Lecture 2 Flashcards
What forms the superior boundary of the abdomen?
Diaphragm, inferior thoracic aperture
What forms the inferior boundary of the abdomen?
Iliac crest, inguinal ligament, pelvic inlet
What forms the posterior boundary of the abdomen?
Lumbar vertebral column, psoas major, quadratus lumborum, (abdominal wall muscles)
What forms the lateral and anterior boundaries of the abdomen?
Abdominal wall muscles
List the layers of the abdominal wall from the most superficial to most deep.
Skin Camper's Fascia Scarpa's Fascia External Oblique Internal Oblique Transversus Abdominis Transversalis Fascia (Extraperitoneal Fascia) Parietal Peritoneum
What are the two layers of the superficial fascia?
Camper’s Fascia and Scarpa’s Fascia
In the abdomen, where is the superficial fascia similar to that found elsewhere in the body?
Above the umbilicus
What happens to the superficial fascia below the umbilicus?
It divides into 2 layers: Camper’s fascia and Scarpa’s fascia
Describe the two layers of the superficial fascia. Which layer is more deep?
Camper’s: thick, yellow, fatty layer all over the abdomen
Scarpa’s: thinner, orange, membranous layer continuous with various other fascia (deep)
What are the functions of the muscles of the abdominal wall? What other feature aids the ability to move?
Provide stability and allow abdominal viscera to move. No bony structures between ribs and pelvis also allows movement.
What are the muscles of the abdominal wall?
Rectus Abdominis
External Oblique
Internal Oblique
Transversus Abdominis
What is the origin of Rectus Abdominis?
Pubic Tubercle, Crest, and Symphysis
What is the insertion of Rectus Abdominis?
Costal cartilages of ribs 5-7 and xiphoid process
What are the actions of Rectus Abdominis?
- Flex trunk
- Support/compress abdominal wall (Secondary respiratory muscles for forcing expiration)
What is the nerve supply of the Rectus Abdominis?
Anterior rami of thoracic spinal nerves
What is the origin of the external oblique muscle?
Ribs 5-12
What is the insertion of the external oblique muscle?
Iliac crest and linea alba via aponeurosis
Where does the aponeurosis of the external oblique stretch from and to?
From xiphoid process to pubic symphysis
What does the lower border of external oblique form?
Inguinal ligament
What are the actions of external oblique?
- Flex trunk (both)
- Turn to opposite side/bend trunk to same side (single)
What is the nerve supply of external oblique?
Anterior rami of thoracic spinal nerve
What is the fibre direction of external oblique?
Infero-medial
What is the origin of internal oblique?
Thoracolumbar fascia, inguinal ligament and iliac crest
What is the insertion of internal oblique?
Ribs 9-12
What are the actions of the internal oblique muscles?
- Flex trunk (both)
- Bend and turn trunk to same side (single)
What is the nerve supply of internal oblique?
Anterior rami of thoracic spinal nerves (some L1)
What is the fibre direction of internal oblique muscles?
Supero-medial
What is the origin of transversus abdominis?
Thoracolumbar fascia, iliac crest, inguinal ligament, costal cartilage of ribs 7-12
What is the insertion of transversus abdominis?
Linea alba, pubic crest, pectineal line
What is the action of the transversus abdominis?
Supports abdominal wall
What is the nerve supply of transversus abdominis?
Anterior rami of thoracic spinal nerves (some L1)
What is the fibre direction of transversus abdominis?
Transverse
Describe the upper 3/4 of the rectus sheath
All 3 abdominal wall muscles surround rectus abdominis. Internal oblique splits around rectus abdominis. External oblique stays above and transversus abdominis stays below.
Describe the lower 1/4 of the rectus sheath. What does this allow?
Rectus sheath over front of rectus abdominis only. Behind = transversalis fascia and parietal peritoneum. Allows vessels to pass through.
Where is the lower 1/4 of the rectus sheath found?
Below the arcuate line
Where is the arcuate line?
Roughly halfway along line from umbilicus to pubic bone
What are the main arteries that supply the abdomen? Which is larger?
Superior epigastric (from internal thoracic) Inferior epigastric (from external iliac) Larger
What is the pathway of the arterial supply to the abdomen?
