Radiology Pt1 - Abdominal/pelvic Anatomy

Front 1

Anterior abdominal wall

Back 1

From superficial to deep

Skin
Camper's fascia
Scarper's fascia

MUSCLES:
Rectus abdominus
External oblique
Internal oblique
Transverse abdominal

Fascia transversalis
Extraperitoneal fat
Parietal peritoneum

Front 2

Camper's fascia

Back 2

The most superficial layer of fascia of the anterior abdominal wall, just beneath the skin. Contains variable amounts of fat.

R:
It passes over the inguinal ligament to merge with the fascia of the thighs.
In the male it continues over the penis and down the spermatic cord into the scrotum. It passes backwards to the perineum.
In females it is continuous with the labia majora and perineum.

Front 3

Scarper's fascia

Back 3

The deeper layer of superficial fascia in the anterior abdominal wall, above the muscles but below Camper's fascia.

R:
Connected to the external oblique muscle aponeurosis. Adherent to the linea alba in the midline.
Proximally it blends with the superficial fascia of the chest.
Distally it blends with the fascia lata of the thigh and continues over the penis and scrotum in males, or labia in females.

In the penis it forms the fundiform ligament. In females it is continuous with the fascia of Colles in the perineum.

Front 4

Rectus abdominus muscle

Back 4

A paired muscle running vertically on each side of the anterior abdominal wall.

Seperated by the midline linea alba - strong connective tissue.

Seperated by 3 transverse fibrous bands (normally)

Contained in the rectus sheath, which above the arcuate line is formed by the aponeuroses of external oblique (superficial), internal oblique (divides to be superficial and deep) and transversus abdominus (deep). Below the arcuate line (1/2 way between umbilicus and pubis) all layers of the sheath are superficial to the rectus muscle.

O: Pubic symphysis and pubic crest.

I: Xiphisternum/xiphoid and lower costal cartilages (5-7) superiorly.

A: Flexes trunk. Accessory muscle of respiration.

N: Thoraco-abdominal nerves (T7-T12)

Front 5

External oblique muscle

Back 5

The largest and most superficial muscle of the lateral anterior abdomen.

Broad, thin, somewhat quadrilateral.

O:
External borders ribs 5-12. The fibres of origin are interspersed with serratus anterior on the upper 5 ribs, and latissimus dorsi on the lower 3.

I:
Iliac crest, inguinal ligament distally.
Forms a midline aponeurosis in the midclavicular line, which crosses to the linea alba.

A: Rotates torso, flexes trunk and compresses abdomen.

N: Lower 6 intercostal nerves and subcostal nerve

R: Originates along slips of serratus anterior and latissimus dorsi. Superficial to internal oblique and transversus msucles.

Deep to Scarpa's fascia.

The aponeurosis runs to the midline over the rectus abdominus.

Front 6

Internal oblique muscle

Back 6

Deep to the external oblique, a triangular-ish muscle between the rubs and iliac crest. Fibres are perpendicular to course of external oblique.

O: Lateral 1/2 of the inguinal ligament, upper 2/3rds of the iliac crest

I: Linea alba medially (becomes aponeurotic), xiphoid and costal margin (10-12th ribs)

A: Rotates trunk, lateral flexion.
Compresses thoracic cavity during exhalation.

N: Lower intercostal nerves, iliohypogastric and ilioinguinal nerves (both branches off L1 in the lumbar plexus).

R: Deep to external oblique, superficial to transversus.

The aponeurosis medially splits over rectus abdominus above the arcuate line. Below the line it runs superficially.

Front 7

Transverse abdominal muscle

Back 7

The deepest anterior abdominal muscle, a core stabiliser, although it is smaller than the other abdominal muscles. Runs transversly.

O: Lateral 1/3rd inguinal ligament, anterior portion of the inner lip of iliac crest, and inner subcostal border (ribs 6-12).

I: Midline, from xiphoid, to linea alba, to pubis.
At the pubis it joins with the lower fibres of internal oblique, to form the conjoint tendon, which inserts to the pubic crest and forms the roof of the inguinal canal.

