Module 4: Reproductive System Flashcards
oogenesis? explain the events in relation to meiotic development.
oogenesis the the process by which oocytes develop and mature within the ovaries.
1. oogenesis begins before birth, meiosis begins but in the first meiotic division, it arrests. it does not become a haploid cell
2. prophase - early life, primordial follicles are being stimulated to grow, the oocyte is growing larger but it is still arrested, thus it remains a diploid cell (primary oocyte).
3. from puberty, once production of hormones that can control follicle growth, the follicle starts to reach antral follicle stage to get ready to ovulate. meiosis one is completed then production of a secondary oocyte (haploid) and polar body which eventually degenerates.
4. once ovulation occurs, the second meiotic division occurs and arrests again at metaphase II.
5. meiosis is only ever completed if fertilised by sperm. if not, it just degenerates
6. if sperm does fertilise oocyte then a haploid cell is created, one ovum and a second polar body.
folliculogenesis?
process of maturation of the ovarian follicle, which contains an immature oocyte. this process involves the progression of a number of small primordial follicles into large preovulatory follicles that occurs in part during the menstrual cycle.
primordial follicle?
small, simple oocyte with one layer of cell surrounding. they sit non-growing as a pool of oocytes waiting to be stimulated (throughout the woman’s whole life) in little batches to grow into primary follicles. gradually die throughout the life of a woman, only very few that go on to ovulate.
preantral follicle?
early growing phase - early stages of development, it is characterised by the absence of an antrum which is a fluid-filled cavity adjacent to the oocyte. granulosa cells form around oocyte, with primary follicle only has one layer of granulosa cells, when it becomes multi-layered, it becomes a secondary follicle. theca cells are on the outside of the cell, basement membrane separating.
antral follicle?
early antral follicles - granulosa cells are growing and spaces in the granulosa cells are forming, fluid is starting to accumulate. theca layer is sectioned into two layers, the theca externa and the theca interna.
antral follicle - becoming larger, little spaces join and the formation of a large antrum, all fluid inside which is supporting the growth of the oocyte. the oocyte is getting large and granulosa cells are lining the antral cavity while cells round the oocyte have been differentiated into a different cell type called cumulus cells.
corpus luteum?
a hormone (progesterone, estradiol) secreting structure that develops in an ovary after an ovum has been discharged but degenerates after a few days unless pregnancy has begun.
gonadotropin?
a type of hormone produced by the anterior pituitary gland which stimulate the activity of the gonads.
LH?
Luteinizing hormone is a hormone secreted by the anterior pituitary gland and is stimulated by a gonadotropin-releasing hormone from the hypothalamus.
In females, it stimulates ovulation and helps with the hormone production needed to support pregnancy. In males, it stimulates the synthesis of androgen.
FSH?
follicle-stimulating hormone. a hormone produced by the pituitary gland in the brain which plays an important role in sexual development and reproduction.
GnRH?
Gonadotropin releasing hormone. A hormone responsible for the release of follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) from the anterior pituitary
HPG?
Hypothalamic-pituitary-gonadal axis. A hormone-regulating mechanism containing three different component structures that operate in a coordinated fashion and which are involved in the regulation of several reproductive and developmental processes in humans and other species. It operates through a feedback loop involving hormones released from the gonads and the pituitary gland and the hypothalamus.
Theca cells?
A group of endocrine cells in the ovary that play an essential role in fertility by producing androgen. made up of connective tissue surrounding follicles.
Granulosa cells?
type of cell found in the ovaries, produce hormones, progesterone and estrogen. these hormones regulate menstrual cycle, follicle growth and ovulation
Androgens?
a group of sex hormones, they help start puberty and play a role in reproductive health and body development
Progesterone?
major source: ovary
stimulus for release: LH
feedback effects exerted: negative feedback on gonadotropin release by anterior pituitary and GnRH release by the hypothalamus.
effects on reproductive organs cooperates with estrogen in stimulating the growth of breasts, promoting the secretory phase of the uterine cycle and stimulates the production of cervical mucus.
metabolic effects: promotes diuresis and increases body temperature
Estrogen?
