Repro Session 1 Flashcards
What compromises the male internal genitalia?
Testes, epididymis, vas deferens, urethra, seminal vesicles, prostate gland and bulbourethral glands
What comprises the female internal genitalia?
Ovaries, Fallopian tubes, uterus, cervix and vagina
What comprises the male external genitalia?
Penis and scrotum
What comprises the female external genitalia?
Vagina, vestibule, labia minora and majora and clitoris
What are the male secondary sexual characteristics?
Larger body size, body composition and fat distribution, facial hair, male pattern baldness, CNS effects and smell
What are the female secondary sexual characteristics?
Smaller body size, SC fat distribution, breast and hair development, CNS effect
How does the development of both male and female reproductive tracts broadly start?
At an indifferent stage with a gonad and duct system
When do structural and functional development of the reproductive tracts occur?
Structural in utero
Functional after birth in childhood, adolescence and puberty
What is the urogenital ridge?
Region of intermediate mesoderm that gives rise to the embryonic kidney and indifferent gonad
Where do the cells of the primitive gonad originate from?
Stroma/parenchyma from intermediate mesoderm supported by primordial germ cells from yolk sac
How do primordial germ cells end up in the indifferent gonad?
Arise in yolk sac in week 3 and migrate into the retroperitoneum along the dorsal mesentery
Why are retroperitoneal germ cell tumours seen in the gonads?
Indifferent gonads develop in the retroperitoneum
How is the indifferent gonad developed in the genetic male?
Male gamete carries Y chromosome –> XY conceptus –> primordial germ cells carry Y –> expression of SRY genes on Y leads to male transcription factors
How does the indifferent gonad develop in the genetic female?
Male gamete carrying X chromosome –> XX conceptus –> no SRY gene zone and therefore development of female
How does the medullary cord differ in the male and female?
Develops in male, regresses in female
How do the cortical cords differ in the male and female?
No cortical cords in male, they develop in the female
Why does the ovary not have a tunica albuginea?
Oocytes have to migrate outside gonad
What does the fate of the mesonephric and paramesonephric ducts depend on?
Whether there is an ovary or testis present
Where do the mesonephric and paramesonephric ducts end?
Cloaca
What is the alternative name for the mesonephric duct?
Wolffian duct
What combines with the mesonephric duct to form the embryonic kidney to give a primitive renal function?
Mesonephric tubules
Where is the mesonephric duct positioned?
Close to the primitive gonad and making contact with the cloaca caudally
What prevents regression of the Wolffian duct?
Male sex hormones from Leydig cells
What is the paramesonephric/Mullerian duct?
Invaginations of the urogenital ridge that enlarge and pull peritoneum into the midline to form the uterus
What allows development of the paramesonephric duct?
Absence of Mullerian inhibiting substance form Sertoli cells
Where do the paramesonephric ducts have openings?
Caudally at the cloaca and cranial into the abdominal cavity
Why can the paramesonephric duct open into the abdominal cavity?
Lack draining function
How do the external genitalia appear at 7 weeks?
Indifferent: genital tubercle, genital folds surrounding opening of urogenital sinus and genital swellings
What is the result of presence of dihydrotestosterone on external genitalia?
Genital tubercle elongation, fusion of genital folds on ventral surface, fusion of genital swellings
What does fusion of the genital folds and swellings form respectively?
Spongy urethra and scrotum
What is the result of lack of testis derived androgen on the external genitalia?
Genial tubercle doesn’t elongate, genital folds do not fuse, genital swellings do not fuse and the urethra opens into the vestibule
What are the fates of the components of the indifferent gonad in the absence of testis derived androgens?
Genital tubercle –> clitoris
Genital folds –> labia minora
Genital swellings –> labia majorum
Describe the descent of the testis.
Appear retroperiotneally high up on posterior abdominal wall
–> processus vaginalis creates path for testes to be guided by the gubernaculum anterior to the pubic symphysis
What is the processus vaginalis?
Outpouching of peritoneum
What is the round ligament of the uterus?
Adult remnant of gubernaculum that attaches the ovary inferiorly to the labio-scrotal folds
Why is the round ligament of the uterus seen in the inguinal canal?
Tethered to labio-scrotal folds
Why does the ovary not move any more inferiorly that the pelvis?
It is tethered by ligaments
What does gestation depend on?
Placental support within female reproductive tract
What are hermaphrodites?
Individuals that have both ovarian and testicular tissue
If a hermaphrodite has the genotype 46, XX what do they usually have?
Uterus
Are hermaphrodites typically male or female in terms of genital development?
Either
Describe the hormone derangement in congenital adrenal hyperplasia.
Low steroid hormone production by the adrenals and hence high ACTH production
Which two processes can be affected in congenital adrenal hyperplasia?
21-hydroxylation or more rarely 17-alpha-hydroxylation
How might females affected by congenital adrenal hyperplasia present?
Parietal masculinisation with large clitoris, virilisation with male appearance, female internal and external genitalia but failure of secondary sexual characteristics
What is inhibited in males affected by congenital adrenal hyperplasia?
