Reproductive System - Physiology of menstrual cycle

Question 1

Describe the follicular phase of the ovarian cycle.

Answer 1

Initiation - endometrial lining of uterus sheds
Follicular development - multiple primordial follicles in the ovaries begin to develop under the influence of follicle-stimulating hormone
Eventually, 1 dominant follicle becomes the primary follicle with oocyte in middle

Question 2

Describe ovulation phase of ovarian cycle.

Answer 2

Ovulation is triggered by a surge in luteinizing hormone (LH), which is preceded by a gradual increase in estrogen levels
The surge in LH causes the mature ovarian follicle (Graafian follicle) to undergo final maturation and rupture.
This rupture releases the mature egg (oocyte) from the ovary
The released egg is swept into the fallopian tube (oviduct) by fimbriae
As the follicles continue to mature, they reach a critical threshold level of estrogen production.
This high level of estrogen triggers a positive feedback loop, leading to a sudden surge in luteinizing hormone (LH) secretion from the pituitary gland

Question 3

Describe the luteal phase of the ovarian cycle

Answer 3

It is characterized by the transformation of the ruptured ovarian follicle into the corpus luteum
Corpus luteum - temporary endocrine structure that secretes hormones essential for preparing the uterine lining (endometrium) for potential implantation of a fertilized egg

Question 4

What are female secondary sexual characteristics?

Answer 4

Female secondary sexual characteristics are physical features that develop during puberty as a result of hormonal changes, particularly increased levels of estrogen and progesterone
Development of breasts
Widening of hips
Body fat redistribution
Pubic hair
Growth of labia and vulva
Menstruation

Question 5

What is female gamete formation and male gamete formation called?

Answer 5

Female - oogenesis
Male - spermatogenesis

Question 6

Contrast female and male gamete formation.

Answer 6

Oogenesis regulated by oestrogen but spermatogenesis regulated by testosterone.
Oogenesis has 2 meiotic divisions but spermatogenesis only has 1.
Meiotic division in oogenesis is asymmetrical, with cytokinesis unevenly distributing cytoplasm between the secondary oocyte and polar bodies
Spermatogenesis is symmetrical, resulting in four equal-sized haploid cells
Oogenesis occurs in the ovaries of females.
Spermatogenesis takes place in the testes of males.

Question 7

What is the importance of human reproduction?

Answer 7

Continuation of the species
Biological imperative
Through reproduction, humans perpetuate their genes and pass on their genetic traits to future generations, contributing to the diversity and evolution of the species
Fulfilment of parental instincts

Question 8

What are the 3 phases of the uterine (endometrial) cycle?

Answer 8

Menstruation
Proliferative phase
Secretory phase

Question 9

Describe the menstruation phase.

Answer 9

As the levels of estrogen and progesterone decline, the endometrial lining of the uterus is no longer maintained, and the blood vessels supplying it begin to constrict.
This leads to a decrease in blood flow to the endometrium, causing it to break down and shed.

Question 10

Describe the proliferative phase.

Answer 10

Estrogen promotes the proliferation of endometrial cells and the regeneration of the endometrial lining that was shed during menstruation
The endometrium becomes thicker and more vascularised, preparing to support embryo implantation and pregnancy
Endometrial glands develop within uterus
Ovarian follicles undergo development

Question 11

Describe the secretory phase.

Answer 11

The secretory phase is characterised by the development and function of the corpus luteum, a temporary endocrine structure formed from the remnants of the ruptured ovarian follicle
Progesterone controls secretory phase