Physical Address

304 North Cardinal St.
Dorchester Center, MA 02124

Organs of the abdominal cavity


Overview

Opening the abdominal wall reveals a cavity filled with some smooth and some partially solid organs (viscera). In its entirety it is called the ‘situs’ of the abdominal organs. The inside of the abdominal wall and the surface of the organs are covered with a thin, moist, shiny membrane (peritoneum). The lining on the inside of the abdominal wall is referred to as the parietal sheet of the peritoneum, while the visceral sheet covers the various organs. This largest part of the abdominal cavity is therefore known as the peritoneal cavity (Cavitas peritonealis) with the retroperitoneal space as a separate flat section behind the parietal peritoneum, which for instance contains the kidneys. The smooth peritoneum guarantees, for instance, that the stomach and intestines change shape during peristalsis so that the intestinal loops can easily move against each other. The middle transverse part of the large intestine (Colon transversum) divides the peritoneal cavity into an upper abdominal (epigastric) situs and a lower abdominal (hypogastric) situs.

The situs of the epigastrium (upper abdomen) contains, among other things, the liver (Hepar), with the closely positioned gallbladder (Vesica biliaris), and the pancreas as the biggest glands found in the human body. The stomach (Gaster) nestles up against the liver, which is on the right. On the left, behind the stomach, is the spleen in its own niche. The hypogastrium (lower abdomen) is filled with the loops of the small intestine (Intestinum tenue), which are surrounded and held in place by the large intestine (Intestinum crassum).

Main topics

After working through this chapter, you should be able to:

Peritoneal cavity

  • explain the structure of the abdominal cavity with recesses as well as the peritoneal duplications on the dissection;

  • explain the neurovascular pathways for all organs, with clinical relevance and organ-specific peculiarities;

Stomach

  • show the positional relationships of the stomach to the rest of the epigastric organs and describe its development;

Intestines

  • show sections of the small and large intestines on the dissection and explain their structural features;

  • describe the origin of the individual intestinal segments, including the boundaries of their areas supplied by neurovascular pathways, and the positional changes they undergo during their development;

  • demonstrate the clinical importance of the positional relationships of the appendix with projection onto the body surface;

Liver and gallbladder

  • explain the vital importance of the liver and its different functions;

  • show the position and projection of the liver and gallbladder and describe their development;

  • show the functional structure of the liver, including the liver segments on the dissection and explain their clinical significance;

  • describe the opening and closure mechanisms of the common bile duct (Ductus choledochus) and to show the topography of the CALOT's triangle on a dissection;

Pancreas

  • explain the vital importance and function of the pancreas;

  • show the classification and topography of the pancreas on the dissection, including the gear system, and explain their development, including malformations;

Spleen

  • understand the various functions of the spleen and its position and structure.

Clinical relevance

In order not to lose touch with prospective everyday clinical life with so many anatomical details, the following describes a typical case that shows why the content of this chapter is so important.

Colon cancer

Case study

A 63-year-old man visits the family doctor because he has had blood in his stool for several weeks. He also suffers more and more from constipation, which surprises him as he is losing his appetite and doesn't eat much. He mentions that he has lost 5 kg in weight in the last three months.

Result of examination

The physical examination is unremarkable, including the rectal palpation. Bowel sounds are normal and there is no pressure pain on the stomach.

Diagnostic procedure

The blood seepage can be confirmed with a stool test. The colonoscopy conducted by a resident gastroenterologist reveals an ulcerated tumour of 2 cm in diameter in the descending colon ; tissue biopsies are taken and sent to the pathology department. Raised levels of the tumour markers CEA and CA 19-9 are found in the blood, typically produced by adenocarcinomas. After admission to a surgical clinic and a computed tomography (CT) of the abdominal and pelvic cavity and skull, diagnostics can exclude metastases.

Diagnosis

Colon cancer ( Fig. a ). Metastases have not been found in the liver, lung and brain. Of all the malignant tumours, colon carcinomas are the most common, along with tumours of the lung, breast and prostate. These can be detected very easily in the early stages through screening with a colonoscopy. The mortality rates have therefore fallen significantly in recent years.

