week 11 - fetus stuff Flashcards
oogenesis
Egg production in the ovaries
spermatogenesis
Sperm production in the testes
fertilization
a) usual site
Fallopian tubes
b) time when event occurs in relation to ovulation
After ovulation
c) structural component(s) which are involved and are formed
Sperm and egg
d) purpose
To produce humans
fertilization
a) penetration of the corona radiata and zona pellucida
For fertilization to occur, a sperm cell first must penetrate two layers: the corona radiata (the granulosa cells that surround the secondary oocyte), and the zona pellucida (the clear glycoprotein layer between the corona radiata and the oocyte’s plasma membrane)
b) production of the female pronucleus
Once a sperm cell enters a secondary oocyte, the oocyte first must complete meiosis II. It divides into a larger ovum (mature egg) and a smaller second polar body that fragments and disintegrates. The nucleus in the head of the sperm develops into the male pronucleus, and the nucleus of the fertilized ovum develops into the female pronucleus
c) production of the diploid nucleus of the zygote
After the male and female pronuclei form, they fuse, producing a single diploid nu-cleus, a process known as syngamy. Thus, the fusion of the haploid (n) pronuclei restores the diploid number (2n) of 46 chromosomes. The fertilized ovum now is called a zygote
cleavage
a) usual site
Fallopian tubes
b) time when event occurs in relation to ovulation
Will happen after ovulation
c) structural component(s) which are involved and are formed
Cleavage is a period after fertilization, when a 1-cell embryo starts developing into a multicellular organism.
d) purpose
To start the development of the fetus
events of cleavage
The first division of the zygote begins about 24 hours after fertilization and is completed about 6 hours later. Each succeeding division takes slightly less time. By the second day after fertilization, the second cleavage is completed and there are four cells. By the end of the third day, there are 16 cells. The progressively smaller cells produced by cleavage are called blastomeres. Successive cleavages eventually produce a solid sphere of cells called the morula.When the morula enters the uterine cavity on day 4 or 5, a glycogen-rich secretion from the glands of the endometrium of the uterus passes into the uterine cavity and enters the morula through the zona pellucida. This fluid, called uterine milk, along with nutrients stored in the cytoplasm of the blastomeres of the morula, provides nourishment for the developing morula. At the 32-cell stage, the fluid enters the morula, collects between the blastomeres, and reorganizes them around a large fluid-filled cavity called the blastocyst cavity Once the blastocyst cavity is formed, the developing mass is called the blastocyst. Though it now has hundreds of cells, the blastocyst is still about the same size as the original zygote.
implantation
a) usual site
uterus
b) time when event occurs in relation to ovulation
after ovulation during the secretory phase
c) structural component(s) which are involved and are formed
zygote
d) purpose
Fetus will remain there until birth important for the nutriations of the fetus
blastocyte
a) its two major components
embryoblast and trophoblast
b) the structures into which each component identified in (a) will develop
The embryoblast or inner cell mass, is located internally and eventually develops into the embryo.
trophoblast is the outer superficial layer of cells that forms the spherelike wall of the blastocyst. It will ultimately develop into the outer chorionic sac that surrounds the fetus and the fetal portion of the placenta
c) name and function of hormone secreted by outer layer
hcG - maintain the progesterone production of corpus luteum during early pregnancy
d) function of enzymes secreted by outer layer
TIMPs (1–3) - it plays a role in regulating the transcriptional profile of fetal and placental tissues associated with the early stages of pregnancy
proteseron secretion on myometrium and endometrium
Progesterone secretion on the myometrium is what will inhibit contractions of the muscles of the uterine wall, less contraction and more relaxation will help with implantation
reasons to why a time lapse is necessary between ferilixation and implation
The period of rest in the tube appears to be necessary for full development of the fertilized egg and for the uterus to prepare to receive the egg.
the urerine lining following implatation
The decidua basalis is the portion of the endometrium between the embryo and the stratum basale of the uterus; it provides large amounts of glycogen and lipids for the developing embryo and fetus and later becomes the maternal part of the placenta. The decidua capsularis is the portion of the endometrium located between the embryo and the uterine cavity. The decidua parietalis is the remaining modified endometrium that lines the non-involved areas of the rest of the uterus
increased estrogen and progesterone after pregnancy
The increase in estrogen during pregnancy enables the uterus and placenta to: improve vascularization (the formation of blood vessels) transfer nutrients. support the developing baby
emrbyo
a) definition of the term
the early developmental stage while it is in the egg or within the uterus of the mother.
