he peritoneum is the serous membrane that lines the abdominal cavity. It is composed of mesothelial cells that are supported by a thin layer of fibrous tissue and is embryologically derived from the mesoderm.

1. ABDOMINAL CAVITY
& PERITONEUM
Abhijit Bhoyar

2. INTRODUCTION
• Abdominal cavity is the largest cavity.
• It encloses the peritoneal cavity between its parietal and visceral
layers.
• Parietal layer clings to the wall of parities while visceral layer is
intimately adherent to viscera concerned.
• So their vascular supply and nerve supply are same as the
parities and viscera, respectively.

3. Conti..
• There are very lengthy organs in the abdominal cavity. These
had to be disciplined with limited movements for proper
functioning of the gut in particular and the body in general.
• Infections involving the parietal peritoneum impart protective
‘board-like rigidity’ to the abdominal wall.
• Referred pain from the viscera to a distant area is due to somatic
and sympathetic nerves reaching the same spinal segment

4. ABDOMINAL REGIONS
•For the purpose of describing the location of
viscera, the abdomen is divided into nine
regions by four imaginary planes, two
horizontal and two vertical.

6. Conti..
• The horizontal planes are the trans-pyloric and
transtubercular planes.
• The vertical planes are the right lateral and the left lateral
planes.
• The pelvic cavity lies below and posterior to the abdominal
cavity.

8. Conti..
• The trans-pyloric plane passes midway between the
suprasternal notch and the pubic symphysis.
• It lies roughly a hand’s breadth below the xiphisternal joint.
• Anteriorly, it passes through the tips of the ninth costal
cartilage; and posteriorly through the body of vertebra L1
near its lower border.

9. Conti..
• Organs present on this plane are pylorus of stomach
beginning of duodenum, neck of pancreas and hila of the
kidneys.
• The transtubercular plane passes through the tubercles of the
iliac crest and the body of vertebra L5 near its upper border.

10. Conti..
• The right and left lateral planes correspond to the
midclavicular or mammary lines.
• Each of these vertical planes passes through the midinguinal
point and crosses the tip of the ninth costal cartilage.

12. Conti..
• The nine regions marked out in this way are arranged in three
vertical zones—median, right and left.
• From above downwards, the median regions are epigastric,
umbilical and hypogastric.
• The right and left regions, in the same order, are
hypochondriac, lumbar and iliac.
• Liver chiefly occupies the right hypochondrium.
• Stomach and spleen occupy the left hypochondrium.

13. Conti..
• Duodenum lies in relation to posterior abdominal wall.
• Coils of jejunum and ileum fill up the umbilical, lumbar and
iliac regions.
• Large intestine lies at the periphery of abdominal cavity,
caecum, ascending colon on right side, descending colon on
left side and transverse colon across the cavity
• The pelvic cavity lies postero-inferiorly between pubic
symphysis anteriorly and concavity of sacrum including
coccyx posteriorly.

14. PERITONEUM
• The peritoneum (Greek stretched over) is a large serous
membrane lining the abdominal cavity.
• Histologically it is composed of an outer layer of fibrous
tissue, which gives strength to the membrane and an inner
layer of mesothelial cells which secrete a serous fluid which
lubricates the surface, thus allowing free movements of
viscera.

16. Conti..
a. An outer or
parietal layer
b. An inner or
visceral layer
c. Folds of
peritoneum by
which the viscera
are suspended.
The peritoneum is in the form of a closed sac which is
invaginated by a number of viscera. As a result, the
peritoneum is divided into:
The peritoneum which is a
simple cavity, before being
invaginated by viscera
becomes highly
complicated

17. Parietal Peritoneum
• It lines the inner surface of the abdominal and pelvic walls
and the lower surface of the diaphragm.
• It is loosely attached to the walls by extraperitoneal
connective tissue and can, therefore, be easily stripped.

18. Conti..
• Embryologically, it is derived from the somatopleuric layer
of the lateral plate mesoderm.
• Its blood supply and nerve supply are the same as those of
the overlying body wall. Because of the somatic innervation,
parietal peritoneum is pain sensitive.

19. Visceral Peritoneum
• It lines the outer surface of the viscera, to which it is firmly
adherent and cannot be stripped. In fact, it forms a part and
parcel of the viscera.
• Embryo logically, it is derived from the splanchopleuric layer
of the lateral plate mesoderm.
• Its blood supply and nerve supply are the same as those of
the underlying viscera. Because of the autonomic
innervation, visceral peritoneum evokes pain when viscera is
stretched, ischemic or distended

20. Folds of Peritoneum
• Many organs within the abdomen are suspended by folds of
peritoneum. Such organs are mobile.
• The degree and direction of mobility are governed by the size
and direction of the peritoneal fold.
• Other organs are fixed and immobile. They rest directly on
the posterior abdominal wall, and may be covered by
peritoneum on one side..

21. Conti..
• Such organs are said to be retroperitoneal.
• Some organs are suspended by peritoneal folds in early
embryonic life, but later become retroperitoneal.
• Apart from allowing mobility, the peritoneal folds provide
pathways for passage of vessels, nerves and lymphatic.

22. Conti..
• Peritoneal folds are given various names:
a. In general, the name of the fold is made up of the prefix ‘mes’ or
‘meso’ followed by the name of the organ, e.g. the fold suspending
the small intestine or enteron is called the mesentery; and a fold
uspending part of the colon is called mesocolon.
b. Large peritoneal folds attached to the stomach are called omenta;
singular of which is omentum which means cover.

