Term
| when does human development begin? |
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Definition
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Term
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Definition
| a highly specialized totipotent cell which marks the beginning of each of us as a unique individual; contains chromosomes and genes derived from mother and father |
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Term
| the stages and duration of pregnancy are calculated starting at what point in time? |
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Definition
| the commencement of the mother's last normal menstrual period, which is approx. 14 days before conception occurs |
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Term
| the sperm and oocyte contain ____ the number of chromosomes present in somatic (body) cells. |
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Definition
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Term
| what is meiosis in general? |
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Definition
a special type of cell division that occurs during gametogenesis
takes place in germ cells only
involves 2 meiotic cell divisions |
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Term
| what is spermatogenesis in general? |
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Definition
| gamete maturation in males |
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Term
| what is oogenesis in general? |
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Definition
| gamete maturation in females |
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Term
| describe what occurs during gametogenesis |
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Definition
| the chromosome number is reduced by half and the shape of the cells is altered |
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Term
| describe the 1st and 2nd meiotic divisions |
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Definition
1st: reduction division because the chromosome number is reduced from diploid to haploid by pairing of homologous chromosomes in prophase and their segregation at anaphase
2nd: follows the 1st division without a normal interphase; each chromosome divides and each half, or chromatid, is drawn to a different pole |
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Term
| what does meiosis allow for? |
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Definition
provides constancy of the chromosome number from generation to generation by reducing the chromosome number from diploid to haploid, thereby producing haploid gametes
allows random assortment of maternal and paternal chromosomes between the gametes
relocates segments by crossing over of chromosome segments which shuffles the genes and produces a recombination of genetic material |
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Term
| how many chromosomes does a spermatogonium have? |
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Definition
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Term
| how many chromosomes does a primary spermatocyte have? |
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Definition
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Term
| how many chromosomes does a secondary spermatocyte have? |
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Definition
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Term
| which are the largest germ cells in the seminiferous tubules? |
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Definition
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Term
| spermatids are gradually transformed into four mature sperm by a process known as what? |
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Definition
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Term
| how long does the entire process of spermatogenesis take? |
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Definition
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Term
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Definition
| line the seminiferous tubules and support and nurture the germ cells and may be involved in the regulation of spermatogenesis |
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Term
| what is the function of the acrosome of a sperm? |
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Definition
a caplike saccular organelle containing several enzymes
when released these enzymes facilitate dispersion of the follicular cells of the corona radiata and sperm penetration of the zona pellucida during fertilization |
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Term
| what does the middle piece of sperm tail contain? |
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Definition
| mitochondria which provide ATP necessary for activity |
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Term
| when does oogenesis begin? |
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Definition
| begins before birth and is completed after puberty; continues to menopause |
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Term
| true or false: oogonia enlarge to form primary oocytes before birth |
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Definition
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Term
| what substance do the follicular cells surrounding the primary oocyte secrete? |
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Definition
| oocyte maturation inhibitor which keeps the meiotic process of the oocyte arrested |
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Term
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Definition
failure of paired chromatids to dissociate
occurs with increasing maternal age |
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Term
| do primary oocytes form after birth in females? |
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Definition
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Term
| describe the division of the primary oocyte |
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Definition
as a follicle mature, a primary oocyte increases in size and completes the first meiotic division to give rise to a secondary oocyte and the first polar body
the division of cytoplasm is unequal
the secondary oocyte receives all the cytoplasm and the first polar body receives very little |
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Term
| of the 40,000 primary oocytes in females how many become secondary oocytes and are expelled at ovulation during the reproductive period? |
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Definition
400
the number of oocytes that ovulate is greatly reduced in women who take oral contraceptives because the hormones in them prevent ovulation from occurring |
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Term
| describe the structure of the oocyte |
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Definition
massive cell compared with the sperm and is immotile
surrounded by a zona pellucida and a layer of follicular cells, the corona radiata
has abundance of cytoplasm containing yolk granules for nutrition to the dividing zygote |