Treatment

The Colon descendens and the Colon sigmoideum, including the lymph nodes along the A. mesenterica inferior, were removed with a hemicolectomy , and sent to the pathology department. The colon can be anastomosed with the rectum, maintaining continence, so that no artificial anus (Anus praeter) is required.

Further developments

On the following day, the patient starts taking in nutrition and is painfree apart from pain where the scar is healing well. Since several lymph nodes are identified as affected by the tumour in the pathological examination, the patient is referred to the ambulatory oncology unit. He there receives intravenous chemotherapy over the next few months on a regular basis which he tolerates very well after initial nausea. Postoperatively, the blood level of the tumour markers is lowered, so that a potential recurrence of the tumour would be indicated by any new increase. After 10 years in complete remission the patient can now be considered as healed.

Dissection lab

The large intestine is found immediately after opening the abdominal cavity

Here you have to look closely at the interrelated positions of the individual organs to each other.

because it surrounds the small intestine and separates the epigastrium from the hypogastrium. It is divided into several sections: the caecum (Caecum) with its appendix (Appendix vermiformis) is followed by the colon sections (Colon ascendens, Colon transversum, Colon descendens and Colon sigmoideum) and then the rectum, and the anal canal (Canalis analis). Since the descending colon is shifted to the rear body wall during development, it is located secondarily retroperitoneal. In contrast, the Colon sigmoideum is covered on all sides by the visceral peritoneum and is thus intraperitoneal. For the implementation of a hemicolectomy, knowledge of the neurovascular pathways which supply the individual intestinal segments is essential. This change developmentally affects the left colonic flexure which marks the transition from the transverse colon to the descending colon. The left-sided colon sections (Colon descendens and Colon sigmoideum) are therefore fed by branches from the A. mesenterica inferior, which originate from the abdominal part of the aorta and initially run retroperitoneally. The right-sided sections up to the transverse colon, in contrast, are supplied by the A./V. mesenterica superior.

The clinically important anastomosis of the A. mesenterica superior with the A. mesenterica inferior is called RIOLAN 's arcade. You can see it very clearly after preparation of the vascular arcades!

The corresponding vein (V. mesenterica inferior) ascends on the dorsal side of the pancreas and joins the other main veins which then build the portal vein (V. portae). Therefore colon tumour cells often metastasise via the venous blood into the liver. The regional lymph nodes along the colon connect to the collecting lymph nodes at the origin of the A. mesenterica inferior (Nodi lymphoidei mesenterici inferiores).

The lymph nodes are seldom easy to find, but their position can be easily tracked along the A. mesenterica.

Back to the clinic

During surgery, the entire A. mesenterica inferior with surrounding lymph nodes can be removed because it only provides the furthest sections of the large intestine. On the other hand, in the case of a tumour in the Colon ascendens, you could not remove the entire A. mesenterica superior, as it also supplies the small intestine and the pancreas.

Fig. a, Polypous colon carcinoma .

6.1

Development

6.1.1

Development of the epigastric situs

Fig. 6.1a–d, Development of the epigastric situs; peritoneum (green); peritoneum of the Recessus pneumatoentericus and the Bursa omentalis (dark red).

6.1.2

Peritoneal positioning

Fig. 6.2, Repositioning of the epigastric organs from the fifth week; paramedian section of the epigastrium.

Fig. 6.3, Repositioning of epigastric organs at the tenth week; cross-section of the hypogastrium at the level of the Flexura duodenojejunalis.

6.1.3

Development of the hypogastric situs

Fig. 6.4a–d, Schematic representation of the intestinal rotation. Intestinal segments and their mesenteries are highlighted in different colours: stomach and mesogastrium (purple), duodenum and mesoduodenum (blue), jejunum and ileum with associated mesenteries (orange), colon and mesocolon (ochre).

Fig. 6.5a–c, Schematic illustration of the relative peritoneal positioning; cross-sections; visceral peritoneum in green, parietal peritoneum in purple.

