Anatomy: Abdomen V - Stomach

expanded part of the alimentary tract between the esophagus + small intestine

normally = the letter J

person to person = body type

individual variation:

• diaphragmatic movements during respiration

• stomach’s contents

• position of the person.

2 - 3 L of food

newborn = up to 30 mL of milk

specialized for:

• accumulation of ingested food

• chemical + mechanical preparation of food for digestion

• passage of food into the duodenum

functions:

• enzymatic digestion

(food blender and reservoir)

chyme - a semiliquid mixture

(passes quickly into duodenum)

• 
  cardia

• fundus

• body

• pyloric part (antrum + canal)

the part of the stomach surrounding the cardial orifice

• dilated superior part of the stomach that is related to the left dome of the diaphragm

• limited inferiorly by the horizontal plane of the cardial orifice

left 5th intercostal space

cardial notch

gas

fluid

food

combination of these

major part of the stomach between the fundus and the pyloric antrum

• funnel-shaped outflow region of the stomach

- pyloric antrum= wide part; leads into pyloric canal = narrow part

discharge of the stomach contents through the pyloric orifice into the duodenum

when intragastric pressure overcomes the resistance of the pylorus

tonically contracted so that the pyloric orifice is reduced

except when emitting chyme

gastric peristalsis

• at irregular intervals

lesser curvature

greater curvature

forms the shorter concave border of the stomach

forms the longer convex border of the stomach

• sharp indentation approx. 2/3 the distance along lesser curvature

• indicates the junction of the body + pyloric part of the stomach

• a continuous mucous layer

• protects its surface from the gastric acid

• contraction = gastric mucosa thrown into longitudinal ridges

• are most marked toward the pyloric part and along the greater curvature

- folds diminish and obliterate as the stomach is distended (fills)

• longitudinal gastric folds of the mucosa along the lesser curvature

• observed radiographically + endoscopically

• because of the firm attachment of the gastric mucosa to the muscular layer

(no oblique layer at this site)

• Saliva + small quantities of masticated food and other fluids

(to the pyloric canal when the stomach is mostly empty)

peritoneum

• except = where blood vessels run along its curvatures + in a small area posterior to the cardial orifice

as the greater omentum

diaphragm

left lobe of liver

anterior abdominal wall

• omental bursa and the pancreas

- anterior wall of the omental bursa

left dome of diaphragm

spleen

left kidney + suprarenal gland,

splenic artery

pancreas

transverse mesocolon + colon

push the stomach anteriorly

• view via lateral radiographs of stomach or CT studies

• posterior wall of omental bursa that covers the pancreas

• occurs because of close relationship b/t posterior wall of stomach + pancreas

• protrusion of part of the stomach into the mediastinum

• through esophageal hiatus of the diaphragm

(often distressful and cause pain)

paraesophageal hiatal hernia + sliding hiatal hernia

• more common after middle age

(possibly b/c of weakening of muscular part of diaphragm + widening of esophageal hiatus)

• pouch of peritoneum, often containing part of the fundus, extends through esophageal hiatus anterior to the esophagus

• less common

• cardia remains in its normal position

(cardial orifice is in its normal position)

• usually no regurgitation of gastric contents

• abdominal part of the esophagus, cardia + parts of the fundus slide superiorly through the esophageal hiatus into the thorax
  (esp. when the person lies down or bends over)

• clamping action of the right crus of the diaphragm on the inferior end of the esophagus is weak

= some regurgitation of stomach contents into esophagus

part of the stomach + intestine herniate through a large posterolateral defect in diaphragm

(foramen of Bochdalek)

• approx. 1 in 2200 newborn infants

• developmental abnormalities

high = approximately 76%

(b/c of consequent pulmonary hypoplasia)

the celiac trunk and its branches

1. Along the lesser curvature by the right and left gastric arteries

2. Along the greater curvature by the right and left gastro-omental arteries

3. The fundus and upper body receive blood from the short and posterior gastric arteries

the portal vein

splenic vein

superior mesenteric vein

splenic vein + superior mesenteric vein

prepyloric vein

(because this vein is obvious in living persons)

