Phys - OB Flashcards
what timing must coitus occur around ovulation for fertilization to be possible
72 hours before
24 hours after
How long are sperm and oocytes viable
- ovulated oocyte: 12-24 hrs
- sperm 12-48 hours
Journey of sperm to the egg
- 250 m sperm per ejaculate
- millions don’t make it to the vagina, millions die in acidic environment, and millions don’t make it through the cervical canal
- uterine contractions act against sperm’s upward course
- half go into the wrong uterine tube
- only a few hundred make it to the ovum
Capacitation
- changes sperm go through in order to penetrate and fertilize an egg
- cholesterol stabilizes the acrosome
- it depletes along the female reproductive path
- takes 6-8 hours
Acrosomal reaction of sperm
- chemical release
- numbers
- function
- hyaluronidase, acrosin, other proteases to break down the cells around the egg
- hundreds of acrosomal reactions needed (one sperm is not enough to fertilize an egg)
- function is to breach the corona radiate and zona pellucida
How does monospermy occur?
- sperm binds oocyte membrane
- Na and Ca channels open
- fast and slow blocks
Fast block to polyspermy
- Na influx depolarizes the membrane
- prevents further penetration
Slow block to polyspermy
- Ca influx causes cortical granule exocytosis
- Contents are released into the ECF under the zona pellucida
- binds water and swells to create a gel-like border around the egg
- detaches sperm from the membrane
Once sperm is in, what occurs to complete fertilization
- sperm nucleus is phagocytize by oocyte
- Ca influx triggers completion of meiosis from metaphase II
- sperm and oocyte pronuclei membranes rupture
- fertilization is accomplished when chromosomes from egg and sperm combine and a diploid zygote is formed
First stages of cells after fertilization
early mitotic divisions of zygote increase cell number but not size:
- 2 cells (36 hours after fertilization, in the uterine tube)
- 4 cells
- 8 cells etc
- morula (100 cells, 72 hours, is in the uterus)
- blastocyst
Blastocyst
- describe
- two main types of cells
- fluid filled ball of cells
- inside called blastocoel
- Trophoblasts: single cell outer layer that become the placenta
- Inner cell mass: becomes the embryonic disc
Implantation
- When
- describe process
- D6
- trophoblasts bind to endometrial cells and secrete digestive enzymes against endometrium
- endometrium proliferates and covers the blastocyst
- entire process occurs from approx D7 to D14
What happens to the blastocyst during implantation
- Differentiates into two layers
- Synctiotrophoblasts: multinucleate outer layer which continue to secrete digestive enzymes
- Cytotrophoblast: inner cell layer
What hormone is released after implantation
HCG - human chorionic gonadotropin
HCG
- secreted by what
- target
- action
- timing
- when detected in blood
- secreted by synctiotrophoblasts
- targets corpus luteum
- stimulates secretion of P and E
- starts W4, spikes W8
- blood at W3
What secretes HCG after synctiotrophoblasts
Chorion
- develops from trophoblasts
When does the placenta take over E and P secretion?
W12
- corpus luteum no longer
Placentation
- formed from what
- timing
- formed from embryonic and maternal tissues
- Corionic villi of the embryo and decidua basalis (basal layer of uterine lining)
- completed by W12
Describe the formation of the placenta
- Chorionic villi projections formed by trophoblasts fill with embryonic vasculature and invade the functionalis.
- The decidua basalis forms from endometrium between the stratum basalis and chorionic villi and fills with maternal vasculature
Describe the amnion
- membranous sac
- surrounds embryo
- broken only by umbilical cord
- filled with amniotic fluid: maternal fluid and fetal urine
- allows free fetal movement
- is turned over every 2 hours
- provides thermostasis
What are three extra-embryonic membranes?
- yolk sac
- chorion
- allantois
Yolk sac
- formed from what
- function
- forms from embryonic disc cells
- produces fetal blood (no liver or bone marrow yet)
- germ cells seed gonads
Chorion
- forms what
- function
- forms placenta
- later fuses with amnion to form amniochorionic membrane
Allantois
- location
- forms what
- out pocket of yolk sac
- forms base for umbilical cord
- becomes part of urinary bladder
Gastrulation
- describe
- when
- formation of three layered embryo from two layered inner cell mass
- Forms three primary germ layers: ectoderm, endoderm, mesoderm
- Primitive streak develops: establishes bilateral symmetry and orientation
- Days 14-21
What do the ectoderm, endoderm, and mesoderm become?
