Repro Flashcards
What makes the primitive gonad?
-Intermediate mesoderm of urogenital ridge and primordial cells
What are primordial germ cells?
-Specialised population of cells derived from the yolk sac which migrate along the dorsal mesentery and populate the mesodermal stroma of the gonads and are the ‘seed of the next generation’
How does the presence of SRY genes influence development?
-Drives development of the male causing differentiation of the gonads into testis, the duct system and the external genitalia
Describe what happens to mesonephric (wolffian) duct system in a male
- Mesonephric duct makes contact with urogenital sinus and ureteric buds begin to sprout causing development of metanephros
- The urogenital sinus expands as smooth muscle appears in the walls creating independant openings for UBs and MDs as it absorbs the structures
- Presence of androgens causes development of prostate, spongy urethra and vas deferens
Describe what happens to mesonephric (wolffian) duct system in a female
- Mesonephric duct makes contact with urogenital sinus and ureteric buds begin to sprout causing development of metanephros
- The urogenital sinus expands as smooth muscle appears in the walls creating independant openings for UBs
- Lack of adrogens leads to regression of MDs and the development of the female internal and external genitalia
Describe what happens to the paramesonephric (mullarian) ducts in females
Why is this prevented in males?
- PMDs appear as invaginations of urogenital ridge
- As they develop and elongate pulling the peritoneum with it, cranially they open into abdo cavity and caudally they fuse at the midline
- This develops to form the upper 1/3 vagina, cervix, uterus and uterine tubes by regression of the septum which was created by fusion
- Mullarian inhibiting hormone released from the testis prevents development of PDS in males
How does the external genitalia of a fetus begin? Describe how these develop into both the male and femaly external genitalia
- Genital swellings, genital tubercles and genital folds
- Males = GT elongates and GF fuse on the ventral surface. This forms spongy urethra and is influenced by DHT
- Females = lack of DHT causes GT to remain and open into a vestibule instead of elongating
Describe the testicular descent
- Begin on the posterior abdominal wall at urogenital ridge (retroperitoneal)
- Evagination of processes vaginalis derived from parietal peritoneum creates a pathway for the testis to pass through the inguinal canal and into the scrotum
Describe ovarian descent
-Start on posterior abdominal wall at urogenital ridge and are tethered to labioscrotal folds via gubernaculum. Drawn down but do not pass through inguinal canal as they are obstructed by the uterus and uterine tubes
What 3 factors during meiosis ensure genetic variation?
- Crossing over
- Random segregation
- Independent assortment
Briefly describe spermatogenesis How long does it take?
- Germ cells line the seminiferous tubules of the testis and become more differentiated towards the lumen. They are finally released as spermatids and carried to the epididymis by sertoli cell secretions and peristalsis where they become motile ad are now spermatozoa
1) Spermatogonium(2n) undergoes mitosis -> Ad (2n replenishes stock) and ap spermatogonium/1 spermocyte(2n)
2) 1spermocyte undergoes meiosis I and forms 2x 2spermatocyte (1n) 3) both 2 spermocytes undergo meiosis II and form 4xspermatid
4) spermatids released and transported to epididymis becoming spermatozoa - 74 days
What is the spermatogenic wave and cycle?
- Spermatogenic wave refers to how spermatogenesis generations spiral around each other within a seminiferous tubule as different germ cells differentiate at different times
- The spermatogenic cycle refers to the time it takes for the same stage of differentiation to appear at the same point in the wave. approxmately 16 days
What are the main constituents of sperm and where do they come from?
- Mostly seminal vesicle secretions (70%) containing a’a, citrate, PGs and fructose
- Prostate secretions (25%) containg proteolytic enzymes
- Sperm - 200-500mill
- Bulbourethral secretions to neutralise and lubricate distal urethra
What is sperm capacitation?
- The final maturation step which occurs in the female genital tract
- Glycoproteins are removed from sperm head which activates signalling pathways and allows the sperm to bind to the zona pellucida of the oocyte to initate the acrosome reaction
Describe oogenesis before birth
- Primordial germ cells in gonads differentiate into oogonia and proliferate by mitosis
- Selected oogonia enter meiosis I whilst others continue in mitosis
- Those which enter meiosis I are primary oocytes and arrest in prophase I and become individually surrounded by follicular cells forming a primordial follicle
- By mid-gestation max number of oogonia are reached and selection occurs. Majority of oogonia undergo atresia
- All surviving oogonia enter meiosis I and halt in prophase I and become primordial follicles
Describe oogenesis when puberty begins, includint the different stages of maturation
- Degeneration of primordial follicles has been occurring since birth
- At puberty approx 15-20 primordial follicles begin to mature passing through preantral, antral and preovulatory stages of maturation. Out of this 20 only 1 will make it to ovulation due to ongoing atresia
- Preantral = primordial follicle grows and granulosa cells form and begin secreting zona pellucida
- Antral = fluid filled spaces appear between granulosa cells and eventually coalesce to form an antrum. Theca interna/externa develop and this is now secondary follice
- Preovulatory = Under influence of FSH and LH meiosis I is completed to produce 2 haploid cells of unequal size. Meiosis II begins but arrests before ovulation and is only completed upon fertilisation. The secondary follicle is now called the graafian follicle.