major source: ovary - developing follicles and corpus luteum
stimulus for release: FSH and LH
feedback effects exerted: both negative and positive feedback on gonadotropin release by the anterior pituitary and GnRH release by the hypothalamus
effect on reproductive organs: stimulate growth and maturation of reproductive organs and breasts at puberty and maintain their adult size and function.
infundibulum?
a funnel shaped structure that is part of the fallopian tube in the female reproductive system. it captures the newly ovulated oocyte.
ampulla?
part of the fallopian tube and is the widest section of the tube and is the primary site for fertilisation
fimbriae?
the fimbriae of the uterine tube, also known as fimbriae tubae, are small, fingerlike projections connected to the end of the fallopian tubes, through which eggs move from the ovaries to the uterus.
isthmus?
a small region which connects the ampulla and infundibulum to the uterus. egg fertilisation occurs in ampulla, then the eggs travel through the isthmus into the uterus.
seminal plasma?
fluid composed from secretions from glands in the male urogenital tract that provides a nutritious and protective medium for the spermatoza during their journey through reproductive tract
seminal fluid (semen)?
organic body fluid that contains spermatoza and is secreted by the gonads of males and can fertilise the females ovum
seminal vesicles?
a pair of convoluted tubular glands that lie behind the urinary bladder of males, they secrete a fluid that partly composes the semen.
bulbourethral glands?
two small exocrine glands in the reproductive system of males, produces a pre-ejaculate fluid called Cowper’s fluid which is secreted during sexual activity.
prostate?
a gland found in males, main function is to produce the major fluids that make up semen
corpora cavernosa?
two columns of spongy tissue in the shaft of the penis, this is responsible for an erection. The cavernosa forms most of the penis. They are filled with erectile tissue. This tissue contains nerves, blood vessels, and muscle fibers.
corpus spongiosum?
corpus spongiosum is the third tissue group that is involved in penile erection. contains the urethra, the tube through which urine and semen exit the body, and extends to form the glans penis, an expanded cap at the tip of the penis.
capacitation?
Capacitation is the process in which sperm undergo changes in the female reproductive tract that make them capable of fertilizing an egg. This process involves the removal of a glycoprotein coat, increased motility, changes in the sperm’s membrane, and preparation for the acrosomal reaction, which is essential for sperm to penetrate and fertilize the egg.
acrosome reaction?
The acrosome reaction is a crucial step in fertilization, specifically in the process of sperm-egg interaction.
- approach - aided by enzymes on its surface, a sperm cell weaves its way past cumulus cells.
- acrosome reaction - binding of the sperm to receptors in the zona pellucida causes Ca2+ levels within the sperm to rise, triggering the release of acrosomal enzymes. acrosomal enzymes form many holes in ZP.
- binding - After path cleared in ZP, 1 sperm forcibly swims towards oocyte membrane (oolemma). Sperm membrane binds to the oolemma
- fusion -
* Oocyte and sperm membranes fuse
* Only sperm nucleus and
centrioles enter oocyte
* Sperm cell membrane, tail,
mitochondria left behind - Blocks to polyspermy - oocyte membrane block and cortical reaction
zona pellucida?
The zona pellucida is a protective glycoprotein layer that surrounds the egg and plays a critical role in fertilization by serving as a barrier, aiding in sperm binding, inducing the acrosome reaction, and ensuring species-specific recognition.
cortical reaction?
The cortical reaction is a process that occurs in the egg after fertilization to prevent multiple sperm from entering. It involves the release of cortical granules, which modify the zona pellucida (the egg’s protective layer) by making it impermeable to other sperm. This reaction ensures that only one sperm can successfully fertilize the egg, preventing genetic abnormalities.
zygote?
A zygote is the initial cell formed when a sperm cell fertilizes an egg cell. It contains a combination of genetic material from both parents and marks the beginning of the development of a new individual.
morula?
A morula is an early-stage embryo that forms a few days after fertilization, typically around the third day in human development.
