1. REPRODUCTION
AHL Topic 11.4
IB Biology
Miss Werba

2. AHL TOPIC 11 – FURTHER PHYSIOLOGY
11.1 DEFENCE AGAINST INFECTIOUS DISEASE
11.2
MUSCLES & MOVEMENT
11.3
THE KIDNEY
11.4
REPRODUCTION
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3. THINGS TO COVER PRODUCTION OF GAMETES
Structure & function of testis tissue
Process of spermatogenesis
Roles of hormones in spermatogenesis
Structure & function of ovarian tissue
Process of oogenesis
Diagrams of a mature egg & sperm
Role of male accessory reproductive structures
Comparison of spermatogenesis & oogenesis
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4. THINGS TO COVER FERTILISATION & PREGNANCY Process of fertilisation
Role of HCG in pregnancy
Development of early embryo
Structure & function of the placenta
Structure & function of the amniotic sac & fluid
Materials exchanged between maternal & foetal blood
Process of birth
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5. TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE
11.4.1
TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE
Produce sperm by a process called spermatogenesis
Produce the hormone testosterone
The testis consists of many seminiferous (SN) tubules.
Interstitial (Leydig) cells and blood capillaries lie between the SN tubules
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6. TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE
11.4.1
TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE
EPIDIDYMISA
TESTISB
SEMINIFEROUS TUBULEC
INTERSTITIUMD
VAS DEFERENSE E A D C B
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7. TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE
11.4.1
TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE
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8. TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE
11.4.1
TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE
SEMINIFEROUS TUBULEC
BASEMENT MEMBRANEG
SERTOLI CELLSH
GERMINAL EPITHELIUM CELLSI
SPERMATOZOAJ
LUMEN OF SN TUBULEK
LEYDIG CELLSL C G H I J K L
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9. TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE
11.4.1
TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE
Leydig (interstitial cells):
produce testosterone
germinal epithelium cells:
origin of spermatogonia
spermatozoa:
developing sperm cells
Sertoli cells:
nourish developing spermatozoa
Spermatozoa will eventually leave the SN tubule via the lumen.
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10. SPERMATOGENESIS Command term = OUTLINE
11.4.2
SPERMATOGENESIS Command term = OUTLINE
1) Mitosis: germ cells (or spermatogonia (2n)) divide to produce more spermatogonia (2n). 2) Growth: spermatogonia grow larger becoming primary spermatocytes (2n) 3) Meiosis I: primary spermatocytes undergo Meiosis I producing two secondary spermatocytes (n) 10
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11. SPERMATOGENESIS Command term = OUTLINE
11.4.2
SPERMATOGENESIS Command term = OUTLINE
4) Meiosis II: secondary spermatocytes undergo Meiosis II producing two spermatids (n) per cell. 5) Development & cell differentiation: spermatids associate with Sertoli cells, developing into spermatozoa (n) 6) Detachment: sperm detach and are carried out of the testis by the fluid in the centre of the seminiferous tubule 11
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12. SPERMATOGENESIS Command term = OUTLINE
11.4.2
SPERMATOGENESIS Command term = OUTLINE P P
BASEMENT MEMBRANEJ SERTOLI CELLSO SPERMATOGONIUMK PRIMARY SPERMATOCYTEL SECONDARY SPERMATOCYTEM SPERMATIDN SPERMATOZOANP P P P O N N N O N N N N N N M M M M L M L L L K K K K K O O J 12
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13. SPERMATOGENESIS Command term = OUTLINE
11.4.2
SPERMATOGENESIS Command term = OUTLINE 13
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14. SPERMATOGENESIS Command term = OUTLINE
11.4.2
SPERMATOGENESIS Command term = OUTLINE 2n n n n 2n n n n
Ref: 14
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15. HORMONES IN SPERMATOGENESIS Command term = STATE
11.4.3
HORMONES IN SPERMATOGENESIS Command term = STATE
3 hormones are involved in spermatogenesis:
FSH LH
testosterone
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16. HORMONES IN SPERMATOGENESIS Command term = STATE
11.4.3
HORMONES IN SPERMATOGENESIS Command term = STATE
FSH
Produced in the pituitary gland
Stimulates division & maturation of Sertoli cells
Stimulates sperm production in SN tubules LH
Stimulates Leydig cells to produce testosterone
Testosterone
Produced in the Leydig cells in the testis
Promotes spermiogenesis (maturation of spermatids into spermatozoa)
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17. SPERM STRUCTURE Command term = DRAW and LABEL
11.4.6
SPERM STRUCTURE Command term = DRAW and LABEL
NUCLEUS
ACROSOME
MITOCHONDRIA
HEAD
MIDPIECE
TAIL
contains the nucleus and acrosome, which carries enzymes necessary to penetrate the egg
contains many mitochondria to generate energy for swimming
propels the sperm as it swims towards the egg
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18. SEMEN PRODUCTION Command term = OUTLINE
11.4.7
SEMEN PRODUCTION Command term = OUTLINE
3 structures are involved in the production of semen :
epididymis
seminal vesicle
prostate gland
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19. SEMEN PRODUCTION Command term = OUTLINE
11.4.7
SEMEN PRODUCTION Command term = OUTLINE
EPIDIDYMIS
sperm arrive here unable to swim.
