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bio 30 > mod 4: From Fertilization to Birth > Flashcards

mod 4: From Fertilization to Birth Flashcards

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Biology 101 flashcards
1
Q

implantation (definition)

A

burrowing of the blastocyst into the wall of the endometrium of the uterus

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2
Q

embryo (definition)

A

the organism in the stages of development from the time the zygote begins cleavage until nine weeks of gestation, when the embryo becomes a fetus

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3
Q

fetus (definition)

A

the organism in the stages of development from nine weeks until birth

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4
Q

extra-embryonic membranes (general definition, list)

A

membranes surrounding the embryo that support its development in different ways. includes the allantois, amnion, chorion, and yolk sac

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5
Q

monozygotic twins (definition)

A

“identical twins”. formed when the embryonic mass produced by the union of one egg and one sperm splits into two separate, identical masses. always of the same sex

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6
Q

zygote (definition)

A

the one-celled product of an egg and sperm fusion. a fertilized egg

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7
Q

fertilization process (step by step description)

A

1) sperm (several hundred million per ejaculation) exit the penis and enter the vagina.
2) the sperm enter the uterus through the cervix and make their way up to the oviducts–some will enter the oviduct that does not contain an egg.
3) the sperm (only a few dozen to a few hundred) reach the egg cell. they meet the outer layer of the egg–the corona radiata.
4) the sperm releases the enzymes within its acrosome, which digest a path through the corona radiata and the the zone pellucida beneath it. the action of many sperm may be needed to open a pathway for a single sperm.
5) the sperm enters the egg, causing the egg’s membrane to depolarize and prevent the entrance of additional sperm.
6) the nuclear membranes of the sperm and egg disappear and the nuclei combine, completing the process and resulting in a zygote

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8
Q

cleavage (description)

A

occurs after fertilization within the oviduct. the process of cell division without enlargement. when the zygote cleaves into 16 cells it is called a morula

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9
Q

morula (definition)

A

undifferentiated mass of 16 cells. developed from a zygote through cleavage

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10
Q

blastocyst (definition, formation)

A

embryo at the stage where it consists of a nearly hollow ball of cells that is made up of two groups of cells: the trophoblast and inner cell mass. develops from the morula when it enters the uterus and fluid from the uterus diffuses into the morula, creating an open space within it. the trophoblast is the outer layer and will form the chorion while the inner cell mass is attached to the inside of the trophoblast and will form the baby

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11
Q

implantation process (description)

A

between the fifth and seventh day after fertilization the blastocyst attaches to the endometrium. the trophoblast secretes enzymes that digest some of the tissues and blood vessels of the endometrium, causing the blastocyst to sink into uterine wall. this is complete within two weeks after fertilization. at this point, the person is considered pregnant

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12
Q

hCG (function, secreted by)

A

“human chorionic gonadotropin”. same effects as LH so it maintains the corpus luteum past the tome when it would normally degenerate, resulting in continued secretion of estrogen and progesterone that maintains the endometrium and prevents menstruation.

secreted by the trophoblast at a high level for two month and then gradually declines to a low level by four months

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13
Q

gastrulation (definition)

A

the folding and differentiation of the embryonic disc into three germ layers, forming the embryonic stage called the gastrula.

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14
Q

blastocyst to gastrula process (timing, description)

A

occurs during second week after fertilization.

the amniotic cavity forms between the cell mass and blastocyst and the inner cell mass flattens into the embryonic disc, which is supported by a short stalk that connects the blastocyst to the endometrium. the embryonic disc consists of three primary germ layers: the endoderm, mesoderm, and ectoderm (in order from inner to outer).

