1. DJH
Human reproduction
for A2 Biology
Part 1

2. Male reproductive system
Bladder
Pubic bone
Seminal vesicle
Vas deferens
Ejaculatory duct
Prostate gland
Urethra
Cowper’s gland
Erectile tissue
Anus
Spongy tissue
Penis
Epididymis
Glans
Testis
Prepuce
Scrotum

3. Female reproductive system
Vertebra
Oviduct
Ovary
Fimbria
Uterus
Cervix
Bladder
Rectum
Pubic bone
Urethra
Vagina
Clitoris
Labium minorum
Anus
Labium majorum
Vaginal orifice
Perineum

4. Male system memory check
Write down the name and one function for as many of structures 1 to 19 as you can.

5. Female system memory check
Write down the name and one function for as many of structures 1 to 16 as you can.

6. Quick test
Write down the name and one function of each of structures 1 – 11.

7. Quick test
Write down the name and one function of each of structures 1 – 14.

8. Gametogenesis gametes are haploid in humans, n = 23
to produce gametes, diploid (2n) cells in the ovary or testis must divide by meiosis
meiosis consists of two consecutive divisions: the first (reduction division) is the one that separates homologous chromosomes from each other

9. The animation shows mitosis in an animal cell where 2n = 4
A reminder of mitosis
In mitosis,
chromosomes are replicated in interphase (S phase of the cell cycle), to form sister chromatids joined at the centromere
in prophase the replicated chromosomes condense by spiralisation, and become visible in the light microscope
chromosomes line up on the equatorial plane, where spindle fibres attach to the centromeres (metaphase)
the centromeres divide and the sister chromatids are pulled toward opposite poles (anaphase)
the daughter chromosomes re-disperse, nuclear envelopes form around them, and cytokinesis occurs (telophase)
The animation shows mitosis in an animal cell where 2n = 4

10. Meiosis This is telophase II leading into interphase
This is anaphase II
This is metaphase II
This is late anaphase I, leading to telophase I
This is late telophase I, leading to prophase II
This is anaphase I
This is metaphase I
This was the parent cell
At the beginning of prophase I chromosomes condense and become visible, as in mitosis.
As they continue to condense the homologous chromosomes pair up: this never happens in mitosis.
Telophase I usually leads straight into prophase II: the nuclear envelope may or may nor re-form.
The pairs of chromosomes (each called a bivalent) move to the equatorial plane and attach to spindle fibres.
At this point the paired chromosomes are seen to consist of sister chromatids, joined at a centromere.
As the spindle fibres contract the homologous chromosomes are pulled apart.
... and the chromatids are separated by centromere division and spindle contraction
Meiosis II is mechanically identical to mitosis: the separated chromosomes line up on the equatorial plane ...
At telophase II four haploid and genetically different daughter cells have been produced
… and this is how it divides

11. Meiosis: chiasmata and crossing over
During prophase I the chromatids of the paired homologous chromosomes become intricately entwined. At this stage they randomly break and re-join at points called chiasmata.
When they separate at anaphase I, the homologous chromosomes now contain both maternal and paternal portions …
… leading to even greater genetic variation in the daughter cells (gametes).
Chiasmata

12. Meiosis: how much have you understood?
These diagrams show four stages in meiosis prophase I.
What is the diploid number of this cell?
Put the diagrams into the correct order.

13. Meiosis: how much have you understood?
These diagrams show stages in meiosis.
Which division of meiosis is shown?
How would the diagrams differ if they showed the equivalent stages of division II?

14. Meiosis: how much have you understood?
Done. If you got the sequence wrong, click the return arrow to try again. Otherwise, click the forward arrow to move on.
These ten photographs show stages in meiosis in sea urchins. Put them into the correct order and identify each stage as precisely as you can. Each mouse click will move you on one step.