The morula is composed of a tight cluster of cells and is the precursor to the blastocyst, the next stage in embryonic development. During this stage, the embryo undergoes multiple rounds of cell division, and the cells do not significantly increase in size. The morula eventually develops into the blastocyst, which consists of two main cell types: the inner cell mass, which gives rise to the future organism, and the outer trophoblast cells, which play a crucial role in implantation in the uterine wall.
describe process of implantation of blastocyst?
A blastocyst is an advanced stage in the development of an embryo, typically occurring about five to six days after fertilization in humans.
Day 4 - early blastocyst hatches from zona pellucida
- blastocyst floats in uterine cavity for 2-3 days
- implantation begins 6-7 days after ovulation, trophoblast cells adhere to uterine endometrial epithelium
Day 6 - blastocyst adheres to uterine wall
Day 7 - implantation begins as trophoblast cells invade uterine wall
Trophoblast cells proliferate and differentiate into 2
layers:
- Cytotrophoblast cells, inner layer of cells
- Syncytiotrophoblast cells, outer layer,
lose plasma membranes → multinucleated mass,
invades and digests endometrium
Day 9: Implantation continues;
embryoblast has become a
bilayered embryonic disc.
* Blastocyst burrows into endometrial lining
* Endometrial cells cover and seal off implanted blastocyst
* Embryoblast/ICM cells differentiate into 2 layers:
- Epiblast cells → fetus
- Hypoblast cells → yolk sac
Day 11: Implantation complete;
amniotic sac and yolk sac form
* Implantation is usually completed by day
12 after ovulation, ~day 26 of the
menstrual cycle
* Corpus luteum is maintained by secretion of human chorionic gonadotropin (hCG)
* hCG secreted by trophoblast cells and then syncytiotrophoblast
* hCG levels rise until 2nd month of pregnancy, decline as placenta secretes progesterone and estrogen
inner cell mass?
The inner cell mass (ICM) is a cluster of cells within the blastocyst, an early-stage embryo. It has the potential to differentiate into all the various cell types and tissues of the developing organism, including organs and systems. The ICM forms the foundation for the future organism’s development, while the outer cell layer of the blastocyst, the trophoblast, is responsible for implantation and later gives rise to the placenta.
trophectoderm?
The trophectoderm is the outer cell layer of the blastocyst, an early-stage embryo. It plays a critical role in implantation, making direct contact with the uterine wall, and is responsible for the formation of the trophoblast, which is the precursor to the placenta. The placenta is essential for nourishing the developing fetus during pregnancy. The trophectoderm’s functions are vital during the early stages of pregnancy.
syncytiotrophoblast?
The syncytiotrophoblast is a specialized, multinucleated layer of cells that forms from the trophoblast during early pregnancy. It plays key roles in implantation by invading the uterine wall, in endocrine functions by secreting hormones like hCG, and in facilitating nutrient and gas exchange between the maternal bloodstream and the developing fetus. It is an integral part of the placenta and is vital for the success of early pregnancy.
cytotrophoblast?
The cytotrophoblast is the inner cell layer of the trophoblast, an essential structure in early embryonic development. It consists of undifferentiated, mononucleated cells and serves as a source of cells that can differentiate into various trophoblast cell types. These differentiated cells contribute to the formation of the syncytiotrophoblast, an outer, specialized layer, and play a crucial role in placental development and the establishment of pregnancy.
hypoblast?
The hypoblast is a layer of cells in the early embryo. It contributes to the formation of the extraembryonic membranes, especially the yolk sac, which provides nutrients and is involved in early embryonic circulation. The hypoblast is part of the bilaminar embryonic disc, along with the epiblast, and its cells eventually differentiate into various cell types, including those needed for the development of the primitive gut and the early digestive system.
spermatogenesis?
3 steps in the production and maturation of sperm (all occurring in the seminiferous tubule):
1. mitosis of spermatogonia (stem cells)
- starting at puberty, spermatogonia divide continuously with each division including a type A daughter cell remaining at basal lamina to maintain pool of dividing germ cells. and type B daughter cells moving toward lumen and developing into primary spermatocytes.