sperm mature in the epididymis
sperm develop motility (learn to swim)
SEMINAL VESICLES
Produce mucus to protect the sperm in the vagina.
produces fluid which contains nutrients for the sperm (fructose).
PROSTATE GLAND
produces most of the seminal fluid
produces fluid which contains mineral nutrients.
produces alkaline fluid to protect sperm in the acidic conditions of the vagina
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20. 11.4
SPERMATOGENESIS 20
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21. OVARY STRUCTURE AND FUNCTION Command term = ANNOTATE
11.4.4
OVARY STRUCTURE AND FUNCTION Command term = ANNOTATE
The ovaries contain follicles in different stages of development.
The follicles contain the developing oocytes.
The germinal epithelium keeps the tissues of the organ together and separates them from the rest of the body.
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22. OVARY STRUCTURE AND FUNCTION Command term = ANNOTATE
11.4.4
OVARY STRUCTURE AND FUNCTION Command term = ANNOTATE
FALLOPIAN TUBEA
OVARYB
GERMINAL EPITHELIUMC
PRIMARY OOCYTE D IN PRIMARY FOLLICLE D1
SECONDARY OOCYTE E IN GRAAFIAN FOLLICLEE1
OVULATIONF
RUPTURED FOLLICLEG
OVUMH
CORPUS LUTEUMI A D D1 B C E1 E H F G
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23. OVARY STRUCTURE AND FUNCTION Command term = ANNOTATE
11.4.4
OVARY STRUCTURE AND FUNCTION Command term = ANNOTATE
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24. OVARY STRUCTURE AND FUNCTION Command term = ANNOTATE
11.4.4
OVARY STRUCTURE AND FUNCTION Command term = ANNOTATE
germinal epithelium cells:
outer layer
produces primary follicles through cell division
primary follicles:
Location for development of oocyte
Surrounded by support cells
mature follicle:
contain oocyte, ready for ovulation
secondary oocyte:
haploid gamete
Ovum held in state of suspended meiosis until after fertilisation
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25. OOGENESIS Command term = OUTLINE
1) Mitosis: (in foetal ovaries) germ cells called oogonia (2n) form more oogonia (2n) 2) Growth: oogonia grow larger becoming primary oocytes (2n) 3) Meiosis I: primary oocytes begin Meiosis I but stop in Prophase I. The primary oocyte and a single layer of follicle cells form the primary follicle.
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26. OOGENESIS Command term = OUTLINE
11.4.5
OOGENESIS Command term = OUTLINE
When a baby girl is born, her ovaries contain at least 400,000 primary follicles.
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27. OOGENESIS Command term = OUTLINE
4 Meiosis I continues: every menstrual cycle, a few primary follicles start to develop. The primary oocyte completes Meiosis I, forming two haploid nuclei. 5) Unequal division: the cytoplasm of the primary oocyte divides unequally forming a large secondary oocyte (n) and a small polar body
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28. OOGENESIS Command term = OUTLINE
6) Meiosis II: The secondary oocyte begins Meiosis II but stops in Prophase II. The follicle cells meanwhile are proliferating and follicular fluid is forming.
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29. OOGENESIS Command term = OUTLINE
11.4.5
OOGENESIS Command term = OUTLINE
When the mature follicle is released during ovulation, the egg is actually still a secondary oocyte.
