Gynaecology Flashcards
What causes gonads to develop into testis?
- SRY
Describe the development of the male sexual organs
- As the gonads become testes, it differentiates into TWO cell types:
- Sertoli cells - produce anti-Mullerian hormone (AMH)
- Leydig cells - produce testosterone
- AMH suppresses further development of the Mullerian ducts
- Testosterone stimulates the Wolffian ducts to develop into the vas deferens, epididymis and seminal vesicles
- Testosterone is converted to DHT by 5a-reductase in the external genital skin to virilise the external genitalia
- The genital tubercle becomes the penis and the labioscrotal folds fuse to form the scrotum
- The urogenital folds fuse along the ventral surface of the penis and enclose the urethra
Describe the development of the female sexual organs
- In the primitive ovary, granulosa cells surround the germ cells and form primordial follicles
- Each follicle consists of an oocyte within a single layer of granulosa cells
- Thecal cells develop from the proliferating coelomic epithelium and are separated from granulosa cells by basal lamina
- The maximum number of primordial follicles are reached at 20 weeks (roughly 6-7 million)
- The numbers reduce by atresia and by birth only 1-2 million remain
- Atresia continues throughout life and about 300,000-400,000 are present at menarche
- The development of an oocyte within the primordial follicle is arrested in prophase of its first meiotic division
- It remains like this until it either undergoes atresia or enters the meiotic process preceding ovulation
- The absence of AMH in the female allows development of the Mullerian structures
- The proximal 2/3 of the vagina develop from the paired Mullerian ducts
- The midline fusion of these structures produces the uterus, cervix and upper vagina
- The unfused caudal segments form the Fallopian tubes
- Cells from the upper part of the urogenital sinus proliferate to produce the sinovaginal bulbs
- The caudal extension of the Mullerian ducts projects into the posterior wall of the urogenital sinus as the Mullerian tubercle
- The Mullerian ducts and the urogenital sinus fuse and canalise starting at the hymen and moving up to the cervix
How do the external female genitalia develop?
- Do NOT virilise in the absence of testosterone
- Cloacal folds fuse anteriorly to become the genital tubercle (this becomes the clitoris)
- The cloacal folds anteriorly are called the urethral folds and form the labia minora
- Another pair of folds within the cloacal membrane form the labioscrotal folds which form the labia majora
- The urogenital sinus becomes the vestibule of the vagina
What does the vulva (external genitalia) include?
- Mons pubis
- Labia majora
- Labia minora
- Vaginal vestibule
- Clitoris
- Greater vestibular glands
Describe the labia majora and minora
- The labia majora contain sebaceous and sweat glands
- There is a core of fatty tissue at the deepest part of each labium
- The labia minora divide anteriorly to form the prepuce and frenulum of the clitoris (clitoral hood)
- Posteriorly they divide to form the fourchette
- The labia minora contain sebaceous glands but no adipose tissue
- Both labia become engorged during sexual arousal
What is the clitoris?
- The clitoris is made up of paired columns of erectile and vascular tissue called the corpora cavernosa
What is the vestibule?
- The vestibule is the cleft between the labia minora
- It contains openings of the urethra, Bartholin’s glands and the vagina
What are the Bartholin’s glands?
- They are bilateral and about the size of a pea
- They open via a 2 cm duct into the vestibule below the hymen and contribute to lubrication during intercourse
What is the hymen?
