Reproductive Physiology & Gamete Biology Flashcards
(230 cards)
1
Q
Define “histology.”
A
The study of microscopic tissues
2
Q
What is the difference between oogenesis and folliculogenesis?
A
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.
3
Q
From what part of the ICM does the urogenital system originate in mammals?
A
The intermediate mesoderm
4
Q
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?
A
The Wnt4 gene
5
Q
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)?
A
The Sry gene
6
Q
What duct regresses and what duct differentiates into the female reproductive tract in a female embryo?
A
The Wolffian duct; the Mullerian duct
7
Q
In what direction does the Mullerian duct differentiate?
A
Cranial to caudal (head to tail)
8
Q
Define “caudal.”
A
I.e. “tail”
9
Q
What does the Mullerian duct differentiate into in a female embryo?
A
into the oviduct, the uterus, the cervix, and the upper one-third of the vagina.
10
Q
What type of hormones control the early embryonic reproductive system development?
A
Steroid hormones
11
Q
What are the major organs of the female reproductive system?
A
- Genital tract, 2. Ovaries, and 3. Pituitary
12
Q
Name the four parts of the female genital tract.
A
- Vagina, 2. Cervix. 3. Uterus, and 4. Fallopian tubes
13
Q
All organs of the genital tract share what three basic structural anatomic features?
A
- Protective outer serosal layer, 2. Wall of smooth muscle, 3. Inner mucosal layer
14
Q
What does “GF-1” or “IGF-1” stand for?
A
The protein Insulin-like Growth Factor-1
15
Q
What is IGF-1 and where is it produced?
A
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.
16
Q
“Stem Cell Factor” is also known by what four names/acronyms?
A
- KIT-ligand (KL or KIT-L)
- Mast Cell Growth Factor
- Steel Factor (where Steel is a mouse mutant)
- Stem Cell Factor (SCF)
17
Q
What is Kit?
A
The receptor (ligand) for Stem Cell Factor.
18
Q
What is Stem Cell Factor (SCF)?
A
A cytokine that binds to the c-KIT receptor (KIT-L) and plays an important role in hematopoiesis, spermatogenesis, and malanogenesis (producing melanin).
19
Q
Define “mast cells.”
A
A type of leukocyte similar in structure and function to basophil that is produced in bone marrow.
20
Q
Define “hematopoiesis.”
A
Production of blood cells.
21
Q
What types of proteins are SCFs and KIT-Ls, respectively?
A
Glycoproteins (either membrane-bound or soluble) and receptor protein tyrosine kinases.
22
Q
What is the name of the protein for which the acronym “bFGF” stands?
A
Basic Fibroblast Growth Factor
23
Q
What two acronyms can be used for Basic Fibroblast Growth Factor?
A
- bFGF (or BFGF)
2. FGF-beta
24
Q
What is the name of the protein for which the acronym “KGF” stands for?
A
Keratinocyte Growth Factor
25
What two acronyms can be used for the protein Keratinocyte Growth Factor?
1. KGF
| 2. FGF-7
26
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:
1. Birth canal during parturition;
2. An excretory duct for the passage of menstrual components;
3. The site of sperm deposition after coitus.
27
Explain two characteristics of the vaginal mucosal layer.
1. Composed mostly of non-secretory stratified squamous epithelium
2. Releases glycogen into the lumus via poorly-developed intercellular mechanisms
28
How is glycogen metabolized in the vagina?
Through bacterial flora that convert it into lactic acid
29
What is the purpose of the acidic vaginal environment?
To create a more hostile environment for pathogens
30
Explain the pH gradient from vagina --> cervix
1. Lactic acid causes low vaginal pH.
2. Cervical secretions contain buffers that neutralize the pH.
3. 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.
31
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
32
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
33
Define "innervated."
Supply an organ or body part with nerves
34
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.
35
What is the muscular layer and the mucosal layer of the uterus called, respectively?
Myometrium and endometrium, respectively
36
The muscular and mucosal layer of the uterus is more complex than which organs?
