The Reproductive System Flashcards
1
Q
Reproductive life history
A
- Fertilisation
- Embryonic development, organogenesis, sex determination
- Birth
- Puberty
- Reproductive competence
- Senescence
2
Q
Key differences between male & female reproductive life history
A
Male characteristics:
- Continuous breeder
- Ability to fertilise relatively constant from day-to-day
- Primary gametes produced throughout life
- Andropause - decline in spermatogenesis with age (However not loss)
Female characteristics:
- Cyclic breeder (25-35 days)
- Capacity for fertilisation changes through cycle
- No new primary gametes produced after birth
- 1/2 million primary oocytes
- 500 ovulations
- Menopause - Reproductive cycle ceases
3
Q
Hormonal control of reproduction
A
Gonadotropin-Releasing Hormone
Stimulates release of “gonadotropins”
- Follicle-Stimulating Hormone
- Luteinising Hormone
4
Q
Peptide reproductive hormones
A
Peptide hormones:
- Chains of amino acids
- Soluble in plasma
- GnRH/inhibin B/activin
5
Q
Steroid reproductive hormones
A
Steroid hormones:
- Cholesterol-based
- Insoluble in plasma
- Need binding proteins (SHBG or ABP)
- Testosterone/DHT/estrogen/progesterone
6
Q
What are the 2 possible fates of spermatogonium (germ cell)?
A
2 possible fates:
1. Continued mitosis
- Source of new spermatogonia
- Mitosis occurs in embryo, then after puberty for rest of life
2. Meiosis
- Formation of spermatocytes
- Meiosis begins at puberty and continues for life
7
Q
Stages involved in meiosis (during gametogenesis)
A
spermatogonia → 1* spermatocytes
chromosome replicates, no cell division
(spermatocytogenesis)
1st meiotic division:
1* spermatocyte → 2* spermatocyte
2nd meiotic division:
2* spermatocyte → spermatids
single 1* spermatocyte ➔ 4 spermatids
spermatids → sperm (spermiogenesis)
8
Q
Internal vs external genitalia
A
• Internal genitalia – accessory glands and ducts
• External genitalia – penis → erectile organ for delivery of sperm & scrotum → sac containing testes (site of sperm production) – optimal ~3oC below abdominal temp
NOTION 1.1/ 1.2
9
Q
Structure of the testes
A
NOTION 1.3
10
Q
What are the 2 cell types inside the tubule of the testes?
A
2 cell types in tubule:
•Spermatogonium (form stacks)
→progressively develop from basal lamina toward lumen
•Sertoli cells (in between stacks)
→adjacently linked by tight junction
11
Q
What cell type is found outside the basal lamina?
A
3rd cell type outside BL
•Leydig cells (testosterone)
NOTION 1.4
12
Q
What is the blood-testis barrier formed by?
A
The blood-testis barrier is formed by adherent basal lamina and Sertoli cell tight junctions.
13
Q
What is the function of the blood-testis barrier?
A
• Maintains internal testicular environment (optimal for sperm)
• Prevents loss of androgen-binding protein (ABP)
• Protects from blood-borne toxins
• Prevents leakage of immature sperm into blood → immune response
14
Q
Stages involved in sperm production
A
- Mitotic spermatogonium
• Divide => New spermatogonia - Meiotic division
• Migration toward lumen
• Tight junctions break & reform as cells migrate
• Maintains BT barrier
• Become spermatids - Spermiogenesis
• Spermatids embedded in apical membrane
• Transformation into spermatozoa
15
Q
Structure of sperm
A
• Spermatid cytoplasm condenses
• Develops flagellated tail rich in microtubules
• Acrosome (flattened out lysomelike vesicle) caps nucleus
• Nuclear chromatin condenses
• Very rich in mitochondria → energy for movement
NOTION 1.5
16
Q
The sperm are non motile when released into the lumen. What then happens?
A
• Released into lumen → non-motile and immature
• Maturation continues in epididymis
• Final maturation occurs in female tract → head becomes more fusible (capacitation → stimulated by enzymes/secretions of female tract)
17
Q
Sperm statistics
- Days taken between spermatogonium -> sperm release
- Days taken for maturation and movement through epididymis
- Sperm produced/ day
- Amount/ ejaculation
A
• Around 65 days from spermatogonium -> sperm release from Sertoli cells
• further 12-20 days for maturation and movement through epididymis
• different regions of the tubule have sperm at different stages of development
• 200-400 produced million/day ~ same amount/ejaculation (2-5 ml)
18
Q
Function of Sertoli cells
What proteins do these cells release?