What induces ovulation and how?
-LH surge causes an increase in collagenase activity inside the ovary-> matrix breakdown in graafian follicle and extrusion of oocyte by PG-induced muscular contraction
What is the corpus luteum? What is its function? What happens to it?
- The granulosa and theca interna of the graafian follicle become vascularised under the influence of LH and begin to secrete progesterone and oestrogen
- The hormones produced from CL stimulate the uterine mucosa to enter the secretory stage and prepare for implantation
- If no fertilisation occurs within 14 days the CL undergoes apoptosis and regresses (corpus albicans) and decreased progesterone levels induce menses, if fertilisation occurs hCG maintains the CL until placenta developed (corpus luteum gravidatis)
What 6 hormones does the anterior pituitary secrete?
- LH
- FSH
- TSH
- ACTH
- GH
- Prolactin
How does the ant pituitary communicate with hypothalamas?
-Superior hypophyseal artery
Describe how the hypothalamic releasing hormones are released in to the superior hypophyseal artery? How do they exert their effect at the pituitary?
- There is a basal secretion which is pulsatile in nature and is tied to the biological clock and external stimuli such as light and dark
- Also under negative feedback control from circulating hormones
- Bind to specific cell surface receptors and induce a second messenger which leads to the production of the corresponding hormone
Which hormone controls the secretion of FSH and LH? In what rhythm is it released?
- Gonadotrophin releasing hormone
- Pulsatile every hour
How do LH and FSH exert their effects on a molecular level at the gonad?
-Bind to GPCRs at gonads which are coupled to Gas -> increased in AC activity -> increased cAMP -> Increased PKA -> leads to the production of the corresponding sex steroids
Under which hormonal control is the LH surge? Explain how this works?
- High titres of oestrogen alone
- High titres of oestrogen decrease the threshold level of GnRH needed at the anterior pituitary in order to secrete LH.
How do moderate titres of oestrogen with progesterone modify the GnRH pulses?
-Oestrogen reduces the amplitude of pulses and progesterone reduces frequency
Which cells specifically do FSH and LH target in both the male and female? What do each of the cells produce?
- Male = FSH targets sertoli cells causing ABG and inhibin secretion, LH targets leydig cells causing testosterone secretion
- Females = FSH targets granulosa cells causing inhibin secretion and aromatase production. LH targets theca cells causing androgen production
What is the function of androgen binding globulin?
-binds to testosterone to keep it within the seminiferous tubule
What is the function of inhibin?
-Selectively inhibits FSH production
What will happen to spermatogenesis if testosterone levels increase? how is this prevented?
-Increase rate of spermatogenesis but also increase production of inhibin which will bring the rate back to normal
What is the dominant hormone in the luteal phase? When does production of this hormone begin and why? What phase does this mark the beginning of?
- Progesterone
- Begins just after ovulation, granulosa cells develop LH receptors and the remnants of the graafian follice undergoes leutinisation to produce corpus luteum.
- Luteal phase
Describe the follicular phase of the ovarian cycle.
- Small group of follicles are recruited independent of extragonadal signals
- No sex steroid hormones means the hypothalamus is not inhibited and causes slow release of FSH and LH which drives follicular development
- FSH binds to granulosa cells causing development by mitosis resulting in the production of inhibin and aromatase.
- Inhibin inhibits the secretion of FSH to prevent development of additional follicles
- Theca interna appears and is stimulated by LH to produce androgens
- Androgens converted to oestrogen by aromatase
- Oestrogen has +ve feedback on HPA and increased GnRH and Inhibin levels leads to LH surge
Describe the luteal phase of the ovarian cycle
- Remnants of the graafian become vascularised and luteinised and form the corpus luteum
- CL secretes oestrogen and progesterone which have a -ve feedback on HPA and prevent the production of FSH and LH -> system held in pause.
- Oestrogen and progesterone stimulate secretory phase of uterine cycle to prepare the uterus for implantation
Describe the proliferative phase of the uterine cycle. When does this occur?
- Oestrogen produced by the dominant follicle stimulates the endometrium of the uterus to proliferate
- Occurs at the same time as the follicular phase of the ovarian cycle
Describe the secretory phase od the uterine cycle. When does this occur?