- The hymen is a thin covering mucous membrane across the entrance to the vagina
- It is usually perforated to allow menstruation
- It is ruptured during intercourse
- Any remaining tags are called carunculae myrtiformes
Describe the vagina
- The vagina is a fibromuscular canal lines by stratified squamous epithelium
- It is longer in the posterior wall (9 cm) than the anterior wall (7 cm)
- The vault of the vagina is divided into FOUR fornices: posterior, anterior and two lateral
- NOTE: the vault is the expanded region of the vaginal canal at the internal end of the vagina
- The vaginal wall is lined by transverse folds
- The vagina has NO glands and is kept moist by secretions from the uterine and cervical glands and by transudation from the epithelial lining
- The epithelium is thick and rich in glycogen
- Before puberty and after menopause, the vagina has NO glycogen because of a lack of stimulation by oestrogen
- Doderlein’s bacillus is a normal commensal that breaks down glycogen to form lactic acid producing a low pH (this is protective as it prevents the growth of pathogenic bacteria)
- Anteriorly the vagina is in direct contact with the base of the bladder
- Laterally, at the fornices, the vagina is related to the cardinal ligaments
- Below this you see the levator ani muscles and ischiorectal fossae
- The cardinal ligaments and uterosacral ligaments form the parametrium
- At birth, the vagina is under the influence of maternal oestrogens so is well developed
- After a few weeks after birth, these effects will disappear
Describe the Uterus
- Maximum external dimensions = 7.5 cm x 5 cm x 3 cm
- Adult uterus weight = 70 g
- The cornu is the site of insertion of the Fallopian tube
- The corpus is the body of the uterus
- The area of the uterus above the cornu is the fundus
- The longitudinal axis of the uterus is roughly at right angles to the vagina and tilts forwards (anteversion)
- The uterus also flexes forwards on itself (anteflexion)
- In 20% of women, the uterus is tilted backwards (retroversion and retroflexion)
- This is of NO pathological significance
- The os is the opening of the cervix
- The internal os is where the mucous membrane of the isthmus becomes that of the cervix
- The uterus has THREE layers:
- Peritoneum - outer serous layer
- Myometrium - middle muscular layer
- Endometrium - inner mucous layer
- The peritoneum covers the body of the cervix and the supravaginal part of the cervix
- The peritoneum is attached to the subserous fibrous layer, except laterally where it spreads out to form the leaves of the broad ligament
- Externally, the myometrium consists of mostly longitudinal muscle fibres
- The thicker intermediate layer has interlacing longitudinal, oblique and transverse fibres
- Internally, they are mainly longitudinal and circular
- The inner endometrial layer has tubular glands that dip into the myometrium
- The endometrial layer is covered by a single layer of columnar epithelium
Describe the Cervix
- Roughly 2.5 cm in length
- Lateral to the cervix is the parametrium (connective tissue)
- The ureters run 1 cm laterally to the supravaginal part of the cervix
- The mucous membrane of the cervix (endocervix) has anterior and posterior columns from which folds radiate out (arbour vitae)
- It has lots of deep glandular follicles that secrete clear alkaline mucus (the main component of physiological vaginal discharge)
- The epithelium of the endocervix is columnar and ciliated in the upper 2/3
- This will transition to squamous epithelium at the squamocolumnar junction
What age related changes happen to the anatomy of the female sexual organs?
