Chapter 15 Reproduction

Question 1

What is sexual reproduction?

Answer 1

It is the fusion of the nuclei of a female and male gamete to form a zygote.

Question 2

Characteristic of the OVUM

Answer 2

0.12-0.15mm in diameter
Smallest cell in the body
Abundant cytoplasm

Question 3

Characteristic of the SPERM

Answer 3

Large nucleus containing 23 chromosomes (H)
Acrosome (Sac containing enzymes that breaks down membrane of ovum during fertilisation to allow sperms to penetrate ovum.) (H)
Numerous mitochondria providing energy to swim(M)
Beating movement enables sperm to swim to ovum (T)
Tail = Flagellum

Question 4

Days 1-5 of Menstruation

Answer 4

The endometrium breaks down from uterus wall, damaging many blood capillaries and paases out through the vagina tgt with the unfertilised ovum. (MENSTRUATION) occurs about 2 weeks after ovulation.

Question 5

Days 6-16 of Menstruation

Answer 5

Walls of the uterus grow and repair the endometrium containing many capillaries. The endometrium continues to thicken until about Day 16, and thereafter from Day 17, thickness is maintained until end of the cycle (Day 28).

Question 6

Day 14 of Menstruation

Answer 6

When the endometrium is ready, ovulation occurs. Ovum passes thru fallopian tube.

Question 7

if egg fertilised

Answer 7

If egg is fertilized, the embryo formed is then implanted in the endometrium and grows in the uterus. The ovaries then stop releasing ova more until the baby in born. If ovum is not fertilised, menstruation occurs and the ovum breaks down, passing out of the system during menstruation.

Question 8

AFTER MENSTRUATION:

Answer 8

Concentration of oestrogen in blood increases to repair the uterine lining and allows it to grow.
Later on, the concentration decreases. (After Ovulation) Concentration of progesterone in the blood increases to help maintain the thickened uterine lining, preparing the uterus for implantation of the embryo, if any. (At this time, concentration of oestrogen increases a little too)

Question 9

what affects the menstrual cycle?

Answer 9

Stress, Emotional Disturbances, Mental Fatigue, illness
Unbalanced diet or malnutrition may cause the periods to become irregular or stop completely

Question 10

natural method of birth control

Answer 10

involves limiting having sexual intercourse only during the times in menstrual cycle where fertilisation is less likely to occur. however, this method may not be reliable as not all healthy females have regular and predictable periods.

Question 11

chemical method of birth control

Answer 11

spermicide- applied onto the vagina to kill sperms before sexual intercourse

Question 12

temporary methods of birth control (prevent fertilisation) condom and diaphragm
pill

Answer 12

condom- sheath placed over penis before sexual intercourse to trap sperms
diaphragm- fits over cervix of uterus to prevent entry of sperms. usually used with spermicide
pill- contains a hormone which if taken regularly, will prevent ovulation

Question 13

prevents implantation

Answer 13

intra-uterine device (IUD) fitted inside of the uterus

Question 14

surgical methods

Answer 14

vasectomy- involves cutting and tying of sperm ducts
tubal ligation- involves cutting and tying of oviducts