(3a) Reproduction in humans

Describe fertilisation

Fusion of male and female gamete to produce a zygote that undergoes cell division and develops into an embryo

Name six parts of the male reproductive system

Prostate gland, sperm duct, urethra, testis, scrotum, penis

What is the prostate gland for

Produces semen

What does semen do

Provide nutrients to sperm

Where is semen produced

Prostate gland

What is the sperm duct for

Sperm passes through to be mixed with gland fluids before going through the urethra to be ejaculated

Where does sperm get mixed with gland fluids

Sperm duct

Where does sperm travel through (immediately) before being ejaculated

Urethra

How come semen does not mix with urine

Ring of muscle in urethra prevents this

What is the urethra for

Carries urine or semen, ring of muscle to prevent mixing

What are testis for

Produce sperm and testosterone

Where is sperm produced

Testis

Where is testosterone produced

Testis

What is the scrotum for

Bag of skin containing testes

What is the penis for

Pass urine from the bladder, allow semen into vagina during sex

What are the oviducts

Tubes connecting ovaries to uterus

Where does fertilisation occur

Oviducts

How are the oviducts adapted for their function

Lined with ciliated cells which push ovum

What are the ovaries for

Contain ova (female gamete)

What is the uterus

Muscular bag

How is the uterus adapted for its function

Soft lining where fertilised egg (zygote) implants to develop into a foetus

Where does the zygote implant

Uterus lining

What is the cervix

Ring of muscle at lower end of uterus

What does the cervix do

Keep foetus in place during pregnancy

What is the vagina

Muscular tube leading to inside of the body

What is the vagina for

Penis enters and deposits sperm here during sex

The menstrual cycle is an example of a…

Secondary sexual characteristic

How long is a menstrual cycle usually?

28 days

On which day of the menstrual cycle does ovulation occur?

14

What is menstruation?

Breakdown of the uterine lining due to lack of fertilisation

Describe what happens after menstruation

Uterus lining starts to thicken again in preparation for possible implantation in next cycle

Describe day 1-7 of the menstrual cycle

Menstruation - lining broken down. Oestrogen starts rising

Describe days 7-14 of the menstrual cycle.

Lining starts to build up. Oestrogen causes egg to mature and peaks just before it is released

What is ovulation

The release of an egg from the ovaries

What happens on day 14 of the menstrual cycle?

Ovulation

When does menstruation occur?

Days 1-7

Describe days 14-28 of the menstrual cycle

Lining thickens, maintained. Progesterone rises once ovulation occurs.

What does the fall in progesterone around day 28 do?

Cause menstruation

What is menstruation caused by

Fall in progesterone

Which hormone stimulates the uterus to develop lining to replace that lost in menstruation?

Oestrogen

What does oestrogen do?

Stimulate ovaries to repair and develop uterus lining

How does oestrogen influence the release of other hormones?

Inhibits FSH, triggers release of LH when high enough

Name the two hormones produced in the ovaries

Oestrogen and progesterone

Name the two hormones released from the pituitary gland

FSH and LH

What does progesterone do?

Maintain and thicken lining

How does progesterone influence the release of other hormones?

Inhibits FSH and LH

What does FSH do?

Cause follicle to develop; egg starts maturing

How does FSH influence the release of other hormones?

The follicle it stimulates will produce oestrogen

What does the follicle do (FSH)

Produce an egg and oestrogen

What happens after FSH is released from the pituitary gland

Oestrogen is released from the follicle

Why does oestrogen inhibit FSH

Only one egg matures per cycle

What does LH do

Triggers ovulation (release of mature egg)

How does LH influence the release of other hormones

stimulates progesterone production (from corpus luteum)

What is the corpus luteum

Remains of follicle after it has released an ovum into fallopian tube

An oviduct is also known as

Fallopian tube

What happens if an egg is fertilised

Corpus luteum continues producing progesterone until placenta develops and takes over the progesterone

Why do progesterone levels drop if the egg is not fertilised

Corpus luteum breaks down so progesterone no longer being produced

What happens after fertilisation in the oviduct

Zygote divides to form an embryo which travels to the uterus and implants in the lining

Where does the placenta form

Implantation site

What phase is the baby in when it implants

Embryo

How is the embryo and mother’s blood connected

Placenta: very close but don’t mix directly. Umbilical cord connects embryo blood supply to placenta

What is the role of the placenta?

Enable exchange of substances between mother and foetus’ blood

What substances are transferred from the mother to the foetus via the placenta?

Oxygen; Nutrients: glucose, amino acids, mineral ions

What substances are transferred from the foetus to the mother’s blood via the placenta?

carbon dioxide; urea

How is the placenta adapted to be an efficient exchange surface?

Large surface area; thin wall for short diffusion distance

What is an additional role of the placenta?

Acts as a barrier to several toxins and pathogens

Although the placenta can act as a barrier to toxins and pathogens, what are some substances that can still pass through?

Nicotine, alcohol, virus particles

Where is the amniotic fluid found?

Surrounding the embryo, within the amniotic sac

What is the role of the amniotic fluid?

Protect developing embryo by cushioning it from bumps when mother moves around

What hormones trigger the development of secondary sexual characteristics?

Oestrogen In females; testosterone In males

What are secondary sexual characteristics?

Changes that occur during puberty; controlled by release of hormones

Describe secondary sexual characteristics seen in both males and females

Body hair; sexual organs develop (breasts/penis and testes)

Describe the secondary sexual characteristics exclusively experienced by females

Hips get wider; menstrual cycle begins

Describe the secondary sexual characteristics experienced exclusively by males

Facial hair; muscles develop; voice breaks

Describe the development of sexual organs in males (secondary sexual characteristics)

Growth of penis and testes; testes produce sperm