Anatomy Flashcards
What does the bony pelvis consist of?
2 hip bones
Sacrum
Coccyx
What is each hip bone a fusion of?
Ilium
Ischium
Pubis
What is the ischiopubic ramus made up of?
Both ischium and pubis
What ligament attaches to the pubic tubercle?
Inguinal ligament
Where does the inguinal ligament attach between?
The ASIS and pubic tubercle
Where are the ischial spines palpable?
On vaginal examination, at about a finger breadth into the vagina (approx. 4 and 8oclock positions)-also pudendal nerve
Where are the attachments of the sacrospinous ligament?
Sacrum and ischial spine
Where are the attachments of the sacrotuberous ligament?
Sacrum and ischial tuberosity
What is the function of the sacrotuberous and sacrospinous ligaments?
Ensure inferior sacrum is not pushed superiorly when weight is suddenly transferred vertically through vertebral column (eg. jumping, later pregnancy)
What 2 foraminae do the sacrotuberous and sacrospinous ligaments form?
Greater and lesser sciatic foraminae
What forms the pelvic inlet?
Sacral promontory
Ilium
Superior pubic ramus
Pubic symphysis
What forms the pelvic outlet?
Pubic symphysis Ischiopubic ramus Ischial tuberosities Sacrootuberous ligaments Coccyx
What part of the pelvic cavity does levator ani form?
Pelvic floor- musculofascial inferior part
What are the functions of the pelvis?
Upper body support
Transference of weight from vertebral column to femurs
Attachment for muscles of location and abdo wall
Attachment for external genitalia
Protection of pelvic organs and associated structures
Passage for childbirth
What are the key differences between the female and male pelvis?
AP and transverse diameters are larger
Subpubic angle is wider
Pelvic cavity is shallower
What is moulding?
The movement of one bone over another to allow the foetal head to pass through the pelvis during labour
Moulding is allowed due to the presence of what?
Sutures and fontanelles
What is the vertex?
An area of foetal skull- outlined by the anterior and posterior fontanelles and the parietal eminences
Which is longer-the occipofrontal diameter or the biparietal?
Occipitofrontal
At the pelvic inlet, is the transverse of AP diameter wider?
Transverse
The foetus should enter the pelvic cavity facing what direction?
Either right or left (transverse)
What is the station?
The distance of the foetal head from the ischial spines
-ve means head is superior, +ve means head is inferior
What should the foetal head do whilst descending through the pelvic cavity?
Rotate
Be in a flexed position e.g. chin on chest
At the pelvic outlet is the AP or transverse diameter wider?
AP
In what position should the baby ideally leave the pelvic cavity?
Occipitoanterior position
During delivery should the foetal head be in flexion or extension?
Extension
What happens once baby’s head is delivered?
There is a further rotation so that the shoulders and rest of the baby can then be delivered
What parts of the female reproductive system are within the pelvic cavity?
Ovaries
Uterine tubes
Uterus
Superior part of vagina
What parts of the female reproductive system are within the perineum?
Inferior part of vagina Perineal muscles Bartholin's glands Clitoris Labia
Fluid collection in the pouch of Douglas can be drained via a needle passed through what in females?
Posterior fornix of the vagina
What is the broad ligament of the uterus?
Double layer of the peritoneum
Where does the broad ligament extend between?
The uterus and the lateral walls and floor of the pelvis
What is the function of the broad ligament?
Helps maintain the uterus in its correct midline position
What is contained within the broad ligament?
The uterine tubes and the proximal part of the round ligament
What is the round ligament?
An embryological remnant
Where does the round ligament attach?
The lateral aspect of the uterus, and passes through the deep inguinal ring to attach to the superficial tissue of the female perineum
Where does implantation of the zygote occur?
Body of the uterus
What 3 layers of support hold thee uterus in place?
Number of strong ligaments e.g. uterosacral ligaments
Endopelvic fascia
Pelvic floor muscles e.g. levator ani
What are the two most common positions of the uterus?
