REPRODUCTION AHL Topic 11.4 IB Biology Miss Werba

AHL TOPIC 11 – FURTHER PHYSIOLOGY 11.1 DEFENCE AGAINST INFECTIOUS DISEASE 11.2 MUSCLES & MOVEMENT 11.3 THE KIDNEY 11.4 REPRODUCTION J WERBA – IB BIOLOGY 2

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 J WERBA – IB BIOLOGY 3

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 J WERBA – IB BIOLOGY 4

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 J WERBA – IB BIOLOGY 5

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 J WERBA – IB BIOLOGY 6

TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE 11.4.1 TESTIS STRUCTURE AND FUNCTION Command term = ANNOTATE J WERBA – IB BIOLOGY 7

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 J WERBA – IB BIOLOGY 8

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. J WERBA – IB BIOLOGY 9

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 J WERBA – IB BIOLOGY 10

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 J WERBA – IB BIOLOGY 11

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 J WERBA – IB BIOLOGY 12

SPERMATOGENESIS Command term = OUTLINE 11.4.2 SPERMATOGENESIS Command term = OUTLINE 13 J WERBA – IB BIOLOGY 13

SPERMATOGENESIS Command term = OUTLINE 11.4.2 SPERMATOGENESIS Command term = OUTLINE 2n n n n 2n n n n Ref: http://www.ib.bioninja.com.au/ 14 J WERBA – IB BIOLOGY 14

HORMONES IN SPERMATOGENESIS Command term = STATE 11.4.3 HORMONES IN SPERMATOGENESIS Command term = STATE 3 hormones are involved in spermatogenesis: FSH LH testosterone J WERBA – IB BIOLOGY 15

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) J WERBA – IB BIOLOGY 16

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 J WERBA – IB BIOLOGY 17

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 J WERBA – IB BIOLOGY 18

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 J WERBA – IB BIOLOGY 19

11.4 SPERMATOGENESIS 20 J WERBA – IB BIOLOGY 20

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. J WERBA – IB BIOLOGY 21

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 J WERBA – IB BIOLOGY I 22

OVARY STRUCTURE AND FUNCTION Command term = ANNOTATE 11.4.4 OVARY STRUCTURE AND FUNCTION Command term = ANNOTATE J WERBA – IB BIOLOGY 23

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 J WERBA – IB BIOLOGY 24

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. J WERBA – IB BIOLOGY

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. J WERBA – IB BIOLOGY 26

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 J WERBA – IB BIOLOGY 27

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. J WERBA – IB BIOLOGY 28

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. J WERBA – IB BIOLOGY 29

OOGENESIS Command term = OUTLINE 11.4.5 OOGENESIS Command term = OUTLINE 30 J WERBA – IB BIOLOGY 30

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. J WERBA – IB BIOLOGY 31

OOGENESIS Command term = OUTLINE 11.4.5 OOGENESIS Command term = OUTLINE 32 J WERBA – IB BIOLOGY 32

OOGENESIS Command term = OUTLINE 11.4.5 OOGENESIS Command term = OUTLINE 2n 2n n n Ref: http://www.ib.bioninja.com.au/ 33 J WERBA – IB BIOLOGY 33

11.4 OOGENESIS 34 J WERBA – IB BIOLOGY 34

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 J WERBA – IB BIOLOGY 35

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 J WERBA – IB BIOLOGY 36

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 J WERBA – IB BIOLOGY 37

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 J WERBA – IB BIOLOGY 38

SPERMATOGENESIS & OOGENESIS Command term = COMPARE 11.4.8 SPERMATOGENESIS & OOGENESIS Command term = COMPARE J WERBA – IB BIOLOGY 39

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 J WERBA – IB BIOLOGY 40

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 J WERBA – IB BIOLOGY 41

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 = ????? J WERBA – IB BIOLOGY 42

