Gametogenesis & Fertilization
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| What is the ampulla? | the widest part of the uterine tube and is where the egg goes immediately after ovulation
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| What is the ampulla also known as? | infundibulum
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| Fertilization occurs where and in what time frame? | in the ampulla within 12 hours of ovulation.
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| What happens if egg is not fertilized? | If not fertilized, the egg passes down the uterine tube and degenerates within 24 hours.
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| When are sperm motile and not? When are sperm motile? Non-motile? | Sperm are non-motile in the epididymus but are motile in the ejaculate.
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| Whatfactors effect motility? | Motility is affected by factors such as the pH of the uterus and the presence of an egg .
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| Where are sperm put first? | Sperm are deposited near the cervix during intercourse and move through the cervix into the uterus.
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| What female action assists sperm in reaching the uterus? | Sperm movement is assisted by contractions of the uterus and uterine tube.
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| How longs does it take for the sperm to reach the ampulla? | Sperm normally reach the ampulla in 1-7 hours.
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| What is capacitation? What is capacitation? | Activation of sperm that must happen before fertilization glycoproteins and seminal proteins are removed from the acrosome region and the sperm become more motile.
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| What are fibriae | protrusions on the ampulla that sweep oocyte into uterine tube
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| What must sperm pass through on the oocyte to fertilize the egg? Which sperm do so freely? | Sperm pass through the corona radiata (the layer of cumulus oophorus cells surrounding the oocyte). Capacitated sperm can pass freely through this cell layer while un-capacitated sperm do not.
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| What must sperm penetrate to fertilize oocyte? | Sperm penetrate the zona pellucida (glycoprotein covering the egg).
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| What is the acrosomal reaction? | Upon contact with the zona pellucida, sperm undergo the acrosome reaction which is the release of enzymes (proteases and acrosin) from the acrosome. These enzymes allow the sperm to penetrate the zona pellucida layer.
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| What is the zona reaction? | The first sperm to contact the egg initiates release of lysosomal enzymes from the oocyte plasma membrane -> zona reaction. Quickly changes permeability zona pellucida, preventing other sperm from penetrating
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| When do the oocyte and sperm plasma membrane fuse? How do they fuse? | Fusion of the oocyte and sperm plasma membranes occurs when the sperm first contacts the egg. The head and tail of the sperm enter the cytoplasm of the egg, leaving the plasma membrane behind.
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| What does the second meiotic division achieve? | forms the large definitive oocyte and a small residual second polar body.
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| When is a zygote formed? When is the zygote formed? | When the male and female pronuclei fuse
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| Describe the formation of blastomere | The chromosomes of the zygote line up on a cleavage spindle to begin the first mitotic division. Cleavage continues as the zygote moves down the uterine tube. These early embryonic cells are called blastomeres.
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| What happens to the blastomere with each successive division? | The blastomeres are still enclosed in the rigid zona pellucida so the blastomeres become smaller and more compact with each successive division.
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| What is a morula? | A mulberry in Latin and Spanish (and it looks like a mulberry)…but for our purposes it’s when there are 16 cells, approximately 3 days after fertilization
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| What are the inner cells of the morula and what will they become? | The inner cells of the morula make up the inner cell mass and will become the embryo proper.
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| What are the outer cells of the morula and what will they become? | The outer cells of the morula, the outer cell mass, will become the trophoblast and later the placenta.
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| When does the morula enters the uterus? | about 4-5 days after fertilization.
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| When does the zona pellucida begins to disintegrate? | on days 5 and 6.
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| How is a blastocoels formed? What is a blastocoel? | Fluid begins to enter the morula and creates a hollow space inside called a blastocoel.
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| What is the morula and the blastocoel called? | blastocyst.
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| What are trophoblast cells? | The cells of the outer cell mass that are now arranged 1 cell layer thick around the outside of the blastocoel.
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| What is the embryonic pole? | The cells of the inner cell mass (also known as the embryoblast) are now clustered to one pole termed the embryonic pole. What is Blastogenesis?
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| The events of implantation are as follows |
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| What happens between the 6-7th day after fertilization? | the embryonic pole of the blastocyst becomes partially embedded in the endometrial lining of the uterus.
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| The trophoblast proliferates rapidly into | cytotrophoblast and syncytiotrophoblast
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| cytotrophoblast are ? | cells surrounding the blastocystic cavity
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| syncytiotrophoblast cells are? | at the embryonic pole, and erode and proliferate into the uterine epithelium.
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| What is the hypoblast? | The cells of the inner cell mass (embryoblast) adjacent to the blastocystic cavity differentiate, forming a single layer of cells called the hypoblast.
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| Male Infertility accounts what percentage of infertility? | for 30 - 50%
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| Male infertility can result from? | low sperm counts, malformed sperm, non-motile or hypomotile sperm, and exposures to drugs or toxins.
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| Female infertility can result from? |
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| How many Early spontaneous abortion are estimated to occur? | in 45% of all fertilizations.
