Unit 15 Human Reproduction

- What are the testes?

Male sex organs

- Function of testes

To produce male gametes/spermatozoa, Production of testosterone

- Where are the testes located?

Scrotum

- Why does the scrotum hang outside the body?

To keep the testes at a lower temperature (cooler than 37*C) so the sperms can develop properly.

- Where are the sperm cells stored?

In small tubules just outside the testes

- Function of Prostate gland?

To secrete fluids in which the sperm cells can swim

- Function of prostate?

Prostate secretes mucus and other glands secrete sugars which sperm cells use as a source of energy for their respiration.

- How is semen formed?

Sperm cells and fluid

- Structure of Sperm cells?

has a flegellum (tail) that lashes side to side adapted for swimming, Small, Has very little energy store- uses sugar in seminal fluid for respiration, No. of chromosomes- 23 (haploid), Millions produced constantly throughout life, Has mitochondria which releases energy to swim

- Why is the egg large?

It provides the food store that supports the embryo after fertilisation

- What are gametes that contain half the number of chromosomes called?

haploid cells

- What are body cells that have the normal number of chromosomes called?

Diploid cells

- How is the egg fertilised by the sperm?

The cell membrane of sperm cell fuses with the cell membrane of the egg cell. The sperm nucleus moves through the cytoplasm of the egg and the two nuclei fuse together to form a zygote (fertilised egg)

- Structure of egg cells?

Large, Has protein and fat in cytoplasm, enough till implantation occurs, no. of chromosomes- 23 (haploid), Produced once a month after puberty till menopause (with the exception of during pregnancy or taking contraceptive pill)

- What hormones do the ovaries make?

Oestrogen, Progesterone

- What is the role of Oestrogen?

Stimulates development of sex organs and sexual characteristic's

- What is the role of Progesterone?

Prepares Uterus so it is ready to receive an embryo

- When and how is the egg released?

An egg is released from the ovary every 28 days, the egg passes out of the ovary into funnel shaped opening's of the oviduct. This is called ovulation. The egg moves down the oviduct to the womb.

- What is the outer opening of the vagina called?

vulva

- What occurs in the oviduct?

Fertilisation

- What occurs in the uterus?

embryo and fetus development

- What is the cervix?

Ring of muscle that separates the uterus from the vagina

- What happens to the embryo when fertilised?

Attaches itself to the lining of the embryo where it develops into fetus

- How does ejaculation occur?

It occurs when the seminal fluid moves into the vagina, at this time a man will also experience an orgasm.

- How does an orgasm occur in women?

Repeated movement of an erect penis against the clitoris or vagina walls

- How many sperm cells does each ejaculation contain?

Contains 2 to 5cm3 of semen with up to 500 million sperm cells

- How does the sperm cell reach the egg cell?

The sperm swims from the vagina to the oviduct

- What is the oviduct?

Muscular tube that links the ovary to the uterus

- What happens immediately after fusion of sperm and egg cell?

The nucleus of the sperm cell enters the egg cytoplasm, leaving it's tail behind, The sperm nucleus fuses with the egg nucleus forming a zygote, The zygote is a diploid as it has 46 chromosomes (one from mother and one from father), The jelly coat changes and stops other sperm cells from entering so only one sperm can fertilise the egg.

- How long can a sperm survive for?

2-3 days

- Where does fertilisation take place?

Oviduct

- What occurs after the fertilised egg begins to divide?

It divides into many cells, the cell division becomes less regular. After a few hours, the embryo becomes a hollow ball of cells that moves down the oviduct.

- What makes the fertilised egg move down the oviduct?

Peristaltic contractions of oviduct move it down, beating of ciliated epithilial cells lining of oviduct

- What is implantation?

Embryo embedding into soft lining of uterus

- What happens to the uterus after implantation?

It has thickened in preparation, contains numerous blood vessels that gives nutrients and oxygen to the embryo via diffusion

- What is the gestation period?

Period of time between fertilisation and birth

- What happens to the embryo after it has been implanted?

grows projections into the lining of the uterus to gain nutrients and oxygen for it's growth, The projections grow into the placenta, The umbilical cord grows

- What is the Placenta?

