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استمازة جقييم السسائل البحثيت ملقسز دزاس ي

اوال : بياهاث جمأل بمعسفت الطالب السقم املسلسل : 124

اسم الطالب : احمد خالد خضس علي

كليت : كليت التمسيض الفسقت/املستوى : الفرقة االولي الشعبت : عام اسم املقسز : تشريح كود املقسز: .. )ط 202 ) استاذ املقسز : د/ السيد علي مهران & د/ عبدالحميد سيد ابوبكر

البريد الالكترووى للطالب :[email protected] عىوان السسالت البحثيت :(digestive system (

ثاهيا: بياهاث جمأل بمعسفت لجىت املمتحىيين

هل السسالت البحثيت املقدمت متشابت جصئيا او كليا ☐وعم ☐ ال فى حالت الاجابت بىعم ال يتم جقييم املشسوع البحثى ويعتبر غير مجاش جقييم املشسوع البحثى م عىاصس التقييم الوشن التقييم اليسبى 1 الشكل العام للسسالت البحثيت 2 جحقق املتطلباث العلميت املطلوبت 3 يركس املساجع واملصادز العلميت 4 الصياغت اللغويت واسلوب الكتابت جيد

هتيجت التقييم النهائى /111 ☐هاجح☐زاسب

جوقيع لجىت التقييم 1.

.2

.3 .4 .5

جسفق هره الاستمازة كغالف للمشسوع البحثى بعد استكمال البياهان بمعسفت الطالب وعلى ان ال جصيد عً صفحت واحدة

Stomach is the central of digestive system

Introduction:-

*The digestive system : is well adapted for ingesting food, breaking it down, both mechanically and enzymatically, and then absorbing the breakdown products and transporting them to the . Separate processes are involved in digesting carbohydrates, proteins, and lipids. Many aspects of the digestive process are regulated by neural (autonomic) and local hormonal influences. The structure of the is well designed to both produce and protect itself from the low pH generated by the secreted hydrochloric acid. The exocrine pancreas produces many digestive enzymes in an inactive form. Activation usually occurs within the lumen of the . The liver receives the bulk of the absorbed nutrients via the portal vein and then uses them for the synthesis of many larger molecules. The intestinal microbiome includes many more cells than the number present in the human body. These microbes have evolved symbiotically along with the digestive system.

*, the system used in the human body for the process of digestion. The human digestive system consists primarily of the digestive tract, or the series of structures and organs through which food and liquids pass during their processing into forms absorbable into the bloodstream. The system also consists of the structures through which wastes pass in the process of elimination and other organs that contribute juices necessary for the digestive process.

The digestive system can be divided into two main parts:

1. Alimentary Tract of the Digestive System o Mouth o & o Stomach o Small and 2. Accessory Organs of the Digestive System o Salivary Glands o Liver o Gallbladder o Pancreas Stomach:-

