G.I.TAPPLIED ANATOMY

OESOPHAGUS The oesophagus is a muscular tube that

starts as the continuation of the pharynx and ends as the cardia of the stomach.

The oesophagus is firmly attached at its upper end to the cricoid cartilage and at its lower end to the diaphragm.

NARROW AREAS OF THE OESOPHAGEAL LUMEN Three normal areas of oesophagus

narrowing are evident on the barium oesophagogram or during oesophagoscopy.

The uppermost narrowing is located at the entrance into the oesophagus and is caused by the cricopharyngeal muscle.

Its luminal diameter is 1.5 cm, and it is the narrowest point of the oesophagus.

NARROW AREAS OF THE OESOPHAGEAL LUMEN The middle

narrowing is due to an indentation of the anterior and left lateral oesophageal wall caused by the crossing of the left main stem bronchus and aortic arch. The luminal diameter is 1.6 cm.

NARROW AREAS OF THE OESOPHAGEAL LUMEN The lowermost narrowing is at the hiatus of

the diaphragm and is caused by the gastroesophageal sphincter mechanism.

The luminal diameter at this point varies somewhat depending on the distention of the oesophagus by the passage of food, but has been measured at 1.6 to 1.9 cm.

These three sites may offer resistance to the passage of a tube down the oesophagus into the stomach

Superiorly: level of cricoid cartilage, juncture with pharynx

Middle: crossed by aorta and left main bronchus

Inferiorly: diaphragmatic sphincter

Oesophageal Constrictions

The lymphatic drainage is from a perioesophageal lymph plexus into the posterior mediastinal nodes, which drain both into the supraclavicular nodes and into nodes around the left gastric vessels.

It is not uncommon to be able to palpate hard, fixed supraclavicular nodes in patients with advanced oesophageal cancer.

LYMPHATIC DRAINAGE

In oesophagoscopy, measurements are made from the upper incisor teeth; the three important levels (17cm), (28cm) and (43cm) corresponding to

The commencement of the oesophagus, The point at which it is crossed by the left

bronchus and its termination respectively. These three points also indicate the

narrowest parts of the oesophagus: the sites at which, swallowed foreign bodies are most likely to become impacted and strictures to occur after swallowing corrosive fluids

APPLIED ANATOMY

The anastomosis between the azygos (systemic) and left gastric (portal) venous tributaries in the oesophageal veins is of great importance in portal Hypertension.

these veins distend into large collateral channels, oesophageal varices, which may then rupture with severe haemorrhage.

The oesophagus is crossed solely by the vena azygos on the right side. This is therefore the side of choice surgically to approach the oesophagus.

APPLIED ANATOMY CONTD

STOMACH General

◦J-shaped◦Functions Digestion

Chemical Mechanical

Results in chyme

Limited absorption

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The stomach is considered as two organs: its proximal portion is designed for storage and digestion, and its distal part is adapted to the role of mixing and evacuation.

In adult life, stomach located T10 and L3 vertebral segment

Can be divided into anatomic regions based on external landmarks◦4 regions Cardia Fundus Corpus (body) Antrum

ANATOMY

RELATIONS OF STOMACH Anterior- in contact with Left hemi-

diaphragm, left lobe and anterior segment of right lobe of the liver and the anterior parietal surface of the abdominal wall

Posterior- Left diaphragm, Left kidney, Left adrenal gland, and neck, tail and body of pancreas

The greater curvature is near the transverse colon and transverse colon mesentery

The concavity of the spleen contacts the left lateral portion of the stomach

The lesser curve of the stomach is supplied primarily by the left gastric artery, which arises from the celiac axis. The right gastric artery, arising from the ascending hepatic artery, is usually a small vessel that provides branches to the first part of the duodenum and the pylorus

VASCULATURE

Right and left gastroepiploic aretries arise from the gastroduodenal and splenic arteries, respectively. They from an arcade along the greater curve, the right providing blood to the antrum and the left supplying the lower portion of the fundus.

VASCULATURE

LYMPHATIC DRAINAGEi. Area I drains along the right

and left gastric vessels to the aortic nodes.

ii. Area II drains to the subpyloric and thence aortic nodes via lymphatics along the right gastro-epiploic vessels.

iii. Area III drains via lymphatics along the splenic vessels to the suprapancreatic nodes and thence to aortic nodes.

