ABSTRACT
Foregut structures
– oesophagus, stomach, liver, pancreas, gallbladder, first part of duodenum
– arterial SS by coeliac trunk
Midgut structures
– second to fourth part of duodenum, jejunum, ileum, caecum, appendix, ascending colon, proximal two-thirds of transverse colon
– arterial SS by sup. mesenteric a.
Hindgut structures
– distal one-third of transverse colon, descending colon, sigmoid colon, rectum, U. part of anal canal
– arterial SS by inf. mesenteric a.
Layers of digestive tract mucosa (from innermost to outermost)
– mucosa (simple columnar epithelium → lamina propria → muscularis mucosa)
– submucosa
– muscularis externa
– serosa
Salivary gland
Submandibular gland (mixed mucous and serous secretion), divided by mylohyoid muscle into:
superficial part
– larger
– located in the neck
deep part
– located in the mouth; main submandibular duct opens into floor of mouth on sublingual papilla at side of lingual frenulum
sublingual gland (mucus secretion)
parotid gland (largest, purely serous)
57 Relationships of parotid gland
– sup.: zygomatic arch
– inf.: post. belly of digastric
– post.: mastoid process
– ant.: ramus of mandible
– med.: styloid process
Structures within parotid gland (from superficial to deep)
– facial n.
– superficial temporal v. + maxillary v. → retromandibular v.
– ext. carotid a. → superficial temporal a. + maxillary a.
Parotid duct
– arises from ant. parotid gland
– pierces buccinator
– opens into oral cavity opposite U. second molar tooth
Oesophagus
– approximately 25 cm long
– C6 to T12 (passes through hiatus in diaphragm at T10)
– lined with squamous epithelium
– relationships:
ant.: trachea, LA, R. pulmonary a.
post.: vertebral column, thoracic aorta, thoracic duct
RHS: azygos vein, thoracic duct
LHS: descending aorta
– cricopharyngeus muscle = upper oesophageal sphincter (narrowest point in whole GI tract)
– diaphragm = lower oesophageal sphincter
– points of constriction (where caustic substances may be trapped)
= cricopharyngeal constriction, aortic constriction (arch of aorta) and diaphragmatic constriction
– divided into three parts:
cervical part:
– striated m.
– SS by inf. thyroid a.
– venous drainage to BCVs
– innervated by recurrent laryngeal n.
thoracic part:
– mixed striated and smooth m.
– SS by oesophageal branches of thoracic aorta
– venous drainage to azygos system
– innervated by vagus n.
abdominal part:
– smooth m.
– SS by L. gastric a. of coeliac trunk.
– venous drainage to L. gastric v. and azygos system
– innervated by vagus n. and sympathetic n.
– lymphatic drainage: post. mediastinal nodes
58Nine quadrants of the abdomen:
– RUQ (R. hypochondrium), epigastrium and LUQ (L. hypochondrium)
– R. flank, umbilical and L. flank
– RLQ (R. iliac), suprapubic and LLQ (L. iliac)
Usual causes of RUQ pain:
– peptic ulceration, gastritis, hepatitis, pneumonia (R. lung), cholangitis, cholecystitis
Usual causes of epigastric pain:
– peptic ulceration, drug-induced gastritis, gastric reflux, biliary colic, acute pancreatitis, abdominal aortic aneurysm (AAA), oesophagitis, angina/MI
Usual causes of LUQ pain:
– acute pancreatitis, MI, splenic infarction, gastric reflux, peptic ulceration, pneumonia (L. lung)
Usual causes of RLQ pain:
– diverticulitis, acute appendicitis, cholecystitis, ruptured ovarian cyst, ruptured ectopic pregnancy, pyelonephritis
Usual causes of LLQ pain:
– diverticulitis, pyelonephritis, ruptured ectopic pregnancy, ruptured ovarian cyst, pelvic inflammatory disease
Layers of abdominal wall (from outermost to innermost): skin → Camper’s fascia (superficial fatty layer) → Scarpa’s fascia (deep membranous layer; fuses to fascia lata of thigh below inguinal lig.) → external oblique m. → internal oblique m. → transversus abdominis m. → transversalis fascia → preperitoneal fat → peritoneum
Innervation of abdominal wall:
ventral primary rami of T1-T6, iliohypogastric + ilioinguinal branches of ventral primary rami of L1
Attachments of external oblique muscle
– origin: lower 8 ribs to anterior half of iliac crest
– insertion: xiphoid process, linea alba, ant. half of iliac crest, pubic crest
– muscle fibre direction: inferomedial
– nerve SS: ventral primary rami of T7-T11, iliohypogastric n. (L1), ilioinguinal n. (L1)
– forms external spermatic fascia of spermatic cord; free border of aponeurosis forms inguinal lig.