A: Stabilises thorax/pelvis and compresses ribs.

N: Lower intercostal (T7-T11) and the iliohypogastric and ilioinguinal nerves (branches off L1 from sacral plexus).

R: Above the arcuate line the central aponeurosis is deep to rectus abdominus.
Lies deep to the internal oblique, and superficial to the fascia transversalis

Front 8

Fascia transversalis

Back 8

Deep to the anterior abdominal muscles, the outer layer of fascia around the peritoneal cavity.

R: Disappears posteriorly into pararenal fat.
Distally it attaches to the iliac crest anterior to iliacus, the posterior margin of the inguinal ligament and is continuous with the iliac fascia.
Medial to the femoral vessels it weakly attaches to the pubis, behind but adhered to the conjoint ligament.
It descends to form the anterior wall of the femoral sheath.

The deep inguinal ring is the location where the spermatic cord or round ligament passes through the fascia transversalis. The fascia is prolonged onto these structures.

Front 9

Pyramidalis

Back 9

A small muscle at the lower section of the linea alba, runs from the linea 1/2 way between the umbilicus and the pubis, to the pubic crest and symphysis.

A: Tightens the linea alba.

N: Subcostal nerve (T12)

V: Absent in 20%

Front 10

Inguinal canal

Back 10

A short ~4cm canal between the deep and superficial inguinal rings that transmits the spermatic cord in males and the round ligament in females. It also contains the ilioinguinal nerve (from L1 at lumbar plexus)

The canal runs inferomedially proximal to the inguinal ligament.

The deep inguinal ligament is the opening in the transversalis fascia, communicating between the internal compartment and subcutaneous space.

R:
Mnemonic: MALT
M = medial are muscles (internal oblique, transverse abdominus)
A = anterior (superficial) are aponeuroses (ex. and int. oblique)
L = lateral are ligaments (inguinal ligament)
T = transversalis fascia/tendons posterior/deep

The canal ends at the superficial inguinal ring, which pierces the external oblique aponeurosis, 1cm above and lateral to the pubic tubercle.

Front 11

Inguinal ligament

Back 11

A band running from the pubic tubercle to the ASIS. Formed by the external oblique aponeurosis and conintuous with the fascia lata of the thigh.

R:
Forms the base of the inguinal canal, and the superior portion of the femoral triangle.

Front 12

Femoral triangle

Back 12

A space in the upper thigh that transmits the femoral nerve, artery and vein (lateral to medial) as well as the inguinal chain of lymph nodes.

R:

Superiorly: Inguinal ligament
Medially: Adductor longus
Laterally: Sartorius
Floor: Iliopsoas laterally, Pectineus and Adductor longus medially
Roof: Fascia Lata

Front 13

Liver segmental anatomy

Back 13

Couninaud segmental classification (functionally seperate segments)

LOBES:
The middle hepatic vein seperates the liver into right and left lobes. This line is called the principal plane, running between the IVC and the gallbladder. On the external surface the line is 4cm to the left of the falciform ligament.

SEGMENTS:
The division are based on the hepatic vein and portal vein courses.

The right portal vein plane seperates the right lobe of the liver into upper and lower segments. The left portal vein divided the most lateral left lobe into posterosuperior portions and anteroinferior portions.The central left lobe is divided AP only.

The segments start on the left odf the IVC and run clockwise, and in the right lobe run anticlockwise around the base of the liver looking in from lateral.

Segment 1: Caudate segment. Directly adjecent to the IVC posteriorly in the left lobe.
Segment 2: Posterior far left (is superior)
Segment 3: Anterior far left (is inferior)
Segment 4: Quadrate lobe. Anterior left in line with IVC. This can be divided into 4a and 4b by the left portal vein.

Segment 5: Anteroinferior right lobe
Segment 6: Posteroinferior right lobe
Segment 7: Posterosuperior right lobe
Segment 8: Anterosuperior right lobe

FUNCTION:
The hepatic arteries, portal veins and bileducts run to the centre of each segment, and then give off small branches to the microscopic function hepatic lobules (centrally again).

The hepatic veins run between segements.