Vagina and fallopian tubes
37
What is the myometrium of the uterus primarily responsible for?
Expulsion of the fetus during parturition
38
Under the influence of what hormone does the uterine myometrium become quiescent?
Progesterone
39
What are the two distinct roles the testis plays?
1. Exocrine (production of mature sperm)
| 2. Endocrine (production and secretion of androgens)
40
What is the average testicular volume in healthy young men?
20cc each
41
What happens to testicular volume as men age?
Decreases
42
What is the normal longitudinal length of the testis?
4.5-5.1cm
43
What is the thick protective covering of the testis called?
Tunica albuginea
44
What is the testis suspended by and what does this structure contain?
Spermatic cord; contains vas deferens, spermatic artery, and venous and lymphatic plexa.
45
The seminiferous tubules occupy approximately what percent of the testicular volume?
80%
46
What are the three layers of the tunica encapsulating the testis?
1. Tunica vasculosa
2. Tunica albuginea
3. Tunica vaginalis
47
What are the lobules in the testis composed of and where do they terminally end?
Four seminiferous tubules; rete testis, respectively
48
What is an approximate length and diameter of a seminiferous tubule?
30-70cm long; 150-250micrometers, respectively
49
What is the rete testis also called?
Efferent ducts (ductuli efferentes)
50
Where do the rete testes lead to?
Caput (head) of the epididymis
51
What signal-transduction pathway do Leydig cells use for steroidogenesis?
cAMP-mediated signal transduction pathway
52
What are three characteristics of Leydig cells?
1. Lipid droplets
2. Mitochondria with tubular cristae
3. Smooth endoplasmic reticulum
53
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.
54
What hormone induces the expression of the LH receptor?
Prolactin
55
What are the five sub-stages of prophase?
1. Leptotene
2. Zygotene
3. Pachytene
4. Diplotene
5. Diakinesis
56
What four hydrolytic enzymes are contained in the acrosome?
1. Hyaluronidase
2. Neuraminidase
3. Phosphatase
4. Trypsin-like protease
57
What differentiates to form the flagellum in sperm?
Centrioles
58
What phagocytizes the residual cytoplasm in a maturing sperm cell?
Sertoli cells, as the spermatozoa are released into the lumen of the seminiferous tubule.
59
The entire cycle from spermatogonia to spermatozoa takes about how long in humans?
64 days
60
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.
61
What four organelles do sperm lack and what two functions do they not perform, respectively?
1. Ribosomes
2. Nuceloli
3. RER
4. Golgi apparatus;
1. Synthesis RNA
2. Secrete
62
How often does a sperm tail beat?
10 times/second
63
What six things can negatively impact sperm motility?
1. Alcohol
2. Drugs
3. Tobacco
4. Sexual lubricants
5. Saliva
6. Genetic factors
64
What six things can negatively impact sperm motility?
1. Alcohol
2. Drugs
3. Tobacco
4. Sexual lubricants
5. Saliva
6. Genetic factors
65
What four parts of the production of sperm requires direct hormonal control?
1. During the development of the fetal testis, the transformation of the primordial germ cells to the primitive Type A spermatogonia MAY require testosterone.
2. The initial division of Type B spermatogonia doesn't need gonadotropins or gonadal steroids but MAY require growth hormone.
3. The process of reductive division (primary to secondary spermatocytes) requires testosterone.
4. Spermiation (releasing spermatids into the lumen of the seminiferous tubules) requires testosterone.
66
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
67
What is the pampiniform plexus and what does it do?
A network of interconnected veins which drain blood from the testes; maintains testicular temperature.
68
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
69
Multi follicular development must occur in a setting which simultaneously does what?
Optimizes the biological potential of the gametes which are obtained
70
What does "premium non nocere" mean?
Do no harm.
71
What are two examples of serious complications that should be avoided during ovarian stimulation?
1. Multiple gestations
| 2. OHSS
72
What are four factors that should be considered for a patient's ovarian stimulation treatment plan?