What are the functions of these proteins
A
• Provide nourishment for developing spermatogonia
• Manufacture and secrete an array of spermatogenic proteins:
- inhibin B – inhibits FSH secretion from anterior pituitary
- activin – stimulates FSH and GnRH release
- androgen binding protein (ABP) → binds testosterone - increases solubility and concentrates it in the luminal fluid
19
Q
Function of leydig cells
A
Leydig cells
• In interstitial space around tubules & secrete testosterone
• Active in foetus - activity resumes at puberty
20
Q
Endocrine control of speramtogenesis
A
NOTION 1.6
21
Q
Effects of testosterone
A
Testosterone – peripheral (secondary) effects
• 1 – differentiation, growth and development of internal/external genitalia
• In combination with a 2nd class of androgen (testosterone - (5-reductase) -> dihydrotestosterone)
• 2 - responsible for production and maintenance of secondary sexual characteristics: → body shape, beard, body hair growth/patterning, muscle mass, thickening of vocal chords, libido
22
Q
What is more potent: testosterone or dihydrotestosterone?
A
Dihydrotestosterone
23
Q
Accessory glands of male tract
What is their main function?
What % of seminal fluid comes from each of the glands?
A
Accessory glands = seminal vesicles, prostate & bulbourethral glands
Contribute fluid secretions to sperm → semen
99% of volume added from accessory glands:
- Seminal vesicles = 60%
- Bulbourethral gland = 5%
- Prostate = 30 %
24
Q
Composition of semen, and the related function of each of these components. As well as the source.
A
NOTION 1.7
25
Functions of semen
Functions:
- Sperm support/nourishment
- Aids sperm motility
- Facilitates retention/transit through the female tract
- pH buffering
- Lubrication
- Protection from pathogens
26
2 components of male sex act
1. Erection reflex
2. Climax
27
What is involved in the erection reflex?
Erection reflex: Normally flaccid penis must stiffen to facilitate vaginal penetration
28
What stimulates the erection reflex?
Controlled by both mechanical stimulation & higher brain centres:
Mechanoreceptors in:
- penis (glans)
- erogenous zones (ear lobes, lips, nipples, neck)
Other sensory modalities:
- Sight, sound, taste, smell
Also centres involving:
- Memory/thought processes
29
What NS controls the erection reflex?
What does it stimulate?
- Controlled by parasympathetic nervous system
- Stimulate release of nitric oxide (NO) from arteriolar endothelial cells
30
Neural control of the erection
Ascending sensory pathways & inputs from other brain areas:
→ stimulate descending autonomic pathways
→ parasympathetic
→ NO released from endothelial cells of penile arterioles
→ penile arterioles dilate
→ erectile tissues fill with blood; restricts venous outflow
→ vasocongestion
→ engorged, hardened penis
31
What is involved in the climax?
Emission & ejaculation
32
What is involved in the emission stage?
Emission:
- Sperm moves from vas deferens → urethra
- Mixes with accessory gland secretions → semen 2-5 ml
33
What is involved in the ejaculation stage?
Ejaculation:
- Semen in urethra propelled to exterior
- Driven by rapid and rhythmic contractions of smooth muscle
- Accompanied by intense pleasure (orgasm)
- Sphinctor at base of bladder closes off urinary part of urethra
34
What is the female germ cell?
Germ cell = oogonium
35
Where does mitosis of gametes occur in females?
Mitosis only occurs in embryo
36
When do oogonia undergo 1st stage of meiosis?
What is involved?
Oogonia undergo 1st stage of meiosis by 5th month gestation:
→ chromosomal replication without cell division
→ produces 1* oocytes
37
What happens after the 1st stage of meiosis in female gametes?
It arrests at this stage of meiosis, with no further oocytes being formed beyond birth.
38
What is a characteristic of gamete formation in females?
Females are born with full complement of primary gametes.
Around 500,000 in total (at puberty).
39
What are 1* oocytes protected by?
What happens during each cycle?
1* oocytes
• Protected and nurtured within follicle
• Single 1* oocyte per follicle
• Several follicles develop/mature per cycle after puberty
• Only one is selected and fully matures → dominant follicle
40
What happens during ovulation, what triggers this?
• Oocyte released from this follicle during ovulation
• Only the oocyte within the dominant follicle resumes meiosis
• Triggered by LH surge
41
What happens in the 1st true meiotic division?
