Anatomy of Abdominal Muscles

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Questions and Answers

What is the primary function of the psoas minor muscle?

Strong flexion of the trunk

Extension of the lumbar spine

Weak flexion of the trunk (correct)

Rotation of the pelvis

At which vertebral level does the abdominal aorta bifurcate into the common iliac arteries?

L4 (correct)

Which branch of the abdominal aorta arises at the level of the L2 vertebrae?

Celiac trunk

Superior mesenteric artery

Renal artery

Inferior mesenteric artery (correct)

Which artery supplies the second half of the large intestine?

Inferior mesenteric artery Signup and view all the answers

Which of the following arteries is not a branch of the celiac trunk?

Superior mesenteric artery Signup and view all the answers

Which nerve root innervates the psoas minor muscle?

L1 anterior ramus Signup and view all the answers

Which artery supplies the kidneys?

Renal artery Signup and view all the answers

What is the level of the vertebral column where the abdominal aorta enters the abdominal cavity?

T12 Signup and view all the answers

What is the origin of the internal oblique muscle?

Iliac crest and lateral 2/3 of inguinal ligament Signup and view all the answers

What is the action of the transversus abdominis muscle?

Compression of abdominal contents Signup and view all the answers

What is the purpose of the conjoint tendon?

To protect a weak area in the abdominal wall Signup and view all the answers

What is the insertion of the rectus abdominis muscle?

5th, 6th, and 7th costal cartilages and xiphoid process Signup and view all the answers

What is the innervation of the internal oblique muscle?

As previous Signup and view all the answers

What is the characteristic of the posterior border of the external oblique muscle?

Free Signup and view all the answers

What is the significance of the linea semilunaris?

It is a curved ridge formed by the rectus abdominis muscle Signup and view all the answers

What is the purpose of the tendinous intersections of the rectus abdominis muscle?

To divide the muscle into distinct segments Signup and view all the answers

What type of muscle is the dartos muscle?

Smooth muscle Signup and view all the answers

What is the main function of the external oblique muscle?

To support and compress abdominal contents Signup and view all the answers

What is the insertion point of the external oblique muscle?

Linea alba, xiphoid process, iliac crest, pubic crest, and tubercle Signup and view all the answers

Which nerve innervates the external oblique muscle?

Iliohypogastric and ilioinguinal nerves (L1) Signup and view all the answers

What is the deepest layer of fascia in the scrotum?

Deep fascia Signup and view all the answers

What is the function of the deep fascia?

To cover and protect the muscles Signup and view all the answers

Which muscle is located on either side of the midline anteriorly?

Rectus abdominis Signup and view all the answers

What is the function of Colles' fascia?

To form a tubular sheath for the penis Signup and view all the answers

What forms the posterior wall of the rectus sheath above the costal margin?

Thoracic wall Signup and view all the answers

Which of the following muscles forms the anterior wall of the rectus sheath between the level of the arcuate line and the pubis?

All three muscles (external oblique, internal oblique, and transversus) Signup and view all the answers

What is the purpose of an aponeurosis?

To connect muscles to bones Signup and view all the answers

What is the function of the linea alba?

To separate the two rectus sheath from each other Signup and view all the answers

What is the transversalis fascia?

A thin layer of connective tissue that lies behind the rectus muscle Signup and view all the answers

What is the level of the arcuate line in relation to the anterior superior iliac spine?

At the level of the anterior superior iliac spine Signup and view all the answers

What is the function of the aponeurosis of the external oblique above the costal margin?

To form the anterior wall of the rectus sheath Signup and view all the answers

What is the relationship between an aponeurosis and a tendon?

An aponeurosis is similar to a tendon Signup and view all the answers

Where do the gonadal arteries originate from?

Abdominal aorta at L2 vertebral level Signup and view all the answers

What is the purpose of the lumbar arteries?

Supply the heavy muscles of the abdomen and trunk walls Signup and view all the answers

What are the final branches of the abdominal aorta?

Common iliac arteries Signup and view all the answers

Where does the inferior vena cava form?

At L5 vertebral level Signup and view all the answers

What structures do the common iliac arteries supply?

Abdominal wall and pelvic organs Signup and view all the answers

What drains the structures of the posterior abdominal wall?

Inferior vena cava Signup and view all the answers

Where does the inferior vena cava enter the heart?

Right atrium Signup and view all the answers

What is the destination of the blood from the gut tube?

Portal system Signup and view all the answers

Study Notes

Muscles of the Anterior Abdominal Wall

The muscles of the anterior abdominal wall consist of three broad, thin sheets of muscle that are most pronounced laterally and become aponeurotic anteriorly.
The four main muscles are: external oblique, internal oblique, transversus abdominis, and rectus abdominis.

External Oblique

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 trunk, assist in forced expiration, micturition, defecation, and vomiting
Innervation: lower six thoracic nerves, iliohypogastric and ilioinguinal nerves (L1)

Internal Oblique

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

Origin: lower six costal cartilages, iliac crest, and lateral 2/3 of inguinal ligaments
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 internal oblique and transversus abdominis muscles
Attaches medially to the linea alba, but has 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

Origin: symphysis pubis and pubic crest
Insertion: 5th, 6th, and 7th costal cartilages and xiphoid process
Action: compress, flex vertebral column, and 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 rectus sheath is generally considered at three levels: above the costal margin, between the costal margin and the arcuate line, and between the level of the arcuate line and the pubis
The aponeuroses of the external oblique, internal oblique, and transversus abdominis muscles form the rectus sheath

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

Abdominal Aorta

Enters the abdomen through the aortic aperture of the diaphragm (T12)
Branches to the diaphragm (inferior phrenic), abdominal wall (lumbar, median sacral), abdominal viscera, kidneys, and ovaries/testes
Bifurcates at L4 into common iliac arteries to supply the lower limb and pelvis

Arterial Branches of Abdominal Aorta

Celiac trunk: the first branch of the abdominal aorta, supplying the stomach, spleen, and liver
Superior mesenteric artery: supplying most of the small intestine and the first half of the large intestine, or colon
Inferior mesenteric artery: a small, unpaired artery supplying the second half of the large intestine
Renal arteries: serving the kidneys
Gonadal arteries: serving the ovaries and testes
Lumbar arteries: serving the heavy muscles of the abdomen and trunk walls

Inferior Vena Cava

Forms at L5 vertebral level when the left and right common iliac veins unite
Drains the structures of the posterior abdominal wall, the kidneys, and the suprarenal glands
The veins that drain blood from the gut tube pass their blood into the portal system, not the IVC
Blood from the portal system passes through the liver before entering the IVC via hepatic veins
The IVC passes from the liver and through the diaphragm at T8 before entering the inferior surface of the right atrium

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Description

Learn about the muscles of the anterior abdominal wall, including the external oblique, internal oblique, transversus abdominis, and rectus abdominis.