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Human sexual reproduction: 2. Details of the male and female reproductive systems and the development of secondary sexual characteristics

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human male genital parts functions testis scrotum seminal vesicle glands sperm duct errectile tissue foreskin KS3 science gcse biology igcse(2) The male and female reproductive systems

(2a) The male reproductive system

The sperm male sex cells (male gametes) are made in the testes after puberty, they are also involved with the production of the hormone testosterone.

The scrotum (scrotal sacs) protects and helps with the thermoregulation of the testicles by keeping the temperature of the testis several degrees below the average body temperature, which is an essential factor for sperm production.

The sperm duct (ejaculatory duct) delivers sperm into the urethra, adding secretions and additives from the prostate gland necessary for sperm function.

So, the sperm moves from the testes into the sperm duct.

The seminal vesicle gland secretes a fluid that mixes with the sperm, and the prostate gland secretes a slightly alkaline fluid that also forms part of the seminal fluid, the fluid that carries the sperm.

The penis is the external male reproductive organ and ejaculates semen into the woman's vagina during sexual intercourse (copulation).

The urethra is the tube that allows urine to flow out of the body from the penis as well as the channel through which the semen flows.


(2b) The female reproductive system

(both female diagrams need to be appreciated in terms of structural features and their function)

human female genetal parts functions oviduct fallopian tube ovary uterus lining vagina cervix KS3 science gcse biology igcseEgg - the female sex cell (gamete)

Ovaries - the organ where the eggs (ovum) are produced and stored and the site of production of the hormones estrogen and progesterone. One or both of the ovaries releases an egg every 28 days.

Oviducts (fallopian tubes) - when an egg is released it travels down this tube into the uterus where it may interact with a sperm from the vagina following sexual intercourse.

Umbilical cord - connects the placenta to the growing foetus - baby, oxygen, nutrients and waste substances pass through it (see below).

Placenta - a temporary organ that develops in the uterus during pregnancy and acts as an interface between the growing foetus and the mother's body and provides dissolved oxygen and nutrients to the growing baby and removes waste products (excretory substances) at the same time (all of which pass through the umbilical cord). The placenta also provides a barrier to protect the developing fetus-baby from harmful toxins and pathogens. However some toxins and pathogens can pass through e.g. the rubella virus, nicotine from smoking and alcohol (ethanol) from drinking alcoholic drinks.

development of embryo foetus baby in uterus womb umbilical cord ks3 science gcse biology igcseUterus (womb) - a hollow muscular organ located in the female pelvis between the bladder and rectum in which the foetus-baby develops after a fertilised egg is implanted in the uterus lining.

Amniotic (amnion) membrane - the innermost layer of the foetal membranes which surrounds the developing foetus and forms the amniotic cavity.

Amniotic sac and amniotic fluid - the amniotic sac surrounds the foetus during pregnancy and contains the amniotic fluid during gestation and in which the embryo is situated giving it a cushioning effect. Amniotic fluid is ~97% water and constantly renewed. The amniotic fluid also contains cells from the foetus, which will allow prenatal diagnosis through amniocentesis - allowing a check to see if the baby has a genetic or chromosomal condition like Down's syndrome.

Cervix - the lower, narrow end of the uterus that forms a canal between the uterus and vagina.

Vagina - a tube that connects the vulva (outer part of female genitals) with the cervix and uterus, penetration by the male penis allows sperm to travel up into the uterus. Menstrual blood leave the body through the vagina as well as expansion to allow the birth of a child.


(2c) Reminders - hormones and the regulation and development of secondary sexual characteristics

During puberty sex hormones play an important role in the sexual development of the young body combined with a growth spurt.

In young females, estrogen levels rise during puberty and this increase leads to secondary sex characteristics like breast and hip development and changes in overall body shape (more curvier).

Later in puberty, in a girl's ovaries, eggs begin to mature and the menstrual cycle can begin i.e. a matured egg is released every 28 days (ovulation and periods start).

In young males, testosterone levels rise during puberty and this increase causes boys to develop deeper voices, bigger muscles, and body and facial hair.

It also helps the testes produce sperm, penis enlarges, and testosterone it plays a role in speeding a boy's growth in height during puberty.


Keywords, phrases and learning objectives for this part on the male and female reproductive systems

Be able to interpret detailed diagrams of the male and female reproductive systems (including the nature and function of the testes ,sperm duct, penis, uretha, egg, ovaries, cervix, vagina ) and describe the development of secondary sexual characteristics in the puberty of girls and boys.


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