Lecture 5: Peritoneal cavity and abdominal wall muscles

Question 1

Which two cavities of the body are continuous with each other?

Answer 1

Abdominal cavity and the pelvic cavity (pelvic brim is a landmark which separates them but it is continuous, so parts of the abdominal cavity can just hang into the pelvic cavity)

Question 2

What does viscera mean?

Answer 2

Internal organs in the main cavity of the body, especially those in the abdomen

Question 3

What is the boundary of the peritoneal cavity?

Answer 3

Mesothelial layers which secrete fluid

the peritoneal cavity is found within the abdominal cavity

Question 4

What organs does the peritoneal cavity envelope?

Answer 4

• envelopes the more superficial viscera (liver/stomach/small intestine)
• rests on anterior surface of deeper viscera (colon/spine/kidneys)

Question 5

What are the intra-peritoneal organs?

Answer 5

Liver, stomach and small intestine: these are fully enveloped (not fully surrounded) by the peritoneal cavity

Question 6

What are the retroperitoneal organs?

Answer 6

Behind the periotoneum

Spine, large intestine, kidneys

Question 7

What is within the peritoneal cavity?

Answer 7

Nothing! except some fluid

Question 8

What is a mesentery?

Answer 8

When there are two layers of peritoneum e.g. after enveloping the stomach/small intestine, and these form channels which allows blood vessels/lymphatics etc. to go from the retroperitoneal space to organs without breaching the peritoneal cavity
(connect viscera to the retroperitoneal space)

Question 9

What is a peritoneal ligament?

Answer 9

Double fold of peritoneum which connects 2 viscera e.g. b/w the liver and stomach

Question 10

What is the function of the peritoneal cavity?

Answer 10

Holds viscera in position

Question 11

What is the function of fluid in the peritoneal cavity?

Answer 11

When the intra-peritoneal organs touch each other, there is no friction, they just glide over each other

Question 12

Does the stomach have a mesentery?

Answer 12

No, because the double fold of peritoneum allows vessels from the retroperitoneal space is too short to be classed as a mesentery

Question 13

What is an aponeurosis?

Answer 13

A flattened tendon

Question 14

What runs down the midline of the abdomen?

Answer 14

Linea alba (white line), a fibrous structure

Question 15

What is the origin/insertion of the external oblique muscles?

Answer 15

Origin: 5th-12th ribs
Muscle fibres then come down in an infero-oblique direction towards the linea alba
Insertion: Iliac crest, inguinal ligaments, linea alba

Question 16

Where is the aponeurosis of the external oblique muscle?

Answer 16

Inferiorly and medially, the muscle belly being more lateral and superior
-the attachment to the inguinal ligament is via the aponeurosis of the muscle

Question 17

What forms the inguinal ligament?

Answer 17

The external oblique aponeurosis, which rolls up

Question 18

What are the actions of the external oblique muscle?

Answer 18

• compress the abdominal viscera
• flex the trunk (lean forward) if both contract at same time
• rotate core/trunk

Question 19

What is the origin/insertion of the internal oblique muscle?

Answer 19

Origin: lateral portion of the inguinal ligament, iliac crest, thoracolumbar facia
Direction of fibres are perpendicular to external oblique
Insert: into the lower 3/4 ribs, linea alba via its aponeurosis, pubic crest

Question 20

What is the action of the internal oblique muscle?

Answer 20

• compress abdominal viscera
• flex trunk if both muscles contract at same time
• ipsilateral rotators due to direction of fibres (same side rotators) when only one of the muscles contracts

Question 21

What is the insertion/origin of the transverse abdominus?

Answer 21

Origin: costal cartilages of lower ribs, thoracolumbar fascia, medial lip of iliac crest, portion of inguinal ligament
Fibres run in transverse direction
Insertion: via aponeurosis which blends with the linea alba, some fibres attach at the pubic crest along with the internal oblique

Question 22

What is the action of the transverse abdominus?

Answer 22

-contraction on both sides compress abdominal contents, important in core stability

Question 23

What is the nerve supply to the abdominal muscles?

Answer 23

Anterior rami T7-T12

internal oblique and transverse abdominus also get their nerve supply from L1

Question 24

Where does the rectus abdominus muscle originate from?

Answer 24

Paired muscle that runs vertically
Origin: pubic crest, pubic tubercle, pubic symphysis
Insertion: Costal cartilages of ribs 5-7

Question 25

What are the breaks in the rectus abdominus called?

Answer 25

Tendinous intersections (6 pack)

Question 26

How do the aponeurosis relate to the rectus abdominus muscle?

Answer 26

-external oblique apo goes over the top of the rectus abdom
-internal oblique apo encloses the rectus abdom
-transverse abdom apo goes under the rectus abdom
These all join between/in middleof the pair to form the linea alba

Question 27

What happens to the aponeurosis below the arcuate line?

Answer 27

All of the aponeurosis go anterior to the rectus abdominus muscles.
Therefore the posterior of the rectus abdominus muscles lie on the transversalis fascia and then the parietal peritoneum

Question 28

What is the rectus sheath?

Answer 28

Aponeurosis’ which enclose the rectus abdominus muscles