Female reproductive system - normal Flashcards
Imaging female reproductive
system? - What are the advantages and disadvantages of Transabdominal or transvaginal
ultrasound?
Produces secondary oocytes and hormones.
Provides sites of fertilisation, implantation and development and delivery of the fetus.
What is the uterus and its function?
Hollow, muscular organ within the pelvis
Pear shaped.
Positioned anterior to the rectum and posterior to the bladder in non pregnant females
It lies mostly within the pelvis cavity
In non pregnant women it measures approximately 7.5cm in length and 5cm in diameter.
It is nearly 2.5cm thick.
It is divided into
Fundus – top part
Body / corpus – central part
Cervix – lower part projecting into the vagina
The body is divided into 3 layers
Endometrium – inner mucosal layer which undergoes the cyclic changes during the menstrual cycle and is shed during menstruation
Myometrium – the thick muscular middle layer responsible for uterine contractions during menstruation and childbirth
Serosa (perimetrium) – the outermost think peritoneal later covering the uterus
Pathway for sperm to reach the fallopian tubes.
To receive, retain, protect and nourish the fertilised ovum and developing embryo / fetus.
To expel the mature fetus at the end of pregnancy.
What is the Position of the uterus?
It is held in place by ligaments – 2 of each
Uterosacral ligaments from posterior cervix to sacrum
Cardinal ligaments from side of cervix to ischial spines
Pubocervical ligament
From side of cervix to pubic symphysis
Blood supply to the uterus description
Arterial blood passes into the internal iliac artery and then into the uterine arteries.
The uterus has an extensive blood supple which is essential to support regrowth of the endometrium and implantation of the ovum and development of the placenta.
Functions of the cervix
Acts as a mechanical barrier to infectious microorganisms present in the vagina.
The external os is a very small opening with thick sticky mucous – plug.
During ovulation, the plug becomes watery to facilitate sperm travel under the influence of oestrogen.
What is the cervix?
This is the lower part of the uterus situated between the external os and the internal os
The cervical canal connects the interior of the vagina and the cavity of the body of the uterus
It is 2-3cm in length
Width depends on age – widest in premenopausal women at 8mm
It dips into the vagina forming the fornices (anterior, posterior and lateral)
The cervical canal contains:
The internal and external os
The hymen
Cervix anatomy
Internal os
The opening of the cervix into the body of the uterus
External os
The opening of the cervix into the vaginal.
Its shape and size varies widely with age, hormonal state and if a woman has had a vaginal birth.
In non parous women it is a small circular opening
In parous women it is wider and more slit like
What is the vagina?
Thin walled, distensible tube, approximately 8-10cm in length
Lies posterior to the urethra and anterior to the rectum
It is a muscular canal lined with a mucous membrane
It is an acidic environment that retards microbial growth. But this is harmful to sperm as well
The alkaline components of semen raise the PH to increase the viability of sperm
Also called the birth canal
What are Fallopian tubes?
Also called the uttering tubes
Bilateral tubular structures connecting the ovaries to the uterus
Function
Transport the mature ova from the ovaries to the uterus
The site where fertilisation commonly takes place if spermatozoa are present
Anatomy of the fallopian tube
The fallopian tubes are divided into
Infundibulum – funnel shaped segment
Ampulla – longest segment
Isthmus – thicker walled segment close to the uterus
The fallopian tubes are approximately 10cm in length and 1cm wide
They run laterally from the uterus through the peritoneum
Distal end curves around ovary - ampulla
Infundibulum – distal part of tube – funnel shaped terminating in fimbriae
Tube narrows as it runs medially from the ampulla
Narrowest segment at entry to uterus - isthmus
Blood supply to the fallopian tubes
Blood supply is from branches of the ovarian and uterine arteries
Blood drainage is via the ovarian and uterine veins
How do the fallopian tubes work?
An oocyte is released from the ovary into the peritoneal cavity
The fimbriae of the tubes drape over the ovary
The oocyte is captured by the fimbriae and swept into the tube
Cilia line the fallopian tubes
The cilia move in a beating movement in the direction of the uterus to create current in the surrounding peritoneal fluid towards the ampulla
The smooth muscles of the fallopian tube generate peristalsis movements which move the ovum along the tube towards the uterus
The ovaries – functions
Oogenesis:
Production and release of mature ova (egg)
Endocrine function:
Secretion of hormones
Oestrogen
Progesterone
The ovaries - anatomy
Bilateral, almond shaped organs situated laterally in the peritoneal cavity
Measure approximately 3x3x2cm but size depends on age and hormonal status
- Double in size during pregnancy
- Smaller and then atrophic during / after menopause
Each ovary is divided into:
An outer fibrous coat
Cortex – contains up to 2 million primary oocytes at birth
Approximately 10 mature each cycle, only 1 becomes the dominant follicles.
The primary follicle becomes the Graafian follicle.
