Abdominal wall anatomy

Question 1

What divides the abdomen into quadrants?

Answer 1

Vertical and transverse lines through the umbilicus

Question 2

What are the two vertical lines used to define the abdominal regions?

Answer 2

Midclavicular lines

Question 3

What is the mid-inguinal point?

Answer 3

Midway between the pubic symphysis and the anterior superior iliac spine (ASIS)

Question 4

What are the two horizontal lines that define abdominal regions?

Answer 4

Transpyloric plane and intertubercular plane

Question 5

Where is the transpyloric plane located?

Answer 5

Midway between the jugular notch and the top of the pubic symphysis

Question 6

Where is the intertubercular plane located?

Answer 6

Between the tubercles of the iliac crest

Question 7

List the central regions of the abdomen from top to bottom.

Answer 7

• Epigastric
• Umbilical
• Hypogastric/suprapubic

Question 8

List the side regions of the abdomen from top to bottom.

Answer 8

• Hypochondral
• Lumbar/flank
• Iliac/groin

Question 9

What three muscle layers make up the anterolateral abdominal wall?

Answer 9

• External Oblique (EO)
• Internal Oblique (IO)
• Transversus Abdominis (TA)

Question 10

What muscle is formed when the layers of the abdominal muscles fuse together anteriorly?

Answer 10

Rectus abdominis muscle

Question 11

External oblique origin

Answer 11

Lower 8 ribs

Upper 4 - Interdigitate with serratus anterior

Lower 4 - nterdigitate with lat dorsi

Question 12

External oblique insertion

Answer 12

Anterior 1/2 of iliac crest

Aponeurosis extending from ASIS to pubic tubercle (inferiorly) + linea alba + Xiphisternum

Interdigite with contralateral aponeurosis

Question 13

What are the borders and free edge of external oblique?

Answer 13

Posterior

Free muscular edge

Forms ant boarder of lumbar triange (of Petit)

Upper

Free

5th Rib to xiphisternum

Lower

ASIS → pubic tubercle

Forms inguinal ligament

Its edge is rolled inwards to form a gutter

Laterally - gives rise to IO + TA; also attachment of fascia lata of the thigh

Medially - superficial inguinal ring = V-shaped gap in aponeurosis just above and lateral to pubic tubercle → extends down to pubic crest

Intercrural fibers - fibres running 90º to aponeurosis near apex of superficial inguinal ring. Prevent crua from seperating

Question 14

What is the origin of internal oblique

Answer 14

Lumber fascia (whole length)

Anterior 2/3 of iliac crest

Lateral 2/3 of inguinal ligament

Question 15

What is the insertion of internal oblique

Answer 15

Costal margins (aponeurtoic at tip 9th rib)

Linea alba

Above arcuate line* – Aponeurosis splits around rectus abdominis

Below arcuate line – Aponeurosis anterior to rectus abdominis

↘︎Crest of pubic bone

↘︎Pectineal line

fuse with fibers of transversus aponeurosis to form the Conjoint Tendon

Question 16

What are the borders/free edge of internal oblique?

Answer 16

Lower border

Is free and arches over the spermatic cord

Laterally muscle fibres in front of the cord

Medially - tendious fibres behind the cord

Arcute line (or semicircular line of douglas)

Free lower margin of posterior layer of the rectus sheath

Found 2.5cm below umblicus

Question 17

What is the origin of transversus abdominus

Answer 17

Costal margin (whole thing, from inside of each costal cartilage, interdigitating with costal orgin of diaphragm)

Lumber fascia (lateral to quadraus lumborum

Anterior 2/3 of iliac crest

Lateral 1/2 inguinal ligament

Fascia over iliac

Question 18

What is the insertion of transversus abdominus

Answer 18

Linea alba

above arcuate line  behind rectus abdominis

Below arcuate line  anterior to rectus abdominis

↘︎Crest of pubic bone

↘︎Pectineal line

fuse with fibers of Internal Oblique to form the Conjoint Tendon

Question 19

What is the origin of rectus abdominus?

Answer 19

3 Tendinous
intersections
(rarely 4)
Fusion to
anterior sheath

Two heads

pubic symphysis (medial)

Pubic crest (lateral)

T he two muscles lie edge to edge in lower part  separated by linea alba in upper part

Question 20

What is the insertion of rectus abdominus?

Answer 20

5th - 7th costal cartilages I’ll

Costal margin

Xiphisternal fibres to diaphragm

Diaphragm
xiphoid

3 (occ 4) x ‘tendinous insertions’ which blend with anterior layer of rectus sheath  they are at: (1) Umbilicus, (2) Xiphisternum, and (3) Halfway b/w these two

A.k.a. the abs

Question 21

Where is pyrimidalis found

Answer 21

Pyramidalis – Pubic crest (b/w rectus abdominis and its sheath)  linea alba (4cm above origin)

Question 22

Describe the linea alba

Answer 22

Strong, midline, fibrous structure  Lies b/w the two recti abdomini

Formed by fusion of all the aponeuroses

Pubic symphysis to Xiphoid process NB// Becomes thicker as it advances superiorly