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30. OOGENESIS Command term = OUTLINE
11.4.5
OOGENESIS Command term = OUTLINE 30
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31. OOGENESIS Command term = OUTLINE
7) Meiosis II continues: After fertilisation, the secondary oocyte completes Meiosis II to form an ovum.
The ovum already has a sperm nucleus inside it and a second polar body.
The first and second bodies do not develop and eventually degenerate.
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32. OOGENESIS Command term = OUTLINE
11.4.5
OOGENESIS Command term = OUTLINE 32
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33. OOGENESIS Command term = OUTLINE
11.4.5
OOGENESIS Command term = OUTLINE 2n 2n n n
Ref: 33
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34. 11.4
OOGENESIS 34
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35. OVUM STRUCTURE Command term = DRAW and LABEL
11.4.6
OVUM STRUCTURE Command term = DRAW and LABEL
CORONA RADIATA
layer of follicle cells which nourish egg
NUCLEUS
ZONA PELLUCIDA
layer of gel (glycoproteins)
CYTOPLASM (yolk)
contains nucleus, fat droplets, cortical granules, etc
PLASMA MEMBRANE
FIRST POLAR BODY
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36. OVUM STRUCTURE Command term = DRAW and LABEL
11.4.6
OVUM STRUCTURE Command term = DRAW and LABEL
NUCLEUS
CYTOPLASM (yolk)
FIRST POLAR BODY
PLASMA MEMBRANE
CORONA RADIATA
ZONA PELLUCIDA
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37. SPERMATOGENESIS & OOGENESIS Command term = COMPARE
11.4.8
SPERMATOGENESIS & OOGENESIS Command term = COMPARE
Similarities:
Both produce haploid gametes by meiosis
Both take place in the gonads
Both start during puberty
Both are controlled by hormones
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38. SPERMATOGENESIS & OOGENESIS Command term = COMPARE
11.4.8
SPERMATOGENESIS & OOGENESIS Command term = COMPARE
Differences:
Spermatogenesis
Oogenesis
Total no. of gametes
Large number of sperm cells
Limited number of ova
Gametes produced per germ cell 4 1
Time of formation (from puberty)
Continuously
Once a month
Release of gametes
Any time
Monthly cycle
Until when
Does not stop
Stops at menopause
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39. SPERMATOGENESIS & OOGENESIS Command term = COMPARE
11.4.8
SPERMATOGENESIS & OOGENESIS Command term = COMPARE
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40. PROCESS OF FERTILISATION Command term = DESCRIBE
11.4.9
PROCESS OF FERTILISATION Command term = DESCRIBE
The sperm are deposited into the vagina after sexual intercourse.
The sperm travel through the uterus to the fallopian tubes.
Fertilisation can occur here, and the fertilised ovum then makes its way to the endometrium to implant.
There are a number of steps that occur during fertilisation of a sperm and egg:
ACROSOME REACTION
PENETRATION OF EGG BY THE SPERM
CORTICAL REACTION
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41. PROCESS OF FERTILISATION Command term = DESCRIBE
11.4.9
PROCESS OF FERTILISATION Command term = DESCRIBE
Remember, at the moment of ovulation, the secondary oocyte is surrounded by the zona pellucida and a corona radiata:
Corona radiata:
The layer of follicle cells surrounding the zona pellucida
Zona Pellucida:
the membrane surrounding the secondary oocyte of mammals, which is secreted by the ovarian follicle cells
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42. PROCESS OF FERTILISATION Command term = DESCRIBE
11.4.9
PROCESS OF FERTILISATION Command term = DESCRIBE
ACROSOME REACTION:
Sperm reaches the corona radiata and moves through the cells
The acrosome fuses with the zona pellucida
Acrosome releases proteolytic enzymes and digests the gel
Proteolytic = ?????
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43. PROCESS OF FERTILISATION Command term = DESCRIBE
11.4.9
PROCESS OF FERTILISATION Command term = DESCRIBE
PENETRATION OF EGG BY THE SPERM:
The sperm then reaches the egg membrane
The egg membrane has special receptors to bind the sperm cell
The head of the sperm fuses with the membrane of the secondary oocyte.
