Pelvis Flashcards
Muscles of posterior abdominal wall
Psoas major
Quadratus lumborum
Iliacus
Psoas major - where does the nerves that pass through arise
From the front: genitofemoral N
Lateral: ilioinguinal, iliohypogastric, lat femoral cutaneous & femoral
Medial = obturator & lumbosacral trunk
What emerges from lat aspect of psoas major
Iliohypogastric
Ilioinguinal
Lateral femoral cutaneous n
Femoral N
Action of psoas major
Hip flexor
Lateral flexor of vertebral column
Nerve supply to psoas major
L1-3, mainly L2
Origin & insertion of psoas major
T12-L5 bodies, IVD, transverse processes
Into lesser trochanter
Quadratus lumborum origin & insert
Origin from Transverse process of L5 from strong iliolumbar lig to upper 4 lumbar vertebra and inferior border of 12th rib
What runs behind the lateral arcuate lig
The subcostal neurovascular bundle
Iliacus origin & insert
Upper 2/3rds of iliac fossa to inner lip of iliac crest and Ant sacroiliac lig
Inserts into psoas (lesser trochanter)
Nerve supply of iliacus
Femoral, L2/3
What is the thoracolumbar fascia
Deep investing membrane covering deep muscles of trunk, with 3 layers
Abdominal aorta starts
T12, b/w crura of diaphragm
Abdo aorta ends
L4, divides into 2 common iliac A
What are the branches of the abdo aorta
3 single ventral arteries - coliac, SMA, IMA
Paired branches to viscera
— suprarenal, renal, gonadal
Paired branches to abdo wall
- inferior phrenic, lumbar A
Median sacral A
Where does the renal A commence
L2
How do the subcostal A enter the abdomen
Arise from thoracic aorta
Travel under lateral arcuate lig, over lumbar fascia, behind kidney in neurovascular plane IO and TA
How many lumbar As are there
4 in number
What do the lumbar arteries give off
Posterior and spinal A
Where do common iliac A begin
L4, to the L of midline
What crosses the L common iliac
Ureter
Inferior mesenteric (sup rectal) vessels
Sympathetic contributions to superior hypogastric plexus
What does the external iliac A give off
2 branches - inferior epigastric
Deep circumflex
Then enters inguinal lig = femoral A
IVC starts….
L5, behind R common iliac A
Which aspects of IVC have valves
Only the gonadal V
What does each common iliac vein receive
Iliolumbar V
Lateral sacral V
Median sacral V
What are the tributaries to the IVC
Common iliac V
Lumbar V
Gonadal V
Renal V
Suprarenal V
Subcostal N and journey
T12, from thorax, behind lateral arcuate lig
What are the branches of the lumbar plexus
L1 = ilioinguinal, iliohypogastric
L1,2 = genitofemoral
L2,3 = lateral femoral cutaneous *post div
L2,3,4 = femoral (post)
L2,3,4 = obturator (ant)
iliohypogastric supplies
Skin in upper buttock
Suprapubic skin
Ilioinguinal nerve supply
Ant 1/3rd of scrotum, penis, upper part of groin
Genitofemoral nerve supply
Motor fibres to cremaster m
Sensory fibres to spermatic fascia, tunica, skin on scrotum, mons pubis/labia
Supplies skin over upper part of femoral triangle
Lateral cutaneous nerve of the thigh supply
L2,3
Iliac fascia, parietal peritoneum of iliac fossa
Lateral side of thigh to knee
Femoral N branches
N to pectineus
N to sartoris
N to rectus femoris
N to vatus lateralis, intermedius, medialis
Saphenous n
Saphenous n supply
Skin over subcutaneous surface of tibia
Obturator division
Anterior , posterior (over adductor brevis)
Anterior div of obturator nerve supplies
Adductor brevis
Adductor longus
Gracilis
Medial thigh cutaneously
Post div of obturator nerve supplies
Obturator externus
Adductor magnus
What is the order the vessels in obturator foramen
Nerve
Artery
Vein
SNS to the pelvis
Coeliac plexus
Lumbar trunk
Psns of pelvis
Vagus
Pelvic splanchnic, joins inferior hypogastric plexus
What runs in the white ramus communicans
Sympathetic preganglionic fibres
What runs in the grey ramus communicans
Sympathetic post ganglionic fibres
Posterior relations of kidney
Diaphragm
Quadratus lumborum
Psoas
Transversus abdominis
Subcostal V
Subcostal A
Subcostal N
Iliohypogastric N
Ilioinguinal N