- meiosis: spermatocytes to spermatids
- meiosis I: primary spermatocyte undergoes meiosis I, forming two secondary spermatocytes
- meiosis II: secondary spermatocyte rapidly undergoes meiosis II to become two spermatids (4 in total) - spermiogenesis: spermatids to sperm
- spermatids contain correct haploid chromosomes
- still non-motile
- streamlining process: spermatid elongates, loses excess cytoplasm, forms a tail
spermiogenesis?
final stage of spermatogenesis, where the spermatids develop into mature spermatozoa.
sertoli cell?
also known as sustentacular cells or sustentocytes are nurse cells. they support the developing sperm, maintains blood-testis-barrier, provides nutrients from blood, secretes testicular fluid for sperm transport, phagocytosis, produces androgen-binding protein (ABP) and produces inhibin (-ve feedback to inhibit FSH release)
leydig cell?
interstitial cells - steroidogenic - produce testosterone in the presence of LH
peritubular?
- neuronal and vascular elements
- connective tissue, immune cells,
interstitial Leydig cells - Steroid (androgen) production
intratubular?
- seminiferous tubules
- lined with complex stratified
germinal epithelium - contains sperm cells and sertoli cells
- Sperm production
seminiferous tubules?
located within the testes, responsible for the production of spermatoza, known as male gametes.
androgen binding protein (ABP)?
a protein that is produced by sertoli cells in the seminiferous tubules of the testes. ABP increases the concentration of androgens inside the testes, which stimulates spermatogenesis
spermatogonia?
a cell produced at an early stage in the formation of spermatozoa, spermatogonia undergoes spermatogenesis to become mature spermatoza
spermatocytes?
the male gametocytes that give rise to sperm. they are diploid cells that undergo meiosis to form four haploid spermatids.
spermatids?
haploid male gametid that results from the division of secondary spermatocytes.
spermatoza?
male reproductive cells produced in the testes, they are haploid cells meaning that they contain half the number of chromosomes as a normal body cell.
rete testis?
the rete testis is a network of delicate tubules located in the hilum of the testicles that carries sperm from the seminiferous tubules to the efferent ducts
efferent ductules?
this connects the rete testis with the initial section of the epididymis. they maintain proper fluid concentration in the testes and propel sperm to the epididymis.
testosterone?
sex hormone that is associated with the development of male reproductive tissues. females and males produce testosterone, males producing significantly more.
pampiniform plexus?
a network of veins in the male reproductive system, the primary function of pampiniform plexus is to cool the arterial blood supplying the testes at a temp slightly lower the body’s core temp for sperm production.
progestin? and what are the two different types of contraceptive pill?
progestin is a synthetic form of progesterone.
1. The combined oral contraceptive pill (COC)
contains estrogen and progestin
2. The progestin only pill (POP)
COC?
The COC pill, or Combined Oral Contraceptive pill, is a birth control method that contains synthetic versions of estrogen and progestin hormones. It is designed to prevent pregnancy by inhibiting ovulation, thickening cervical mucus to hinder sperm movement, and altering the uterine lining to reduce the chances of implantation.
POP?
“Progestin-Only Pill.” It is a type of birth control pill that contains only progestin, a synthetic version of the hormone progesterone. These pills are often referred to as the “minipill” and are taken orally to prevent pregnancy.
ART?
“Assisted Reproductive Technology.” ART refers to a range of medical procedures and treatments that are used to help individuals or couples overcome infertility and achieve pregnancy when traditional methods have not been successful. These technologies involve various medical interventions to manipulate human eggs, sperm, or embryos.
IVF?
In Vitro Fertilization, is an advanced reproductive technology. The process involves stimulating the ovaries to produce multiple eggs, retrieving mature eggs, fertilizing them with sperm in a laboratory, culturing the resulting embryos, and transferring one or more healthy embryos into the woman’s uterus.
ICSI?
Intracytoplasmic Sperm Injection is a specialized technique used in assisted reproductive technology (ART), particularly in in vitro fertilization (IVF). It is employed when male infertility issues, such as low sperm count or poor sperm quality, may hinder natural fertilization. During ICSI, a single sperm is directly injected into an egg, ensuring fertilization.
PCOS?