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15
Q

morphogenesis (definition)

A

development of body organs and structures. begins with gastrulation

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16
Q

differentiation (definition)

A

the turning on and off of genes in a cell. results in specialized cell functions

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17
Q

neurulation (definition, process)

A

the process of forming the embryo’s neural tube, which will develop into the brain and spinal cord.

thickened band of mesoderm cells develops along the back of the embryonic disc along where the baby’s back will be. they come together to form a rod-like structure called the notochord, which will form the basic framework of the skeleton. the nervous system develops from the ectoderm just above the notochord. cells on the surface above the notochord begin to thicken, folds develop and then fuse, forming the neural tube

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18
Q

allantois (definition)

A

extra-embryonic membrane that forms the foundation for the umbilical cord, which the connects the fetus with the placenta. forms part of the bladder

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19
Q

amnion (definition)

A

extra-embryonic membrane that is a closed, fluid-filled sac surrounding the developing organism. protects the organism from impact and temperature change. formed from cells of the embryonic disc

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20
Q

chorion (definition)

A

extra-embryonic membrane that is the outermost layer of the embryo. develops from the trophoblast and forms the fetal portion of the placenta

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21
Q

yolk sac (definition)

A

extra-embryonic fluid that produces the first blood cells and gametes and contributes to the formation of the digestive tract

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22
Q

placenta (location, definition, timing)

A

embedded in the endometrium. provides a location where nutrients, gases, wastes, and hormones can be exchanged between fetal and maternal blood pools. full developed by about 10 weeks

23
Q

ectopic pregnancy (definition)

A

occurs when implantation takes place in the oviduct

24
Q

events of week 1 (list)

A
  • formation of the zygote into a morula (cleavage)
  • formation of the morula into a blastocyst
  • beginning of implantation of the blastocyst
  • trophoblast starts to secrete hCG
25
Q

events of week 2 (list)

A
  • completion of implantation of the blastocyst
  • formation of the amnion between the inner cell mass and trophoblast
  • formation of the inner cell mass into the embryonic disc
  • formation of the three primary germ layers in the embryonic disc (gastrulation, formation of the gastrula)
  • morphogenesis begins
  • extension of finger-like projections of the chorion into uterine lining, establishing the beginnings of the placenta
26
Q

events of week 3 (list)

A
  • formation of the notochord
  • formation of the neural tube (neurulation)
  • heart forms and stars beating
27
Q

events of week 4 (list)

A
  • blood cells start to form and fill developing blood vessels
  • lungs and kidneys take shape
  • formation of small buds that will develop into arms and legs
  • distinct head is visible. clear evidence of eyes, ears, and nose
    NOTE: at this point the period is two weeks late–the person may start to suspect they are pregnant
28
Q

events of week 5 (list)

A
  • opening of eyes but lack of eyelids or irises

- rapid differentiation of brain cells

29
Q

events of week 6 (list)

A
  • continued rapid differentiation of brain cells
  • lengthening and slight flexing of limbs
  • production of hormones that will influence development of external genitalia by the gonads
30
Q

events of weeks 7 and 8 (list)

A
  • embryo has distinct human characteristics
  • organs are formed
  • nervous system starting to coordinate body activity
  • eyes are well developed but eyelids are stuck closed
  • nostrils are developed but plugged
  • external genitalia are still forming but not yet differentiated
31
Q

trimester (definition)

A

one-third of the gestational period (one-third of the pregnancy)

32
Q

vernix (definition)

A

cheesy, oily substance covering the fetus. has antibacterial properties

33
Q

teratogen (definition)

A

a substance that can cause deformities during fetal development. can be a chemical, virus, or radiation. teratogens have more severe effects during the embryonic stage of development (differentiation) than before or after that stage.

34
Q

FASD (definition)

A

“fetal alcohol spectrum disorder”. permanent syndrome of birth defects caused by maternal intake of alcohol during pregnancy. includes disorders of growth, behaviour, and cognitive abilities.

35
Q

parturition process (definition, description)

A

childbirth/labour.

1) estrogen increases the ability of the uterus to contract and lessens the effect if progesterone, which relaxes uterine muscles so they aren’t contracting continually, to prevent premature birth. sharp drop in progesterone causes the body to prepare for labour
2) fetal cells produce oxytocin, which releases prostaglandins, both of which produce intense, frequent contractions that initiate labour. the placental produces relaxin, relaxing the pelvic ligaments in the pubic bone, allowing it to shift so there’s more room for the baby to exit
3) the baby pushes down on the cervix to begin to exit (usually head first). pressure receptors of the cervix detect this and stimulate the hypothalamus and pituitary, causing the posterior pituitary to release oxytocin, which travels through the blood to uterine muscles
4) afterbirth: the placenta is delivered, usually within 30 minutes of actual birth.

