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Questions and Answers
Which spinal nerve is responsible for supplying the area of skin just above the inguinal ligament and the symphysis pubis?
Which spinal nerve is responsible for supplying the area of skin just above the inguinal ligament and the symphysis pubis?
What is the primary source of blood supply to the skin near the midline of the abdominal wall?
What is the primary source of blood supply to the skin near the midline of the abdominal wall?
Which of the following veins is responsible for draining the lower abdominal wall?
Which of the following veins is responsible for draining the lower abdominal wall?
What is the name of the deep membranous layer of the superficial fascia?
What is the name of the deep membranous layer of the superficial fascia?
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Which spinal nerve is responsible for supplying the area of skin over the xiphoid process?
Which spinal nerve is responsible for supplying the area of skin over the xiphoid process?
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What is the name of the fatty layer of the superficial fascia?
What is the name of the fatty layer of the superficial fascia?
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Which of the following arteries supplies the skin in the inguinal region?
Which of the following arteries supplies the skin in the inguinal region?
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Where does the venous drainage from the upper abdominal wall mainly pass?
Where does the venous drainage from the upper abdominal wall mainly pass?
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What is the main function of the dartos muscle in the scrotum?
What is the main function of the dartos muscle in the scrotum?
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Which of the following muscles is NOT part of the Anterior Abdominal Wall?
Which of the following muscles is NOT part of the Anterior Abdominal Wall?
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What is the insertion point of the External oblique muscle?
What is the insertion point of the External oblique muscle?
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What forms the anterior wall of the rectus sheath above the costal margin?
What forms the anterior wall of the rectus sheath above the costal margin?
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What is the function of the deep fascia in the perineum?
What is the function of the deep fascia in the perineum?
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What is the innervation of the External oblique muscle?
What is the innervation of the External oblique muscle?
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What forms the posterior wall of the rectus sheath above the costal margin?
What forms the posterior wall of the rectus sheath above the costal margin?
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At which level do the aponeuroses of all three muscles form the anterior wall of the rectus sheath?
At which level do the aponeuroses of all three muscles form the anterior wall of the rectus sheath?
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What is the primary function of the Rectus abdominis muscle?
What is the primary function of the Rectus abdominis muscle?
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What is the function of the aponeurosis?
What is the function of the aponeurosis?
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What is the name of the fascia that forms a tubular sheath for the penis (or clitoris)?
What is the name of the fascia that forms a tubular sheath for the penis (or clitoris)?
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What is the linea alba?
What is the linea alba?
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How many muscles are part of the Anterior Abdominal Wall?
How many muscles are part of the Anterior Abdominal Wall?
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What is the level at which the aponeurosis of the internal oblique splits to enclose the rectus muscle?
What is the level at which the aponeurosis of the internal oblique splits to enclose the rectus muscle?
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What is the posterior wall of the rectus sheath composed of between the level of the arcuate line and the pubis?
What is the posterior wall of the rectus sheath composed of between the level of the arcuate line and the pubis?
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What is a characteristic of aponeuroses?
What is a characteristic of aponeuroses?
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Which muscle has a posterior border that is free?
Which muscle has a posterior border that is free?
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What is the function of the conjoint tendon?
What is the function of the conjoint tendon?
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What is the origin of the Rectus abdominis muscle?
What is the origin of the Rectus abdominis muscle?
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What is the innervation of the Transversus abdominis muscle?
What is the innervation of the Transversus abdominis muscle?
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What is the function of the Internal oblique muscle?
What is the function of the Internal oblique muscle?
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What is the attachment site of the conjoint tendon medially?
What is the attachment site of the conjoint tendon medially?
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What is the name of the curved ridge formed by the rectus abdominis muscle when it contracts?
What is the name of the curved ridge formed by the rectus abdominis muscle when it contracts?
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What is the level of the second transverse tendinous intersection of the rectus abdominis muscle?
What is the level of the second transverse tendinous intersection of the rectus abdominis muscle?
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What type of fascia lines the transversus abdominis muscle?
What type of fascia lines the transversus abdominis muscle?
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What type of membrane lines the walls of the abdomen?
What type of membrane lines the walls of the abdomen?
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Which artery anastomoses with the inferior epigastric artery?
Which artery anastomoses with the inferior epigastric artery?
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What drains into the femoral vein via the superficial epigastric and great saphenous veins?
What drains into the femoral vein via the superficial epigastric and great saphenous veins?
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What type of fat is found between the fascia transversalis and the parietal peritoneum?
What type of fat is found between the fascia transversalis and the parietal peritoneum?
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Which artery arises from the external iliac artery?
Which artery arises from the external iliac artery?
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What forms an important portal-systemic venous anastomosis?
What forms an important portal-systemic venous anastomosis?
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Which artery supplies the lateral part of the abdominal wall?
Which artery supplies the lateral part of the abdominal wall?
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Study Notes
Dermatomes of the Anterolateral Abdominal Wall
- A dermatome is an area of skin supplied mainly by afferent nerve fibers from the dorsal root of a spinal nerve.