- Loss of maternal oestrogens from the circulation after birth causes the uterus to decrease in length and weight
- The cervix will be twice the length of the uterus at this point
- During childhood, the uterus grows slowly
- After the onset of puberty, the dimensions of the uterus start to increase
Describe the fallopian tubes
- Extend outwards from the uterine cornu to end near the ovary
- At the abdominal ostium, the tube opens into the peritoneal cavity
- The Fallopian tubes take the ovum from the ovary towards the uterus and promote oxygenation and nutrition for sperm, ovum and zygote
- They run in the upper margin of the broad ligament (mesosalpinx)
- This encloses the tube so that it is completely covered by peritoneum (except for a thin strip on the inferior side)
- Each tube is roughly 10 cm long and has FOUR parts:
- Interstitial portion (lies within the wall of the uterus)
- Isthmus (narrow portion adjoining the uterus)
- Ampulla (widest and longest part)
- Infundibulum or fimbrial portion (opening of the tube into the peritoneal cavity)
- One of the fimbriae extend and partially embrace the ovary
- The muscular wall of the tube has an inner circular and an outer longitudinal layer
- The tube epithelium forms a number of folds or plicae that run longitudinally
- There is NO submucosa and NO glands
- The epithelium has TWO cell types:
- Ciliated cells (produce a constant current of fluid in the direction of the uterus)
- Secretory cells (contribute to the volume of tubal fluid)
Describe the Ovaries
- Size and appearance depends on age and stage of the menstrual cycle
- Proliferation of stromal cells in puberty makes them grow in size (reaching 3 cm long x 1.5 cm wide x 1 cm thick)
- The ovary becomes smaller after menopause
- The ovary is the only intra-abdominal structure that is NOT covered by peritoneum
- Each ovary is attached to the cornu of the uterus by the ovarian ligament
- It is also attached to the broad ligament by the mesovarium, which contains nerves and blood vessels
- Laterally, each ovary is attached to the suspensory ligament of the ovary with folds of peritoneum that become continuous with the overlying psoas major
- Anterior to the ovaries are the Fallopian tubes, superior portion of the bladder and the uterovesical pouch
- Posterior to the ovary is the ureter
Describe the structure of the ovaries
- It has a central vascular medulla consisting of loose connective tissue containing elastin fibres and non-striated muscle cells
- It has an outer thicker cortex which is denser than the medulla
- It contains networks of reticular fibres and fusiform cells
- The surface of the ovaries has a single layer of cuboidal cells (germinal epithelium)
- Underneath this layer is another layer called the tunica albuginea (increases in density with age)
- At birth, most primordial follicles are found within the cortex
- After puberty, some follicles become Graafian follicles and ovulate and become the corpus luteum
- This will ultimately undergo atresia and become the corpora albicans
Describe the bladder
- The bladder is made of involuntary muscle arranged in an inner longitudinal layer, middle circular layer and outer longitudinal layer
- It is lined by transitional epithelium
- The average capacity is 400 mL
- The ureters open into the base of the bladder after running through the bladder wall for about 1 cm
- The internal meatus of the urethra is known as the trigone
- The base of the bladder is adjacent to the cervix
- It is separated from the anterior vaginal wall by pubocervical fascia that stretches from the pubis to the cervix
Describe the urethra
- Roughly 3.5 cm long
- Lined with transitional epithelium
- Smooth muscle of the wall is arranged into outer longitudinal and inner circular layers
- The upper part of the urethra is mobile but the lower part is relatively fixed
- On voluntary voiding of urine, the base of the bladder and the upper part of the urethra descend and the posterior angle disappears so that the base of the bladder and the posterior wall of the urethra come to lie in a straight line
Describe the ureter
- As the ureter crosses the pelvic brim, it lies in front of the bifurcation of the common iliac artery
- It reaches the pelvic floor and then passes inwards and forwards to attach to the peritoneum of the back of the broad ligament, passing under the uterine artery
- It then passes through the ureteric canal
- It runs close to the lateral vaginal fornix to enter the trigone of the bladder
- Its blood supply is from small branches of the ovarian artery
- IMPORTANT: the ureter can get damaged during a hysterectomy (e.g. cut, tied, necrosis due to interference with blood supply)
Describe the rectum
- The rectum begins at the level of the 3rd sacral vertebra
- The front and sides are covered by the peritoneum of the rectovaginal pouch
- The lower third of the rectum has no peritoneal covering and the rectum is separated from the posterior wall of the vagina by the rectovaginal fascial septum
- Lateral to the rectum are the uterosacral ligaments alongside which run some of the lymphatics draining the cervix and vagina
What is intermenstrual bleeding?
- bleeding between periods, often seen with endometrial and cervical polyps and endometriosis
What is post-coital bleeding?
- Beeding after sex. Associated with cervical abnormalities
What is postmenopausal bleeding?
- Bleeding more than 1 year after cessation of periods. Exclude endometrial pathology or vaginal atrophy