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44. PROCESS OF FERTILISATION Command term = DESCRIBE
11.4.9
PROCESS OF FERTILISATION Command term = DESCRIBE
CORTICAL REACTION:
The cortical granules (lysosomes) release enzymes
The zona pellucida thickens and the sperm-binding proteins are destroyed.
This forms the “fertilisation envelope”
Once formed, the envelope cannot be penetrated by other sperm cells.
Now, the nucleus of the secondary oocyte completes meiosis II and then the egg and sperm nuclei fuse to form a diploid zygote.
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45. PROCESS OF FERTILISATION Command term = DESCRIBE
11.4.9
PROCESS OF FERTILISATION Command term = DESCRIBE
acrosome of sperm reaches zona pellucida
ACROSOME REACTION
enzymes released from acrosome digest the zona pellucida
the membranes of the sperm and egg fuse
CORTICAL REACTION
enzymes from cortical granules fuse with egg plasma membrane. This thickens zona pellucida and destroys sperm-binding proteins.
FERTILISATION ENVELOPE FORMED
no more sperm can penetrate egg
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46. PROCESS OF FERTILISATION Command term = DESCRIBE
11.4.9
PROCESS OF FERTILISATION Command term = DESCRIBE
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47. PROCESS OF FERTILISATION Command term = DESCRIBE
11.4.9
PROCESS OF FERTILISATION Command term = DESCRIBE
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48. PROCESS OF FERTILISATION Command term = DESCRIBE
11.4.9
PROCESS OF FERTILISATION Command term = DESCRIBE
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49. PROCESS OF FERTILISATION Command term = DESCRIBE
11.4.9
PROCESS OF FERTILISATION Command term = DESCRIBE
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50. EARLY EMBRYO DEVELOPMENT Command term = OUTLINE
EARLY EMBRYO DEVELOPMENT Command term = OUTLINE
After fertilisation, the zygote undergoes several mitotic divisions.
These are cleavage divisions as they are not followed by cell growth.
Several cleavage divisions occur, which leads to the formation of the morula, a solid ball of cells.
The morula reaches the uterus about four days after fertilisation.
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51. EARLY EMBRYO DEVELOPMENT Command term = OUTLINE
EARLY EMBRYO DEVELOPMENT Command term = OUTLINE
After this, unequal divisions cause a fluid-filled cavity to form in the middle.
This makes a blastocyst (at around 5 days).
The blastocyst consists of:
an inner mass of cells ( the embryo)
an outer layer called the trophoblast ( the placenta)
a fluid filled cavity
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52. EARLY EMBRYO DEVELOPMENT Command term = OUTLINE
EARLY EMBRYO DEVELOPMENT Command term = OUTLINE
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53. ROLE OF HCG IN EARLY PREGNANCY Command term = OUTLINE
ROLE OF HCG IN EARLY PREGNANCY Command term = OUTLINE
If fertilisation has occurred, it will take approximately 8 days for the blastocyst to embed itself into the endometrium.
After implantation, the trophoblast of the embryo starts to secrete the hormone HCG (= human chorionic gonadotrophin).
By the mid-pregnancy, the corpus luteum starts to degenerate, but the cells in the placenta have started to secrete oestrogen and progesterone by this stage.
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54. ROLE OF HCG IN EARLY PREGNANCY Command term = OUTLINE
ROLE OF HCG IN EARLY PREGNANCY Command term = OUTLINE
HCG concentration continues to rise for 8-10 weeks.
HCG stimulates the corpus luteum to grow and continue secreting oestrogen and progesterone.
Progesterone and oestrogen inhibit FSH and LH – so no more eggs are released.
Progesterone maintains the endometrium.
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55. ROLE OF HCG IN EARLY PREGNANCY Command term = OUTLINE
ROLE OF HCG IN EARLY PREGNANCY Command term = OUTLINE
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56. PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE
PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE
The placenta is a disc-shaped structure that nourishes the developing embryo.
It is formed from the developing trophoblast upon implantation.
The trophoblast invades the uterine wall.
The umbilical cord connects the foetus to the placenta.
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57. PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE
PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE
The placenta has a rich blood supply: facilitating the exchange of materials between the maternal blood and foetal capillaries.
The placenta has few, thin membranes: providing a short diffusion distance for materials.
The placenta has villi: increases surface area for exchange.
