Sexual Reproduction

Sexual Reproduction Male Reproduction Annotate a diagram of the testis tissue Sertoli cell 1. ………………………………………………………………………… Basement membrane 2. ………………………………………………………………………… Spermatogonia 3. ………………………………………………………………………… Primary spermatocyte 4. ………………………………………………………………………… Secondary spermatocyte 5. ………………………………………………………………………… Spermatid 6. ………………………………………………………………………… Outline the process of spermatogenesis Spermatogenesis involves mitosis followed by cell growth followed by meiosis (two divisions) and differentiation ………………………………………………………………………………………………………………………………………………….......... Occurs in seminiferous tubules (testes) and produces four gametes per germ cell ………………………………………………………………………………………………………………………………………………….......... Gametes differentiate into spermatozoa via a process that occurs continuously from puberty ………………………………………………………………………………………………………………………………………………….......... Annotate a diagram of a mature sperm Acrosome 1. …………………………………………………… Nucleus 2. …………………………………………………… Centriole 3. …………………………………………………… Mitochondria 4. …………………………………………………… Axoneme (within flagellum) 5. …………………………………………………… Outline the role of the following in the production of semen Where sperm matures and develops capacity to ‘swim’ Epididymus: …………………………………………………………………………………………………………………………………… Adds nutrients (provides energy for the sperm) and secretes prostaglandins Seminal Vesicle: ……………………………………………………………………………………………………………………………… Secretes alkaline fluids which help to neutralise vaginal acids Prostate Gland: ……………………………………………………………………………………………………………………………….. Female Reproduction Annotate a diagram of ovarian tissue Primordial follicle 1. ……………………………………………………………… Primary follicle 2. ……………………………………………………………… Secondary follicle 3. ……………………………………………………………… Graafian follicle (mature) 4. ……………………………………………………………… Oocyte 5. ……………………………………………………………… Corpus luteum 6. ……………………………………………………………… Corpus albicans 7. ……………………………………………………………… Outline the process of oogenesis Occurs in ovaries (completed in oviduct), with only one gamete produced per germ cell ………………………………………………………………………………………………………………………………………………….......... There is unequal division of cytoplasm (forms one egg and up to three polar bodies) ………………………………………………………………………………………………………………………………………………….......... Occurs in staggered stages (foetal development ⇨ puberty ⇨ fertilisation) ………………………………………………………………………………………………………………………………………………….......... Annotate a diagram of a mature egg Cytoplasm 1. ………………………………………………………………………... Nucleus (not technically present, but usually included) 2. ………………………………………………………………………... Cortical granule 3. ………………………………………………………………………... Zona pellucida (jelly coat) 4. ………………………………………………………………………... Corona radiata (follicular cells) 5. ………………………………………………………………………... Outline the events that precede the meiotic divisions of a developing egg cell The process begins during foetal development, when a large number of primordial cells are formed by mitosis ………………………………………………………………………………………………………………………………………………….......... The primary oocytes remain arrested in prophase I until puberty, when a girl begins her menstrual cycle ………………………………………………………………………………………………………………………………………………….......... Each month, hormones unlock some oocytes to begin the second meiotic division (but are arrested in metaphase II) ………………………………………………………………………………………………………………………………………………….......... If the oocyte is fertilised by a sperm, meiosis II is completed and the mature egg forms a ovum ………………………………………………………………………………………………………………………………………………….......... Fertilisation Compare the processes of spermatogenesis and oogenesis Feature Spermatogenesis Number of gametes produced Four Cytoplasmic division Equal Duration of process Continuous Timing of gamete release Lifelong (from puberty) Oogenesis One (+ polar bodies) Unequal In staggered stages Finite (menarche to menopause) Describe the conditions required for fertilisation Capacitation Biochemical changes occur when sperm enters the female reproductive tract ………………………………………………………………………………………………………………………………………………….......... Uterine chemicals dissolve the sperm’s cholesterol coat, improving its motility ………………………………………………………………………………………………………………………………………………….......... Acrosome Reaction To enter the egg, sperm must penetrate the protective jelly coat (zona