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87 Cards in this Set
- Front
- Back
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First 2 weeks after fertilization of egg/formation of zygote
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pre-embryonic period
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Third through eighth weeks when all major organ systems begin to develop
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embryonic period
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Ninth through thirty-eighth weeks when growth dominates; fetal period ends at birth
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fetal period
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Embryogenesis
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fertilization to birth
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What occurs in human development after birth?
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maturation of body and reproductive organs; production of sex cells (gametes), eggs or sperm
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The production of eggs or sperm is known as...
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gametogenesis
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Gametes are haploid which means...
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they contain 23 chromosomes
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Reproductive organs produce haploid cells by...
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meiosis
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Parent cells that produce diploid primary oocytes through mitosis are...
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oogonia
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Primary oocytes are located in the ovaries and enter prophase I during...
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fetal development
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What stops in females until puberty?
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oogenesis
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Monthly, after puberty, a number of primary oocytes begin to mature by resuming...
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meiosis I
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Meiosis I produces two daughter cells but cytokinesis...
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divides the cells unequally
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The smaller cell that dies is known as...
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polar body
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The larger cells is the haploid ______ ______, which stops developing at metaphase II and will be _______.
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secondary oocyte; ovulated
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Meiosis II produces...
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two daughter cells with uneven division of cytoplasm
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The larger cell, containing 23 chromosomes that will combine with the 23 provided by the sperm that fertilized it is known as...
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ovum
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What happens if the secondary oocyte is not fertilized?
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it degenerates in about 24 hours
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The secondary oocyte is expelled from the ovary with what two surrounding structures?
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corona radiata, zona pellucida
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Several layers of cuboidal cells
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corona radiata
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A clear layer of proteins on the ovum under the corona radiata
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zona pellucida
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_____ must penetrate both structures in order to fertilize the ovum
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sperm
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Where does spermatogenesis take place?
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testes of the male
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Parent cells that produce diploid primary spermatocytes through mitosis are...
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spermatogonia
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Each primary spermatocyte undergoes meiosis I producing...
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two haploid secondary spermatocytes containing 23 chromosomes
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Each secondary spermatocyte will undergo meiosis II to produce two spermatids for a total of 4...
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spermatids
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Spermatids must undergo further changes called ______ to become ____ _____.
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spermiogenesis; immature sperm
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Immature sperm then move to the ________ to mature.
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epididymis
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Mature sperm must undergo ________ or conditioning in the vagina to change the membrane of the ______, a membranous cap at the head of the sperm.
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capacitation; acrosome
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The acrosome contains _______ that will be released upon contact with the cells of the corona radiate and facilitate the penetration of the sperm's nucleus into the cytoplasm of the egg.
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digestive enzymes
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Fusion of sperm and secondary oocyte
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fertilization
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Where does fertilization usually occur?
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upper 1/3 of the uterine tube
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Nucleus of the ovum fuses with..
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nucleus of sperm
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The resulting single diploid cell is the...
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zygote
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Two or more sperm may penetrate the egg's cytoplasm, a condition called ______ that is immediately fatal
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polyspermy
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Series of mitotic divisions
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cleavage
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16-cell stage organism
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morula
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Week 1, one to two days after the morula enters the uterine cavity, it develops a fluid filled cavity in its center called...
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blastocyst cavity and the organism is now a blastoyst
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Week 1. Shortly after blastocyst format, differentiation forms two regions:
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trophoblast-outer ring of cells that will develop into the chorion
embryoblast-cluster of tightly packed cells inside one portion of the trophoblast |
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Cells of the inner cell mass are...
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pluripotent
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What happens to the zona pellucida at the end of the first week after fertilization?
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degrades
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The cells that line the inside of the uterus form a layer called the...
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endometrium
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What happens during week 2?
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implantation takes place; extra embryonic membranes are formed; placenta is formed
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What two layers does the endometrium consist of?
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deep basal layer & superficial functional layer
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Blastocyst invades the functional layer and its trophoblast turns into two layers:
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cytotrophoblast & syncytiotrophoblast
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By day 8, the cells of the embryoblast differentiate into two distinct types:
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hypoblast-layer of small cuboidal cells facing the blastocyst cavity
epiblast-layer of columnar cells deep to the hypoblast |
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The hypoblast and epiblast form a flat disc called the...
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bilaminar germinal disc
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The bilaminar germinal disc and trophoblast produce 3 extra embryonic membranes:
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yolk sac, amnion, chorion
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Formed from and continuous withe hypoblast layer
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yolk sac
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It does not store yolk in humans but does serve as a site for...
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early blood cell and vessel formation
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Thin layer of cells that forms above and is derived from the epiblast
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amnion
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A fluid filled _____ _____ appears between the amnion and epiblast layer.
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amnionic cavity
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The fluid is produced by the cells of the amnion and will protect the embryo from...
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drying out
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The outermost membrane and is formed by the rapidly expanding syncytiotrophoblast and cytotrophoblast
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chorion
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What is the major function of the chorion?
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formation of the placenta
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Highly vascularized organ that serves as a physical and biochemical interface between embryo and mother
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placenta
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What are the 3 main functions of the placenta?
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exchange of nutrients, waste products, and blood gases between embryo and mother; transmission of maternal antibodies to the embryo; production of many hormones predominantly estrogen and progetherone
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The embryonic portion of the placenta is the...
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chorion
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The maternal portion is from the functional layer of the…
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endometrium
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The early embryo is attached to the placenta by a structure called the...
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connecting stalk
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The connecting stalk will develop into the...
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umbilical cord
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What is transmitted through the umbilical cord?
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umbilical arteries & veins
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Fingerlike projections that appear at the leading edge of the chorion
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chorionic villi
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The villi project into the...
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functional layer of the endometrium
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Inside the villi are...
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branches from umbilical blood vessels
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Outside the villi is...
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maternal blood
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Where does metabolic exchange in the placenta occur?
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across the wall of the villi
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What forms during week 3?
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primary germ layers
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What has developed by the end of week 3?
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main organ systems
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Once all 3 germ layers are present, the trilaminar structure can be called an...
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embryo
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Cells from the epiblast layer move through the primitive streak to locate themselves between the...
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epiblast and hypoblast layers
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The cells between the epiblast and hypoblast layers become the primary germ layer known as...
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mesoderm
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Other migrating cells displace the hypoblast cells and become...
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endoderm
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Cells remaining in the epiblast will become...
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ectoderm
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All 3 germ layers are derived from the...
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epiblast
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Where is the ectoderm located?
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on the external surface of the embryo
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What 3 structures will the ectoderm eventually develop into?
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epidermis of the skin, derivatives of epidermis, nervous system
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Thickening of the overlying ectoderm forms a...
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neural plate
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The lateral edges of the neural plate form...
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neural folds
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The depression between the folds is the...
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neural groove
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The neural folds approach midline and fuse to form the...
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neural tube
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Develops into many internal structures following the foldings of the embryo
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endoderm
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The process of constructing the organs of the body
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organogenesis
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Rudimentary forms of most organ systems are complete by...
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the end of the embryonic period
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During this period normal development of organs can be interfered with by agents called...
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teratogens
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What is a teratogen?
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any agent that can cause congenital malformations/birth defects
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Characterized by maturation and growth of tissues and organs
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fetal period week 9-38
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