• ascends over the pylorus to the right gastric vein

• anterior + posterior surfaces

• gastric and gastro-omental lymph nodes

superior 2/3 of the stomach

(along the right and left gastric vessels)

fundus + superior part of the body of the stomach

(drains along the short gastric arteries and left gastro-omental vessels)

pyloric lymph nodes

pancreaticoduodenal lymph nodes

anterior and posterior

• esophageal hiatus

lesser curvature

a celiac branch

| (runs to the celiac plexus)

T6 - T9 segments of the spinal cord

greater splanchnic nerve

plexuses around the gastric + gastro-omental arteries

Spasmodic contraction of the pylorus sometimes occurs in infants (usually between 2 and 12 weeks of age)

• failure of pyloric canal smooth muscle fibers to relax normally

• food does not pass easily from the stomach into the duodenum

• stomach becomes overly full = vomiting

thickening of the smooth muscle in the pylorus

(approx. 1 in 150 male infants; 1 in 750 female infants)

• elongated overgrown pylorus is hard + severe stenosis of pyloric canal = resisting gastric emptying

• proximal part of stomach becomes secondarily dilated b/c of the pyloric obstruction

• - cause unknown; possibly genetic = high incidence in infants of monozygotic twins*

• malignant tumor may be palpable (body or pyloric)

• gastroscopy to view stomach

• removal of lymph nodes poses surgical issues

can inspect mucosa of the air-inflated stomach

• observe gastric lesions and take biopsies

spleen

gastrosplenic + splenorenal ligaments

body + tail of pancreas

aortic nodes

celiac nodes

nodes around head of pancreas

Total = removal of the entire stomach (uncommon)

Partial = removal of part of the stomach

( ex. region of the stomach involved by a carcinoma)

usually also requires removal of all involved regional lymph nodes

one or more arteries may be ligated during procedure

(without seriously affecting blood suppling remaining stomach)

pyloric region

Important to remove:

• pyloric lymph nodes

• right gastro-omental lymph nodes

(receiving lymph drainage from this region)

celiac lymph nodes

| (all gastric nodes drain here)

• open lesions of the stomach mucosa

(peptic ulcers = lesions of pyloric canal or duodenum mucosa)

• most in stomach/duodenum associated with infection of Helicobacter pylori (H. pylori) bacterium (9 out of 10)

• severe chronic anxiety = predisposed to peptic ulcers

as much as 15 times higher

*thought that high acid in stomach/duodenum overwhelms the bicarbonate normally produced by duodenum --->

reduces effectiveness of mucous lining = vulnerable to H. pylori*

bacteria erodes protective mucous lining of stomach

= inflamed mucosa; vulnerable to effects of gastric acid + digestive enzymes (pepsin) produced by the stomach

if gastric arteries erode = can cause life-threatening bleeding

Vagotomy (surgical section of the vagus nerves)

may also be in conjunction with resection of the ulcerated area

(surgical section of the vagal trunks)

• rarely performed because the innervation of other abdominal structures is also sacrificed

• stomach is denervated but the vagal branches to the pylorus, liver and biliary ducts, intestines, and celiac plexus are preserved

• attempts to denervate even more specifically the area in which the parietal cells are located

• hoping to affect the acid-producing cells while sparing other gastric function (motility) stimulated by the vagus nerve

• stomach wall into the pancreas

• referred pain to the back

severe hemorrhage into the peritoneal cavity

visceral afferent fibers

The pain of a recurrent peptic ulcer may persist after complete vagotomy, whereas patients who have had a bilateral sympathectomy may have a perforated peptic ulcer and experience no pain

• b/c stomach is supplied by pain afferents that reach the T7 and T8 spinal sensory ganglia + spinal cord segments through the greater splanchnic nerve

• brain interprets pain as though irritation occurred in the skin of the epigastric region

(supplied by the same sensory ganglia and spinal cord segments)

Cardial orifice = posterior to 6th left costal cartilage, 2 - 4 cm from the median plane at the level of the T11 vertebra

Fundus = posterior to left 6th rib in plane of the mid clavicular line

Greater curvature = passes inferiorly to left as far as 10th left cartilage before turning medially to reach pyloric antrum

Lesser curvature = passes from right side of cardia to pyloric antrum; most inferior part of curvature marked by angular incisure (lies just left of midline)

pyloric part of stomach *

supine position = level of the 9th costal cartilages + level of L1 vertebra; pyloric orifice is approximately 1.25 cm left of midline

erect position = right side; location varies from L2 through L4 vertebra