Pregnancy or gestation, as it's known, is when there's one or more embryos in the uterus. Now, pregnancy in humans is divided into trimesters. And during the first trimester, there's a lot of interesting stuff happening. Following implantation, this hormone, human chorionic gonadotropin hormone, or HCG as it's often referred to, will be secreted and will actually prevent the degradation of the corpus luteum and halt the menstrual cycle. Interestingly, this hormone is actually what a lot of pregnancy tests test for. And you can see an example of that right behind me there. Now, the outer layer of the blastocyst is known as the trophoblast, and this is what's going to grow into the endometrium to form the placenta. Now, the placenta is an incredibly important organ. It's going to allow for the exchange of materials, nutrients, and wastes between the mother and fetus. This is how the developing embryo is going to eat, breathe, and get rid of its waste products. So, very very important. The developing fetus is connected to the placenta by an umbilical cord, and this actually contains two arteries and a vein. Now, the fetus is going to or technically the embryo is considered a fetus once it has its adult structures in their rudimentary form. And this is going to happen through organogenesis or the development of organs. And you can see here how the fetus is curled up inside the womb, and how it has this bundle of two arteries and a vein that connects to the placenta. Now, in humans, we give birth to live offspring. This is known as, or we are known as viviparous organisms for this reason. But some organisms lay eggs, and this is known as oviparous. Whereas, some reproductive strategies are ovoviviparous, and this is when the egg will remain inside the parent until it's ready to hatch. Now with humans, we undergo labor. These are uterine contractions that will expel the fetus from the uterus. And this is stimulated by the hormone, oxytocin. And this is actually involved in a positive feedback loop, because pressure from the head of the fetus on the cervix stimulates oxytocin release. Oxytocin stimulates uterine contractions, which are going to increase the pressure on the cervix leading to more oxytocin release. So you can see how this is a positive feedback loop. Now, we, humans, are considered eutherians because we give birth to live developed offspring. There are other types of mammals though, known as monotremes, which actually lay eggs, and marsupials that give birth to underdeveloped offspring that have to remain in this pouch that actually contains the mammary gland nipple. Now, mammary glands are what define mammals and are one of the things that define mammals, and these are going to be glands that secrete milk in a process known as lactation. The hormone prolactin stimulates this milk production, and oxytocin actually stimulates the secretion of milk in response to suckling by the infant. That's all I have for this lesson. I'll see you guys next time.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny40m
- 26. Prokaryotes4h 59m
- 27. Protists1h 6m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
44. Animal Reproduction
Animal Reproduction
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