Week 3 - Anatomy of Anaesthesia Flashcards
What are some motor functions of the female reproductive system?
Uterine contraction, uterine cramping, pelvic floor muscle contraction
What type of nerve fibres are responsible for motor control to the uterus e.g. contracting and cramping? This is under the influence of what?
Autonomics (sympathetic/parasympathetic), under hormonal control
What type of nerve fibres are responsible for contraction of muscles of the pelvic floor?
Somatic motor
What type of nerve fibres are responsible for sensation from the adnexae (ovaries and Fallopian tubes)?
Visceral afferents
What type of nerve fibres are responsible for sensation from the uterus?
Visceral afferents
What type of nerve fibres are responsible for sensation from the pelvic part of the vagina?
Visceral afferents
What type of nerve fibres are responsible for sensation from the perineal part of the vagina?
Somatic sensory
What type of nerve fibres are responsible for sensation from the perineum?
Somatic sensory
What structure is responsible for dividing the pelvis and perineum?
Levator ani muscle
What is the a) motor supply and b) sensory supply to a structure in the pelvis (i.e. body cavity)?
a) Autonomics b) Visceral afferents
What is the a) motor supply and b) sensory supply to a structure in the perineum (i.e. body wall)?
a) Somatic motor b) Somatic sensory
The visceral afferents which supply the superior aspect of organs of the pelvis (which are touching the peritoneum) travel alongside which other nerve fibres?
Sympathetics (along periarterial plexuses)
The visceral afferents which supply the superior aspect of the organs of the pelvis (which are touching the peritoneum) travel alongside sympathetic fibres to enter the spinal cord at which level?
Between T11 and L2 (thoracolumbar outflow)
Pain from the superior aspect of pelvic organs which are touching the peritoneum is perceived where?
Suprapubic
The visceral afferents which supply the inferior aspect of organs of the pelvis (which are not touching the peritoneum) travel alongside which other nerve fibres?
Parasympathetics
The visceral afferents which supply the inferior aspect of the organs of the pelvis (which are not touching the peritoneum) travel alongside parasympathetic fibres to enter the spinal cord at which level?
S2, 3, 4 (craniosacral outflow)
Pain from the inferior aspect of pelvic organs which are not touching the peritoneum is perceived where?
S2, 3, 4 dermatomes (posterior thigh and saddle area of perineum)
Describe how pain is sensed in the pelvic part of structures which pass through from pelvis to perineum (i.e. above levator ani)?
Same as for the inferior aspect of pelvic organs - visceral afferents which travel to the spinal cord with parasympathetics
Describe how pain is sensed in the perineal part of structures which pass through from pelvis to perineum (i.e. below levator ani)?
Somatic sensory via the pudendal nerve
The somatic sensory fibres which supply the structures below the levator ani enter the spinal cord at which level?
S2, 3, 4
Pain from structures below the levator ani, sensed by the pudendal nerve, is localised where?
Within the perineum
Both parasympathetics (and the visceral afferents that run along them) and somatic sensory fibres both travel to S2, 3, 4. Do they travel along the same path?
No, they follow different paths
What are the structures which are supplied by visceral afferents that travel back to T11-L2 in the spinal cord with sympathetics?
Uterus, ovaries and uterine tubes
What are the structures which are supplied by visceral afferents that travel back to S2-S4 in the spinal cord with parasympathetics?
Cervix and superior vagina
What are the structures which are supplied by somatic sensation via the pudendal nerve?
Organs/structures within the perineum - inferior vagina, perineal muscle, glands and skin
What are the two important spinal cord levels in the female reproductive system?
T11-L2 and S2-S4
Where does sympathetic outflow originate?
Autonomic centres in the brain
Where does sympathetic outflow leave the spinal cord?
T1-L2
What happens to sympathetic fibres once they leave the spinal cord?
Travel to sympathetic chains which run the entire length of the vertebral column, and synapse and pass into all spinal nerves (anterior and posterior rami)
What type of nerve fibres does the pudendal nerve carry?
Somatic sensory and motor and sympathetic
What is the pudendal nerve a branch of? What are its nerve roots?
A branch of the sacral plexus, S2, 3, 4
Describe the course of the pudendal nerve?
Exits the pelvis via the greater sciatic foramen, passes posterior to the sacrospinous ligament before re-entering the pelvis/perineum via the lesser sciatic foramen. It then travels in the pudendal canal (a passageway within obturator fascia)
The pudendal nerve travels alongside which other structures in the pudendal canal?
Internal pudendal artery and vein, and nerve to obturator internus
What does the pudendal nerve branch into?
Superficial and deep perineal nerves
What does the superficial perineal nerve supply?
External genitalia
What does the deep perineal nerve supply?
Muscles of the perineum
What are some procedures that a pudendal nerve block may be useful for?
Episiotomy incision, forceps delivery, perineal stitching post-delivery
During labour, the branches of the pudendal nerve can be stretched and fibres within which muscles can be torn?
Levator ani (puborectalis especially) and/or external anal sphincter
What can be the result of tearing muscle fibres in the levator ani/external anal sphincter?
Both of the muscles can be weakened which can lead to a weakened pelvic floor/faecal incontinenece
What happens in an episiotomy?
A posterolateral incision is made into the fat filled ischioanal fossa
Why is it preferred to make a posterolateral episiotomy incision rather than a median one?
It avoids the incision extending into the rectum and disrupting the anal sphincter/perineal body
How is a spinal anaesthetic administered?
Lumbar puncture
Where is anaesthetised in a spinal anaesthetic?
From the waist down - intra and sub peritoneal, plus somatic area innervated by the pudendal nerve
Which anaesthetic causes women to be unable to feel contractions?
Spinal
Where is anaesthetised in a caudal epidural anaesthetic?
Sub-peritoneal area and somatic area innervated by the pudendal nerve
Where is anaesthetised by a pudendal nerve block?
The area innervated by the pudendal nerve only (i.e. the perineum)
Where does the spinal cord become the cauda equina?
L2
Where does the subarachnoid space end?
S2
Where is spinal/epidural anaesthetic administered?
L3/4
Which layers do you need to pass through to administer a spinal anaesthetic?
Supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space, dura mater, arachnoid mater, SUBARACHNOID SPACE
Once a spinal anaesthetic has been administered, how should the patient be positioned?
At an incline to make sure the anaesthesia stays inferiorly
If a patient lies down following a spinal anaesthetic, what symptom can this cause?
Headache due to raised ICP
What layers do you need to pass through to administer an epidural?
Supraspinous ligament, interspinous ligament, ligamentum flavum, EPIDURAL SPACE
What is found in the epidural space?
Fat and veins
Because all spinal nerves contain sympathetics, performing a spinal anaesthetic will have what impact on the lower limb?
Vasodilation - flushed skin, warm limbs, reduced sweating
Because all spinal nerves contain sympathetics, you should be aware of what sign when performing a spinal anaesthetic?
Hypotension
The pudendal nerve crosses what aspect of the sacrospinous ligament?
Lateral
What structures can be used as a landmark to administer a pudendal nerve block?
Ischial spines
