19. Anatomy, Histology, &, Embryology of the Stomach

. Anatomy, Histology, & Embryology of the Stomach

*Intraperitoneal, and part of foregut

Anatomy of the Stomach

• Location: in the left hypochondrium, and epigastric regions

• Surface Projection: “J” shape, size and position very variable, but two main points are fixed to the ab wall and are constant in their surface projection.

  • Esophageal-Gastric Jxn (Cardia) – L side, 2-4 cm lat to midline, @ 7^th costal cart anteriorly, @ T10-11 posteriorly

  • Gastro-duodenal Jxn (Pylorus) – L1-2 at slight R, 9^th costal cart, 1-2 cm lat to midline, can shift down to L3-4 when stomach is full

  • Fundus – sup edge of 5^th rib @ mid-inguinal line

  • Stomach cross midline about 5 fingers above the umbilicus

• Topography: Sits in the Gastric bed, made up of the pancreas, spleen, left kidney, left suprarenal gland, transverse colon (L flexure), mesocolon, and diaphragm

  • Ant = Diaphragm, left lobe of liver, anterior ab wall,spleen, transverse colon

  • Post = the Gastric Bed as mentioned above, along with the Omental Bursa (Lesser Sac), and the splenic a.

• Function: Stores and digest food, using Gastric juice (chyme), made up of Gastrin, HCL, Pepsin,etc.

• Parts:

1. 1. Cardia – part of the stomach that receives the esophagus
   2. Fundus – area of the stomach above the level of the cardia, located w/in left dome of diaphragm. Cardiac notch –angle between esophagus and fundus
   3. Body (Corpus) – main part of stomach between cardia and pyloric antrum
   4. Pyloric Antrum – funnel shaped region of stomach that leads to pyloru
   5. Pylorus – last part of the stomach, contains the pyloric sphincter, the muscle that allows the emission of gastric juice into duodenum.
   6. Lesser Curve – the shorter, concave side from the cardia to the pylorus. Attachment site for lesser omentum. Angular notch – angle between pyloric antrum and pylorus
   7. Greater Curve – long convex line leading from cardia to pylorus, next to spleen. Attachment site for greater omentum.

• Blood Supply:

  • Because stomach is part of FOREGUT, it is supplied by branches of SUP MESENTERIC A.

  • Lesser curve – L gastric a (celiac trunk), R gastric a (hepatic a proper, from common hepatic a from celiac trunk). Both gastric a anastomose with each other.

  • Greater curve – L gastroepiploic (same as gastro-omental) (splenic a), R gastro-epiploic a (from gastroduodenal a) The 2 gastroepiploic anastomose with each other.

  • Fundus – Short gastric a (splenic a)

  • Veins pretty much follow the arteries.

  • • L&R Gastric v → portal v.

  • • Short gastric v and left gastroepiploic v → splenic v → portal v.

  • • R gastro omental v → sup mesenteric a

• Lymph Drainage – divide stomach into quadrants

  • Upper Right  → L gastric nodes → can go to 3 places:

    • Sup/ant → parasternal nodes, sup/post → post mediastinal nodes. Both drain into supraclavicular nodes. (→ thoracic duct)

  • • Can also drain into → cardiac nodes → celiac nodes

  • • Clinical Note – The fact that gastric nodes can drain eventually into supraclavicular lymph nodes is clinically significant. In the case of gastric carcinoma or inflammation, one of the first areas where it can be detected is if one of the supraclavicular nodes, the Virchow, is enlarged.

NOTE – a “sentinal” lymph node, is usually superficially placed and one of the first to be felt in case of inflammation or carcinoma. It is not the specific name of one lymph node, but a general term for any lymph node that fits the above description.

• • Upper Left → Splenic nodes → run w/ splenic a to go to celiac nodes

  • Lower Right  → Pyloric nodes → celiac nodes

  • Lower Left → gastroepiploic nodes → pyloric nodes

  • All drain eventually to cysterna chyli, unless mentioned otherwise

• Innervation

  • PNS – (+) digestion, secretion, vasodilation.

  • • Foregut = CNX sends branches to submucosal/myenteric plexus w/in wall of organs → short post ggl fibers

  • SNS – (-) digestion, secretion, vasoconstriction

  • • from T6-T9 → send branches to celiac plexus through grtr. Splanchnic n. → aortic hiatus → celiac ggl plexus around celiac trunk → post ggl fibers run with arteries that branch off celiac trunk.

• Special Areas:

  • Labbe’s Triangle – where stomach is in direct contact with ab wall. Loc between inf border of liver, L costal arch, and transverse colon.

  • Space of Traube – location of fundus. Located between inf border of liver, spleen, L costal arch, transverse colon

  • • Clinical NOTE – From Wikipedia = There are 2 possibilities to evaluate splenomegaly in the clinical examination: percussion and palpation.[1] Percussion can be done in this space.Underneath Traube’s space lies the stomach, which produces a tympanic sound on percussion. If percussion over Traube’s space produces a dull tone, this might indicate splenomegaly (but can also occur after a meal). Assessing this may be more difficult in obese patients.

