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
What is the nerve supply to the body and fundus of uterus?
Sympathetics to reach spinal cord at T10/11 to L2
What is the nerve supply to the cervix?
Parasymp pelvic splanchnic nerves
Whatsupples the inferior vagina?
Pudendal nerve
What spinal levels must an epidural block to be effective?
Inserted at L3/4
Must block T10-L1 in 1st stage and extend to S2-5 in 2nd stage
At what vertebral level are the iliac crests?
L4
What is the scrotum?
Cutaneous ac divided in 2 by a fibromuscular septum
What makes up the wall of the scrotum?
Hair beating skin
Dartos muscle
What is the normal length and volume of the testicle?
5cm in length
12-25 ml
What can cause a reduced testicular volume?
Klinefelter’s syndrome
Post chemo
Post-orchitis
Where does the epididymis lie in respect to the testis?
Posterolateral border
What are the testis encapsulated within?
Tough fibrous capsule; tunica albuginea (protective and helps with transport of sperm)
What is the tunica vaginalis?
Double layer of peritoneum that encloses the testes and epididymis within scrotum
What is a hydrocele?
Collection of fluid between parietal and visceral layers of tunica vaginalis
What arises from the inferior pole of the testis?
The tail of epididymis becomes vas deferens
Where does the vas lie in respect to the testes?
Continuous with tail of epididymis
Lies medial to epididymis on posterior aspect of testis
Describe the route of the vas
Ascends within the scrotum
Passes through the spermatic cord to enter inguinal canal through superficial inguinal ring in external oblique
Passess through deep inguinal ring, immediately lateral to the inferior epigastric artery to enter abdomen
Passess above and medial to ureter as descends into pelvis to meet seminal vesicle
Joins duct from seminal vesicle to form ejaculatory duct
What is the arterial supply of the vas?
Artery to the vas; derived from the superior vesical artery
What is the location of the seminal vesicles?
Posterior to bladder
What is the location of the prostate gland?
Base of bladder around urethra, rests on the urogenital diaphragm
Prostatic urethra has a midline, longitudinal ridge posteriorly and a urethral crest
What is the arterial supply and venous drainage of the prostate?
Branches from inferior vesical artery
Drained by a plexus of prostatic veins to the internal iliac vein
Function of epididymis and vas?
Exit route from testes to urethra
Concentration and storage of sperm
Site for sperm maturation
Function of seminal vesicles?
Produce semen into ejaculatory duct
Supplies fructose
Prostaglandins (motility)
Fibrinogen (clot precursor)
Function of prostate gland?
Produces alkaline fluid to neutralize vaginal acidity
Clotting enzyme to clot semen within female
Function of bulbourethral glands?
Secretes mucus to act as lubricant
What muscle covers the corpus spongiosum?
Bulbospongiosus
What muscle covers the corpus cavernosum?
Ischiocavernosum
Describe the expression “point and shoot” in terms of erection and ejaculation?
Point; parasymp control that blocks symp vasoconstriction and allows for increased blood flow in erection
Shoot; symp control of muscles involved in ejaculation
At what vertebral levels do the testicular and ovarian arteries arise from?
L2
What autonomic nerves do the testicular and ovaries being with them?
T10-T11 (also supply of abdominal skin at umbilicus)
What is the drainage of the testicular veins?
Right -> IVC
Left -> left renal vein
What is a varicocele?
Veins around testes become distended and elongated
Most common on left, as the vein joins higher pressure left renal vein
What is the lymph drainage of the testes and ovaries?
Para-aortic nodes
If testicular malignancies spread locally to scrotum -> superficial inguinal nodes
At what gestation can the uterine fundus be palpated?
12 weeks
Where does the inferior epigastric artery run?
Branch of external iliac
Ascends from just superior to the inguinal ligament (medial to deep inguinal ring) to run in a medial direction behind rectus muscle
Which costal cartilages does the rectus abdominis insert onto?
5,6,7
Describe the uterine fundus as you move through pregnancy?
Palpable by week 12
At umbilicus at week 20
Grows 1cm per week to reach xiphisternum at around 36 weeks
What structure does a midline vertical incision go through?
Linea alba; avascular, skirts around umbilicus
How can damage to the bladder by minimized in a c/s?
Catheterisation before to reduce size
Surgical care to identify and dissect the loose visceral peritoneum in lower segment of uterus
Bladder is pushed down anterior to uterus towards vagina
Why is it important to suture the rectus sheath on closure of anterior abdominal wall?
Reduce risk of wound hernia formation
How can the inferior epigastric artery be avoided in surgical incisions?
Immediately medial to deep inguinal ring at midpoint of inguinal ligament
Superior to femoral pulse felt at mid-inguinal point
What is the neurovascular supply to the abdominal wall musculature?
Intercostal bundles between 7-12, subcostal bundle inferior to rib 12 and L1 spinal nerve
