Fertilization to Implantation Booklet 2 PDF

Fertilization to Implantation BOOKLET 2  Learner outcomes… What you need to know! ⚫ trace the processes of fertilization, implantation and extra-embryonic membrane formation, i.e., placenta, amnion, chorion, allantois, followed by embryonic and fetal development, parturition and la...

Fertilization to Implantation BOOKLET 2  Learner outcomes… What you need to know! ⚫ trace the processes of fertilization, implantation and extra-embryonic membrane formation, i.e., placenta, amnion, chorion, allantois, followed by embryonic and fetal development, parturition and lactation, and describe the control mechanisms of these events, i.e., progesterone, LH, human chorionic gonadotropin (hCG), prostaglandins, oxytocin, prolactin ⚫ describe development from fertilization to parturition in the context of the main physiological events that occur in the development of organ systems during each major stage (trimester); i.e., zygote, blastocyst, gastrulation, general morphogenesis 2  Learner outcomes… What you need to know! ⚫ identify major tissues and organs that arise from differentiation and morphological development of the ectoderm, mesoderm and endoderm in the embryo; i.e., -ectoderm: nervous system, epidermis -mesoderm: skeleton, muscles, reproductive structures -endoderm: lining of the digestive and respiratory systems, endocrine glands 3 Terms you need to know Oviduct (2n) and (n) Zygote Cleavage Morula Blastocyst Trophoblast (chorion) Mitosis Implantation Undifferentiated Cell 4 Terms you need to know Gastrulation Ectoderm Mesoderm Endoderm Gastrula Ectopic Neurulation Chorion Amnion Allantois Yolk Sac Placenta Umbilical Cord 5  First Stages of Development Fertilization: Occurs: in FALLOPIAN TUBE(oviduct) (within 24 h of ovulation) Only a few dozen of the best swimmers make it!! ⚫ Sperm reaches egg & uses acrosome to digest through outer layer ⚫ Sperm travels further eventually reaching the plasma membrane of the ovum. ⚫ One sperm enters, causing cell membrane to depolarize preventing entrance of other sperm. ⚫ Sperm and Ovum nuclei fuse (23+23 = 46)  Fertilization ⚫ Gametes (n) fuse to form a zygote (2n) ⚫ Zygote = first SINGLE cell of new life Actual Image Egg (n) + sperm (n) (2n)  Early Stages of Development ZYGOTE When can Conception Occur? ⚫ Ova can survive at most for approx. 1-2 days post ovulation while sperm can survive for up to approx. 5 days given the right environment. ⚫ Given a normal menstrual cycle, when could pregnancy occur?  Zygote (2n) Cell Cleavage ⚫ Zygote undergoes mitotic divisions (cleavage ) to form ball of cells called morula (16-32 cells by day 5) ⚫ Morula develops into blastocyst (day 7) Morula (2n) Blastocyst (2n) Blastocyst inner cell mass Chorion a cavity (space) opens up in the morula ◻ Chorion (trophoblast): outer layer of blastocyst Chorion forms placenta and cavity the amnion ◻ inner cell mass: will develop into embryo From Ovulation to Implantation Zygote Mitosis 16- 32 cells Chorion  From Ovulation to Implantation ⚫ Day 1: First Cleavage – cell divides by mitosis ⚫ Day 4: 16 – 32 cell stage. Ball of cells is called a morula. ⚫ Day 5: the cells of the morula begin to move around to form an inner and outer layer of cells. The outer layer of flattened cells (chorion) are important for implantation in the uterine lining. ⚫ Day 7: The two layers of cells arrange themselves around a hollow fluid filled cavity called the blastocoel, the actual cell mass is called a blastocyst.  From Ovulation to Implantation Day 8: Implantation 1. The blastocyst, by means of villi and enzymes secreted by the chorion (the membrane that forms around it), implants itself in the endometrium thus resulting in pregnancy (gestation). 2. The chorion secretes hCG, (Human chorionic gonadotropin) a hormone which stimulates the corpus luteum to produce progesterone and estrogen for the first 3 months. STEM CELLS Stem cells from the blastocyst are undifferentiated …can develop into any cell in the body and can be used for stem cell research. First Spinal Cord Stem Cell Surgery (3 min) A stem cell Story (15 min) REVIEW THE STEPS: Mitosis zygote morula hCG Helps to implant blastocyst chorion Corpus luteum Secretes produces hCG for progesterone 3 months and estrogen for 3 months  Gastrulation (~Day 7) ⚫ Gastrulation is the process in which the inner cell mass of blastula turns into 3 germ layers (embryonic tissues) – the (ectoderm, mesoderm, endoderm) ⚫ embryo now called gastrula Gastrulation (~Day 7) Cells begin to differentiate (change) to form specific organ systems! -nervous system Ectoderm -epidermis (skin) -Skeleton Mesoderm -Muscles -Gonads (reproductive structures) So Many Gonads -Respiratory system Endoderm -Digestive a -Endocrine glands R.E.D. Bozeman 6:50- 8:59 How to remember the stages? Zebras Make Better Guacamole Every Friday Zygote – Day 0 (Sperm + egg) Morula – Day 4 (16 – 32 cells) Blastocyst – Day 6 **Implantation Outer layer (chorion) helps the implantation process, secretes hCG and forms placenta How to remember the stages con’t… Zebras Make Better Guacamole Every Friday Gastrula – Day 7 - 3 germ layers – ectoderm, mesoderm, endoderm. Neurulation – formation of neural tube which will form CNS. Embryo – Day 10 - chorion starts to form the placenta Fetus – week 8 – called fetus because all major organ systems have started to develop Ectopic Pregnancy: Faulty Implantation ⚫ In an ectopic pregnancy, a fertilized egg has implanted outside the uterus, usually in the fallopian tube. ⚫ Severe bleeding and possible death of the mother can result from this type of pregnancy Pregnancy Tests Outer layer of the blastocyst (the chorion) starts to secrete hCG when it implants in the endometrium on ~day 7. This causes morning sickness & is the hormone measured in a pregnancy test! Pregnancy test: tests for the presence of hCG in the urine (sometimes the blood). Remember hCG: similar to LH – keeps corpus luteum secreting progesterone & estrogen for 3 months!! Later on, the placenta secretes sufficient estrogen and progesterone How can a miscarriage occur? For first 3 months progesterone comes from mother Fetus starts making it’s own after 3 months If mom stops progesterone and fetus does not start… – Miscarriage occurs Neurulation: formation of neural tube 🡪 develops into brain and spinal cord. Happens during the gastrula stage Becomes the primative curve of the spine  Practice:State the layer (ecto, meso, endo) that the part originates from 1. Lungs ____Endo___________ 11. Hair ______Ecto__________ 2. Eye ______Ecto___________ 12. Muscles _____Meso________ 3. Skin _____Ecto___________ 13. Pancreas ___Endo_______ 4. Heart ____Mes___________ 14. Hypothalamus ___Ecto_____ 5. Stomach ____Endo_________ 15. Thyroid gland _____Endo___ 6. Brain _____Ecto___________ 16. Large intestine ____Endo__ 7. Testes _____Meso_________ 17. Bones ____Meso__________ 8. Small Intestine ___Endo_____ 18. Finger nails ___Ecto_______ 9. Teeth ____Ecto__________ 19. Ovaries _____Meso_______ 10. Spinal cord ______Ecto______  Summary of Events After Implantation Days 7-10 Gastrulation begins – major cellular reorganization into the three germ layers “Gastrula” stage is when different genes will be turned on to express different organs in the later stages of the pregnancy Days 10-14 Pregnancy fully established Amniotic cavity forms Yolk sac forms Embryo forms Chorion starts to form the placenta Days 15-21 Emergence of the body plan “Primitive streak” starts to form (at site of Gastrulation) becomes mesoderm Neural Groove forms (future brain and spinal cord) Day 21 Heart begins to Week 4 beat Eyes, ears and lower limbs begin to develop Weeks 5 – 8 Teeth, palate, external genitalia begin to develop  Extra-Embryonic Membranes formed after implantation 1. Chorion: outer membrane of blastocyst ⚫ secretes hCG until 2nd trimester (first 3 months) ⚫ fetal contribution to the placenta ⚫ gas/nutrient/waste exchange 2. Amnion: inner membrane of outer layer of blastula ⚫ becomes fluid-filled ⚫ sac that protects embryo ⚫ from infection, impact and temperature fluctuations Extra-Embryonic Membranes..CON’T formed after implantation 3. Allantois: forms the foundation of the umbilical cord ⚫ Becomes part of the bladder 4. Yolk sack: Small in humans ⚫ (forms blood cells) In other animals -provides nutrients Extra-Embryonic Membranes n , hCG n ta tio l a Imp lacenta p and Amniotic Fluid Umbilical cord and bladder Blood cells CHICK Pool of blood HUMAN  Placenta ⚫ Placenta: allows exchange of some substances between mother and fetus ⚫ from mother: nutrients, oxygen, antibodies, viruses, drugs, alcohol ⚫ from fetus: metabolic wastes (CO2, urea) ⚫ NO exchange of blood cells  Placenta ⚫ formed when chorion extends into endometrium ⚫ not fully developed until the 2nd trimester ⚫ secretes estrogen & progesterone during the 2nd & 3rd trimesters ⚫ Progesterone prevents contractions ⚫ Progesterone and estrogen cause growth of the endometrium The Placenta To Baby Away The placenta will function as the: Lungs: exchange O2 and CO2 Small Intestine: provide nutrients Kidneys: remove nitrogenous wastes (urine)  Umbilical Cord ⚫ Rope-like structure that forms after 8 weeks ⚫ Runs from the belly button of the fetus to the placenta FYI ⚫ Contains 2 arteries and 1 vein ⚫ 2 arteries carry deoxygenated blood… from fetus to mother ⚫ Vein carries oxygenated blood… from mother to fetus ⚫ Normally arteries carry oxygenated blood ⚫ Only 2 exceptions exist…pulmonary(heart) artery & umbilical artery!!! ⚫ b/c an artery is defined as tubes that carry blood from the heart and not necessarily oxygenated blood  Uterus Amniotic Fluid Placenta Umbilical Cord Chorion Amnion Layers of the womb FROM THE OUTSIDE Cervical plug -uterus (mucus) Helps -placenta to keep out Cervix -chorion pathogens -amnion -amniotic fluid Vagina -baby