pellucida) ………………………………………………………………………………………………………………………………………………….......... Acrosome vesicles release enzymes which soften the glycoprotein matrix ………………………………………………………………………………………………………………………………………………….......... Egg and sperm membranes fuse and the sperm nucleus (+ centriole) enters the egg ………………………………………………………………………………………………………………………………………………….......... Cortical Reaction Cortical granules release enzymes that destroy sperm-binding proteins on the jelly coat ………………………………………………………………………………………………………………………………………………….......... (after fertilisation has occurred) ………………………………………………………………………………………………………………………………………………….......... This prevents other sperm penetrating the fertilised egg (polyspermy) ………………………………………………………………………………………………………………………………………………….......... Embryo Development Outline the role of hCG in early pregnancy When a blastocyst is implanted into the endometrium it begins to secrete hCG (human chorionic gonadotropin) ………………………………………………………………………………………………………………………………………………….......... hCG sustains the corpus luteum and prevents its degeneration (continues to make oestrogen and progesterone) ………………………………………………………………………………………………………………………………………………….......... Oestrogen inhibits FSH & LH, preventing further egg release, while progesterone maintains the endometrium ………………………………………………………………………………………………………………………………………………….......... When a placenta develops and begins to produce progesterone, hCG levels drop and the corpus luteum degenerates ………………………………………………………………………………………………………………………………………………….......... Outline, with the aid of the diagram, the early development of an embryo A zygote undergoes several divisions to form a morula, and subsequent unequal divisions results in a blastocyst ………………………………………………………………………………………………………………………………………………….......... Blastocyst contains an inner cell mass (forms embryo), outer layer (trophoblast: forms placenta) and a cavity ………………………………………………………………………………………………………………………………………………….......... This occur in the oviduct and when the blastocyst reaches the uterus, it embeds into the endometrium ………………………………………………………………………………………………………………………………………………….......... Explain how the structure of the placenta relates to its function The placenta is a disc-shaped structure that nourishes the developing embryo ………………………………………………………………………………………………………………………………………………….......... It is formed from the trophoblast of a developing embryo (i.e. the outer layer) ………………………………………………………………………………………………………………………………………………….......... An umbilical cord connects a fetus to the placenta and maternal blood pools via open ended arterioles into lacunae ………………………………………………………………………………………………………………………………………………….......... Fetal chorionic villi extend into these lacunae and facilitate materal exchange ………………………………………………………………………………………………………………………………………………….......... List the materials that are exchanged between maternal blood and foetal blood within the placenta Nutrients, oxygen and maternal antibodies will be taken up by the fetus Maternal → Foetal: …………………………………………………………………………………………………………………………. Carbon dioxide and toxic waste products (e.g. urea) will be removed by the mother Foetal → Maternal: …………………………………………………………………………………………………………………………. Outline the hormonal role of the placenta Placenta takes over hormonal role as corpus luteum degenerates ; Estrogen stimulates growth of the uterine ………………………………………………………………………………………………………………………………………………….......... myometrium and mammary glands ; Progesterone maintains the endometrial lining and reduces uterine contractions ………………………………………………………………………………………………………………………………………………….......... Outline the role of hormones and positive feedback in the process of birth The fetus begins to stretch the uterine walls, which triggers the release of two hormones – oxytocin and estrogen ………………………………………………………………………………………………………………………………………………….......... Estrogen inhibits progesterone (which was preventing contractions) and oxytocin stimulates uterine contractions ………………………………………………………………………………………………………………………………………………….......... As the uterus contracts, stretch receptors are further stimulated (positive feedback) ………………………………………………………………………………………………………………………………………………….......... Contractions will stop when the baby is birthed (no more stretching of the uterus) …………………………………………………………………………………………………………………………………………………..........