Front 14

Liver blood supply

Back 14

a

Front 15

Portal venous system

Back 15

The portal vein returns blood from the gut to the liver, where it is processed (detoxified) and then drained by the IVC.

PORTAL VEIN:
Around 5cm long, runs along the free edge of the lesser omentum, behind the CBD and hepatic artery (most anterior).

The portal vein is formed by the confluence of the IMV, SMV and splenic vein. The IMA usually drains into the splenic vein prior to joining the portal vein.
Small drainage branches into the portal vein proper include the right and left gastric veins, the oeseophageal veins and the cystic vein.

The SMV:
Drains the same territory as the SMA supplies - the midgut. So drains the ileum, jejunum as well as the iliocolic, right colic and middle colic veins. Additionally, the SMV drains the right gastroepiploic vein (this appears in lieu of SMA pancreatic branches).

IMV:
Drains the same territory as the IMA supplied - the hindgut. Thus drains the left colic, sigmoid and superior rectal veins. The IMV drains into the splenic vein in normal anatomy.

SPLENIC VEIN:
The splenic vein follows the same course as the splenic artery, and drains the spleen, the short gastric (posterior gastric) veins and the left gastroepiploic veins. It also drains the IMV.
Pancreatic branches appear to be less prominent in the vein than the artery although the drainage route is the same (body/tail by splenic, head by SMV).

OTHER BRANCHES:
The left and right gastric (coronary) veins drain the lesser curve. The left gastric also drains the lower portion of the oesophagus.
The cystic vein drains the gallbladder.

RELATIONSHIPS:
IMV - to the left of IMA
SMV - to the right of SMA
Splenic vein - Posterior to the pancreas, joins the portal vein behind the head.
Portal vein - Cofluence behind the head of pancreas. Passes behind the 1nd part of duodenum and along the free edge of the lesser omentum to the porta hepatis.
It is seperated from the IVC in the porta by the epiploic foramen.

PORTOSYSTEMIC ANASTAMOSES:
4 main areas, where systemic drainage combines with portal. Important in portal hypertension as collateral channels can open.

Oesophageal - the lower part is drained via the left gastic vein to portal vein. The upper part is drained into the IVC.

Rectum - the upper part drained by superior rectal vein to IMV, the mid and lower parts drained by inferior rectal vein to internal pudendal to internal iliac.

Umbilicus - the normally obliterated umbilical and paraumbilical veins are the ligamentum teres, which runs from the portal vein to the abdominal wall. The abdominal wall veins drain inward to the IVC.

Retroperitoneal veins - A rich plexus of para-vertebral veins connect mesenteric portal channels (around small and large bowel) to lumbar and phrenic veins draining into the IVC.

Additionally there are frequently small spleno-renal anastamoses.

Front 16

Abdominal arterial supply

Back 16

The abdominal aorta has 4 midline branches and 4 major paired lateral branches, as well as multiple minor lateral branches (lumbar arteries)

Midline:
Coeliac trunk L1
Superior mesenteric artery L1
Inferior mesenteric artery L3
Median sacral artery (terminal at iliac bifurcation) L4

Lateral branches:
Inferior phrenic T12
Middle adrenal L1
Renal arteries L1/2
Gonadal arteries L3
Bifurcation - common iliac arteries L4

Front 17

Abdominal venous drainage

Back 17

a

Front 18

Lesser sac

Back 18

a

Front 19

Hepatic peritoneum reflections

Back 19

a

Front 20

Diaphragm

Back 20

The diaphragm is a thin sheet of muscle that seperates the thoracic cavity from the abdominal cavity. It is domed bilaterally, sloping mainly anterior to posterior, and originates from the xiphoid, the costal borders of the lower 6 ribs, and the lumbar vertebrae.

PARTS:
3 muscle slips - sternal, costal and lumbar.

Openings:
Aortic hiatus - the aorta, azygos vein and thoracic duct pass through here. The structure is midline, just anterior to vertebrae, and at the level of T12 (remember 'aortic hiatus' has 12 letters).
The aortic hiatus is ringed by the median arcuate ligament.

