Anatomy – Abdomen

Transpyloric plane Plane or level midway between the jugular notch and the pubic symphysis to which many structures are related Midway between xiphisternum and umbilicus/Hands breadth below xiphisternal joint Related structures Lower border L1 Tip 9th costal cartilage (fundus of gallbladder) Head, neck, body pancreas Hilum left kidney just above, right kidney just below SMA leaves aorta, Splenic vein joins SMV to form portal vein Supracolic compartment above (liver, spleen, stomach); Infracolic compartment below (small intestine, colon)

Inguinal canal oblique intermuscular space 4cm long lying in medial half of inguinal ligament between deep and superficial inguinal rings Borders Anterior wall External oblique anastomosis, internal oblique Posterior wall Conjoint tendon medially Transversalis fascia Deep inguinal ring - opening in transversalis fascia 1cm above midpoint of inguinal ligament Inferior epigastric artery deep to post wall at medial edge of deep ring, gives rise to cremasteric branch

Inguinal triangle Lateral – inferior epigastric artery Media – lateral edge of rectus abdominis Inferior – inguinal ligament Hernias passing lateral to artery pass through deep ring and indirect; passing medial to artery are direct Floor Lower edge inguinal ligament Roof Lower edges internal oblique and transversus Arch over from in front of cord laterally to behind cord medially to form conjoint tendon which inserts into pubic crest and pectineal line of pubic bone

Contents of inguinal canal → Spermatic cord, Ilioinguinal nerve

Spermatic cord Coverings (are also coverings of testis) Skin, subcut tissue (dartos fascia) Internal spermatic fascia, Cremasteric muscle and fascia, External spermatic fascia, Tunica vaginalis Contents Ductus deferens/its artery Testicular artery and veins Processus vaginalis Branch of genitofemoral nerve Autonomic nerves Lymphatics

Testis Epididymis attached to postero-lateral testis Canal of epididymis forms ductus deferens Testis and epididymis covered by visceral and parietal tunica vaginalis Hydrocele forms between these 2 layers Testicular artery - Branch Ao; Pampiniform plexus; Lumbar and pre-aortic nodes

Blood supply of gut Venous drainage Superior mesenteric vein joins splenic vein to form portal vein Drains blood from GIT in abdomen and most of GIT in pelvis; also pancreas, spleen, gallbladder 5 sites porto-systemic anastomosis - low oesophagus, upper anal canal, bare area liver, periumbilical, retroperiteum

1 Foregut Coeliac trunk Supplies lower oesophagus to opening bile duct into duodenum, liver, pancreas and spleen. T12, 2nd abdominal branch aorta Branches Left gastric, Splenic, Common hepatic Branches Hepatic, Right gastric, Gastroduodenal artery

Midgut SMA Supplies gut from entrance of bile duct to splenic flexure, L1 Passes down behind splenic vein and body of pancreas Lies ant to left renal vein, uncinate process pancreas and 3rd part duodenum Branches Inf pancreaticoduodenal, Middle/Right colic, Ileocolic, Jejunal and ileal branches+++

Hindgut IMA Supplies gut from splenic flexure to upper third of anal canal (dentate line) Arises from front of aorta behind 3rd part of duodenum Level L3, level of umbilicus, 3cm above aortic bifurcation Branches Left colic, Sigmoid, Superior rectal

Duodenum C-shaped tube that loops around the head of the pancreas 1st part Level of L1, 5cm long Runs right, up, back from pylorus First 2.5cm (duodenal cap) lies between greater/lesser omenta in front of gastroduodenal A, bile duct, portal vein Second 2.5cm runs on upper part of head pancreas to medial surface right kidney and is retroperitoneal 2nd part Level of L2, 7.5cm long Passes down over hilum right kidney, Retroperitoneal Crossed by attachment of transverse mesocolon Lies alongside head of pancreas Posteromedial wall receives hepatopancreatic duct 3rd part Level of L3, 10cm long Curves forwards over right psoas/IVC/aorta and reaches left psoas, Retroperitoneal Crossed by SMA Inferior border is a level commencement inf mesenteric artery, Upper border against body of pancreas 4th part Level of L2, 2.5cm long To left of aorta lying on left psoas and left sympathetic trunk Reaches lower border of pancreas Retroperitoneal until duodenojejunal junction

Spleen 1x3x5inches, Weighs 7oz, Lies between 9th and 11th ribs under diaphragm Diaphragmatic surface Visceral surface Splenic notch anteriorly, Colic impression, Renal impression, Gastric impression Hilum Blood supply Splenic artery Lymphatic drainage Pancreaticosplenic nodes and coeliac nodes Nerve supply Coeliac plexus – sympathetic fibres only