Virilisation
What happens in androgen insensitivity syndrome?
Males that have a Y chromosome and testis but lack of receptors to/response to dihydrotestosterone –> no male genitalia but paramesonephric duct is suppressed
How may an individual affected by complete androgen insensitivity syndrome present?
Short/poorly developed vagina, testes in inguinal or labial regions but no spermatogenesis
What does complete androgen insensitivity syndrome increase the risk of?
Testicular tumours
Describe the spectrum of effects seen in mild/partial androgen insensitivity syndromes.
Mild–> virilisation
Partial –> ambiguous genitalia
Tested are usually undescended
What happens in 5-alpha-reductase deficiency?
Testosterone is not converted to dihydrotestosterone therefore causing ambiguous genitalia in males with hypospadias/clitoromegaly
Describe Klinefelter syndrome.
47, XXY causing decreased fertility, small testes, decreed testosterone +/- gynaecomastia
Describe Swyer syndrome (XY female gonadal dysgenesis).
Point mutations/deletion of SRY gene so pts appear to be female but do not menstruate or develop secondary sexual characteristics
Describe Turner syndrome.
45, X with gonadal dysgenesis, short stature, high-arched palate, webbed neck, shield-like chest, cardiac and renal abnormalities and inverted nipples
What are the features of gonadal dysgenesis?
Oocytes absent, ovaries are streak gonads, phenotypically female with a variety of chromosomal complements
What are hypospadias?
Incomplete fusion of the urethral folds allowing abnormal openings of the urethra along the inferior aspect of the penis
Where are the abnormal openings in hypospadia usually seen?
Near the glans, shaft or base
What is epispadia?
Urethral meatus is on the dorsum of the penis
What causes micropenis?
Insufficient androgens due to primary hypogonadism, hypothalamic or pituitary disorder
What is the result of the genital tubercle splitting in the male?
Bifid penis
How do duplications of the uterus arise?
Lack of fusion of the paramesonephric ducts in a local area or along the entire line of fusion
What is uterus didelphys?
Double uterus
What is uterus arcuatus?
Slightly indented uterus due to failure of paramesonephric duct fusion
Describe uterus bicornis.
2 horns enter common vagina
What causes cervical/vaginal atresia?
Complete or partial atresia of the paramesonephric ducts
Once germ cells have colonised the gonads, what processes do they undergo to form mature gametes?
Mitosis, meiosis and cytodifferentiation
Compare spermatogenesis with oogenesis.
Spermatogenesis: huge number of gametes produced continuously with essentially disposable cells.
Oogenesis: few gametes produced intermittently with each having ~1/400th of the total reproductive potential of the female
Briefly describe the 4 steps of meiosis.
Prophase: chromosomes condense, crossing over occurs
Metaphase: homologous pairs align
Anaphase: pairs separate
Telophase: 2 daughter cells formed
What are the two main functions of meiosis in gametogenesis?
Reduce hormosome number to 23 and ensure each gamete is genetically unique
What are the products of meiosis in oogenesis?
1 mature oocyte and 3 polar bodies
Why are polar bodies formed in oogenesis?
To maximise cytoplasm and nutrients present into one cell
What is crossing over in meiosis?
Exchange of regions of DNA between 2 homologous chromosomes
What is random segregation in meiosis?
Random distribution of chromosomes among 4 gametes
How does independent assortment give rise to genetic variation?
2 homologous chromosomes of a pair must go into separate gametes
What is the raw material for spermatogenesis?
Soermatogonia
When does spermatogenesis occur in the male?
Begins around puberty and is available for up to 70 years
What are the products of spermatogonia undergoing mitosis?
Ad spermatogonium and Ap spermatogonium
What is the function of ad spermatogonium?
To maintain stock
What is an alternative name for Ap spermatogonium?
Primary spermatocytes
What happens to primary spermatocytes to give spermatids?
Divide by meiosis to give secondary spermatocytes and then to spermatids
What happens to the 4 haploid spermatids from each primary spermatocyte?
Differentiate by spermigenesis (cytodifferentiation) into spermatozoa
Where does spermatogenesis take place?
Seminiferous tubules of the testis
What splits the testis into the basal and adluminal compartments?
Tight junctions between Sertoli cells (blood testis/Sertoli cell barrier)
What is the purpose of the blood testis/Sertoli cell barrier?
Separate hormones needed for maturation and surface markers on gametes that could stimulate an immune response (as they are not self)
What is the function of the rete testis?
Concentrate sperm
What is the function of the head of epididymis in spermatogenesis?
Final maturation and storage for 2-3 months
Describe the pathway of sperm in the testes.
Seminiferous tubules –> rete testis –> ductili efferentes –> head of epididymis
What is the spermatogenic cycle?
Time taken for reappearance of the same stage of spermatogenesis within a given segment of seminiferous tubule
What is the spermatogenic wave?
