BIOL1XX8 2024 L21 Making Eggs and Sperm PDF

Reproduction and Development Making Eggs and Sperm (Part 1) Dr Osu Lilje School of Life and Environmental Sciences Ed Uthman from Houston, TX, USA, CC BY 2.0 , via Wikimedia Commons Mitosis Meiosis Homologous pair e.g....

Reproduction and Development Making Eggs and Sperm (Part 1) Dr Osu Lilje School of Life and Environmental Sciences Ed Uthman from Houston, TX, USA, CC BY 2.0 , via Wikimedia Commons Mitosis Meiosis Homologous pair e.g. Chromosome 1 (from each parent) bind together  Mitosis Same Meiosis 4 stages in total (plus interphase) Produce new 8 stages in total (plus interphase) Happens in somatic cells cells Happens in germ/sex cells Purpose is cellular proliferation Similar basic Purpose is sexual proliferation Produces 2 diploid daughter cells steps Produces 4 haploid daughter cells Chromosome number remains the Start with a Chromosome number is halved in same single parent each daughter cell Genetic variation doesn’t change cell Genetic variation increased Female reproductive system Ovaries open into peritoneal cavity fimbriae Fimbriae direct ovum into uterine tube/fallopian tube/oviduct cilia Successful fertilization normally occurs in the first third of the uterine tube Vagina – channel connecting to the cervix Frontal view Male reproductive system Testis and scrotum Epididymis From testis via tubules and ductules Maturation Vas deferens or ductus deferens Blood vessels and nerves approx. 45cm long peristaltic movement Urethra Lateral view Male reproductive system Seminal vesicles Prostaglandin, stimulate motility of sperm Fructose, nutrient source for the sperm Clotting agents (different from blood), coagulates semen after ejaculation Prostate gland Citric acid, used by sperm in ATP production (energy) Proteolytic enzymes, eventually breakdown clotting agents Bulbourethral (Cowper’s) glands Mucous (released pre-ejaculation), lubricate urethra and end of penis to prevent damage to sperm Alkaline fluid, neutralize acidity of urethra Frontal view Semen (100x106 sperm/ml, 2-5ml, 60% seminal vesicle, 30% prostate, 5% testes, 5% bulbourethral glands) Making Eggs and Sperm (Part 2) Dr Osu Lilje School of Life and Environmental Sciences https://www.flickr.com/people/93087247@N00  Spermatogenesis A. F. Dixon, Cunningham's Text-book of Anatomy., Public domain, via Wikimedia Commons Seminiferous tubules in testes germ cells- develop into spermatocytes Sertoli cells – nourish developing germ cells Spermatogonia Primary spermatocyte (2n) Secondary spermatocyte (n) Spermatid (n) www.mhhe.com/seeleyess8  Spermatogenesis Spermatid (n) TrJaagup, CC BY-SA 3.0 , via Wikimedia Commons Differentiation (while nourished by sertoli cells) head, acrosome, midpiece and flagellum Released into lumen of seminiferous tubules to the epididymis for further maturation www.mhhe.com/seeleyess8  Oogenesis Ovaries are suspended by ligaments Ovarian follicle containing oocyte blood vessels, lymphatic vessels and nerves The University of Sydney www.mhhe.com/seeleyess8 Oogenesis Oogonia 5 million before birth (2nd trimester) Primordial follicle (2n) cells 400 000 at birth primary oocyte – Pause at Prophase I 300 000 at puberty Primary follicle (2n) primary oocyte layers of granulosa cells zona pellucida Secondary follicle (2n) At puberty During a lifetime only 400 develop fully www.mhhe.com/seeleyess8 Follicle = oocyte + surrounding granulosa cells  Just before ovulation the oocyte completes Oogenesis Meiosis I and pauses during early Meiosis II. Meiosis will be completed if fertilization occurs Ovulation triggered by peak in luteinising hormone (LH) anterior pituitary Corpus luteum secretes progesterone and a small amount of oestrogen www.mhhe.com/seeleyess8 Reproduction and Development Making a Human (Part 1) Dr Osu Lilje School of Life and Environmental Science The hormones in males Before Puberty... Testosterone and inhibin inhibit GnRH (secreted by immature hypothalamus) and, LH and FSH secretion by the anterior pituitary gland www.mhhe.com/seeleyess8 The hormones in males Puberty... Begins at age 12 to 14yrs old Hypothalamus maturation reduces sensitivity to testosterone and inhibin GnRH secretion that increases Luteinising hormone (LH) and follicle stimulating hormone (FSH) Enlargement of reproductive organs and development of secondary male characteristics www.mhhe.com/seeleyess8 The hormones in females Before Puberty... Oestrogen and progesterone (ovaries) negative-feedback Low GnRH (immature hypothalamus), low LH and FSH (anterior pituitary) www.mhhe.com/seeleyess8 The hormones in females Puberty... Begins 11 to 13yrs old (menarche) Maturation of hypothalamus high GnRH, high LH and FSH decrease negative-feedback of oestrogen and progesterone oestrogen production increased by developing follicle Enlargement of reproductive organs and development of secondary female characteristics www.mhhe.com/seeleyess8