Attachments of internal oblique muscle
– origin: lateral two-thirds of inguinal ligament, anterior two-thirds of iliac crest, lateral edge of thoracolumbar fascia to rib 12
– insertion: lower three ribs, xiphoid process, linea alba, pubic crest, pectineal line
– muscle fibre direction: superomedial
– nerve SS: ventral primary rami of T7-T11, iliohypogastric n. (L1), ilioinguinal n. (L1)
– forms cremaster muscle and fascia; forms part of conjoint tendon
59Neurovascular bundle lies between internal oblique and transversus abdominis
Attachments of transversus abdominis muscle
– origin: lower six costal cartilages, lateral third of inguinal ligament, anterior two-thirds of iliac crest, lateral edge of thoracolumbar fascia
– insertion: xiphoid process, linea alba, pubic crest, pectineal line
– muscle fibre direction: horizontal
– nerve SS: ventral primary rami of T7-T11, iliohypogastric n. (L1), ilioinguinal n. (L1)
– forms internal spermatic fascia; forms part of conjoint tendon
Attachments of rectus abdominis
– origin: pubic symphysis, pubic crest
– insertion: costal cartilages 5–7
– lateral margin = linea semilunaris
– separated by tendinous intersections; midline separation by linea alba (xiphoid process → pubic symphysis)
– nerve SS: ventral primary rami of T7-T11
Attachments of pyrimidalis
– origin: anterior pubis, pubic symphysis
– insertion: linea alba
– nerve SS: ventral primary ramus of T12
– function: tense linea alba
Arterial SS of ant. abdominal wall
– sup. epigastric a. (one of the terminal branches of int. thoracic a.)
– inf. epigastric a. (branch of ext. iliac a.)
– deep circumflex iliac a. (branch of ext. iliac a.)
Attachments of psoas major muscle
– origin: lat. T12 to L5 vertebral bodies
– pass under inguinal ligament
– insertion: lesser trochanter of femur
– nerve SS: ant. rami of L1–3
– function: flex and laterally rotate thigh
Attachments of psoas minor muscle
– origin: lat. T12 to L1 vertebral bodies
– insertion: pectineal line of pelvic brim
– nerve SS: ant. rami of L1
– function: flex vertebral column
Attachments of quadratus lumborum
– origin: transverse process of L5 + iliac crest
– insertion: transverse processes of L1–4
– nerve SS: ant. rami of T12, L1–4
– function: laterally flex vertebral column
Layers of smooth muscle of stomach
– outer longitudinal
– middle circular
– inner oblique
60 Parts of stomach
– cardia
– fundus
– body
– pyloric antrum (sphincter leading to duodenum)
Cell types in stomach
– chief cells: secrete pepsinogens (digestive E)
– parietal cells: secrete hydrochloric acid + intrinsic factor
– mucus-secreting cells
Arterial supply of stomach
– R. and L. gastric arteries (lesser curvature)
– R. and L. gastroepiploic arteries (greater curvature)
– short gastric arteries (from splenic a.) (SS fundus)
– inferior phrenic arteries
Innervation of stomach
– ant. + post. vagal trunks
Structures that form stomach bed
– part of diaphragm
– L. suprarenal gland
– U. pole of L. kidney
– spleen
– pancreas
– splenic a.
– mesentery of transverse colon
Transpyloric plane (L1)
– midway between jugular notch and pubic symphysis, at tip of ninth costal cartilage, between supracolic and infracolic compartments
– structures crossed by the plane
– fundus of gallbladder (RHS)
– head, neck and body of pancreas
– left and right hilum of kidneys
– origin of superior mesenteric a.