Anteverted
Anteflexed
What are some normal variations in position of the uterus?
Retroverted
Retroflexed
What state are the walls of the vagina usually in?
Collapsed
What zone is sampled during a cervical smear?
Squamo columnar junction (transformation zone)
Do the uterine tubes usually lie symmetrically?
No
What is a bilateral salpingo-oophorectomy?
Removal of both uterine tubes and ovaries
What is a unilateral salpingectomy?
Removal of one of the uterine tubes
Where are the fimbriae open?
Into the peritoneal cavity
What size and shape are the ovaries?
Almond like
What do the ovaries secrete?
Oestrogen and progesterone in response to FSH and LH
Where do ovaries develop?
Posterior abdominal wall and move onto the lateral wall of pelvis, then onto the round ligament
Where is the ovum released?
Directly into the peritoneal cavity to be picked up by the fimbriae of the uterine tube
What is the fornix?
Space around the cervix
What are the 4 parts of the fornix?
Anterior
Posterior
2 Lateral
What is the perineum divided into?
Superficial and deep pouches
What is the levator ani muscle made up of?
Number of small muscles
Skeletal
What does levator ani form?
The majority of the pelvic diaphragm with its fascial coverings
What does levator ani provide?
Continual support for the pelvic organs
Describe the contractions of levator ani
Tonic contraction
Reflexively contracts further during situations of increased intra-abdominal pressure
What can be a factor in the development of prolapse of the pelvic organs?
Weakness of levator ani
What is the nervous supply to levator ani?
Nerve to levator ani
S3,4,5 sacral plexus
What nerve supplies the perineal muscles?
Pudendal nerve
What is the perineal body?
Bundle of collagenous and elastic tissue into which the perineal muscles attach
What is the perineal body important for?
Pelvic floor strength
Where is the perineal body located?
In perineum, just deep to skin
Where are the Bartholins glands located?
Perineum, just lateral to vaginal orifice on both sides
Where does the bed of breast extend from?
Ribs 2-6
Lateral border of sternum to mid-axillary line
Where do breasts lie on?
Deep fascia covering pec major and serratus anterior
What lies between the fascia and breast?
Retromammary space
How are breasts attached to skin?
Firmly via suspensory ligaments
Where does most lymph from the breast drain to?
Ipsilateral axillary nodes, then to supraclavicular nodes
Where can lymph from inner breast quadrants drain to?
Ipsilateral and contralateral lymph nodes
Where can lymph from the lower inner breast quadrant drain to?
Abdominal lymph nodes
What is the axilla?
Pyramidal pathway between arm and chest
What does the axilla contain?
Brachial plexus branches
Axillary artery (& branches) and axillary vein (& tributaries)
Axillary lymph nodes
All embedded in axillary fat
What do breast surgeons use to describe the extent of axillary node clearance?
‘Levels’ of axillary nodes
What are the levels of the axillary lymph nodes?
Level I – inferior and lateral to pectoralis minor
Level II – deep to pectoralis minor
Level III – superior and medial to pectoralis minor
What is the adnexae?
Ovaries and fallopian tubes
What nerve fibres are involved in the pelvis?
Sympathetic
Parasympathetic
Visceral afferent
What nerve fibres are involved in the perineum?
Somatic motor
Somatic sensory
What are the nerve fibres associated with uterine cramping?
Sympa/parasympathetic (hormonal)
What are the nerve fibres associated with uterine contraction?
Sympa/parasympathetic (hormonal)
What are the nerve fibres associated with pelvic floor muscle contraction?
Somatic motor
What are the nerve fibres associated with pain from adnexae?
Visceral afferents
What are the nerve fibres associated with pain from uterus?
Visceral afferents
What are the nerve fibres associated with pain from vagina?
Visceral afferents (pelvic part) Somatic sensory (perineum)
What are the nerve fibres associated with pain from the perineum?
