Anatomy of stomach and its relations v By

Anatomy of stomach and its relations v By Praveen Panicker

STOMACH(ventriculus/gaster) • Most dilated part of GIT • Occupies in the epigastric, umbilical &left • hypochondral areas Occupying a recess bounded by upper abdominal viscera, completed above& anterolateraly by anterior abd wall &diaphragm

Parts of stomach

Stomach • Roughly J Shaped at rest • Size and Shape varies with • a) Volume of food or fluid it contains • b) Position of body • c) Phase of respiration • High and transverse in obese and short persons • Elongated in thin persons

Mean capacity 30 ml 1000 ml 1500 ml 2 OPENINGS S • 2 BORDERS at birth at puberty at adult 2 SURFACE

Gastric orifices • Cardiac orifices • Situated to the left of midline behind 7 th costal cartilage 2. 5 cm from its sternal junction at the level of T 11 • 10 cm from ant abd wall • 40 cm from incisor teeth

Pyloric orifice • Can be identified by prepyloric vein crossing its anterior surface vertically • 1. 2 cm to right of midline in trans pyloric plane provided the body is supine & stomach is empty

Gastric curvatures Lesser curvature • Extends b/w cardiac & pyloric orifice forming right border • Incisura angularis is a notch in the most dependent part , its position varies with gastric distension • Gives attachment to lesser omentum

Greater curvature • 4 to 5 times longer than lesser curvature • Starts at cardiac incisure • Arches upwards & postero laterally & to Lt • Highest convexity is fundus Lt 5 th ICS • Finally turns right to end at the pylorus Attachments • Lt of fundus & adjoining body - gastrosplenic lig. • Beyond this - greater omentum

Gastric surfaces Antero superior Postero inferior • Antero superior surface Lt part of this surface is posterior to Lt costal margin & in contact with diaphragm. It is related to costal attachments of upper fibers of transverse abdominis which separate it from 7 th to 9 th costal margin

• Upper &Left part of this surface becomes postero lateral & is in contact with spleen’s gastric surface • Rt half of this surface is related to Lt & quadrate lobe of liver & ant abd wall • Whole of the surface is covered by peritoneum. • part of greater sac separate it from above structures

• Postero inferior surface Related to STOMACH BED diaphragm Lt suprarenal gland upper part of front of left kidney splenic artery anterior pancreatic surface colic flexure together with transverse mesocolon

• This surface is also covered by peritoneum except near the cardiac orifice where a small triangular area contacts diaphragmatic crus

INTERIOR OF STOMACH • A large globular Lt part & a narrow tubular Rt part

Gastric micro structure • Mucosa • Sub mucosa • Muscularis externa • Serosa • Mucosa • Thick, smooth surface, velvetty • Reddish brown to pink in colour

• In contracted state • • • mucosa is folded to form RUGAE. They are Longitudinal & more marked towards pyloric & greater curvature Actually they are large folds in sub mucosal connective tissue Obliterated when stomach is distended

MUCOSA • Epithelium • Lamina propia • Muscularis mucosa

• Epithelium • Appears as honey combed due to small gastric pits (foveola). Base of gastric pits (foveola) receives gastric glands which extend deep into lam propria Epithelium simple columnar mucous cells

Gastric glands cardiac Principal pyloric Principal ØFound In body & fundus Cardiac glands üSituated near the cardia Pyloric glands numerous mucous & entero endocrine cells predominate

Principal Ø Highly differentiated Ø Found In body & fundus Are made of different types of cells Chief Parietal Mucous Stem Entero endocrine

these cells undergo constant replacement (3 to 7 days)

Cardiac glands üSituated near the cardia üMucous secreting cells predominate Pyloric glands ü numerous mucous & entero endocrine cells predominate

Lamina propria Found in b/w the glands § Contain gastric follicles which are aggregations of lymphoid tissue § A periglandular vascular plexus is also present

ØMuscularis mucosa • Inner circular • Outer longitudinal • Ext circular in some places ØSub mucosa • Loose connective tissue • Collagen, elastin, sub mucosal plexus of stomach

Muscularis externa From within outwards layers are Ø Oblique fibres ØCircular Ølongitudinal

ØOblique fibres • Limited to gastric • body Most developed near the cardiac orifice ØCircular fibres • Form a uniform layer • external to oblique fibres At the pylorus form annular pyloric sphincter

Longitudinal fibres • Arranged in 2 groups • 1 st set radiates from cardiac orifice, best • developed along the curvatures 2 nd set commence in the body, passes to right, some fibres pass to duodenum, deeper fibres interlace with pyloric sphincter ØMuscle action upper region of stomach forms an area of storage, lower region has a pump like axn mixing & delivering the contents to duodenum

Gastric vessels • Left gastric artery • Rt gastric artery • Lt & Rt gastro epiploic • artery Short gastric artery