Question 23

Describethe semilunar line

Answer 23

Lateral border of rectus muscle, is formed by splitting of IO aponeurosis

NB// Curves up from pubic tubercle to costal margin (tip of 9th costal cartilage in transpyloric plane)

Question 24

Describe the arcuate line

Answer 24

= Free lower margin to the posterior layer of the rectus sheath  found 2.5cm below umbilicus

Above arcuate line:

Internal oblique aponeurosis splits around rectus muscle (anterior and posterior)

External oblique aponeurosis fuses with anterior layer of internal oblique aponeurosis to form anterior layer of rectus sheath

Transversus aponeurosis fuses w/ posterior layer of internal oblique aponeurosis to form posterior layer of rectus sheath

Below arcuate line:

All 3 aponeuroses pass in front of muscle

Below the umbilicus, the aponeuroses of IO and TA fuse completely  but that of EO fuses only to the most medial part of the sheath

NB// Posterior layer is attached to the costal margin (7-9th costal cartilage)  Rectus muscle passes over this costal margin to become attached to 5-7th costal cartilage (as does the EO aponeurosis)  so in this region the anterior layer of the sheath only consists of EO

Question 25

What are the contents of the rectus sheath?

Answer 25

Muscles, nerves, vessels. Muscles : Rectus abdominis Pyramidalis muscles Vessels Superior Epigastric artery and vein Inferior Epigastric artery and vein Nerves Anterior cutanous branches of the lower thoracic nerves (T7-12) + accompanying posterior intercostal vessels Posterior intercostal nerves → pass from IC space into the abdo wall. Run in neurovascular plane - b/w IO and TA Enter rectus sheath by piercing post layer of IO aponeurosis Pass to the midline of rectus muscle Pierce the muscle and supply it Skin is supplied by Poster intercostal nerves that then pierce ant layer of sheath to to become ant cutanous nerves, supply skin Before these nerves reach the sheath, they give off their ‘lateral cutaneous branches’  pierces IO and EO (supplies EO)  reaches the skin  

Question 26

Describe the arterial origin, venous drainage, and course of the superior epigastric artery and vein

Answer 26

Superior Epigastric artery and vein Terminal branch of internal thoracic Enters sheath by passing between sternal and costal fibers of diaphragm Supplies rectus muscle and anastomoses with inferior epigastric a. Accompanying vein→ drains in to internal thoracic vien

Question 27

List the four (groups of) vessels contributing to the blood supply of the anterior abdominal wall

Answer 27

Superior epigastric artery and vein Inferior epigastric artery and vein Thoracic vessels and Lumbar arteries Deep circumflex iliac artery

Question 28

Describe the origin, venous drainage, and course of the inferior epigastric artery and vein

Answer 28

The inferior epigastric artery branches off the external iliac at the inguinal ligament  Passes upwards behind the conjoint tendon, and Slips over arcuate line and enters the sheath Accompanying vein → drains into external iliac vein

Question 29

Describe the origin of and course of the deep circumflex iliac artery

Answer 29

The deep circumflex artery rises from external iliac behind inguinal ligament. It runs laterally towards ASIS and continues along inner lip of iliac crest where pierces transversus muscle to reach the neurovascular plane where it will anastomose with branches of iliolumbar and superior gluteal arteries At ASIS, it gives off an ascending branch that enters neurovascular plane and anastomoses with inferior epigastric and lumbar arteries

Question 30

Are there lymph nodes in the abdominal wall?

Answer 30

No

Question 31

Describe the superficial lymphatic drainage of the abdominal wall

Answer 31

Superficial tissues of the wall Above umbilicus drains to the pectoral group of axillary nodes Below umbilicus drains to the superficial inguinal nodes

Question 32

Describe the lymphatic drainage of the deeper tissues of the abdominal wall

Answer 32

Above umbilicus drains to the mediastinal nodes Below umbilicus drains to the external iliac and para-aortic nodes

Question 33

List the nerve supply to the abdominal wall components

Answer 33

Rectus abdominis – Lower intercostal and subcostal nerves (T7-12) Pyramidalis – Subcostal nerve (T12) EO – Lower intercostal and subcostal nerves (T7-12) IO and TA – Lower intercostal and subcostal (T7-12), iliohypogastric and ilioinguinal (L1) nerves

Question 34

What are the four actions of the abdominal wall?

Answer 34

Abdo wall conforms to volume of abdo contents  shape is determined by the tonus of its own muscles. Actions: Moving the trunk [e.g. one armed movements] – Flexion of lower thoracic and lumbar spine (rectus most powerful), abduction and rotation of trunk (obliques) Depressing the ribs [expiration] – Recti and oblique’s approximate the ribs to the pelvic girdle  erector spinae prevents thoracolumbar flexion Compressing the abdomen [expiration, evacuation, heavy lifting] – Obliques and TA  erector spinae prevents thoracolumbar flexion NB// Expiration – Diaphragm relaxed, pelvic effluent closed; Evacuation – Diaphragm contracts (+ breath hold), pelvic effluent opened Supporting and protecting viscera – Esp the intestines  reflex contraction in response to a blow