1. Medication
2. Monitoring cost
3. Medication side effects
4. Risk of cycle cancellation
73
At midgestation, how many follicles does a female embryo have?
6-7 million (the maximum number)
74
Beginning at midgestation, what happens to follicles?
They begin to undergo atresia and apoptosis
75
At birth, a female has roughly how many follicles?
1-2 million
76
After birth, does the rate of follicular loss accelerate or decelerate?
Accelerate
77
When does the rate of follicle loss stop accelerating?
Mid-thirties
78
Define "monotocous."
Ovulating a single egg at a time (i.e. humans)
79
Are primordial follicles responsive to gonadotropins?
No
80
What possibly impacts the size of the cohort of follicles available to a female during each cycle?
The residual pool of inactive primordial follicles
81
What appears to play a role in the development of primordial follicles?
Androgens
82
What three stages of follicular development are Gn-independent?
1. Primordial
2. Primary
3. Secondary
83
What two stages of follicular development are Gn-dependent?
1. Pre-Antral
| 2. Antral (Graffian)
84
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
85
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
86
The follicle destined to ovulate is recruited when in the cycle?
First few days
87
The appearance of gonadotropins is apparent in what phase of the prior cycle?
Luteal
88
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.
89
When do gonadotropins peak in a cycle?
Day 3
90
Is follicular response strictly dose related?
No, not at the extremes
91
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.
92
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.
93
What are the two side effects of clomiphene citrate?
1. Antiesrogenic effect causes hot flashes in 10-20% of women
2. Multiple gestation risk increased to 7-10% (primarily twins, with triplet risk being 0.3-0.5%)
94
What is letrozole?
A triazole (anti fungal) derivative and a potent, reversible, competitive inhibitor of aromatase
95
What is aromatase?
A microsomal cytochrome P450 enzyme which catalyzes the rate-limiting step in the production of estrogen, namely, the conversion of androstenedione and testosterone via three hydroxylation steps to estrone and estradiol respectively
96
How does letrozole work?
It blocks the aromatase enzyme (which catalyzes the rate-limiting step in the production of estrogen) and lowers estrogen production both in the periphery and in the brain at the level of the hypothalamus and pituitary. This results in a compensatory increase in pituitary release of FSH and LH which stimulates follicular growth. After the medication is discontinued and the follicles grow, normal negative feedback by estrogen at the level of the hypothalamus and pituitary will occur.
97
Why does letrozole lead to the ovulation of less oocytes than clomiphene citrate?
Because the discontinuation of letrozole, unlike CC, leads to normal negative feedback of estrogen which in turn suppresses FSH and allows smaller follicles to come atretic and undergo apoptosis. CC, on the other hand, apparently irreversibly binds to the estrogen receptors and this leads to a lack of negative feedback and a lack of FSH suppression, which results in more follicles developing.
98
How is letrozole given?
A 5-day course on cycle days 3-7 or 5-9, with doses ranging from 2.5-7.5mg
99
What are the four primary injectable medications for ovarian stimulation?
1. hMG
2. FSH
3. LH (or hCG)
4. long acting FSH
100
What two adjunctive treatments accompany the primary ones for ovarian stimulation?
1. DHEA (oral)
| 2. GH (subcutaneous injection)
101
What are hMG's?
Human Menopausal Gonadotropins; extracted from urine of postmenopausal women and a dose originally contained 75IU equivalents of FSH and LH (the LH bioactivity actually comes from urinary hCG). However, now due to better purification techniques, a dose with 75IU's of FSH has only 0.001IU of LH.
102
What is the difference between exogenous FSH and hMG?
FSH is recombinant and involves insertion of the genes encoding the alpha and beta subunits of FSH into the genome of a Chinese hamster ovary cell line, which allows for the production of bioactive, dimeric FSH which is purified utilizing immunochromatography and specific anti-FSH monoclonal antibodies, allowing for medication production without urinary proteins (like hMG).
103
What two types of recombinant FSH are available on the market today, and is there any difference in their biological activity?
