BIOL1XX8 2024 Development and Birth Lecture Notes PDF

Reproduction and Development Making a Human (Part 2) Dr Osu Lilje School of Life and Environmental Science The menstrual cycle Menses (4-5 days) removal of superficial layer of endometrium Day 1 of cycle – first full day bleeding The University of Sydney...

Reproduction and Development Making a Human (Part 2) Dr Osu Lilje School of Life and Environmental Science The menstrual cycle Menses (4-5 days) removal of superficial layer of endometrium Day 1 of cycle – first full day bleeding The University of Sydney www.mhhe.com/seeleyess8 The menstrual cycle Proliferative Stage Sustained increase in oestrogen stimulates GnRH secretion by hypothalamus GnRH triggers LH and FSH secretion from anterior pituitary FSH stimulates oestrogen prod. by develop. follicles, results in positive feedback Large increase in LH triggers ovulation (approx.day 14) which is the start of the secretory stage The University of Sydney www.mhhe.com/seeleyess8 The menstrual cycle Secretory Stage Corpus luteum Secretes progesterone and small amounts of oestrogen Ed Uthman, CC BY-SA 2.0 via Wikimedia Commons Progesterone thickens endometrium and causes fluid secretion (nutrients for embyo) Progesterone and oestrogen inhibit hypothalamus and anterior pituitary and hence LH and FSH secretion decline after ovulation. The University of Sydney The menstrual cycle Secretory Stage Cont. If fertilisation (7-8 days after ovulation) Endometrium becomes fully developed Human chorionic gonadotropin (HCG) production by the trophoblasts during implantation of the embryo which maintains corpus luteum No fertilisation - Menses Endometrium sloughed Corpus luteum degenerates, reducing progesterone Increase FSH The University of Sydney Fertilization and preimplantation embryo development All the ‘physiological events align’ Sperm Capacitation in the uterus (enzymes) – stabilize acrosomal head and strengthen tail motility Egg Secondary Oocyte released into uterine duct/fallopian tube www.mhhe.com/seeleyess8 The University of Sydney Reproduction and Development  Trophoblast Development and Birth (Part 1) Dr Osu Lilje School of Life and Environmental Science Inner cell mass Blastocyst The original uploader was Enzo at Polish Wikipedia., CC BY-SA 3.0 , via Wikimedia Commons Fertilization Cleavage Implantation Gastrulation Neurulation Organogenesis Parturition Fertilization Day 0 Granulosa cells (Corona radiata) Preventing polyspermy Two mechanisms prevent more than one sperm- 1 Fast block (Na+) diffuses into oocyte from extracellular space, and Secondary oocyte (n) 2 Slow block (Ca2+) release by ER, initiate cell division (complete meiosis) and trigger cortical reaction Zona pellucida Zygote Formed when pronuclei of sperm and egg fuse sperm pronuclei Polar body zygote Zona pellucida Atdoan0, CC BY-SA 4.0 The University of Sydney , via Wikimedia Commons  Fertilization Cleavage Implantation Gastrulation Neurulation Organogenesis Parturition Cleavage Day 1 to 6 - repeated mitotic division as the embryo migrates down the oviduct to the uterus zona pellucida “zona hatching” degeneration of zona pellucida and replacement with underlying trophoblast The University of Sydney totipotent  Fertilization Cleavage Implantation Gastrulation Neurulation Organogenesis Parturition Implantation Day 7 to 10 Day 12 Produce Human chorionic gonadotropin Two types (HCG) of trophoblast Contribute to development of the placenta form umbilical cord Developing placenta and umbilical cord – filtration barrier The University of Sydney Fertilization Cleavage Implantation Gastrulation Neurulation Organogenesis Parturition Gastrulation Day 12 Embryonic disc Primitive streak central axis triggers gastrulation (formation of germ cell layers) Germ cell layers Ectoderm Mesoderm Endoderm Ectoderm - skin and nervous system pluripotent Mesoderm - organs, muscle and bone Endoderm - digestive system The University of Sydney Fertilization Cleavage Implantation Gastrulation Neurulation Organogenesis Parturition Neurulation Day 18 Folding of neural tube determines position of Ectoderm 1. Grey matter (unmyelinated neurons and cell bodies) and 2. White matter (myelinated neurons) in the central nervous system Spinal cord white matter outside grey matter inside Brain grey matter outside white matter inside http://cnx.org/content/col11496/1.6/ The University of Sydney  Development and Birth (Part 2) Dr Osu Lilje School of Life and Environmental Science 4 month fetus Fertilization Cleavage Implantation Gastrulation Neurulation Organogenesis Parturition Organogenesis begins around 3 to 8 weeks and continue until birth Depends on the development of different organs Brain begins developing in week 3 Heart begins developing in week 3, the four chambers formed in week 7 Kidneys begin developing in week 9 *From fertilization to week 7 a developing human is referred to as an embryo. From week 8 to birth, the developing human is called a fetus. The University of Sydney Week 8 Fetus* Gestation 280 Days, 40 weeks or 9 months (3 trimesters) The University of Sydney  Fertilization Cleavage Implantation Gastrulation Neurulation Organogenesis Parturition Factors that influence Parturition Placenta ACTH – adrenocorticotropic hormone The University of Sydney