48. Anatomy | Anterior Abdominal Wall and Inguinal Canal

Which organs are located in the Right Upper Quadrant (RUQ)?

Right lobe of liver, gallbladder, right kidney, duodenum, head of pancreas, right colic flexure, right half of transverse colon, pyloric sphincter, right adrenal gland

What are the clinical correlates of RUQ pain?

Acute cholecystitis, hepatitis, pancreatitis

Which organs are located in the Left Upper Quadrant (LUQ)?

Left lobe of liver, stomach, tail of pancreas, spleen, left kidney, left colic flexure, left half of transverse colon, phrenicocolic ligament

What are the clinical correlates of LUQ pain?

Splenic rupture, gastric ulcer, pancreatitis, phrenicocolic ligament injury

Which organs are located in the Right Lower Quadrant (RLQ)?

Appendix, cecum, ascending colon (lower part), right ovary, ileum and jejunum

What are the clinical correlates of RLQ pain?

Appendicitis (classic McBurney's point tenderness)

Which organs are located in the Left Lower Quadrant (LLQ)?

Sigmoid colon, left ovary, descending colon (lower part)

What are the clinical correlates of LLQ pain?

Diverticulitis of descending or sigmoid colon

Which anatomical planes divide the abdomen into quadrants?

Median plane (linea alba) and Transumbilical plane (umbilicus)

What is the fiber direction of the external oblique?

Inferomedial ('hands in pockets')

What is the contribution of the external oblique to the rectus sheath?

Anterior lamina

What is the fiber direction of the internal oblique?

Superomedial, perpendicular to EO

What is the contribution of the internal oblique to the rectus sheath?

Splits into anterior and posterior lamina

What is the fiber direction of the transversus abdominis?

Horizontal

What is the contribution of the transversus abdominis to the rectus sheath?

Posterior lamina (above arcuate line only)

What is the orientation of rectus abdominis fibers?

Superior-inferior

What fasciae overlie the anterior abdominal wall?

Camper's (fatty) and Scarpa's (membranous) fascia

What forms the anterior rectus sheath above the umbilicus?

EO aponeurosis + anterior IO aponeurosis

What forms the posterior rectus sheath above the umbilicus?

Posterior IO aponeurosis + TA aponeurosis

What forms the anterior rectus sheath below the arcuate line?

EO aponeurosis + IO aponeurosis + TA aponeurosis

What forms the posterior rectus sheath below the arcuate line?

Absent; only transversalis fascia + peritoneum

Which dermatome corresponds to the nipple?

T4

Which dermatome corresponds to the umbilicus?

T10

Which dermatome corresponds to the subcostal region?

T12

Which nerves are included in the thoracoabdominal nerves?

T7-T12, run between IO & TA

What is the mnemonic for lumbar plexus nerves of the abdominal wall?

I (twice) Got Laid On Friday: Iliohypogastric (L1), Ilioinguinal (L1), Genitofemoral, Lateral cutaneous of thigh, Femoral

Which arteries run vertically in the rectus abdominis?

Superior epigastric (downward), inferior epigastric (upward); they anastomose

Why is the linea alba a preferred incision site?

Midline incision avoids neurovasculature, wide access

What are disadvantages of linea alba incision?

Poor blood supply → delayed healing; perpendicular to tension lines

Why is McBurney's point an ideal incision site for appendectomy?

Parallel to tension lines; between EO & IO fibers (splitting not cutting); rapid healing

What does the umbilical vein become in adults?

Round ligament of liver (ligamentum teres hepatis)

What do the umbilical arteries become in adults?

Medial umbilical ligaments

What does the urachus become in adults?

Median umbilical ligament

What does the upper gubernaculum become in females?

Ovarian ligament

What does the lower gubernaculum become in females?

Round ligament of uterus

What does the gubernaculum become in males?

Scrotal ligament (guides testicular descent)

What does the processus vaginalis become in adults?

Tunica vaginalis

What does Scarpa's fascia become in males?

Dartos fascia

What clinical condition results from a patent processus vaginalis?

Congenital indirect inguinal hernia or hydrocele

What is the cremasteric reflex?

Stroking thigh → testis elevates via cremaster muscle

What is the mnemonic for spermatic cord layers?

ICE: Internal spermatic fascia, Cremasteric fascia, External spermatic fascia

What does the internal spermatic fascia derive from?

Transversalis fascia

What does the cremasteric fascia and muscle derive from?

Internal oblique muscle

What does the external spermatic fascia derive from?

External oblique aponeurosis

What does the tunica vaginalis derive from?

Processus vaginalis (peritoneum)

What does the dartos fascia derive from?

Scarpa's fascia

Which abdominal wall layer corresponds to the scrotum?

Skin → Scrotum

Which abdominal wall layer corresponds to the external spermatic fascia?