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Term
| describe the structure of the uterus |
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Definition
thick walled, pear shaped muscular organ
body is the expanded superior 2/3
cervix is the cylindrical inferior 1/3
body narrows from the fundus to the isthmus |
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Term
| where do the external and internal os communicate? |
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Definition
internal os communicates with the cavity of the uterine body
the external os communicates with the vagina |
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Term
| what are the 3 layers of the wall of the body of the uterus? |
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Definition
perimetrium- the thin external layer
myometrium- the thick smooth muscle layer
the endometrium- the thin internal layer |
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Term
| what are the 3 layers of the endometrium? |
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Definition
compact layer- thin, densely packed connective tissue around the necks of the uterine glands
spongy layer- composed of edematous connective tissue containing the dilated, tortuous bodies of the uterine glands
basal layer- containing the blind ends of the uterine glands |
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Term
| which layers of the endometrium form the functional layer and disintegrate during menstruation and after delivery of a baby? |
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Definition
| the compact and spongy layers |
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Term
| what are the 4 parts of the uterine tubes? |
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Definition
| the infundibulum, the ampulla, the ishtmus, and the uterine part |
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Term
| where is GnRH synthesized and what does it cause release of? |
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Definition
synthesized by neurosecretory cells in the hypothalamus and is carried by the hypophysial portal system to the anterior lobe of the pituitary gland
stimulates the release of FSH and LH |
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Term
| what does FSH stimulate the production of? |
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Definition
| stimulates the development of ovarian follicles and the production of estrogen by the follicular cells |
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Term
| what does LH stimulate the production of? |
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Definition
| serves as a trigger for ovulation and stimulates the follicular cells and corpus luteum to produce progesterone |
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Term
| development of an ovarian follicle is characterized by what features? |
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Definition
growth/differentiation of primary oocyte
proliferation of follicular cells
formation of zona pellucida
development of the theca folliculi |
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Term
| as a primary follicle increases in size, the adjacent connective tissue organizes into a capsule, the theca folliculi. the theca soon differentiates into what 2 layers? |
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Definition
the theca interna and theca externa
thecal cells are thought to produce an angiogenesis factor that promotes growth of blood vessels in the theca interna |
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Term
| what marks the formation of a secondary follicle? |
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Definition
| the formation of an antrum |
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Term
| ovulation is triggered by what? |
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Definition
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Term
| what does estrogen regulate? |
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Definition
| regulates development and function of the reproductive organs |
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Term
| what is the principal mechanism leading to ovulation? |
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Definition
| enzymatic digestion of the follicular wall |
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Term
| what are the 3 glycoproteins found in the zona pellucida? |
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Definition
ZPA, ZPB, ZPC
usually form a network of filaments with multiple pores |
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Term
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Definition
a variable amount of abdominal pain which accompanies ovulation in some women
ovulation results in slight bleeding into the peritoneal cavity which results in sudden constant pain in the lower abdomen
can be used as a symptom of ovulation but there are better symptoms such as a slight drop in basal body temperature |
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Term
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Definition
some women do not ovulate because of an inadequate release of gonadotropins
ovulation can be induced by administration of gonadotropins or an ovulatory agent such as clomiphene citrate which stimulates the release of FSH and LH |
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Term
| what does the corpus luteum secrete? |
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Definition
| progesterone and estrogen causing the endometrial glands to secrete and prepare the endometirum for implantation of the blastocyst |
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Term
| degeneration of the corpus luteum is prevented by which hormone? |
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Definition
| hCG- secreted by the syncytiotrophoblast of the blastocyst |
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Term
| if the oocyte is not fertilized, how many days after ovulation does it take for the corpus luteum to degenerate? |
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Definition
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Term
| what is menopause and when does it occur? |
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Definition
| the permanent cessation of menstruation between the ages of 48 and 55 |
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Term
| how long is the average menstrual cycle? |
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Definition
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Term
| what occurs during the menstrual phase of the menstrual cycle? |
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Definition
the functional layer of the uterine wall is sloughed off and discarded with the menstrual flow
the blood discharged through the vagina is combined with small pieces of endometrial tissue |
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Term
| what occurs during the proliferative phase of the menstrual cycle? |
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Definition
