O&G Clinical Anatomy Flashcards
What are the functions of the bony pelvis?
- Support of the upper body when sitting and standing
- Transference of weight from the vertebral column to the femurs to allow standing and walking
- Attachment for muscles of locomotion and abdominal wall
- Attachment for external genitalia
- Protection of pelvic organs, their blood & nerve supplies, their venous and lymphatic drainage
- Passage for childbirth
What makes up the bony pelvis?
2 hip bones, sacrum, coccyx
Which 3 bones make up the hip bones?
Ilium, ischium and pubis
- Label these parts of if the bony pelvis
*
What is the name of the angle formed by the pubic arch?
Sub-pubic angle
*What forms the pelvic inlet?
sacral promontory, ilium, superior pubic ramus and pubic symphysis
*What forms the pelvic outlet?
Pubic symphysis, ischiopubic ramus, ischial tuberosities, sacrotuberous ligaments and coccyx
*What is the pelvic cavity situated between?
Pelvic inlet and pelvic floor
Which pelvic structure is used to measure gestation in pregnancy?
Pubic symphysis
Which pelvic structures can be used to determine stations during birth, and = station 0?
Ischial spines
What kind of joint is the pubic symphysis?
Secondary cartilaginous (secondary cartilaginous often occur in the midline)
What kind of joint is the sacroiliac joint?
Generally synovial anteriorly, fibrous posteriorly
What are the 2 ligaments of the pelvis that dont cross or stabilise joints, but prevent vertical displacement of the sacrum when weight suddenly moves vertically e..g jumping or late pregnancy?
Sacrotuberous and sacrospinous ligaments
What are the 2 ligaments of the pelvis that dont cross or stabilise joints, but prevent vertical displacement of the sacrum when weight suddenly moves vertically e..g jumping or late pregnancy?
Sacrotuberous and sacrospinous ligaments. (They also form the greater and lesser sciatic foramina)
What is the attachment of the sacrotubrous and sacrospinous ligaments, and which is most posterior?
Sacrotuberous: sacrum + coccyx to ischial tuberosity
Sacrospinous: sacrum + coccyx to ischial spine (this is the most posterior)
What arteries, veins and nerves are at risk of damage in pelvic fractures?
Common iliac artery and common iliac vein, and sacral plexus
What are the main differences between the male and female pelvis?
- AB and transverse diameter of the inlet and outlet are wider in females
- Sub-pubic angle is wider
- Pelvic cavity is shallower in female
- Sacral promontory is larger in males, making pelvic inlet heart shaped
- Acetabulum is more medial in females, and wider
What is the name of the space between foetal cranial bones?
Fontanelles
*Vertex
Diamond shaped area of the skull between the parietal eminence and anterior + posterior fontanelles
Movement of one bone over another to allow the foetal head to pass through the pelvis during labour, aided by sutures and fontanelles
Moulding
In what direction should the foetus be facing when it enters the pelvic cavity and why?
Transverse direction (to the right or left) because the occipitofrontal diameter of the foetus’ head is larger than the biparietal diameter, which matches the mums pelvis which is wider transversely than it is AP
How should the baby’s head position change when descending through the pelvic cavity, and then exiting the cavity?
It should rotate and end up in a flexed position, and then leaving the cavity in an extended occipitoanterior position (occiput facing up, and face down). Once the baby is delivered there is further rotation to the the shoulders and the rest of the baby can be delivered.
What borders do the inferior part of parietal peritoneum form?
Floor of peritoneal cavity and roof over pelvic organs
Where would any excess fluid in the upright female collect, and how is this drained?
Recto-uterine pouch (Pouch of Douglas). This is drained via needle through the posterior fornix of the cavity
What are the two pouched formed by the peritoneum in the female?
Vesico-uterine, and recto-uterine (Pouch of Douglas)
What is the pouch formed by the peritoneum in the male?
Recto-vesical
What is the broad ligament and what is its function?
Double layer of peritoneum, helps maintain the uterus in it correct midline position
What is the round ligament, and where does it attach?
An embryological remnant which passes through the deep inguinal ring to attach to the superficial tissue of the female perineum
What holds the uterus in position, and what can occur if these are weak?
Number of strong ligaments e.g. uteroscaral, endopelvic fascia and pelvic floor muscles. Weakness of these can result in prolapse
What are the 3 layers of the body of the uterus?
Perimetrium, myometrium and endometrium
*What is the most common position of uterus?
Anteverted and ante flexed
What is a normal variation of uterine position?
Retroverted and retroflexed
What junction must be sampled in a smear test?
Squamo columnar junction
What is the risk with the uterine tubes opening into the peritoneal cavity?
Infection could pass between the two areas, e.g. PID, or ectopic pregnancy
True or False: the walls of the vagina are normally collapsed and in contact
True, except superiorly where the cervix holds them apart forming a fornix
What are the 4 parts of the cervical fornix?