b) time period during pregnancy to which term refers
from the 5th through the 10th week of pregnancy.
c) overall developmental changes which occur
Your baby’s major organs and body parts begin to take shape. The placenta forms during the embryonic stage.
fetus
a) definition of the term
an unborn offspring
b) time period during pregnancy to which term refers
10th week until birth
c) overall developmental changes which occur
All the body parts will take shape, sex organs will develop and it will be a baby by the time it comes out
primary germ layer systems
a) nervous system
ectoderm
b) integumentary system
mesoderm
c) cardiovascular system
mesoderm
d) musculoskeletal system
mesoderm
e) digestive system
mesoderm
f) respiratory system
mesoderm
development in first trimester
a) First month: Three primary germ layers have become differentiated. Body systems begin to form. Heart forms. CNS appears at the start of the third week.
b) Second month: Tissue differentiation into organs and systems continues / emphasis changes to growth and development of each system.
c) Third month: Centers of ossification have appeared in most bones. Heartbeat can be detected.
devlopment in 2nd trimester
e) Fifth month: Fetal heart may be heard. Fetal movement may be felt. Brown fat is deposited and is the site of heat production.
f) Sixth month: Fetal outline may be feltby the examiner. Lungs are not well-developed. Type II alveolar cells begin to produce surfactant. Increased utilization of iron for hematopoieses.
devleopment for 3rd tirmester
g) Seventh month: Testes descend into scrotum.
h) Eighth month: Weight gain is approximately 220 gm./week. Subcutaneous fat is deposited.
i) Ninth month: Weight gain is approximately 220 gm./week. Additional subcutaneous fat deposition has occurred.
j) Mid-tenth month: Weight gain is approximately 220 gm./week.
foramen ovvlae
a) location
a small hole located in the septum, which is the wall between the two upper chambers of the heart (atria)
b) function
makes it possible for the blood to go from the veins to the right side of the fetus’ heart, and then directly to the left side of the heart
ductus arteriosus
a) location
connects the left pulmonary artery near its origin to the descending aorta just distal to the left subclavian artery
b) function
carries blood away from the lungs and sends it directly to the body
ductus venosus
a) location
in the fetal liver connecting the umbilical vein directly to the caudal inferior vena cava or distal left hepatic vein
b) function
allows oxygenated blood in the umbilical vein to bypass the liver and is essential for normal fetal circulation
human chorionic gonadotropin
a) source(s) during embryological period
Will stimulate corpus lutem
b) source(s) during fetal period
plactena
estorgen after pregenecy
a) myometrium
Help with contraction, stimulate actin/myosin proteins
b) endometrium
Will renew the uterus lining every month until ureter is implanted into the wall
c) breast structures
Stimulates growth in milk ducts
d) external genitalia
increasing a normal clear discharge from the vagina and making the vulva and urethra healthy
progestoerone after pregency
a) myometrium
Will inhibit contractions, making it easier for implantation
b) endometrium
inhibits the proliferative activity of the endometrium
c) breast structures
stimulates the formation of the milk glands
d) external genitalia
human chorionoic smatomammotropin (hCS) or human placental lactogne (hPL)
a) breasts
lactation
b) maternal metabolism
modulates maternal metabolism to meet the energy requirements of the developing fetus.