The oesophageal hiatus is anterior and slightly left of the aortic hiatus. It contains the oesophagus, oesophageal arteries and the anterior and posterior vagal trunks.
It passes through the diaphragm at T10 (oesophagus has 10 letters).

The caval opening passes the vena cava and several branches of the right phrenic nerve. It is anterior and left of the oesophageal hiatus, just lateral of the midline. The cava passes through the diaphragm at T8 (vena cava has 8 letters).

Adjacent to the crura bilaterally are the psoas arches, through which the psoas and the sympathetic trunks pass. These are formed by the medial arcuate ligaments.

Lateral to this is the lateral arcuate ligament, which runs over the quadratus lumborum as it reaches the diaphragm. The subcostal nerve, artery and vein pass through here.

The splanchnic nerves pass through apertures in the crura. The hemiazygos vein also passes through an aperture in the left crus.

NEURO:
Phrenic nerves. C3-C5 in the spine. These pass down along the middle mediastinum, the right over the right atrium and the left over the left ventricle (outside the pericardium).

Front 21

Biliary tract

Back 21

a

Front 22

Stomach

Back 22

Between the oesophagus and duodenum.

Front 23

Coeliac trunk

Back 23

The first anterior branch of the abdominal aorta, also the largest.

Supplies the foregut (stomach, liver, spleen, part of pancreas)

BRANCHES:
Bifurcates shortly after origin into a left splenic branch and a right hepatic branch.
The splenic artery gives off the left gastric artery, inferior branches to the pancreas (including the larger dorsal pancreatic and pancreatica magna arteries to the head and tail respecitvely).
Distally the splenic artery gives of the left gastroepiploic artery and posterior gastric arteries before ending in the spleen.

The hepatic artery (or common hepatic artery) runs right, giving off the right gastric artery and gastroduodenal artery in a short distance. The distal lateral branch is the hepatic artery proper and supplies the liver.
The right gastric runs around the lesser curve to anastamose with the left gastric, supplying the lesser curve of the stomach.

The gastroduodenal artery bifurcates into a left-running right gastroepiploic artery and the downward superior pancreatic artery. The gastroepiploic, like the gastric, anastamoses with it's fellow from the splenic artery, in this case around the greater curvature of the stomach.

The superior pancreatic splits into anterior and posterior divisions around the pancreatic head, which anastamose with the ant and post divisions of the inferior pancreatic artery (from the SMA).

The anterior division gives off the dorsal pancreatic artery, which curls around the uncinate process to pass behind the pancreas and anatamose with the splenic artery. The dorsal pancreatic artery gives off the transverse pancreatic artery, which runs posteriorly behind the body of the pancreas, joining with the pancreatic branches and pancreatica magna from the splenic artery as a rich vascular network.

RELATIONSHIPS:

The hepatic artery passes right, along the free edge of the lesser omentum to the porta hepatis. It is anterior to the CBD and the portal vein (most posterior)

The GDA runs behind the 1st part of the duodenum before bifurcating below it.

The gastric arteries run around the lesser curve, the gastroepiploic around the greater curve.

The superior pancreaticoduodenal has an anterior and posterior branch which pass around the pancreatic head, anastamosing with like branches of the inferior pancreaticoduodenal. The branches curve around the inside of the duodenal C.

The splenic artery passes immediately superior to the pancreas, passing branches downward to it. It terminates in the spleen.

Front 24

SMA

Back 24

The second midline (and second largest) branch of the abdominal aorta.

The superior mesenteric artery supplies the midgut -
Part of the pancreas, the small bowel from 2nd part of duodenum onwards, and 2/3rds of transverse colon.

The artery courses from the midline to the left iliac fossa, through the mesentary.

BRANCHES:
The inferior pancreatico duodenal artery
The Middle colic (arises superior to other colic branches to supply transverse colon)
The right colic artery
Iliocolic artery - also gives a small 'artery to the appendix'
Down the left side are multiple ileal and jejunal branches

The end arteries to the bowel arise from anastamoses between adjacent arteries - for example between the right colic and middle colic. These (called marginal arteries) run longitudinally along the bowel, and give off vascular arcades to the walls. These are called vasa recta in the small bowel and 'terminal end arteries' in the large bowel.