Anterior, posterior and 2 lateral
How is the position of the uterus palpated during digital examination?
Using bimanual palpation through posterior fornix
How is the position of the adnexae (uterine tubes and ovaries) palpated during digital examination?
Bimanual palpation through lateral fornices and over iliac fossa with the other hand (normally non-palpable)
Where is the perineum located?
Between the pelvic diaphragm (pelvic floor mostly) and the skin
When is the pelvic floor contracted?
Trick question! It is tonically contracted all of the time, but contracts further reflexively in situations of increased intra-abdominal pressure
*Perineal body
bundle of collagenous and elastic tissue just deep to the skin into which the perineal muscles attach - important for pelvic floor strength
*Bartholins glands
Secrete mucous to lubricate the opening to the vagina (similar to bulbourethral glands in males)
Which ribs do the bed of breasts extend over, from which borders?
Ribs 2-6 (lateral border of sternum to mid-axillary line)
Retromammary space
Lies between deep fascia and breast
*What attached the breast to the skin?
Suspensory ligaments
Where does the majority of lymph from the breast drain?
Ipsilateral axillary lymph nodes, then to supraclavicular
Where can lymph from the inner breast drain to?
Parasternal LNs
Where can lymph from the lower inner breast drain to?
Abdominal LNs
*How is the extent of clearance of axillary nodes described?
As levels, in relation to the pectoralis minor.
- Level I – inferior and lateral to pectoralis minor
- Level II – deep to pectoralis minor
- Level III – superior and medial to pectoralis minor
Is the pelvis a body cavity or body wall, and therefore which type of nerves is it innervated by?
It is a body cavity and so is autonomic: innervated by sympathetic, parasympathetic and visceral afferent
Is the perineum a body cavity or body wall, and therefore which type of nerves is it innervated by?
It is a body wall and so is somatic: somatic motor and sensory
*Superior aspects of pelvic organs touching the peritoneum e.g. uterine tubes, uterus: Which type of nerves are these supplied by, and which fibres do these follow and at which level do they enter the spinal cord?
Visceral afferents (as pelvic) which run alongside sympathetic fires to T11-L2.
Where is the pain perceived with insult involving pelvic organs touching peritoneum?
Suprapubic region
*Inferior aspects of pelvic organs not touching the peritoneum e.g. cervix and superior vagina: Which type of nerves are these supplied by, and which fibres do these follow and at which level do they enter the spinal cord?
Visceral afferents (as pelvic) which run alongside parasympathetic fibres to S2, 3, 4.
Where is the pain perceived with insult involving pelvic organs not touching peritoneum?
Perineum (S2, 3, 4 dermatome)
*Which type of nerves are structures below the elevator ani (e.g. inferior vagina, perineal muscles) supplied by, and which fibres do these follow and at which level do they enter the spinal cord?
Somatic sensory, which are part of the pudendal nerve entering at levels S2,3,4.
Where is the pain perceived with insult involving structures below the levator ani?
Perineum
Which plexus do fibres from sacral sympathetic trunks form?
Superior hypogastric plexus
What is the inferior hypogastric plexus made up of?
Mixed autonomic - pelvic splanchnic nerves from parasympathetic sacral outflow mix with sympathetics
Pain from the female reproductive system is involved with which 2 most important spinal levels?
T11-L2 (following sympathetic) and S2,3,4 (following parasympathetic)
At what level does the spinal cord form the caudal equine?
L2 vertebra
What anaesthetic options are available during labour?
Spinal anaesthetic, Epidural anaesthetic and pudendal nerve block
At which level is the anaesthetic injection in a spinal and epidural, and how is this level found using surface anatomy?
It is injected at the L3-L4 region, and L4 is found between the superior points of the iliac crest, at the intercristal lines
*In a spinal anaesthetic, what srtuctures does the needle pass through?
- supraspinous ligament (over top of spines)
- interspinous ligament (in between spines)
- ligamentum flavum (connects lamina of adjacent vertebral bodies)
- epidural space (fat and veins)
- dura mater
- arachnoid mater
- finally reaches subarachnoid space
*In an epidural anaesthetic, what srtuctures does the needle pass through?
- supraspinous ligament
- interspinous ligament
- ligamentum flavum
- epidural space (fat and veins)
Which both works and wears off faster, spinal or epidural?
Spinal, as it is directly to the rootlets and cord itself, but is quickly dispersed by the CSF. While epidural has to pass though the fat and veins of the epidural space
Why does vasodilation occur with spinal anaesthetic?
Because all spinal nerves and their named nerves contain sympathetic fibres, so anaesthetising these will block sympathetic tone in arterioles
What are signs that the spinal anaesthetic is working?
