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WEEK 3:
Embryology 1:
| Question | Answer |
|---|---|
| cervix | duct connecting uterus + vagina, produces mucus liquid |
| fimbriae | transfer ovum from ovaries to the fallopian tube/ oviduct |
| ovum | mature ovulated egg |
| fertilisation | fusion of sperm + ovum = zygote, usually taking 24 hours |
| ampulla | longest + widest part of fallopian tube, usual site of fertilisation |
| implantation site | upper + posterior wall in the midsagittal plane of uterus, completes at 2 weeks |
| sites for ectopic (abnormal) implantation sites | (5) fallopian tubes (97%), uterine cornua (2.5%), ovaries, cervix, abdomen |
| uterine cornua | upper points of uterus where fallopian tubes connect |
| layers in ovum | zona pellucida + corona radiata |
| zona pellucida | glycoprotein matrix barrier to sperm |
| corona radiata | external layer of follicular cells providing support + nourishment to ova cells |
| cells in ovum | contains cortical granules which release contents upon fertilisation to prevent polyspermy |
| ovum organalles | cytoplasm + haploid nucleus |
| spermatozoa head parts | haploid nucleus, acrosome cap, and paired centrioles |
| acrosome cap in spermatozoa | contains hydrolytic enzymes to penetrate ovum zona pellucida |
| paired centrioles in spermatozoa | helps zygote divide |
| middle piece spermatozoa | many mitochondria providing ATP for movement |
| flagellum of spermatozoa | made of microtubule (axoneme) which bends to facilitate movement |
| male gametogenesis | spermatogenesis |
| female gametogenesis | oogenesis |
| spermatogenesis definition | sperm produced in seminiferous tubules of testes regulated by hypothalamus + pituitary gland hormones |
| how many stages of spermatogenesis | three |
| first stage of spermatogenesis (mitosis) | mitotic division of spermatogonial stem cells producing more cells |
| second stage of spermatogenesis (meiosis) | (1- spermatogonia mature into primary spermatocytes) (2- primary spermatocytes -> meiosis I -> secondary spermatocytes) (3- secondary spermatocytes -> meiosis II -> 4 spermatids) |
| third stage of spermatogenesis (spermiogenesis) | spermatids differentiate into mature spermatozoa |
| oogenesis definition | eggs produced from germ cells within ovary |
| first stage of oogenesis (mitosis) | primary germ cells migrate to fetal ovary becoming oogonia, which then divide rapidly through mitosis to increase numbers |
| second stage of oogenesis (meiosis I) | (1- oogonia -> meiosis I -> primary oocytes arrested in prophase I of meiosis until puberty) (2- puberty: primary oocytes resume meiosis I with each menstrual cycle) (3- primary oocyte completes meiosis I -> secondary oocyte + non-functional polar body) |
| third stage of oogenesis (meiosis II) | (1- secondary oocyte -> meiosis II (arrested in metaphase II) + released from ovary during ovulation) (2- meiosis II only completed when secondary oocyte fertilised -> mature ovum) |
| biological stages from fertilisation - foetus development? | three - pre-embryonic/ germinal, embryonic and foetal period |
| germinal/ pre-embryo period | first two weeks, zygote repeatedly self-replicates (first division = morula then blastula) |
| embryo period | from third week- eighth week, gastrulation (get germ layers) occurs, rounded shape + cells in 3 layers (ectoderm, mesoderm + endoderm) |
| foetus period | from ninth week- birth, begins to look human-like + develop features |
| morula stage of pre-embryo/ germinal period | around fourth day, 16 cell stage, made of blastomeres, surrounded by zona pellucida |
| blastula stage of pre-embryo/ germinal period | around fifth day, different cell types with central cavity, made of differentiated blastomeres |
| gastrulation meaning | embryo gets three germ layers |
| stages of fertilisation | sperm penetration of corona radiata, sperm binding + penetrating zona pellucida, fusion of sperm + oocyte cell membranes (syngamy) + nucleus |
| sperm penetration of corona radiata | sperm prepares by physiologically changing (capacitation) by increasing motility to penetrate egg layers |
| sperm binding + penetration of zona pellucida | acrosome reaction occurs (enzymes break down zona pellucida) so sperm can go deeper causing egg to undergo cortical reaction (releasing substances to make zona pellucida harden to stop sperm entering/ polyspermy) |
| fusion of sperm + oocyte cell membranes + nucleus | sperm membranes fuse with egg's plasma membrane allowing sperm's nucleus to enter egg's cytoplasm so sperm + egg nucleus fuse to combine genetic material = zygote) |
| what does the oocyte + sperm provide during fertilisation | (oocyte: cytoplasm containing nutrients + organelles) (sperm: centriole needed to form centrosome) |
| cleavage | rapid mitotic cell zygote divisions into smaller cells (blastomeres) without changing cytoplasmic volume - making morula + blastula |
| morulation | cleavage/ segmentation of ovum forming morula around 16-cell stage |
| how does morula become blastocyst/ blastula | zona pellucida in morula undergo 'compaction' (tight junctions between surface cells) and splits causing cavity to develop + cells begin to differentiate |
| embryoblast | inner cell mass of blastocyst |
| trophoblast | outer cell layer of blastocyst |
| order of development after zygote | cleavage (2), further cleavage (4), morula + compaction, blastocyst |
| difference in time for fertilisation + implantation | fertilisation = 24 hours, implantation = 2 weeks |
| difference between occurrence of spermatogenesis + oogenesis | spermatogenesis = at puberty, oogenesis = eggs made during embryo development |
| hatching | zona pellucida degenerates in morula to become blastocyst |
Created by:
kablooey
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