- Progesterone produced by the corpus luteum causes the endometrium to become highly vascular, increases uterine secretions and decreases the motility of uterine smooth muscle
- Occurs at the same time as the luteal phase
Summarise the actions of oestrogen during the follicular phase
- Drives follicular development by increasing levels of GnRH, FSH and LH
- Stimulates the uterine endothelium to proliferate
- Stimulates think alkaline cervical mucus
- Increases motility of uterine tube
Summarise the actions of progesterone during the follicular phase
- Causes negative feedback of HPA putting cycle in pause
- Stimulates vascularisation of endometrium
- Decreases motility of uterus and uterine tubes
- Stimulates acidic mucus
- Causes changes in mammary tissue
- Increases body temperature
What is the normal length of a menstrual cycle? Why can it vary?
- 21 to 35 days
- Varying length in follicular cycle becuase luteal phase is constant +/- 2 days due t lifespan of CL
Give 3 causes of menorrhagia
- Hypothyroid
- Abnormal clotting (idiopathic thrombocytopenia)
- Fibroids (benign tumours of the endometrium increases bs to uterus)
- Iatrogenic (copper coil)
- PCOS
- Obesity (increases oestrogen)
- Progesterone contraception
Give 3 causes of amenorrhoea
- Pregnancy
- Anorexia (low oestrogen)
- Primary (absent ovaries, primary ovarian failure, excessive prolactin)
- Cryptomenorrhoea (cervical stenosis, imperforate hyman)
- Tumours
Define thelarche, pubarche, menarche and adrenache. State the order in which they occur in girls and boys
- Thelarche -> development of breast
- Pubarche -> development of axillary and pubic hair
- Menarche -> first menstrual period
- Adrenarche -> onset of increased androgen secretion
- Girls = thelarche, adrenarche, pubarche then menarche
- Boys = genital development, adrenarche, pubarche, spermatogenesis
Describe the difference between the growth spurt in males and females
-Earlier and shorter in girls due to oestrogen causing closure of the epiphyseal growth plates
What is the typical age of onset of puberty for males and female? What factors influence this in females?
- Males = ~12.5 years
- Females = ~11.5 years
- For females there is a critical weight of 47kg due to the relationship between adipose tissue and oestrogen production. (obese children start early)
Describe the hormonal changes and consequences at the start of puberty in a male
- From about 10 years old FSH and LH slowly begin to rise and spermatogenesis and androgen secretion begin at a very low level (adrenals secrete androgens but too low to initiate puberty)
- At a sufficient level androgens stimulate growth of prostate, testis and drive development of secondary sexual characteristics
Describe the hormonal changes and consequences at the start of puberty in a female
- From about 8 years old FSH and LH slowly begin to rise and oestrogen begins to be produced.
- At sufficient levels oestrogen feeds back on HPA axis and menses is initiated via the LH surge
- Oestrogen also drives progression of secondary sexual characteristics of growth of internal and external genitalia and subcut fat distribution
- Adrenals increase androgen production and this drives pubarche
What effect do androgens have on bone and muscle?
-Cause retention of minerals to stimulate growth
What is precocious puberty? Give some causes
- Onset of puberty before 8 in girls and 9 in boys
- Idiopathic
- Gonadotropin dependant causes eg hormone secreting tumour (rare)
- Gonadotropin independent causes eg meningitis
What is precious pseudopuberty? Give some causes
- Development of secondary sexual characteristics independent of HPG axis
- Alternative source of sex steroids eg anabolics
- Congenital adrenal hyperplasia
- Choriocarcinoma of gonads
Define delayed puberty. Give some causes
- Initial physical changes of puberty not present by 13 in girls (or amenorrhoea at 16) or 14 in boys or that the length of puberty is greater then 5 years
- Hypergonadotrophic hypogonadism causes (gonadal failure eg turners, atresia or chemotherapy)
- Hypogonadotrophic hypogonadism causes (hypothalamic/pituitary lesions)
Briefly describe the menopause and its effects
- Follicular phase begins to shorten and ovulation can be early or absent as primary follicles begin to run out
- Eventual cessation of the menstrual cycle for at least 12 months due to lack of follicles, produces a huge decline in oestrogen levels and a concomitant rise in FSH and LH
- Uterus endometrium regresses and myometrium shrinks, Reduced vaginal tone, involution of breasts, skin changes, reduction in pelvic tone, risk of osteoporosis as bone density decreases
Describe the blood supply and venous drainage of the testis
- Teasticular arteries straight from the abdominal aorta
- R testicular vein -> IVC, L testicular vein -> L renal vein -> IVC
What does the spermatic cord contain?
