Describe the events of the female sexual cycle that provide a mature egg cell from an ovary and prepare the uterine endometrium for the possibility of fertilization (conception) and pregnancy.
1) Egg is released into peritoneum and moves into fallopian tube, where it most likely will be fertilized
2) Takes egg up to 7 days before it fully reaches uterus, at which point if not fertilized, will die
3) If egg isn't fertilized, corpus luteum dries up, lowering progesterone secretion, and uterus no longer ready for implantation of egg, starting menstural cycle
4) If egg is fertilized, it immediately starts mitosis, so that by the time is reaches uterus it's already becoming embryo, ready for implantation in wall of uterus
Describe the optimal time frame and location within the female reproductive tract for fertilization to occur.
48 hours after ovulation to 14 hours before ovulation
Describe the actions taken by the structures of the female reproductive tract to facilitate sperm migration toward the mature egg.
1) Egg enters uterus at external end of cervix
2) sperm travels through uterus and into fallopian tube
3) takes sperm a couple hours to travel from cervix to fallopian tube
4) Sperm mostly likely to fertilize egg in fallopian tube as it's moving towards uterus, because higher likelihood that sperm and egg will meet in the narrow halls of the fallopian tube
5) Vagina secretes mucus that only allows sperm to reach egg at certain period of time optimum for egg and sperm
Describe the process of capacitation and explain why this process must occur before fertilization can occur.
- plasma membrane over acrosome gets thinner until ruptures and releases enzymes that eat away cells of zona pellucida surrounding egg
- whichever sperm does that first, deposits nucleus of sperm into egg
Briefly describe the series of events that must occur once a sperm encounters an egg in order to achieve fertilization by only a single sperm.
- 2000 - 3000 sperm reach egg and start eating away at wall of egg.
- latecomer sperm actually penetrates egg surface and fertilizes egg
- once sperm has penetrated egg, egg releases fluid that kills any other sperm that makes contact with egg
Define the terms: zygote, embryo and fetus and describe the duration of each of these phases of prenatal development.
- zygote - initial joining of sperm and egg after fertilization, forming diploid cell (0-30 hrs)
- embryo - weeks 2 - 8 of development
time when organs of body begin to form
- fetus - end of 8th week, when most organs and organ systems are formed, skeletal muscle and bones are forming, and heart of pumping blood throughout embryo
Describe the sequence and major events that occur during each phase of the preembryonic stage of development: cleavage, morula and blastocyst that ultimately result in the formation of the embryo.
- preembryotic stage - days 0 - 16
cleavage - first stages of mitotic division of zygote completed w/in first 30 hours forming 16 cells
- Morula - formation of solid mass cells from cells formed during cleavage (w/in 72 hours of fertilization)
-- travels down uterine tube, continuing to divide
- Blastocyst - forming of hollow ball from cells containing small inner mound of cells called embryoblast (which will develop into embryo) and sphere of simple squamous called trophoblast (which will become placenta)
Describe the timing and sequence of events in the process of implantation of the blastocyst that brings the developing organism into close proximity with the maternal circulation.
- Day 6
- blastocyst makes contact w/ uterine wall and implants
- trophoblast divides to form inner and out layer
Define the term: ectopic pregnancy, describe the typical clinical presentation of a woman with an ectopic pregnancy and explain why this is a true medical/surgical emergency condition.
- any egg development that happens outside of the uterus
Explain the role of human chorionic gonadotropin (hCG), the hormone secreted by the trophoblast until the end of the eighth week of gestation.
- stimulates corpus luteum to secrete progesterone
- Is hormone detected in urine pregnancy test
Describe the formation of the three primary germ layers from the embryoblast that completes the formation of the embryo.
- ectoderm - forms from splitting and flattening of embryoblast
- endoderm - forms from splitting and flattening of embryoblast
- mesoderm - forms from groove of ectoderm b/t ectoderm and endoderm
Identify the mature tissues/organs that develop from each of the three primary germ layers - the ectoderm, the mesoderm and the endoderm.
- ectoderm - everything on outside including nervous system, brain, adrenal medulla, pineal and pituitary glands, salivary glands, ear structures, epidermis
- mesoderm - everything in middle of body including skeleton, muscle, connective tissue, blood, mesothelium
- endoderm - Lining of the insides of the body including epithelial lining, thyroid, parathyroid glands, thymus, mucosal endothelium, accessory digestive and reproductive organs
Describe the formation and principle functions of the amnion, yolk sac, allantois and chorion.
- amnion - develops from embryoblast and cytotrophoblast forming cavity and filling w/ fluid
-- embryo develops here
- yolk sac - develops from ventral side of embryo
-- produces cells that form blood and blood vessels
-- produces germs cells that will become oogonia or spermatogonia
-- develops from endoderm, so portions will develop into digestive, respiratory, urinary tracts
- allantois - develops blood vessels that will be umbilical cord, and eventually urinary bladder
- chorion - develops into part of placenta
Describe the placental transfer of gases, nutrients and waste materials between maternal and fetal blood - the two blood supplies do not mix!
- makes it so that maternal and fetal blood don't mix, similar to vessels of lungs
- O₂, nutrients and anti-bodies diffuse into placenta from maternal blood and transported to fetus via umbilical vein
- Metabolic waste from fetus carried to placenta via umbilical arteries, diffusing into maternal blood for disposal
- Fetal Hb has higher affinity for O₂, allowing it to pull O₂ away from maternal to deliver to fetus
Identify the principle hormones secreted by the placenta and describe the effects of each hormone on the maternal physiology - specifically the production of hormones required for the maintenance of pregnancy and mammary development - and on the developing fetus.