36
Q

lactation process (description)

A

prolactin, which control milk production, is not secreted during pregnancy due to high estrogen and progesterone levels. prolactin production begins after birth and milk production starts within a few days. before then, breasts secrete colostrum (thin, yellowish fluid similar to milk but with more protein and less fat). suckling of the baby stimulates nerve endings in the nipple and areola, which travel to the hypothalamus, stimulating secretion of oxytocin, which causes contractions within the mammary lobules. cease or lack of suckling causes milk production to stop within a few days

37
Q

folate (definition)

A

“folic acid”. vitamin B9. ingestion prior to and during pregnancy prevents neural tube defects

38
Q

dilation stage (pregnancy) (definition)

A

stage one of three. stretching and opening of the cervix to 10 cm to allow passage of the fetus during expulsion.

39
Q

expulsion stage (pregnancy) (definition)

A

stage two of three. smooth muscle walls of the uterus contract in rhythmic cycles to deliver the fetus from the vagina.

40
Q

placental stage (pregnancy) (definition)

A

“afterbirth”. stage three of three. further uterine contractions push the placenta out through the vagina.

41
Q

prostaglandin (definition, function)

A

group of hormones that contribute to parturition by thinning the cervix and increasing contraction of the uterus.

42
Q

colostrum (definition)

A

rich, yellowish secretion from the mammary glands that occurs in the few days prior to secretion of milk. contains more proteins and less fat than milk does. contains antibodies like milk does.

43
Q

reproductive technology (definition)

A

any application of human intelligence that increases or decreases reproductive potential

44
Q

family planning (definition)

A

natural birth control that consists of avoiding sex during the fertile period around ovulation, which can be tested for by small increase in core temperature. not very effective

45
Q

tubal litigation (definition)

A

permanent female sterilization in which the Fallopian tubes are cut and sealed to prevent further ova from passing from the ovaries to the site of fertilization

46
Q

vasectomy (definition)

A

permanent male sterilization in which the ductus deferens are cut and sealed to prevent sperm from passing from the epididymus into the semen

47
Q

IVF (definition)

A

“in vitro fertilization”. process in which multiple eggs harvested from a female are combines with sperm in the lab and the resulting embryo is implanted into the mother or surrogate mother. used in cases of female infertility

48
Q

amniocentesis (definition)

A

fetal diagnostic technique where a syringe is inserted through the mother’s abdominal and uterine alls to extract a sample of amniotic fluid, which contains sloughed-off embryonic cells. used to karyotype the embryo

49
Q

CVS (definition)

A

“chorionic villi sampling”. fetal diagnostic technique done by pinching off a small sample of chorionic villus (done vaginally). used to karyotype the embryo because chorion cells are embryonic

50
Q

cordiocentesis (definition)

A

process of sampling fetal blood from the umbilical cord to test for possibility of infection or blood disease

51
Q

first trimester developments (list)

A
  • embryonic development is completed and fetal begins
  • growth of body accelerates but growth of head slows
  • cartilage-based skeleton begins to harden
  • external organs are distinguishable as male or female by the end
52
Q

second trimester developments (list)

A
  • heartbeat of the fetus is loud enough to be heard with a stethoscope
  • bones of skeleton begin to form
  • legs grow and develop
  • mother begins to feel movement
  • fetus becomes covered with lanugo (fine, soft hair)
  • skin appears wrinkled because there is very little fat
  • skin appears more pink due to blood-filled capillaries extending into it
  • fetus born prematurely at this stage is unlikely to survive, even if supported by machines
53
Q

third trimester developments (list)

A
  • fetal brain cells form rapidly
  • testes descend into scrotum
  • layer of fat develops beneath skin
  • digestion and respiratory systems are last to mature
  • nutrition is especially important because poor nutrition can damage the placenta, which can lead to low birth weight, short stature, delayed sexual developments, and learning disabilities

bio 30 (8 decks)

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