Reproduction and Development Biology PDF

8/27/24, 2:16 PM Platform | Study Fetch Reproduction and Developmental Biology Asexual Reproduction (00:00:37 - 00:01:29) Binary Fission Process by which a prokaryotic cell divides in half The cell replicates its DNA and...

8/27/24, 2:16 PM Platform | Study Fetch Reproduction and Developmental Biology Asexual Reproduction (00:00:37 - 00:01:29) Binary Fission Process by which a prokaryotic cell divides in half The cell replicates its DNA and then a septum is created to divide the cell into two daughter cells Budding Outgrowth that forms on organisms like hydra and yeast A smaller version of the organism forms and then breaks off to become an independent organism Regeneration Organism can be fragmented into multiple pieces, and each piece will form a new adult organism Parthenogenesis Embryo develops from an unfertilized egg in a sexually reproducing species Example: Honey bees Human Reproduction (00:01:29 - 00:03:40) Male Reproductive System Spermatogenesis Spermatogonia are the stem cells that produce sperm Spermatids are the partially differentiated sperm cells Sperm Structure Head contains the nucleus and acrosome (enzymes to penetrate egg) Midpiece contains mitochondria to power the tail/flagella Tail/Flagella provides motility to reach the egg Reproductive Anatomy Seminiferous tubules are the site of spermatogenesis Epididymis stores sperm Vas deferens transports sperm Ejaculatory ducts release sperm during ejaculation Urethra and penis allow sperm to exit the body Accessory Glands Seminal vesicles secrete fructose Prostate gland increases alkalinity Bulbourethral glands secrete mucus These fluids help protect and nourish the sperm https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce17e6d56e584fb7692c13/document?go=note 1/8 8/27/24, 2:16 PM Platform | Study Fetch Hormonal Regulation FSH from pituitary stimulates Sertoli cells to facilitate spermatogenesis LH from pituitary stimulates Leydig cells to produce testosterone Female Reproductive System Oogenesis Oogonia are the stem cells that produce oocytes Primary oocytes undergo meiosis to form secondary oocytes and polar bodies Ovarian Cycle Follicle development is stimulated by FSH Ovulation is triggered by a surge of LH Corpus luteum produces progesterone to prepare the uterus Uterine Cycle Menstruation occurs when the uterine lining is shed Proliferative phase rebuilds the uterine lining Secretory phase prepares the lining for implantation Fertilization and Embryonic Development Sperm must penetrate the egg's acrosome and zona pellucida Zygote undergoes cleavage divisions to form a blastocyst Blastocyst implants in the uterine lining and develops into an embryo Embryology (00:03:40 - 00:04:30) Germ Layers Ectoderm forms the nervous system and epidermis Mesoderm forms muscles, bones, circulatory system Endoderm forms the digestive and respiratory systems Organogenesis Development of the major organ systems from the germ layers Includes formation of the heart, lungs, brain, and other vital organs Fetal Development Placenta and umbilical cord provide nutrients and oxygen to the fetus Fetus undergoes dramatic growth and differentiation over 9 months Birth occurs when the fetus is ready to survive outside the uterus The Reproductive System The Male Reproductive System https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce17e6d56e584fb7692c13/document?go=note 2/8 8/27/24, 2:16 PM Platform | Study Fetch (00:03:40 - 00:03:51) The hypothalamus releases GnRH, which stimulates the anterior pituitary to release FSH and LH Testosterone from Leydig cells in the testes will: Inhibit the anterior pituitary and hypothalamus via negative feedback Stimulate the Sertoli cells The Female Reproductive System (00:03:51 - 00:04:03) The ovaries produce ova (eggs) The fallopian tubes are where the egg travels to reach the uterus (00:04:03 - 00:04:14) Ectopic pregnancy occurs when the embryo develops in the fallopian tube instead of the uterus The uterus is where the egg develops into an embryo The uterus has 3 layers: perimetrium, myometrium, and endometrium The endometrium is the layer that is shed during menstruation (00:04:14 - 00:04:28) The cervix is the entrance to the uterus from the vagina (00:04:28 - 00:04:39) Oogenesis produces 1 mature egg and several polar bodies, unlike spermatogenesis which produces 4 viable sperm (00:04:39 - 00:04:51) FSH stimulates follicle development in the ovaries LH stimulates ovulation of the egg Estrogen and progesterone regulate the menstrual cycle and secondary sex characteristics (00:04:51 - 00:05:04) Diagram of the menstrual cycle: Phase Hormone Levels Menstrual Flow Estrogen and progesterone low, FSH and LH somewhat higher but LH low Proliferative FSH and LH increase, estradiol increases Secretory Progesterone surges, then drops off (00:05:04 - 00:05:24) If pregnancy occurs, progesterone is maintained by the embryo's production of human chorionic gonadotropin (hCG) If no pregnancy, progesterone drops, signaling shedding of the endometrial lining (menstruation) (00:05:24 - 00:05:42) Hormone feedback loops in females: https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce17e6d56e584fb7692c13/document?go=note 3/8 8/27/24, 2:16 PM Platform | Study Fetch Hypothalamus releases GnRH Anterior pituitary releases FSH and LH Ovarian hormones (estradiol, progesterone) provide negative feedback to the hypothalamus and pituitary (00:05:42 - 00:07:03) Inhibin from Sertoli cells and testosterone from Leydig cells provide negative feedback to the hypothalamus and pituitary, regulating FSH and LH levels Fertilization and Early Embryonic Development