Anterior relations of R kidney
Peritoneum of hepatorenal pouch
2nd part of duodenum
Hepatic flexure
Anterior relations of L kidney
Peritoneum of lesser sac
Peritoneum of greater sac
Body of pancreas, splenic vessels
Splenic flexure
Where does the perinephric fat lie
Outside of renal capsule, surrounded by renal fascia
Blood supply to the kidneys
Renal arteries, L2
Order of vessels at renal hilum
Renal V most anterior
Renal A
Ureter most posterior
Lymph drainage of kidney
Para-aortic nodes at L2
Nerve supply of kidney
Sympathetic preganglionic cells in T12-L1 and they send preganglionic fibres to thoracic and lumbar splanchnic nerves
How long is the ureter
25cm
Narrowest points of ureter
Pelvoureteric junction
Pelvic brim
Vesicoureteric junction
Where does the ureter run
Arise most post structure in renal hilum
Along tips (medially) of transverse processes
Crosses pelvic brim in sacroiliac joints
What crosses the L ureter
Gonadal vessels
L colic vessels
Apex of sigmoid colon
What crosses R ureter
Gonadal vessels
R colic vessels
Ileocolic vessels
Root of mesentry
Blood supply of ureter
Upper - ureteric branch of renal A
Middle - aorta, gonadal, common iliac, internal iliac A
Lower - branches of inferior and superior vesical and uterine arteries
Lymph drainage of ureters
Abdo portion - para-aortic nodes
Pelvic - common iliac, internal iliac LN
Nerve supply of ureter
Sympathetic fibres from t10-l1 via coeliac and hypogastric plexus
PSNS fibres from pelvic splanchnic nerves
Development of ureters
Mesodermal origin
Ureteric buds from caudal end of mesonephric duct
Features of R suprarenal gland
Pyramidal
Lies on diaphragm
Enroaches front of R kidney
Anterior surface overlapped by IVC
In contact with bare area of liver
Features of L suprarenal gland
Crescenteric
Medial border of L kidney to above hilum
Lies on L crus
Where do the suprarenal glands lie
L = L crus
R = on diaphragm
Lymph drainage of suprarenals
Para-aortic nodes
Nerve supply of suprarenals
Myelinated preganglionic sympathetic fibres from splanchnic nerves via coeliac plexus (synapse directly with medullary cells
structure of suprarenal gland
Medulla
Cortex = 3 zones
What do the components of medulla form
Cortex
- zona glomerulosa = aldosterone
- zona fasciculata = cortisol
- zona reticularis = androgen hormones
Medulla
- A, NA, dopamine
Internal iliac artery divisions
Posterior - 3
Anterior - 9
Where does the internal iliac arise
At bifurcation of common iliac, at L4
Branches of the internal iliac a
Post - iliolumbar, lateral sacral, superior gluteal A
Ant
- obturator a, inferior gluteal A, umbilical A
- uterine A, vaginal A, superior vesical A
- inferior vesical, middle rectal, internal pudendal
Posterior divisions of int iliac A
Uterine, umbilical, sup vesical
Inferior gluteal, inf vesical, internal pudendal
Obturator a, middle rectal, vaginal A
Ant divisions of internal iliac A
Iliolumbar
Lateral sacral
Superior gluteal A
Pelvic brim
Pubic crest, pectineal line of pubis, arcuate line of ilium, ala and promontory of sacrum
What angle does the pelvic brim lie at
60 degrees
Sex differences b/w pelvis
Female = broader, slender
Less acute subpubic angle
Less indentation from promontory
Pubic arch is wider
Muscles of the pelvis
Piriformis
Obturator internus
Levator ani
- iliococcygeus
- pubococcygeus
Coccygeus
Piriformis origin and insert
Middle 3 pieces of sacrum to insert sup aspect of greater trochanter
Obturator internus origin and insert
Obturator membrane, bony margins of foramen and ischial tuberosity
Insert with sacrotuberous lig to ischial tuberosity
What makes up the pelvis floor
Iliococcygeus
Pubococcygeus
Where does the iliococcygeus origin
Posterior half of tendinous arch
Pelvic surface of ischial spine
Pubococcygeus components
Puborectalis
Pubourethralis
Pubovaginalis
Nerve supply of levator ani
Sacral plexus branches of S3/4
What makes up levator ani
Pubcoccygeus
Iliococcygeus
Origin of coccygeus
Tip of ischial spine => coccyx and lowest part of sacrum