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. J WERBA – IB BIOLOGY 43

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. J WERBA – IB BIOLOGY 44

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 J WERBA – IB BIOLOGY 45

PROCESS OF FERTILISATION Command term = DESCRIBE 11.4.9 PROCESS OF FERTILISATION Command term = DESCRIBE J WERBA – IB BIOLOGY 46

PROCESS OF FERTILISATION Command term = DESCRIBE 11.4.9 PROCESS OF FERTILISATION Command term = DESCRIBE J WERBA – IB BIOLOGY 47

PROCESS OF FERTILISATION Command term = DESCRIBE 11.4.9 PROCESS OF FERTILISATION Command term = DESCRIBE J WERBA – IB BIOLOGY 48

PROCESS OF FERTILISATION Command term = DESCRIBE 11.4.9 PROCESS OF FERTILISATION Command term = DESCRIBE J WERBA – IB BIOLOGY 49

EARLY EMBRYO DEVELOPMENT Command term = OUTLINE 11.4.11 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. J WERBA – IB BIOLOGY 50

EARLY EMBRYO DEVELOPMENT Command term = OUTLINE 11.4.11 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 J WERBA – IB BIOLOGY 51

EARLY EMBRYO DEVELOPMENT Command term = OUTLINE 11.4.11 EARLY EMBRYO DEVELOPMENT Command term = OUTLINE J WERBA – IB BIOLOGY 52

ROLE OF HCG IN EARLY PREGNANCY Command term = OUTLINE 11.4.10 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. J WERBA – IB BIOLOGY 53

ROLE OF HCG IN EARLY PREGNANCY Command term = OUTLINE 11.4.10 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. J WERBA – IB BIOLOGY 54

ROLE OF HCG IN EARLY PREGNANCY Command term = OUTLINE 11.4.10 ROLE OF HCG IN EARLY PREGNANCY Command term = OUTLINE J WERBA – IB BIOLOGY 55

PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE 11.4.12 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. J WERBA – IB BIOLOGY 56

PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE 11.4.12 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. J WERBA – IB BIOLOGY 57

PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE 11.4.12 PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE J WERBA – IB BIOLOGY 58

PLACENTA STRUCTURE AND FUNCTION Command term = OUTLINE 11.4.12 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. J WERBA – IB BIOLOGY 59

THE AMNIOTIC SAC & AMNIOTIC FLUID Command term = STATE 11.4.13 THE AMNIOTIC SAC & AMNIOTIC FLUID Command term = STATE The foetus is supported and protected by the amniotic sac and amniotic fluid. J WERBA – IB BIOLOGY 60

THE AMNIOTIC SAC & AMNIOTIC FLUID Command term = STATE 11.4.13 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. J WERBA – IB BIOLOGY 61

EXCHANGE ACROSS THE PLACENTA Command term = STATE 11.4.14 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! J WERBA – IB BIOLOGY 62

EXCHANGE ACROSS THE PLACENTA Command term = STATE 11.4.14 EXCHANGE ACROSS THE PLACENTA Command term = STATE J WERBA – IB BIOLOGY 63

THE BIRTHING PROCESS Command term = STATE 11.4.15 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. J WERBA – IB BIOLOGY 64

THE BIRTHING PROCESS Command term = OUTLINE 11.4.15 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. J WERBA – IB BIOLOGY 65

THE BIRTHING PROCESS Command term = OUTLINE 11.4.15 THE BIRTHING PROCESS Command term = OUTLINE J WERBA – IB BIOLOGY 66

Sample questions Q1. Which of the cells labelled in the diagram below provides nourishment for developing sperm cells? J WERBA – IB BIOLOGY 67

Sample questions Q2. Which pair of statements best describes oogenesis and spermatogenesis? J WERBA – IB BIOLOGY 68

Sample questions A1. C A2. D J WERBA – IB BIOLOGY 69

Sample questions Q3. Explain the function and structure of the placenta. [8] J WERBA – IB BIOLOGY 70

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 J WERBA – IB BIOLOGY 71