– root of transverse mesocolon
– duodenojejunal flexure
– second part of duodenum
– end of spinal cord
Greater omentum
– developed from dorsal mesentery
– double layer of peritoneum
– from greater curvature of stomach + first part of duodenum → fold back up to enclose transverse colon
Lesser omentum
– double layer of peritoneum
– from liver → lesser curvature of stomach + first part of duodenum
Lesser sac
– space behind stomach (connected to greater sac via epiploic foramen)
61 Epiploic foramen (opening of lesser sac)
– post. relationships: IVC
– ant. relationships: free border of lesser omentum (bile duct + hepatic a.+ portal vein)
– sup. relationships: caudate process of liver
– inf. relationships: first part of duodenum
Retroperitoneal structures
– third part of duodenum
– ascending and descending colon
– pancreas (except tail)
– kidney
– ureter
– adrenal gland
– IVC
– abdominal aorta
– anal canal
Relationships of parts of duodenum
First part of duodenum (superior part)
– ant: quadrate lobe of liver
– post: lesser sac, gastroduodenal artery
– sup: epiploic foramen
– inf: head of pancreas
Second part of duodenum (descending part)
– ant: fundus of gallbladder, right lobe of liver, transverse colon, small intestine
– post: hilum of right kidney, right psoas
– lat: right colic flexure
– med: head of pancreas
Third part of duodenum (inferior part) (longest part of duodenum)
– ant: root of the mesentery
– post: right ureter
– sup: head of pancreas
– inf: jejunum coils
Fourth part of duodenum (ascending part)
– ant: beginning of root of mesentery
– post: medial border of left psoas
Level of umbilicus: L3/4 vertebrae
Linea alba
– fibrous line in the middle separating rectus sheaths on either side
– used in midline incision in surgeries
Rectus sheath
– encloses rectus abdominis and pyramidalis
– upper quarter (above mid-point between umbilicus and pubic symphysis)
external oblique aponeurosis is anterior to rectus abdominis
internal oblique aponeurosis is split to enclose rectus abdominis
transversus abdominis is behind rectus abdominis
62– lower quarter (below mid-point between umbilicus and pubic symphysis)
all aponeuroses pass anterior to rectus abdominis
rectus abdominis lies in contact with transversus fascia
– arcuate line (point where inferior epigastric vessels enter rectus sheath)
midway between umbilicus and pubic symphysis
below arcuate line → aponeuroses run ant. to rectus abdominis
Useful dermatomes to remember
T4 = nipple
T7 = epigastrium
T8 = costal margin
T10 = umbilicus
T12 = pubic symphysis
L1 = inguinal ligament
Structures on posterior surfaces of liver
– abdominal oesophagus
– stomach (fundus)
– right colic flexure
– right kidney
– diaphragm
– inferior vena cava (IVC)
Liver divided into anatomical R. + L. lobes by line drawn from fossa of gallbladder to vena cava
Contents of porta hepatis (portal triad)
– R. and L. hepatic ducts (bile from liver to c. hepatic duct)
– R. and L. branches of hepatic artery (branch of coeliac trunk)
– portal vein
– sympathetic and parasympathetic fibres
– hepatic lymph nodes
Portal vein
= union of splenic vein and superior mesenteric vein at level L2 behind head of pancreas
Tributaries of portal vein
– splenic vein
– inf. mesenteric vein (joins splenic vein behind body of pancreas)
– sup. mesenteric vein (joins splenic vein behind neck of pancreas)
– R. + L. gastric vein
Gallbladder
– stores and concentrates bile
– fundus + body + neck
– connected to cystic duct → joins c. hepatic duct → CBD
Arterial SS of gallbladder: cystic artery (branch from R. hepatic a.)
Venous drainage of gallbladder: cystic vein (drains to portal v.)