- The anterolateral abdominal wall is divided into dermatomes:
- T7: Over the xiphoid process
- T10: Umbilicus
- L1: Lies just above the inguinal ligament and the symphysis pubis
Skin Blood Supply and Venous Drainage
- The skin near the midline is supplied by branches of the superior and inferior epigastric arteries.
- The skin of the flanks is supplied by branches of the intercostal, lumbar, and deep circumflex iliac arteries.
- The skin in the inguinal region is supplied by the superficial epigastric, superficial circumflex iliac, and superficial external pudendal arteries, which are branches of the femoral artery.
- Venous drainage from the upper abdominal wall passes mainly into the axillary vein via the lateral thoracic vein.
- The lower abdominal wall drains into the femoral vein via the superficial epigastric and great saphenous veins.
Superficial Fascia
- Divided into two layers:
- Superficial fatty layer (Camper's fascia)
- Deep membranous layer (Scarpa's fascia)
- The superficial fatty layer is continuous with the superficial fat over the body, and may be extremely thick (8 cm or more) in obese individuals.
- The deep membranous layer is thin and fades out laterally and superiorly, where it becomes continuous with the superficial fascia of the back and thorax, respectively.
Deep Fascia
- A thin layer of connective tissue covering the muscles.
- Lies immediately deep to the membranous layer of superficial fascia.
Muscles of the Anterior Abdominal Wall
- Three broad thin sheets of muscle:
- External oblique
- Internal oblique
- Transversus abdominis
- Additionally, there are two muscles:
- Rectus abdominis (on either side of the midline anteriorly)
- Pyramidalis (may be present in the lower part of the rectus sheath)
External Oblique Muscle
- Origin: lower eight ribs
- Insertion: xiphoid process, linea alba, iliac crest, pubic crest, and tubercle
- Action: support and compress abdominal contents, assist in flexion and rotation of the trunk, assist in forced expiration, micturition, defecation, and vomiting
- Innervation: lower six thoracic nerves, iliohypogastric and ilioinguinal nerves (L1)
Internal Oblique Muscle
- Origin: iliac crest and lateral 2/3 of inguinal ligament
- Insertion: lower three ribs, xiphoid process, linea alba, and symphysis pubis
- Action: same as external oblique
- Innervation: same as external oblique
Transversus Abdominis Muscle
- Origin: lower six costal cartilages, iliac crest, and lateral 2/3 of inguinal ligament
- Insertion: xiphoid process, linea alba, and symphysis pubis
- Action: compress abdominal contents
- Innervation: same as external oblique
Conjoint Tendon
- Formed by the lowest tendinous fibers (aponeurosis) of the internal oblique and transversus abdominis muscles
- Attaches medially to the linea alba, with a lateral free border
- Has an essential role in protecting a weak area in the abdominal wall, where a weakening of the conjoint tendon may lead to a direct inguinal hernia
Rectus Abdominis Muscle
- Origin: symphysis pubis and pubic crest
- Insertion: 5th, 6th, and 7th costal cartilages, and xiphoid process
- Action: compress, flex vertebral column, and act as an accessory muscle of expiration
- Innervation: lower six thoracic nerves
Rectus Sheath
- The composition of the walls of the rectus sheath changes at different levels
- The anterior wall is formed by the aponeurosis of the external oblique above the costal margin
- The posterior wall is formed by the thoracic wall above the costal margin
- Between the costal margin and the arcuate line, the aponeurosis of the internal oblique splits to enclose the rectus muscle
- Below the arcuate line, the aponeuroses of all three muscles (external oblique, internal oblique, and transversus abdominis) form the anterior wall, and the posterior wall is absent
Linea Alba
- A fibrous band that separates the two rectus sheaths from each other
- Extends from the xiphoid process to the symphysis pubis
- Formed by the fusion of the aponeuroses of the lateral muscles of the two sides
Transversalis Fascia
- A thin layer of fascia that lines the transversus abdominis muscle
- Named according to the structure it overlies (e.g., diaphragmatic fascia, psoas fascia, iliac fascia)
Extra-peritoneal Fat
- A thin layer of connective tissue that contains a variable amount of fat
- Lies between the fascia transversalis and the parietal peritoneum
Parietal Peritoneum
- A thin serous membrane
- Lines the walls of the abdomen
- Continuous below with the parietal peritoneum lining the pelvis
Anterolateral Abdominal Wall Arteries
- Superior epigastric artery (from internal thoracic artery)
- Inferior epigastric artery (from external iliac artery, from common iliac artery)
- Deep circumflex iliac artery (from external iliac artery)
- Lower two posterior intercostal arteries (from descending thoracic aorta)
- Four lumbar arteries (from abdominal aorta)
Anterolateral Abdominal Wall Veins
- Superficial veins network radiates out from the umbilicus
- Above the umbilicus: drains into the axillary vein via the lateral thoracic vein
- Below the umbilicus: drains into the femoral vein via the superficial epigastric and great saphenous veins
- Paraumbilical veins form an important portal-systemic venous anastomosis
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Description
Understand the dermatomes of the anterolateral abdominal wall, including the areas supplied by spinal nerves T7, T10, and L1. Learn about the cutaneous nerve supply to the anterior abdominal wall.
