W2 - FEMALE REPRODUCTIVE SYSTEM

Question 1

What is the function and location of the ovaries in the female reproductive system? Decribe the decent of the ovaries and its arteries and veins

Answer 1

• These are the gonads which produce the gametes in the female reproductive system
• These are the equivalent of testes in men (except producing the ovum)
• They are located within a fold of peritoneum which covers the uterus and uterine tubes
• During foetal development, the ovaries develop within the abdominal wall and descended down into the pelvic region stopping in the lateral part of the pelvis
• The gubernaculum is the structure which facilitates this descent, however this changes into two structures
  
  • Ovarian ligament (attaches the ovary to the junction between the uterine tube and the uterus)
  • Round ligament of the uterus (connects the uterus with the vagina, going into the deep inguinal ring and through the inguinal canal)
• It is important to note that the ovaries are not physically connected to the uterine tubes, but rather is an open pathway (thus it is a potential pathway for pathogens to enter the pelvic region)
• Ovarian arteries and veins
  
  • Left ovarian vein drained into the left renal vein (Eventually joining the inferior vena cava)
  • Right ovarian vein goes straight into inferior vena cava

Question 2

What structures are formed by the peritoneum? What are the three parts of the broad ligament?

Answer 2

• The peritoneum drapes down over the bladder, uterus and rectum
• This forms the vesico-uterine pouch anteriorly and the recto-uterine pouch posteriorly (which is the lowest part of the pelvic cavity)
• The peritoneum also covers the uterine tubes and ovaries which is then known as the broad ligament
• There are three parts to this ligament
  
  • Mesometrium connects walls of the uterus laterally to the walls of the pelvis
  • Mesosalpinx is the part of the peritoneum covering the uterine tube
  • Mesovarium posteriorly connecting the ovary to the mesosalpinx
    
    • This structure is also associated with forming the coverings of the ovary
• The suspensory ligament of the ovaries is another structure coming from the broad ligament which contains the vessels and nerves that supply the ovaries
• Goes from uterus to pelvic wall

Question 3

Observe and describe the relationship of the uterus with the rectum and the bladder

Answer 3

• Uterus is positioned between rectum and bladder; bladder anterior and rectum posterior
• Uterus often tilts forward (anterverted/anteflexed) over bladder

Question 4

Identify the recto-uterine and vesico-uterine pouches. Where are these pouches and how have they formed?

Answer 4

• Recto-uterine pouch - Part of peritoneal cavity that lies between rectum and posterior wall of uterus
• Vesico-uterine pouch - Part of peritoneal cavity that lies between bladder and anterior wall of the uterus; anterior pouch of peritoneum is shallower than posterior one

Question 5

Observe, name and describe and the two main ligaments that suspend the ovaries in the pelvic cavity

Answer 5

• Suspensory ligament connects to lateral wall of pelvis; this ligament also conveys ovarian vessels, lymphatics and nerves and constitutes lateral part of mesovarium of broad ligament
• Ovarian ligament also attaches ovary to uterus and also runs in mesovarium of broad ligament; it is a remnant of the gubernaculum

Question 6

What are the three main bands of pelvic fascia?

Answer 6

• Underlying this peritoneum which has come down from the abdominal cavity is the pelvic fascia
• There are three main bands
  
  • Pubocervical ligament
    
    1. Attaches from the pubis, blending with the bladder, before terminating at the cervix
    2. Prevents cystocele where the bladder bulges (Herniates) into the anterior wall of the vagina due to weakness in this fascia.
  • Lateral/transverse cervical ligament (Cardinal ligament)
    
    1. Attaches from the cervix to the lateral pelvic wall
    2. Important for the supporting and providing stability to the cervix
  • Uterosacral ligament
    
    1. Is located posteriorly
    2. From the cervix/uterus to the sacrum
    3. Which supports the pelvic diaphragm and support to the uterus and cervix
    4. These do provide some movement

Question 7

What causes uterine prolapse? What are some factors contributing to pelvic organ prolapse?