Follitropin alpha and beta; no
104
Why is DHEA used in conjunction with ovarian stimulation treatment?
Because in some women with ovarian insufficiency, some level of androgen insufficiency may also exist and 50-75mg of Dehydroepiandrosternedione supplementation for 4 months may result in improved outcomes for natural conception or IVF conception, due to reports of modest increases in oocyte and embryo quality.
105
Why is GH used in adjunct with ovarian stimulation methods?
Meta-analysis have shown that, although GH supplementation did not increase COS response or number of oocytes, but both pregnancy and live with rates did increase, perhaps speaking to oocyte quality. This makes sense, because oocyte-granulose cells crosstalk with a number of growth differentiating factors stimulated by GH like IGF-1 and IGF-2.
106
How does OHSS occur physiologically?
Due to ovarian enlargement when multi follicular development occurs, there may be an acute shift of fluid out of the intravascular space.
107
What does the most severe OHSS cases include and what are five medical risks of this?
Third-space accumulation of fluid and hemoconcentration which can result in:
1. Renal failure
2. Acute respiratory distress syndrome
3. Thromboembolic disease
4. Hypovolemic shock
5. Death
108
Why doesn't OHSS happen in real life?
Because in natural cycles, feedback mechanisms prohibit excessive stimulation from occurring (aside from rare case reports of patients with PCOS or FSH receptor mutations)
109
What is the underlying pathophysiology of OHSS and when is the onset, typically, of symptoms?
Luteinization of large numbers of follicles; 5-10 days after the ovulatory trigger (respectively)
110
The GnRH agonist trigger can only be done in a patient who has what and what?
1. Functional hypothalamic-pituitary-gonadal axis at the outset
2. Has not been down-regulated as part of the IVF cycle regimen
111
What are the two most common ways employed to decrease the incidence or severity of OHSS?
1. Coasting, where the trigger medication is delayed until the estradiol falls to a more acceptable range (typically less than 2,500 to 3,000 pg/mL)
2. Substituting an hCG ovulation trigger, which has a long half-life, with a GnRH agonist trigger
112
What four criteria should affect patient starting dose of gonadotropins?
1. Patient age
2. Antral follicle count
3. Serum ovarian reserve testing
4. Information about prior response to gonadotropins
113
What three things are required to be monitored in women who develop OHSS?
1. Monitoring for hemoconcentration
2. Monitoring for hydration status
3. Monitoring for electrolyte disturbances
114
What three things may a patient require who develops OHSS and why?
1. Intravenous fluid to rehydrate and/or correct metabolic disturbances
2. Anticoagulant therapy if the risk of thromboembolism is high
3. Removal of excessive fluid from the third-spaces, such as the abdomen and the lungs
115
Why are, for some patients, a fresh transfer a bad idea?
Because the multi follicular development affects the uterine endometrium, with a premature rise in progesterone impacting embryo-endometrial synchrony
116
A 2013 Cochrane review concluded what about natural or minimal stimulation cycles in comparison to traditional, aggressive stimulation cycles?
A woman with a 53% chance of live birth with standard IVF stimulation has a 34-53% chance with a natural cycle.
117
What are the four pro's in a natural cycle IVF?
1. Decreased need for intensive monitoring, as the only goal is to retrieve the follicle before the mid-cycle LH occurs;
2. Little or no medication is required;
3. The cost is decreased by 75-80%;
4. The risk of OHSS is nearly eliminated.
118
What are the success rates for a natural IVF cycle?
~ 7%
119
Why are natural IVF success rates so low, in three reasons?
1. Cancellation due to premature LH surge
2. Lack of oocyte retrieved
3. Statistical disadvantage of a single oocyte
120
Many natural cycle IVF protocols have added what to the regimen in order to prevent premature LH surge?
An hCG or GnRH agonist trigger
121
What is another name for fimbria?
Infundibulum
122
Where in the fallopian tubes is the most common site of fertilization?
