B15.4 Sexual reproduction in humans

Label male reproductive system diagram

What is the function of the testes?

• Produces sperm (male gamete) and testosterone (male hormone)

What is the function of the scrotum?

• Sac supporting the testes and covering them, maintains sperm at a temperature slightly lower than the rest of the body

What is the function of the sperm ducts?

• Tube where sperm passes through which connects testes to urethra for ejaculation

What is the function of the prostate gland?

• Produces semen — fluid which provides sperm cells with nutrients

What is the function of the urethra?

• Tube running down center of penis — can carry out semen or urine

What is the function of the penis?

• Passes urine out of the body from the bladder and allows semen to pass into the vagina during intercourse

Label female reproductive system diagram

What is the function of the ovaries?

• Contains egg cells (female gametes) which mature and hormones (oestrogen and testosterone)

What is the function of the oviducts?

• Connects ovary to uterus, lined with ciliated cells to push released ovum down the duct — fertilisation occurs here

What is the function of the uterus?

• Organ with soft lining where fertilised zygote implants in its lining to develop into a fetus during pregnancy

What is the function of the cervix?

• Ring of muscle between vagina and uterus — keeps fetus in place during pregnancy

What is the function of the vagina?

• Muscular canal that leads to inside of woman’s body — male’s penis and newborn can pass through here

What is fertilisation and where does it take place?

• The fusion of the nuclei from a male gamete (sperm cell) and a female gamete (egg cell)

  • Takes place in oviducts

Label parts of male gamete

What are the adaptations of a sperm cell?

• Has flagellum (tail): allows it to swim to the egg cell

• Contains enzyme in acrosome (head region): allows it to digest through the jelly coat and cell membrane of the egg cell when it is in contact with one

• Contains many mitochondria: to provide sperm cell energy from respiration so that the flagellum can move back and forth, which allows it to swim to the egg

Describe the sperm cell in terms of size, structure, motility and numbers

• Size: very small

• Structure: head region and flagellum, has many structural adaptations

• Motility: capable of movement

• Numbers: produced everyday in huge numbers

Label parts of a female gamete

What are the adaptations of an egg cell?

• Has cytoplasm which contains a store of energy: provides energy needed for dividing the zygote after fertilisation

• Has a jelly-like coating which changes after fertilisation: forms an impenetrable barrier after fertilisation to prevent other sperm nuclei from entering

Describe the egg cell in terms of size, structure, motility and numbers

• Size: large

• Structure: round cell covered in jelly coating, has few structural adaptations

• Motility: not capable of movement

• Numbers: many immature eggs in each ovary, only one is released per month

What are the two types of sexual characteristics?

• Primary sexual characteristics: differences in reproductive organs between males and females

• Secondary sexual characteristics: changes — controlled by hormones — that occur during puberty

What are the female secondary sexual characteristics?

• Emotional changes

What are the male secondary sexual characteristics?

• Emotional changes

What is the menstrual cycle?

• A process controlled by hormones that lasts approximately 28 days that prepares the uterus for pregnancy by thickening the endometrium which causes changes in the ovaries

  • Has 4 stages

What are the names of the 4 stages of the menstrual cycle?

1. Menstruation

2. Follicular

3. Ovulation

4. Luteal

Describe the first phase of the menstrual cycle briefly

Stage #1: Menstruation Days 1-5

• Endometrium breaks down and is removed from the body

  • Referred to as a “period”

Describe the second phase of the menstrual cycle briefly

• Stage #2: Follicular Days 6-13

  • Egg matures in ovary

  • Endometrium rebuilds

Describe the third phase of the menstrual cycle briefly

Stage #3: Ovulation Day 14

• Egg is released from ovary

• Egg begins to slowly move towards the uterus via the oviduct

Describe the fourth phase of the menstrual cycle briefly

Stage #4: Luteal phase Days 15-28

• Endometrium maintained

• If no fertilisation then the endometrium breaks down

• If fertilisation occurs then the cycle is broken