Anterior Abdominal Wall Flashcards
Name the bony landmarks of the anterior abdominal wall
- Xiphoid process
- Costal margin (7th to 10th)
- Iliac crest
- ASIS
- Pubic crest and tubercle
6.Pubic symphysis
Name the surface landmarks of the AAW.
- Umbilicus
- Linea alba- extends from xiphoid process to pubic symphysis
- Costal margin- superiorly
- Iliac crest
- ASIS
- Inguinal ligament/line
- Pubic tubercle and crest
What are the structures forming the AAW?
- Skin
- Superficial fascia- outer fatty layer(camper’s fascia) and inner membranous (scarpa’s fascia)
- Muscles- EO, IO, TA
- Blood vessels
- Nerves
- Lymphatics
No deep fascia to allow free movement of abdominal organ
Scarpa’s fascu
Discuss the superficial fascia.
- Contains two layers below the line formed by joining the two ASIS.
- Superficial fatty layer( Camper’s) and deep membranous layer(Scarpa’s)
- The space between the two layer contains superficial epigastric, circumflex iliac, external pudendal vessels, and superficial inguinal lymph nodes.
- Camper’s fascia- continous with the superficial fascia of adjoining areas of the body. Over the penis, it is devoid of fat and in the scrotum it is replaced by an involuntary muscle, dartos muscle.
- Scarpa’s fascia:
- In the midline it is attached to linea alba
- Separated from underlying EO muscle by a layer of loose areolar tissue.
- Forms fascia of the penis- Buck’s fascia
- Covers scrotum where it is replaced by dartos and then continues with the superficial fascia of perineum- Colles’ fascia.
-The space between the perineal membrane and Colles’ fascia is called superficial perineal pouch
Discuss the anterior abdominal wall muscles.
1. External Oblique- down & medially
* Origin- lower 8 ribs.
* Insertion:
1. Fleshy fibers- iliac crest
2. Aponeurosis- upper part to xiphoid process and gives origin to pec major, middle part to linea alba and the lower part forms inguinal ligament.
2. Internal Oblique-
* Origin- lateral 2/3 of inguinal ligament, iliac crest(middle), lumbar fascia.
* Insertion- fleshy fibers to the 3 last ribs, aponeurosis inserted to next 3 costal cartilages, xiphoid process and linea alba, pubic crest & pectineal line.
* At the lateral border of rectus muscle, it splits into two layers
* Lower part fuses with transversus abdominis to form conjoint tendon.
* Lower border of aponeurosis fuses with that of transversus abdominis to form arcuate line.
3. Transversus abdominis- horizontal
* Origin: lateral 1/3 of inguinal ligament, iliac crest(inner lip), lumbar fascia and lower 6 costal cartilages.
* Insertion: xiphoid process & linea alba, pubic crest & pectineal line through the conjoint tendon.
* Forms posterior wall of rectus sheath
* Lined by trasnversalis fascia which forms iliopubic tract( over external iliac vessels) and deep inguinal ring.
* Forms arcuate line with IO.
Rectus abdominis
* Origin: Symphysis pubis(medial head) and pubic crest( lateral head).
* Insertion: 5,6,7 costal cartilages and xiphoid process.
* Linea semilunaris- lateral border
* Divided into 4 segments by 3 tendinous intersections.
Supplied by the lower 6 thoracic nerves T(7-T12)
Pyramidalis
* Small triangular muscle that may be absent.
* Origin:
* Insertion: linea alba
* Stretches the linea alba
Supplied by subcostal nerve (T12)
The 3 obliques are supplied by the lower 6 thoracic nerves and L1( iliohypogastric and ilioinguinal nerves)
State the functions of the anterior abdominal wall muscles.
- Oblique muscles- lateral flexion and roation of the trunk.
- Rectus abdominis- flexion of the trunk and stabilisation of the pelvis.
- Pyramidalis- stretches the linea alba.
- Accessory muscles of respiration: they relax during inspiration and assist in forced expiration(coughing and sneezing)
- Protect abdominal viscera and keep them in place.
- Raise intra-abdominal pressure during defecation, parturition and micturition.
Discuss the Rectus Sheath.
Contents:
1. Two muscles- RA and pyramidalis( if present)
2. Two arteries- superior and inferior epigastric.
3. Two veins- Superior and inferior epigastric.
4. Six nerves- terminal arts of lower 6 thoracic nerves, including lower 5 intercostal nerves and subcostal nerve.( they are accompanied by terminal parts of posterior intercostal vessels)
* Aponeurotic sheath enclosing rectus abdominis muscle.
* Derived from the aponeuroses of flat muscles of the anterior abdominal wall
* Maintains the strength of the anterior abdominal wall.
* Checks bowing of RA muscle during contraction hence increasing its efficiency.
* Has anterior(complete) and posterior(deficient above and below) walls.
* Posterior wall is attached to 7,8,9 costal cartilages above and presents free curved margin below.
Formation:
Above level of costal margin
1. Anterior wall is formed by aponeurosis of EO only.
2. Posterior wall is deficient and muscle lies directly on 5th,6th,7th costal cartilages.
Between costal margin and arcuate line
1. Anterior wall- fusion of EO with anterior lamina of IO.
2. Posterior wall- fusion of posterior lamina of IO and TA.
Below the arcuate line:
1. Anterior- aponeuroses of all 3 flat muscles.( TA and IO are fused, EO is separate)
2. Posterior- deficient.
Discuss the inguinal ligament.