Ampulla
123
What is the final short segment of the fallopian tubes that connects it to the uterus called?
Isthmus
124
What does the oviduct's mucosal layer consist of and how many types can it be subdivided into?
Columnar epithelium; 2 types
125
What are the two sub-types of the fallopian tubes' mucosal layer?
1. Ciliated epithelium
| 2. Secretory epithelium
126
What three aspects of the fallopian tube epithelium fluctuates in response to estrogen and progesterone?
1. The ratio of ciliated to secretory cells
2. The direction of ciliary beating
3. The height of the cells
127
What part of the fallopian tubes contorts onto itself and why?
Mucosal layer; forming an intricate labyrinth of branching folds to offer a large ciliated surface area that potentiates the number of sperm that can be moved up the oviducts to the site of fertilization
128
Sperm transport up the oviduct to the ampulla is brought about by what three things?
1. Cilial propulsion
2. Myosalpingeal contractions
3. Their own (sperm) forward propulsion
129
What three things do the secretions of the oviductal secretory epithelium supply fluid for?
The movement of sperm and oocytes as well as nourishment to the gametes
130
What happens to the different areas of oviductal cilia under the influence of estrogen and why?
1. The cilia in the ampulla and isthmus beat in the direction of the ovary;
2. The cilia in the fimbria and the ampulla next to the fimbria beat in the direction of the uterus.
This is to sequester the oocyte within the middle of the ampulla
131
After ovulation, in the presence of increasing concentrations of what hormone do the cilia and myosalpingeal contractions pulse towards where and why?
Progesterone; from ovary to uterus; to move the presumptive embryo towards the uterus for implantation
132
The ovaries and testes both develop from what identical structure?
The embryonic genital ridge
133
What are the ovaries shaped like and how long are they?
Almond; 3-4cm long
134
What three things are the ovaries the site of?
1. Oogenesis
2. Folliculogenesis
3. Luteolysis
135
What are the two major structures of the ovary?
1. Follicle
| 2. Corpus luteum
136
What two things can be present alone or together at the ovary in various stages of development?
Follicles and/or corpus luteum
137
Define "stroma."
The supportive tissue of an epithelial organ, tumor, gonad, etc., consisting of connective tissues and blood vessels
138
What is the stroma of the ovary comprised of?
Connective tissue framework
139
Describe the connective tissue framework of the ovarian stroma.
Denser on the periphery (outer ovarian cortex) than its center (inner ovarian medulla)
140
What two things are contained in the ovarian cortex?
Follicles and corpus luteum
141
Describe the tunica albuginea of the ovary.
The outermost layer of the ovarian cortex, composed of thin but tough, dense protective coating made up of a network of connective tissue and devoid of any cell types
142
What three things are houses in the ovarian medulla and how do these things enter the ovary?
1. Ovarian blood vessels
2. Lymphatic vessels
3. Nerves
(They enter through the ovarian hilus)
143
The OUTERMOST layer of the ovary is called what?
Germinal (or cuboidal) epithelium
144
What is the germinal epithelium layer of the human ovary not associated with, and what is it principally involved in instead?
Not associated with oogenesis; rather it is principally involved in the transport of fluid and ions by surface pinocytosis
145
What does "follicle" mean in Latin?
"Little bag"
146
What are the three cell types that compose a follicle?
1. Thecal cells
2. Granulosa cells
3. Oocyte
147
What are the two functions of the follicle?
1. Endocrine gland (an active site for steroidogenesis)
| 2. Site of oogenesis
148
What is the primary steroid product of the follicle?
Estrogens
149
What is the major estrogen product of the follicle?
17-beta-estradiol
150
What two cells in the follicle cooperate to produce estrogen and how?
1. Thecal layer contains the cytoplasmic enzymes to produce androgens and very little estrogen, but these androgens are then passed on to:
2. Granulosa cells, that convert them (androgens) into estrogen.
NOTE: This cooperative relationship is called the "Two Cell Theory."
151
What are six fertility-related hormones of the anterior pituitary?
