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GASTRO-INTESTINAL

Oro-pharynx

Macro identification - see moore p834

Tongue – three parts – root, body, tip.

• Root is posterior part, attached mainly to floor of mouth.
• Tongue functions – mastication, taste, deglutition, articulation, oral cleansing, but main functions are squeezing food into pharynx (swallowing) and speaking.
• Muscles of tongue – 4 extrinsic, 4 intrinsic - supplied by CNXII (hypoglossal) mainly (vagus nerve for one muscle)
  • Extrinsic – genioglossus, hyoglossus, styloglossus,palatoglossus
  • Intrinsic – superior longitudinal muscle of tongue, inferior longitudinal of tongue, transverse muscle of tongue, vertical muscle of tongue
  • NB: most tongue muscles originate from occipital myotomes.
• Sensory innervation of tongue
  • anterior two-thirds = lingual nerve
  • posterior one-third = lingual branch of glossopharyngeal nerve (CNIX)
• Arterial supply – lingual artery (from external carotid), and deep lingual veins
• Lymphatic drainage – submental, submandibular, inferior deep cervical, superior deep cervical lymph nodes.

Oesophagus:

• Relations with mediastinal structures:

Oesophagus follows curve of vertebral column as it descends through neck and posterior mediastinum, piercing diaphragm. Abdominal part forms groove in left lobe of liver, entering stomach at cardiac orifice, postterior to seventh left costal cartilage. Here, esophagus covered anteriorly and laterally by peritoneum, encircled by esophageal plexus of nerves. Right border continuous with lesser curvature of stomach, left border separtaed from stomach fundus by cardiac notch.

NB: relations in cervical area:

• Esophagus lies between trachea and anterior longitudinal ligament on surfaces of vertebrae.
• On right side – esophagus in contact with cervical pleura at root of neck
• On left side – posterior to subclavian artery, thoracic duct lies between pleura and esophagus

• Surface and radiological anatomy –
  • Barium swallow in esophageal cancer can show persistent fillling defect owing to narrowing of esophageal lumen by cancer – see more p160

Peritoneum

• See Moore p158 – peritoneal cavity divided into two peritoneal sacs, greater and lesser. Incision through anterior abdominal wall enters greater peritoneal sac. Lesser sac (omental bursa) lies posterior to the stomach, lesser omentum, and liver.
• OMENTUM – this is double-layered sheet or fold of peritoneum. Ithey attach stomach to body wall or other abdominal organs
  • Lesser omentum – connects lessser curvature of stomach and proximal part of duodenum to liver. It lies posterior to left lobe of liver, and attached to liver in the fissure for the ligamentum venosum and parta hepatis (transvers fissure on inferior surface)
  • Greater omentum – fat-laden fold of peritoneum hanging down from gerater curvature of stomach, connects stomach with diaphragm, spleen, and transverse colon. The double layer usually fuses during fetal period, thus greater omentum composed of 4 layers of peritoneum.
• Intraperitoneal and extraperitoneal organ location-
  • Moore p153 – Retroperitoneal – kidneys, duodenum
  • Covered on each side with peritoneum – ascending colon, pancreas (posterior to omental bursa
  • Have mesentery (or ligaments joining it to other organs)– stomach, jejunum, spleen, liver

STOMACH

• Terminology of parts – Moore p164
• Blood supply –
  • Arteries -
    • Stomach supplied by all three branches of celiac trunk:
    • 1) left gastric artery (lesser curvature)
    • 2) branches of common hepatic artery – right gastric and right gastro-omental arteries
    • 3) branches of splenic artery – left gastro-omental and short gastric arteries
  • Veins –
    • Gastric veins parallel arteries in position and course and drain into portal system of veins. Considerable variation in the way they do so.
  • Lymphatic drainage –
    • Lymph vessels accompany arteries along greater and lesser curvatures.
    • See Moore p170. 4 major areas of lymphatic drainage:
      • 1) lesser curvature (largest)
      • 2) right part of greater curvature (next largest)
      • 3) left part of greater curvature
      • 4) part of lesser curvature related to pylorus
    • In general, lymph is drained from anterior and posterior surfaces of stomach toward its curvature, (gastro-omental lymph nodes) then efferent vessels from these nodes accompany large arteries to celiac lymph nodes (around celiac trunk).

• Histology
  • Mucosa of stomach has tubular glandular form, but three distinctly different histological zones:
    • Cardia – mucus-secreting glands surrounding entrance of esophagus
    • Fundus and body –major histo region, consisting of glands secreting acid (parietal) –peptic (chief) gastric juices as well as protective mucus.
    • Pylorus secrete mucus (2 different types) and endocrine cells secrete gastrin.
  • In a single gastric gland (fundus and body) there are:
    • 2 types of mucus cells - one covering luminal surface of stomach, and neck mucous cells in gland necks
    • parietal cells – most numerous in middle portion (isthmus) of glands (eosinophilic cytoplasm, centrally located nucleus)
    • chief cells – bases of gastric glands – condensed, basally located nuclei, strongly basophilic granular cytoplasm
• lesser sac is the omental bursa, posterior to stomach
• stomach bed
  • formed by posterior wall of omental bursa and retropertioneal structures between it and posterior abdominal wall (pancreas and left kidney) superiorly, stomach bed contains part of diaphragm, spleen, left suprarenal gland.Inferiorly, body and tail of pancreas, and transverse mesocolon.