External oblique aponeurosis

Which abdominal wall layer corresponds to the cremaster muscle and fascia?

Internal oblique aponeurosis

Which abdominal wall layer corresponds to the internal spermatic fascia?

Transversalis fascia

Which abdominal wall layer corresponds to the tunica vaginalis?

Peritoneum

What structure underlies the median umbilical fold?

Urachus remnant

What structure underlies the medial umbilical fold?

Obliterated umbilical arteries

What structure underlies the lateral umbilical fold?

Inferior epigastric vessels

Which fossa is superior to the bladder?

Supravesical fossa

Which fossa is medial to the inferior epigastric vessels?

Medial inguinal fossa (Hesselbach's triangle)

Which fossa is lateral to the inferior epigastric vessels?

Lateral inguinal fossa (deep ring site)

What is the pathway of an indirect inguinal hernia?

Through deep inguinal ring → canal → superficial ring (may enter scrotum)

What is the relation of an indirect hernia to the inferior epigastric vessels?

Lateral

What coverings does an indirect inguinal hernia have?

All 3 spermatic fascias (ICE)

What patients are typical for indirect inguinal hernia?

Infants (congenital, patent processus vaginalis) or young males

What are clinical features of indirect hernia?

Bulge following testicular descent path; hydrocele possible

What is the pathway of a direct inguinal hernia?

Through Hesselbach's triangle → superficial ring

What is the relation of a direct hernia to the inferior epigastric vessels?

Medial

What coverings does a direct inguinal hernia have?

External spermatic fascia only

What patients are typical for direct inguinal hernia?

Elderly men with acquired transversalis fascia weakness

What are clinical features of direct hernia?

Groin bulge, impulse medial on finger exam

What is the pathway of a femoral hernia?

Through femoral ring, below inguinal ligament

What patients are typical for femoral hernia?

More common in females

What are clinical features of femoral hernia?

Bulge on proximal thigh, high strangulation risk

What is the pathway of an umbilical hernia?

Umbilical ring defect

What patients are typical for umbilical hernia?

Infants, obese adults

What are clinical features of umbilical hernia?

Midline bulge at umbilicus

How do you distinguish indirect from direct hernia on exam?

Finger in superficial inguinal ring, patient coughs → Impulse at fingertip (lateral) = Indirect; Impulse at medial side of finger = Direct

Where does a direct inguinal hernia occur anatomically?

Through Hesselbach's Triangle, medial to inferior epigastric vessels, exits superficial inguinal ring

What is the cause of a direct inguinal hernia?

Acquired transversalis fascia weakness

What is the herniation covering of a direct inguinal hernia?

External spermatic fascia only

What is the typical presentation of a direct inguinal hernia?

Elderly men, groin herniation, pain/tenderness, erythema, fever

Where does an indirect inguinal hernia occur anatomically?

Through deep inguinal ring, lateral to inferior epigastric vessels

What is the cause of an indirect inguinal hernia?

Persistent processus vaginalis (failure to close)

What is the herniation covering of an indirect inguinal hernia?

All 3 spermatic fascia layers (ICE)

What is the typical presentation of an indirect inguinal hernia?

Infant or adult male, groin herniation, pain/tenderness, erythema, fever; hydrocele risk in infants

Which organ in the RUQ is most associated with gallstones?

Gallbladder

Which organ in the RUQ is involved in hepatitis?

Liver (right lobe)

Which organ in the RUQ is associated with pancreatitis?

Head of pancreas

Which organ in the LUQ is most commonly injured in trauma?

Spleen

Which ligament in the LUQ supports the colon and may be damaged?

Phrenicocolic ligament

Which organ in the LUQ is a common site for gastric ulcer?

Stomach

Which organ in the RLQ is classically involved in appendicitis?

Appendix

Which point in the RLQ is used for appendectomy incision?

McBurney's point

Which structure in the LLQ is most often affected in diverticulitis?

Sigmoid colon

Which quadrant contains the right ovary?

Right lower quadrant (RLQ)

Which quadrant contains the left ovary?

Left lower quadrant (LLQ)

What is the linea alba?

Midline connective tissue that divides rectus sheath vertically

What happens to the rectus sheath below the arcuate line?

Posterior sheath absent; rectus abdominis rests on transversalis fascia and peritoneum

Where do thoracoabdominal nerves run in the abdominal wall?

Between internal oblique and transversus abdominis

Where do superior and inferior epigastric arteries anastomose?

Within rectus abdominis muscle

Why does a linea alba incision heal poorly?

Because of poor vascularity and perpendicular to tension lines

Why is McBurney's point incision advantageous?

It follows muscle fiber orientation, minimizes muscle cutting, and is in correct location for appendix

Which adult ligament is the remnant of the umbilical vein?

Round ligament of liver (ligamentum teres hepatis)