◦The stomach is innervated by terminal branches from the anterior and posterior gastric nerves (gastric divisions of both the anterior and posterior vagi)

◦Left and Right Vagus Nerves descend parallel to the oesophagus within the thorax before forming a peri-esophageal plexus between the tracheal bifurcation and the diaphragm

NERVE SUPPLY

NERVE SUPPLY Left (anterior) Vagus

Nerve◦Left of the

Oesophagus Branches

Hepatic Branch Supplies liver

and Biliary Tract Anterior gastric or

Ant. Nerve of Latarget

NERVE SUPPLY

Right (posterior) Vagus Nerve◦Right of the

Oesophagus Branches

Celiac Posterior Latarget Innervates

posterior gastric wall

The secretion of acid and pepsin is controlled by two mechanisms: nervous and hormonal.

The vagus nerves are responsible for the nervous control, and the hormone gastrin, produced by the antral mucosa, is responsible for the hormonal control.

APPLIED ANATOMY

Following Vagotomy, the neurogenic (reflex) gastric acid secretion is abolished but the stomach is, at the same time, rendered atonic so that it empties only with difficulty; because of this, total Vagotomy must always be accompanied by some sort of drainage procedure.

APPLIED ANATOMY

Total (truncal) vagotomy and selective vagotomy must be accompanied by some sort of drainage procedure, either a pyloroplasty (to enlarge the pyloric exit and render the pyloric sphincter incompetent) or by a gastrojejunostomy to prevent dumping syndrome.

APPLIED ANATOMY

A posterior gastric ulcer or cancer may erode the pancreas, giving pain referred to the back. Ulceration into the splenic artery may cause torrential haemorrhage.

In the surgical treatment of chronic gastric and duodenal ulcers, attempts are made to reduce the amount of acid secretion by sectioning the vagus nerves (vagotomy) and by removing the gastrin-bearing area of mucosa, the antrum (partial gastrectomy).

APPLIED ANATOMY

Knowledge of the anatomy of these nerves has led to the technique, highly selective vagotomy, for treatment of peptic ulcer. In this procedure, the antral branches called the “crow’s foot” are preserved, while the more proximal branches are divided as they enter the stomach as in selective vagotomy.

APPLIED ANATOMY

Malignant disease of the stomach is treated by total gastrectomy, which includes the removal of the lower end of the oesophagus and the first part of the duodenum; the spleen and the gastrosplenic and splenicorenal ligaments and their associated lymph nodes; the splenic vessels; the tail and body of the pancreas and their associated nodes;

APPLIED ANATOMY

the nodes along the lesser curvature of the stomach; and the nodes along the greater curvature, along with the greater omentum

The continuity of the gut is restored by anastomosing the oesophagus with the jejunum.

APPLIED ANATOMY

Drainage can be avoided if the nerve of Latarjet is preserved, thus maintaining the innervation and function of the pyloric antrum (highly selective vagotomy).

APPLIED ANATOMY

A penetrating ulcer of the anterior stomach wall may result in the escape of stomach contents into the greater sac, producing diffuse peritonitis.

The anterior stomach wall may, however, adhere to the liver, and the chronic ulcer may penetrate the liver substance.

APPLIED ANATOMY

Gastric Pain The sensation of pain in the stomach is caused by the stretching or spasmodic contraction of the smooth muscle in its walls and is referred to the epigastrium.

APPLIED ANATOMY

Gastroscopy. The mucosa of the air-inflated stomach can be inspected in the living subject through the gastroscope. With the modern fibre-optic instrument the whole of the gastric mucosa can be viewed, the duodenum examined, and the common bile duct and the pancreatic duct intubated for retrograde contrast-enhanced radiological study.

It is also possible to perform a mucosal biopsy through a gastroscope.

APPLIED ANATOMY

APPLIED ANATOMY

The right posterior vagus may occasionally give off a small branch that courses to the left behind the oesophagus to join the cardia. This branch has been termed the “criminal nerve of Grassi” in recognition of its important role in the etiology of recurrent ulcer when it is left undivided.

Nasogastric intubation i is performed to empty the stomach, to decompress the stomach in cases of intestinal obstruction, or before operations on the gastrointestinal tract; it may also be performed to obtain a sample of gastric juice for biochemical analysis.

Nasogastric Intubation

1. The patient is placed in the semi upright position or left lateral position to avoid aspiration.

2. The well-lubricated tube is inserted through the wider nostril and is directed backward along the nasal floor.

3. Once the tube has passed the soft palate and entered the oral pharynx, decreased resistance is felt, and the conscious patient will feel like gagging.