Polycystic ovary syndrome. a common hormonal disorder affecting individuals with ovaries during their reproductive years. It is characterized by irregular menstrual periods, elevated male hormones, the presence of polycystic-appearing ovaries, and often associated metabolic issues. PCOS can lead to infertility, irregular cycles, and an increased risk of metabolic conditions like diabetes.
relationship between GnRH pulses and FSH/LH?
faster GnRH pulse rate, there is an increased LH rate, decreased FSH rate
slower GnRH pulse rate, there is an increased FSH rate, decreased LH rate
regulation of ovarian cycle? (2-cell-2 gonadotropin hypothesis)
- GnRH stimulates FSH and LH secretion.
- FSH and LH stimulate follicles to grow, mature and produce steroid hormones.
2-cell-2 gonadotropin hypothesis: the cholesterol from the blood is supplied to the theca cells, theca cells respond to LH and produce androgens. the androgens are then supplied across basement membrane to granulosa cells. granulosa cells have the receptor for FSH and respond to FSH and an enzyme, aromatase, converts those androgens to produce estrogens to fuel growth of more granulosa cells.
- negative feedback loop of estrogens and inhibin (produced by granulosa cells).
- positive feedback stimulates gonadotropin release
- estrogen levels continue to rise as a result of continued release by dominant follicle
- when levels reach a critical high value, brief positive feedback occurs on brain and anterior pituitary
- triggers LH surge - LH surge triggers ovulation and formation of the corpus luteum
- shortly after ovulation:
- estrogen levels decline
- LH transforms ruptured follicles into corpus luteum
- LH stimulates corpus luteum to secrete progesterone (and some estrogen) almost immediately - negative feedback inhibits LH and FSH release
- negative feedback from rising plasma progesterone and estrogen levels
- inhibin enhances inhibitory effect
- declining LH inhibits follicle development
If no fertilisation occurs:
- corpus luteum degenerates
- sharp decrease in progesterone and estrogen
- ends the negative feedback and cycle starts again
phases of the menstrual cycle? (28 day cycle)
- Days 1-5: menstrual phase
- gonadotropin levels begin to rise
- by day 5, growing follicles starting to produce estrogen
- functional layer of endometrium shed - Day 6 - 14: proliferative (preovulatory) phase
- LH steadily rising with surge just before ovulation
- FSH declining with increase just before ovulation
- rising estrogen levels - regeneration of the functional layer of the endometrium
- ovulation at the end of proliferative phase on day 14 - Days 15 - 28: secretory (postovulatory) phase
- begins immediately after ovulation
- most consistent in duration
- drop in LH, but level still high enough to support progesterone production by corpus luteum
- P promotes well-developed blood supply and endometrial glands to provide nutrient rich secretions to prepare for implantation
- P thickens cervical mucus to form a plug that blocks entry of more sperm, pathogens or debris
which phases occur before and after ovulation and what are the dominating hormone?
before - menstrual and proliferative phases occur before ovulation. dominating hormone - estrogen
after - secretory phase occurs after ovulation. dominating hormone - progesterone
describe testis migration
10-15 weeks
- Pelvic position
- Suspensory ligament
lengthens and
regresses
25-28 weeks
- Migrates over pubic
bone
- Reaches scrotum by
35-40 weeks
how does the pill work?
High plasma estrogen
* Inhibits secretion of FSH
(and to a lesser extent, LH)
via -ve feedback (hypo & pit)
* Inhibits follicle maturation &
ovulation
High plasma progestin
* Inhibits synthesis of LH
(via -ve feedback to the
hypothalamus & pituitary)
* Prevents LH surge
required for ovulation
High estrogen - very fluid, enhances sperm penetration into uterus
High progesterone - thickens cervical mucus, forms a mucus plug around the cervix and prevents sperm from gaining access to uterus
what are some common and rare side effects of the COC pill?
common:
- tender breasts
- nausea and bloating
- headache
- weight gain/water retention
- low sex drive
- spotting
- mood changes
rare:
- increased risk of blood clots
- increased risk of stroke
- increased risk of cancer
- migraines
-dizziness
- increased BP
what are some other hormonal contraceptive methods?
