TOPIC 218.
LOWER PART OF THE ABDOMINAL CAVITY
ABDOMINAL CAVITY → space in the trunk below the diaphragm. It is divided into the
abdominal cavity proper and pelvic cavity.
1. BORDERS
- Anterolateral:
Rectus abdominis
External oblique
Internal oblique
Transversus abdominis
- Posterior:
Lumbar segment of the spine
Psoas major
Quadratus lumborum
- Superior – diaphragm
- Inferior:
Iliac bones
Pelvic diaphragm
2. DIVISION
The abdominal cavity is divided into 2 storeys:
- UPPER STOREY
- LOWER STOREY
LOWER PART OF THE ABDOMINAL CAVITY
1. BORDERS
- Superior – transverse mesocolon
- Inferior – pelvic cavity
2. CONTENTS
- Right and left paracolic canals (gutters)
- Right and left mesenteric sinuses
- Mesentery
- Sigmoid mesocolon
- Duodenojejunal recess
- Superior and inferior ileocaecal recesses
- Large and small intestines
- Rectovesical pouch – in males
- Rectouterine pouch + uretrovesical pouch – in females
- Pelvic organs
PERITONEUM
- Serous membrane lining the abdominal and pelvic cavities
In males: closed
In females: communicates with the external environment by the uterine tubes
- Consists of 2 layers:
Parietal peritoneum
Visceral peritoneum
*Between them, the peritoneal cavity is located → contains peritoneal fluid
- The extraperitoneal tissue (tela subserosa) contains a large amount of fatty tissue that is
lodged between the peritoneum and the abdominal wall.
Richly developed on the posterior abdominal wall
Poorly developed on the anterior abdominal wall
1. PARIETAL PERITONEUM
- Fibrous tissue
- Lines the inner surface of the abdominal and pelvic cavities → forms the outer limit of
the peritoneal cavity
- Receives the same arterial and nerve supplies as the wall it lines
- More sensitive to pain because it is innervated by SOMATIC INNERVATION
oIn the pelvis – devoid of somatic innervation
2. VISCERAL PERITONEUM
- Composed of mesothelial cells
- Covers the outer surface of the abdominal visceral organs
- Receives the same arterial and nerve supplies as the organ it covers
- Innervated by AUTONOMIC INNERVATION
- Pain is only felt when the organ is distended or ischemic
RELATIONS OF VISCERAL ORGANS TO PERITONEUM
1. INTRAPERITONEAL ORGANS
- Completely (4 sides) covered by peritoneum
- Generally mobile → can be moved away to access deeper organs in surgery and prone to
herniation
- They are:
Stomach
Bulbus duodeni of the superior part of the duodenum
Jejunum
Ileum
Appendix
Transverse colon
Sigmoid colon
Supraampular part of the rectum
Spleen
Ovaries
2. MESOPERITONEAL ORGANS
- Covered by the peritoneum by 3 sides
- Degree of mobility is between the intraperitoneal and extraperitoneal organs
- They are:
Liver
Gall bladder
Ascending part of duodenum
Caecum
Ascending colon
Descending colon
Ampular part of the rectum
Urinary bladder (when distended)
Uterus
3. EXTRAPERITONEAL (RETROPERITONEAL) ORGANS
Covered by peritoneum by only 1 side
- Located in the retroperitoneal space
- Not movable at all
- They are:
Descending and horizontal parts of the duodenum
Anal canal
Pancreas
Kidneys
Adrenal glands
Ureters
Urinary bladder (when empty)
Major vessels like the abdominal aorta and the inferior vena cava
PERITONEAL FORMATION
1. MESENTERY
- Double layer peritoneum that occurs as a result of invagination of the peritoneum by the
small intestine.
- Connects the small intestine to the posterior abdominal wall
- Contains the neurovascular bundles that supply and drain the small intestine
- Forms the root of the mesentery (radix mesenterium) that divides the mesenteric sinus
into right and left.
oStarts from the 2nd lumbar vertebra and ends at the right iliac fossa
2. MESOCOLON
- It is the mesentery of the large intestine
- Contains the neurovascular bundles that supply and drain the parts of the large intestine
where they are connected to the posterior abdominal wall by mesocolon.