Intestine

• macro features of small and large intestine:
  • too easy – but NB: to distinguish large intestine from small intestine:
    • three thickened bands of longitudinal muscle – teniae coli
    • sacculations of wall between teniae, haustra
    • small pouches of omentum filled with fat – appendices epiploicae.
• Duodenum
  • Arterial supply – superior and inferior pancreaticoduodenal arteries
  • Venous – veins follow arteries draining into portal venous system (eg superior mesenteric vein, portal vein directly)
  • Lymphatic – pancreaticoduodenal lymph nodes along splenic artery, pyloric lymph nodes along gastroduodenal artery. Then to celiac lymph nodes.Inferiorly, also superior mesenteric nodes.
• Jejunum and ileum
  • Arterial – superior mesenteric artery
  • Venous – superior mesenteric vein (accompanies the artery)
  • Lymphatic drainage – lacteal to plexus in SI walls to mesenteric lymmph nodes. à superior mesenteric lymph nodes.
• Cecum and appendix
  • Arterial – ileocolic artery (from superior mesenteric ), appendix by appendicular artery (from ileocolic artery)
  • Venous – ileocolic vein (superio mesneteric vein)
  • Lymphatic – lymph vessels from here pas to ileocolic lymph nodes along ileocolic artery. Then to superior messenteric lymph nodes.
• Ascending colon
  • Arterial – ileocolic and right colic arteries (superior mesenteric)
  • Venous – ileocolic and right colic veins (superior mesenteric vein
  • Lymph – paracolic and epicolic nodesà superior mesenteric lymph nodes
• Transverse colon
  • Arterial – middle colic artery (superior mesenteric), right and left colic arteries. NB left colic from inferior mesenteric.
  • Venous – superior mesenteric vein.
  • Lymph – nodes here to superior mesenteric nodes
• Descending colon
  • Arterial – left colic and superior sigmoid arteries (inferior mesenteric)
  • Venous – inferior mesenteric vein
  • Lymph – intermediate colic nodes (along left colic artery) à inferior mesenteric nodes around inferior mesenteric artery. NB Left colic flexure also to superior mesenteric lymph nodes.
• Sigmoid colon
  • Arterial – sigmoid arteries (inferior mes.)
  • Venous – inferior mesenteric vein
  • Lymph – intermediate colic nodes (along branches of left colic arterries) à inferior mesenteric lymph nodes around inferior mesenteric artery.

LIVER

• Lobes – Moore p192 Right (Caudate – posterior, quadrate-anterior), Left lobe
• NB: each lobe(right and left) has own arterial, venous supply and biliary drainage.

• Surface/radiological anatomy –

• Liver – rises to highest point posterior to right fifth rib, inferior to nipple . liver in right upper quadrant, occupying right hypochondriac region, parts of epigastric and left hypochonriac regions.
• Liver moves with respiration because it is connected to diaphragm by falciform and coronary ligaments.

• Blood supply –

• Arterial - Right and left lobes receive right and left branches of portal vein, and hepatic artery proper (which branches into right and left heaptic arteries)

• Venous – union of central veins in lobules à hepatic veins à inferior vena cava

• Histology – see Stevens Histology Figures 12.2, 12.7

Gall bladder and bile ducts

• Gall bladder
  • Piriform sac lies along right edge of quadrate lobe in gallbladder fossa (visceral surface). Concentrates bile secreted by liver and stores it in intervals between active phases of digestion. Usually holds 30-60ml of bile.
• Relations of common bile duct –
  • Runs in free edge of lesser omentum with hepatic artery and portal vein. Passes inferiorly, anterior to omental foramen, anterior to right edge of partal vein and on right side of hepatic artery.
  • Passes posterior to superior part of the duodenum and head of pancreas.
  • Posterior to duodenum, lying to right of gastroduodenal artery.
  • Then contacts pancreatic duct, both running obliquely through wall of duodenum, uniting to form the hepatopancreatic ampulla.
• Surface/radiological anatomy –
  • When gallbladder enlarged and distended, often palpable through anterior abdominal wall at level of ninth costal cartilage. Site of max. tenderness in acute cholecystitis.
  • If gallbladder enlarged greatly, can be seen to move inferiorly during inspiration as it is pushed down with liver by diaphragm.
• Arterial supply –
  • Cystic artery arising from right hepatic artery

Pancreas

• macroscopically: head, neck, body and tail
• relations
  • head of pancreas within curve of duodenum, embraced by it. Posterior is IVC, right renal vessels, left renal vein.
  • Uncinate process rests against aorta posteriorly.
  • Neck of pancreas grooved posteriorly by superior mesenteric vessels. Anterior surface covered with peritoneum and adjacent to pylorus of stomach. Posterior to neck, portal vein is formed from superior mesenteric vein and splenic vein.
  • Body of pancreas – extends left across aorta dn superior lumbar vertebrae, posterio to omental bursa. Three surfaces – anterior, posterior, inferior.
    • Anterior – peritoneum (stomach bed)
    • Posterior – no peritoneum when in contact with aorta, superior mesenteric artery, left adrenal and left kidney. Body of pancreas intimately related to splenic vein. Anterior to aorta, pancreas body is between celiac trunk and superior mesenteric artery.
    • Inferior
  • Tail of pancreas – passes between two layers of splenorinal ligament with splenic vessels. End usually contacts hilum of spleen.
• Blood supply of pancreas
  • Arterial - Splenic and pancreaticoduodenal arteries.
  • Venous – pancreatic veins drain into portal, splenic, superior mesenteric veins, (most into splenic vein).