Abdomen V - Stomach Flashcards
stomach
expanded part of the alimentary tract between the esophagus + small intestine
In most people, the shape of the stomach resembles___________?
What causes variations in the position of the stomach from person to person?
What causes variations in the position of the stomach in an individual?
normally = the letter J
person to person = body type
individual variation:
- diaphragmatic movements during respiration
- stomach’s contents
- position of the person.
An empty stomach is only slightly larger than the large intestine;
How much food can it hold when expanded?
How much can a newborn’s stomach hold?
2 - 3 L of food
newborn = up to 30 mL of milk
What are the functions & specializations of the stomach?
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)
The gastric juice gradually converts a mass of food into what?
Where is it passed to?
**chyme - **a semiliquid mixture
(passes quickly into duodenum)
What are the 4 parts of the stomach?
- cardia
- fundus
- body
- pyloric part (antrum + canal)
cardia
the part of the stomach surrounding the cardial orifice
fundus
- 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
The superior part of the fundus usually reaches what level?
left 5th intercostal space
What is located between the esophagus and the fundus?
cardial notch
The fundus may be dilated by …?
gas
fluid
food
combination of these
body of stomach
major part of the stomach between the fundus and the pyloric antrum
pyloric part
- funnel-shaped outflow region of the stomach
- pyloric antrum= wide part; leads into pyloric canal = narrow part
The pylorus (distal, sphincteric region of the pyloric part) is a marked thickening of the circular layer of smooth muscle.
What does this control?
discharge of the stomach contents through the pyloric orifice into the duodenum
When does intermittent emptying of the stomach occur?
when intragastric pressure overcomes the resistance of the pylorus
What is the normal state of the stomach?
What is an exception to this?
tonically contracted so that the pyloric orifice is reduced
*except when emitting chyme*
What process passes the chyme through the pyloric canal + orifice into the small intestine for further mixing, digestion, and absorption?
When does this occur?
gastric peristalsis
- at irregular intervals
What are the 2 curvatures of the stomach?
lesser curvature
greater curvature
Lesser curvature
forms the shorter concave border of the stomach
Greater curvature
forms the longer convex border of the stomach
angular incisure (notch)
- sharp indentation approx. 2/3 the distance along lesser curvature
- indicates the junction of the body + pyloric part of the stomach
In a live patient, the interior of the stomach is covered by …?
What protection does this provide?
- a continuous mucous layer
- protects its surface from the gastric acid
gastric folds (or gastric rugae)
- 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)
A gastric canal (furrow) forms temporarily during swallowing between what structures?
How can it be observed?
- longitudinal gastric folds of the mucosa along the lesser curvature
- observed radiographically + endoscopically
Why does the gastric canal form?
What passes through this canal?
- 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)
What is the stomach covered by?
What area is the exception to this?
peritoneum
- except = where blood vessels run along its curvatures + in a small area posterior to the cardial orifice
The two layers of the lesser omentum extend around the stomach and leave its greater curvature as…?
as the greater omentum
Anteriorly, the stomach is related to what 3 structures?
diaphragm
left lobe of liver
anterior abdominal wall
Posteriorly, the stomach is related to what 2 structures?
The posterior surface of the stomach forms most of the …?
- omental bursa and the pancreas
- anterior wall of the omental bursa
From superior to inferior, the stomach bed is formed by what 6 structures?
left dome of diaphragm
spleen
left kidney + suprarenal gland,
splenic artery
pancreas
transverse mesocolon + colon
Pancreatic pseudo-cysts and abscesses in the omental bursa may do what to the stomach?
How can physicians view this change?
push the stomach anteriorly
- view via lateral radiographs of stomach or CT studies
Following pancreatitis (inflammation of the pancreas), the posterior wall of the stomach may adhere to …?
Why does this occur?
- posterior wall of omental bursa that covers the pancreas
- occurs because of close relationship b/t posterior wall of stomach + pancreas
Hiatal Hernia
- protrusion of part of the stomach into the mediastinum
- through esophageal hiatus of the diaphragm
(often distressful and cause pain)
What are 2 main types of hiatal hernias?
Which people are these most likely to occur in?
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)
Paraesophageal hiatal hernia
- 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
Sliding hiatal hernia
-
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
Congenital Diaphragmatic Hernia
part of the stomach + intestine herniate through a large posterolateral defect in diaphragm
(foramen of Bochdalek)
- approx. 1 in 2200 newborn infants
- developmental abnormalities
Congenital Diaphragmatic Hernia:
With abdominal viscera in the limited space of the prenatal pulmonary cavity, the lungs (especially the left lung) does not have room to develop.
What is the mortality rate in these cases?
high = approximately 76%
(b/c of consequent pulmonary hypoplasia)
The stomach has a rich arterial supply arising from ____________?
the celiac trunk and its branches
Most blood is supplied to the stomach by anastomoses formed -
- Along the lesser curvature by the right and left gastric arteries
- Along the greater curvature by the right and left gastro-omental arteries
- The fundus and upper body receive blood from the short and posterior gastric arteries
The gastric veins parallel the arteries in position and course.