Biliary tree
– R. hepatic duct + L. hepatic duct → common hepatic duct
– common hepatic duct + cystic duct → common bile duct
Ligamentum teres = remnant of umbilical vein, found in falciform ligament
63Hepatorenal recess (on RHS) = Morrison’s pouch
Recto-uterine pouch = pouch of Douglas
Ampulla of Vater
= union of common bile duct (CBD) and main pancreatic duct in second part of duodenum
– contains smooth muscle sphincter of Oddi regulating flow of bile and pancreatic juice
Sites of portocaval anastomoses
– lower end of oesophagus (between oesophageal branches of left gastric veins and oesophageal veins draining to azygos vein) → oesophageal varices
– lower end of GI tract (rectum and anal canal) (between superior rectal vein and middle rectal vein) → haemorrhoids
– around umbilicus (between para-umbilical veins and left branch of portal vein) → caput medusa
– retroperitoneal veins
Dorsal pancreatic bud forms most of the pancreatic head, neck, body and tail
Ventral pancreatic bud forms inferior head and uncinate process
Parts of pancreas
– head, neck (level L1), uncinate process, body and tail
Relationships of pancreas
– ant.: transverse mesocolon + transverse colon, stomach
– post.: IVC, portal vein, splenic vein, aorta, L. psoas muscle, L. kidney
Comparison of jejunum and ileum(see Table 4.1) Comparison of jejunum and ileum
Jejunum
Ileum
Proximal two-fifths of small intestine
Located in LUQ
Larger diameter
Thicker wall
Larger plicae circulares
Less prominent arterial arcades
Longer vasa recta
Less mesenteric fat
Does not contain Peyer’s patches
Distal three-fifths of small intestine
Located in RLQ
Smaller diameter
Thinner wall
Smaller plicae circulares
More prominent arterial arcades
Shorter vasa recta
More mesenteric fat
Contains Peyer’s patches
Features of colon
– taenia coli (three bands) (from base of appendix → recto-sigmoid junction)
– haustra
– appendices epiploicae
64 Movements of colon
– segmentation (absorption of water)
– propulsion (movement of bolus)
McBurney’s point
– two-thirds of the distance from the umbilicus to the right anterior superior iliac spine (ASIS)
– site of pain in appendicitis
Various sites where appendix can be found
– retrocaecal (most frequent position)
– pelvic
– retrocolic
– pre-ileal
– post-ileal
– subcaecal
Spleen
– anterior to ribs 9–11
– diaphragmatic surface + visceral surface (where hilus is located)
– functions:
storage of platelets and monocytes
production of antibodies
filtering of red blood cells
– relationships:
inferiorly: L. colic flexure
medially: L. kidney
anteriorly: stomach
posteriorly: diaphragm, L. costodiaphragmatic recess, L. lung
– connected to stomach by gastrosplenic ligament (contains short gastric a. + L. gastroepiploic a.)
– connected to kidney by lienorenal ligament
– arterial SS: splenic a. (from coeliac trunk)
– venous drainage to splenic v. → portal v.
– red pulp (site of red blood cell destruction) + white pulp (lymphoid)
Peritoneal ligaments associated with spleen
(a)Gastrosplenic ligament:
– connects greater curvature of stomach to hilum of spleen
– contains short and left gastroepiploic vessels
Splenorenal ligament:
– connects L. kidney to spleen
– contains tail of pancreas and splenic vessels
Inguinal ligament
– thickened lower border of external oblique aponeurosis
– runs from anterior superior iliac spine (ASIS) to pubic tubercle
– medially forms lacunar ligament (extends up to pectineal line)
Boundaries of the femoral canal (structures pass from abdomen to upper thigh)
– anteriorly: inguinal ligament
65– medially: lacunar ligament
– laterally: iliopsoas
– posteriorly: pectineus
Contents of the femoral canal (lateral to medial)
– femoral nerve
– genitofemoral nerve
– femoral artery
– femoral vein
– femoral ring
Boundaries of femoral ring
– anteriorly: inguinal ligament
– medially: lacunar ligament
– laterally: medial border of femoral vein
– posteriorly: pectineus
Contents of femoral ring
– Cloquet’s node
– lymphatics
Mid-inguinal point
= mid-point of inguinal ligament (halfway between ASIS and pubic tubercle)
Boundaries of inguinal triangle
(also known as Hesselbach’s triangle)
– lateral: inferior epigastric artery
– medial: lateral border of rectus abdominis
– inferior: inguinal ligament
External inguinal ring: defect in external oblique aponeurosis for passage of spermatic cord or round ligament en route to scrotum or labia major
Internal inguinal ring: defect in transversalis fascia for passage of spermatic cord from peritoneal cavity
Boundaries of inguinal canal
– floor: inguinal lig. + lacunar lig.
– roof: transversus abdominis, lowest fibres of internal oblique muscles
– ant.: skin, superficial fascia, aponeurosis of external oblique, internal oblique covers lateral third
– post.: transversalis fascia, conjoint tendon (medial aspect)
Contents of inguinal canal
– men: spermatic cord
– women: round ligament of uterus + genital branch of genitofemoral nerve
Structures in spermatic cord (10 in total)
– vas deferens
– pampiniform plexus of veins
– artery to vas deferens
– vein from vas deferens
– cremasteric artery and vein
– testicular artery
– sympathetic nerve
66– genital branch of genitofemoral nerve (SS cremaster muscle)
– testicular lymphatics
– remnants of processus vaginalis
Branches of abdominal aorta (see Table 4.2) Branches from abdominal aorta
Branches
Vertebral level from which the artery branches
Three anterior visceral branches
Coeliac trunk
T12
Superior mesenteric artery
L1
Inferior mesenteric artery
L3
Three lateral visceral branches
Suprarenal artery
L1
Renal artery
L1/L2
Testicular/ovarian artery
L2
Five lateral abdominal wall branches
Inferior phrenic artery
T12/L1
Four lumbar arteries
L1–4
Three terminal branches
External iliac artery
L4
Internal iliac artery
L4
Median sacral artery
L4
Branches of coeliac trunk
L. gastric a.: passes up to supply lower oesophagus; descends in lesser omentum along lesser curvature of stomach
Splenic a.: runs along U. border of pancreas → passes through lienorenal ligament to hilum of spleen
– short gastric branch: SS fundus of stomach
– L. gastroepiploic branch: SS great curvature of stomach
Hepatic a.: divides into R. + L. hepatic a.