1st true meiotic division
• Only occurs in 1* oocyte within selected follicle
• 1* oocyte -> 2* oocyte & 1st polar body
• Disparate sizes
• Polar body disintegrates
• Egg begins 2nd meiotic division
• BUT pauses (again) after sister chromatids separate (still in follicle)
42
What happens to the 2* oocyte?
What then happens, if fertilisation does or does not occur?
• Egg (2* oocyte) released from ovary with meiosis still suspended (ovulation)
• If no fertilisation occurs → meiosis never completed and egg lost
• If fertilisation occurs → egg completes division
• Fertilised egg -> 1/2 sister chromatids form zygote with sperm nucleus & 1/2 sister chromatids form 2nd polar body
• Hence 1 primary occulted produces single egg
43
Following characteristics of gametogenesis in males vs females:
- Site
- Germ cell
- Mitosis
- Meiosis
- Meiosis completed?
- Gametes produced
- Numbers
NOTION 2.1
44
Anatomy of the Female Reproductive System
NOTION 2.2/ 2.3
45
What does the female external vs internal genitalia consist of?
Female external genitalia = vulva or pudendum
Female internal genitalia = vagina, cervix, uterus, fallopian tubes and ovaries
46
What is the cervix?
What is it lined with?
What does it create?
• Narrow “neck” of uterus
• Lined with mucous-secreting glands
• Creates physical & chemical barrier between vagina and uterus
47
What is the uterus?
What are the 3 layers of the uterus?
Thickness of the endometrium
The Uterus (site of implantation for fertilised eggs)
• 3 layers
– Outer connective tissue (support, rich blood supply)
– Smooth muscle layer (myometrium) – child birth
– Inner epithelium (endometrium) – rich in blood vessels/glands
• Endometrial thickness/character changes during menstrual cycle
48
How long are the fallopian tubes?
Diameter of the fallopian tubes
Smooth muscle in the fallopian tubes
Epithelium of the fallopian tubes
Fallopian tubes
• 20-25 cm long
• Diameter of drinking straw
• Longitudinal & circular smooth muscle in walls
• Fluid-filled
• Lined by cilliated epithelium
49
What is the function of cilia in the fallopian tubes?
What is the site of fertilisation?
What are the fimbriae?
• Cillia beating/muscular contraction moves fluid and egg toward uterus
• Site of fertilisation if descending egg meets ascending sperm
• Open end of tube divided into finger-like projections → fimbriae
• These “sweep” egg into tube rather than losing it into abdominal cavity
50
Shape of the ovaries
Diameter of the ovaries
What are the 2 sections of the stroma?
What does the cortex contain?
Why are the ovaries important?
The Ovaries
• Elliptical shape (2-4 cm diameter)
• Medulla – rich in blood vessels
• Rest of stroma = cortex
• Cortex = site of follicular dev.
• Contains follicles at various stages of development/decline
The ovaries are vitally important as the site of gametogenesis and also as a source of hormones.
NOTION 2.4
51
What is involved in folliculogenesis?
- How long does it take?
- How many follicles are developed in each cycle?
- How many become dominant follicles?
- What happens to the rest?
• Takes months to move between stages
• Each cycle ~ 20 follicles develop to tertiary stage in each ovary
• Only 1 actually becomes mature, dominant follicle (mechanism unclear)
• The rest undergo atresia (regression) and are lost
NOTION 2.5
52
What is the thecal layer of a follicle composed of?
Thecal layer composed of interna (glandular) and externa (blood vessels and smooth muscle) in mature follicles.
53
What is the effect of the LH surge?
Purpose/Effect of LH surge:
- Stimulates resumption of meiosis in 1* oocyte (pauses again during 2nd meiotic division)
- Stimulates enzymes to digest outer layers of follicle
- Stimulates prostaglandin (contraction of follicle smooth muscle) → ruptures follicle releasing 2* oocyte
54
What are the different stages of a follicle?
1. Primary follicle = Primordial follicle (50 um)
2. Secondary follicle = Preantral follicle (200 um)
3. Tertiary follicle = Antral follicle (5 mm)
4. Pre-ovulatory follicle = Graffian follicle (20 mm)
55
How long can folliculogenesis take?
Folliculogenesis takes up to 375 days in total, but begins continuously
→ Follicles of different stages within ovary at any 1 time
→ Normally always 1 mature enough for ovulation
56
What is the length of menstrual cycle?
Ranges from 24-35 days
57
What is the menstrual cycle characterised by?
What are the two subsections of the menstrual cycle?
Characterised by 3-7 days of menstruation (menses) when
uterine lining is shed as bloody discharge through the vagina.
