Lecture 5: Peritoneal cavity and abdominal wall muscles Flashcards
Which two cavities of the body are continuous with each other?
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)
What does viscera mean?
Internal organs in the main cavity of the body, especially those in the abdomen
What is the boundary of the peritoneal cavity?
Mesothelial layers which secrete fluid
the peritoneal cavity is found within the abdominal cavity
What organs does the peritoneal cavity envelope?
- envelopes the more superficial viscera (liver/stomach/small intestine)
- rests on anterior surface of deeper viscera (colon/spine/kidneys)
What are the intra-peritoneal organs?
Liver, stomach and small intestine: these are fully enveloped (not fully surrounded) by the peritoneal cavity
What are the retroperitoneal organs?
Behind the periotoneum
Spine, large intestine, kidneys
What is within the peritoneal cavity?
Nothing! except some fluid
What is a mesentery?
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)
What is a peritoneal ligament?
Double fold of peritoneum which connects 2 viscera e.g. b/w the liver and stomach
What is the function of the peritoneal cavity?
Holds viscera in position
What is the function of fluid in the peritoneal cavity?
When the intra-peritoneal organs touch each other, there is no friction, they just glide over each other
Does the stomach have a mesentery?
No, because the double fold of peritoneum allows vessels from the retroperitoneal space is too short to be classed as a mesentery
What is an aponeurosis?
A flattened tendon
What runs down the midline of the abdomen?
Linea alba (white line), a fibrous structure
What is the origin/insertion of the external oblique muscles?
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
Where is the aponeurosis of the external oblique muscle?
Inferiorly and medially, the muscle belly being more lateral and superior
-the attachment to the inguinal ligament is via the aponeurosis of the muscle
What forms the inguinal ligament?
The external oblique aponeurosis, which rolls up
What are the actions of the external oblique muscle?
- compress the abdominal viscera
- flex the trunk (lean forward) if both contract at same time
- rotate core/trunk
What is the origin/insertion of the internal oblique muscle?
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
What is the action of the internal oblique muscle?
- 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
What is the insertion/origin of the transverse abdominus?
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
What is the action of the transverse abdominus?
-contraction on both sides compress abdominal contents, important in core stability
What is the nerve supply to the abdominal muscles?
Anterior rami T7-T12
internal oblique and transverse abdominus also get their nerve supply from L1
Where does the rectus abdominus muscle originate from?
Paired muscle that runs vertically
Origin: pubic crest, pubic tubercle, pubic symphysis
Insertion: Costal cartilages of ribs 5-7
What are the breaks in the rectus abdominus called?
Tendinous intersections (6 pack)
How do the aponeurosis relate to the rectus abdominus muscle?
-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
What happens to the aponeurosis below the arcuate line?
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
What is the rectus sheath?
Aponeurosis’ which enclose the rectus abdominus muscles
