Chapter 16 - Repro Cyles & Fertilisation

Question 1

Explain the ovarian cycle

Answer 1

• at birth there are about 400000 immature eggs in a female
  1. Eggs in the resting stage are surrounded by a single layer of cells (referred to as a primary follicle)
  2. Some eggs undergo further development - a denser layer of cells form and the egg is forced to the side of the follicle (referred to as a secondary follicle)
  3. In 10-14 days, the follicle becomes known as a mature follicle and moves towards the surface of the ovary.
  When the mature follicle bursts, it expels the egg. A process called ovulation.

Question 2

What is a corpus luteum and corpus albicans?

Answer 2

• The remaining cells of the follicle enlarge and change into a yellow colour called the corpus luteum.
• The hormones that influence the development of the lining of the uterus are secreted by the corpus luteum.
• corpus alibans form when the egg is not fertilised and eventually disappears while another ovarian cycle begins.
• if fertilisation does occur, the corpus luteum continues to form until the placenta can take over its job.
• when the baby stops breastfeeding the ovarian cycles begins again.

Question 3

Explain the menstrual cycle

Answer 3

• menstrual cycle is closely linked with the ovarian cycle
• during primary/secondary follicle development the endometrium becomes softer and thicker.
• after ovulation the endometrium secrets a watery mucus rich in glycogen
• if the egg is not fertilised, the corpus luteum signals the endometrium to stop thickening and begin menstruation.
• when menstruation first begins - menarch
• when menstruation stops - menopause

Question 4

What are endocrine Glands?

Answer 4

• regulate and control the hormones that signal menstrual and ovarian cycles.
• hormones are transported by blood
• hormones only take affect on their target organ (testes and ovaries)

Question 5

What are the 3 types of hormones secreted by the pituritary gland?

Answer 5

Gonadotropins

1. FSH - stimulates the development and maturation of follicles
   - follicles secrete oestrogen
2. LH - promotes final maturation of follicle and corpus luteum
   - corpus luteum secretes progesterone & oestrogen

Lactogenic hormone - prepares and maintains milk production

Question 6

What does HCG stand for and what does it do?

Answer 6

Human Chorionic Gonadotropin

• produced by the placenta
• secretes oestrogen and progesterone

Question 7

What is Oxytocin?

Answer 7

Hormone from the Pituitary
Uterus - stimulates contraction of smooth muscle
Breasts - promotes contraction of muscles cells sounding the nipples

Question 8

What is Oestrogen, Progesterone and Testosterone?

Answer 8

Oestrogen -

• development of female repro system
• secondary sexual characteristics

Progesterone -

• maintenance of of endometrium
• development and maintenance of placenta
• development of milk secreting Glands

Testosterone -

• development of male repro system
• development of secondary sexual characteristics
• sex drive

Question 9

Why is sperm mortality high?

Answer 9

• many sperm die before reaching the egg.
• the corona radiata is held together with acid. The head of sperm contain an enzyme that break down this acid. Lot’s of sperm are needed to break down majority of the acid.

Question 10

What happens after the sperm meets the egg?

Answer 10

• the sperm forms a male pronucleus
• the nucleus of the ebb forms a female pronucleus
• the egg is now referred to as a zygote