- Vas deferens
- Testicular artery, cremasteric artery, artery to vas deferens
- Genitofemoral nerve
- Lymphatics
- Surrounded by Pampiniform plexus
What is the pampiniform plexus?
-A sophisticated drainage system which acts as a heat exchanger as spermatogenesis is optimal at a few c below body temp
Describe the layers of the testis from superficial to deep
- Skin
- Subcut tissue
- Dartos fascia
- External spermatic fascia (external oblique apon)
- Cremasteric muscle and fascia
- Internal spermatic fascia
- Tunica vaginalis (peritoneum)
- Tunica albuginea (fibrous capsule)
Define the terms hydrocoele, haematocoele, varicocoele and spermatocoele
- Hydrocoele = serous fluid in tunica vaginalis
- Haematocoele is blood in tunica vaginalis
- Varicocoele is swollen varicosities of the pampiniform plexus (aching pain)
- Spermatocoele is an epididymal cyst
How are the testis innervated?
-Anterior by lumbar plexus and posterior by sacral plexus
Describe the course of vas deferens
-Leaves epididymis-> spermatic cord -> inguinal canal -> deep inguinal ring -> pelvis side wall -> passes between bladder and ureter -> joins with seminal vesicle to form ejaculatory duct
Describe the anatomical location and the organisation of the prostate. Explain where BPH and Prostate Ca occur and what the consequences of this are
-Fibromuscular gland which lies between the bladder and the rectum
-Divided into zones:
Central zone formed by the wolffian ducts and peripheral zones formed by the UGS
-BPH occurs in the central zone so enlargement causes compression of the internal urethral orifice which is in contact with the anterior surface
-Prostate cancer occurs in the peripheral zones so considerable enlargement needs to occur before it creates any symptoms so it presents later increasing the chance of spinal/brain mets
Describe the internal structure of the penis
- Pair of copora cavernosa dorsally (Erectile tissue)
- Corpus spongiosum ventrally (spongy tissue surrounding urethra)
What arteries supply the penis?
-Internal pudendal and internal iliac
What are the functions of bulbospongiosus and ischiocavernosus?
- Bulbospongiosus wraps around root of penis and helps expel residual urine
- Ischiocavernosus compresses veins to help maintain erection
Describe the anatomical landmarks of a pelvis and state which factors make a gynaecoid pelvis
- Iliac crest
- Linea terminalis (entry to true pelvis)
- Ischial spine
- Ischial tuberosity
- Sacrum
- Coccyx
- Round intel, straight side walls, not prominent ischial spines, curved sacrum, subpubic arch >90
What are pelvic conjugates?
-Distances between the anterior and posterior pelvis:
Obstetric from sacral prominance to pubic symphysis
Diagonal from sacral prominence to inferior pubic symphysis
Anatomical from sacral prominance to superior pubic symphysis
Name the anatomical parts of the uterine tubes and uterus
- Abdominal ostium, fimbrae, infundibulum, ampulla, and uterine ostium
- Fundus, isthmus, body, cervix
What is the broad ligament? Describe its sections
- Transverse fold of peritoneum which contains the uterine tubes and ovarian vessels
- Split into mesometrium which is the entire ligament
- Mesosalpinx is the section of the broad ligament covering the uterine tube
- Mesovarium is the section covering the ovary
What is the round ligament?
- Former gubernaculum which attaches ovaries to labia majora folds through inguinal canal.
- Made by round ligament of the ovary which reflects off the side wall of the uterus and becomes round ligament of uterus
What does the suspensory ligament contain?
-Ovarain vessels
What is meant by the uterus being anteverted and anteflexed?
- Anteverted refers to the angle of the between the axis of the cervix and axis of the vagina
- Anteflexed refers to the angle between the axis of the uterus and axis of the cervix
What are the main 2 ligaments which provide visceral support to the uterus?
- Transverse cervical -> Thickening at the base of the broad ligament to provide lateral stability of cervix
- Uterosacral -> Opposes pull of round liganent
Describe the innervation to the vagina
- Inferior 1/5 somatic innervation from pudendal
- Superior 4/5 and uterus from uterovaginal plexus
What are bartholin glands?
-Greater and lesser vestibular glands
Give 3 possible reasons for the increasing incidence of STIs
- Better diagnostic equipment
- Better awareness of screening
- True increase in transmission due to changing sexual and social behaviours
How is a diagnosed STI managed?
- Short course/single dose of antibiotics
- Screen for co-infection
- Contact tracing
- Sexual health education
- Advice on contraception
What STI is caused by HPV? What strains of HPV are most likely to cause this STI? With what are strains 16 and 18 associated? How is the STI treated?
- Anogenital warts
- Strains 6 and 11
- Cervical cancer
- Spontaneous resolution within 2 years, cryotherapy