocional en os organos reproductores

Aborto expontaneo y presencia de machos no dominantes→ bruce effect

ingenieria genetica bebes de diseño

madurez pulmonar

antojos del embarazo

Ritos animales → placenta

CRISPR

Clonación