Answer 7

• Uterine prolapse due to weakening in the uterosacral and/or cardinal ligaments
• Rectovaginal fascia
  
  • Separates the vagina (anterior) from the rectum (posterior)
  • Provides support to rectum
  • Defects in this fascia contribute to rectocele (Rectum bulging forward into vagina), also called posterior vaginal wall prolapse
    
    • Prolapse is a condition in which the organs fall out of place
• Factors contributing to pelvic organ prolapse (uterus, bladder, rectum etc)
  
  • Increased turnover of collagen in connective tissue → Less stable/mature collagen
  • Muscular damage to levator ani in parturition (risk increases 3% for each 100g increase in infant birthweight)
  • Neural damage in parturition
  • BMI (risk increase 3% for each unit of BMI)
  • Ageing

Question 8

What is the uterus? Describe the position of the uterus and uterine body

Answer 8

• Broadly speaking, most of the uterus is simply referred to as the body, with the inside known as the uterine cavity (triangular if sectioned in the coronal plane)
• The uterus narrows as it starts towards the vagina, this narrowing is known as the cervix
• The section just above the junction of the uterine tubes is the fundus
• The uterus is anteverted (bent at an angle to the vagina) meaning it is tilted forwards
• The axis of the uterine body is also at an angle to the cervix (this is anteflexed)
• The position of the uterus is dependent on the degree to which the uterus is filled

Question 9

How does an ovum (egg) get from the ovary to the uterus?

Answer 9

• Egg expelled into peritoneal cavity but trapped by fimbriae of infundibulum of uterine tube which drapes over ovary; movement of uterine tube and beating cilia of fimbriae create currents in peritoneal fluid that move oocyte into uterine tube; then peristalsis of uterine tube and beating cilia of uterine mucosa carry oocyte toward uterus

Question 10

Define the terms anteverted and anteflexed

Answer 10

• Anteverted - Inferior or cervical part of uterus anteverted if inclined anteriorly (Uterus tipped forward over bladder); this is the more common position of uterus although some women have retroverted uterus tipped posteriorly
• Anteflexed - Fundus (superior part) tipped forward relative to cervix

Question 11

Describe the normal support mechanisms for the uterus within the pelvis

Answer 11

• Passive support - From bladder as uterus is anterverted and so rests on bladder
• Ligamentous - Broad ligament (peritoneum) supports uterus laterally (peritoneum folds over uterus and holds it to lateral walls and floor of pelvis); lateral cervical ligaments (cardinal) connect cervix and fornix of vagina to lateral pelvic wall; uterosacral ligaments extend from sides of cervix to middle of sacrum; round ligament binds uterus to anterior abdominal wall, runs through inguinal canal to fuse with fibres in labia majora; restricts superioposterior movement of uterus (e.g. during bladder filling); all these ligaments hold uterus in place but allow for mobility so bladder and rectum can be filled and emptied without too much restriction by uterus
  
  • Pubovesical ligaments connect neck and pelvic part of urethra to posteroinferior aspect of each pubic bone
• Muscular - Pelvic diaphragm is dynamic support; maintains tonus (low level contraction) while standing and sitting and active contractions during periods of increased intra-abdominal pressure (coughing, sneezing, lifting)

Question 12

Identify pelvic structures that would normally assist in maintaining urinary continence

Answer 12

• Voluntary urethral sphincter comprised of sphincter urethrae (proximal two thirds of urethra), and compressor urethrae and urethrovaginal sphincter anterolaterally
• Latter two serve to maintain resting urethral closure through constant low level contraction
• Also contribute to voluntary closure and reflex closure during acute instances (e.g. coughing, sneezing, laughing) of increased intra-abdominal pressure
• Fascia in this area attached to perineal membrane anteriorly, and laterally to levator ani muscles through tendinous arch
• Connective tissue extends bilaterally from inferior part of pubic bone along junction of fascia of obturator internus and levator ani muscle group to near ischial spine
• This tissue provides secondary support to urethra, bladder neck, and bladder base
• Defects in this tissue believed to result in cystocele development (herniation of bladder into vagina) and urethral hypermobility
• Primary support to this area and entire pelvic floor believed to be levator ani muscle complex
• At rest, constant tone mediated by low level muscle contraction thought to constitute major supportive mechanism
• Similar to urethral sphincter muscle groups, fast-twitch fibres of levator ani complex aid in suddenly stopping urinary stream during voluntary guarding reflex
• With acute increases in intra-abdominal pressure, forceful contraction of fast-twitch levator fibres elevates pelvic floor and tightens connective-tissue planes, thereby supporting pelvic viscera

Question 13

Define and describe the layers of the uterus wall

Answer 13

• There are three layers to the uterus wall
  
  • Endometrium
    
    1. Is the inner glandular mucosa layer
    2. Is formed in two layers, the functional layer (which grows to a thick, highly vascularised tissue prior to implantation of the blastocyst) and the basilar layer (which is home to stem cells which are responsible for the regrowth of the functional layer after menstruation)
    3. The blood supply to this layer is under hormonal influences
    4. Straight arteries supply the basal layer, and spiral arteries that go up into the functional layer
       