c) fetal nutrition
In the fetus, it promotes the formation of insulin-like growth factor and growth factors believed to promote growth of most, if not all, fetal tissues
cortiocopropin-releasing hormone
a) source
hypothalamus
b) function(s) related to birth of the child
controls the placental “surveillance and response” system so that the fetus can detect threats to survival and adjust its developmental trajectory
controling prolactin
Anterior pituitary gland, causes the breasts to grow and make milk during pregnancy and after birth
a) inhibition during pregnancy
Dompiane
b) release after delivery
stimulation/ocytocin
c) release after milk production has begun
suckiling
d) inhibition after breastfeeding has begun
Dompaine
uterine stimulants (oxytocics)
medications given to cause a woman’s uterus to contract, or to increase the frequency and intensity of the contraction
uterine involutation
a physiological process by which the uterus turns to its pre-pregnancy dimensions with endometrial regeneration, reduced uterine blood flow and endometrial vascularity, and reduced muscle mass
pospartum hemorrhage
heavy bleeding after birth
- sperm transport and cpacitation
a physiological process by which the uterus turns to its pre-pregnancy dimensions with endometrial regeneration, reduced uterine blood flow and endometrial vascularity, and reduced muscle mass
list of steps ferilization
- sperm transport and cpacitation
- acrosomal reaction and spemr penetration
- blocks to polyspermy
- completion of Meiosis II and ferilization
- cleavage
- blastocyte formation
list of step of implatation/embroyic formation
- implatation
- formation of placenta
- extraembryonic membranes
- gastrulation:germ layer formation
- organofneisis: differation of the germ layers
- fetal cirulation/delevlopment
list of steps of fetal development
- fetal cirulation
- anatomical changes
- metabolic changes
- physiological changes
5.
steps of labour
- dilation
- expulsion
- placental
step 1 of feriliation : sperm transport and capacitation
Millions of sperm ejaculated into the female reproductive tract are lost due to leakage from the vaginal canal, destruction by the acidic environment of the vagina, inability to pass the cervical mucus, or destruction by defense cells of the uterus.
In order to fertilize an egg, sperm must be capacitated, a process involving weakening of the sperm cell membrane in order to allow release of acrosomal hydrolytic enzymes.
step 2 of fertilizatoin: acrosomal reaction/sperm peneration
A sperm cell must breach both the corona radiata and zona pellucida in order to penetrate the oocyte.
Once a sperm cell binds to a receptor on the zona, Ca++ channels open, leading to a rise in intracellular Ca++ in the sperm cell that causes the release of acrosomal enzymes: Hundreds of sperm cells must undergo the acrosomal reaction before fertilization can occur.
Once a sperm cell binds to membrane receptors on the oocyte membrane, its nucleus is pulled into the cytoplasm of the oocyte, where the gametes fuse.
step 3 of fertilzation: blocks to polyserpmy
Polyspermy, entry by more than one sperm cell, leads to a lethal number of chromosomes and is prevented in several ways.
The oocyte membrane block occurs when the oocyte sheds the rest of its sperm-binding receptors following the binding of a sperm cell.
The zona reaction (slow block to polyspermy) involves entry of a sperm cell into the oocyte, which causes waves of Ca++ to be released into the oocyte’s cytoplasm, which activates the oocyte to prepare for the second meiotic division.
The cortical reaction (slow block to polyspermy), triggered by the Ca++ surge in the cytoplasm, results in destruction of sperm-binding receptors, while enzymes released from granulocytes inside the plasma membrane form a swollen, hardened membrane.
step 4 of fetilzationL completion of Meiosis II and fertilzation
Following the entry of the sperm pronucleus into the oocyte, the oocyte completes meiosis II, forming the ovum pronucleus, and the second polar body: male and female pronuclei fuse and produce a zygote. Early embryonic development begins with fertilization and continues with the movement of the embryo to the uterus, where it implants in the uterine wall.
step 5 of ferilzation: clevage
After 36 hours, cleavage forms two blastomeres; by 72 hours, continued division will have produced a ball of 16 or more cells, called a morula.
step6 of fetilzation: blastocytst formation
After 4–5 days, the embryo has formed about 100 cells, becoming a blastocyst, and breaks free of the zona pellucida.
The blastocyst is a fluid-filled ball of cells that separate into trophoblast cells that produce the placenta, and the embryoblast, which will become the embryonic disc.
step 1 of implatation
Implantation occurs after 6–7 days; the trophoblast adheres to the endometrium and produces enzymes and growth factors to the endometrium, which takes on characteristics of an inflammatory response.
Uterine capillaries become permeable and leaky, and the trophoblast proliferates, forming the inner
cytotrophoblast and the outer syncytiotrophoblast that erodes the endometrium to allow the blastocyst to embed. Trophoblast cells secrete human chorionic gonadotropin (hCG), which acts on the corpus luteum to maintain its presence until the placenta can adequately support the developing fetus.
step 2 of implatation : formation of placenta
Placentation is the process of proliferation of the trophoblast, giving rise to the chorion which, along with the endometrial decidua basalis, becomes the placenta.
