Week 3 and 4 anatomy tutorials Flashcards
Where does the anterior fontanelle lie?
Between frontal and parietal bones; remains open until around 18 months of age
Where does the posterior fontanelle lie?
Between 2 parietal and occipital bones; closes at 1 year
What makes up the vertex?
Parietal eminences laterally
Anterior and posterior fontanelles
How can the foetal head be positioned to occipito-anterior whilst in the birth canal?
Manual rotation
Vacuum extraction
Kielland’s rotational forceps
How will the foetal head change position as it descends through the maternal pelvis?
Enters pelvis inset in occipitotransverse position
Rotate to occipitoanterior at pelvic outlet
As it descends beyond ischial spines; the head will extend
Why is OP instead of OA more difficult to labour?
If in OP; head is not well flexed and therefore the presenting diameter is wider resulting in cephalopelvic disproportion
What are the important pelvic landmarks in relation to labour?
ASIS Pubic tubercle Pubic crest Pectineal line Pubic symphysis Ischial tuberosity Ischial spine Sacrotuberous ligament Sacrospinous ligament SI joint
What makes up the pelvic inlet?
Pubic symphysis Along pubic crest Superior pubic ramus Iliopectineal line Sacral promontory
What makes up the pelvic outlet?
Coccyx Sacrospinous and sacrotuberous ligaments Ischial tuberosities Ischiopubic ramus Pubic symphysis
What makes up the posterior half of the perineum?
Ischio-anal region with the anal canal centrally and ischioanal fossa laterally
What makes up the anterior aspect of the perineum?
Urogenital triangle spanned by the perineal membrane
What is the relation of the greater and lesser sciatic foramina to the ischial spines?
Greater superior
Lesser inferior
Where does the perineal membrane attach?
Ischiopubic ramus to spain the subpubic angle
What is the posterior fourchette?
Small, transverse fold where the labia minora meet
This is where the episiotomy begins
What is the course of the pudendal nerve and vessels?
Emerge from pelvis below the piriformis through the greater sciatic foramen
Vessels curve over ischial spine and nerve curves over the spine and sacrospinous ligament immediately medial to artery
NVB enters perineum inferior to the ligament and adjacent to ischial spine
Pass forward in the fasical canal in the ischioanal fossa
How is a pudendal nerve performed?
Ischial spine palpated vaginally
Pudendal nerve is immediately inferior to the tip of the spine
Anaesthetic needle inserted through vaginal wall aimed just below the ischial spine at pudendal nerve
Why must you put your hand below the needle tip hen performing a pudendal nerve block?
Baby’s head tends to be stationed within the lesser pelvis
What does the pudendal nerve supply?
Main motor supply to perineum
Sensory to skin of perineum and external genitalia
Innervation to perineal muscles, external anal sphincter and external urethral sphincter
What will a pudendal nerve block anaesthetise and why is it helpful?
LA to S2-4
Does not block pain from uterus, cervix or superior vagina
Are contractions affected by a pudendal nerve block?
No
Why can the facial nerve be injured by forceps delivery in babies?
Foetal skull has no mastoid processes
Therefore no protection for the facial nerve from the stylomastoid foramen
In what scenario can klumpke’s palsy occur in childbirth?
Arm delivered first, forced abduction putting undue traction on lower trunk of brachial plexus
Loss of function of all small muscles of hand, clawing of fingers and sensory loss on medial aspect of upper limb
In what scenario can erb’s palsy occur in childbirth?
Shoulder dystocia
If head is pulled it may force the shoulder and neck apart putting undue pressure on the upper trunk of brachial plexus
Arm adducted and internally rotated, elbow extended and pronated
Sensory loss to lateral aspect of upper limb
What nerve damage can occur in women during childbirth?
If patient in lithotomy position for too long, neuropraxia of common fibular nerve (foot drop)
When is a spinal anesthetic used?
Emergency c/s
Rapidly blocks nerve roots
SE; post spinal headache, resp arrest
What is the nerve supply to the vulva?
L1 via ilioinguinal supplies anterior labia
Posterior labia supplied by S2,3,4 via pudendal nerve
Therefore L1-S4 musch be anaesthetised