1. FSH
2. LH
3. TSH
4. Growth Hormone
5. Prolactin
6. Adrenocorticotropic Hormone
152
What are three fertility-related hormones classified as glycoproteins?
1. FSH
2. LH
3. TSH
153
What are two fertility-related hormones classified as somatotropins (growth hormones)?
1. Growth Hormone
| 2. Prolactin
154
What is one fertility-related hormone classified as a pro-opiomelanocortin?
Adrenocorticotropic Hormone
155
Define "hypophysiotropic hormone."
A hormone produced by the hypothalamus that acts no the pituitary and stimulates its rate of secretion.
156
What are eight hypophysiotropic hormones?
1. GnRH
2. Prolactin-Inhibiting Hormone
3. Prolactin-Releasing Hormone
4. Dopamine-Prolactin Releasing Factor?
5. Thyrotropin-Releasing Hormone
6. Growth Hormone-Inhibiting Hormone (Somatostatin)
7. Growth Hormone-Releasing Hormone
8. Corticotropin-Releasing Hormone
157
What does "Corpus Luteum" mean in Latin and why?
"Yellow body" b/c of the yellow pigment lutein at the LH surge
158
What is considered the second major structure of the ovary?
The corpus luteum, even though it's a structure that develops from the follicle
159
What happens to granulose cells right before the LH surge?
They begin to undergo hypertrophy and numerous lipid vacuoles start to form within their cytoplasm.
160
How does the LH surge modify the steroidogenic activity of the granulosa cell?
From an estrogen-producing cell to a progesterone plus estrogen-producing cell
161
What are four types of non-steroidogenic cells in the corpus luteum?
1. Resident leukocytes
2. Endothelial cells
3. Fibroblasts
4. Luteal cells
162
What percentage of non-steroidogenic cells make up the corpus luteum?
70-85%
163
Where in the brain is the pituitary located?
On the mental surface inside a bony pocket at the base of the skull called the sella turcica
164
Both lobes of the brain are in communication with the hypothalamus via the what?
Median eminence
165
What is the pituitary also known as and why?
The hypophysis, due to its location
166
What is the posterior pituitary composed of and what is it referred to as?
Almost exclusively of nervous tissue and is also referred to as the neurohypophysis
167
The posterior pituitary is the home of what two hormones?
Oxytocin and Vasopressin (ADH)
168
What are two reproductive-related roles of oxytocin?
1. Contraction of the uterine myometrium
| 2. Contraction of the myoepithelial cells surrounding the alveoli of the mammary gland
169
What three things do the oocyte exclusively provide for a developing embryo?
1. All the cytoplasmic material, including most of the cytoplasmic organelles
2. Nutrients
3. Embryos structural and enzymatic proteins
170
How many lobes are in the anterior pituitary, what are they called, which ones do we care about, and why?
Two lobes; anterior and intermediate; anterior; intermediate lobe is rudimentary in humans and needs not be reviewed.
171
What is the similar biological effect of oxytocin and vasopressin and why?
To stimulate specific smooth muscles; both are nano peptides with similar amino acid sequences.
172
What is the pituitary also known as?
Hypophysis
173
What are the two neurosecretory neurons in the anterior hypothalamus that produce oxytocin and vasopressin?
The supraoptic and paraventricular nuclei
174
Which part of the pituitary do the supraoptic and paraventricular nuclei products arrive and how do they get there?
In the posterior pituitary; the axons for these nuclei travel through the median eminence of the hypothalamus to form the pituitary stalk and then terminate within the posterior pituitary.
175
What terms are given for the anterior and posterior pituitary, respectively, and why?
1. Adenohypophysis - because it is composed of endocrine cells.
2. Neurohypophysis - because it is composed exclusively of nervous tissue.
176
Prior to menarche, there is an increase in activity from which part of the pituitary?
Anterior (adenohypophysis)
177
Why are the hormones of the anterior pituitary called "trophic" hormones?