Front 25

IMA

Back 25

The inferior mesenteric artery is the third midline artery arising
from the abdominal aorta. It supplies the hindgut.

It runs down into the left iliac fossa

Supplies the distal 1/3rd of the transverse colon, the sigmoid and the upper part of the rectum.

BRANCHES:
Left colic artery
Sigmoid branches
Superior rectal artery

Front 26

Arterial anastamoses

Back 26

a

Front 27

Lateral aortic branches

Back 27

a

Front 28

Kidneys

Back 28

Lie in the perirenal space, on the quadratus lumborum and lateral to psoas.

PARTS:
Pelvis - drains major calcyces (2-3)
Major calyces - drain 2-4 minor calcyces
Renal papilla - the peak of each medullary pyramid, indents a minor calyx
Cortex - outer layer, contains corpuscles/parts of tubules
Medulla - contains distal tubules/LoH

Arteries - usually 1 for each kidney, arising at L1/L2. Can be accessory arteries from aorta or common iliacs.

The artery usually divides into 5 segmental arteries:
superior
anterior
posterior (the only one to run behind the pelvis, all others in front)
inferior
pelvis/calcyceal branch

The segmental branches give rise to 4-6 arcuate arteries, which curl around the medulalry pyramids and supply cortex via tiny interlobular arteries.

Veins - usually 1 for each kidney. Anterior to artery and renal pelvis. Can have accessory veins.

The other variation is early divergence of the minor branches - can look like multiple vessels but common origin.

The veins develop as a circumferential ladder around the aorta, with 2 veins taking the role of the IVC from each iliac.
Persistence of this pattern is called a left sided IVC, where the left leg drains into the left renal vein via a persistant vessel.
The other anomaly (more common) is that the posterior venous rami around the aorta persist. Most commonly this results in a circumaortic renal vein. Rarely the anterior component obliterates and only the posterior component remains (retroaortic renal vein)

VARIATIONS:
Pelvic kidneys - embryologically the kidneys lie close together and in the pelvis before ascending

Horseshoe kidney - remains fused across midline 1/400
usually accompanied by vessel variation also.

Foetal lobulation - clefts in the contour of kidney at sites of lobar differentiation.

Duplication - can have either totally seperate structures or partial duplication, with a large kidney showing 2 hila, with its own vessels and pelvis

Hypertrophied column (of Bertin)
the columns between the medullary pyramids can be congenitally hypertrophic, appearing like a tumour

Front 29

Ureter

Back 29

25-30cm long tube from kidney to bladder.

Retroperitoneal. Superiorly in perirenal space, then lying on the psoas muscle, then in pelvis along lateral pelvic wall near internal iliac veins.

Curve anteromedially to enter the bladder at the level of the seminal vesicles/cervix.

PARTS:
Vesicoureteric junction - the ureter passes through the muscular wall obliquely, creating a pseudo-valve.

A/V/N:
Multiple and numerous blood supplies from gonadal, aortic, renal, vesical, rectal and iliac branches. Veins are the same.

Nerve supply is stretch sensation and autonomics via local plexuses.

Front 30

Bladder

Back 30

Retroperitoneal (extraperitoneal really at this level)
- there are several local reflections of peritoneum draping around the bladder

Rectovesical pouch which is the most dependant place for free fluid to be found in men
Vesicouterine pouch (of Douglas) is the most dependant in women.

SPACES AROUND BLADDER:
perivesical - contains the bladder and urachus
prevesical (of Retzius) between bladder and symphysis. Communicates with retroperitoneum and presacral space.

BLADDER WALL:
Mostly detrusor muscle
The trigone is the triangular base of the bladder between the ureteral bladder orifices posterosuperiorly and the internal urethral opening inferiorly.

A/V/N:
Blood supply via superior vesical arteries from IIAs mainly
Drainage is via plexi of veins - vesical and prostatic in men, vesical and uterine in women.
Both mainly drain to internal iliac veins.