       1. Spiral arteries important as they can coil up during menstruation to remove this layer
    5. With increasing progesterone concentration, the spiral arteries will coil up tighter, causing ischemia
    6. This lack of blood supply causes cell death, effectively leading to the menstrual phase of the menstrual cycle
  • Myometrium
    
    1. Is about 90% of the mass of the uterus
  • Perimetrium
    
    1. Is continuous with the overlying broad ligament
• The uterus is supplied by the uterine artery, which comes of the anterior branch of the internal iliac artery

Question 14

Describe the structure of the uterine tube

Answer 14

• The uterine tube connects the ovaries with the uterus
• It is also known as the oviduct or the fallopian tube
• The ovaries propel the oocyte to the uterine tube
• The uterine tubes are not connected directly to the ovaries, but rather have this structure called an infundibulum which contains fimbriae that drape over the ovaries
• The job of these structures is to draw the ovum into the uterine tubes through creating a current
• There is then the ampulla, which is the region that fertilisation would generally occur
• Following on from the ampulla is the isthmus
• The intramural segment of the uterine tube is the next section, and is the one to join the two structures

Question 15

Describe the histology of the ampullary region and oviduct mucosa

Answer 15

• Ampullary region
  
  • In ampulla
  • The complex folds have cilia that propel the fertilised eggs from the ovary into the uterus
  • Smooth muscle helps move eggs through peristalsis
• Oviduct mucosa (Inner lining of the oviduct)
  
  • Simple columnar hence for secretions
  • Have cilia
• Ciliated and non-ciliated simple columnar epithelium surrounded by smooth muscle
• Ovarian end ~60-80% ciliated cell
• Uterine end mostly secretory cells, only ~25% ciliated
• Transport of materials along duct by ciliary movement and peristalsis of smooth muscle
• Ciliation under influence of oestrogen
• Non-ciliated mucosal cells have microvilli and produce secretions containing nutrient sources for spermatozoa, oocytes and developing pre-embryo

Question 16

What is an ectopic pregnancy? What is the most common location?

Answer 16

• If the fimbriae and infundibulum fail to do their job, and do not catch the ovulated oocyte, it is possible for the egg to be lost to the pelvic cavity
• If this egg is then fertilized, it may implant in the wrong area (not in the uterus as it should)
• The most common of these ectopic pregnancies are tubal (in the various regions of the uterine tube)
• If this happens and it is not discovered in the first 8 weeks, it will haemorrhage and seriously endanger the mother

Question 17

What are the three phases to the menstrual cycle?

Answer 17

• There are three phases to the menstrual cycle
  
  • Proliferative phase
    
    • Starts from the end of the last menstruation
    • The functional layer (stratum functionalis) of the endometrium is restored by the synchronous proliferation of glands, stroma and vessels from the basilar layer - increased thickness of stratum functionalis
    • This occurs under the influences of increasing oestrogen
    • Endometrial glands have pseudostratified columnar epithelia, some ciliated cells
    • Proliferation of stromal cells - dense aggregation amongst glands
  • Secretory phase
    
    • In the secretory phase the functional layer is prepared for implantation
    • This occurs after ovulation and is stimulated by progesterone
    • The spiral arteries continue to lengthen and coil
    • Mid‐secretory endometrium shows glandular coiling with luminal secretions
    • Late secretory endometrium shows serrated appearance of glands, often containing exfoliated cells or cell fragments in lumens
    • Stromal cells very abundant and predecidual cells (PD) in stroma around arterioles
    • These cells transform to decidual cells on implantation of blastocyst and contribute to formation of placenta
  • Menstrual phase
    
    • If implantation does not occur, menstruation occurs, which involves shedding of the stratum functionalis
    • This occurs due to a decreased progesterone and decreased oestrogen that cause constriction of the coiled arteries stopping all blood flowing through them
    • The blood haemorrhages - blood does not clot due to fibrinolysis (breakdown of clots) due to prostacyclin and nitric acid
    • Thus, the entire functional layer is shed as menstrual discharge
    • The process then starts again

Question 18

Describe the anatomy of the cervix

Answer 18

• Is the narrow opening of the uterus to the vagina
• This cervix is broken up into three parts
  