Because they modulate other endocrine glands of the body
178
What three hormones do all scientists agree play a role in the reproductive system of females?
1. FSH
2. LH
3. Prolactin
179
Increased prolactin has what effect on which hypothalamic hormone?
Inhibitory effect on GnRH
180
What hormone of the anterior pituitary, although not having a documented direct role in the female reproductive system, does have effects on fertility nonetheless and why?
1. TSH - Elevated levels in female patients with hypothyroidism suggest that, if not having a regulatory role per se, still needs to be maintained in a defined range to prevent adverse actions on ovarian and endometrial function.
181
How do blood vessels enter the anterior pituitary?
Through a capillary plexus located in the median eminence of the hypothalamus (i.e. there is NO direct arterial connection to the anterior pituitary)
182
The blood vessels that lead from the plexus to the anterior pituitary are called what and to where do they lead?
The hypothalami-hypophyseal portal blood vessels; empty directly into the vascular sinusoids of the anterior pituitary.
183
What is the significance of the hypothalami-hypophyseal portal blog vessel system?
This specialized circulation allows the neuroendocrine products of the hypothalamus to be delivered directly to the anterior pituitary without being diluted into the systemic circulation.
184
In the female fetus, primordial germ cells proliferate and migrate from where to where via what? When do they reach the gonadal ridges?
From the epithelium of the yolk sac to the genital ridge via the embryonal endoderm, reaching the gonadal ridges at about the 5th week of pregnancy
185
After the fifth week of pregnancy, from where to what do the primordial germ cells travel?
Inwards from the gonadal ridges to form the primitive medullary and sex cords
186
At what do primary germ cells lose their motility and become oogonia?
After the fifth week of pregnancy, after moving inwards from the gonadal ridges to form the primitive medullary and sex cords
187
How do oogonia multiply?
Mitosis
188
What are oogonial nests?
Premeiotic gametes (oogonia) have intercellular cytoplasmic bridges between them, which is the characteristic of nest formation observed in the human.
189
How are oogonial nests thought to be derived?
From daughter cells derived from the same dividing oogonium
190
What is a possible benefit of oogonial nests?
They may help to increase the store of materials and nutrients necessary for later development.
191
How many oogonia will arrive at the fetal ovary?
1,000-2,000
192
When do oogonia stop mitosis (maximum concentration as well as weeks of gestation)?
6 to 7 million oogonia by the 20th week (5th month) of gestation
193
What eight factors have been demonstrated or suggested by researchers to play a role in fetal ovary developmemt?
1. Growth factors
2. Neurotropins
3. Prostaglandins
4. Members of the TGF-beta (transforming growth factor beta) superfamily, including:
5. BMP's (bone morphogenic proteins)
6. WNT (wingless-type mouse mammary tumor virus integration site
7. Signaling molecules
8. AMH
194
What two changes occur to some oogonia to become primary oocytes?
1. They enlarge;
| 2. They undergo nuclear changes preparing them for development into mature oocytes.
195
Is Meiosis synchronous? Why or why not?
No; a variation of meiotic progression between neighboring oocytes is evidence of this.
196
Oocytes where begin meiosis before oocytes where? What other two things do they do first?
In the inner gonad before the periphery. They also initiate follicle formation and growth first.
197
What happens after DNA replication to the homologous sets of chromosomes in a primary oocyte?
Form tetrads
198
Estimates of the proportion of oogonia that enter meiosis in the human fetal ovary vary from what to what?
50% to 90%
199
When have the earliest primordial follicles been observed in the human fetal ovary?
13 weeks of gestation
200
When do primordial follicles generally become abundant in the human fetal ovary?
16-20 weeks of gestation
201
Although regulation of primordial follicles in the human fetal ovary is not well understood, what four things have been reported to regulate nest breakdown and primordial follicle assembly?
1. Circulating hormones
2. Steroid factors
3. Locally produced factors
4. Factors involved in the apoptotic pathway
202
At what developmental stage do somatic cell-surrounded primary oocytes become primordial follicles?
