Layers of ovulated egg (secondary oocyte): - Corona radiata: the outermost layer of follicular cells - Zena pellucida (ZP): layer with receptors for sperm binding - Perivitelline space: space above the egg plasma membrane - The plasma membrane of the egg: the innermost layer directly over the egg (where the egg and sperm fuse) How does sperm enter the egg? - The sperm has an acrosome which is a cap of digestive enzymes on the head of the sperm that is used to dissolve the outer egg layer. The sperm acrosome binds to the ZP of the egg and the enzymes are released so sperm can get entry into the cell. - Polyspermy occurs when more than one sperm enters the cell. - Fast block: occurs within the first 2-3 seconds of the first sperm entering. This is a change in the egg’s electrical potential (-70mV to +20mV) - Slow block: occurs within 10 seconds of the first sperm entering. - The fusion of sperm with plasma membrane causes a calcium wave to spread through the egg and the calcium wave triggers a cortical reaction which causes water to fill perivitelline space. Water lifts off the egg and makes it stiff. Gastrulation is the embryonic tissues that divide into “germ layers”: - Endoderm: the layer that becomes gastrointestinal and lungs - Mesoderm: the layer becomes the skeleton, muscles, heart, blood vessels, urinary and reproductive system - Ectoderm: the layer becomes the nervous system, skin, eyes, hair Blastocyst is a ball of cells that secretes hCG (which rescues CL): - Inner cell mass will become the embryo - Trophoblast becomes the chorion - Chorion = placenta (connects to the umbilical cord for nutrients, hormones, and oxygen to go to the embryo. Allows waste to leave and pass through the mother's circulatory system) - Chorionic villi = umbilical cord - amniotic fluid= fluid surrounding embryo/ fetus, held within the amniotic sac Hormones: - The embryo releases hCG which prevents the CL from breaking down - The placenta releases hormones that affect the mother - Progesterone: keeps the uterine lining thick and in a pregnancy friendly state. It also suppresses the mother’s immune system to decrease the probability of it attacking the fetus - Estrogen: causes water retention in the mother which can increase blood pressure (gestational hypertension) - Peptide hormone: insulin-resistance in mother where the tissues take up less blood glucose and the fetus diverts the glucose to itself (gestational diabetes) - Oxytocin causes uterine contractions during labor (is also a bonding hormone) - The sudden drop in estrogen and progesterone from the placenta can cause postpartum depression Prenatal Testing: testing done on fetal cells to look for problems in development (could be genetic) - Amniocentesis: insertion of a long needle to withdraw fluid and fetal cells for analysis - Chorionic villi sampling: insertion of catheter into vagina, cervix, uterus to suction some of the chorionic villi of the placenta for analysis - Ultrasound: use of sound waves to make pictures Parturition: the process of giving birth The start of labor: - When the fetus gets too big, they start to lose room in the uterus. The fetus releases a cortisol (stress hormone) which causes the moms pituitary to release oxytocin. Oxytocin causes uterine contractions that squeeze the fetus and makes it release more cortisol. And as the fetus pushes down on the cervix from the contraction more oxytocin will be released. The cycle repeats until the baby (and placenta) is out Stage 1: - The baby’s head presses against the cervix which causes oxytocin release - The baby’s head enters the cervix and the amniotic sac is pinched which causes it to rupture (water breaks) - The cervix starts to dilate. - Epidural can be given. (anesthetic injected into the epidural space around the spinal cord) Stage 2: - Episiotomy can be performed if needed - - Controlled cut in the perineum (area between vagina and anal opening) The baby is delivered! Stage 3: - Placenta (afterbirth) is expelled - Uterine involution starts (returns uterus back to normal shape) Vernix caseosa: protective cheesy coating that covers fetus Lanugo: fine hairs that covers fetus Striae: stretch marks Dystocia: problems during birth - Breech birth occurs when the baby is positioned upside down for birth (butt or feet first) - External cephalic version: doctor physically reaches in and turns the baby’s body into right position (head down) - Can cause bleed of mom that can lead to blood mixing with fetus (Could be a problem when Rh disease) Reason for C-section: surgical removal of fetus due to complications during birth, or when baby’s or mother’s life is in danger - Stress of mother (hypertension, diabetes, and other) - Stress of baby (umbilical wrapped around neck) - Placenta previa (placenta block birth canal) - Infectious disease (genital herpes, etc) - Breech birth Breastfeeding Pros and Cons Pros Cons Uterus back to normal shape If baby is allergic to milk proteins Antibodies in breastmilk (protects baby) If mom is highly stressed Bond with the baby (oxytocin release) If mom is addicted to drugs Baby formula is expensive Can be painful Making milk takes energy (help mom lose weight) Time commitment If mom needs medication then she might need to stop