Nasogastric Intubation

4. Some important distances From the nostril (external nares) to the

cardiac orifice of the stomach is about 17.2 in. (44 cm),

from the cardiac orifice to the pylorus of the stomach is 4.8 to 5.6 in. (12 to 14 cm).

The curved course taken by the tube from the cardiac orifice to the pylorus is usually longer, 6.0 to 10.0 in. (15 to 25 cm)

Nasogastric Intubation

Deviated nasal septum, making the passage of the tube difficult on the narrower side.

Three sites of oesophageal narrowing may offer resistance to the nasogastric tube.

The upper oesophageal narrowing may be overcome by gently grasping the wings of the thyroid cartilage and pulling the larynx forward. This manoeuvre opens the normally collapsed oesophagus and permits the tube to pass down without further delay.

Anatomic Structures that May Impede thePassage of the Nasogastric Tube

The nasogastric tube enters the larynx instead of the oesophagus.

Rough insertion of the tube into the nose will cause nasal bleeding from the mucous membrane.

Penetration of the wall of the oesophagus or stomach.

Always aspirate tube for gastric contents to confirm successful entrance into stomach.

Anatomy of Complications

Finishes chemical digestion Responsible for absorbing most of the

nutrients. ◦Ingested nutrients spend at least 12 hours in

the small intestine. thin-walled tube The length of the small

intestine varies from 10 to 33 feet (3–10m) The average is about 6 meters (20 feet) in length.

Resection of up to one third or even half of the small intestine is compatible with a perfectly normal life.

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SMALL INTESTINE

SMALL INTESTINE

It extends from the pylorus of the stomach to the caecum of the large intestine

It occupies a significant portion of the abdominal cavity.

The jejunoileum extends from the peritoneal fold that supports the duodenal-jejunal junction (the ligament of Treitz) downward to the ileocecal valve.

The duodenum is first segment of the small intestine. It is approximately 25 centimeters (10 inches) long and originates at the pyloric sphincter◦ The duodenum curves in a C around the head of the pancreas. ◦ At its origin from the pylorus it is completely covered with◦ peritoneum for about 1 in (2.5 cm), but then becomes a

retroperitoneal organ, only partially covered by serous membrane.

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SMALL INTESTINE

The first part of the duodenum is overlapped by the liver and gallbladder, either of which may become adherent to, or even ulcerated by, a duodenal ulcer.

The pancreas, as the duodenum’s most intimate relation, is readily invaded by a posterior duodenal ulcer. The pain radiates into the dorsolumbar region.

Erosion of the gastroduodenal artery by such an ulcer results in severe haemorrhage.

The first part of the duodenum becomes which becomes visible following barium meal as a triangular shadow termed the duodenal cap.

APPLIED ANATOMY

The jejunum: middle region of the small intestine. ◦approximately 2.5 meters (7.5 feet)◦makes up approximately two-fifths of the small

intestine’s total length. ◦primary region for chemical digestion and nutrient

absorption . There is no sharp distinction between the jejunum and

ileum. The ileum :is the last region of the small intestine.

◦about 3.6 meters (10.8 feet) in length◦forms approximately three-fifths of the small intestine. ◦terminates at the ileocaecal valve sphincter that controls the entry of materials into the

large intestine.

THE JEJUNUM AND ILEUM

1.The jejunum has a thicker wall as the circular folds of mucosa (valvulae conniventes) are larger and thicker more proximally.

2. The proximal small intestine is of greater diameter than the distal.

3. The jejunum tends to lie at the umbilical region, the ileum in the suprapubic region and pelvis.

4. The mesentery becomes thicker and more fat-laden from above downwards.

DIFFERENCES

5.The mesenteric vessels form only one or two arcades to the jejunum, with long and relatively infrequent terminal branches passing to the gut wall. The ileum is supplied by shorter and more numerous terminal vessels arising from complete series of three, four or even five arcades

approximate length of 1.5 meters (5 feet) diameter of 6.5 centimeters (2.5 inches). Absorbs most of the water and electrolytes from the

remaining digested material. Watery material that first enters the large intestine soon

solidifies and becomes faeces. Stores faecal material until the body is ready to

defecate. Absorbs a very small percentage of nutrients still

remaining in the digested material. Composed of four segments:

◦the caecum, colon, rectum, anal canal26

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LARGE INTESTINE

is subdivided, for descriptive purposes, into: caecum with the appendix vermiformis; ascending colon (5–8 in (12–20 cm)); hepatic flexure; transverse colon (18 in (45 cm)); splenic flexure; descending colon (9–12 in (22–30 cm)); sigmoid colon (5–30 in (12–75 cm), average 15

in (37 cm)); rectum (5 in (12 cm)); anal canal (1.5 in (4 cm)).