15. What happens next?

16. What happens next?

17. Outcomes of meiosis Four haploid daughter cells …
which are genetically different due to …
independent assortment of maternal and paternal chromosomes at metaphase/anaphase I …
and chiasma formation and crossing over during prophase I

18. Spermatogenesis
Spermatogenesis takes place in the wall of the seminiferous tubules of the testes.

19. Spermatogenesis
A single seminiferous tubule

20. Stages in spermatogenesis
Late spermatids 5 1
Spermatogonia
Secondary spermatocytes 3
Primary spermatocytes undergoing meiosis 1 2
Early spermatid 4

21. Sertoli cells
Spermiogenesis
Meiosis II
Meiosis I
Mitosis
The cells undergoing spermatogenesis are embedded in and protected by Sertoli cells (nurse cells).

22. Leydig cells (interstitial cells)
Leydig cells are found in the spaces between seminiferous tubules: they secrete testosterone and other androgens.

23. Oogenesis Objectives:
* To be able to outline gametogenesis in the human male and female
**To be able to explain the role of hormones in maintenance of the human menstrual cycle and link this to changes in the ovary and uterus during the Cycle

24. Oogenesis
Oogenesis starts in the foetal ovaries and continues from 5 to 25 weeks of foetal life.
At birth the ovaries contain about primary oocytes, all arrested in prophase of meiosis I.
At puberty, about primary oocytes remain in the ovaries. In each menstrual cycle one or two of these are stimulated to complete meiosis I: the division is unequal, forming a secondary oocyte and a small polar body.
The secondary oocyte starts meiosis II, but halts at metaphase. Meiosis II is completed only after fertilisation, forming a second polar body and an ovum.

25. Comparison of spermatogenesis and oogenesis
Starts during foetal life: suspended until puberty
Starts at puberty
Re-starts at menarche: completed during menstrual cycles by only a small percentage of primary oocytes
Continuous from puberty into old age
Four functional gametes produced from every primary spermatocyte
Only one functional gamete produced from every primary oocyte

26. Oogenesis in the ovary
In the foetal ovary diploid oogonia are produced by mitosis
Some of these divide by mitosis to produce primary oocytes, which start meiosis I
As they do so, some of the cells around them form a covering layer called a primordial follicle
During childhood some of the primordial follicles develop into primary follicles, in which the cells surrounding the oocyte form several layers called granulosa cells.
Cells around the granulosa cells form an additional layer around the follicle called the theca.
The granulosa cells themselves secrete a protective glycoprotein layer around the primary oocyte called the zona pellucida.

27. Oogenesis in the ovary
Hormones secreted at puberty stimulate primary follicles to develop into secondary follicles: the primary oocyte (still stuck in prophase of meiosis I) grows in size, and a fluid-filled space develops in the follicle.
During each menstrual cycle one (usually) secondary follicle is stimulated by the hormone FSH to develop into a Graafian follicle: in the Graafian follicle the primary oocyte completes meiosis I, forming a small first polar body and a secondary oocyte, which is expelled in ovulation

28. The menstrual cycle
Pituitary secretes FSH; this triggers follicle development.
Granulosa cells secrete oestrogens.
Oestrogens stimulate repair of endometrium …
… and secretion of LH by pituitary.
LH triggers ovulation …
… and development of remaining follicles cells into corpus luteum.
Corpus luteum secretes progesterone …
…which stimulates vascularisation of endometrium and inhibits FSH secretion
Corpus luteum degenerates, progesterone level falls; endometrium breaks down, FSH secretion re-starts, a new cycle begins

29. The ovarian cycle Secretory (luteal) phase: days 14-28
Follicular phase: days 1-14
Ovulation: around day 14

30. The uterine cycle
In the menstrual phase the endometrium breaks down as the corpus luteum degenerates and progesterone secretion fails.
In the follicular (proliferative) phase the endometrium is repaired and thickened under the influence of FSH.
In the secretory phase the endometrium becomes vascular and spongy under the influence of progesterone.

31. How well have you understood the menstrual cycle?
What is this? How does it get here?
What has caused this development?
What are these?
What is this? What does it produce?
What triggers this event?
What is breaking down here? Why?
What has caused this repair? Where was it made?
What has caused this change? Where was it made?

32. End of Part 1
Fertilisation, implantation, pregnancy, birth and lactation are covered in Part 2