Peritoneal duplications
Structure Comment
Mesenterium

  • Dorsal suspension of intra- and retroperitoneal parts of the small and large intestines

  • Continued peritoneal duplication between the mesogastrium and mesorectum

  • Contains the neurovascular structures of the intestines

Omentum majus

  • Lig. gastrocolicum

  • Lig. gastrosplenicum

  • Lig. gastrophrenicum

  • Apron-shaped part

  • Apron-shaped duplication comprising several parts

  • Develops from the dorsal mesogastrium

  • Contains the neurovascular supply for the greater curvature of the stomach

Omentum minus

  • Lig. hepatogastricum

  • Lig. hepatoduodenale

  • Develops from the ventral mesogastrium (Mesohepaticum dorsale)

  • Contains the neurovascular pathways for the lesser curvature of the stomach

Lig. falciforme hepatis

  • Develops from the ventral mesogastrium anterior to the liver (Mesohepaticum ventrale)

  • Contains portacaval anastomoses to the ventral trunk wall

Lig. splenorenale Develops from the dorsal mesogastrium
Lig. phrenicocolicum

  • Develops from the dorsal mesogastrium

  • Forms the floor of the splenic recess

Clinical remarks

MECKEL's diverticula are common (3 % of the population), and usually occur in the section of the small intestine 100 cm orally of the ileocaecal valve. As they often contain disseminated gastric mucosa, they can simulate the clinical symptoms of appendicitis when inflamed and bleeding .

A disruption of the intestinal rotation may lead to malrotations (hypo- or hyperrotation). These may cause twisting of intestinal loops ( Volvulus ), potentially resulting in a bowel obstruction (ileus ). If sections of the intestines are hereby shifted into a different, abnormal position, this may complicate the diagnosis for appendicitis. The malrotation may be incomplete ( Fig. a ) or result in the duodenum crossing the Colon transversum ventrally ( Fig. b ). The completely reversed or mirror-image positioning of the organs is referred to as Situs inversus .

[ S701-L275 ]

6.2

Topography

6.2.1

Surface anatomy

Fig. 6.6, Regions of the abdomen; ventral view.

Regions of the abdomen
Region Projected organs
Right hypochondrium(Regio hypochondriaca dextra)

  • Liver (pain with swelling of the liver or fatty liver)

  • Gallbladder (inflammation of hepatic colic with presence of gall stones)

Epigastrium (upper abdomen)(Regio epigastrica)

  • Stomach (gastric ulcer)

  • Oesophagus (heartburn)

  • Colon transversum (bloating, obstruction, infarction, inflammation)

Left hypochondrium(Regio hypochondriaca sinistra) Spleen (splenic rupture, pain with swelling of spleen)
Right flank(Regio lumbalis dextra)

  • Right kidney (nephritis, renal colic)

  • Colon ascendens (bloating, obstruction with pain, infarction, inflammation)

Umbilical region (Regio umbilicalis) Small intestine (bloating, obstruction with pain, infarction, inflammation)
Left flank(Regio lumbalis sinistra)

  • Left kidney (nephritis, renal colic with kidney stones)

  • Colon ascendens (bloating, obstruction with pain, infarction, inflammation)

Right inguinal region = right groin(Regio inguinalis dextra)

  • Appendix vermiformis (appendicitis)

  • Inguinal canal (inguinal hernia)

Pubic region (Regio pubica)

  • Urinary bladder (urinary retention, urinary infection)

  • Rectum (bloating, obstruction with pain, infarction, inflammation)

Left inguinal region = left groin(Regio inguinalis sinistra)

  • Sigmoid colon (bloating, obstruction with pain, infarction, inflammation [particularly also diverticulitis])

  • Inguinal canal (inguinal hernia)

Fig. 6.7, Horizontal planes of the abdomen; ventral view.