- Ectoderm: skin and nervous system
- Endoderm: epithelial linings
- Mesoderm: notochord and everything else
Notocord formation
- first organ to form
- derived from mesoderm
- gives signal for neurulation
- forms axial support
- replaced later by vertebral column
- persists as nucleus pulposus of intervertebral discs
Neurulation
- from ectoderm
- surrounds notocord
- detaches once neural tube is formed
- Anterior end forms brain and posterior end forms spinal cord
Timing of important phases of neurulation
- forms neural plate D7
- forms neural folds D21
- forms neural tube D23
What does the neural crest give rise to?
- cranial, spinal, sympathetic ganglia
- adrenal medulla
Endoderm organogenesis
- folds laterally, anteriorly, and posteriorly
- edges fuse to form gut lining
- oral and anal opening perforate lining
- outpockets form mucosal linings and glands of respiratory and GU systems
Mesoderm organogenesis
- once notochord is formed, somites form
- somites are 40 pairs of mesodermal blocks
- complete at end of W4
three portions of mesoderm organogenesis and what do they form?
- Sclerotome: vertebrae
- Myotome: skeletal muscle
- Dermatome: dermis of skin
Fetal circulation
- yolk sac and mesoderm form blood cells
- mesoderm spreads to form vascular network
- End of W3 2 vessels have fused and bent to form rudimentary heart
- fetal circulation bypasses the liver and lungs
- When does the rudimentary heart start pumping?
- when is the CVS functional?
- W4
- W8
List the 5 fetal vascular modifications and what happens after birth
- umbilical vein: constricts/fibroses into ligamentum teres of round ligament of liver
- Ductus venosus: collapses, ligamentum venosum on undersurface of liver
- Foramen ovale: flap closes due to high L side pressure, fuses into fossa ovalis
- Ductus arteriosus: constricts and remains a fibrous connection between pulmonary artery and aorta
- Umbilical arteries: constrict/fibrose, persist as superior vesical arteries that supply the bladder and as umbilical ligaments
Umbilical vein
Carries freshly oxygenated blood and nutrient rich blood from placenta to embryo
Ductus venosus
sends blood from umbilical vein to IVC (nutrients skip gut/liver)
Foramen ovale
oval opening in interatrial septum
Ductus arteriosus
Between pulmonary artery and aorta
Umbilical arteries
bilateral branches from internal iliac arteries, deliver blood to placenta
Sexual determination
- genetic gender determined at moment of fertilization
- XX vs. XY
Sexually indifferent stage
- when
- describe
- W 5-6
- gonadal ridges of mesodermal derivation are the pre-gonads, become seeded with gametogonia from yolk sac (can be either sex, destined to go through meiosis)
- 2 ducts form: paramesonephric (Mullerian) and mesonephric (Wolffian)
Male sex differentiation
- gonadal ridges develop into gonads
- If have Y chromosome, around W7 gonads become testes and secrete testosterone
- Seminiferous tubules develop from gonadal ridges
- Gonads merge with mesonephric tubes (Wolffian) to develop into male anatomy
- mesonephric ducts form remaining duct system
- paramesonephric (Müllerin) ducts degenerate
Female sex differentiation
- “default”
- Around W8 if no testosterone gonads develop into ovaries
- cortical portion forms follicles
- paramesonephric ducts develop into female duct system
- mesonephric ducts degenerate
Sexual differentiation
- what three structures develop into male or female sexual organs
- genital tubercle
- urethral folds
- labioscrotal swellings
Sexual differentiation: male
- when is it a “male” embryo
- describe formation of genitalia/organs
- XY embryo at W8
- genital tubercle: enlarges, become penis
- Urethral folds: fuse to enclose urethral groove, form penile urethra and meatus
- Labioscrotal swellings fuse to become scrotum
Sexual differentiation: female
- when is it a “female” embryo
- describe formation of genitalia/organs
- XX embryo at W8
- genital tubercle: becomes clitoris
- Urethral folds: form labia minora
- Labioscrotal form labia majora
Descent of testes
- when
- describe
- about W32
- migrate through inguinal canal into scrotum, drag blood and nerve supply
- gubernaculum cord assists and becomes part of spermatic cord
- tunica vaginalis is parietal peritoneum
Descent of ovaries
- when
- describe
- about W32
- descend a short distance
- gubernaculum splits to become ovarian and round ligaments
6 Anatomical changes in pregnant body
- increase in vascular network and engorgement of blood in reproductive organs
- Chadwick’s sign - blue vagina
- Breasts enlarge and areolas darken
- Melasma
- Hypertrophy of myometrium
- Amniotic fluid increases
Timing in pregnancy
- when does uterus occupy the pelvic cavity
- When is the fungus above the umbilicus
- when is the fundus at the xiphoidal process
- 16 weeks
- 7 months
- 9 months
What is approx pregnancy weight gain?
