Anatomy of Labour Flashcards
Bony pelvis consists of? (4)
2 hip bones,
sacrum,
coccyx
Each hip bone consists of a fusion of what? (3)
ilium,
ischium,
pubis
Pelvic inlet made up of (4)
sacral promontory,
ilium,
superior pubic ramus,
pubic symphysis
Pelvic outlet made up of? (5)
pubic symphysis, ischiopubic rams, ischial tuberosities, sacrotuberous ligaments, coccyx
Pelvic cavity lies between?
Pelvic inlet and pelvic floor
Inguinal ligament attached between?
ASIS and pubic tubercle
Ischial spines are palpable on vaginal examination at approx what positions on clock?
4 and 8 o’ clock
What types of joints are the hip joints?
synovial
What type of joint is pubic symphysis?
secondary cartilaginous
Ligaments tighten during later pregnancy. T/F?
False - relax
What is a straddle injury to pelvis?
All four pubic rami fractured
What arteries and what veins and what nerves are at risk of life threatening haemorrhage in serious pelvic damage?
common iliac artery,
common iliac vein,
sacral nerves/plexus
What 3 adaptations of female pelvis make it better for childbirth than males?
AP and transverse diameters of female pelvis are larger at both pelvic inlet and outlet,
subpubic angle and pubic arch is wider,
pelvic cavity is shallower
What is moulding in childbirth?
movement of one bone over another to allow the foetal head to pass through the pelvis
What outlines the vertex of the foetal skull?
area outlined by the anterior and posterior fontanelles and the parietal eminences - basically a diamond shape each point at fontanelle at eminence
Which is longer on foetal head - occipitofrontal diameter or biparietal diameter?
occipitofrontal diameter longer i.e. babies head is longer than it is wide
At the pelvic inlet, which is wider - the transverse diameter or AP diameter?
transverse diameter wider
What is the station in labour? What do negative and positive stations mean?
Distance of foetal head from the ischial spines,
negative station means head is superior to spines,
positive station means head is inferior
What should the foetal head do and what position should it be in as it descends through the foetal cavity?
It should rotate and be in a flexed position (chin on chest)
At the pelvic outlet, which is wider - the transverse diameter or AP diameter?
AP diameter is wider
What position should foetal head be in during final part of delivery when exiting pelvic cavity?
Should be in extension
At pelvic inlet foetal head should be?
Transverse
While descending pelvic cavity foetal head should be?
rotating and flexed
At pelvic outlet foetal head should be?
OA and extend
What rotation occurs once babies head as been delivered?
rotation so that the shoulders and rest of baby is delivered
Repro system motor function? (3)
uterine cramping uterine menstruation,
contraction during Labour,
pelvic floor muscle contraction e.g. during sneezing
What type nerves responsible for uterine cramping?
hormonal - sympathetic and parasympathetic
What type of nerves responsible for uterine contraction during labour?
hormonal - sympathetic and parasympathetic
What type of nerves responsible for pelvic floor muscle contraction e.g. during sneezing?
somatic motor
What type of nerves transfer pain from annexe and uterus?
visceral afferents
What type of nerves transfer pain from vagina?
pelvic part visceral afferents and perineum somatic sensory
What type of nerves transfer pain from perineum?
somatic sensory
In terms of visceral afferents transferring signals from superior aspect of pelvic organs AKA touching the peritoneum, what fibres do they run alongside, what spinal cord levels do they enter and where do we perceive pain?
run alongside sympathetic fibres,
enter spinal cord between T11-L2,
pain is perceived as suprapubic
In terms of visceral afferents transferring signals from inferior aspect of pelvic organs AKA NOT touching the peritoneum, what fibres do they run alongside, what spinal cord levels do they enter and where do we perceive pain?
run alongside parasympathetic fibres,
enter spinal cord S2, S3, S4,
pain perceived in S2, S3, S4 dermatome (perineum)
In terms of visceral afferents from structures crossing from pelvis to perineum ABOVE the elevator ani (e.g. urethra, vagina), what fibres do they run alongside, what spinal cord levels do they enter?
parasympathetic,
enter spinal cord at levels S2, S3, S4
In terms of somatic sensory nerves from structures crossing from pelvis to perineum BELOW the levator ani (e.g. urethra, vagina), what fibres do they run alongside, what spinal cord levels do they enter and where do we perceive pain?
travel in pudendal nerve,
enter spinal cord at levels S2, S3 and S4,
pain perceived as localised pain within perineum
Sympathetic nerves come from sacral sympathetic trunks that existed spinal cord at what levels? What do these nerves form in the pelvis?
T11-L2,
form the superior hypogastric plexus which sends down fibres pelvis and perineum
Parasympathetics exit spinal cord as pelvic splanchnic nerves. Where do parasympathetics from sacral outflow (2,3,4) mix with sympathetics?
in the inferior hypogastric plexus ,
Which organs touch the peritoneum and so pain travels in visceral afferents back through to T11-L2?
uterine tubes,
uterus,
ovaries
Which organs DON’T touch the peritoneum and so pain travels in visceral afferents back through to S2-S4?
cervix and superior vagina
What 3 types of anaesthesia can be given during labour?
Spinal anaesthetic,
epidural,
pudendal nerve block
What vertebral levels spinal and epidural anaesthetic injected into? Why? (2)
L3-L4 (L5) region because spinal cord becomes caudal equine at L2 and subarachnoid space ends at S2
What layers does needle pass through in epidural?
supraspinous ligament,
interspinous ligament,
ligamentum flavus,
epidural space
What layers does needle pass through in spinal?
supraspinous ligament, interspinous ligament, ligamentum flavus, epidural space, dura mater, arachnoid matter into subarachnoid space
Explain the physiology behind spinal anaesthetic leading to HYPOTENSION?
all spinal nerves contain sympathetic fibres, sympathetic fibres supply all arterioles, sympathetic tone to all lower limb arterioles is blocked by spinal and so that leads to vasodilation -> Hypotension!!
Below L2, sympathetic ganglia receive fibres from where?
receive fibres via sympathetic chain which then connect with lumbar, sacral and coccygeal spinal nerves
Pudendal nerve nerve roots?
S2, S3, S4
Pathway of pudendal nerve from S2, S3, S4?
exits pelvis via greater sciatic foramen,
passes posterior to sacrospinous ligament,
re-enters pelvis/perineum via lesser sciatic foramen,
travels in pudendal canal and branches go to perineum
How is pudendal nerve block administered?
Fingers in vagina, palpate for ischial spine and pass needle through skin or vagina and aim for slightly medial to ischial spine
What is pudendal nerve block commonly used for? (4)
forceps delivery,
painful vaginal delivery,
episiotomy incision,
perineal suturing post delivery
What can happen to pudendal nerve fibres during labour?
pudendal nerve can be stretched
1st - 4th degree tears involve?
1st - skin,
2nd - perineal muscles,
3rd - partial anal sphincter involved,
4th - complete tearing to anal sphincter including bowel lining
What is purpose of episiotomy?
preventing tears of fibres of levator ani or external anal sphincter
What is most common episiotomy incision direction?
posterolateral