Neuro is parasympathetics from pelvic splanchnic and inferior hypogastric nerves. Sensory fibres follow the same nerves.

VARIATIONS:
Persistant urachus - the normally obliterated channel between umbilicus and bladder, become the median umbilical ligament. If persistant can be a 'cyst' or 'diverticulum'.

Bladder diverticulae are common, and can be acquired due to minor trauma or congenital (Hutch diverticulum) as site of ureterovesical junction.

Duplicated collecting system - usually due to duplicate kidney, multiple ureters drain to bladder.

Ectopic insertions of ureters can also occur

Retrocaval ureters pass behind the IVC instead of running alongside it, and can be a cause of partial ureteric obstruction.

Front 31

Pelvis

Back 31

false pelvis -
the large open region bounded by the sacrum, innominate bones, iliopsoas and the rectus sheath anteriorly

true pelvis - the smaller region between the coccyx and symphysis. It is bounded below by the piriformis and coccygeus muscles.

Front 32

Rectum

Back 32

15-20cm long, from anal canal to sigmoid.

Rectosigmoid junction is at the S3 level roughly.

Features:
VALVES:
Valves of Houston: 3-5 lateral folds which anchor the circular muscle layer in fan shaped arangements.

When there are three they are called superior, middle and inferior, and they are orientated anterior right for the middle valve and posterior left for the others.

The middle valve is the Plica transveralis of Kohlrousch, and lies in line with pouch of Douglas/rectovesical pouch.

The inferior valve is 2-4cm above the anal margin, and corresponds with the termination of the peritoneum anteriorly.

PERITONEUM:
The upper 1/3rd is covered in front and laterally by peritoneum. It is still retroperitoneal as the posterior aspect is not covered.
The middle third is covered only anteriorly.
The lower third is totally extraperitoneal and unrelated to any peritoneum.

MUSCLES:
There is a circular inner layer and longitudinal outer layer. These condense to form the internal sphincter at the anal canal.
The external sphincter muscles are largely below the rectum, around the anal canal, although the levator ani/puborectalis supports the anorectal junction.

RECTOSIGMOID JUNCTION:
Also called the sphincter of O'Beirne, is a pseudo-sphincter formed by a thickening of the muscular layer.

BLOOD SUPPLY:
Upper 1/3rd is superior rectal artery from IMA
Mid and lower 1/3rds are Mid and inferior rectal arteries from posterior trunk of internal iliac.

Front 33

Prostate

Back 33

The gland that surrounds the urethra just below the urinary bladder. The urethra in the prostate is called the prostatic urethra and merges with the ejaculatory ducts at this location.

The prostate produces the alkaline component of semen.

It is divided into function zones, as well as anatomical lobes.

ZONES:
The urethra is central. Anterolaterally are the teardrop shaped transitional zones, which are where most prostate cancer arises.
The central zone is posterior and lateral (flat shape) and the peripheral zone wraps the gland circumferentially.
The fibromuscular zone is anterior.

The peripheral zone is 65% of the gland in young men
Central zone 25%
Transition zone 5%
Fibromuscular zone 5%

LOBES:
There are 2 large lateral lobes and a flat posterior lobe which circumferentially surround the internal structures.
Centrally the urethra is flanked anteriorly by the anterior lobe and posteriorly by the posterior lobe, both of which are small.

Front 34

External iliac artery

Back 34

The artery to the leg

O: Common iliac artery bifurcation at the pelvic brim, at the level of the sacroiliac joints.

B: Inferior epigastric artery, anastamoses with the superior epigastric of the ITA
Circumflex iliac artery, runs along the iliac bone/pelvic brim
Femoral artery, terminal artery, arbitrary division at the inguinal ligament.

R: External iliac vein posterior. By the termination at inguinal ligament the femoral vein is medial and the femoral nerve is lateral

Front 35

Internal iliac artery

Back 35

Main artery of the pelvis. It descends to the greater sciatic foramen and then gives off branches

O: Common iliac bifurcation at the level of the pelvic brim/sacroiliac joints.