Somatic sensory
Describe the pain sensation from the superior aspect of pelvic organs/touching the peritoneum
Visceral afferents
Run alongside sympathetic fibres
T11-L2
Pain perceived as suprapubic
Describe the pain sensation from the inferior aspect of pelvic organs/not touching the peritoneum
Visceral afferents
Run alongside parasympathetic fibres
S2,3,4
Pain perceived in S2,S3,S4 dermatome (perineum)
Describe the pain sensation from structures crossing from pelvis to perineum e.g. urethra, vagina (above levator ani)
Visceral afferents
Parasympathetic
S2,3,4
Describe the pain sensation from structures crossing from pelvis to perineum e.g. urethra, vagina (below levator ani)
Somatic sensory
Pudendal nerve
S2,3,4-localised pain within perineum
At what level does spinal cord become cauda equina?
L2 vertebra
At what level does the SA space end?
S2
Is there a likely risk of infection in spinal/epidural anaesthetic?
No
What does the needle pass through in a spinal anaesthetic?
Supraspinous ligament Interspinous ligament Ligamental flavum Epidural space (fat + veins) Dura mater Arachnoid mater SA space
What does the needle pass through in an epidural anaesthetic?
Supraspinous ligament
Interspinous ligament
Ligamental flavum
Epidural space (fat + veins)
What happens to the sympathetic outflow below L2 level?
Sympathetic ganglia receive fibres from L2 level via sympathetic chain
Distribute them via connections with lumbar, sacral and coccygeal spinal nerves
What does spinal anaesthetic effect?
All spinal nerves and their named nerves (containing sympathetic fibres) below level of injection
What does the blockade of sympathetic tone to all arterioles in lower limb result in?
Vasodilation: skin of lower limbs lookds flushed Warm lower limbs Reduced sweating All signs that spinal anaesthetic is working
What must be watched for in spinal anaesthetic?
Hypotension
What does the pudendal nerve supply?
Somatic motor and sensory structures of the perineum
Where does the pudendal nerve originate?
Branch of sacral plexus : S2,3,4
What does a pudendal nerve block do?
Anaesthetise majority of perineum
What is a pudendal nerve block useful for?
Episiotomy incision
Forcepss use
Perineal stitching post delivery
Describe the course of the pudendal nerve
Exits pelvis via greater sciatic foramen
Passes posterior to sacrospinous ligament
Re-enters pelvis/perineum via lesser sciatic foramen
Travels in pudendal canal (passageway within obturator fascia) within internal pudendal artery and vein, and nerve to obturatory internus
Branches to supply structures of perineum
What can be used as a landmark to administer block?
Ischial spine
What can cause pudendal nerve of sphincter damage during labour?
Branches of pudendal nerve can be stretched with resultant stretch of nerve fibres
Fibres within the levator ani (puborectalis) or external anal sphincter muscle could be torn and as a result, the muscle weakened from 1st to 3rd degree
Weakened pelvic floor and faecal incontinence could result
What is an episiotomy?
Posterolateral (mediolateral) incision
Made into the relatively safe fat filled ischioanal fossa and avoids incision extending into rectum
What are the layers of the anterolateral abdominal wall?
Skin
Superficial Fascia
Anterior: Rectus Sheath, Rectus Abdominis
Lateral: External oblique, Internal oblique, Transversus Abdominis
What are the attachments of the external obliques?
Between lower ribs and iliac crest, pubic tubercle and linea alba
What is the linea alba?
Midline interweaving of aponeuroses of anterolateral abdominal wall muscles
The fibres of external obliques run in the same direction as what?
External intercostals
What are the attachments of the internal obliques?
Between lower ribs, thoracolumbar fascia, iliac crest and linea alba
The fibres of internal obliques run in the same direction as what?
Internal intercostals
Where does transversus abdominis attach between?
Lower ribs, thoracolumbar fascia, iliac crest and linea alba
What do the tendinous intersections of the rectus abdominis do?