• Peritoneal Ligaments

  • Dorsally (Behind, part of dorsal mesogastrium) – phrenicogastric, phrenico lienal, lienorenal, gastrocolic lig, Greater omentum

  • Ventrally (ant, part of ventral mesogastrium) – hepatogastric lig

Histology – Stomach # 47 * H&E

Structures to Identify:

• simple columnar epithelium

• gastric pits (foveal)

• simple tubular glands

• mucus, chief, parietal, resting cells

• APUD (stained by heavy metals, like Ag)

• Meissner’s/Myenteric plexus

• Rugae

• surface mucus cells

General Information

• under diaphragm on left side, our slide is taken from the body region of stomach

• Cardia, Fundus, Pylorus – all have diff glands and diff secretions.

• Stomach mixes and partially digests food, creating chyme to send to duodenum

• Layers: Mucosa, Submucosa, Muscularis Externa, Serosa (visceral peritoneum)

Mucosa

• Simple columnar epithelium, that invaginates into stomach parenchyme to make gastic pits, where gastric glands open into. Gastic glands have glandular epithelium

• mucus surface cells secrete mucus onto surface of stomach to protect it from the acidiity of gastric juice (pH=1-2)

• Lamina Propria – lymphoreticular connective tissue, loads of reticular fibers and collagen fibers, as well as diffuse lymph tissue referred to collectively as GALT (Gut assoc. lymph tissue)

• Muscularis mucosae – Inner circular layer and outer longitudinal layer. Smooth m. strands from the inner layer split each gastric pit from each other.

Gastric Glands:

*Secretions from glands listed in picture on right.

• Mucus neck glands – secrete soluble mucus, very pale cytoplasm, lots of rough ER, located in neck of gastric glands, in b/w parietal cells. Cuboidal with basal nucleus,

• Parietal cells – triangular cells with very very eosinophillic (red) cytoplasm, narrow apical part that points towards pit, large cell with large nucleus. Located in neck and partially the isthmus of gastric pit.

• Chief cell – small, cuboidal, basophillic cell, highest in # at base of gland so look for them there.

• Enteroendocrine cell – v. faint cell with LARGE nucleus, (unlike parietal, which is v. red normally), smaller than parietal cell, has paracrine secretion, secrete not into pit, but into lamina propria.

• Originate from endoderm but become endocrine, part of GEP cells system (Gastro-Entero-Pancreatic), but can also say is part of APUD (neural crest origin)
  

Submucosa

• contains Meissner’s plexus (aka Submucosal plexus)

• In empty stomach, can protrude into rugae

• dense irregular CT, with more collagen fibers than LP

• lymph vessels, capillaries, larger arterioles, venules, fibroblasts, adipose

Muscularis Externa

• NOTE Has three layers of musc = Inner oblique, middle circular, outer longitudinal

• has Myenteric plexus – PNS ggl and n fibers – loc. b/w middle and outer layers

Serosa

• comes with sub serosa

• equivalent to visceral peritoneum – only present in intraperitoneal organs, or organs covered partially with peritoneum

• considered simple squamous mesothelium, so if asked to find mesothelium, you know what it is.

Stomach # 48 * PAS

• PAS shows CARBS = mucus producing cells

• surface epithelium is dark, as well due to surface mucus cells → easy to identify by looking for bright pink line on top of epithelium

• parietal cells stain less darkly (as compared to H&E)

• w/in LP can see purple fibers due to PAS positive staining of reticular fibers

• reticulare basement membrane around gland also PAS positive

• Secondary lymph nodules also visible

PAS rxn : used to visualize carbohydrates like substances. Periodic acid oxidizes the vicinal hydroxyl and amino groups, breaks the chain to form an aldehyde. Basic fuchsin bleached by sulfuric acid reacts with these aldehyde groups, giving characteritic magenta color.

Structures to Identify in particular:

• mucus neck cells and surface mucus cells

• Parietal cells

• LP

• reticular fibers

• lymph nodules

Embryology of Stomach

• Appears as enlargement of forgut @ 14^th week, changes from tube shape due to different rates of growth of the future lesser and greater curves, and because of movements of surrounding organs

• Longitudinally: rotates L (ant) and R (post). Posterior side grows faster → creates lesser and greater curvature

• Ant-Post axis: Pylorus moves R & up, cardia moves L and down

• Stomach connects to dorsal body by dorsal mesogastrium, which thru the clockwise rotation, is carried left to form greater omentum

• L vagus = ventral surface of stomach, R vagus = dorsal surface (which makes sense as the L vagus rests on the ant side of esoph, and R vagus is on posterior side, and it just carries on down that way.

• Longit. Rotation causes creation of lesser sac behind stomach

• Ant/Post Rotation causes creation of greater sac,

• Lesser Omentum (hepatoduodenal and hepatogastic ligaments) formed by ventral mesogastrium with falciform lig.

Anim = http://www.indiana.edu/~anat550/gianim/sdo/sdo.html

Anim2 = http://www.rvc.ac.uk/Review/abdomen/HTML/stomach.htm