1.6 Human reproduction

Natural sciences

Grade 9

Life processes: healthy life

Module 7

Human reproduction

• Reproduction is the process by which offspring are created.
• During this process, GAMETES (generative sex cells) have to unite.
• The male gametes are called SPERM CELLS and female gametes are OVA , or egg cells. Both gametes carry the genetic characteristics of the new individual.

Sperm cell and ovum

• In both sexes, gametes only begin to be produced after PUBERTY . Hormones from the brain control maturation.
• The cells are formed in the sexual organs, namely in the TESTES of the male and in the OVARIA of the female.

Male sexual organs:

• 1. 2 TESTES in the external SCROTUM
• SPERM TUBES that carry sperm cells from the testes to the PROSTATE GLAND and other glands.
• The PENIS , which is responsible for transferring the SEMEN (sperm cells and nutrients) to the female system. The release of semen is called EJACULATION .

Female sexual organs:

• 1. Two FALLOPIAN TUBES for guiding the ova from the ovaries. FERTILIZATION normally occurs here.
• A UTERUS situated just behind the bladder and in which an infant will develop.
• A VAGINA that receives the sperm cells from the penis and which also serves as birth canal.

Male and female sexual organs:

The menstrual cycle:

• 1. A cycle that commences in girls once they have reached puberty (commencement varies between the ages of 10 and 15).
• This cycle prepares the female body for possible pregnancy.
• It involves the thickening of the ENDOMETRIUM inside the lower portion of the uterus in the area where an embryo will attach itself.
• Various hormones such as progesterone and ESTROGEN are involved in preparing the body for possible pregnancy. The levels of these hormones rise and recede and cause a variety of changes that may be very uncomfortable for a girl, e.g. moodiness, tenderness of the breasts, water retention.
• Halfway through the cycle, the egg cell (ovum) is released from the ovary. This is known as ovulation .
• The normal duration of the cycle is 28 days. At the end of this period the endo­metrial layer loosens from the uterus and is discarded. This casting off of the endometrial tissue is known as MENSTRUATION and the process takes 3 to 7 days.
• Girls use protective sanitary pads or tampons to absorb the flow of blood.

Fertilization: the combination of a male sperm cell with a female ovum to form a zygote

• 1. This occurs in the Fallopian tube
• A special chemical membrane develops immediately to prevent other sperm from penetrating the ovum.

Pregnancy:

• 1. The zygote immediately begins to divide repeatedly to form an embryo .
• A chemical message that travels through the woman’s body stimulates further changes.
• The developing EMBRYO attaches itself to the ENDOMETRIUM , the lining of the wall of the UTERUS . This process is known as IMPLANTATION .
• A PLACENTA develops where the embryo is attached and this nourishes the embryo while it is developing into a foetus. The foetus is attached to the placenta by means of the UMBILICAL CHORD .
• The developing foetus is supplied with nutrients and oxygen through the UMBILICAL CHORD and waste materials from the foetus, like carbon dioxide, are also removed through this chord.
• When the embryo is nine weeks old, it is called a FOETUS.
• The development of the foetus is completed in approximately 280 days or 9 months.

Class Activity: Discussion on reproduction

1. Explain what is meant by:

a) IMPLANTATION

b) OVULATION

c) FOETUS

d) PUBERTY

e) MENSTRUATION

2. What is the function of the following?

Testis

Ovaries

Penis

Scrotum

Uterus

Fallopian tubes

Placenta

Umbilical chord

3. What is an ECTOPIC PREGNANCY?

4. Explain how the following sets of twins develop:

a) identical or monozygotic (uniovular) twins;

b) non-identical or dizygotic (fraternal) twins

c) Siamese twins

5. What determines whether the baby will be male or female? Explain.

Assessment: CLASS DISCUSSION

Were you able to complete the table and answer the questions?

[LO 1.3]

Assessment

Learning Outcomes 1 : Scientific Investigation

The learner will be able to act confidently on curiosity about natural phenomena, and to investigate relationships and solve problems in scientific, technological and environmental contexts.

We know this when the learner:

• evaluates data and communicates findings.

Memorandum

CLASS ACTIVITY: GROUP DISCUSSION- REPRODUCTION

1. a) implantation of embryo into the wall of the uterus

b) release of ovum from ovary

c) developing embryo after two months

d) sexually mature phase in boys and girls

e) shedding of preparatory layer in the monthly cycle

2. Complete:

3. a pregnancy in which the embryo is implanted in the wall of the Fallopian tube instead of the uterus

4. a) a single zygote that divides early in its development – identical information; always of the same sex

b) two zygotes and two different sperm cells; two different individuals

c) uncompleted identical division

5. father donating X or Y chromosome