– enters porta hepatis
– R. hepatic a. gives off cystic a.
– gastroduodenal a.: branches into superior pancreaticoduodenal + R. gastroepiploic branches (SS greater curvature of stomach)
– R. gastric a.: SS lesser curvature of stomach; anastomoses with L. gastric a.
Branches of superior mesenteric artery
SS caecum, ascending colon, two-thirds of transverse colon
– inferior pancreaticoduodenal artery
– middle colic artery
– R. colic artery
67– ileocolic artery
– jejunal and ileal arteries
Branches of inferior mesenteric artery
SS distal transverse colon, descending colon, sigmoid, rectum
– L. colic artery
– sigmoid arteries
– superior rectal artery (anastomoses with middle and inf. rectal arteries)
Branches of external iliac artery
– inf. epigastric a. (medial)
– deep circumflex iliac a. (lateral)
Branches of internal iliac artery
(anterior division)
– umbilical a.
– obturator a.
– inf. vesical a.
– middle rectal a.
– internal pudendal a.
– uterine a.
– inf. gluteal a.
– vaginal a.
(posterior division)
– iliolumbar a.
– lat. sacral a.
– sup. gluteal a.
Lumbar plexus
formed within psoas major from ventral rami of L1 to L5
iliohypogastric nerve (L1)
– motor SS to transversus abdominis, internal oblique
– sensory SS to skin of mons pubis
ilio-inguinal nerve (L1)
– sensory SS to skin of groin, scrotum/labium majus, conjoint tendon
lateral cutaneous nerve of thigh (L2 and 3) passes under inguinal ligament
– sensory SS to skin of lateral thigh
genitofemoral nerve (L1 and 2) divides into genital and femoral branches on the anterior surface of psoas
– genital branch: passes through deep inguinal ring into inguinal canal to supply cremaster muscle or labium majus
– femoral branch: passes under inguinal ligament to supply skin of thigh
femoral n. (L2–4)
– motor SS to muscles in ant. compartment of thigh
– sensory SS to skin over ant. thigh, medial leg and medial foot
obturator n. (L2–4)
– motor SS to muscles in med. compartment of thigh
– sensory SS to skin over medial thigh
lumbosacral trunk (L4 and 5)
68 Sacral plexus (lies on piriformis)
– formed from ventral rami of L4 and 5, and S1—4
superior gluteal n. (L4 and 5, and S1)
– motor SS to gluteus medius, gluteus minimus and tensor fasciae latae
inferior gluteal n. (L5, and S1 and 2)
– motor SS to gluteus maximus
n. to piriformis (S2)
– motor SS to piriformis
n. to obturator internus and superior gemellus (L5, and S1 and 2)
– motor SS to obturator internus and superior gemellus
post. cutaneous n. of thigh (S2 and 3)
– sensory SS to skin on post. thigh
perforating cutaneous n. (S2 and 3)
– sensory SS over gluteal fold
sciatic n. (L4—S3)
tibial n.
common fibular n.
pudendal n. (S2—4)
– motor SS to muscles of perineum
– sensory SS to skin of perineum
Rectum
– continuous with sigmoid colon at vertebral level S3
– dilated at lower part (ampulla)
– U. two-thirds covered by peritoneum ant. and U. third covered by peritoneum lat.
– puborectalis forms sling at junction between rectum and anal canal, forming anorectal angle
Relationships of rectum
– ant.: bladder/uterus, prostate and seminal vesicles/vagina
– post.: sacrum and coccyx
Arterial SS of rectum
– sup. rectal a. (from inf. mesenteric a.)
– middle rectal a. (from internal iliac a.)
– distal part: inf. rectal (from internal pudendal a.)
Venous drainage of rectum
– proximal part: inf. mesenteric v. → splenic v. → portal v.
– distal part: iliac v. → IVC