The menstrual cycle can be split into:
- Ovarian cycle (changes occurring in the follicles of the ovary)
- Uterine cycle (changes occurring in the endometrium of the uterus)
58
What are the stages involved in the ovarian cycle?
Ovarian cycle:
- Follicular – follicle develops
- Ovulation – egg released
- Luteal – ruptured follicle forms corpus luteum
59
What are the stages involved in the uterine cycle?
Uterine cycle:
- Menses – lining shed
- Proliferative – lining thickens & develops
- Secretory – thickened endometrium becomes secretory
60
Graph displaying the levels of gonadotrophic & ovarian hormones, in combination with the ovarian cycle, and uterine cycle.
NOTION 2.6
61
Hormonal overview of the Ovarian Cycle
NOTION 2.7
62
With regard to the early-mid follicular phase:
- What does FSH stimulate?
- What does LH stimulate?
- What does Estrogen drive?
- What is the effect of elevated Estrogen levels?
Early-mid follicular phase
- FSH stimulates estrogen release from granulosa cells (GCs)
- LH → androgen release (androstenedione) from thecal cells converted to estrogen in GCs
- Estrogen drives its own production from GCs
- Elevated estrogen begins to reduce FSH/LH production
→ reduces further follicular development (enough follicles committed)
63
With regard to the LH Surge:
- What do high Estrogen levels induce?
- Feedback given from Estrogen & Progesterone
- What is the effect of these two factors?
- What happens to the effects of FSH?
- What is stimulated following the LH surge?
LH Surge
- Increased GnRH receptor expression induced by high estrogen levels → Ant. pituitary ultra-sensitive to GnRH
- Estrogen/progesterone also switch from –ve feedback to +ve feedback at level of hypoth. and anterior pituitary
- Together produces a very profound surge in GnRH potency ➔ LH surge
- FSH less pronounced as it is cushioned by inhibin
- Stimulates ovulation ~ 24 h later
64
With regard to the early-mid luteal phase:
- What does the corpus luteum produce?
- What is the effects of these hormones?
- What does this help to maintain?
Early-mid luteal phase
- Corpus luteum produces progesterone, estrogen and inhibin
- Inhibits hypothalamus and pituitary (-ve feedback again)
→ inhibits folliculogenesis
- Supports and maintains endometrium
65
With regard to the late luteal phase:
- What happens to the corpus luteum?
- What happens to Estrogen/ Progesterone levels?
- What is the effect of this on the hypothalamus/pituitary?
Late luteal phase
- Corpus luteum regresses & dies after 12-14 days
- Estrogen/progesterone levels decrease
→ endometrium shed (menses)
- Relieves inhibition of hypothalamus/pituitary
→ FSH and LH secretion reinstated
- Follicular development continues into new cycle
66
With regard to the menses phase of the uterine cycle:
- What days does this phase take place in?
- What happens to the endometrium?
- How much cellular debris/ blood is lost over this period?
- What is this phase stimulated by?
- What phase of the ovarian cycle coincides with this phase?
Day 1-6 = menses:
- Endometrium sloughs its surface layer
- 35 ml serous fluid/ cellular debris & 40 ml blood is discharged over 3-7 days
- Stimulated by loss of hormonal support from corpus luteum
- Continues well into the follicular phase of the ovarian cycle
67
With regard to the proliferative phase of the uterine cycle:
- When does this phase take place?
- Where does Estrogen come from?
- What is the effect of Estrogen?
- What is the final thickness?
- What happens to the cervical mucous?
- What does this help?
Day 7-14 = proliferative phase:
- Estrogen comes from developing follicle
- Estrogen stimulates proliferation, vascularisation & gland formation
- Final thickness = 3-4mm
- Cervical mucous - stringy approaching ovulation
- Helps “catch” sperm and moves them through cervix
68
With regard to the secretory phase of the uterine cycle:
- When does this take place?
- What is the effect of estrogen and progesterone during this phase?
- What happens to the endometrial cells?
- What happens to the cervical mucous?
- What happens to progesterone levels during this phase?
Day 14-28 = Secretory Phase:
- Estrogen stimulates proliferation, vascularisation & gland formation. Progesterone = primary supportive hormone (secretion of supportive mucous)
- Endometrial cells become enriched with glycogen/ lipids (embryonic nourishment)
- Cervical mucous - thickens and forms protective plug
- Progesterone declines as corpus luteum regresses (12-14 days)
69
What secondary sex characteristics does Estrogen have an effect on?