• These form anastomosis in all layers, forming sub serosal, intramuscular & sub mucosal plexus ; from these anterior & posterior branches arise • Mucosal arteries usually arise from sub mucosal plexus. But along the curvatures they arise directly from sub serosal arteries without anastomosing with other plexus. So that these are more vulnerable to ischemic injury

v pyloric region is supplied by pyloric arteries (br of rt gastric & gastroepiploic) where they form a submucosal plexus. They also anstomose with Duodenal & gastric arteries v. Arterioles from Submucosal arterial plexus penetrate the mucosa & branch to form capillary beds which drain to sub mucosal venous plexus

v This rich lumen directed blood flow enables. HCO 3 - generated basally by the parietal cells as a counterpart of their secretion of acid to be carried into apical part in order to protect the cells from acid damage v Fenestrated capillaries also facilitate delivery of HCO 3 v In antrum where HCO 3 - secreting parietal cells are few blood supply is increased in order to facilitate removal of acid

Gastric nerves • Parasympathetic [ vagus] • Anterior br (frm rt vagus) Posterior br ( frm Lt vagus) sympathetic

c Anterior nerve c Gastri Pylori ØGastric nerve radiates on • anterior surface of body &fundus One br which is larger near lesser curvature is called greater anterior gastric N (anterior nerve of latarjet)

Pyloric br • 2 in no: one which • traverses the lesser omentum almost horizontally to Rt, then turns down on the left side of hepatic artery to reach pylorus Other arises from greater anterior gastric nerve & passes obliqly to pylorus

v. Posterior Gastric coeliac v. Gastric • Radiate over the posterior surface of body & fundus upto pyloric antrum • Largest pass along lesser curvature Greater posterior gastric nerve v. Coeliac • Pass to coelic plexus

Sympathetic supply • From Coeliac plexus Inconstant brs Hepatic plexus Lt phrenic plexus Lt thorasic nerve, thorasic & lumbar trunks ØForm Sub mucosal plexus of Meissner Myentric plexus of Auerbach

Lymphatics are continous with that of oesophagus & duodenum ØArranged in 4 groups • 1 st gp accompany Lt gastric artery. Receives a large area on both gastric surface. They end in Lt gastric nodes • 2 nd gp short gastric & Lt gastro epiploic arteries. Drains Left of the vertical from oesophagus. End in pancreaticosplenicnode

3 rd gp drains Rt half of grtr curvature as far as pylorus. End in Rt gastro epiploic nodes which drain to pyloric nodes 4 th gp Pylorus Drains to hepatic, pyloric & Lt gastric nodes

LYMPH NODES ON POTERIOR SURFACE

Although these vessels communicate, their valves direct lymph from • Rt part of stomach towards lesser curvature. From Lt side to greater curvature

Important Lymph node stations(Japanese)

PHYSIOLOGY • Parietal cells HCL & IF • Chief cells pepsinogen • ECL histamine

Gastric secretions • 2500 ml/day • Contents • cations anions pepsin lipase Mucus IF Na, K, Mg, H+ Cl, HPO 2, so 4

MUCOSAL BARRIER • Formed by mucous & HCO 3 • Mucous made of glycoprotein forms a flexible gel coat • They also protect duodenal mucosa • Their stimulation is augmented by prostaglandin • Trefoid peptides also provide protection

HCL SECRETION ØH+ -K+ ATPase in the apical membrane of parietal cells pumps H+ against concentration gradient. Ø When stimulated tubulo vesicular structures inside the parietal cell move to apical membrane & fuse with it thus inserting more H+ -K+ ATPase (which are present in the walls of tubulo vesicular structures )

Regulation of acid secretion H+ -K+ ATPase is activated by Histamine Ach secretogouges Gastrin which act through their receptors Histamine play the dominant role Ach & Gastrin act partly directly & partly indirectly by releasing histamine

Regulation of gastric secretion Cephalic influence Gastric influence Intestinal influence

Gastric motility & emptying • The pacemaker of gastric muscle action is called gastric pacemaker cells of Cajal situated in the FUNDUS of the stomach • They are located in the outer circular muscle layer near the myentric plexus • They initiate the basic electrical rhythm

Gastric motility & emptying • • When food enters the stomach fundus & upper part of body relax & accommodate the food called receptive relaxation This is vagally mediated & triggered by movement of pharynx & oesophagus Soon after, peristaltic waves settle in distal stomach, mixing & grinding the food permitting semi liquid portion to enter the duodenum

• The contraction of distal stomach caused by • • each peristaltic waves is called antral systole & can last upto 10 seconds. In regulation of gastric emptying antrum, pylorus & upper duodenum act as a single unit. In antrum partial contraction ahead of advancing gastric contents prevent solid masses from entering duodenum

• Regurgitation from duodenum will not occur because contraction of pyloric segment tends to persist longer than that of duodenum • Hunger contractions Gastric contractions in b/w meals sometimes be felt, sometimes mildly painful

• Rate at which stomach empties into duodenum depends on Type of food Oncotic pressure of food Type of food rich in carbohydrate leaves the stomach in few hrs, protien rich food leaves more slowly, slowest for fat. Oncotic pressure of food Hyperosmolarity of duodenal contents gastric emptying

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