Vaginal ring
➢ Same hormones as COC pill, in place for 3 weeks
➢ >4 weeks – loses effectiveness
➢ Advantages: not affected by vomiting/diarrhoea (cf pill), no
daily commitment, fertility returns when removed
➢ Disadvantages: need to remember to remove and replace at correct time, expensive
Injection (e.g. Depo-Provera)
➢ Slow release, synthetic progestogen* injection
➢ Long Acting Reversible Contraceptive (LARC)
➢ Every 12 weeks
➢ Advantages: good if can’t take E, long-acting, stops
menstruation
➢ Disadvantages: return to fertility at cessation can be slow (up to 18 mths), doctor must inject
Implant (e.g. Implanon NXT)
➢ LARC – up to 3 years
➢ Similar to injection but return of fertility is faster
➢ Advantages: very effective, ‘implant and forget’,
reversible, periods lighter (or none)
➢ Disadvantages: must be implanted by trained doctor/nurse, bleeding may be erratic, can be painful when inserted, can move from original position
Hormonal IUD (e.g. Mirena, Kyleena)
➢ Synthetic progestogen (levonorgestrel)
➢ LARC – up to 5 years
➢ Alternative – copper IUD (no hormone)
➢ Advantages: effective if inserted correctly, reversible
➢ Disadvantages: must be implanted by doctor, increased risk for pelvic inflammatory disease and irregular bleeding,
can move out of place
what are common causes of infertility in women?
- Endocrine abnormalities
- Hypothalamic dysfunction
(Weight/strenuous exercise/stress/travel) - Pituitary disease
(Hypothyroidism/hyperprolactinemia) - Ovarian dysfunction
- PCOS, premature ovarian failure, abnormal follicle development
- Implantation abnormalities
- Luteal phase deficiency, ↓ progesterone production
- Delayed maturation of endometrium
what are clinical features of PCOS? (Reproductive, Endocrine and Metabolic)
Reproductive:
- Disrupted cycles and ovulations
- oligomenorrhea/amenorrhea
- Arrested follicle maturation
- Polycystic ovaries
Endocrine:
- Hyperandrogenism
- acne, hirsutism
- LH hypersecretion
Metabolic:
- Obesity
- Insulin resistance
- Increased risk of type 2 diabetes and cardiovascular disease
what are the female anatomical abnormalities that affect infertility?
- Tubal disease
Inflammatory scarring (STIs,
pelvic inflammatory disease),
septic abortion, surgery, IUD,
salpingitis - Tubal blockage
- Endometriosis
- Uterine fibroids/polyps/septum
endometriosis?
- Abnormal growth of
endometrial tissue outside the
uterus in pelvic cavity - Responds in normal way to
hormones → pain and fibrosis - Affects ovaries, fallopian tubes
and uterus - Can block movement of sperm
and egg/embryo in tubes
what are common causes of infertility in males?
- Varicocele – dilatation of Pampiniform plexus
- Reduced semen quality (increased temp)
- Vas deferens blockage
- Retrograde ejaculation – problem with ejaculation reflex
- Hypogonadotropic hypogonadism (Kallman Syndrome)
what are other risk factors for infertility?
- Overweight or obese
Oocyte quality
Sperm quality - Stress
Sperm production
Ovulation/cycles - Smoking
Sperm count/quality
Oocyte quality - Alcohol
Sperm count/quality
Impacts on ovarian reserve
Disrupted cycles - Age
– mainly female, some male
what are fertility tests for females?
- Blood tests and ultrasound – PCOS, endometriosis, ovulation,
fibroids, polyps, ovarian cysts etc - Ultrasound and/or X-Ray – checks for tubal blockage
- Ovarian Reserve – AMH (anti-mullerian hormone) level
what are fertility tests for males?
- Semen analysis – sperm count, motility, morphology
volume and consistency of seminal fluid
pH, leukocytes, fructose levels - DNA Fragmentation test – Sperm Chromatin Structure Assay
(SCSA) - Sperm agglutination – may be result of sperm Abs; common in
men who’ve had vasectomy