Secondary sex characteristics:
- Breast development
- Fat distribution (hips/ thighs)
- Maintenance of vaginal function
- Mucosal Structure
- Lubrication
70
What others effects does estrogen have on the body?
Other effects:
- Bone structure/ density
- Cardiovascular health
71
What is the effect of testosterone & other androgens (from the ovaries/ adrenal glands) on sex characteristics?
Other sex characteristics:
- Pubic/ axillary hair
- Libido
72
What is the concentration of testosterone in males vs females?
Males = 9-35 nmol/ litre
Females = 0.2-2.5 nmol/ litre
73
What is involved in the female sexual response?
It is triggered by the same combination of mechanical (and other sensory) stimuli and higher center influences as male.
However it is much more complex. It is characterised by:
- Erection of clitoris
- Identical control to male erection (NO)
- Vasocongestion in erectile tissue space
- Dilation of labia/ vagina
- Increased blood flow to pubic region
- Increased sensitivity
- Lubrication of vagina
- Bartholins gland (female eq. to Bulbourethral gland)
- Plasma seepage from vaginal walls
74
Climax involved in female sexual response
Climax of female sexual response:
- Series of muscular contractions (vaginal walls & uterus)
- Pleasurable sensations (orgasm)
- Autonomic response (heart/ respiratory rate, blood pressure)
Unlike male climax, the female climax is not required for pregnancy however, there is suggestion that it can facilitate fertilisation:
- Contractions help sperm transit towards uterus
- Mucous secretions etc nurture sperm in female tract
75
How many autosomes does a human have?
What do these direct?
What do the sex chromosomes direct?
Autosomes – 22 homologous pairs
Direct human somatic development
sex chromosomes – X or Y
direct human sexual development
inherit 1 from each parent
76
Presence and absence of Y chromosome
Presence of Y ➔ embryo becomes male (even if XXY)
Absence of Y ➔ embryo becomes female (XO viable)
YO non-viable
→ presence of an X also fundamentally required
→ larger chromosome - encodes vital genes
77
What happens in females, 2 weeks after fertilisation?
In females: ~ 2 weeks after fertilisation
→ 1 of X chromosome pair inactivates
→ Condenses to form Barr body (condensed clump of chromatin)
→ Barr body identifiable in female cells
78
How many sperm are ejaculated during copulation?
How many make it to the site of fertilisation?
Copulation results in ejaculation of ~200 million sperm into the vagina.
Of total no. ejaculated only ~100 sperm make it to the fertilisation site.
79
What is involved in ovulation?
Ovulation
- Released egg moves down fallopian tube
- May release molecules that attract sperm
- Egg can only be fertilised for ~ 24 h after ovulation
80
What is involved in capacitation?
Capacitation
- Outer membrane changes (more readily fusible)
- Enhanced motility
- Occurs in female tract
- Sperm remains viable for 4-6 days in female tract
81
What do sperm need to penetrate cells surrounding an egg?
Where are these released?
Sperm need enzymes to penetrate cells surrounding egg
→ Released from the acrosome of capacitated sperm
→ Sperm binds to sperm-binding receptors on oocyte membrane
→ 1st sperm to reach receptor fuses membranes with egg
82
What happens following fertilisation?
1. Completion of 2nd meiotic division in the egg
- Fusion of egg/sperm membranes triggers:
→ sperm nuclei passage into egg cytoplasm
→ resumption of meiotic division
→ ejection of 2nd polar body
2. Block to polyspermy (prevents more than 1 sperm fertilising egg)
→ Cortical granules degranulate in response to sperm fusion
→ They secrete contents into space outside egg membrane
→ This changes the nature of zona pellucida and egg membrane
→ The egg membrane is now impermeable to sperm
→ Known as the cortical reaction
3. Cell division begins in the zygote
→ Division begins during transit through tube - resulting in increased cell numbers
83
What is the most common site for fertilisation?
The ampulla
84
Movement of fertilised egg through fallopian tube
NOTION 3.1
85
Pre implantation cell division
NOTION 3.2
86
What is the blastocyst?
The Blastocyst
- hollow ball of ~ 100 cells
- forms around day 5 after fertilisation
87
What does the inner cell mass form?
Inner cell mass forms:
- Embryo
- Some extra-embryonic membranes
i) amnion – secretes amniotic fluid
ii) allantois – part of umbilical cord
iii) yolk sac – degenerates early
88
What does the outer cell mass form?
Outer cell mass (trophoblast) forms:
- Chorion – another extra-embryonic membrane
→ encloses embryo and forms placenta
89
What is the blastocele?
