Reproductive Physiology Flashcards
How are primary oocytes produced?
Produced by oogonia (stem cells) in the fetal ovaries
When/why does menopause start?
When there are no more functional primary oocytes
What phase are primary oocytes held in?
Meiosis I (unchanged from fetus)
What is released from the ovary at ovulation?
One secondary oocyte
When does completion of meiosis II begin?
When sperm contacts the egg (fertilization)
What are the two phases of the ovarian cycle?
- Follicular phase
2. Luteal phase
Follicular phase
Where the egg & granulosa cells develop up to the point of ovulation
Luteal phase
Where the leftover bits of the granulosa hang around & secrete hormones (mainly progesterone) to prepare the uterus lining (endometrium) for a zygote
Characteristics of a primary follicle
Has granulosa cells which grow & secrete fluid + produce an antrum
Characteristics of a mature follicle
Has a full antrum
Shoots out the peritoneal cavity
When does the luteal phase occur?
After the mature follicle leaves the peritoneal cavity
What is a primordial follicle?
Precursor to a primary follicle
Primordial cell: histology
Flat follicular cells
Primary follicle: histology
Cubodial granulosa cells
Zona pellucida = begins to form, stays until egg implants (protection; shell)
How does a primary follicle transition to a secondary follicle?
Granulosa cells proliferate & secrete follicular fluid which forms intracellular spaces
How does a secondary follicle transition into a mature follicle?
Antras join together –> shoots egg out
Granulosa cells continue to secrete follicular fluid (makes a continuous antrum around the oocyte –> mature follicle)
Granulosa cells around the oocyte = corona radiata
What happens when the hypothalamus detects low estrogen?
GnRH is released by the hypothalamus
What does GnRH do?
Gets LH and FSH released from the anterior pituitary
What does LH do?
Stimulates estrogen production (which inhibits GnRH/LH/FSH release)
*This doesn’t matter at this point bc the primary follicle just wants to grow
What happens when the primary follicle continues to grow?
Makes estrogen which stimulates GnRH/LH/FSH
What happens when LH surges?
Mature follicle ruptures + egg is released
What does the leftover follicle do after ovulation?
Converts itself into an endocrine gland (corpus luteum) which makes progesterone –> tells uterus to get ready for a zygote
Layers of the uterus
Myometrium
Endometrium (stratum basalis and then stratum functionalis)
Layers of the endometrium
Stratum basalis: always there
Stratum functionalis: gets thick & accepts fertilized egg, falls off
Where do most changes of the menstrual cycle occur?
In the endometrium
What is the purpose of the uterine cycle?
Prepares the endometrium for zygote implantation
How does the stratum functionalis develop?
Due to the proliferation of the endometrial stroma & elongation and growth of endometrial glands (provides nutrients for the zygote)
Phases of the uterine cycle
Menstrual phase: loss of the stratum functionalis
Proliferative phase: growth of stratum functionalis, endometrial glands get thicker & BVs get more spiral
Secretory phase: secretion of food for a fertilized egg
Estrogen levels during menstrual phase
Low
Cause of the proliferative phase
Release of estrogen
What causes the endometrium to become secretory?
Progesterone released by corpus lute
How is the endometrium rescued?
Pregnancy!
Stops the degeneration of the corpus luteum because implanting egg & placenta releases hCG
What is hCG + what does it do?
Human chorionic gonadotropin
Stops the menstrual cycle + tells the corpus luteum to keep making estrogen and progesterone
Progesterone effect with menstrual cycle
Progesterone inhibits uterine contractions & disintegration of the stratum functionalis
When can a fertilized egg implant on the endometrium?
A few days before or after ovulation
Parts of sperm
Acrosome: head, contains digestive enzymes to penetrate the zona pellucida
Nucleus: haploid chromosomes
Midpiece: supplies energy for flagellum (mitochondria)
Flagellum: provides motive power for swimming
Spermatogenesis
Stem cells (spermatogonia) constantly divide + undergo meiosis
1 stem cell = 4 sperm
Components of semen
Fluid from seminal vesicles
Sperm from vas deferens
Prostatic fluid from prostate
Seminal vesicle secretions
Makes up majority of semen
Secretions have fructose (food) and clotting proteins (allows for clotting of semen)
Prostaglandins (stimulates sperm to swim + uterus to contact)
Alkaline fluid
Prostatic fluid
Acidic/neutral fluid that provides a medium for sperm to swim
Has citric acid (nutrient for sperm)
Has protein digesting enzymes (breaks clot so sperm can swim out)
Purpose of bulbourethral glands
During arousal, bulbourethal glans release alkaline fluid intro the urethra to neutralize acidic urine & some mucus (so sperm don’t touch urethra wall) to decrease sperm damage during ejaculation
Similarities between 2 processes of gamete manufacture
FSH stimulates growth of gametes
LH stimulates production of hormones from the gonad
Hormones produced by the gonads feedback on the pituitary to decreased production of gonadotropins
What does LH stimulate?
Stimulates ovarian follicle to make estrogen & progesterone
Stimulates Leydig cells in the testes to make testosterone
How does negative feedback of the gonads occur?
Sex steroids!!