Both arteries run underneath Rectus Abdominis (on top of transversalis fascia and within the rectus sheath) and anastamose together.
What are the other arteries that surround the abdomen region?
Deep circumflex iliac Musculophrenic branches Intercostal Lumbar Iliolumbar
What are the two types of veins that drain the abdomen? Where do they drain to?
- Thoracoepigastric veins drain to axillary
- Superficial epigastric veins drain to femoral
What are the types of nerves that drain the abdomen?
- Lateral cutaneous branches 7-12 intercostal nerves and iliohypogastric nerve (L1)
- Anterior cutaneous branches of 7-12 intercostal nerves
What is the pathway of the nerves that drain the abdomen?
Travel in neurovascular plane between internal oblique and transversus abdominis before piercing the muscular wall to reach the skin
What is the skin, muscle, and parietal peritoneum of the abdomen suppled by?
T7-12 (intercostal) and L1 (iliohypogastric/ilioinguinal) spinal nerves
What exists between the two layers of the peritoneum? What is its purpose?
A small amount of serous fluid. Reduces friction.
Describe the mesentery.
Visceral peritoneum comes back around on itself to form a mesentery anchoring the viscera to the posterior body wall.
What is the parietal peritoneum sensitive to?
Pain, touch, temperature, pressure
What is the nervous supply of the parietal peritoneum?
- Somatic nerves to body wall (thoracic and lumbar nerves)
- Phrenic nerve (up by diaphragm)
- Obturator nerve (down in pelvis)
What are the visceral peritoneum and mesenteries sensitive to?
Stretching and distension e.g. when you’ve eaten too much
What fibres of which nervous system are supplied by the visceral peritoneum and mesenteries?
Afferent nerve fibres of autonomic nervous system (ANS)
What is the GI tract suspended by?
Mesenteries
The midgut and hindgut are only suspended ____ __________
One mesentery (dorsal)
What is the foregut suspended by?
Both a ventral and dorsal mesentery
What is meant by intraperitoneal?
Completely contained in visceral peritoneum and suspended by a mesentery.
Identify the intraperitoneal structures of the abdomen
Stomach, liver, gall bladder, spleen, proximal duodenum, smal intestine, appendix, transverse colon, sigmoid colon
What is meant by retroperitoneal?
Lays between peritoneum and body wall
What is the inguinal ligament formed by?
The external oblique rolling in on itself to create a gap for femoral vessels to pass underneath
Describe the linea alba
Midline, where the aponeuroses of the muscles meet
What issue can occur below the arcuate line?
Weak so can end up with hernia
Identify the retroperitoneal structures of the abdomen
Kidneys, pancreas, distal duodenum, ascending and descending colon, upper 2/3 of rectum
What is the greater sac?
Peritoneal cavity proper: everything that is not the lesser sac
Where is the lesser sac found?
Behind lesser omentum and stomach. It spans from liver to stomach.
What is the lesser sac created due to?
Rotation of the foregut structures - drags lesser omentum around to create a pocket
What are two other names for omental foramen?
Epiploic foramen or Foramen of Winslow
What is the omental foramen bounded by anteriorly and posteriorly?
A: Free edge of lesser omentum
P: IVC
What does the free edge of the lesser omentum contain?
Portal triad
What are paracolic gutters?
Peritoneal sulci lateral to the ascending/descending colons
What do paracolic gutters create a pathway for?
Peritoneal fluid (or pus, blood, bile etc) to migrate around the abdomen
The paracolic gutter on which side is more clinically significant? Why?
Right hand side
- Larger
- Left side limited
- Right side peritoneum is continuous with peritoneum of hepatic recess and lesser sac
What is the left paracolic gutter limited by?
The phreno-colic ligament, which blocks a bit of the passageway so fluid doesn’t move as freely.
Describe how migration of fluid can present as acute appendicitis
When sitting, fluid moves down the paracolic gutters due to gravity. Pressure build-up leads to pain in lower right quadrant. Presents like appendicitis, but may originate from the liver.
Describe what happens to fluid in the paracolic gutters when we are supine.
Fluid will enter lesser sac. When standing, it will have nowhere to go, so will collect there. If pus and bile are occupying space that they are not meant to, can form abscesses, which can be very distant from the site of pathology.