Nerve supply of coccygeus
Sacral plexus branches S3/4
Blood supply of rectum
Superior rectal A
Middle rectal
Inferior rectal
Median sacral A
Venous return of rectum
Internal rectal plexus and external rectal plexus forms potential site of portosystemic anastomosis
As some into IMV, some into internal pudendal V
Nerve supply of the rectum
Sympathetic - from inferior mesenteric plexus
PSNS - pelvic splanchnics from S2,3,4 via inferior hypogastric plexus (motor to rectal M
Urinary bladder surfaces
Apex
Base
Inferolateral surface
Neck
Superior surface
What attaches to apex of bladder
Urachus => medial umbi lig => median umbi fold
What aspects of bladder are covered by peritoneum
Base (upper portion)
Superior surface
What is the space infront of inferolateral surfaces of bladder
Behind pubic symphysis = retropubic space
What is the lowest part of bladder
Neck
Internal surface of bladder features
Trabeculae
Trigone
What is the trigone
2 ureteral orifice and internal urethral orifice below
Blood supply of bladder
Superior and inferior vesical A (from Internal Iliac A)
Lymph drainage of bladder
External iliac LN
Internal, obturator
Nerve supply of bladder
PSNS via pelvic splanhnic nerves
SNS from L1,2 via sup and inf hypogastric plexus
How is the control of micturition
Bladder distends -> afferent impulse via pelvic splanchnics -> stimulate efferent to contract detrusor
High centres inhibit this
Prostate surfaces
Base
Apex
Anterior
Posterior
Inferolateral
What is the highest part of the bladder
Base!!!!!
What is the lowest part of prostate
Apex
What separates prostate and rectum
Denovilliers fascia
Where do the ejaculator ducts enter the prostate
Posterior surface, just below bladder, and pass to open into prostatic urethra
Zones of the prostate
Peripheral
Central
Transition
Features of peripheral zone of prostate
Surrounds central zone
Commonest site of prostate cancer
Most frequent zone for prostate cancer
Peripheral zone
Where is the zone of BPH
Transitional zone
Blood supply of prostate glands
Inferior vesical A => prostatic branch
Also, middle rectal, internal pudendal
Veins run into a plexus, thus joining vesicoprostatic plexus
Lymph drainage of prostate
Internal iliac nodes
Nerve supply of prostate
Acini - PSNS from pelvic splanchnics via inferior hypogastric plexus
Muscle fibres that assist with ejaculation are under SNS from inferior hypogastric plexus
What are the features of seminal colliculus
Prostatic utricle
Ejaculator ducts (lat to prostatic utricle)
What is the prostatic utricle
Remnant of paramesonephric ducts
Blood supply to ductus deferens
Superior vesical A => artery to ductus deferens (note: anastomoses with testicular)
Blood supply to seminal vesicle
A to seminal vesicles
From inferior vesicle and middle rectal A
Nerve supply of ductus deferens & seminal vesicles
Smooth muscles of ductus,seminal vesicles by inferior hypogastric plexus (motor symp fibres)
Features of the uterus
Fundus
Body
Cervix
Where do the uterine tubes enter uterus
At the cornu
What encloses the body of peritoneum
Broad ligament
What covers post surface of uterus
Rectouterine pouch of douglas
What are the aspects of uterine tube
Isthmus
Ampulla
Infundibulum
Blood supply of uterus & uterine tubes
Uterine A (int iliac) gives branches to cervix and vagina, anastomosis with ovarian A
Lymph drainage from cervix
External and internal iliac LN, sacral nodes
Lymph drainage of uterus
Upper part of body, fundus, uterine tube to para-aortic
Lower part of body = ext iliac nodes
Nerve supply to uterus & uterine tubes
Inferior hypogastric plexus
How is pain from the cervix transferred
Via pelvic splanhnic nerves w/ symphathetic nerves to T10 - L1
What is the normal position of the uterus
Anteflexed
What is the most fixed part of the uterus
The cervix, due to pelvic diaphragn, visceral pelvic fascia & peritoneal attachments
What are the features of broad lig
Mesoovarian, mesosalpinx
No supportive features
Holds the suspensory lig of the ovary
