Reproductive Physiology & Gamete Biology Flashcards
Define “histology.”
The study of microscopic tissues
What is the difference between oogenesis and folliculogenesis?
Oogenesis refers to the physiological principles involved in oocyte formation, whereas folliculogenesis refers to the growth of the oocyte and follicles during their morphological development after activation.
From what part of the ICM does the urogenital system originate in mammals?
The intermediate mesoderm
In the absence of the Y chromosome, the expression of what gene is required to signal the developmental fate of an indifferent embryonic gonad toward the ovary?
The Wnt4 gene
What gene on the Y chromosome inhibits the expression of the Wnt4 gene in the indifferent embryonic gonad (and thus promotes the male sexual development system)?
The Sry gene
What duct regresses and what duct differentiates into the female reproductive tract in a female embryo?
The Wolffian duct; the Mullerian duct
In what direction does the Mullerian duct differentiate?
Cranial to caudal (head to tail)
Define “caudal.”
I.e. “tail”
What does the Mullerian duct differentiate into in a female embryo?
into the oviduct, the uterus, the cervix, and the upper one-third of the vagina.
What type of hormones control the early embryonic reproductive system development?
Steroid hormones
What are the major organs of the female reproductive system?
- Genital tract, 2. Ovaries, and 3. Pituitary
Name the four parts of the female genital tract.
- Vagina, 2. Cervix. 3. Uterus, and 4. Fallopian tubes
All organs of the genital tract share what three basic structural anatomic features?
- Protective outer serosal layer, 2. Wall of smooth muscle, 3. Inner mucosal layer
What does “GF-1” or “IGF-1” stand for?
The protein Insulin-like Growth Factor-1
What is IGF-1 and where is it produced?
A hormone similar in structure to insulin which works with Growth Hormone (made by the pituitary gland) to reproduce and regenerate cells. GF stimulates the liver to produce IGF-1.
“Stem Cell Factor” is also known by what four names/acronyms?
- KIT-ligand (KL or KIT-L)
- Mast Cell Growth Factor
- Steel Factor (where Steel is a mouse mutant)
- Stem Cell Factor (SCF)
What is Kit?
The receptor (ligand) for Stem Cell Factor.
What is Stem Cell Factor (SCF)?
A cytokine that binds to the c-KIT receptor (KIT-L) and plays an important role in hematopoiesis, spermatogenesis, and malanogenesis (producing melanin).
Define “mast cells.”
A type of leukocyte similar in structure and function to basophil that is produced in bone marrow.
Define “hematopoiesis.”
Production of blood cells.
What types of proteins are SCFs and KIT-Ls, respectively?
Glycoproteins (either membrane-bound or soluble) and receptor protein tyrosine kinases.
What is the name of the protein for which the acronym “bFGF” stands?
Basic Fibroblast Growth Factor
What two acronyms can be used for Basic Fibroblast Growth Factor?
- bFGF (or BFGF)
2. FGF-beta
What is the name of the protein for which the acronym “KGF” stands for?
Keratinocyte Growth Factor
What two acronyms can be used for the protein Keratinocyte Growth Factor?
- KGF
2. FGF-7
What is the “vagina” and what are its three functions?
It basically consists of a muscular tube that connects the uterus to the exterior, it serves as:
- Birth canal during parturition;
- An excretory duct for the passage of menstrual components;
- The site of sperm deposition after coitus.
Explain two characteristics of the vaginal mucosal layer.
- Composed mostly of non-secretory stratified squamous epithelium
- Releases glycogen into the lumus via poorly-developed intercellular mechanisms
How is glycogen metabolized in the vagina?
Through bacterial flora that convert it into lactic acid
What is the purpose of the acidic vaginal environment?
To create a more hostile environment for pathogens
Explain the pH gradient from vagina –> cervix
- Lactic acid causes low vaginal pH.
- Cervical secretions contain buffers that neutralize the pH.
- This results in a gradient from external opening of vagina (pH = 4 to 5) to the opening of the cervix (pH = 6 to 7), as the cervix pH is 7 to 8.
At the end of the follicular phase, under the influence of what hormone, is cervical fluid thin and watery and why?
Estrogen; allowing the entrance of sperm into the uterus at the time of ovulation
During the remainder of the menstrual cycle, under the influence of what hormone, does cervical mucus thicken and why?
Progesterone; to inhibit entrance of any materials from the vagina
Define “innervated.”
Supply an organ or body part with nerves
Why is the cervix highly innervated and where do these direct nervous pathways lead to??
Mechanical stimulation of the cervix is a potent stimulator of oxytocin secretion by the posterior pituitary (where the direct nerve pathways lead to); this is why pressure on the cervix during later pregnancy by the fetus stimulates oxytocin secretion, which is one of the major initiators of parturition.
What is the muscular layer and the mucosal layer of the uterus called, respectively?
Myometrium and endometrium, respectively
The muscular and mucosal layer of the uterus is more complex than which organs?
Vagina and fallopian tubes
What is the myometrium of the uterus primarily responsible for?
Expulsion of the fetus during parturition
Under the influence of what hormone does the uterine myometrium become quiescent?
Progesterone
What are the two distinct roles the testis plays?
- Exocrine (production of mature sperm)
2. Endocrine (production and secretion of androgens)
What is the average testicular volume in healthy young men?
20cc each
What happens to testicular volume as men age?
Decreases
What is the normal longitudinal length of the testis?
4.5-5.1cm
What is the thick protective covering of the testis called?
Tunica albuginea
What is the testis suspended by and what does this structure contain?
Spermatic cord; contains vas deferens, spermatic artery, and venous and lymphatic plexa.
The seminiferous tubules occupy approximately what percent of the testicular volume?
80%
What are the three layers of the tunica encapsulating the testis?