- Types of mesocolon:
Mesocolon transversum – connects the transverse colon to the posterior
abdominal wall
Mesocolon sigmoideum – connects the sigmoid colon to the posterior abdominal
wall
Mesoappendix (mesenteriolum appendicis vermiformis) – connects the appendix
to the posterior abdominal wall
3. OMENTUM
Duplicature of the mesentery which contains a large amount of fatty tissue.
- LESSER OMENTUM (Omentum Minus)
oStretches from the portal triad to the lesser curvature of the stomach and
proximal part of the duodenum
Formed by:
Hepatogastric ligament
Hepatoduodenal ligament
- GREATER OMENTUM (Omentum Majus)
Stretches from the greater curvature of the stomach to the transverse colon and
covers loops of the small intestine
Formed by 4 peritoneal layers → which are fused to form 2 laminae:
Anterior lamina
Starts from the greater curvature of the stomach and descends
anterior to the transverse colon
Descends almost up to the pubic bones and ascens to form the
posterior lamina.
The ligament which connects the stomach to the transverse colon
= gastrocolic ligament
Posterior lamina
Blends with the transverse colon and ascends up to the anterior
border of the pancreas where it is separated into 2 layers:
1 covers the anterior part of the pancreas and goes up to
the diaphragm
2 covers the inferior part of the pancreas and is continuous
with the mesocolon transversum
4. LIGAMENTS
- Connect the adjacent organs or connect the organ to the abdominal wall
- The nomenclature of the ligament reflects the organs that it connects:
Falciform ligament – connects the liver to the abdominal wall
Coronary ligament – connects the liver to the diaphragm
Triangular ligament of the liver
Hepatogastric ligament – connects the liver to the lesser curvature of the stomach
Hepatoduodenal ligament – connects the liver to the duodenum
Hepatocolic ligament – connects the liver to the colon
Hepatorenal ligament – connects the liver to the right kidney
Gastrophrenic ligament – connects the stomach to the diaphragm
Gastrolienal (gastrosplenic) ligament – connects the stomach to the spleen
Gastrocolic ligament – connects the stomach to the transverse colon
Gastropancreatic ligament – connects the stomach to the pancreas
Phrenicoesophageal ligament – connects the diaphragm to the oesophagus
Phrenicocolic ligament – connects the diaphragm to the colon
Phrenicorenal ligament – connects the diaphragm to the kidney
Phrenicolienal ligament – connects the diaphragm to the spleen
Pancreaticolienal ligament – connects the pancreas to the spleen
Lienorenal ligament – connects the spleen to the left kidney
Pyloropancreatic ligament – connects the pylorus to the pancreas
Duodenorenal ligament – connects the duodenum to the right kidney
5. RECESSES
They are pouches that are formed by the peritoneal folds. They are places of retroperitoneal
herniation.
- Duodenojejunal recess
- Superior ileocaecal recess
- Inferior ileocaecal recess
- Retrocaecal recess
- Intersigmoid recess
6. FOLDS
They are the reflection of the peritoneum that rises from the abdominal wall by the
underlying structures.
- Gastropancreatic fold
- Ileocaecal fold
- Superior duodenal fold
- Inferior duodenal fold
- Median umbilical fold
- Medial umbilical fold
- Lateral umbilical fold
7. SINUSES
There are 2 sinuses, which are the right and left mesenteric sinuses
- RIGHT MESENTERIC SINUS
Closed
BORDERS
Medial – root of the mesentery
Lateral – ascending colon
Superior – transverse colon
- LEFT MESENTERIC SINUS
Communicates with the lesser pelvis
BORDERS
Medial – descending colon
Lateral – root of the mesentery
Inferior – sigmoid colon
8. PARACOLIC CANALS (lateral abdominal canals)
They consist of 2 paracolic canals, which are the right and left.
- RIGHT PARACOLIC CANAL
Communicates with the right hepatic bursa
BORDERS
Medial – ascending colon
Lateral – parietal peritoneum
Inferior – caecum
- LEFT PARACOLIC CANAL
Communicates with the lesser pelvis
BORDERS
Medial – descending colon
Lateral – parietal peritoneum
Superior – phrenicocolic ligament
