Chapter 20 Flashcards
What is diversity?
genes from 2 individuals are combined in random ways to produce a new individual
Why is diversity important?
allows for genetic variation and adaptability to a changing environment
How does a new individual progress?
zygote to embryo to fetus
What happens to germ cells during meiosis?
gametes (sperm and ova) in gonads via meiosis
When do testes stop making testosterone?
third trimester
When does sex hormone secretion occur?
not until the gonads are stimulated at puberty
- anterior pituitary releases gonadotropic hormones
What effect does follicle-stimulating hormone (FSH) and luteinizing hormone (LH) have on people?
1) stimulation of spermatogenesis or oogenesis
2) stimulation of gonadal hormone secretion
3) maintenance of the structure of the gonads
What are the 2 components of the testes?
- seminiferous tubules
- interstitial tissue
What is in the seminiferous tubules? What happens here?
FSH receptors here on sertoli cells
- influences spermatogenesis
What is in the interstitial tissue? What happens here?
LH receptors found on Leydig cells
- makes and secretes testosterone
- also filled with blood and lymphatic capillaries
How do spermatids move?
seminiferous tubules to rete testis to efferent ductules to epididymis
What is the purpose of the epididymis?
site of sperm maturation and storage
Where do spermatozoa move during ejaculation?
epididymis to ductus deferens to ejaculatory duct to urethra
What adds fluids to sperm for semen?
seminal vesicle and prostate gland
What is in semen besides sperm?
seminal fluid (fructose = energy for sperm)
prostate fluid (citric acid, calcium, coagulation proteins)
What is emission?
movement of semen into urethra
What is ejaculation?
forceful expulsion of semen from urethra
What nervous system controls emission and ejaculation?
sympathetic
What organs are involved in ejaculation?
contraction of smooth muscles in:
- tubules
- seminal vesicle
- prostate
- muscles at base of penis
What is oligospermia?
sperm count of <20 million/mL semen
- less fertile
What are likely causes of oligospermia?
heat, drugs, anabolic steroids
What is the function of the ovaries?
female gonads
- site of oocyte and sex steroid production
What is the function of the fallopian tubes?
fimbriae that wrap around ovaries and catch the oocyte after ovulation
- most common site of fertilization
What is the function of the uterus?
site of embryonic development
What are the layers of the uterus?
- endometrium: inner layer (where embryo implants and develops)
- myometrium: middle muscle layer, contracts to expel baby at birth
- perimetrium: outer connect tissue layer
- cervix: narrow bottom region of uterus
What happens to females at the end of gestation?
oogonia begins meiosis to produce primary oocytes
How does the number of oocytes decrease as life goes on?
Newborn girl: 2 million oocytes
Puberty: 400k
- only 400 are ovulated
Where are the primary oocytes stored?
primary follicles
What happens to the primary follicles in response to FSH?
they grow to produce many layers of granulosa cells
- also secondary follicles
What happens during ovulation?
graafian follicle (ovum before ovulation) is so big it bulges out of the ovary
- hormones stimulate the follicle to burst and release the secondary oocyte
- if it’s not fertilized, the oocyte will degenerate after a few days
What happens after ovulation?
remaining follicle becomes corpus luteum
- secretes both estrogen and progesterone
What is the menstrual cycle?
28 day cycle of endometrial buildup and sloughing in response to ovarian hormones
- changes in endometrium follow changes in the follicles of the ovaries
What are the 3 phases of the menstrual cycle?
menstrual
proliferative
secretory
What happens in terms of hormones with contraception?
- synthetic estrogen and progesterone
- decrease in FSH and LH (negative feedback)
- no LH surge = no ovulation
- reduces cervical mucus (sperm needs this to survive)
- prevents implantation on endometrium
What are some side effects of contraception?
- higher risk of breast and cervical cancer
- higher weight gain
- higher depression
- higher stroke and heart attack risk
- higher suicide risk
What is the benefit of FABM?
- no medical side effects
- comparable to other contraceptive success rates
How does FABM work?
fertility awareness-based methods
- uses actual data
- mucus observations
- temperature readings
- hormone levels in urine for real time observations
- fertile window (8-19 days)
What are examples of extrinsic regulation of GnRH?
- pheromones can synchronize the menstrual cycle (olfactory system has input on GnRH neurons)
- stress and emotions can affect menstrual cycle
- low body fat can produce delayed menarche (amenorrhea)
= controlled by leptin
What happens during implantation?
blastocyst releases chorionic gonadotropin
- acts like LH to keep corpus luteum alive to continue releasing estrogen and progesterone
- keeps endometrium thick and vascular to house the blastocyst
What does the fetal part of the blastocyst become?
- endoderm: gut organs
- ectoderm: becomes skin and nervous system
- mesoderm develops later and will become the muscles, bones, connective tissues
How does the placenta get nutrients?