Round lig of the ovary journey
From junction of uterus & uterine tube to deep inguinal ring, to labium majus
What blood supply of round lig of uterus
Inferior epigastric A
Transverse cervical lig attachments
Cervix & vaginal fornix to lateral wall of pelvis
Uterosacral lig attachments
From post cervix below peritoneum embrancing retrouterine pouch and rectum => front of sacrum
What is the role of uterosacral lig
Keeps cervix braced backwards against forward pull of round lig
Maintains uterine anteflexion
What does the lig of ovary attach
Ovary to body of uterus
Where does the lig of the ovary attach
To lower pole of ovary, to the uterus
Blood supply to ovary
Ovarian A, direct branch of abdo aorta
How does the ovarian A reach the ovary
Via suspensory ligament
Lymph drainage of ovary
Para-aortic node
Some via round lig to inguinal nodes
Nerve supply to ovary
SNS from aortic plexus
PSNS via inferior hypogastric plexus
Vagina fornices
Anterior, posterior and lateral
What part of vagina has peritoneal covering
Posterior fornix, via rectouterine pouch
Relationship between ureter and vagina
Ureter at first adjacent to lateral fornix, then passes across the front of anterior fornix
Where are the bartholins glands (vestibular)
Vestibule of vagina, below hymen, in posterolateral wall
Blood supply of vagina
Vaginal A(int iliac)
Support from uterine, inf vesical and middl rectal
Venous drainage of vagina
Via plexus on pelvic floor to drain internal iliac V
Lymph drainage of vagina
Ext, internal iliac nodes
Nerve supply of vagina
Lower end = sensory fibres from perineal and post labial branches of perineal
Autonomic from inf hypogastric plexus supply blood vessels, smooth muscle of vagina and vestibular glands
Upper vagina only sensitive to stretch
Female urethral length and features
4cm, only has external urethral meatus
Blood supply of urethra
Upper = inf vesical
Lower = vaginal and internal pudendal A
Lymph drainage of urethra
Int, ext iliac nodes
Nerve supply of urethra
Inf hypogastric plexus and perineal branch of pudendal n
What is anterior to the internal iliac vessels
Ureter, fallopian tube, ovary
Posterior relations to internal iliac vessels
Internal iliac vein, sacral plexus, SI
Lateral relations to internal iliac artery
Ext iliac vessels, obturator n, psoas major
Medial relations of internal iliac A
Parietal peritoneum
Small bowel
Where does the internal iliac begin
L5/S1 at pelvic brim
Divisions of the int iliac A
Post - 3
Ant - 9 ish
Terminal branch of anterior division of internal iliac
Internal pudendal
Inferior gluteal
Post branches of int iliac A
Iliolumbar
Superior gluteal
Lateral sacral
Anterior divisions of int iliac A
Umbi
Sup vesical
Inf vesical
Uterine
Vaginal
Middle rectal
Inferior gluteal
Internal pudendal
Obturator
Where does the int iliac V start
In the greater sciatic notch
Where does int iliac V join ext iliac V
On medial surface of psoas
Tributaries of the int iliac V
(Apart from corresponding arterial veins)
Rectal venous plexus
Prostatic venous plexus
Uterine venous plexus
Vaginal venous plexus
What communicates the internal iliac V with the vertebral venous plexus
Lateral sacral V
What forms the sacral plexus
Lumbosacral trunk (l4,5)
Upper 4 ant rami of sacrum
Divisions of sacral plexus
Anterior divisions
Posterior diviisons
Anterior divisions of sacral plexus
Tibial part of sciatic nerve (L4 - S3)
N to obturator internus (L5, S1-2)
N to quad femoris (L4 to S1)
Pudendal N (S2,3,4)
Perineal branch of S4
Pelvic splanchnic nerves
What does n to obturator internus supply
Obturator internus
Super gemellus
Nerve to quad femoris supplies
Inf gemellus, hip joint
Quadratus femoris
Perineal branch of S4 supplies
Puborectalis, pubourethralis, pubovaginalis
Perianal skin
Pelvic splanchnic nerve component
PSNS from ant surface of S2-3 +4
Pass forward into inf hypogastric plexus where they mix with SNS to supply pelvic viscera and distal colon
Post divisions of sacral plexus
N to piriformis (S1-2)