Blastocele: fluid-filled cavity (amniotic fluid)
90
What is involved in implantation?
Implantation (~7 days post fertilisation)
- Blastocyst secretes enzymes → “burrows” into endometrium
- Endometrial cells surround blastocyst, which becomes engulfed
- Division continues; blastocyst → embryo
- Termed an embryo from implantation → 8th week of gestation → foetus
91
Where do the chorionic villi grow into?
What is the effect of this?
• Chorionic villi grow into endometrium (highly vascularised)
• Release enzymes that breakdown maternal blood vessel walls → villi bathed in maternal blood
• Ideal exchange bed for gasses, nutrients, waste and even maternal antibodies
• No blood mixing – placenta receives up to 10% of maternal blood flow
NOTION 3.3
92
What happens to the corpus luteum following implantation?
What is the effect of this on hormone levels?
How is this prevented?
- After implantation the corpus luteum begins to near the end of its 12-day life.
- Corpus luteum regression → decrease in progesterone/estrogen → endometrial sloughing
- Placenta produces hormones to prevent this
93
What hormone does the placenta produce?
What can this be used for?
What is the physiological effect of this hormone?
Human chorionic gonadotropin (hCG)
- Peptide hormone secreted by chorionic villi
- hCG detected in pregnancy tests
- Stimulates ongoing progesterone production from corpus lutem
94
Role of corpus luteum throughout the trimesters
• Corpus luteum supports pregnancy during early 1st trimester → regresses
• Placenta takes over secretion of progesterone and estrogen
95
Effect of estrogen throughout pregnancy
Effect of progesterone throughout pregnancy
Estrogen
- Important for embryonic/foetal development
- Also stimulates milk-ducts
Progesterone
- Maintains endometrium
- Inhibits uterine contraction
Also feedback & suppress pituitary → prevent further follicular development
96
What happens when hCG levels decline?
• hCG levels decline; estrogen/progesterone increase (entirely placental)
• further developmental roles in mother and foetus
•support also required for endometrium & preventing uterine contraction
97
When does the bipotential or indifferent stage come to an end?
What happens following this?
• Bipotential or indifferent stage continues up to week 6 of gestation
• Gonads arise from genital ridge/bipotential gonad alongside foetal kidney
98
What happens when there is no signal?
What happens when there is a signal?
No signal - cortex -> ovary
Signal - medulla -> testis
99
What are the 2 different pairs of ducts?
- Wolffian ducts
- Mullerian ducts
100
What are some bipotential external genitalia?
Bipotential external genitalia
- Genital tubercle
- Labioscrotal swelling
- Urethral folds
- Urethral groove
101
What is the signal?
The signal = sex-determining region of the Y chromosome (SRY gene)
102
Sexual differentiation in the embryo:
- What does the SRY protein activate?
- What do the protein products act on?
- What does this structure form?
- What hormones are then produced?
- What is the effect of these hormones?
NOTION 3.4
103
Sexual differentiation in the embryo:
- What happens if there is no SRY protein?
- What structure is then affected?
- What hormones are then absent?
- What is the effect of these low levels?
NOTION 3.5
104
External genitalia differentiation
Differentiation driven by presence/absence of dihydrotestosterone (DHT).
Descent of testes into scrotum driven by testosterone.
NOTION 3.6
105
Summary of Key Bipotential Structures and Their Fate During Sexual Differentiation
NOTION 3.7
106
When does parturition usually occur?
Parturition (labour and delivery) usually occurs between weeks 38-40.
107
What stimulates parturition?
Stretch of the uterine is stimulated by:
- Decreased progesterone (no longer inhibits uterine contraction)
In addition there is:
- Increased estrogen
- Increased prostaglandin
- Increased relaxin (cervix softens/pelvic ligaments loosen)
This then sends signals via afferent neurons, which stimulate the release of oxytocin.
Oxytocin then stimulates uterine contraction.
108
Posiitve feedback & parturition
- Contractions drive cervical dilation → drives +ve feedback (oxytocin)
- +ve feedback → contractions intensify & baby delivered through vagina
109
What happens to the placenta following delivery?
What helps decrease blood loss?
What is a typical blood loss?
- Placenta detaches and follows soon after
- Contractions help clamp maternal blood vessels to prevent excessive bleeding
- Typical blood loss ~ ½ pint (250-300 ml)
110
Effects of prolactin
Effects of oxytocin
Prolactin = milk production
Oxytocin = milk ejection/let down
111
What is PIH?
What is it’s effects?
What happens to PIH levels during pregnancy?