Divide each rectus abdominis into 3 or 4 smaller muscles to improve mechanical efficiency
Where does the linea alba run from?
Xiphoid process to the pubic symphysis
What is the rectus sheath?
Combined aponeuroses of anterolateral abdominal wall muscles surrounding rectus abdominis muscles
When undertaking a suprapublic incision, such as in lower segment C-section, what is cut from the anterior and posterior rectus sheath?
Anterior rectus sheath only
Describe the nerve supply to the anterolateral abdominal wall
Enter from lateral direction 7-11th intercostal nerves: become thoracoabdominal nerves Subcostal (T12) Iliohypogastric (L1) Iliolingual (L1)
Where does the nerve supply to the anterolateral abdominal wall travel?
In plane between internal oblique and transversus abdominis
What is the blood supply to the anterior abdominal wall?
Superior epigastric arteries
Inferior epigastric arteries
Describe the superior epigastric arteries
Continuation of internal thoracic
Emerges at superior aspect of abdo wall
Lies posterior to rectus abdominis
Describe the inferior epigastric arteries
Branch of external iliac artery
Emerges at inferior aspect of abdo wall
Lies posterior to rectus abdominis
What is the blood supply to the lateral abdominal wall?
Intercostal and subcostal arteries
Describe the intercostal and subcostal arteries
Continuations of posterior intercostal arteries
Emerge at lateral aspect
How should you aim to minimise traumatic injury to muscle fibres when making an incision?
Incise in same direction as muscle fibre
When incising muscle, what should be aimed for?
Minimise traumatic injury to muscle fibres
Avoid damaging nerves
Avoid interrupting blood supply
What is done to the rectus muscles in a LSCS incision?
Separated from each other in a lateral direction, moving them toward their nerve supply
What layers are cut/moved in an LSCS?
Skin and fascia
(anterior) Rectus sheath
Rectus abdominis – separate the muscles laterally
Fascia and peritoneum
Retract bladder (a urinary catheter is usually already inserted)
Uterine wall
Amniotic sac
What layers need stitched closed in an LSCS?
Uterine wall with visceral peritoneum
Rectus sheath
(Fascial layer if increased BMI)
Skin
What layers are opened in a laparotomy?
Skin and fascia
Linea alba (a structure rather than a layer)
Peritoneum
What layers need stitched closed in a laparotomy?
Peritoneum & Linea alba
Fascia (if increased BMI)
Skin
What complications can occur in a laparotomy as it is relatively bloodless?
Can mean that healing is not as good
Increases the chance of wound complications e.g. dehiscence, incisional hernia
What must be avoided if a lateral port is required?
Inferior epigastric artery
In a laparotomy how can the position of the uterus be manipulated?
By grasping the cervix with forceps inserted through the vagina
What is the route of the inferior epigastric artery?
Branch of external iliac artery
Emerges just medial to the deep inguinal ring- ring located halfway between ASIS and pubic tubercle
Then passes in a superomedial direction posterior to the rectus abdominis
What is an abdominal hysterectomy?
Removal of the uterus via an incision in the abdominal wall (A)
Often same incision as for LSCS
What is a vaginal hysterectomy?
Removal of uterus via the vagina
How can the ureter be differentiated from the uterine artery in a hysterectomy to avoid damaging it?
Ureter passes inferior to artery (water under bridge)
Ureter will vermiculate when touched
What is the pelvic floor made up of?
Pelvic diaphragm
Muscles of perineal pouches
Perineal membrane
What makes up the pelvic diaphragm?
Levator Ani
Coccygeus
What does levator ani attach?
Pubic bones, ischial spines and tendinous arch of levator ani
Perineal body, coccyx and walls of organs in midline
What are the 3 parts of levator ani?
Puborectalis
Pubococcygeus
Iliococcygeus
What innervates levator ani?
Pudendal nerve and nerve to levator ani
Where does the deep perineal pouch lie?