Attachments
Lateral- ASIS
Medial- Pubic tubercle
Deep relations- acts as retinaculum
1. 3 muscles- pectineus, psoas and iliacus
2. 2 vessels- femoral vein and artery.
3. 2 fascia- transversalis and iliacus
4. 3 nerves- genitofemoral, femoral and lateral cutaneous nerve of thigh.
5. Lymphatics
Extensions/Expansions:
1. Lacunar ligament- lateral edge forms boundary for femoral canal.
2. Pectineal ligament (ligament of cooper)- extension of posterior part of lacunar along pecten pubis.
3. Reflected part of inguinal ligament
4. Ilioinguinal ligament.
List the layers of the AAW.
- Skin
- Superficial fascia
- Muscles- EO,IO,TA
- Transversalis fascia
- Extraperitoneal fat
- Parietal layer of peritoneum
Name the lines of the AAW.
- costal margin
- linea alba- tendinous line formed by decussating of aponeurosis of muscles.
- linea semilunaris- lateral border of RA
- inguinal ligament
- arcuate line- lower border of IO and TA aponeurosis
- Mc burney’s incision
- langer’s lines- cleavage lines formed by direction of collagen fibres in the dermis.
Incision parallel to langer’s line leaves minimal scars
Mc Burney’s point- surface landmark for vermiform appendix, medial 2/3 and lateral 1/3 on line between umbilicus and ASIS(spino-umbilical line)
9 arteries ; 3 superficial, 6 deep
Describe the blood supply of the AAW.
Superficial
1. Superficial external pudendal- to external genitalia
2. Superficial epigastric- going to the umbilicus
3. Superficial circumflex iliac- to iliac crest
Deep
Above- from internal thoracic
1. Superior epigastric- enters rectus sheath
2. Musculophrenic- runs along costal margin
Side- from aorta
1. Posterior intercostal arteries
2. Lumbar arteries
Below- branches of external iliac
1. Inferior epigastric- enters rectus sheath, lies medial to deep inguinal ring.
2. Deep circumflex iliac- going to iliac crest
The superior and inferior epigastric anastomose, connecting the sub clavian artery with the external iliac.
All superficial arteries are branches of femoral artery
Internal thoracic is from subclavian
Discuss the inferior epigastric artery.
- From external iliac
- Enters rectus sheath
- Medial to deep inguinal ring.
- Has 2 branches:
1. Pubic branch- anastomoses with pubic branch of obturator . It may enlarge and replace the obturator artery and is called abnormal obturator artery.
2. Cremastric artery- passes through deep inguinal ring to supply cremaster muscle.
The pubic branch is related to the femoral ring and may be injured in femoral hernia operation.
Describe the venous drainage of the anterior abdominal wall.
Superficial veins:- drain in 3 directions
* Superiorly- lateral thoracic vein to axillary vein.
* Inferiorly- superficial epigastric to great saphenous to femoral vein.
* Medially- paraumbilical veins to portal vein
Caput medusae- dilated veins radiating from umbilicus due to liver cirrhosis portal hypertension
Deep Veins
* Superior epigastric and musculophrenic veins- drain into internal thoracic vein.
* Inferior epigastric and deep circumflex iliac veins- drain into external iliac vein.
* Posterior intercostal veins- drain into azygos vein.
* Lumbar veins- drain into *Inferior vena cava.
*
The superior epigastric and lateral thoracic form an anastomotic channel called thoracoepigastric vein. It connect axillary vein and femoral vein.
Thoracoepigastric vein dilates in superior vena cava obstruction.
Discuss the nerve supply to the skin and muscles of the anterior abdominal wall.
- Lower six thoracic nerves (T7-T12)
- Iliohypogastric nerve- (anterior primary ramus ofL1)
- Ilioinguinal nerve- (anterior primary ramus of L1)
*
Cutaneous nerves - Lower six thoracic nerves (T7-T12) through intercostal and subcostal nerves.
- Only the inferior part is supplied by the first lumbar nerve through the iliohypogastric and ilioinguinal nerves.
Anterior cutaneous
-Derived from the lower 5 intercostal, subcostal and iliohypogastric nerves
- They pierce anterior wall of rectus sheath and divide into medial and lateral branches to supply the skin.
Lateral cutaneous branches
1. From lower two intercostal nerves, emerge through the external intercostal muscle and divide into a large anterior and small posterior branches to supply skin.
2. Lateral cutaneous branches of subcostal and iliohypogastric nerves appear close to the iliac crest and descend over it to supply the skin in the upper anterior part of the gluteal region.
The lower 5 intercostal nerves leave the intercostal spaces between the slips of origin of the TA muscle and diaphragm and enter the abdominal wall by passing behind the 7,8,9,10 costal cartilages. They pierce post wall of rectus sheath, RA and ant wall and come out as the anterior cutaneous nerves.
Identify the dermatomes of the anterior abdominal wall.
- Level of xiphoid process- T7
- Umbilicus- T10
- Suprapubic region- L1
The visceral pain of appendicitis is referred to the umbilicus as the appendix is supplied by T10 spinal segment.