- Tunica vasculosa
- Tunica albuginea
- Tunica vaginalis
What are the lobules in the testis composed of and where do they terminally end?
Four seminiferous tubules; rete testis, respectively
What is an approximate length and diameter of a seminiferous tubule?
30-70cm long; 150-250micrometers, respectively
What is the rete testis also called?
Efferent ducts (ductuli efferentes)
Where do the rete testes lead to?
Caput (head) of the epididymis
What signal-transduction pathway do Leydig cells use for steroidogenesis?
cAMP-mediated signal transduction pathway
What are three characteristics of Leydig cells?
- Lipid droplets
- Mitochondria with tubular cristae
- Smooth endoplasmic reticulum
When are the first androgens secreted from the testes and why?
Prenatal development; Leydig cells are steroidogenically active between weeks 8-18 gestation and later at puberty and subsequently.
What hormone induces the expression of the LH receptor?
Prolactin
What are the five sub-stages of prophase?
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis
What four hydrolytic enzymes are contained in the acrosome?
- Hyaluronidase
- Neuraminidase
- Phosphatase
- Trypsin-like protease
What differentiates to form the flagellum in sperm?
Centrioles
What phagocytizes the residual cytoplasm in a maturing sperm cell?
Sertoli cells, as the spermatozoa are released into the lumen of the seminiferous tubule.
The entire cycle from spermatogonia to spermatozoa takes about how long in humans?
64 days
In the cycle of the seminiferous epithelium, how often and when do adjacent resting spermatogonia initiate a new cycle?
Every 16 days (plus or minus one); when the primary spermatocytes initiate prophase I, a second cycle is activated.
What four organelles do sperm lack and what two functions do they not perform, respectively?
- Ribosomes
- Nuceloli
- RER
- Golgi apparatus;
- Synthesis RNA
- Secrete
How often does a sperm tail beat?
10 times/second
What six things can negatively impact sperm motility?
- Alcohol
- Drugs
- Tobacco
- Sexual lubricants
- Saliva
- Genetic factors
What six things can negatively impact sperm motility?
- Alcohol
- Drugs
- Tobacco
- Sexual lubricants
- Saliva
- Genetic factors
What four parts of the production of sperm requires direct hormonal control?
- During the development of the fetal testis, the transformation of the primordial germ cells to the primitive Type A spermatogonia MAY require testosterone.
- The initial division of Type B spermatogonia doesn’t need gonadotropins or gonadal steroids but MAY require growth hormone.
- The process of reductive division (primary to secondary spermatocytes) requires testosterone.
- Spermiation (releasing spermatids into the lumen of the seminiferous tubules) requires testosterone.
What muscle in the scrotum raises the testes closer to the body when the ambient temperature is low, and relaxes to low the testes away from the body when the ambient temperature is hot?
Cremasteric muscle
What is the pampiniform plexus and what does it do?
A network of interconnected veins which drain blood from the testes; maintains testicular temperature.
What is the primary goal of ovarian stimulation?
To statistically increase the odds of treatment success by increasing the opportunities available to find the right follicle
Multi follicular development must occur in a setting which simultaneously does what?
Optimizes the biological potential of the gametes which are obtained
What does “premium non nocere” mean?
Do no harm.
What are two examples of serious complications that should be avoided during ovarian stimulation?
- Multiple gestations
2. OHSS
What are four factors that should be considered for a patient’s ovarian stimulation treatment plan?
- Medication
- Monitoring cost
- Medication side effects
- Risk of cycle cancellation
At midgestation, how many follicles does a female embryo have?
6-7 million (the maximum number)
Beginning at midgestation, what happens to follicles?
They begin to undergo atresia and apoptosis
At birth, a female has roughly how many follicles?
1-2 million
After birth, does the rate of follicular loss accelerate or decelerate?
Accelerate
When does the rate of follicle loss stop accelerating?
Mid-thirties
Define “monotocous.”
Ovulating a single egg at a time (i.e. humans)
Are primordial follicles responsive to gonadotropins?
No
What possibly impacts the size of the cohort of follicles available to a female during each cycle?
The residual pool of inactive primordial follicles
What appears to play a role in the development of primordial follicles?
Androgens
What three stages of follicular development are Gn-independent?
- Primordial
- Primary
- Secondary
What two stages of follicular development are Gn-dependent?
- Pre-Antral
2. Antral (Graffian)
What occurs during the preantral-early antral transition and what is important to know about this stage?
Formation of the theca cell layer, which is the most susceptible to follicular atresia
Once follicles progress and up regulate their gonadotropin receptors to become gonadotropin sensitive, what is there a narrow window for?
Narrow window of time that FSH is required to rescue them from atresia and apoptosis
The follicle destined to ovulate is recruited when in the cycle?
First few days
The appearance of gonadotropins is apparent in what phase of the prior cycle?
Luteal
If no pregnancy occurs, what happens to estrogen and progesterone, FSH and LH (respectively), and why?
The levels decline and this release of negative feedback at the level of the hypothalamus and pituitary causes up regulation of FSH and LH.
When do gonadotropins peak in a cycle?
Day 3
Is follicular response strictly dose related?
No, not at the extremes
What is the mechanism for Clomiphene citrate?
Occupies estrogen receptors at the hypothalamus and causes an inaccurate interpretation of circulating estrogen levels. The hypothalamus perceives an artificially low level of estrogen levels which alters the GnRH secretion and increases pituitary output of FSH and LH. This allows for multi follicular development.
How is clomiphene citrate administered and why?
As a 5-day course (doses from 50mg to 150mg), because it is a racemic mixture and the cis-isomer (enclomiphene) is more potent and responsible for inducing follicular development, but has a short half-life and is cleared rapidly as opposed to trans-isomer (zuclomiphene) which has a longer half-life.