The placenta is fully functional as a nutritive, respiratory, excretory, and endocrine organ by the end of the third month of gestation.
emboryic stage 1 : extraembryonic membranes
While implantation is occurring, the blastocyst is being converted into a gastrula, in which three primary germ layers form and embryonic membranes develop.
The amnion forms the transparent sac ultimately containing the embryo and provides a buoyant
environment that protects the embryo from physical trauma.
The yolk sac forms part of the gut, and produces the earliest blood cells and blood vessels.
The allantois is the structural base for the umbilical cord that links the embryo to the placenta and becomes part of the urinary bladder.
The chorion helps to form the placenta and encloses the embryonic body and all other membranes
embroyic period 2 : gastrulation: germ later formation
Gastrulation is the process of transforming the two-layered embryonic disc to a three-layered embryo containing three germ layers: ectoderm, mesoderm, and endoderm.
Gastrulation begins with the appearance of the primitive streak, which establishes the long axis of the embryo.
The endoderm gives rise to epithelial linings of the gut, respiratory, and urogenital systems, and associated glands.
The mesoderm gives rise to all types of tissues not formed by ectoderm or endoderm, such as muscle tissue. c. The ectoderm gives rise to structures of the nervous system and the epidermis
emrboyic period 3 : organogenesis-differentiation of germ layers
Organogenesis is the formation of organs and organ systems; by the end of the embryonic period at 8 weeks, all organ systems are recognizable.
The embryo starts off as a flat plate, but as it grows, folds laterally into a tube, and folds toward the center from both ends, finally fusing where the yolk sac and umbilical vessels protrude.
Specialization of the endoderm forms the GI tract; outpocketings of endoderm form the mucosa of the
respiratory tract and several glands.
Specialization of the ectoderm results in the development of the brain and anterior end of the spinal cord
Neural crest cells migrate and give rise to the cranial, spinal, and sympathetic ganglia, adrenal medulla,
pigment cells of the skin, and some connective tissues.
Specialization of mesoderm occurs as mesodermal aggregates appear on either side of the notochord.
Mesodermal specialization forms the notochord and gives rise to the dermis, parietal serosa, bones, muscles, kidneys, gonads, cardiovascular structures, and connective tissues.
fetal circulation
By 31/2 weeks, the embryo has a blood vessel system and a pumping heart.
Unique prenatal vascular modifications include umbilical arteries and veins that carry blood to and from the placenta, a ductus venosus that serves to bypass the liver, and the foramen ovale and ductus arteriosus, used to divert most blood flowing through the heart away from the pulmonary circulation into the systemic circulation.
Occlusion of vascular shunts after birth a. The umbilical arteries and veins constrict and become
fibrosed, becoming the medial umbilical ligaments, and the round ligament of the liver, or ligamentum teres.
b. The ductus venosus closes and is eventually converted to the ligamentum venosum.
c. The pulmonary circulation becomes functional, and pressure in the right side of the heart decreases, while pressure in the left side increases, causing pulmonary shunts to close.
d. A flap of tissue covers the foramen ovale and fuses with the wall, becoming the fossa ovalis; the ductus arteriosus constricts, becoming the ligamentum arteriosus.
events of fetal development
By the end of the embryonic period, bones begin to ossify, muscles are formed, and most organ systems are forming in place, and blood supply to and from the placenta is well developed.
During the fetal period, there is rapid growth of the structures established in the embryo, and the greatest amount of growth occurs during the first eight weeks of life.
anatomic changes of fetus
The female reproductive organs and breasts become increasingly vascular and engorged with blood.
The uterus enlarges dramatically, causing a shift in the woman’s center of gravity and an accentuated lumbar curvature (lordosis).
Placental production of the hormone relaxin causes pelvic ligaments and the pubic symphysis to soften and relax.
There is a normal weight gain of around 28 pounds, due to the growth of the fetus, maternal reproductive organs, and breasts, and increased blood volume
metabolic changes
As the placenta enlarges, it produces human placental lactogen (hPL), which works with estrogen and progesterone to promote maturation of the breasts for lactation.
Human placental lactogen also promotes the growth of the fetus and exerts a glucose-sparing effect on maternal metabolism.