The right and left gastric veins drain into what vein?
the portal vein
The short gastric veins + left gastro-omental veins drain into the _____________?
splenic vein
The right gastro-omental vein empties in the __________?
superior mesenteric vein
Which 2 veins join to form the portal vein?
splenic vein + superior mesenteric vein
What vein is used by surgeons for identifying the pylorus?
Where is it located?
prepyloric vein
(because this vein is obvious in living persons)
- ascends over the pylorus to the right gastric vein
The gastric lymphatic vessels accompany the arteries along the greater and lesser curvatures of the stomach. They drain lymph from which surfaces toward its curvatures?
Which lymph nodes are located here?
- anterior + posterior surfaces
- gastric and gastro-omental lymph nodes
gastric lymph nodes drain from what area of the stomach?
superior 2/3 of the stomach
(along the right and left gastric vessels)
pancreatico-splenic lymph nodes drain from what areas of the stomach?
fundus + superior part of the body of the stomach
(drains along the short gastric arteries and left gastro-omental vessels)
Lymph from the right 2/3 of inferior third of the stomach drains along the right gastro-omental vessels to which lymph nodes?
pyloric lymph nodes
Lymph from the left 1/3 of greater curvature drains along the short gastric + splenic vessels to what lymph nodes?
pancreaticoduodenal lymph nodes
The parasympathetic nerve supply of the stomach is from the ______________ vagal trunks and their branches?
where do they enter the abdomen?
anterior and posterior
- esophageal hiatus
The anterior vagal trunk (mainly from left vagus nerve - CN X), lies on the anterior surface of the esophagus.
It runs toward which area of the stomach?
lesser curvature
The larger posterior vagal trunk (mainly from right vagus nerve), enters the abdomen on the posterior surface of the esophagus.
As it passes toward the lesser curvature of the stomach, what does it gives off?
a celiac branch
(runs to the celiac plexus)
The sympathetic nerve supply of the stomach comes from which spinal nerves?
T6 - T9 segments of the spinal cord
The sympathetic nerves of the stomach pass to the celiac plexus through the which nerve?
Which plexuses are they distributed through?
greater splanchnic nerve
plexuses around the gastric + gastro-omental arteries
Pylorospasm
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
Congenital Hypertrophic Pyloric Stenosis
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*
Carcinoma of the Stomach
- malignant tumor may be palpable (body or pyloric)
- gastroscopy to view stomach
- removal of lymph nodes poses surgical issues
gastroscopy
can inspect mucosa of the air-inflated stomach
- observe gastric lesions and take biopsies
In the case of stomach carcinoma, the lymp nodes along the splenic vessels can be excised by removing what structures?
spleen
gastrosplenic + splenorenal ligaments
body + tail of pancreas
Carcinoma-involved nodes along the gastro-omental vessels can be removed by resecting the greater omentum.
The removal of the which lymph nodes prooves more difficult?
aortic nodes
celiac nodes
nodes around head of pancreas
Gastrectomy
(Total gastrectomy vs. Partial gastrectomy)
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*
Arterial anastomoses supplying the stomach are clinically beneficial during gastrectomies because…?
one or more arteries may be ligated during procedure
(without seriously affecting blood suppling remaining stomach)
Cancer frequently occurs in the what region of the stomach?
It is important to remove which lymp nodes in these cases?
pyloric region
Important to remove:
- pyloric lymph nodes
- right gastro-omental lymph nodes
(receiving lymph drainage from this region)
As stomach cancer advances, lymphogenous dissemination of malignant cells involves which important lymph nodes?
celiac lymph nodes
(all gastric nodes drain here)
Gastric Ulcers
- 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
Individuals with gaastric ulcers often have gastric acid secretion rates that are _____________ times higher than normal between meals.
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*
How does the Helicobacter pylori (H. pylori) effect the stomach, causing ulcers?
What can happen if ulcers erode into gastric arteries?
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*
secretion of acid by parietal cells of the stomach is largely controlled by the vagus nerves. What procedure is performed in some people with chronic or recurring ulcers to reduce the production of acid?
Vagotomy (surgical section of the vagus nerves)
*may also be in conjunction with resection of the ulcerated area*
truncal vagotomy
(surgical section of the vagal trunks)
- rarely performed because the innervation of other abdominal structures is also sacrificed
selective gastric vagotomy
- stomach is denervated but the vagal branches to the pylorus, liver and biliary ducts, intestines, and celiac plexus are preserved
selective proximal vagotomy
- 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
A posterior gastric ulcer may erode through what structures?
This results in …?
- stomach wall into the pancreas
- referred pain to the back
In a posterior gastric ulcer, erosion of the splenic artery results in what?
severe hemorrhage into the peritoneal cavity
Pain impulses from the stomach are carried by what type of fibers that accompany sympathetic nerves?
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*
Visceral Referred Pain:
Why is pain from a gastric ulcer referred to the epigastric region?
- 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)
The surface markings of the stomach in the supine position include:
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 *
Where are the surface marking for the pyloric part of the stomach in the supine position + the erect position?
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