Horizontal planes of the abdomen
Plane Vertebra Landmark Anatomical structure
A: Transpyloric plane(ADDISON’s plane) L1 Midway between pubic symphysis and the jugular notch Pylorus, fundus of gallbladder, Mesocolon transversum, pancreas, Flexura duodenojejunalis, Truncus coeliacus (T12/L1), origin of the hepatic portal vein, A. mesenterica superior, hilum of kidney with A. renalis (L2)
B: Subcostal plane L2–L3 Inferior border of the 10 th rib A. mesenterica inferior
C: Transumbilical plane L3–L4 Umbilicus
Supracristal plane L4 Iliac crest Aortic bifurcation (access for lumbar puncture)
D: Transtubercular plane L5 Tuberculum iliacum Origin of V. cava inferior
E: Interspinous plane Midsacrum Spina iliaca anterior superior Appendix vermiformis

Fig. 6.8, Cutaneous areas (dermatomes) of the anterior trunk wall with projection of the spinal nerves; ventral view.

6.2.2

Abdominal situs

Fig. 6.9, Position of the viscera, Situs viscerum, in the epigastrium, and greater omentum, Omentum majus; ventral view.

6.2.3

Epigastric situs

Fig. 6.10, Position of the viscera, Situs viscerum, in the epigastrium; ventral view. The ventral trunk wall and the rostral parts of the diaphragm have been removed.

Clinical remarks

For the physical examination of trauma patients, it is important to be familiar with the topography of the abdominal situs to exclude internal bleeding after an accident by employing ultrasound ( FAST sonography , Focused Assessment with Sonography for Trauma). The positioning of the ultrasound probe produces longitudinal and cross-sectional images of the following four regions:

  • 1.

    Right flank with view of the right-sided Recessus subphrenicus and Recessus subhepaticus (clinically also known as the hepatorenal recess of MORISON’s pouch ) surrounding the liver

  • 2.

    Left flank with view of the left-sided Recessus subphrenicus (clin.: KOLLER’s pouch ) surrounding the spleen

  • 3.

    Suprapubic region with view of the Excavatio rectouterina (pouch of DOUGLAS) in women and the Excavatio rectovesicalis (PROUST's space ) in men Fig. 6.19 )

  • 4.

    Infrasternal region with cranial view towards the pericardium to rule out a pericardial tamponade.

[ S701-L126 ]

6.2.4

Greater omentum

Fig. 6.11, Sections and neurovascular pathways of the greater omentum, Omentum majus; semi-schematic representation; ventral view.

Fig. 6.12, Sections and neurovascular pathways of the greater omentum, Omentum majus; sagittal section of the stomach, pancreas, Colon transversum, Bursa omentalis and Omentum majus; semi-schematic representation; lateral view from the left side.

6.2.5

Epigastric situs with Bursa omentalis

Fig. 6.13, Position of the viscera, Situs viscerum, in the epigastrium; ventral view.

Borders of the Bursa omentalis
Orientation Bordering structure Recessus
Ventral Omentum minus, stomach (posterior aspect), Lig. gastrocolicum –
Dorsal Pancreas (anterior aspect), aorta with Truncus coeliacus, left kidney (superior pole), left adrenal gland –
Cranial Liver (Lobus caudatus), diaphragm Recessus superior
Caudal Mesocolon transversum, inferior extension between the layers of the Omentum majus (if not fused) Recessus inferior
Left Spleen, Lig. gastrocolicum Recessus splenicus

Fig. 6.14, Position of the viscera, Situs viscerum, in the epigastrium; ventral view.

Clinical remarks

Like other recesses of the peritoneal cavity ( Fig. a ), the Bursa omentalis is of clinical significance due to potential entrapment of intestinal loops (internal hernias ), deposition of tumour cells in the case of peritoneal carcinosis, or bacterial accumulation in the case of peritonitis. During operations in the abdomen, the surgeon therefore inspects the Bursa omentalis , in order to avoid missing any disease.

For operations in the epigastrium, e. g. surgical interventions on the pancreas, there are three access routes ( Fig. b ) into the Bursa omentalis:

  • via the Omentum minus (1; Fig. 6.13 )

  • via the Lig. gastrocolicum (2; Fig. 6.14 )

  • via the Mesocolon transversum (3).

The illustration ( Fig. b ) below indicates the possible extension of the Recessus inferior of the Bursa omentalis if the two peritoneal layers of the Omentum majus have not fused sufficiently.