Site of exchange for oxygen and nutrients for co2 and other waste products, diffuses between fetal and maternal blood, Acts as a barrier for most toxins and pathogens

- Describe the features of the placenta?

Like lungs- large surface area and short distance for diffusion

- Describe the function of the Umbilical cord?

Attaches the fetus to the placenta, Contains artery that transports deoxygenated blood from the fetus to the placenta, Vein that returns oxygenated blood to the fetus

- Describe the function of amniotic sac

Makes amniotic fluid that surrounds and protects the fetus against mechanical damage

- What does the embryo look like one month after fertilisation?

Size of tadpole, no arms or legs, heart beat started

- What does the embryo look like two months after fertilisation?

Has face, limbs and fingers, Most organs formed, Now known as fetus

- What does the fetus look like three months after fertilisation?

Rapid development of muscles and nerves

- What does the fetus look like five months after fertilisation?

180mm in length, Fully formed eyebrows, nails, fingerprint, body hair

- What does the fetus look like seven months after fertilisation?

Development is almost complete

- What all does the fetus take and give the mother?

Takes glucose, amino acids, fats, mineral ions, vitamins, water. Produces urea which diffuses into the mothers blood then excreted by her kidneys.

- Where does the brain start to make hormones that stimulate the testes and ovaries

Pituitary Gland

- What is the male hormone called?

testosterone

- What does the testosterone stimulate?

Growth of male sex organs, Testes that make sperm cells, Hair growth on face, Deepening of voice, Development of muscles in the body

- What is the female hormone called?

Oestrogen

- What does the Oestrogen stimulate?

Growth of female sex organs, Start of menstrual cycle (period), Hair growth on body, Growth and development of breasts, Widening of the hips

- What occurs in the female body during menstruation?

Breakage of uterus lining causing blood and cells to pass out of the vagina

- How are follicles formed?

Potential eggs surrounded by a group of cells

- What happens during ovulation?

The egg is released, the uterus lining which has blood vessels and glands eventually thickens

- What happens to the egg if fertilisation does not occur?

The egg dies and passes out of the vagina, the yellow body in the uterus breaks down, the thick lining of the uterus breaks down.

- What happens to the egg if pregnancy occurs?

Release of hormones that stimulates uterus lining which thickens. The thickened lining supports the uterus giving it food and water.

- What hormone does the pituitary gland secrete?

Follicle stimulating hormone (FSH), Luteinising hormone (LH)

- What hormone does the ovary secrete?

Oestrogen, Progesterone

- What does the FSH do?

This hormone is carried in to the blood to the ovary where it stimulates development of follicles, it has potential to grow into an egg

- How does the cell divide?

Meiosis

- What are the effects of Oestrogen?

Stimulates the repair and thickening of uterus lining, Stops secretion of FSH from pituitary gland, Stimulates pituitary gland to release LH

- What is STI?

Disease transmitted via body fluids through sexual contact

- Give examples of STI

HIV, Syphilis, Gonorrhea

- What does HIV attack?

HIV attacks T-lymphocyte that coordinates the immune system. The T-lymphocytes stimulate other lymphocytes to produce antibodies After HIV attacks T-lymphocytes, it reduces the number of t-lymphocytes produced, so it weakens the body's ability to defend itself against all infections.

- How is HIV Transmitted?

* In the blood and semen, Unprotected sexual intercourse, Hypodermic needles contaminated with infected blood, Passage from mother's blood to fetus, Passage from Breastmilk, Blood used for transfusions

- What is the full form of aids?

Acquired Immunodeficiency syndrome

- What is AIDS?

A collection of diseases brought on by the weakening of the immune system

- early Symptoms of HIV?

flu, swollen glands, high fever

- Symptoms of AIDS?

weight loss, fever, fatigue, diarrhoea

- How can HIV be prevented?

Antiretroviral treatment- prevents replication of virus in host cells, Set up of free needle exchange schemes, Screening donated blood for HIV antibodies and eliminating contaminated blood being used for transmission, Education programmes to build awareness