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menstrual cycle changes: uterus endometrium (loss), ovary follicle development.
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The second phase of the uterine cycle when estrogen causes the lining of the uterus to grow, or proliferate, during this time. As they mature, the ovarian follicles secrete increasing amounts of estradiol, and estrogen.
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Intercourse more than a day after ovulation will therefore usually not result in fertilization. During the journey, fluids in the female reproductive tract prepare the sperm for fertilization through a process called capacitation, or priming. The fluids improve the motility of the spermatozoa.
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The hormone progesterone is produced by the ovaries. Progesterone also stimulates the glands in the uterus to secrete substances that maintain the endometrium and keep it from breaking down. For this reason, this phase of the menstrual cycle is called the secretory phase.
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First cell mitotic divisions of the zygote forming initially 2 blastomeres that continue to divide to form the morula, a "berry", a solid mass of cells.
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The free-floating blastocyst has reached the uterine body still enclosed in the zone pellucida and "hatches" from this surrounding extracellular matrix. It is only after hatching that the blastocyst can attach to and then implant into the uterine wall.
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The attached blastocyst begin implantation into the maternal uterine lining epithelium and underlying stroma. The entire cellular products of the original fertilisation event are now referred to as the conceptus. When conceptus implantation completes, a coagulation plug is formed at the site of implantation and the entire process of development will occur enclosed within the wall of the uterus.
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The conceptus completes implantation during this stage. The trophoblast cells proliferate, syncytiotrophoblast cells continue to invade the maternal endometrium and cytotrophoblast cells form clumps that will later form sites of chorionic villi formation. The maternal endometrium locally begins the decidual process and the endometrial stroma accumulates fluid. The extraembryonic cavities begin to form. The bilaminar embryonic disc epiblast and hypoblast forms from the inner cell mass.
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The bilaminar embryo is now about 0.2 mm diameter in size. The three extra embryonic spaces (amniotic, primitive yolk sac and chorionic) are present. The large chorionic cavity is surrounded by the cell layers extending to form chorionic villi. These villi are the beginning of the functional units of the placenta.
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Gastrulation is continuing as cells migrate from the epiblast, continuing to form mesoderm. Mesoderm is a continuous sheet except at the buccopharyngeal and cloacal membranes. These membranes have ectoderm and endoderm only and will lie at the rostral and caudal of the gastrointestinal tract. From the primitive node a tube extends under the ectoderm in the opposite direction to the primitive streak. This tube forms first the axial process then notochordal process, then finally the notochord.
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The babys eyelid folds develop into the eyelids and cover more of the eye as the palpebral fissure takes shape. Sensory placodes, lens pit, otocyst, nasal pits moved ventrally, fourth ventricle of brain Heart fusion of aortic and mitral endocardial cushion material. The first generation of subsegmental bronchi now complete. Anal membrane defined. Cloacal membrane ruptures from urinary pressure at stage 18 or 19. Rete testis develops from the seminiferous cords, rete ovarii cords are developing.
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During stage 13, in the ectoderm the neural tube continues to close, Caudal neuropore closes, forebrain is still growing. In the mesoderm there is continued segmentation of paraxial mesoderm (21 - 29 somite pairs), heart prominence. The head is forming 1st, 2nd and 3rd pharyngeal arch, forebrain, site of lens placode, site of otic placode, stomodeum. The body is forming a heart, liver, umbilical, early upper limb bulge
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The hearing otic capsule formed by condensed mesenchyme. The lens vesicle and optic cup lie appear to press against the surface.The nasal discs form nasal pits. The hearts atrioventricular bundle appears and semilunar cusps appear. Coronary circulation plexus appears on the heart begin to acquire coronary sinus connection.The vertebrae and ribs formed, and primordia of sternum and hypaxial flank muscle primordium laterally in the body wall.
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Neural first parasympathetic ganglia, submandibular and ciliary, are identifiable, neural goes through vascular development. Abdominal wall muscle cell migration about 25% of the the abdominal cavity, the lateral plate mesoderm has become more condensed in the area around the myoblasts. Heart outflow tract elliptical configuration with four cushions, the two larger fusing at this stage. Semilunar valve leaflets form at the end of the head lip and palate components of the upper lip.
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Limb bone forms by endochondrial ossification and throughout embryo replacement of cartilage with bone. Neural smell vomeronasal fibres and nervus terminalis. Female uterus opening of the paramesonephric duct to the coelomic cavity formed as an invagination of the coelomic epithelium. Abdominal Wall separation of the myoblasts into distinct inner and outer layers. Abdominal wall thicker in the region where secondary structures were forming compared with the primary body wall region.
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The head scalp vascular plexus visible. Limbs upper limbs begin to rotate ventrally. Neural amygdaloid body has at least four individual nuclei. Oculomotor nerve shows a dorsolateral and a ventromedial portion. The cerebellum cell layer develops choroid plexuses of the fourth and lateral ventricles. Gastrointestinal tract anal membrane perforates. Neural cortical plate appears in the area of future insula and formation of the anterior communicating artery.
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Limb fingers and toes lengthen. The migratory streams of neurons from the subventricular zone of the olfactory bulb towards the future claustrum for smell. Uterus fused duct bifurcated at the caudal portion at Carnegie. Genital 8 Week Testis- mesenchyme, interstitial cells secrete testosterone, androstenedione. Genital 8 to 12 Weeks-HCG stimulates testosterone production. Tongue nerves penetrate basal lamina and synapse with undifferentiated,elongated,epithelial cells(taste bud progenitor cell).
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Stage 23 defines the end of the embryonic period. There is straightening of trunk, umbilical cord, intestines herniated at umbilicus in body. Extraembryonic Coelom chorionic cavity is now lost by fusion with the expanding amniotic cavity. Abdominal Wall rectus muscle forms 2 or 3 distinct layers with myotube orientation uniform in all muscles. The external oblique and internal oblique started to expand in thickness, transversus a thin layer of muscle. Gastrin containing cells in stomach antrum.