  • The internal os (opening into the uterus)
  • Cervical canal (in between these two, is simple columnar epithelium)
  • External os (opening into the vagina, is stratified squamous epithelium)
• As the cervix actually protrudes a little into the vagina, a ‘gutter’ is formed around the outside of the cervix known as the fornicies
• Are both anterior and posterior fornix
• Within the cervix is a transition zone known as the transformation zone (the change from stratified squamous to simple columnar)
• The location of this junction changes with age
  
  • Prior to puberty and after menopause, the stratified squamous epithelium will extend further into the cervical canal
  • During the reproductive years, there needs to be more cervical mucous (to stop pathogens, sperm during pregnancy) so there is a greater amount of simple columnar epithelium
• This transformation zone is the area that is most likely to undergo pathogenic changes (precancerous changes)
• This is the region of cells that pap smears look at for precancerous cells
• The endocervix consists of simple columnar cells
• The ectocervix consists of stratified squamous

Question 19

Describe the anatomy of the vagina

Answer 19

• Is a fairly thin walled tube that is about 8-10cm long
• Near the fornices it is expanded, and is known as the vaginal vault
• The vagina is an acidic environment which provides protection against pathogenic fungi and bacteria
• It also provides protection against sperm
  
  • The reason the vagina is acidic, is that within the mucosal layer there is a high amount of glycogen which is used by bacteria for energy (of which the by-product is lactic acid which makes the environment acidic)
• It has a mucosal layer, stratified squamous epithelium layer, and a muscle layer
• The vaginal wall is made up of stratified squamous epithelium (continuous with the opening of the cervix)
• This layer will thicken during the reproductive years
• The muscular layer is smooth tissue and is surrounded at the opening of the vagina by the bulbospongiosus muscle
• Lubrication of the vagina is produced by the cervical glands superiorly and the greater vestibular gland in the vestibule below

Question 20

Describe the external genitalia in the female reproductive tract

Answer 20

• Are those structures within the superficial perineal pouch and superficial to that structure
• These external genitalia include
  
  • Mons pubis (which is the mound of the pubic symphysis)
  • Labia majora (equivalent of the scrotum)
  • Labia minora (bound the area known as the vestibule)
  • Vestibule (in the inner region that houses the opening of the urethra and vagina)
  • Hymen (covers the vagina, is perforated to allow the flow of menarche)
  • Clitoris (is hooded by the prepuce that is formed by the labia minora coming together anteriorly)

Question 21

Describe the erectile tissues and glands of the female reproductive tract

Answer 21

• Deep to the external genitalia (in the superficial perineal pouch) are the erectile tissues and glands
  
  • Clitoris
  • Corpus cavernosum (erectile tissue that combines to make the clitoris)
  • Bulb of vestibule (erectile tissue that combine with the corpus cavernosum to make the clitoris)
  • Greater vestibular glands (produce mucous to help with lubrication)
  • Lesser vestibular glands or skenes glands (are scattered under the tissue under the vestibule)

Question 22

Which layer of the uterus is lost and regenerates every month? Into which layer would a fertilised egg embed?

Answer 22

• Stratum functionalis of the endometrium

Question 23

What is the functional significance of a change in location of the transformation zone at the cervix?

Answer 23

• The transformation zone in reproductive years is located near the external os of the cervix where its secretions can either facilitate entry of sperm into the uterus (pre-ovulatory), or under hormonal influence (post-ovulatory), produce more viscous mucus which forms a cervical plug that blocks entry of sperm and pathogens
• Prior to puberty and after menopause, when the secretions above are not required, the transformation zone is located further into the cervical canal away from the external os

Question 24

Describe the histological features of the uterine tube that assist a healthy pre-embryo on its journey to implantation in the uterus

Answer 24

• Extensive folding of mucosa increases surface area for delivery of nutrients; cilia on epithelial cells lining lumen and smooth muscle of muscularis create ciliary movement and peristalsis to transport fertilised egg along duct to uterine cavity

Question 25

What classification of epithelium lines the vagina?

Answer 25

• Stratified squamous

Question 26

How does the vagina maintain lubrication without glands?

Answer 26

• Surface of vaginal wall lubricated by mucus mainly from cervical glands, also from greater and lesser vestibular glands in walls of vaginal vestibule

Question 27

What is the glycogen in the vaginal epithelium used for?

Answer 27

• Commensal vaginal bacteria use glycogen as substrate to produce lactic acid, maintaining acidic environment that protects against pathogenic bacteria and fungi