[ S701-L126 ]

6.2.6

Hypogastric situs

Fig. 6.15, Position of the viscera, Situs viscerum, in the hypogastrium; ventral view.

6.2.7

Hypogastric situs with recess of the peritoneal cavity

Fig. 6.16, Position of the viscera, Situs viscerum, in the hypogastrium; ventral view.

Fig. 6.17, Position of the viscera, Situs viscerum, in the hypogastrium; ventral view.

Clinical remarks

Of all the recesses in the body , small intestinal appendages (TREITZ hernia ) are most frequently trapped in the Recessus duodenales superior and inferior. This entrapment can cause a blockage (ileus) and bowel infarctions.

6.2.8

Mesenterium

Fig. 6.18, Mesentery of the small intestine, mesenterium, and large intestine, Intestinum crassum; ventral view.

6.2.9

Secondary retroperitoneal organs

Fig. 6.19, Position of the secondary retroperitoneal organs; ventral view.

Clinical remarks

In an upright position (seldom in bedridden patients), the most inferior extension of the abdominal cavity, the Excavatio rectovesicalis (PROUST's space ) in men, and the Excavatio rectouterina (pouch of DOUGLAS ) in women ( Fig. 6.20 ), may collect inflammatory exudate or pus with inflammation in the hypogastrium. An ultrasound may be used to check if the liquid is clear or not.

Ultrasound is also used for rapid exclusion of internal bleeding in trauma patients ( FAST-sonography, Focused Assessment with Sonography for Trauma) (Clinical remarks Fig. 6.10 ). Placing the ultrasound probe in a horizontal or orientation will offer longitudinal and cross-sectional views of the Excavatio rectouterina (pouch of DOUGLAS) in women and the Excavatio rectovesicalis (PROUST's space) in men to rule out a possible accumulation of blood in these pelvic peritoneal recesses.

6.2.10

Dorsal wall and recess of the peritoneal cavity

Fig. 6.20, Dorsal wall of the peritoneal cavity, Cavitas peritonealis, with recess, Recessus, and spleen, Splen [Lien]; ventral view.

6.2.11

Arteries of the abdomen

Fig. 6.21, Arteries of the abdominal viscera; semi-schematic illustration; ventral view.

6.2.12

Veins of the abdomen

Fig. 6.22, Portal vein, V. portae hepatis, with tributaries; semi-schematic illustration; ventral view.

6.2.13

Nerves of the abdominal organs

Fig. 6.23, Autonomic innervation of the abdominal organs; schematic drawing.

6.2.14

Truncus coeliacus

Fig. 6.24, Branches of the Truncus coeliacus; semi-schematic illustration; the liver is mobilised upwards; ventral view after removal of the Omentum minus.

Branches of the Truncus coeliacus
Branch Supply area Pathway
A. gastrica sinistra Stomach (lesser curvature), oesophagus (Pars abdominalis), in 10–20 % of the left lobe of the liver

  • Plica gastropancreatica

  • Lig. hepatogastricum

A. hepatica communis Stomach (lesser and greater curvature), duodenum, pancreas, Omentum majus, liver, gallbladder

  • Retroperitoneal

  • A. hepatica propria in the Lig. hepatoduodenale

  • A. gastrica dextra in the Lig. hepatogastricum

  • A. gastroomentalis dextra in the Lig. gastrocolicum

A. splenica Stomach (rear side, fundus, greater curvature), pancreas, Omentum majus, spleen

  • Retroperitoneal

  • Firstly the A. gastroomentalis sinistra within the Lig. gastrosplenicum, then within the Lig. gastrocolicum

Fig. 6.25, Topography of the Truncus coeliacus; ventral view; after removal of the Omentum minus.

6.2.15

Truncus coeliacus and A. mesenterica superior

Fig. 6.26, Origin of the A. mesenterica superior and branches of the Truncus coeliacus; ventral view; the stomach is folded back cranially and the pancreas is cut through.

6.2.16

A. mesenterica superior

Fig. 6.27, A. mesenterica superior; ventral view; Colon transversum folded upwards.