In its normal position, the stomach is an elongated oval sac-like structure about 3.5 –3.8 mm. long. It is transversely located within the penultimate whorl of the visceral mass and its whole outer surface is covered by the digestive gland follicles, except the dorsal part. It is noticeable that its dorsal surface appears pale bluish in color indicating the presence of haemolymph spaces within the connective covering it. In a dorsal view, the stomach has a relatively broad or posterior part 0.8 mm. in greatest width, and it narrows gradually towards the relatively narrow and short proximal or anterior part about 0.35 mm, in width. The former part which is far from the buccal mass is about 2.1 mm long and the latter is about 0.9 mm long. The esophagus opens into the distal or cardiac part of the stomach at a point near the left side of its anteroventral surface. Also, careful examination of the ventral aspect of the stomach shows the existence of a small ventral protrusion or vestibule arising from its distal or cardiac part close to its point of connection with the esophagus. These vestibules nearly rounded in top view being about 3.5 mm. in diameter and it receives, at its posterior edge, two adjacent common ducts emerging from the follicles of the digestive gland. The antero-median border of the proximal or pyloric part of the stomach is connected dorsally to the style sac and ventrally to the intestine, A mid-longitudinal incision is made along the roof of the stomach, a system of elevations and grooves can be seen on the lining of its cardiac and pyloric parts, Examination of histological sections of the stomach revealed that these elevations are folds of the epithelial lining.On the floor of the cardiac portion of the stomach, three relatively large folds can be easily discerned. The first of these is mid-ventral somewhat conical fold which is the largest one: being about 1.00 mm long. It has a distal or posterior relatively broad part about 0.75 mm. in greatest width and narrows gradually towards its proximal end to become about 0.35 mm. wide. The second fold is intermediate in size and semicircular in outline extending on the periphery of the postero-lateral part of the floor of the cardiac stomach. It encircles the broadest posterior part of the mid-ventralfold and its left part is longer than the right one. It is moderately protruding into the lumen; being about 175 μm., in height and about 300 μm in width. These two folds enclose in between a semicircular relatively deep groove which is usually filled with food and the secretion of the digestive gland and it corresponds to the groove termed "the gutter" in the snail Paludomus tanschaurica (Seshaiya, 1929). The third fold is the smallest one, and it runs as a narrow elevation along the left margin of the floor of the cardiac part from its posterior end forwards to a point about 0.45 mm. before its anterior border. It is differentiated into an outer long limb about 2.0 mm in length and an inner anterior adjacent short limb about 0.3 mm. in length and 0.13 mm in width. The anterior region of fusion of the limbs is about 0.15 mm. long and about 75 μm wide, and the outer limb narrows gradually and slightly towards its posterior end which is 0.25 mm wide. The position of this fold in the closed stomach gives the impression that it may likely act as a barrier to prevent the contents of the previously mentioned groove from flowing interiorly into the pyloric stomach which lies at a relatively low level, The interior of the pyloric part of the stomach is characterized by a nearly smooth deep floor and a slightly ridged roof. The low level of the floor of this part, in comparison with that of the cardiac stomach, facilitates the flow of the partially digested food from the

Studies on the Functional Morphology of the Digestive System of the Fresh Water Thiarid Snail119latter into the former.The wall of the cardiac part of the stomach has a simple columnar epithelial lining which is almost ciliated in all parts except that covered by the gastric shield. The latter part is distinguished by relatively short columnar cells ranging from 20 to 40 μm. in height, in comparison with the rest of the endothelium which is ranging from 30 to 50 μm in height. It is noticeable that the whole endothelium is formed of granulated narrow cells with almost central nuclei nearly alternatively with vacuolated relatively broad ones with mostly basal nuclei. This indicates the secretory nature of this endothelium. Outside this endothelium, there is a clear basement membrane followed by a coat of a highly vacuolated supported by irregularly scattered circular muscle fibers. This coat connects the cardiac stomach with the digestive gland or the mantle wall, The basic histological structureof the wall of the pyloric stomach is similar to that of the cardiac stomach. The noticeable difference between them is mainly confined to the ciliation and high of the endothelial columnar cells which are continuously ciliated in the former and generally shorter (about 15 μm. high) than in the latter.

*The Stomach is the most important of the digestive system. Sections:-

the human stomach is divided into four sections, beginning at the cardia.

 The cardia is where the contents of the esophagus empty into the stomach.  The fundus is formed in the upper curved part.  The body is the main, central region of the stomach.  The is the lower section of the stomach that empties contents into the . Blood supply:-

Schematic image of the blood supply to the human stomach: left and right gastric artery, left and right gastroepiploic artery and short gastric artery.

The lesser curvature of the human stomach is supplied by the right gastric artery inferiorly and the left gastric artery superiorly, which also supplies the cardiac region. The greater curvature is supplied by the right gastroepiploic artery inferiorly and the left gastroepiploic artery superiorly. The fundus of the stomach, and also the upper portion of the greater curvature, is supplied by the short gastric arteries, which arise from the splenic artery. Structure:-

In humans, the stomach lies between the oesophagus and the duodenum (the first part of the small intestine). It is in the left upper part of the abdominal cavity. The top of the stomach lies against the diaphragm. Lying behind the stomach is the pancreas. A large double fold of visceral called the hangs down from the greater curvature of the stomach. Two sphincters keep the contents of the stomach contained; the lower oesophageal sphincter (found in the cardiac region), at the junction of the oesophagus and stomach, and the pyloric sphincter at the junction of the stomach with the duodenum.