Requirements for fertilization
Male
- Has to be enough sperm per mL of semen
- Has to make its way up to the Fallopian tube
Female
- Egg has to be in the uterine tube
- Cervical mucus can’t be too thick
- The endometrium has to be in the secretory phase for a blastocyst
Blocks of polyspermy (x2)
- Cell membrane of the oocyte depolarizes (prevents other sperm from contacting)
- The ZP hardens (due to enzymes released by the oocytes) –> no more sperm can enter
Where is the site of fertilization?
The ampulla
Importances of the zona pellucida
So the zygote doesn’t implant in the uterine tube
Once in the endometrium, the buildup of fluid causes ZP to crack open so now the blastocyst can implant
What makes up the future placenta?
The trophoblasts
Purpose of the yolk sac
Source for early blood cells
Membrane for nutrient exchange
Temporary waste storage (produced by metabolically active cells)
Where does the amniotic cavity form?
Forms in the ectoderm –> completely surrounds the developing fetus
Purpose of the connecting stalk
Leads to the trophoblasts
Becomes the umbilical cord
What does the ectoderm give rise to?
Skin & nervous system (CNS)
What does the mesoderm give rise to?
MSK & blood vessels + lymphatics
What does the endoderm give rise to?
Tube-like structures (GI, GU & respiratory tracts)
What is the allantois?
Part of the yolk sack –> storage of waste
What does the head fold give rise to?
CNS, spinal cord
What does the tail end give rise to?
Sacral part of spinal cord
Parts of the endoderm
Foregut: pharynx - duodenum (supply: celiac trunk)
Midgut: supplied by superior mesenteric a.
Hindgut: distal colon - rectum (supply: inferior mesenteric a.)
Vessels of the umbilical cord (x3)
Large umbilical vein: supplies O2 rich blood from placenta –> fetus
2 smaller umbilical arteries: fetus –> placenta for waste
Three stages of development
- Pre-embryonic
- Embryo
- Fetus
Pre-embryonic phase of development
At the end of this phase, there is a tiny trophoblast
In the early parts of this phase, ZP is still present so embryo is isolated from maternal environment
Embryonic phase
All major organs are assembled in this time –> organogenesis
Placenta is now much larger than the embryo & complete access to maternal circulation
Fetal phase
Organs grow during this period –> histogenesis phase
Problems in embryonic development
Major dysgenesis in organ systems –> caused by drugs on the maternal side
Thalidomide (anti-nausea pill) = interfered with development of upper limb bud (phocomelia)
Valproic acid (anti-seizure medication) = interfered with the proper closure of the neural tube (spina bifida)
Problems in fetal development
Incomplete or abnormal development in organ systems
Microtia: incomplete growth of outer ear
Cataracts: lens are cloudy due to rubella virus (interrupted ion pumps within the lens)
What is the decidua?
Stratum basalis + functionalis = maternal contribution to the placenta (where the blood comes in)
What is the chorion?
Fetal contribution to the placenta (came from the trophoblasts)
Purpose of the amniotic sac
Absorbs mechanical vibrations & helps fetus to strengthen muscles (resistance against water)
What happens if there is too much amniotic fluid?
Can cause fetal distress during delivery
Can be caused due to diabetes at the time of pregnancy
Purpose of anchoring villus
So the placenta doesn’t detach
What are syncytiotrophoblasts?
Outer layer of cells that line the chorionic villi & separate maternal and fetal blood cells
Express very little MHC I molecules so the maternal immune system doesn’t attack
What are cytotrophoblasts?
Cells that invade the maternal side to anchor + go into the maternal arteries
What does extraembryonic mesoderm give rise to?
BVs in the chorionic villi
What is found in the intervillous space?
Maternal blood
Components of the umbilical cord
Gelatinous goo on the outside (Wharton’s jelly) = mesenchymal stem cells used to make MSK
Also fibroblasts (CT) and myofibroblasts (muscle)
What is the source for cord-derived mesenchymal cells?
Wharton’s jelly (extraembryonic mesoderm)
What is the source for blood-derived stem cells?
Cord blood
Purpose of syncytiotrophoblasts
Cover + hide fetal structures
Purpose of cytotrophoblasts
When trophoblasts invade the maternal endometrium, cytotrophoblasts will cover the SM –> allows for blood to fetus even under sympathetic stimulation
What would happen if the cytotrophoblasts didn’t completely cover the arteries?
Fetal side: intrauterine growth restriction (not enough nutrients to fetus)
Maternal side: hypertension (preeclampsia)
Maternal adaptions to pregnancy (x4)
- Cellular immunity decreases (must remain tolerant of paternal antigens)
- Increased blood volume and cardiac output
- Increased tidal volume (to increase CO2 loss: larger conc gradient)
- Myometrial mass increases greatly
Positive feedback during childbirth
- Pressure on cervix
- Stretch receptors in cervix –> hypothalamus
- OT released by post. pituitary (receptors are found on myometrium)
- Uterus contracts
How does the uterus wake up at term? (x4)
- Expression of lots of OT and prostaglandin (uterine contractions) receptors
- Stimulation/disinhibition of OT and PG production
- Decreased RMP (closer to threshold)
- More gap junctions expressed between myocytes