30 lbs
Gi physiologic changes during pregnancy
- increased salivation
- n/v
- GERD
- constipation
urinary physiologic changes during pregnancy
- fetal metabolic waste
- increased volume load
- increased frequency of urination
respiratory system physiologic changes during pregnancy
- nasal mucosa congestion
- nosebleeds
- increased respiration rate and vital capacity
- dyspnea
Cardio physiologic changes during pregnancy
- increased blood volume 25-40%
- increased bp
- increased hr
- decreased venous return
- varicosities
- increased CO by 20-40%
7 placental hormones
- Human placental lactogen
- Human chorionic thyrotropin
- Relaxin
- HCG
- Progesterone
- Estrogen
- Oxytocin
Human placental lactogen
- Enhances E and P effect on mammary tissue
- glucose sparing effect for female (need to keep blood glucose appropriately high to support fetus)
- promotes fetal growth
Human chorionic thyrotropin
- similar to TSH
- stimulates thyroid and increases metabolism
Relaxin
- produced by corpus luteum, placenta, and mammary glands
- relaxes pubic symphysis and other joints
- softens and dilates cervix
HCG
- produced by corpus luteum and placenta
- induces progesterone production
Progesterone
- maintains uterine lining
- quiets uterus
- thickens cervical mucus
- inhibits lactation during pregnancy
Estrogen
- steadily increases during pregnancy
- overwhelms progesterone near term (need uterine contracts to deliver!)
- stimulates oxytocin receptors on myometrium
Oxytocin
- produced by fetal cells and hypothalamus (posterior pituitary)
- acts on placenta
- stimulates release of prostaglandins
- causes uterine contractions
- positive feedback with hypothalamus
- creates strong rhythmic uterine contractions of labor
Three stages of labor
- dilation stage
- expulsion
- placental stage
Dilation stage
- cervix effaces and thins
- contractions at fundus (later whole uterus)
- engagement
Expulsion stage
- full dilation
- contractions Q2-3 min, last 1 min
- urge to push
- crowning
- birth
Placental stage
- uterine contractions compress blood vessels to limit bleeding
- allows detachment
- delivered about 15 min after expulsion
- inspect to ensure all parts have been delivered, none retained
First breath
- CO2 accumulates
- acidosis occurs: respiratory centers in brain stem are stimulated and cause first inspiration
- surfactant reduces alveolar surface tension
- Rate is 45+ for first two weeks
Normal rr for children
- newborn to 6 months: 30-60
- 6-12 months: 24-30
- 1-5 years: 20-30
- 6-12 years: 12-20
Prolactin-releaseing hormone (PRH)
- released from hypothalamus
- in response to elevated E, P, lactogen and suckling
- target is anterior pituitary
- stimulates release of prolactin
Prolactin
- anterior pituitary in response to PRH
- targes mammary glands
- stimulates milk production
- initiates lactation post birth, takes a few days
What is initial milk called? describe it
- Colostrum
- high in protein, vitamin A, sodium chloride
- lower CHO, lipids, potassium than mature milk
Oxytocin and lactation
- released from posterior pituitary
- response to cervical and nipple stretch and infant suckling
- targets uterus and alveolar glands
- stimulates release of milk and duct contractions
- let down reflex