Branches of the A. mesenterica superior
Branch Supply area Pathway
A. pancreaticoduodenalis inferior Duodenum, pancreas Mesenterium
Aa. jejunales and ileales Jejunum, Ileum Mesenterium
A. ileocolica, A. colica dextra and A. colica media Ileum (terminal part), Caecum, Appendix vermiformis, Colon ascendens and Colon transversum

  • Mesenterium

  • Mesocolon

  • A. appendicularis in the mesentery of the Appendix vermiformis

Fig. 6.28, Pathway of the A. and V. mesenterica superior; ventral view; after opening of the mesentery with the Colon transversum folded back.

Clinical remarks

When parts of the colon are surgically removed, such as the Colon ascendens in a right hemicolectomy, it is important to keep in mind that besides the large intestine, the A. mesenterica superior also supplies the small intestine and should therefore not be removed completely.

6.2.17

A. mesenterica inferior

Fig. 6.29, A. mesenterica inferior; ventral view; Colon transversum folded back cranially.

Branches of the A. mesenterica inferior
Branch Supply area Pathway
A. colica sinistra Colon descendens and Colon transversum Mesocolon
Aa. sigmoideae Colon sigmoideum Mesocolon
A. rectalis superior

  • Rectum

  • Anal canal (Zona columnaris)

  • Retroperitoneal

  • Mesorectum

Fig. 6.30, Pathway of the A. and V. mesenterica inferior in the retroperitoneum; ventral view; Colon transversum folded back and small intestinal loops shifted to the right.

6.2.18

Neurovascular pathways in the mesenteries

Fig. 6.31, Pathway of the A. and V. mesenterica superior and concomitant lymphatic pathways and autonomic nerves in the mesentery; view from ventral; Colon transversum folded back cranially and small intestinal loops shifted to the left.

Fig. 6.32, Pathway of the A. and V. mesenterica inferior and concomitant lymphatic pathways and autonomic nerves in the retroperitoneal space; view from ventral; Colon transversum folded back cranially and the small intestinal loops shifted to the right.

6.3

Stomach

6.3.1

Projection of the stomach

Fig. 6.33, Projection of the stomach, Gaster, onto the ventral trunk wall; ventral view.

Fig. 6.34, Zone of referred pain ( HEAD's zone) of the stomach, schematic drawing; ventral view.

Fig. 6.35a and b, Projection of inner organs onto the body surface.

6.3.2

Structure of the stomach

Fig. 6.36a and b, Stomach, Gaster.

Clinical remarks

If the angle of HIS is lost, e. g. due to faulty attachment in the diaphragm (axial hiatus hernia ), this may lead to reflux of gastric juices with inflammation of the oesophagus (reflux oesophagitis ). If drug therapy to reduce acid production with proton pump blockers fails, an operation is needed to improve the closure by looping the fundus of the stomach around the oesophagus (NISSEN's fundoplication ).

6.3.3

Musculature of the stomach

Fig. 6.37a and b, Muscle layers of the stomach, Gaster; ventral view.

6.3.4

Internal surface of the stomach

Fig. 6.38, Stomach, Gaster, and duodenum; ventral view.

6.3.5

Structure of the wall of the stomach

Fig. 6.39, Structure of the wall of the stomach, Gaster; microscopic view.

Fig. 6.40, Gastric ulcer, Ulcus ventriculi.

Clinical remarks

More than 80 % of all gastric and duodenal ulcers are caused by the bacterium Helicobacter pylori. In addition, increased gastric acid production or a reduced formation of mucus, e. g. after taking painkillers containing the active substance acetylsalicylic acid, promote the formation of gastric ulcers. Accordingly, treatment involves eliminating bacteria with antibiotics, along with inhibiting the secretion of gastric acid. In the case of complications, surgical treatment is indicated. Complications may include a perforation into adjacent organs or the abdominal cavity, resulting in life-threatening peritonitis, or the erosion of a gastric artery ( Fig. 6.42 ), leading to heavy bleeding .

6.3.6

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here

Related Posts