- hCG - secreted by blastocyst and embryo maintaining corpus luteum
- progesterone and estrogen - maintain endometrium
Describe the major events that occur during the fetal stage of development.
- 4 weeks - beginning development of CNS and limbs
- 8 weeks - development of eyes, face, fingers, toes, brain waves
- 12 weeks - eyes and limbs well-formed, swallows amniotic fluid and produces urine
- 16 weeks - face fully formed, , kidneys formed, heartbeat can be heard
- 20 - 22 weeks - time of viability - baby born b/f this time won't survive
- 35 weeks - lung maturity
- 40 weeks - full term
- 40+ weeks - placenta begins to disintegrate
Identify and describe the functions of the unique features of the fetal circulatory system that allow the fetus to survive in the intrauterine environment until birth.
- foramen ovale - hole that allows blood to pass from LA to RA w/o going through lungs
- ductus arteriosus - vessel that allows blood that's entered RV to bypass lungs and flow directly into systemic circulation
- umbilical vein - transports O2 and nutrient-rich blood from placenta to fetus
- ductus venous - continuation of umbilical artery allowing blood to bypass liver and directly into IVC
- umbilical arteries - transport deoxygenated blood and waste-filled blood from fetus to placenta
Describe the major anatomic and physiologic changes that occur in a woman's body throughout gestation with specific attention to the cardiovascular system.
- increase in maternal blood volume (1 - 2 L increase)
- increase in CO (30-40%)
- decrease blood pressure due to increase in endometrial blood vessels
- pressure placed on iliac veins late in pregnancy can lead to edema, varicose veins and hemorrhoids
Describe the major anatomic and physiologic changes that occur in a woman's body throughout gestation with specific attention to the respiratory system.
- increase minute ventilation (50%) due to increase demand for O2 by fetus and need to rid extra CO₂ from fetal metabolism
- later in pregnancy, uterus can put pressure on diaphragm, resulting in dyspnea (shortness) of breath
Describe the major anatomic and physiologic changes that occur in a woman's body throughout gestation with specific attention to the urinary system.
- increases glomerular filtration by 50% to filter additional waste from fetus
- increased aldosterone, estrogen, progesterone leads to increased water and salt retention
- increased pressure on bladder causing frequent urination and occasional incontinence
Describe the major anatomic and physiologic changes that occur in a woman's body throughout gestation with specific attention to the integumentary system.
- stretching of abdominal skin, leading to stretch marks due to tearing of connective dermis tissue
- increased subcutaneous fat, ensuring women has enough energy stores to sustain self and fetus
Describe the major anatomic and physiologic changes that occur in a woman's body throughout gestation with specific attention to the digestive system.
- frequent nausea and vomiting due to increased progesterone and hCG levels
- some women experience hyperemesis gravidarum - excessive vomiting requiring medication and medical attention
- increased heartburn b/c of increase acid reflux due to pressure on the stomach
Describe the major anatomic and physiologic changes that occur in a woman's body throughout gestation with specific attention to the reproductive system.
- corpus luteum secretes estrogen and progesterone to maintain endometrium and prevent onset of menses, resulting in missed periods
- blood flow to uterus increases 50% and continues to grow during pregnancy
- breast enlargement to due accumulation of fat and proliferation of mammary glands
Describe the major anatomic and physiologic changes that occur in a woman's body throughout gestation with specific attention to the endocrine system.
- increased secretion of TSH and ACTH, leading increased secretion of T3/T4 and cortisol and aldosterone from adrenal cortex
- needed for increased metabolic demand of mother and fetus
- increased prolactin secretion, preparing mammary glands for lactation after delivery of baby
Describe the major anatomic and physiologic changes that occur in a woman's body throughout gestation with specific attention to the nutrition and metabolism.
- increased basal metabolic rate (15% increase)
- increased thermogenesis, so women need to be careful not to overheat
- increased appetite and caloric intake needed to meet growing demands of fetus
- women should gain only 20-30 lbs during pregnancy
Describe the series of events that occur during labor, including the three stages of labor and the role of the hormone oxytocin that lead to vaginal delivery of the fetus (parturition).
- 1st stage - onset of effective uterine contractions through complete dilation and effacement of cervix
- 2nd Stage - complete dilation of cervix to deliver of fetus
- 3rd Stage - deliver of fetus to deliver of placenta
- pressure of fetus head on cervix causes release of oxytocin, creating positive feedback loop stimulating stronger and stronger uterine contractions leading to greater stretching of cervix
Describe the changes that must occur in the circulatory, respiratory, digestive and immune
systems shortly after birth to allow the neonate to transition to extrauterine life.
- circulatory - closing of foramen ovale and ductus arteriosus, allowing for adequate O2 supply
- Respiratory - development of surfactant from alveoli
- Immune - naturally acquired passive immunity already in baby through passage of IgG antibodies from maternal serum across placenta last 6 months after birth until child begins to produce own antibodies
- Breastfeeding all provides further immunity b/c milk contains high levels of IgA antibodies
Identify the remnant structures of the fetal circulatory system that persist after birth and into adulthood.
- Foramen ovale = fossa ovalis
- ductus arteriosus = ligamentum arteriosum
- umbilical vein = ligamentum teres
- ductus venosus = ligamentum venosum
- umbilical arteries = median umbilical ligaments
Describe the process of lactation, including the roles of the hormones prolactin and oxytocin.
- production and expulsion of milk from lactiferous ducts and lactiferous sinuses
- production stimulation by release of prolactin, from anterior pituitary
- expulsion stimulation by release of oxytocin released in response to nipple stimulation