anterior abdominal wall Flashcards
What is the abdomen?
The abdomen is the part of the trunk between the thorax and pelvis.
How are the thoracic and abdominal cavities separated?
They are separated physically by the diaphragm.
Are the abdominal and pelvic cavities separate?
No, they are continuous with each other.
What is the boundary between the abdominal and pelvic cavities called?
The pelvic inlet, which is an imaginary plane.
What is the structure of the abdominal cavity anterolaterally?
It is musculo-aponeurotic.
What functions does the musculo-aponeurotic structure provide?
Protection, flexibility, and distensibility required for respiration, posture, and locomotion.
Why is the distensibility of the abdominal cavity important?
It accommodates expansions caused by ingestion, pregnancy, and other factors.
Up to which intercostal space can the abdominal cavity extend superiorly?
Up to the 4th intercostal space.
Which organs are protected by the thoracic cage?
The more superiorly located abdominal organs.
How is the abdominal cavity subdivided?
It is subdivided into nine regions to describe the location of organs, pain, or pathologies
What are the four planes used to delineate the nine abdominal regions?
- Two vertical midclavicular lines.
- One superior horizontal subcostal plane.
- One inferior horizontal transtubercular plane.
Where do the midclavicular lines pass?
From the midpoint of the clavicles to the midinguinal points.
Where does the subcostal plane pass?
Through the inferior border of the 10th costal cartilage on each side.
Where does the transtubercular plane pass?
Through the iliac tubercles and the body of the L5 vertebra.
What are the nine abdominal regions?
What additional landmarks do clinicians use to establish the abdominal regions?
- Two vertical semilunar lines.
- One superior horizontal transpyloric plane.
- One inferior horizontal interspinous plane.
Where do the semilunar lines run?
Parallel to the lateral edges of the rectus sheath.
Where is the transpyloric plane located?
Roughly midway between the superior margin of the manubrium and the pubic symphysis, at the L1 vertebral level.
What does the transpyloric plane transect when the patient is lying down?
The pylorus of the stomach.
Where does the interspinous plane pass?
Through the anterior superior iliac spines.
How is the abdominal cavity divided for general descriptions?
Into four quadrants.
What planes are used to divide the abdomen into quadrants?
The horizontal transumbilical plane.
The vertical median plane.
Where does the transumbilical plane pass?
Through the umbilicus, typically at the L3/L4 intervertebral disc.
Where does the median plane pass?
Longitudinally through the body.
What are the four quadrants of the abdomen?
What is the linea alba?
A vertical skin groove visible in lean individuals, separating the two columns of rectus abdominis.
Where does the inguinal ligament extend?
Between the anterior superior iliac spine and the pubic tubercle.
What are semilunar lines?
Slightly curved linear impressions in the skin, parallel to the lateral edges of the rectus sheath.
whats present in both male and females for the Surface anatomy of anterolateral abdominal wall
epigastric fossa
semilunar valves
umbilicus
linguinal ligament
How is the subcutaneous tissue superior to the umbilicus characterized?
It is consistent with subcutaneous tissue found in most regions of the body.
How is the subcutaneous tissue inferior to the umbilicus reinforced?
By many elastic and collagen fibers, forming two distinct layers:
- The superficial fatty (Camper’s) layer.
- The deep membranous (Scarpa’s) layer.
What are the two distinct layers of the superficial fascia of the abdomen?
- Camper’s (fatty) layer.
- Scarpa’s (membranous) layer.
What key muscles and structures are visible in the superficial anatomy of the anterolateral abdominal wall?
What muscle is responsible for the “six (or eight) packs” appearance?
The rectus abdominis, divided by tendinous junctions.
What structures are included in the intermediate layer of the anterolateral abdominal wall?
What is the function of the tendinous junctions?
They divide the rectus abdominis into segments, contributing to the “pack” appearance.
What structures are included in the deep layer of the anterolateral abdominal wall?
what are the layers of the anterolateral abdominal wall from superficial to deep
What is the origin of the external oblique muscle?
The external surfaces of the 5th-12th ribs.
What are the 3 insertion points of the external oblique muscle?
Linea alba.
Anterior half of the iliac crest.
Pubic tubercle.
What are the 2 actions of the external oblique muscle?
Unilateral: Lateral flexion of the trunk to the same side and rotation of the trunk to the opposite side.
Bilateral: Flexion of the trunk, stabilization of the pelvis, compression of the abdomen, and assistance in expiration.
What is the 3 innervations of the external oblique muscle?
- Intercostal nerves (T5-T11).
- Subcostal nerve (T12).
- Iliohypogastric nerve (L1).
What structure is formed by the inferior margin of the external oblique aponeurosis?
The inguinal ligament, which runs from the anterior superior iliac spine (ASIS) to the pubic tubercle.
What is the origin of the internal oblique muscle?
- Thoracolumbar fascia.
- Anterior two-thirds of the iliac crest.
What are the 2 insertion points of the internal oblique muscle?
- Inferior borders of the 10th-12th ribs.
- Linea alba.
What are the 2 actions of the internal oblique muscle?
Unilateral: Lateral flexion and rotation of the trunk to the same side.
Bilateral: Flexion of the trunk, stabilization of the pelvis, compression of the abdomen, and assistance in expiration.
What are the 4 innervations of the internal oblique muscle?
- Intercostal nerves (T6-T11).
- Subcostal nerve (T12).
- Iliohypogastric nerve (L1).