THE LARGE INTESTINE

The caecum is the first part of the colon, or large intestine, and begins at the ileocaecal junction

It is a blind pouch, which has a mesentery, and gives rise to the vermiform appendix.

The appendix has its own mesentery, the mesoappendix.

CAECUM

The colon (but not the appendix, caecum or rectum), bears characteristic fat-filled peritoneal tags called appendices epiploicae scattered over its surface.

The colon and caecum (but not the appendix or rectum) are marked by the taeniae coli. These are three flattened bands commencing at the base of the appendix and running the length of the large intestine to end at the rectosigmoid junction. These causes sacculations of the intestine

FEATURES

The taeniae are about a foot shorter than the gut to which they are attached.

These sacculations may be seen in a plain radiograph of the abdomen when the large bowel is distended and appear as

incomplete septa projecting into the gas shadow.

APPLIED ANATOMY

The appendix arises from the posteromedial aspect of the caecum about 1 in (2.5 cm) below the ileocaecal valve; its length ranges from 0.5 in (12mm) to 9 in (22 cm).

In the foetus it is a direct out pouching of the caecum, but differential overgrowth of the lateral caecal wall results in its medial displacement.

Most frequently (75% of cases) the appendix lies behind the caecum.

THE APPENDIX

POSITION AND BLOOD SUPPLY

The following factors contribute to the appendix’s predilection to infection:

It is a long, narrow, blind-ended tube, which encourages stasis of large-bowel contents.

It has a large amount of lymphoid tissue in its wall.

The lumen has a tendency to become obstructed by hardened intestinal contents (enteroliths), which leads to further stagnation of its contents.

Predisposition of the Appendixto Infection

Visceral pain in the appendix is produced by distention of its lumen or spasm of its muscle.

The afferent pain fibers enter the spinal cord at the level of the T10, and a vague referred pain is felt in the region of the umbilicus.

Later, the pain shifts to where the inflamed appendix irritates the parietal peritoneum. Here the pain is precise, severe, and localized (Somatic pain).

Pain of Appendicitis

The mesentery of the appendix, containing the appendicular branch of the ileocolic artery, descends behind the ileum as a triangular fold. Acute infection of the appendix may result in thrombosis of this artery with rapid development of gangrene and subsequent perforation.

The lumen of the appendix is relatively wide in the infant and is frequently completely obliterated in the elderly. They rarely develop appendicitis.

APPLIED ANATOMY

Usually performed through a muscle-splitting incision in the right iliac fossa.

Appendix is located by tracing the taeniae coli along the caecum—they fuse at the base of the appendix.

The appendix mesentery, containing the appendicular vessels, is firmly tied and divided, the appendix base tied, the appendix removed and its stump invaginated into the caecum.

McBurneys point junction between the medial two third and the lateral one third on the line joining the ASIS and umbilicus

APPENDICECTOMY

Meckel’s diverticulum represents the remains of the embryonic vitellointestinal duct (communication between the primitive mid-gut and yolk sac) and is, therefore, always on the anti-mesenteric border of the bowel.

it is said to occur in 2% of subjects, twice as often in males as females, to be situated at 2 feet (62 cm) from the ileocaecal junction and to be 2 in (5 cm) long.

Exomphalos is persistence of the mid-gut herniation at the umbilicus after birth.

APLLIED ANATOMY

Bleeding Oesophageal Varices Should the portal vein

become obstructed, as, for example, in cirrhosis of the liver and portal hypertension it develops, resulting in dilatation and varicosity of the portal–systemic anastomoses.

Varicosed oesophageal veins may rupture, causing severe vomiting of blood (haematemesis).

Bleeding Oesophageal Varices

Insertion of the Sengstaken-Blakemore Balloon for oesophageal Haemorrhage.

The Sengstaken-Blakemore balloon is used for the control of massive oesophageal haemorrhage from oesophageal varices.

A gastric balloon anchors the tube against the oesophageal–gastric junction. An oesophageal balloon occludes the oesophageal varices by counter pressure. The tube is inserted through the nose or by using the oral route.

Bleeding Oesophageal Varices

Bleeding Oesophageal Varices

The lubricated tube is passed down into the stomach, and the gastric balloon is inflated.

In the average adult the distance between the external orifices of the nose and the stomach is 17.2 in. (44 cm), and the distance between the incisor teeth and the stomach is 16 in. (41 cm).