The other follicles close down .
Medulla
- The central part containing blood vessels, lymphatic vessels and nerves.
They are held in place by ligaments that anchor them to the pelvis wall and uterus.
They are suspended in a double fold of the peritoneum called the mesovarian.
Ovaries – blood and nerve supply
Nerve supply to the ovaries runs with the vasculature and enters at the hilum
Lymphatic drainage is to the lateral aortic and iliac nodes
Blood supply is via the ovarian artery which branches form the descending aorta
The ovarian artery and vein enter at the hilum
Left ovary drains into the left renal vein
The right ovary drains into the inferior vena cava
Pathophysiology of follicle development
Small groups of follicles mature in a cyclic manner under the influence of FSH after puberty
The follicles develop from a primordial follicle, to a secondary follicle and then 1 follicle becomes the tertiary or Graafian follicle.
The Graafian follicle contains the primary oocyte and fluid.
The primary oocyte divides by meiosis to form a secondary oocyte which is released into the abdominal cavity during ovulation (day 14 of the menstrual cycle)
The Graafian follicle ruptures and the released oocyte is caught and transported to the uterus.
The tissue left over from the rupture of the Graafian follicle forms into a mass called the corpus luteum. This will persist if there is fertilisation and implantation or will regress into a fibrous scar called corpus albicans if implantation does not occur.
The follicles secrete oestrogen as they grow.
The corpus luteum produces progesterone and oestrogen, relaxin and inhibin until it degenerates.
Imaging Ovaries - Ultrasound
On ultrasound the ovaries look like elliptical / oval structures with an echogenic focus.
During the early menstrual cycle, multiple anechoic follicles can be seen
In this image you can see several follicles of 4-6mm along the edge.
The menstrual cycle
The menstrual cycle is regulated by the complex interaction of hormones:
Pituitary hormones
Follicle stimulating hormones (FSH)
Luteinizing hormone (LH)
Ovarian hormones
Oestrogen
progesterone
It consists of 2 cycles:
The uterine cycle
The menstrual, proliferative and secretory phases
The ovarian cycle
The follicular phase, ovulation and the luteal phase
Day 1 of the menstrual cycle is the first day of a period
The purpose of ovarian hormones are to:
Produce a mature ovum for fertilisation
Prepare the endometrium for the fertilised ovum
Support an early pregnancy
Days 1-4 – menstruation
Uterine cycle:
The endometrium is shed as hormonal support is withdrawn
Vaginal bleeding occurs
Myometrial contractions
Rising oestrogen levels stimulate growth of new endometrium
Ovarian cycle – days 1-14:
Called the follicular phase
Menstruation lasts approximately 1-7 days
FSH and LH are released from the pituitary gland
This induces development of the follicles
The ovarian follicles produce oestradiol and inhibin
This supresses FSH
As a result normally only 1 oocyte develops
The dominant follicle forms
Day 5-13 – proliferative
Uterine cycle:
Hormones from the hypothalamus stimulate FSH and LH release from the pituitary gland
There is proliferation of the cells in the endometrium causing thickening
Day 12-15 – peri-ovulatory
Uterine cycle:
Pituitary and hypothalamus cause LH levels to rise sharply
Ovulation occues 36 hours after the LH surge
Ovarian cycle:
Called ovulation
Increased levels of oestradiol reach a maximum on ay 13
LH levels rise sharply
Ovulation occurs 36 hours after the LH surge
Day 12-15 – peri-ovulatory
Enometrium has a 3 line sign – hypoechoic with a hyperechoic rim
Day 15-28 – secretory
Uterine cycle:
The ovarian corpus luteum produces progesterone and oestradiol
Progesterone levels peak around day 21 causing changes in the endometrium – blood supply increases and cells enlarge
Without fertilisation the ovarian corpus luteum fails and progesterone and oestrogen levels fall
Hormonal support is withdrawn
The endometrium breaks down and menstruation occurs
Ovarian cycle:
Following release of the ovum, the dominant follicle becomes the corpus luteum.
The corpus luteum produces oestradiol and increasing levels of progesterone.
This peaks around day 21.
This peak induces.
Summary – normal ovarian cyclical changes
Normal ovary develops follicles (1-2mm) every 28 days
The dominant follicle develops (follicular phase)
The dominant follicle ruptures mid cycle at ovulation as LH reaches a peak and oestrogen levels are high (ovulatory phase).
After ovulation the corpus luteum forms (early luteal phase)
Without fertilisation the corpus luteum regresses (late luteal)
Ovarian changes over time
Postmenopausal ovaries
Decrease in size with age – often hard to see on US
Premenarchal ovaries
Best viewed transabdominally.
Look like small structures.
During adolescence there is a growth of follicles which can be mistaken for polycystic ovaries.
Reproductive age ovaries
Changes occur due to hormone fluctuations