The stomach is surrounded by parasympathetic (stimulant) and sympathetic (inhibitor) plexuses (networks of blood vessels and nerves in the anterior gastric, posterior, superior and inferior, celiac and myenteric), which regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles.

Because it is a distensible , it normally expands to hold about one litre of food. The stomach of a newborn human baby will only be able to retain about 30 millilitres. The maximum stomach volume in adults is between 2 and 4 litres. layers of the stomach wall:- stomach walls consist of a mucosa, , muscularis externa, subserosa and serosa.

The inner part of the lining of the stomach, the gastric mucosa, consists of an outer layer of column-shaped cells, a , and a thin layer of smooth muscle called the muscularis mucosa. Beneath the mucosa lies the submucosa, consisting of fibrous connective tissue.[citation needed] Meissner's plexus is in this layer.

Outside of the submucosa lies another , the muscularis externa. It consists of three layers of muscular fibres, with fibres lying at angles to each other. These are the inner oblique, inner circular, and outer longitudinal layers. The presence of the inner oblique layer is distinct from other parts of the , which do not possess this layer.

 The inner oblique layer: This layer is responsible for creating the motion that churns and physically breaks down the food. It is the only layer of the three which is not seen in other parts of the digestive system. The antrum has thicker skin cells in its walls and performs more forceful contractions than the fundus.  The middle circular layer: At this layer, the pylorus is surrounded by a thick circular muscular wall, which is normally tonically constricted, forming a functional (if not anatomically discrete) pyloric sphincter, which controls the movement of chyme into the duodenum. This layer is concentric to the longitudinal axis of the stomach.  Auerbach's plexus (AKA myenteric plexus) is found between the outer longitudinal and the middle circular layer and is responsible for the innervation of both (causing peristalsis and mixing)

The outer longitudinal layer is responsible for moving the bolus towards the pylorus of the stomach through muscular shortening.

To the outside of the muscularis externa lies a serosa, consisting of layers of connective tissue continuous with the peritoneum. Function:-

 Digestion :In the human digestive system, a bolus (a small rounded mass of chewed up food) enters the stomach through the esophagus via the lower esophageal sphincter. The stomach releases proteases (protein-digesting enzymes such as pepsin) and hydrochloric acid, which kills or inhibits bacteria and provides the acidic pH of 2 for the proteases to work. Food is churned by the stomach through muscular contractions of the wall called peristalsis – reducing the volume of the bolus, before looping around the fundus and the body of stomach as the boluses are converted into chyme (partially digested food). Chyme slowly passes through the pyloric sphincter and into the duodenum of the small intestine, where the extraction of nutrients begins.

Gastric juice in the stomach also contains pepsinogen. Hydrochloric acid activates this inactive form of enzyme into the active form, pepsin. Pepsin breaks down proteins into polypeptides.

 Absorption :Although the absorption in the human digestive system is mainly a function of the small intestine, some absorption of certain small molecules nevertheless does occur in the stomach through its lining. This includes:  Water, if the body is dehydrated  Medication, such as aspirin [25]  Amino acids  10–20% of ingested ethanol (e.g. from alcoholic beverages)  Caffeine

To a small extent water-soluble vitamins (most are absorbed in the small intestine)

*References:-

1- Brenner, H., Rothenbacher, D., & Arndt, V. (2009). Epidemiology of . In . Cancer epidemiology (pp. 467-477). Humana Press.

2- Washington, K. (2010). of the AJCC cancer staging manual: stomach. Annals of surgical . oncology, 17(12), 3077-3079

3- Imran, M. A. (2006). U.S. Patent No. 7,037,343. Washington, DC: U.S. Patent and Trademark Office.

4- Hamilton, S. R., & Aaltonen, L. A. (Eds.). (2000). Pathology and genetics of tumours of the digestive system (Vol. 2). Lyon:: IARC press

5- Knowledge bank.

6- Bosman, F. T., Carneiro, F., Hruban, R. H., & Theise, N. D. (2010). WHO classification of tumours of the digestive system (No. Ed. 4). World Health Organization.

7- Stevens, C. E., & Hume, I. D. (2004). Comparative physiology of the vertebrate digestive system. Cambridge University Press.