Perforating cutaneous N (S2-3)
Sup gluteal N (L4-S1)
Inf gluteal (L5-S2)
Common perineal part of sciatic N (L4-S2)
What lies anterior to sacral plexus
Lateral sacral A + ureter (which passes in front of ALL parietal pelvic peritoneum and viscera)
What passes superior to sacral plexus
Sup gluteal A
What passes inf to sacral plexus
Inf gluteal A
What emerging nerves are apart of the inferior hypogastric plexus
SNS (via sup hypogastric plexus, half are preganlionic, others are sacral symp fibres)
PSNS (from pelvic splanchnics)
Where does the inferior hypogastric plexus lie in the male pelvis
Lateral to rectum
Posterolateral to seminal vesicle, prostate
Posterior to bladder
Where does the inferior hypogastric plexus lie in female pelvis
Lateral to rectum, cervix, vaginal fornix
Posterolateral to blader
Cutaneous nerve supply of anal region
Inferior rectal N (S3,4)
Perineal branch of S4
Coccygeal plexus S5
Urogenital cutaneous nerve supply
Ilioinguinal N
Dorsal nerve of pudenal
Posterior femoral cutaneous N
Perineal N of pudendal
What type of muscle (circular, longitudinal) makes up the anal region
ALL circular
Components of ext anal sphincter
Deep, superficial and subcutaneous parts
Deep parts are blended with puborectal of levator ani (anorectal ring)
Fibromuscular strands pass backwards to coccyx which contributes to anococcygeal lig
Internal anal sphincter formed fro
Thickening of inner circular muscle of rectum
What is the pectinate line
The site of anal valves, which are formed from folds of anal columns, which has glands and sinuses
Difference in epidermis of pectinate line
Superior to pectinate line = columnar
Inferior = stratified squamous
Arterial supply to anal region
Above pectinate = superior rectal A (from IMA); medial sacral (aorta), middle rectal (from int iliac)
Lower = inferior rectal (int pudendal A)
Venous drainage of anal region
Upper = via superior rectal & IMV to portal system
Lower = via inf and middle rectal V to int iliac V
Site of portosystemic anastomosis
Lymph drainagae of anal canal
Upper = lymph of rectal
Lower = superficial inguinal nodes
Nerve supply of anal canal
Inferior rectal branches of pudendal N = ext sphincter and sensory supply of 1-2cm above pectinate down
S2 to sphincter urethrae
SNS from pelvic plexus to contract int sphincter
Pelvic splanchnics to relax int sphincter
What is the nerve that controls external anal sphincter
Inferior rectal branch of pudendal N
What factors (anatomical) maintain continence
Puborectalis
Ext sphincter
Anorectal angle
Abdo pressure
Mucosal cushions
Ischiorectal fossa boundaries
Bae = perineal body, muscle of urogenital diaphragm, sacrotuberous lig and gluteus maximus
Medial wall = ext anal sphincter of anal canal, sloping levator ani muscles
Lateral wall = ischial tuberosity with obturator internus
Sharp apex = where medial and lateral walls meet
How do the 2 ischiorectal fossae communicate
Posteriorly, down in retrosphincteric space within the anococcygeal Lig
Where is the pudendal canal
Lower lateral wall of ischioanal fossa, overlies obturator internus and medial side of ischial tuberosity
Formed by splitting obturator fascia
Conducts from lesser sciatic notch to deep perineal pouch above perineal membrane
What is in the pudendal canal
Pudendal N
Internal pudendal vessels
What is the perineal body
Central tendon of perineum
A fibromuscular mass to which multiple muscles gain attachment and within they decussate
What muscles attach to perineal body
External anal sphincter
Pubovaginalis, pubourethralis
Part of levator ani
Bulbospongiosus
Superificial and deep transverse perineal musclesq=
What forms the deep perineal space of the male urodiaphragm
Superior fascia and inferior fascial (aka perineal membrane)
What is within deep perineal space
Membranous urethra
Internal pudendal vessels
Dorsal n of penis
Perineal n at the sides
Paried bulbo urethral glands
Sphincter urethrae
Deep transverse perineal muscles
