StomachPrepare

d by:Peshawa

Yasin

University Of SULAIMANI

College Of ScienceDepartment:

BIOLOGY

Index

Description

Functions of Stomach

Shape

Histology

Structural anatomy

Functional anatomy

Gross Anatomy

Stomach size

Gastric emptying

Mechanical & Chemical Digestion

Gastrectomy

Description

The stomach is an expanded J-shaped organ in the upper left region of the abdominal cavity.

It is continuous with the esophagus superiorly and empties into the duodenum of the small intestine inferiorly.

It continues the mechanical and chemical digestion of the bolus. After the bolus has been completely processed in the stomach, the product is called chyme.

Functions of Stomach

Digestion. Produce acid. Reservoir for food. Slows food entering intestines. Help with vitamin absorption (Vitamin

B12).

Stomach shape

Its shape and position are strongly associated with organogenesis.

Any developmental abnormality of the organ itself or nearby located viscera and peritoneum, as well as their vessels and nerves may influence stomach morphology.

Stomach Shapes

Histology

The stomach is lined by a simple columnar epithelium.

This epithelium contains surface mucous cells which secrete mucin onto the epithelial lining.

The muscularis: It is composed of three smooth muscle layers

instead of two:

Inner oblique layer.

Middle circular layer, and o

Outer longitudinal layer.

Structural anatomy

The cardia connects the esophagus to the upper stomach (fundus), which merges with the body (corpus) followed by the antrum of the stomach.

The lower outlet of the stomach (pylorus) merges with the duodenum.

The left-facing arch of the stomach is the greater curvature, whereas the right surface forms the lesser curvature. The superior rounded portion under the left side of the diaphragm is the stomach’s fundus.

Functional anatomy

The stomach can be divided into a proximal and a distal segment.

The proximal stomach mainly serves as a food reservoir. Its tone determines the rate at which food passes to the distal stomach.

In the distal stomach, food is further processed (chyme formation), it is also responsible for portioning chyme delivery to the small intestine.

Gross Anatomy

The adult stomach varies from 15 to 25 cm long, but its diameter and volume depend on how much food it contains.

An empty stomach has a volume of about 50 ml and a cross-sectional diameter only slightly larger than the large intestine, but when it is really distended it can hold about 1.5 L of food.

Stomach size

Stomach is the most dilated part of the digestive tract.

Stomach size is dependent on the degree of gastric filling, but this distension is mainly limited to the proximal stomach.

Gastric emptying

Solid food remains in the stomach until it has been broken down into small particles (diameter of !1mm) and suspended in chyme.

The chyme then passes to the duodenum. The time required for 50% of the ingested

volume to leave the stomach varies, for instance: 10—20 min for water and

1–4 hours for solids (carbohydrates, proteins, fats).

When empty, the stomach collapses inward, throwing its mucosa into large, longitudinal folds called rugae (roo’ge).

Indigestible substances

Indigestible substances (bone, fiber, foreign bodies) do not leave the stomach during the digestive phase.

Special contraction waves called migrating motor complexes (MMC) pass through the stomach and small intestine roughly every 1.5 hours during the ensuing interdigestive phase, as determined by an intrinsic “biological clock”.

These peristaltic waves transport indigestible substances from the stomach and bacteria from the small intestine to the large intestine.

Mechanical Digestion

The walls of stomach have several layers of smooth muscle. There are three layers of muscle, when food is present, these muscles work together to churn the content of stomach.

You have probably heard your stomach “growl” when it has been empty for some times. These sounds are made by the contraction of smooth muscles that form the walls of stomach.

Chemical Digestion

Gastric fluid carries out chemical digestion in the stomach.

Gastric enzymes: Pepsin splits complex protein molecules into

shorter chains of amino acids. Hydrochloric acid in the stomach not only

ensure the low pH, but also dissolves minerals and kills bacteria that enter the stomach along with food.

Gastrectomy

About half of the patients subjected to total gastrectomy experience weight loss.

Malabsorption, particularly fat malabsorption, is a common feature after total gastrectomy. This may be due to shortened intestinal transit time and small bowel bacterial overgrowth, but is less often due to diarrhea or pancreatic exocrine insufficiency.

Total and subtotal

In a total gastrectomy, the intestine is joined to the end of the esophagus, whilst

In a partial (or sub-total) gastrectomy the intestine is joined to the remaining healthy stomach.

sub

Total

Total and subtotal

Patients who had a total gastrectomy continued to suffer from alimentary symptoms, especially indigestion and diarrhea, during the entire follow-up period.

However, patients who underwent subtotal gastrectomy had a significantly better outcome already during the first postoperative yr. Patients given a gastric substitute after gastrectomy improved with the passage of time and had an even better outcome in the long run.

Common After-Effects of Gastrectomy

Prolonged period of recovery.

Reduces size of the food reservoir – this can lead to reduced food intake and weight loss.

Vitamin B12 not available from diet – so B12 will be needed by injection.

No stomach acid means that the stomach is more susceptible to infections.

Rapid movement of food to small intestine – this causes ‘dumping syndrome’.

Comparison between different animals

References

Books Elaine N. Marieb, Katja Hoehn. (2013). Human anatomy &

physiology. 9th ed. Pearson Education, Inc. USA. 1107 pp.

Fox, Stuart Ira. (2011). Human physiology. 12th ed. McGraw-Hill Companies, Inc. USA. 749 pp.

Freudenrich c.c. and Tortora G. J. (2010). Visualizing Human Anatomy and Physiology. John wiley & Sons, Inc. USA 400-415 pp.

Johnson M.D. (2010). Human Biology Concepts and Currents. 6th ed. Pearson Education, Inc. 327-341 pp.

John H. postlethwait, Janet L. Hopson. (2006). Modern Biology. Holt, Rinehart and Winston. USA. 1130.

Agamemnon Despopoulos, Stefan Silbernagl. (2003). Color Atlas of Physiology 5th ed. Georg Thieme Verlag. Germany. 436 pp.

References

Articles: Burdan F. and R.K. Ingrid. (2012). Anatomical classification

of the shape and topography of the stomach. 34(2): 171–178 pp.

Jan Svedlund MD, and Sullivan M. (1999). Long term consequences of gastrectomy for patients' quality of life: the impact of reconstructive techniques. 94, 438–445.

Lars Olbe M.D. and Lars Lundell M.D. (1987). Intestinal function after total gastrectomy and possible consequences of gastric replacement. Volume 11, Issue 6, pp 713-719.

Website: http://www.gics.org.uk/content/3.pdf

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