- Ilioinguinal nerve (L1).
what part of the abdomen does this diagram highlight
external oblique
what part of the abdomen does this diagram highlight
internal oblique
what part of the abdomen does this diagram highlight
transverse abdominis
What is the thoracolumbar fascia?
A strong connective tissue structure in the lumbar region, with anterior, middle, and posterior layers enclosing muscles.
How many layers does the thoracolumbar fascia have, and what are they?
3
Anterior layer.
Middle layer.
Posterior layer.
What is the origin of the rectus abdominis?
Pubic symphysis.
Pubic crest.
What are the 2 insertion points of the rectus abdominis?
Xiphoid process.
5th-7th costal cartilages.
What are the 4 actions of the rectus abdominis?
Flexion of the lumbar spine.
Stabilization of the pelvis.
Compression of the abdomen.
Assistance in expiration.
What are the 2 innervations of the rectus abdominis?
Intercostal nerves (T5-T11).
Subcostal nerve (T12).
What is the origin of the pyramidalis muscle?
Pubic crest.
Where does the pyramidalis insert?
Linea alba.
What is the action of the pyramidalis muscle?
Tenses the linea alba.
What is the innervation of the pyramidalis muscle?
Subcostal nerve (T12).
What percentage of people lack the pyramidalis muscle
It is absent in approximately 20% of people.
Which 4 muscles are involved in the movements of the anterolateral abdominal wall?
How do the contralateral external and internal oblique muscles work together?
They act as a unit to perform flexion and rotation. For example, the right external oblique (EO) and left internal oblique (IO) work together to bring the right shoulder toward the left hip.
How do the fibers of the external and internal obliques differ in orientation?
External oblique fibers: Pass diagonally downward and medially.
Internal oblique fibers: Pass diagonally upward and medially.
Which muscles are involved in lateral flexion of the trunk?
External oblique.
Internal oblique.
Which muscles are primarily responsible for trunk flexion (bending forward)
Rectus abdominis.
What is the rectus sheath?
An incomplete fibrous sheath that encloses the rectus abdominis and pyramidalis muscles.
What 3 structures are enclosed by the rectus sheath besides muscles?
- Superior and inferior epigastric arteries and veins.
- Lymphatic vessels.
- Distal portions of the anterior rami of spinal nerves T7-T12.
How is the rectus sheath formed?
By the decussation and interweaving of the aponeuroses of the three layers of abdominal muscles:
External oblique (EO).
Internal oblique (IO).
Transversus abdominis (TA).
What are the 2 layers of the rectus sheath?
Anterior layer: Covers the front of the rectus abdominis.
Posterior layer: Covers the back of the rectus abdominis.
What is the linea alba?
A fibrous midline structure formed by the interweaving fibers of the rectus sheath.
What is the arcuate line?
It marks the transition between the aponeurotic posterior wall of the rectus sheath (covering the superior 3/4 of the rectus abdominis) and the transversalis fascia (covering the inferior 1/4).
What structures cover the superior 3/4 of the rectus abdominis above the arcuate line?
The aponeurotic posterior wall of the rectus sheath.
What covers the inferior 1/4 of the rectus abdominis below the arcuate line?
The transversalis fascia.
Where is the arcuate line located?
Roughly 1/3 of the distance from the umbilicus to the pubic crest.
How is the rectus sheath formed above the arcuate line?
What forms the posterior layer of the rectus sheath above the arcuate line?
The posterior layer is formed by the aponeurosis of the internal oblique (IO) and transversus abdominis (TA).
How is the rectus sheath formed below the arcuate line?
The aponeuroses of all three abdominal muscles (EO, IO, and TA) pass anterior to the rectus abdominis to form the anterior layer of the rectus sheath.
What covers the posterior aspect of the rectus abdominis below the arcuate line?
The transversalis fascia.
What is the dermatomal landmark for the umbilicus?
T10 dermatome.
What are the T7-T12 thoracoabdominal nerves?
Distal anterior rami of the T7-T12 spinal nerves.
Former intercostal nerves distal to the costal margin.
Where do the T7-T12 thoracoabdominal nerves run?
In the neurovascular plane between the internal oblique and transversus abdominis muscles.
What do the T7-T12 thoracoabdominal nerves supply?
The skin and muscles of the anterolateral abdominal wall.
What 3 nerves contribute to innervation of the anterolateral abdominal wall?
Subcostal nerve (T12).
Iliohypogastric nerve (L1).
Ilioinguinal nerve (L1).
What branches do the thoracoabdominal nerves give rise to?
- Anterior cutaneous branches.
- Lateral cutaneous branches.
Where is the T12 (subcostal) nerve located?
Below the 12th rib, providing lateral and anterior cutaneous branches.
What are the 2 main arteries supplying the anterolateral abdominal wall?
Superior epigastric artery
Inferior epigastric artery
What does the external iliac artery continue as?
The femoral artery at the point of the inguinal ligament.
Which arteries supply the lateral region of the abdominal wall?
10th and 11th posterior intercostal arteries.
Subcostal artery from the descending aorta.
What is the relationship between the superior and inferior epigastric arteries?
They anastomose within the rectus sheath, ensuring continuous blood supply to the abdominal wall.
Where does the superior epigastric artery arise from?
From the internal thoracic artery.
Where does the inferior epigastric artery arise from?
From the external iliac artery.
label this diagram of the vessels of anterolateral abdominal wall