Skin of lower limbs looks flushed, warm LLs, reduced sweating (due to blockade of sympathetic tone). Also can ask patient about what they can/can’t feel
When is a pudendal nerve block useful?
- Births where epidural/spinal wasn’t wanted or too late
- episiotomy incision
- forceps use
- perineal stitching post delivery
What is the route of the pudendal nerve?
Exits pelvis vis greater sciatic foramen, passes posterior to lateral sacrospinous lig and then re-enters pelvis/perineum via lesser sciatic foramen. Then travels through pudendal canal (within obturator fascia) to supply structures of perineum
Which pelvic structure is used as a landmark when giving a pudendal nerve block?
Ischial spines
Episiotomy
Incision made before the perineum tears, so that it is a neat, controlled cut. Made Posterolaterally usually to avoid extension into the rectum, and to the fat filled ischioanal fossa instead
How is oogonia formed during development?
around week 6, germ cells from the yolk sac invade the ovaries and proliferate by mitosis to form oogonia (which go on to form oocytes via meiosis)
Atresia of germ cells
Apoptosis-based process causing loss of oogonia dn oocytes, which are then resorbed.
At what phase does meiosis halt in oocytes before birth until puberty?
Prophase I
What happens if the oocyte fails to associate with pregranulosa (follicle) cells?
It will die
What changes happen to the pregranulosa cells after the primordial follicle enters the growth phase to become a primary?
They change from squamous to cuboidal
What defines the primary follicles?
zona granulosa (cuboidal granulosa cells)
What is the theca folliculi and what are its two layers?
Endocrine cells which form layers of the secondary follicles, which is made up of theca interna and externa
What happens to the dominant follicle one day before ovulation?
It will complete meiosis 1, but instead of 2 equal cells its produces one secondary oocyte and one tony polar body that then degenerates
At what phase of meiosis does the secondary oocyte then stop and when does it restart?
It stops at metaphase II and then restarts and becomes a mature oocyte after fertilisation
What does the follicle become after ovulation?
Corpus luteum - with the theca and granulosa cells secreting oestrogen and progesterone. If it doesnt implant, it then becomes the corpus albicans
How does the ovum move down the fallopian tube?
Gentle peristalsis and ciliated epithelium
Which kind of epithelium is in the ampulla of the uterine tube?
Simple columnar with cilia and secretory cells (there are additional layers of smooth muscle underneath)
What is the endometrium of the uterine tubes made up of?
Tubular secretory glands embedded in a connective tissue stroma.
What is the myometrium of the uterine tubes made up of?
3 layers of smooth muscle combined with collagen and elastic tissue
What is the perimetrium of the uterine tubes made up of?
Outer visceral covering of loose connective tissue covered by mesothelium
What is the endometrium subdivided into?
Stratum Functionalis (F) which undergoes monthly growth, degeneration and loss. Stratum Basalis (B) which is a reserve tissue that regenerates the functionalis
What causes the stratum functionalis to shed during mesntruation?
Arterioles undergo constriction, causing ischaemia and tissue breakdown
What is the transition in epithelium that occurs at the cervix?
Stratified squamous ont he vaginal surface, transitioning to simple columnar (common site of dysplasia)
What are the 4 layers of the vagina?
1) Non-keratinised stratified squamous (thicker in reproductive years)
2) lamina propria (connect tissue)
3) Fibromuscular layer
4) Adventitia
Where does vaginal lubrication come from?
Mucous from the cervical glands and fluid from thin walled blood vessels of the lamina propria (no glands in the vagina)
What is the mons pubis?
Skin which contains highly oblique hair follicles, overlying a substantial subcutaneous fat pad, which itself overlies the pubic symphysis.
What do the labia majora contain?
Extensions of mons pubis, similar structure and rich in apocrine sweat glands and sebaceous glands and with small bundles of smooth muscle. Hair follicles on the outer surface, but not the inner.
What is the structure of the labia minora?
Thin skin folds that lack subcutaneous fat and hair follicles, but are rich in vasculature and sebaceous glands that secrete directly onto the surface of the skin.
What is the epithelium transition in the vagina and where does it occur?
Keratinized epithelium extends into the opening of the vagina to the level of the hymen, where there is a transition to non-keratinized stratified squamous epithelium.
Which germ layer does the reproductive system come from?
Mesoderm (intermediate)
Where do the germ cells originate from, and where do they migrate to?
Originate in the wall of the yolk sac, then migrate to the genital ridges
Which gene is required to be expressed for male development to occur?
SRY gene (sex determining region of Y)
Which ducts form the base of the male reproductive system?
Mesonephric duct (stimulated by testosterone from leydig cells, while degeneration of paramesonephric duct is stimulating by Mullerian inhibiting substance from sertoli cells)
Which ducts form the base of the female reproductive system?
Paramesonephric duct
Which structure controls the descent of the testes?
Gubernaculum (ligamentous structure)
