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Human Reproductive System Review Male Reproductive System Sperm Formation • • • • • MEIOSIS forms sperm ( male gametes) Sperm forms in testes Scrotum kept 5˚ cooler than rest of body Semen is sperm plus protecting fluid Semen leaves testes through the epididymis and then vas deferens (sperm ducts) to the urethra before it exits. Secondary Sexual Characteristics - Male • Produced by testosterone – Deeper voice – Chest and facial hair – Lengthen bones – Increased size of testes for sperm production Female Reproductive System Mrs. Degl Ovum Formation • MEIOSIS forms the eggs (ova) • Eggs are formed before birth • 1 egg per month is matured and released from ovaries, most of the time • Eggs travel through the fallopian tube where they may become fertilized • If not, a mature female will menstruate and begin cycle again Secondary Sexual Characteristics - Female • Induced by increased LH, FSH, estrogen, and progesterone hormone levels – Pubic hair – Widen pelvis – Enlarge mammary tissue (breasts) – Begin menstrual cycles Overview of Fertilization/Development - We’ve already learned how gametes are produced (gametogenesis) through meiosis - What process produces every other cell in the human body? MITOSIS Fertilization • • • • Occurs in upper 1/3 of Fallopian tube Only 1 sperm can fertilize an egg Fertilized egg = zygote An average woman is pregnant (gestational period) for 9 whole months. That is 40 weeks. Zygote Morula • The zygote undergoes several mitotic divisions (cleavage) over a 3-4 day period – 2-cell 4-cell 8cell 16 cell • Finally it becomes a (16celled) morula. It is still a solid ball of cells with defining shape Stem Cells • Totipotent cells: capable of developing into all the different cell types – all cells of mammalian embryos are totipotent until the 16-cell stage • Plueripotent cells – can differentiate into many tissues, but not all – Come from the ICM of blastocyst The Controversy Morula Blastocyst • Slowing, the morula cavitates and the inner cells begin to migrate to one small section of the embroyo forming the inner cell mass (ICM) • The outer, trophoblast cells will become the placenta • The ICM cells will become the embryo Implantation • As the fertilized egg developed from zygote to blastocyst, it was being moved down the fallopian tubes via smooth muscle contractions to the uterus • In apes (not like this in most species), the blastocyst actually digs through the uterine wall causing some women to experience implantation bleeding Implantation • Blastocyst implants into thick walls of uterus • Embryo gets air and nutrients through the umbilical cord • Once pregnant, progesterone levels stay high in mom (“pro” = for “gestation” = pregnancy) • Mom’s uterus grows with the baby Blastocyst Gastrula • Gastrulation – The outer-wall of the blastocyst invaginates on itself (folds in) and three distinct germ layers form • A germ layer is a primary layer of cells that form during embryogenesis • These layers become specific structures – Ectoderm, Mesoderm, Endoderm 1st Trimester = 1st 12 weeks • • • • Heart develops first Neural tube develops Tissues and organs are laid out All body systems appear by Week 8 = “organogenesis” • Now a Fetus 2nd Trimester = up to 24 weeks 3rd Trimester = Up to 40 weeks • • • • • More growth Kicking, rolling, stretching Eyes open – Week 32 Lungs mature Rotates to head-down position, unless baby is breech Birth • Labor – Uterine contractions begin – Cervix dilates to 10 cm. • Birth – Uterus pushes baby through vaginal canal – Placenta delivered after baby – Cesarean Section (c-section) is a surgery that cuts through the uterus to deliver the baby if it cannot be born vaginally Mrs. Degl Throw Back Mrs. Degl