Fertilization Events (00:07:03 - 00:07:25) Capacitation: Destabilizes the sperm's plasma membrane and increases its permeability to calcium Prepares the sperm to penetrate the egg Acrosome Reaction: Contact between the sperm and egg initiates the acrosome reaction The acrosome membrane fuses with the sperm head membrane, releasing enzymes that break down the zona pellucida (coating of the egg) Polyspermy Block: Prevents more than one sperm from fertilizing an egg Fast block: Depolarization of the egg's membrane helps repel sperm Slow block: Calcium ions released inside the egg's plasma membrane stimulate the cortical reaction Meiosis II: The fertilized egg completes meiosis II, releasing the second polar body Stages of Embryonic Development (00:09:13 - 00:10:26) Day 1: Fertilization Fertilization occurs, creating the zygote Day 2-3: Cleavage The zygote undergoes cell division, forming a compact mass of cells Day 4: Differentiation The cells differentiate into the inner cell mass and the trophoblast The blastocyst cavity forms https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce17e6d56e584fb7692c13/document?go=note 4/8 8/27/24, 2:16 PM Platform | Study Fetch Day 5: Implantation The blastocyst implants in the uterine epithelium The trophoblast cells begin to form the placenta Day 12: Bilaminar Disc The mesoderm forms and spreads The amniotic sac begins to enlarge Day 23: Amnion and Umbilical Cord The amniotic sac, chorion, and umbilical cord begin to form and function Monozygotic Twins Occur when a single fertilized egg divides into two separate embryos Can have different chorion and amnion configurations depending on the timing of the division Anterior Pituitary Hormones (00:07:03) LH (Luteinizing Hormone) is released from the anterior pituitary Fertilization and Early Embryonic Development Monozygotic vs. Dizygotic Twins (00:10:57 - 00:11:26) Monozygotic (identical) twins: Derived from the same embryonic origin Genetically identical Dizygotic (fraternal) twins: Two eggs fertilized by two sperm Genetically distinct, like siblings Cleavage Patterns (00:11:26 - 00:12:31) Spiral cleavage: Occurs at the 8-cell stage Radial cleavage: Occurs in protostomes and deuterostomes Differences in mouth and anus formation Determinate cleavage: https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce17e6d56e584fb7692c13/document?go=note 5/8 8/27/24, 2:16 PM Platform | Study Fetch Fate of blastomeres is not predetermined Indeterminate cleavage: Fate of blastomeres is predetermined Holoblastic cleavage: Even division throughout the embryo Embryos with little yolk Meroblastic cleavage: Uneven division Embryos with a lot of yolk Morula and Blastula (00:12:31 - 00:13:11) Morula: Ball of 12-16 cells Blastula: Formed after blastocoel (hollow space) is created Contains trophoblast (outer layer) and inner cell mass Trophoblast becomes extra-embryonic structures (placenta, amnion) Inner cell mass becomes the embryo Gastrulation (00:13:11 - 00:14:17) Blastula cells rearrange to form the germ layers: Ectoderm Mesoderm Endoderm Primitive streak forms, leading to the formation of the germ layers Ectoderm forms outer surface and central nervous system Mesoderm forms muscle, blood, kidneys, bone Endoderm forms internal organs Germ Layer Derivatives (00:14:17 - 00:14:35) Ectoderm: Outer surface Central nervous system Mesoderm: Muscle Blood system https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce17e6d56e584fb7692c13/document?go=note 6/8 8/27/24, 2:16 PM Platform | Study Fetch Kidneys Bone Endoderm: Internal organs Embryonic Development and Organ Formation Digestive Tube and Germ Cells (00:14:35 - 00:14:46) The digestive tube, pharynx, and lungs form as a budding off of the gastrointestinal tract The germ cells of the new embryo will also form during this process Ectoderm (00:14:46 - 00:15:07) Ectoderm Mnemonic: Ectoderm is the attracted derm, pretty skin and health Ectoderm will form: Epidermis and skin Nails Jaws and teeth Brain, central nervous system (CNS), and peripheral nervous system (PNS) Sensory parts of skin and nails Sweat glands Mesoderm (00:15:07 - 00:15:24) Mesoderm Mnemonic: Mesoderm means "of having sex" Mesoderm will form: Gonads Bones and skeleton Muscles Cardiovascular system Blood Spleen Endoderm https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce17e6d56e584fb7692c13/document?go=note 7/8 8/27/24, 2:16 PM Platform | Study Fetch (00:15:24 - 00:15:47) Endoderm Mnemonic: Endoderm is the "end internals of the end P TT" Endoderm will form: Epithelial lining of internal organs Pancreas Liver Thyroid Parathyroid Thymus Organogenesis (00:15:47 - 00:15:58) Organogenesis is the process by which organs are formed from the three germ layers Patterning and adult structure formation occurs during this process Neurulation (00:15:58 - 00:16:30) Neurulation is the formation of nervous tissue It begins with the formation of a neural plate from the ectoderm The neural plate then folds inward to form the neural tube, which will become the central nervous system Embryonic Models (00:16:30 - 00:17:58) In mammals, the amnion secretes amniotic fluid to cushion and protect the embryo The embryo will inhale and drink the amniotic fluid, then excrete it, recirculating the fluid If the embryo cannot excrete the fluid (e.g., renal agenesis), it can lead to birth defects The chorion forms the placenta, the allantois becomes the umbilical cord, and the yolk sac nourishes the fetus Chick embryos are nourished by a yolk sac, while human embryos are nourished by the placenta and umbilical cord https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce17e6d56e584fb7692c13/document?go=note 8/8