What is the effect of suckling on PIH levels?
PIH = prolactin-inhibiting hormone
→ inhibits prolactin secretion
• PIH levels fall in pregnancy
→ milk production during pregnancy
• Suckling relayed to hypothalamus
→ further reduction in PIH
➔ more milk secreted
112
What is the average weight of a baby?
Average baby – 7-8 lb
113
What is the largest recorded weight of a baby?
Largest baby:
- 23 lb 12 oz
- 1879 in Canada - only lived 11 h
114
What is the smallest recorded weight of a baby?
Smallest baby
- 8 oz
- 2004 in Illinois, USA
- Rumaisa Rahman
- Her twin Hiba was just 1lb 4oz
115
What is the most amount of children delivered by a women?
Most babies
- 69 from a Russian women (1707-1782)
- Only known as 1st wife of Feodor Vassilyev
- 27 pregancies – 16 twins, 7 triplets, 4 quadruplets
116
What are 7 different categories of reproductive diseases?
1. Genetic – multiple/absent sex chromosomes
2. Developmental – abnormal embryonic/pubertal development
3. Structural – malformed/malfunctioning reproductive tissues
4. Endocrine – disruption in hormonal control of reproduction
5. Gestational – reproductive dysfunction during pregnancy
6. Cancer – malignant invasion of reproductive tissue
7. Infertility – inability to conceive (after 1 year of unprotected intercourse)
Most reproductive disorders belong to more than 1 of these categories.
117
What are genetic reproductive diseases caused by?
Commonly caused by non-disjunction of sex chromosomes
118
What is Turners Syndrome?
How common is this condition?
What are some characteristics of this condition?
Turner’s syndrome (XO) - 1/10,000:
- Sexually infantile – no Barr bodies
- Ovaries poorly developed
- Webbed neck, broad chest, short stature, poor breast development, CV/kidney problems
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What is Kleinfelter’s Syndrome?
How common is this condition?
What are characteristics of this condition?
Kleinfelter’s syndrome (XXY) – 1/500:
- Externally male (often with breasts)
- Small, cryptorchid testes (sterile)
- Small ext genitalia (hypospadias)
- Mental retardation common
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Diagram of non disjunction in sperm
NOTION 4.1
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What is Poly-X syndrome?
How common is Poly-X syndrome?
Characteristics of Poly-X syndrome
Poly-X - 1/2,000:
- Can be fertile
- Often undiagnosed (inactivation of X chromosomes)
- Normal – abnormal sexual features
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Diagram of non disjunction in ovary
NOTION 4.2
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What is androgen insensitivity syndrome?
What is its effect on testicular tissue?
What is its effect on testosterone levels?
What happens to the androgen receptor?
What is the effect of this?
AIS/testicular feminisation:
- Normal testicular tissue (internal, undescended)
- Normal testosterone levels
- Genetic mutation in androgen receptor
→ testosterone has little effect on target tissues
→ female external genitalia/undescended testes
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What does the severity of AIS depend on?
What chromosome does the mutation lie on?
What happens in carrier females?
- Range of severity depends on exact mutation
- Sex-linked (X-chromosome)
- Carrier females → pubic/axillary hair/acne
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What is male pseudohermaphroditism?
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What is ambiguous female genitalia?
What are some characteristics of this condition?
What happens in male sufferers?
Ambiguous female genitalia (XX)
- Congenital adrenal hyperplasia
- Adrenal glands produce excess androgens
- Virilization/masculinization of female genitalia
Male sufferers acquire mature male sexual characteristics shortly after birth.
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What is female pseudohermaphroditism?
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What is true hermaphroditism?
True hermaphroditism → combination of male and female gonadal tissue on one or both sides.
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How common is Hypospadia?
What is Hypospadia?
What causes Hypospadia?
Severity of Hypospadia
How is it corrected?
Hypospadia (2nd most common genital birth defect)
- Deviation of the external urethral meatus from the tip of the glans penis
- Opens instead along ventral surface/internally
- Failure of urethral folds to fuse during development
Classed according to severity
→ determines urogenital functionality
Usually corrected by surgery in infancy
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What is normal testicular descent directed by?
What is it controlled by?
What phase of descent occurs at 7 months gestation?
What phase of descent occurs at 8 months gestation?
- Directed by gubernaculum contraction
- Controlled by testosterone
1. Transabdominal descent - 7 months gestation
2. Transinguinal descent- 8 months gestation
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What is cryptorchidism?
How common is it?
How can it be corrected?
What is the effect on spermatogenesis?
