Anterior Abdominal Wall and Inguinal Canal

Richard D. Lane, Ph.D.Professor and Acting ChairmanDepartment of Neurosciences

Room 103, Block HSBRlane@meduohio.edu

AnteriorAbdominalWall

PosteriorAbdominalWall

Anterior Abdominal WallA. Definitions:

Abdomen:The portion of the trunk between thethorax and pelvis

Abdominal cavity:The space enclosed by the

abdominal wall,Continuous with the pelvic cavity(abdominopelvic cavity)

Contains the abdominal viscera and peritoneal cavity

Anterior (anteriolateral) abdominal wall:Musculocutaneous sheet anchored

to the skeleton (ribs, lumbar vertebrae, pelvis)

Umbilicus

AnteriorSuperiorIliac Spine

LineaAlba

LineaSemilunaris

Umbilicus

ASIS

B. Physiology of the Anterior Abdominal Wall:

1. Bend and rotate trunk

2. Support trunk

3. Raise abdominal pressure (Valsalva Maneuver) Loud speech, vomiting, defecation, child birth

II. Clinical RelevancyA. Diagnostic

1. Palpate abdominal organs2. Rigidity and/or rebound tenderness indicate irritation of the deep surface

3. Enlarged - 5 Fs & 1 T: Fetus, fluid (ascites), fat (superficial or deep), flatus, feces, and tumor

B. Surgical1. Common site of entry into abdominal cavity2. Repair of inguinal hernia

4 Quadrants

Transumbilical plane (TUP)IV disc between L3 & L4

Median plane

RUQ LUQ

RLQ LLQ

9 RegionsMidclavicular line (MCL)

Subcostal plane (L2)

Transtubercular plane (L5)

E

U

H

RH

RL

RI

LH

LL

LI

V. Muscles of the Anterior Abdominal Wall

Innervation: Anterior rami of T7-T12 spinal nerves (Thoracoabdominal nerves) +/- L1

Combined action: Compress abdominal contents

Inferior ribs

Anterior ½ iliac crest

Pubic tubercle

Anterior superiorIliac spine

Inguinal ligament

Rectus Sheath

Superficial Inguinal ring

Anterior 2/3Iliac crest

Lateral “Lateral “1/2”1/2”Inguinal lig.Inguinal lig.

Conjoined tendon =Falx InguinalisAttached to pectinealLine of superior pubic RamusThin and weak

Rectus sheath

Lowerribs

Innervated by the genital branch of theGenitofemoral nerve (Cremaster reflex, L1)

Ribs and Costal margin

Thoracolumbar fascia

Iliac crest

Lateral “1/3”Inguinal ligament

(Does not contributea layer to the spermatic cord)

Ribs 5-7 &Xyphoid process

Pubic crestPubic symphysis

Linea alba

LineaSemilunaris

Arcuate line: The crescent shaped inferior border of the posterior layer of the rectus sheath Locate approximately 1/3 of the distance from the umbilicus to the pubic crest.

Anterior rami of spinal nerves

Motor - abdominal musclesSympathetics – sweat glands, blood v.Sensory - skin, muscles, and parietal peritoneum

Travel between the internal oblique and transverse abdominus muscles, pierce the rectus sheath to supply the rectus abdominus and provide ant. cutaneous branches.

T7-T11 Thoracoabdominal nervesT12 Subcostal nerveL1 Iliohypogastric nerveL1 Ilioinguinal nerve

Dermatome

T7

T10

L1

Internal thoracic

Musculophrenic

Posteriorintercostal

Subcostal

External Iliac

Femoral Superficial epigastricSuperficial circumflex iliac

(small vessel)

Median

Paramedian

Suprapubic

subcostal

XMcBurney’spointASIS

• Inguinal Canal• An oblique intermuscular passage through the inferior portion of the anterior

abdominal wall.

• During development, it serves as a route of passage for the testes from the posterior abdominal wall to the scrotum.

• It contains the spermatic cord in males and the round ligament in females.

• It runs parallel and superior to the inguinal ligament along the medial one-half of the ligament.

• It is 4-5 cm in length.

• It runs deep (lateral) to superficial (medial).

• It extends from the deep inguinal ring (lateral) to the superficial inguinal ring (medial).•

MedialCrus

LateralCrus

Intercruralfibers

Spermatic cord Contents Ductus deferens Testicular A., Vas A. Pampiniform plexus lymph vessels Nerves

Layers External spermatic f. Cremasteric fascia Internal spermatic f. -Transversalis f.

Hydrocele excess fluid in a persistent process vaginalis Cord or testis

Blood supplyNerve supplyLymphatic drainage

XII Clinical Correlation: Inguinal Hernias

Hernia: the abnormal protrusion of a structure from the cavity in which it belongs.

Inguinal hernia: abdominal hernia through the anterior abdominal wall in the inguinal region

Direct: Leaves the abdominal cavity medial to the inferior epigastric artery (within the inguinal triangle).Travels anteriorly through the posterior wall of the inguinal canal that is formed by transversalis fascia and exits via the superficial inguinal ring, hence only the medial portion of the inguinal canal is traveled.Covered by one or two layers of the spermatic cord.Transversalis fascia forms the hernial sac.Less common than indirect hernias, usually occurs in men older than 40 years.

Indirect: Leaves the abdominal cavity lateral to the inferior epigastric arteryTravels through the deep inguinal ring, the entire inguinal canal, and the superficial inguinal ring.Originates lateral to the inferior epigastric vessels.Covered by all three layers of the spermatic cord.The remains of the process vaginalis forms the hernial sac.

20 times more common in males than females.

Boundaries of the Inguinal Triangle