- umbilical arteries deliver fetal blood to placental vessels
- blood circulates within placenta and returns to the fetus through umbilical vein
- maternal blood is delivered to and from placenta
maternal and fetal blood don’t mix - molecules diffuse across tissues of the placenta for exchange
- oxygen and nutrients diffuse from maternal to fetal blood
- CO2 and wastes diffuse from fetal to maternal blood
- placenta degrades maternal molecules that may harm fetus
What immunities are passed to the baby through breast feeding?
- IgG antibodies are passed from mother to child in utero
- IgA antibodies are passed to the child in breast milk
= provides passive immunity
How is the placenta formed?
After implantation
- from trophoblast layer of cells in the blastocyst and from maternal cells in the uterus
What is the developed placenta made of?
large mass of blood vessels from mother and fetus
What is a key feature of the fetus at day 23 (3 weeks pregnant)?
heart is beating and pumping
What is a key feature of a fetus at day 30-55 (4-8 weeks pregnant)?
growing rapidly
What is a key feature of the fetus at 5 weeks?
reflexive movement begins
What is a key feature of the fetus at 6 weeks?
- brainwave activity has begun
- hands begin to move
- every structure that is present in an adult is also present in the baby
What is a key feature of the fetus at 7 weeks?
- head rotates and leg moves
- baby can hiccup
- fetal heart EKG patten is similar to an adult
What is a key feature of the fetus at 8 weeks?
- urine production and release begins
- joints are similar to those of an adult
- right and left handedness emerges
What is a key feature of the fetus at 9 weeks?
- baby can grab objects, open and close jaw, move tongue, sigh, stretch
- nerve receptors are functioning in face, palms of hand and soles of feet can sense light touch
- reproductive organs form
- retina of eye present
What is a key feature of the fetus at 10 weeks?
- bone formation in most bones starts
- finger and toe nails grow
- unique fingerprints
- eyes roll down reflexively
What is a key feature of the fetus at 11 weeks?
- complex facial expressions begin
- intestines absorb water and glucose
- baby inhales and exhales amniotic fluid
What is a key feature of the fetus at 12 weeks?
- bile production begins in liver
- bowel movements begin
- taste buds all over tongue
- pancreas completely formed
- thyroid completely formed
What is a key feature of the fetus at 14 weeks?
- sensitive to touch
- touch to mouth causes baby to turn away
What is a key feature of the fetus at 15 weeks?
- glucagon is present in bloodstream
- females have primary follicles containing oocytes in ovaries
What is a key feature of the fetus at 16 weeks?
- mother can begin to feel baby move
- baby has hormonal stress response to invasive procedures
What is a key feature of the fetus at 17 weeks?
- cerebral cortex is active
- meconium (product of cell loss, digestive secretion, swallowed amniotic fluid) accumulates in the bowel
- brown fat production allows baby to produce heat
What is a key feature of the fetus at 19 weeks?
- oogonia production stops permanently
- daily biological rhythms like sleep begin
What is a key feature of the fetus at 20 weeks?
- baby responds to increased range of sounds
- baby can feel pain
- surfactant production may begin
What is a key feature of the fetus at 21 weeks?
- has a better than 50% chance of survival
What is a key feature of the fetus at 23 weeks?
- brain has major growth spurt increasing size by 400-500%
- daily movement helps work out developing muscles
What is a key feature of the fetus at 24 weeks?
- baby can hear sounds outside the womb
- baby will have a blink-startle response to a loud sound increasing heart rate and movement
- gas exchange now possible outside of womb
What is a key feature of the fetus at 25 weeks?
- baby can taste
= if mother eats sweets, baby will swallow faster
What is a key feature of the fetus at 26 weeks?
eyes produce tears
- sense of smell present
What is a key feature of the fetus at 27 weeks?
pupils react to light
What is a key feature of the fetus at 28 weeks?
- baby can differentiate between high and low frequency sounds from outside the womb
- bone marrow takes over production of red blood cells from liver
- baby can do somersaults by a series of movements similar to walking
What is a key feature of the fetus at 29 weeks?
eyes can move around and all senses are functioning
What is a key feature of the fetus at 30 weeks?
- breathing motions continue to be more common, even with no air in the womb
- infants born at this time can survive without lifesaving treatment
What is a key feature of the fetus at 31 weeks?
- baby can have dreams
What is a key feature of the fetus at 32 weeks?
baby’s memory begins working
- prefers sounds heard in the later part of pregnancy to ones heard only after birth
What is a key feature of the fetus at 35 weeks?
- baby has firm grasp
- lung development ready for birth
What is a key feature of the fetus at 37 weeks?
- baby drinks 15oz amniotic fluid each day
- baby is more coordinated
- pregnancy is full-term and doctor won’t stop labor
What is a key feature of the fetus at 38 weeks?
14-20 inches and 6-10 pounds
What happens at first breath?
- amniotic sac breaks
- labor contractions in uterus
- mother pushes baby out
- after umbilical cord is cut, baby increases its carbon dioxide content in baby’s blood
- stimulates baby’s brain to trigger breathing and baby takes first breath