Failure of testicular descent (3% male births)
➔ cryptorchidism (1 or both testes)
- Testis remains at any point in descent path
- Corrected surgically/hormonally in infancy
- Temp. damage if spermatogenesis begins
- Potential to become cancerous
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What is endometriosis caused by?
What is it characterised by?
What are some symptoms of endometriosis?
Caused when: Stray pieces of shed endometrium move up Fallopian tube → abdomen (retrograde menstruation).
Characterised by ectopic endometrial tissue in places it shouldn’t by e.g in the ovaries.
Symptoms:
- Dysmenorrhea (painful periods)
- Pelvic/abdominal/back pain
- Pain during ovulation/intercourse
- Can cause infertility
→ scars/inflammation on ovary
→ Fallopian tube/ovarian blockage
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What % of women with endometriosis are asymptomatic?
What % of women with chronic menstrual pain are found to have endometriosis?
What % of infertile women are found to have endometriosis?
What % of women with endometriosis are infertile?
Prevalance:
- 2% of women asymptomatic
- Found in 20% of women with chronic menstrual pain
- Found in 20% of infertile women
- Up to 60% of women with endometriosis are infertile
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What is involved in treatment of endometriosis?
Treatment:
- GnRH inhibition
→ reduced FSH/LH (loss of cycling) → reduces stimulation of endometrium
→ normal lining AND ectopic patches
→ alleviation of pain….not often curative
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What is PCOS?
What is the effect of the cysts formed?
What are symptoms of PCOS?
What can PCOS be linked to?
How can PCOS be treated?
PCOS = Poly Cystic Ovarian Syndrome (multiple, persistent cysts in ovary = follicles stalled during folliculogenesis).
Cysts common and most regress spontaneously (seen in 20% of women)
Some persist and secrete steroid hormones → reproductive interference.
Symptoms
- irregular menstruation (reduced fertility)
- often see androgen-linked symptoms → acne, greasy skin, hirsutism
Links with obesity/type2 diabetes
Managed with combination of progesterone/estrogen → LH/FSH → reduces androgen production
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How are couples considered infertile?
Couples considered infertile if they have been engaged in unprotected coitus for 1 year without pregnancy.
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What % of married couples seek assistance with infertility?
Of these couples, what % were female, male caused or caused by both partners?
1/6 married couples (17%) seek assistance.
NOTION 4.3
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What is the most common causes of infertility?
Most common causes involve ovulatory failure or problems with sperm.
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What % of infertility is diagnosed?
What % experience successful treatment?
Diagnosis: 85-90%
Successful treatment: 50-60%
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Who was the 1st “test tube baby”?
Louise Joy Brown (25th July 1978) – 1st “test-tube baby”
> 1 million worldwide since.
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What is involved in in-vitro fertilisation (IVF)?
NOTION 4.4
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What % of women become pregnant per IVF cycle?
What % of transferred embryos implant/ develop?
What % results in multiple births?
~ 28% of women become pregnant per IVF cycle
<15% of transferred embryos implant/develop
~30% result in multiple births
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What are improvements made with regard to IVF treatment?
- Micro-manipulation of eggs and sperm to enhance chances of fertilisation
- Improved sperm purification/harvest direct from testes
- Selection procedures – use of best oocytes/sperm
- Better In Vitro maturation (gametes and zygote)
- Cyropreservation of eggs/sperm/embryos – use in later IVF cycles
- Donor banks for sperm and eggs
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Since 1940s, what has happened to:
- Sperm production
- Seminal volume/ quality
- Sperm motility
In many countries of the Western world (including Scotland):
- Sperm production has halved
- Seminal volume/quality reduced by 1/3
- Sperm banks also report reduced sperm motility
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Recent prevelance of Testicular dysgenesis syndrome
What do Testicular dysgenesis syndrome’s include?
Worldwide doubling in incidence of testicular dysgenesis syndrome (TDS)
→ Poor semen quality
→ Testicular cancer
→ Cryptorchidism/hypospadias
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What are EDCs?
EDCs (Endocrine Disrupting Chemicals) = Environmental chemicals which interfere with endocrine systems
NOTION 4.5
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To effect reproductive development, EDCs must be present ____________.
In Utero
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What are EDC sources?
EDC sources = industrial pollution, pesticides, transport, buildings, nature.
Persistent chemicals → atmosphere → soil/rivers/oceans → plants/animals.
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How do EDCs accumulate in the mother?
How can it then affect the new born baby?
NOTION 4.6
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Examples of EDCs, and their effects on reproductive system
NOTION 4.7