lasts about 9 days, coincides with growth of ovarian follicles and is controlled by estrogen secreted by these follicles
there is a 2-3 fold increase in the thickness of the endometrium and in its water content during the phase of repair and proliferation
early during the phase the surface epithelium reforms and covers the endometrium
glands increase in number and length and the spiral arteries elongate |
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Term
| what occurs during the luteal phase of the menstrual cycle? |
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Definition
lasts approximately 13 days, coincides with the formation, functioning, and growth of the corpus luteum
progesterone produced by the corpus luteum stimulates the glandular epithelium to secrete a glycogen-rich material
spiral arteries grow into the superficial compact layer and become increasingly coiled
venous network becomes complex and large lacunae develop
direct arteriovenous anastomoses are a prominent feature of this stage |
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Term
| what happens if fertilization does not occur? |
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Definition
the corpus luteum degenerates
estrogen and progesterone levels fall and the secretory endometrium enters an ischemic phase
menstruation occurs |
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Term
| describe the ischemic phase of the menstrual cycle in general |
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Definition
occurs as spiral arteries constrict, giving the endometrium a pale appearance
hormone withdrawal results in stoppage of glandular secretion, a loss of interstitial fluid and a marked shrinking of the endometrium
results in a loss of 20-80 mL of blood
the entire compact layer and most of the spongy layer of the endometrium are discarded in the menses |
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Term
| what happens if fertilization does occur? |
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Definition
cleavage of the zygote and blastogenesis
the blastocyst begins to implant in the endometrium on approximately the sixth day of the luteal phase
hCG, produced by the syncytiotrophoblast keeps the corpus luteum secreting estrogens and progesterone
the luteal phase continues and menstruation does not occur |
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Term
| what is the function of the fimbriae on the uterine tube? |
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Definition
move back and forth over the ovary
the sweeping action of the fimbriae and fluid currents produced by the cilia of the mucosal cells of the fimbriae sweep the secondary oocyte into the funnel-shaped infundibulum of the uterine tube |
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Term
| what enzyme, produced by the seminal glands, coagulates some of the semen or ejaculate and forms a vaginal plug which prevents backflow of semen into the vagina? |
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Definition
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Term
| what happens during capacitation of sperm? |
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Definition
a glycoprotein coat and seminal proteins are removed from the surface of the sperm's acrosome
the membrane components of the sperms are extensively altered
sperm are more active
occurs in the uterus or uterine tube |
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Term
| sperm accounts for what percent of semen? |
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Definition
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Term
| what is found in male infertility? |
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Definition
fewer than 10 million sperms per milliliter of semen is likely to be sterile
50% of sperms should be motile after 2 hours and some should be motile after 24 hours
may result from a low sperm count, poor sperm motility, medications, endocrine disorders, smoking, pollutants, etc. |
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Term
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Definition
| when 2 sperm participate in fertilization of an oocyte |
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Term
| triploid embryos have how many chromosomes? |
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Definition
69 chromosomes
may appear normal but they nearly always abort
have severe intrauterine growth restriction and disproportionately small trunks |
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Term
| where is the usual site of fertilization? |
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Definition
| the ampulla of the uterine tube |
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Term
| what are the phases of fertilization? |
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Definition
passage of sperm through the corona radiata
penetration of the zona pellucida
fusion of plasma membranes of the oocyte and sperm
completion of the second meiotic division of oocyte and formation of female pronucleus
formation of the male pronucleus
as the pronuclei fuse into a single diploid aggregation of chromosomes, the ootid becomes a zygote |
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Term
| what is early pregnancy factor? |
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Definition
an immunosuppressant protein which is secreted by the trophoblastic cells and appears in the maternal serum within 24 to 48 hours after fertilization
forms the basis of a pregnancy test during the first 10 days of development |
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Term
| what are the cells that formed by repeated mitotic divisions of the zygote? |
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Definition
blastomeres
become smaller with each successive cleavage division
normally occurs as the zygote passes along the uterine tube toward the uterus
begins approx. 30 hours after fertilization |
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Term
| describe compaction of blastomeres |
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Definition
after the nine cell stage, the blastomeres change their shape and tightly align themselves against each other to form a compact ball of cells
mediated by cell surface adhesion glycoproteins
permits greater cell to cell interaction and is a prerequisite for segregation of the internal cells that form the inner cell mass or embryoblast of the blastocyst |
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Term
| when there are 12 to 32 blastomeres the developing human is called what? |
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Definition
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Term
| how long after fertilization does the blastocyst attach to the endometrial epithelium? |
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Definition
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Term
| how many days after fertilization does it take for the hypoblast to appear on the surface of the embryoblast facing the blastocytic cavity? |
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Definition
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