Below the fascia covering the inferior aspect of the pelvic diaphragm
Above the perineal membrane
What is contained within the deep perineal pouch?
Part of urethra (and vagina in females)
Bulbourethral glands in males
NVB for penis/clitoris
Extensions of ischioanal fat pads and muscles
Where does the perineal membrane attach?
Laterally to the sides of the pubic arch, closing the urogenital triangle
Where is the superficial perineal pouch in males?
Below the perineal membrane
What is contained within the superficial perineal pouch in males?
Root of penis:
-Bulb- corpus spongiosum, crura-corpus cavernosum
-Associated muscles- bulbospongiosus and ischiocavernosus
Proximal spongy urethra
Superficial transverse perineal muscle
Branches of internal pudendal vessels and pudendal nerve
What is contained within the superficial perineal pouch in females?
Female erectile tissue and associated muscle:
-Clitoris and crura-corpus cavernosum
-Bulbs of vestibule-paired
-Associated muscles- bulbospongiosus and ischiocavernosus
Greater vestibular glands
Superficial transverse perineal muscle
Branches of internal pudendal vessels and pudendal nerve
What are the functions of the pelvic floor?
Support to pelvic organs- normally tonically contracted, actively contracts in coughing etc
Helps maintain continence:
-urinary (external urethral sphincter, compressor urethrae, levator ani)
-faecal (tonic contraction of puborectalis bends anorectum anteriorly, active contraction maintains continence after rectal filling)
What can cause injury to pelvic floor?
Pregnancy Childbirth Chronic constipation Obesity Heavy lifting Chronic cough or sneeze Previous injury to pelvic/pelvic floor Menopause
What does continence depend on?
Urinary bladder neck support
External urethral sphincter
Smooth muscle in urethral wall
Describe vaginal prolapse
Herniation of urethra, bladder, rectum or rectouterine pouch through supporting fascia
Presents as lump in vaginal wall
Can be urethro/cysto/recto/entero-cele
Describe uterine prolapse
Descent of uterus 1st, 2nd, 3rd degree Dragging sensation Feeling of lump Urinary incontinence
Describe sacrospinous fixation
Sutures placed in sacrospinous ligament Just medial to the ischial spine To repair cervical/vault descent Performed vaginally Risk of injury to pudendal NVB and sciatic nerve
Describe incontinence surgery
Trans-obturator approach Mesh through obturator canal Space in obturator foramen for passage of obturator NVB Create a sling around the urethra Incisions through vagina & groin
Where do the majority of arteries of pelvis and perineum arise from, and what are the exceptions?
From internal iliac artery
Exceptions:
Gonadal artery- L2 abdominal aorta
Superior rectal artery- continuation of inferior mesenteric
What is the medial umbilical fold a remnant of?
Umbilical artery
Where are most branches of the arteries in the male perineum from, and what is the exception?
Internal pudendal
Anterior scrotal artery is exception as comes from external iliac
Where do anastomoses occur in the female reproductive system?
Between uterine and ovarian artery, and between uterine and vaginal artery
Where do most pelvic and perineal veins drain to?
Internal iliac vein
Some via superior rectal into hepatic portal system, some via lateral sacral veins into internal vertebral venous plexus
Why does ureter damage occur more on the left than the right?
As the right is constant and usually crosses external iliac, whereas the left is more medial and crosses common iliac
51% of ureter damage occurs lateral to cervix during uterine artery division
What is the lymphatic drainage of the superior pelvic viscera?
External iliac nodes
Common iliac, aortic, thoracic duct, venous system
What is the lymphatic drainage of the inferior pelvic viscera?
Deep perineum
Internal iliac nodes
Common iliac, aortic, thoracic duct, venous system
What is the lymphatic drainage of the superficial perineum?
Superficial inguinal lymph nodes
What is the gonadal lymphatic drainage?
Lumbar (aortic/caval) nodes