Distance between the same stage of spermatogenesis in a seminiferous tubule
What causes the spermatogenic wave?
Each stage of spermatogenesis follows in an orderly sequence along the length of the seminiferous tubule
What is spermiation?
Spermatids moving into the lumen of seminiferous tubules
What happens to spermatids as they travel through the testis?
Remodelled
How are spermatids transported?
Sertoli cell secretions and peristaltic contraction up until epididymis where they become motile
Where is the energy for spermigenesis mainly derived from?
Fructose
What are the origins of the different components of semen?
Seminal vesicle secretions (~70%)
Secretions of prostate (~25%)
Sperm via vas deferens (2-5%)
Bulbourethral/Cowper gland secretions (
What is found in seminal vesicle secretions?
A.a., citrate, fructose and prostaglandins
What is found in secretions of the prostate in semen?
Proteolytic enzymes and zinc
How many sperm are released from the vas deferens per ejaculate?
~200-500 million
What is the function of mucoproteins found in bulbourethral/Cowper gland secretions?
Help lubricate and neutralise acidic urine in the distal urethra
What is sperm capacitation?
Conditions of femal genital tract allowing sperm to become fertile
What occurs in sperm capacitation?
Removal of glycoproteins and cholesterol, activation of sperm signalling pathways and acrosome reaction on binding with zona pellucid a
What is used in the sperm signalling pathway?
Atypical soluble adenylyl cyclase and PKA
What happens when the first sperm binds to the zona pellucida?
Initiation of calcium wave to prevent polyspermy
What must sperm be incubated in for human IVF?
Capacitation media
When has the female developed her entire stock of gamete potentials?
Before birth
What do germ cells differentiate into once they have colonised the primitive gonad in the female?
Oogonia
Where are the oogonia found?
Near the surface epithelium of the ovary
How do oogonia become primary oocytes?
Enter meiosis and arrest in prophase I
What happens to the majority of oogonia in the developing ovary?
Proliferate by mitosis to be arranged in clusters surrounded by flat epithelial cells
What happens in the female ovary at mid-gestation?
Maximum number of germ cells has been reached and many oogonia and primary oocytes undergo atresia
What has happened by the 7th month of gestation in the ovary?
Majority of oogonia have degenerated, ~2 million primary oocytes have entered meiosis I and are individually surrounded by flat epithelial cells to from primordial follicles
What happens to primordial follicles in the ovary?
Remain arrested (diplotene stage) until puberty
How many oocytes usually pass through the3 stages of maturation before only 1 or 2 are released by ovulation?
15-20
What are the 3 stages of oocyte maturation?
Pre-antral, Antral stage and preovulatory stage
What happens during the preantral stage of oocyte maturation?
Primordial follicles begin to grow, follicular cells become cuboidal and proliferate, stratified epithelium of granulosa cells is formed and the granulosa cells secrete the zona pellucida onto the oocyte
What happens during the Antral stage of oocyte maturation?
Fluid filled spaces appear between granulosa cells and coalesce to form the antrum, granulosa cells surrounding the oocyte (cumulus oophorus) nurse ovum
How many follicles begin to develop with each ovarian cycle?
Several
Which cells in the developing follicle express LH receptors?
Theca interna and granulosa
What causes the preovulatory stage of oocyte maturation?
LH surge
What happens in the preovulatory stage of oocyte maturation?
Meiosis I is completed, cell enters meiosis II but arrests in metaphase ~3 hours before ovulation and will only be completed if the oocyte is fertilised, otherwise it degenerates 24 hrs after ovulation
What forms the first and second polar bodies in the preovulatory stage of oocyte maturation?
Meiosis I and II respectively
What happens to the polar bodies formed during oogenesis?
Reabsorbed
What stimulates rapid follicular growth several days before ovulation?
FSH and LH
What is the Graafian follicle?
Mature follicle of ~2.5 cm diameter
What are the consequences of the LH surge on ovulation?
Increases collagenase activity, prostaglandins increase the LH response and cause local ovarian wall contractions
What forms the corpus luteum?
Remaining granulosa and theca interna cells after ovulation that become vascularised and luteinised
What is the action of the corpus luteum?
Secrete oestrogens and progesterone to stimulate uterine mucosa to enter secretory stage in preparation for embryo implantation
What happens to the corpus luteum if fertilisation does not occur?
Dies and is reabsorbed by the ovary after 14 days forming fibrotic scar tissue (corpus albicans) that decreases progesterone precipitating menstrual bleeding
How is oocyte transport achieved?
Fimbriae sweeping over ovary before ovulation, rhythmic contraction of uterine tube and motion of cilia in epithelial lining
How long does it take an oocyte to travel from the ovary to the uterine lumen?
3/4 days
What happened to the corpus luteum if the oocyte is fertilised?
hCG secreted by embryo prevents its degeneration allowing it to grow into the corpus luteum graviditatis that continues to secrete progesterone until the placenta takes over ~month 4
Where does the last stage of meiosis II in oogenesis occur?
Oviduct