B:
Divides into anterior and posterior trunks -

ANTERIOR TRUNK
Obliterated umbilical artery (medial umbilical ligament)
Superior vesical branches (usually from umbilical)
Obturator artery through obturator foramen
Inferior vesical (in males)/Uterine in females
Vaginal/deferential artery
Middle rectal (posterior)
Inferior gluteal (posterior)
Internal pudendal artery (terminal branch through greater sciatic, curls back around and inside via lesser sciatic foramen)

POSTERIOR TRUNK:
Iliolumbar
Lateral sacral
Superior gluteal

S:
Bladder via superior and inferior vesical/uterine
Uterus/vagina/ovaries/cervix/fallopian tubes via uterine
Vagina or vas deferens via vaginal/deferential
Adductor compartment and hip joint via obturator artery
Glutes via superior and inferior gluteal arteries.
Psoas/iliacus via iliolumbar. Small branch to cauda equina.
Sacral canal and lower back skin/muscle via lateral sacral arteries.
Penis/clitoris and anal canal (inf rectal) via internal pudendal

V: a great deal of variation. Arteries often arise from other branches. Just remember that gluteal, pudendal and rectal arise inferior, and obturator, vesical and umbilical arise superior.

Front 36

Common iliac artery

Back 36

O: Aortic bifurcation at L4

T: divides into external and internal iliacs at the pelvic brim, in front of the sacroiliac joints.

R: 4cm long.
Runs from L4 level to pelvic brim, along the medial border of the psoas muscle.

The terminal bifurcation is crossed by the ureter.

Is accompanied by the (posterior and right bilaterally) by th common iliac veins.
These veins become posterior after the bifurcation.

Front 37

Uterus

Back 37

Pear shaped structure behind the bladder, aroun 8cm in length.

PARTS:
CERVIX -
the cervix is the muscular canal between the vagina and uterine body. It is divided into the ectocervix and the endocervix.
The ectocervix projects into he vagina (around 3cm) and contains the external os (the opening of the cervix).
The endocervical canal runs from the external os to the internal os, and varies greatly in length.
The internal os opens into the uterine body.

UTERINE BODY:
The body is a muscled, pear shaped organ. The cavity internally is triangular, with the points formed by the internal os, and the fallopian tube openings.

The body is made of several layers of tissue - the endometrium (mucosal), the myometrium (muscular), the perimetrium (loose connective tissue) and the peritoneum. The body is enclosed in peritoneum.

The upper part of the body is called the fundus.

LIGAMENTS/SUPPORT:
Primarily supported by the pelvic and urogenital diaphragms.

Several ligaments also:

The broad 'ligament' - is actually mesentary for the uterus, which covers the uterus (mesometrium), fallopian tubes (mesosalpinx) and ovaries (mesoovarium). This membrane connects the uterus to the walls of the pelvis.

Pubocervical ligament - cervix to pubic symphysis.
Cardinal ligament (transverse cervical ligament) - the strongest support, in the base of the broad ligament. Wraps the cervix and attaches it to the ischial spine. These ligaments contains the uterine artery and vein bilaterally.
Uterosacral ligaments - rectouterine folds to sacrum anteriorly.

POSITION:
The uterus is normally anteverted (tipped forward on the cervix) and anteflexed (fundus tipped forward on body). Less commonly it can be retroverted or retroflexed.

VARIANTS:
Normal simple - one uterine body and cervix.
Bicornuate - 1 body and cervix, but a muscular septum in the fundus seperating the 2 'horns'.
Bipartite: Totally seperate uteri, single cervix
Duplicate: 2 cervixes, 2 uteri

VASCULAR:
Uterine artery via the anterior trunk of the internal iliac artery. The uterine artery arives at the level of the cervix and gives a descending trunk to the cervix, an ascending trunk to the uterus and the ascending trunk gives off a tubal branch to the fallopian tube and ovary. It anastamoses with the ovarian artery distally, which comes from the aorta and runs in the suspensory ligament.
The ureter passes behind the uterine artery at the cervix.

Front 38

Fallopian tubes

Back 38

8-10 cm in length, running from uterine cornua bilaterally to the ovaries.