23. Conti..
c. In many situations, double-layered folds of peritoneum
connect organs to the abdominal wall or to each other. Such
folds are called ligaments.
• These may be named after the structures they connect. For
example, the gastrosplenic ligament connects the stomach to
the spleen.
• Other folds are named according to their shape, e.g. the
triangular ligaments of the liver. Some of the larger
peritoneal folds are considered in this chapter, while others
are considered along with the organs concerned.

25. Peritoneal Cavity
The viscera which
invaginate the peritoneal
cavity completely fill it so
that the cavity is reduced to
a potential space separating
adjacent layers of
peritoneum.

26. Conti..
• The peritoneal cavity is divided broadly into two parts.
• The main, larger part is known as the greater sac, and the
smaller part, situated behind the stomach, the lesser
omentum and the liver, is known as the omental bursa or
lesser sac.

27. Sex Differences
• In the male, the peritoneum is a closed sac lined by
mesothelium or flattened epithelium.
• The female peritoneum has the following distinguishing
features.
1 The peritoneal cavity communicates with the exterior
through the uterine tubes.
2 The peritoneum covering the ovaries is lined by cubical
epithelium.
3 The peritoneum covering the fimbria is lined by columnar
ciliated epithelium.

28. Functions of Peritoneum
1 Movements of
viscera:
2 Protection of
viscera:
3 Absorption
and dialysis:
4 Healing power
and adhesions:
5 Storage of
fat:
6 Provides
passage for
nerves,
vessels and
lymphatics

29. Functions of Peritoneum
1 Movements of viscera:
• The chief function of the peritoneum is to provide a slippery
surface for free movements of abdominal viscera.
• This permits peristaltic movements of the stomach and
intestine, abdominal movements during respiration and
periodic changes in the capacity of hollow viscera associated
with their filling and evacuation.
• The efficiency of the intestines is greatly increased as a result
of the wide range of mobility that is possible because the
intestines are suspended by large folds of peritoneum.

30. Conti..
2 Protection of viscera:
• The peritoneum contains various phagocytic cells which
guard against infection.
• Lymphocytes present in normal peritoneal fluid provide both
cellular and humoral immunological defence mechanisms.

31. Conti..
• The greater omentum has the power to move towards sites of
infection and to seal them thus preventing spread of
infection.
• For this reason, the greater omentum is often designated as
the ‘policeman of the abdomen’.

32. Conti..
3 Absorption and dialysis:
• The mesothelium acts as a semipermeable membrane across
which fluids and small molecules of various solutes can pass.
Thus, the peritoneum can absorb fluid effusions from the
peritoneal cavity.
• Water and crystalloids are absorbed directly into the blood
capillaries, whereas colloids pass into lymphatics with the aid
of phagocytes.

33. Conti..
• The greater absorptive power of the upper abdomen or
subphrenic area is due to its larger surface area and because
respiratory movements aid absorption.
• Therapeutically, considerable volumes of fluid can be
administered through the peritoneal route.
• Conversely, metabolites, like urea can be removed from the
blood by artificially circulating fluid through the peritoneal
cavity. This procedure is called peritoneal dialysis.

34. Conti..
4 Healing power and adhesions: The mesothelial cells of the
peritoneum can transform into fibroblasts which promote healing of
wounds.
5 Storage of fat: Peritoneal folds are capable of storing large amounts
of fat, particularly in obese persons.
6 Provides passage for nerves, vessels and lymphatics to and from the
suspended viscera.

35. CLINICAL ANATOMY OF PERITONEUM
• Collection of free fluid in the peritoneal cavity is known as
ascites. Common causes of ascites are cirrhosis of the liver,
tubercular peritonitis, congestive heart failure, and malignant
infiltration of the peritoneum. Veins also get prominent in
cirrhosis of liver.

36. Conti..
• Fluid from the (peritoneal cavity) may be removed by
puncturing the abdominal wall either in the median plane
midway between the umbilicus and pubic symphysis, or at a
point just above the anterior superior iliac spine. The
procedure is called paracentesis.
• Urinary bladder must be emptied before the procedure

37. Conti..
• Inflammation of the peritoneum is called peritonitis. It may
be localized when a subjacent organ is infected; or may be
generalized. The latter is a very serious condition.
• The presence of air in the peritoneal cavity is called
pneumoperitoneum. It may occur after perforation of the
stomach or intestines.

38. Conti..
• Laparoscopy is the examination of the peritoneal cavity
under direct vision using an instrument called laparoscope.
• Opening up the abdominal cavity by a surgeon is called
laparotomy.
• Greater omentum limits the spread of infection by sealing off
the site of ruptured vermiform appendix or gastric ulcer and
tries to delay the onset of peritonitis. It is called ‘abdominal
policeman’.

39. Conti..
• Inflammation of parietal peritoneum causes localized severe
pain and rebound tenderness on removing the fingers.
• Peritoneal dialysis is done in case of renal failure. The
procedure removes the urea, etc. as it diffuses through blood
vessels into the peritoneal cavity.

40. Questions Ask
• Enlist the regions of abdominal cavity.
• Define peritoneum.
• Describe layers of peritoneum.
• Functions of peritoneum.
• Applied/Clinical anatomy of peritoneum.