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| Why do early spontaneous abortions occur? | They mainly occur because of deleterious chromosomal abnormalities but can also occur from insufficient hormonal cues to initiate implantation.
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| Do women know that they are pregnant when they have a early spontaneous abortions? | No
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| What are the signs of early spontaneous abortions ? | The only clinical signs may be slight delay in their menstrual period, and the menstrual flow may be somewhat increased.
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| Describe Cell Cycle | G1: Cell growth and synthesis of cellular elements. S: DNA replication: each chromosome consists of two sister chromatids. G2: DNA repair, protein synthesis in preparation for cell division. M: mitosis: Cell division.’ Mitosis
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| Interphase | DNA strands replicate, forming 2 parallel sister chromatids joined by a centromere
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| Prophase | Mitosis begins, chromosomes condense, nuclear envelope disappears, centriole pairs migrate to opposite poles
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| Prometaphase | chromosomes continue to condense, chromatids become visible’
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| Metaphase | Chromosomes line up in the quatorial plane with their centromeres attached microtubules extending from the centriole forming the mitotic spindle
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| Anaphase | centromeres divide and each chromatid migrates toward the opposite pole
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| Telophase | At opposite poles chromosomes begin to uncoil, nuclear membrane reforms and cytoplasm divides (cytokinesis)
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| Meiosis | Cell division in the gonads-female and male gametes with half chromosome -requires two cell divisions Meosis I and II
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| Prophase I | Chromosomes condense. Homologous pairs of chromosomes one maternal one paternal. Form chiasmata via crossover of chromatids
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| Anaphase I | Homologous chromosomes migrate toward opposite poles and chiasmata separate
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| Telophase I | Half the chromosomes are now at each pole and the cytoplasm divides producing two haploid cells
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| Prophase II | chromosomes condense in haploid cells
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| Metaphase II | Chromosomes line up in equatorial plane
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| Anaphase II | Centromeres divide and each chromatid migrate toward the opposite pole
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| Telophase II | At opposite poles, the chromosomes begin to uncoil; nuclear membrane reforms and the cytoplasm divides producing two haploid cells.
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| Spermatogenesis | produce sperm
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| Primordial germ cells | arrive in the developing testis during the 4th and 5th week of gestation
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| Spermatogenesis begins | at puberty and continues into old age.
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| Describe the maturation into sperms from Type A spermatogonia to spermatids | Takes place in the sertoli cells of the seminiferous tubules. Type A spermatogonia via mitotic divisions become->type B spermatogonia which through division become->primary spermatocytes which through Meiosis I become ->secondary spermatocytes which thro
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| What do Sertoli cells do for the spermatids | Sertoli cells support and protect the developing spermatids
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| Spermiogenesis | maturation of spermatozoa-takes place in Sertoli cells’ Includes formation of Acrosome, condensation of nucleus, formation of neck, middle piece, and tail, shedding of excess cytoplasm
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| What happens after spermiogenesis is complete? | Spermatozoa enter the lumen of the seminiferous tubules and are transported to the epididymis where they are stored. Become functional and free swimming as they age.
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| Oogenesis | maturation of primordial germ cells to primary oocytes
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| Primordial germ cells | in developing ovary 4th to 5th week of gestation
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| Oogonia | what the primordial germ cells develop into after undergoing a number of mitotic divisions
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| Primary oocytes | in the 4th month of development oogonia undergo meiosis I and become primary oocytes
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| 5th month of development what happens? 7th month? | oogonia and many primary oocytes begin to degenerate and die. By 7th month, only 600,00 primary oocytes arrested in Meiosis I remain
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| At puberty, a pool of what is established and maintained? | growing follicles. Each month 15 to 20 follicles from this pool begin to mature but only 1 reaches full maturity, the others will stop maturing and degenerate.
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| primary follicle | maturing follicle with a covering of granulosa cells. The granulosa cells secrete a glycoprotein to cover the oocyte forming the zona pellucida.
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| What is the antrum? | A fluid filled cavity formed when the granulosa cell layer splits The folicle is now considered to be a secondary follicle. The granulosa cells that remain to cover the oocyte are called the cumulus oophorus. Secondary follicles may reach 2.5 cm in siz
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| When does the primary oocyte complete meiosis I and what does it form? | 24 to 36 hours prior to ovulation, Cell division is unequal, forming one large cell (secondary oocyte) and a small polar body.
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| What does the secondary oocyte arrest in? | metaphase of Meiosis II.
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| What happens at ovulation? | the secondary follicle ruptures releasing the secondary oocyte still covered by the cumulus oophorus. These cells rearrange around the zona pellucida to form the corona radiata. The secondary oocyte enters the uterine tube. Meiosis II resumes and compl
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| What is fetal programming? | Epigenetic alterations to chromatin structure
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| What is Epigenetics ? | It is the process where non genetic factors regulate gene expression thus altering an individuals phenotype. Involve DNA methylation and or histone modification which change which genes are expressed
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