P:
Interstitial segment: The segment that passes through the myometrium/uterine wall. Around 1cm in length.
Isthmus: The main length of the tube, running from the edge of uterus to the dilatation of the ampulla. Somewhat tortuous.
Ampulla: The point of initial dilatation of the tube between isthmus and infundibulum. It usually has a 90degree+ turn here.
Infundibulum: The funnel shaped opening of the tube, open to the posterior surface of the ovary to catch ovum as they are released. The infundibulum is ringed by the fingerlike projections called fimbriae.

L: Suspended by the broad ligament of the uterus to the lateral pelvic wall, the tubal portion called the mesosalpinx.

Vasc: Supplied by tubal branch of the uterine artery.

Front 39

Ovaries

Back 39

Variable in position, usually in the true pelvis. They sit posterior to the broad ligament, anterior to ureters and below iliac bifurcation in the ovarian fossa initially (nulliparous).

P: Medulla which is the central area that blood supply enters through
Cortex is the outer area that follicles develop in
Germinal epithelium is the covering layer, which is specialised peritoneum.

L:
Broad ligament: surrounds the uterine complex, called the mesoovarium around the ovary. Loosely holds complex in place to lateral pelvic walls.
The suspensory ligament: The main ligament of the ovary, attaches ovary to superolateral pelvic wall. The ovarian artery and vein passes through the suspensory ligament.
Proper ovarian ligament: a condensation of fibrous tissue that connects the ovary to the uterus anterior to the broad ligament.

Vasc: Dual blood supplies -
the ovarian artery via the suspensory ligament (anterolateral aortic branch) and ovarian artery via the tubal branch (internal iliac branch).

R:
Suspensory ligament holds ovary in craniocaudal orientation.
Fimbriae of fallopian tubes positioned behind ovary to catch follicles.

Front 40

Colon

Back 40

Large bowel

PARTS:
Caecum: 7 cm long, intraperitoneal, ileocaecal valve and appendix
Appendix: 6-15cm in length, intraperitoneal (has mesoappendix) and usually (2/3) retrocaecal. Also can sit inferior - pelvic - or upward. Appendiceal artery is a branch of ileocolic artery from SMA.

Ascending colon: Retroperitoneal. To hepatic flexure.

Transverse colon: Intraperitoneal, in transverse mesocolon. To splenic flexure.

Descending colon: Extraperitoneal. To sigmoid colon.

Sigmoid colon: Intraperitoneal, on sigmoid mesocolon. Very variable in length.

FEATURES:
Taeniae coli - the three thickened bands of muscle that run along the colon at anterior and postero-superior/inferior locations. These are the muscles of peristalsis, which are circumferential in the small bowel, 3 bands in the large bowel and anterior/posterior near circumferential bands in the rectum.

Appendices epiploica: Subserosal pockets of fat

Haustra and plica semilunaris: The haustra are the sacculations of the large bowel, the plica are the folds, which are caused by the taeniae being shorter than the bowel overall.

Front 41

Small bowel

Back 41

PARTS:
Duodenum:
4 parts - bulb, descending, transverse and ascending portions. The bulb is intraperitoneal, the rest are retroperitoneal.

Jejunum:
2-3m long, about 40% of the bowel.

Ileum:
No clear transition from jejunum. About 4m long (60% of bowel). Ends in iliocaecal valve.

FEATURES:
Plicae circularis - circumferential folds of bowel wall, more in younger people. More prominent is the proximal bowel, less in the distal ileum.

Ligament of Treitz: The suspensory ligament of the duodenum, at the DJ flexure. This is an expansion of the right crus of the diaphragm.

Lympoid follicles/Peyer's patches: in the submucosa. Not visible in most imaging. More in the ileum, less in jejunum.

NERVES:
Sympathetic and parasympathetic follow the arteries.

Sympathetic are splanchnic nerves, follow the SMA

Parasympathetic are branches of posterior vagal trunk, which passes diaphragm with oesophagus and runs with arterial branches.

Front 42

Abdominal sympathetic supply

Back 42

a

Front 43

Abdominal pelvic supply

Back 43

a