Plasma levels of parathyroid hormone and activated vitamin D rise, ensuring a positive maternal calcium balance throughout pregnancy.
physiological changes of fetus
Many women suffer morning sickness during the first few months of pregnancy, until their systems adapt to elevated levels of hCG, estrogens, and progesterone.
Heartburn often results from the displacement of the esophagus, and constipation may result due to the decreased motility of the digestive tract.
The kidneys produce more urine, because maternal metabolic rate is higher, and there is additional fetal metabolic waste that must be eliminated.
Vital capacity and respiratory rate increases, but there is a decrease in residual volume, and many women suffer from difficult breathing, or dyspnea.
Blood volume increases to accommodate the needs of the fetus and may increase up to 40% by the 32nd week of pregnancy.
Mean blood pressure decreases during the second trimester, but then returns to normal levels during the third trimester; cardiac output increases by 35–40%.
partiurition
Parturition is the process of giving birth and usually occurs within 15 days of the calculated due date, which is 280 days from the last menstrual period.
inittationn of labour
Estrogen levels peak, possibly due to rising levels of fetal adrenal cortical hormones (cortisol), stimulating myometrial cells of the uterus to form abundant oxytocin receptors and antagonizing the quieting effect of progesterone on uterine muscle.
Fetal cells produce oxytocin, which promotes the release of prostaglandins from the placenta and further stimulates uterine contraction.
Increasing cervical distention activates the mother’s hypothalamus, which signals the release of oxytocin, setting up a positive feedback loop in which further distention of the cervix promotes the release of more oxytocin, which causes greater contractile force.
Expulsive contractions are aided by a change that occurs in an adhesive protein, fetal fibronectin, converting it to a lubricant.
dilation stage of labour
The dilation stage of labor extends from onset of labor to the time when the cervix is fully dilated by the baby’s head, at about 10 cm in diameter.
At first, only the superior uterine muscle is active, but as labor progresses, contractions become more vigorous and rapid, and more of the uterus becomes involved.
As the infant’s head is forced against the cervix, the cervix softens, thins, and dilates; ultimately, the amnion ruptures, releasing amniotic fluid.
The dilation stage is the longest part of labor; during this phase, the infant’s head becomes engaged as it passes into the true pelvis, and as descent continues, the baby’s head rotates so that its greatest dimension is along the anteroposterior line, allowing easier navigation of the pelvic outlet.
explusion stage
The expulsion stage extends from full dilation until the time the infant is delivered.
Crowning occurs when the baby’s head distends the vulva; when the baby is in the vertex, or head-first,
presentation, the skull acts as a wedge to dilate the cervix.
Once the head has been delivered, the rest of the baby follows much more easily; after birth, the umbilical cord is clamped and cut.
placental stage
During the placental stage, uterine contractions compress uterine blood vessels, limiting bleeding, and cause detachment of the placenta from the uterine wall, followed by delivery of the placenta and membranes (afterbirth).
stages after birth
A. At 1–5 minutes after birth, the baby’s physical signs are assessed based on heart rate, color, muscle tone, and reflexes; a score from 0–2 is assigned to each factor, and the total is called the Apgar score.
B. Taking the First Breath and Transition
Once the placenta is no longer removing carbon dioxide from the blood, it builds up in the infant’s blood, resulting in acidosis that signals the respiratory control centers.
The first breath is very difficult, due to the fact that airways are small, and the lungs are collapsed.
C. Occlusion of special fetal blood vessels and vascular shunts takes place.
D. The transitional period is the 6–8 hours after birth characterized by intermittent waking periods in which the infant’s vital signs fluctuate but after a time, the baby stabilizes and wakes mostly in response to hunger.
vitro ferilzaition (IVF)
In vitro fertilization (IVF) combines oocytes and sperm in culture dishes for several days, to allow fertilization to occur. The two-cell or blastocyst stage embryo is transferred to the woman’s uterus.
zygote intrafallopian tranfer (ZIFT)
Zygote intrafallopian transfer (ZIFT) immediately places fertilized oocytes into the woman’s uterine tubes, with the hope that normal blastocyst formation and implantation occurs.
gamete intrafallopian tranfer (GIFT)
Gamete intrafallopian transfer (GIFT) directly transfers sperm and oocytes to a woman’s uterine tube, hoping that normal fertilization, blastocyst formation, and implantation occurs.