The placenta has a large TSA and many Rough ERs and vesicles: able to make and secrete HCG, oestrogen and progesterone.
The placenta secretes anti-immune substances: avoids attack by immune system.
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58. PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE
PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE
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59. PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE
PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE
The placenta takes over the hormonal role of the ovary (at ~12 weeks)
It releases progesterone and oestrogen:
Oestrogen stimulates growth of the muscles of the uterus (myometrium) and the development of the mammary glands.
Progesterone maintains the endometrium, as well as reduces uterine contractions and maternal immune response (no antibodies against foetus).
Both oestrogen and progesterone levels drop near time of birth.
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60. THE AMNIOTIC SAC & AMNIOTIC FLUID Command term = STATE
THE AMNIOTIC SAC & AMNIOTIC FLUID Command term = STATE
The foetus is supported and protected by the amniotic sac and amniotic fluid.
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61. THE AMNIOTIC SAC & AMNIOTIC FLUID Command term = STATE
THE AMNIOTIC SAC & AMNIOTIC FLUID Command term = STATE
The foetus is supported and protected by the amniotic sac and amniotic fluid.
The amniotic sac protects the foetus against infections.
The amniotic fluid absorbs shocks and allows the foetal skeleton to develop without the added strain of gravity.
Babies also drink amniotic fluid & urinate in it. It is therefore constantly filtered by the mother.
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62. EXCHANGE ACROSS THE PLACENTA Command term = STATE
EXCHANGE ACROSS THE PLACENTA Command term = STATE
Materials are exchanged between the maternal and foetal blood in the placenta.
The placenta is foetal tissue which invades maternal uterine tissue.
An exchange of materials takes place by diffusion:
the foetal blood becomes enriched with nutrients and oxygen
the maternal blood takes up the waste products from the foetus, which will then be excreted.
NB. materials are exchanged but the blood doesn’t mix!
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63. EXCHANGE ACROSS THE PLACENTA Command term = STATE
EXCHANGE ACROSS THE PLACENTA Command term = STATE
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64. THE BIRTHING PROCESS Command term = STATE
THE BIRTHING PROCESS Command term = STATE
It normally takes 38 weeks after conception for the foetus to be ready to be born.
Progesterone levels will drop so that the uterus can have coordinated muscle contractions.
The foetal head engages in the cervix.
Stretch receptors in the uterus and cervix report the pressure to the brain and the pituitary gland releases oxytocin.
Oxytocin initiates contractions in the myometrium. The contractions become longer & stronger.
This creates a positive feedback loop and results in increasing the strength and duration of the contractions.
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65. THE BIRTHING PROCESS Command term = OUTLINE
THE BIRTHING PROCESS Command term = OUTLINE
The cervix will dilate throughout this process.
When the cervix is fully dilated, labour is over and the second stage (expulsion) begins.
The child is born through the vagina. This stage usually takes no more than one hour.
When the uterus is no longer pushing against something, the positive feedback loop is broken and contractions soon reduce.
However, a few contractions are needed to expel the placenta from the uterine wall. This is the last stage of birth.
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66. THE BIRTHING PROCESS Command term = OUTLINE
THE BIRTHING PROCESS Command term = OUTLINE
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67. Sample questions
Q1. Which of the cells labelled in the diagram below provides nourishment for developing sperm cells?
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68. Sample questions
Q2. Which pair of statements best describes oogenesis and spermatogenesis?
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69. Sample questions
A1. C
A2. D
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70. Sample questions
Q3. Explain the function and structure of the placenta. [8]
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71. Sample questions
A3.
transfer of foods/nutrients/glucose from mother to foetus; foetal gas exchange/transfer of oxygen from mother to foetus; transfer of excretory products/CO2 from foetus to mother; transfer of antibodies/hormones from mother to foetus; secretion of oestrogen/progesterone; from approximately 12 weeks / when ovary/corpus luteum stops secretion; disc shaped structure; connected to the foetus by an umbilical cord; embryonic tissue invades/grows into the uterine wall; placental villi increase the surface area (for exchange); foetal capillaries in placenta/placental villi; inter-villous spaces/sinuses through which mother’s blood flows; small distance between foetal and mother’s blood/narrow placental barrier; Allow reference to embryo instead of foetus throughout. 8 max
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