What supplies the external urethral sphincter (sphincter urethrae) in men
Perineal branch of pudendal n
What forms colles or superficial perineal fascia
Scarpas fascia continuation of abdominal wall
What are the superficial perineal muscles in men
Bulbospongiosus
Ischiocavernosus
Superficial transverse perineal m
What n supplies bulbospongiosus m
Perineal branch of pudendal N (S2,3)
What n supplies ischocavernosus m
Perineal branch of pudendal N (S2,3)
What n supplies superificial transverse perineal M
Perineal branch of pudendal N S2,3
How does the internal pudendal A reach the deep perineal pouch, and what are its relationship to other vessels it travels with
Passes through pudendal canal
Dorsal N is above it
Perineal n below it
Internal pudenda A branches
Perineal branch
Artery to the bulb
Deep artery to penis
Dorsal artery
What are the terminal branches of pudendal Nerve
Dorsal N of penis/clitoris
Perineal N
Aspects of the penis
Root - bulb & crus
Body
Glans penis
What are the parts of the bulb of the penis and what do they do
Crus - attaches to perineal memrbane and ischiopubic rami, receives deep artery of the penis; continues as corpus cavernosum
Bulb becomes corpus spongiosum
What are the features of a transversely sliced penis
2x corpus cavernosum
1x corpus spongiosum, which contains urethra (spongy)
What surrounds the corpora of the penis
Tunica albuginea, and then outside of this, there is the deep fascia of the penis (Buck’s fascia)
What vessels lie deep to the deep fascia of the penis (Bucks)
Deep dorsal V, A and nerve
Blood supply of the penis
Deep artery of the penis
Dorsal artery
Artery to the bulb
*all are branches of internal pudendal A
Venous return of the penis
Mostly via deep dorsal vein, some via superificial dorsal vein into the vesicoprostatic venous plexus
Lymph drainage of the penis
Skin = superficial inguinal nodes
Glans and corpora = deep inguinal nodes
Nerve supply of penis
Skin = posterior scrotal and dorsal N (from pudendal N)
S2 is the dermatome
Ejactulation for bulbocavernosum and ischiocavernosum is perineal N (from pudendal)
SNS from L1 via sup and inf hypogastrics for ejaculation
PSNS via pelvic splanchnics for erection
What forms erection (nervous system)
PSNS (via pelvic splanchnics)
What forms ejaculation (nervous system)
SNS and somatic, from T11-L2
What are the sections of the male urethra
20cm in length, 3 parts
Prostatic
Membranous
Spongy
What epithelium lines the urethra
Transitional to navicular fossa
Then stratified squamous
Narrowest part of male urethra
External meatus
What nerves supply male urethra
Perineal
Inf hypogastric plexus
Layers of the scrotum
Skin
Dartos
Ext spermatic fascia
Cremasteric
Internal spermatic fascial
Testis with tunica vaginalis (parietal, visceral)
Tunica albuginea
Blood supply of scrotum
Superficial and deep ext pudendal A (from femoral)
Scrotal branches of perineal A (internal pudendal)
Lymph drainage of scrotum
Superficial inguinal nodes
Nerve supply to scrotum
Ant 1/3 = ilioinguinal and genital branch of genitofemoral
Post 2/3 = scrotal branch of perineal (S3), posterior cutaneous femoral N (S2)
Joints of the pelvis
Sacroiliac
Sacrococcygeal
Pubic symphysis
Ligaments of the pelvis
Sacrotuberous
Sacrospinous
Iliolumbar lig
What type of joints is SI joint
Synovial joint
What ligaments support SI joint
Anterior & posterior SI ligaments
Interosseous sacroiliac lig
What type of joint is sacrococcygeal
Symphysis
What are the ligs support sacrococcygeal joint
Anterior and posterior sacrococcygeal lig
Lateral sacrococcygeal lig (forms the foramen for ant rami of 5th sacral N)
What type of joint is pubic symphysis
Secondary cartilaginous
Each side covered with hyaline cartilage and a fibrocartilage disc b/w
What reinforces pubic symphysis
Superior pubic lig
Arcuate pubic lig (below)
What does sacrotuberous attach to
Sacrum, PSIS, PIIS and transverse tubercle of sacrum to ischial tuberosity
What are the attachments of sacrospinous lig
Lower sacrum and coccyx to spine of ischium