After arresting in the diplotene part of meiotic prophase I
203
At what point do primary oocytes lose their intracellular bridges?
After DNA replication and formation of tetrads occur (in meiosis I)
204
What happens rapidly after primary oocytes lose their intracellular bridges?
They become encapsulated by a single layer of flattened, simple cuboidal epithelial cells (pre-granulose follicular cells), the cellular origin of which remains controversial (may be ovarian or mesonephric surface epithelial cells).
205
What does the reservoir (pool) of female gametes refer to?
The pool of primordial follicles in the fetal ovary from which all mature oocytes will develop
206
What embryonic factor regulates a female's reproductive lifespan?
The size of the reservoir of female gametes (i.e. of primordial follicles) in the fetal ovary
207
When does meiosis of the primary follicles resume after it has been arrested in the fetal ovary?
After the female reaches sexual maturity
208
The majority of follicles in the human ovary are at what stage of the germline and what is their respective diameter?
Primordial follicles; 30-50micrometers
209
Do all primary oocytes survive to form primary follicles in the fetal ovary? Why or why not?
No; some may demise altruistically to ensure that one or two from the closer (nest) can survive.
210
When do primordial follicles become known as primary follicles instead?
When their granulose cells become cuboidal.
211
When does oogenesis become intimately involved in folliculogenesis?
When the primordial follicles become primary follicles
212
How does the rate of follicular recruitment vary over a woman's lifetime?
Increases steadily during childhood and adolescence to a maximum during late teen years, followed immediately by a continuous decline
213
What happens to oogonia that do not become primordial follicles?
Degenerate in the process of atresia
214
How many primordial follicles with primary oocytes will be present at birth?
~2 million
215
What are four reasons that a portion of primary follicles are destined to become atretic due to the immaturity of the hypothalami-pituitary axis?
1. They fail to arrest in meiosis I;
2. They fail to stay arrested in meiosis I;
3. They initiate growth during prenatal life;
4. They initiate growth during pre-pubertal life.
216
The loss of primordial follicles is initiated by what?
Death of the oocyte
217
By the time puberty is reached, what has the total number of oocytes within the ovary dropped to?
300,000 to 400,000
218
What percentage of primordial follicles never mature, and what happens to these follicles?
99.9%; they degenerate and are re-absorbed by the body.
219
When does follicular atresia begin and end?
Around the 20th week of gestation; continues throughout the life of the woman until all oocytes are depleted at 45 to 55 years of age (and is the cause of menopause).
220
Ovarian aging is closely ties to what two things?
1. Decline in ovarian follicular reserve
| 2. Oocyte quality
221
What are five hypothesis which attempt to explain the maternal age effect on oocytes?
1. Oocytes entering meiosis later during fetal development might be more likely to succumb to DNA damage;
2. Oxidative damage
3. Telomere damage
4. Mitochondrial function
5. Ovarian mosaicism
222
How does a pregnant woman's internal environment affect her female progeny's subsequent oocyte integrity?
Her internal environment may influence the extent of oocyte selection and apoptosis within her fetus, directly affecting the fertility of her daughter by controlling the size of the ovarian reserve and the quality of the oocyte that will become her future grandchild.
223
What are three key regulating factors in the survival and differentiation in the germ and somatic ovarian cells?
1. Insulin
2. IGF
3. KIT-L
224
What are three known stimulators of primordial to primary follicle transition, and what hormone are they inhibited by?
1. KIT-L
2. bFGF
3. KGF
Inhibited by AMH
225
When is oogenesis endocrine independent?
From the oogonial stage until the formation of the early primary follicle
226
What estimate of fertilized human eggs have an incorrect number of chromosomes?
10-30%
227
Abnormal chromatin separation during meiosis is most often due to what?
Meiotic non-disjunction
228
Approximately what fraction of miscarriages are aneuploid?
1/3
229
What is the leading cause of developmental disabilities and mental retardation?
Aneuploidy
230
What does the word "menses" mean in Latin?
"month"