2 Liver Weighs 1500g and receives 1500ml/minute Surface marking Upper margin level xiphisternum Left 5 th IC space 8cm from midline Right 5 th -11th rib mid axillary line Lower border -costal margin Right lobe Right of falciform, Left lobe Left of falciform Caudate lobe Post between IVC and fissure for ligamentum venosum Quadrate lobe Post between gallbladder fossa and ligamentum teres Surfaces Diaphragmatic Visceral H shaped pattern, Cross-piece is porta hepatis Right limb is inferior vena cava above and gallbladder below Left limb is fissure for ligamentum venosum and ligamentum teres Borders Inferior border Notched by ligamentum teres - lies in lower free margin falciform ligament. Gallbladder Superior border Falciform ligament becomes left triangular ligament and upper layer of coronary ligament Porta hepatis R/L hepatic ducts (ducts anterior – duct, artery, vein) R/L hepatic arteries (hepatic veins enter IVC on posterior surface) R/L branches of portal vein Lymph nodes, Nerves Blood supply Hepatic artery, portal vein, 3 hepatic veins

Biliary tract Hepatic ducts Common hepatic duct in porta hepatis → R/L hepatic ducts → joined by cystic, forms bile duct Bile duct 8cm long 8mm diameter Galbladder - Fundus, Body, Neck

Kidneys, ureters and adrenals Kidneys Hilum right kidney lies just below transpyloric plane 5cm from midline (level of L1) Hilum left kidney just above transpyloric plane 5cm from midline (level of L2) Normal kidney measures 3x6x12cm Renal fascia, Perinephric fat Capsule Cortex Contains renal columns Medulla Contains renal pyramids → renal papilla → projects to minor calyx → 3 major calyses; Renal pelvis Blood supply Renal arteries, Renal veins Most anterior structure at hilum Lymphatic drainage Para-aortic nodes

Ureters 25cm long Hilum kidney posterior to renal vessels at L1/2 → Down on psoas major under peritoneum → Leave psoas muscle at bifurcation common iliacs → Over SI joint → Forward/medial at ischial spine → Base of bladder Crosses genitofemoral nerve, obturator nerve, artery and vein; Crossed by gonadal vessels Narrowings – PUJ, pelvic brim, VUJ Surface marking tip 9th costal cartilage to bifurcation common iliac artery Radiographic marking L1 → Medial to tips transverse processes lumbar vertebrae → Cross pelvic brim at SI joint → Ischial spine → Pubic tubercle Blood supply Renal and gonadal artery and vein Adrenals In renal fascia, separate from kidneys by perirenal fat

3 Pancreas Head Retroperitoneal at level L2/transpyloric plane Moulded to c-shaped concavity of duodenum Lies over IVC and right and left renal veins Neck Narrow band of pancreatic tissue lying in front of commencement of portal vein Body Across aorta at origin coeliac trunk, left crus, left psoas, lower left adrenal to hilum left kidney Tail Blood supply Neck, body and tail Splenic artery; Head Inf/sup pancreaticoduodenal

Diaphragm

Retroperitoneal structures Aorta, IVC Cisterna chili, Sympathetic trunk Kidneys, Ureters Pancreas, Most of duodenum and adrenals Posterior abdo wall – psoas major, quadratus lumborum, iliacus

Abdominal aorta Through aortic foramen, Divides on body L4 Branches Unpaired = coeliac trunk, SMA, IMA Inferior phrenic Coeliac trunk Branches – common hepatic, splenic, left gastric Adrenal arteries Superior mesenteric artery Renal arteries arising at right angles at L2 Gonadal arteries Cross ureter Inferior mesenteric arteries Lumbar arteries Four pairs, opposite upper 4 lumbar vertebrae Median sacral artery Small posterior branch Right and left common iliac artery Originate on body of L4 Branches External iliac arteries becomes femoral artery Branches Inf epigastric, Deep circumflex iliac Internal iliac arteries

IVC Opposite L5 from confluence common iliac veins behind right common iliac artery Runs up to right of aorta Pierces central tendon of diaphragm T8 No gut branches due to portal system

CT Spaces – hepatorenal, splenorenal ; in pelvis – rectouterine pouch of douglas, vesicouterine pouch AXR Stomach, large bowel, small bowel, psoas, liver, kidneys, bones (ribs/spine/pelvis/femurs)

Layers of lower abdominal wall Skin – Camper fascia (superficial fatty tissue) – Scarpa fascia (deep membranous) – Investing fascia – External oblique – Internal oblique – Transversus abdominis – Transversalis fascia – fat – parietal peritoneum

Hepatic portal system Drains venous blood from: - bowel from lower 1/3 oesophagus to upper anal canal - unpaired abdominal organs (spleen, pancrease, gallbladder) To liver sinusoids Formed by SMV and splenic vein behind neck of pancreas IMA joins splenic vein along its length

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