Anatomy of the abdominal wall and inguinal region week 1

Question 1

What are the boundaries of the abdominal cavity? (inferior and superior borders, walls of cavity)

What are the functions of the walls of the abdominal cavity?

Answer 1

The extent of the abdomen is from the diaphragm, xiphoid process and costal margin of ribs 7-10 superiorly to the iliac crest, anterior superior iliac spine, inguinal ligament, pubic symphysis inferiorly. The abdominal musculature forms the anterior wall. The lower thoracic and lumbar vertebra, muscles, and fascia form the posterior wall of the abdomen. The abdominal wall functions to expand when needed and to hold everything in place.

Question 2

How does the abdomen communicate with the thoracic and pelvic cavities?

Answer 2

• Abdomen to Thorax: openings in diaphragm
• Abdomen to Pelvis: open communication

Question 3

Define the following terms/muscles/landmarks of surface anatomy.

linea alba

rectus abdominus muscles

umibilicus (what is it associated with?)

linea semilunaris

tendinous insertions

Answer 3

• linea alba – midline structure noting left and right halves
• rectus abdominus muscles – connects the ribs to the pelvis (a.k.a. “six pack”)
• umbilicus – marks entrance of the umbilical cord, commonly associated with the 10th thoracic level
• linea semilunaris – the lateral edge of the rectus abdominus (a.k.a. semilunar line)
• tendinous insertions – interruptions in the rectus abdominus (a.k.a. transverse lines)

The linea alba and linea semilunaris are where the aponeuroses of some muscles meet. Because there is no vasculature or innervation to these areas, they are good places for surgical access.

Question 4

What are the boundaries used in the 4 quadrant system?

What organs exist in each of the 4 quadrants?

Answer 4

The 4 Quadrant System (most commonly used). 4 quadrants are marked by a perpendicular line through the linea alba and a transverse line through the umbilicus.
Right Upper Quadrant – liver, gall bladder, first 3 parts of the duodenum, head of the pancreas, pyloric portion of the stomach, right kidney, ureter and suprarenal gland, upper position of the ascending colon, right half of the transverse colon.
Left Upper Quadrant – cardiac and fundic regions of the stomach, left half of the transverse colon, upper position of the descending colon, body and tail of the pancreas, spleen, left kidney, ureter and suprarenal gland.
Right Lower Quadrant – lower portion of the ascending colon, appendix, right ureter.
Left Lower Quadrant – lower portion of the descending colon, sigmoid colon, left ureter.

Question 5

What are the boundaries used in the 9 quadrant system? What are the quadrants and what embryological structures are they associated with? Why is this clincally significant?

Answer 5

The 9 Quadrant System.
• Vertical lines extend downward from the midclavicular line.
• 2 horizontal lines:
• Subcostal (lower part of the costal margin)
• Intertubercular (extending between the iliac crests.

Organs derived from the foregut tend to refer pain to the epigastric region. Midgut–> umbilical region. Hindgut–> pelvic/hypogastric region

see slide 11 of notes

Question 6

What is the transpyloric plane? What organs are associated with it? What is the clinical significance of it?

Answer 6

Transpyloric plane – passes through the 1st lumbar vertebra (this is halfway between the pubic symphysis and the jugular notch.) Plane passes through the pylorus of the stomach, fundus of the gallbladder, neck and body of the pancreas, hila of the kidneys, 1st part of the duodenum, origin of the superior mesenteric artery.

Question 7

What nerves supply the abdominal wall?

What is an important neural landmark on the abdomen and why?

Answer 7

• innervation from the thoracic intercostal nerves T7-T12 and L1 (1st lumbar nerve; also called the iliohypogastric nerve.)
• an important neural landmark is the umbilicus which marks the 10th thoracic spinal level-used to assess spinal cord lesions

Question 8

What is the primary arterial supply of the abdominal wall? What aa is it a continuation of? Where does it run in the abdominal wall? What aa does it join?

Answer 8

• The primary arterial supply is the superior epigastric artery, a continuation of the internal thoracic artery. It runs in btwn the linea alba and semilunar line (see attached pic)
• runs deep to the rectus abdominus.
• joins the inferior epigastric, a branch of the external iliac artery.

Question 9

What other arteries supply the abdominal wall?

Answer 9

• lower posterior intercostal arteries.
• lumbar arteries.
• branches of the femoral artery (superficial epigastric, superficial circumflex iliac, and superficial external pudendal; do not try to find these but know they exist.)
• The veins generally follow the arterial pathways.

Question 10

T or F: The abdominal wall is organized into flat sheets of fascias, connective tissue and muscle.

Answer 10

True

Question 11

Explain the anatomy of the fascia of the abdominal wall that lies just beneath the skin (superficial fascia).

Answer 11

• uniform in thickness above the umbilicus.
• divided into 2 layers below the umbilicus.

Camper’s fascia - outer fatty layer.
Scarpa’s fascia - deeper fibrous layer

Question 12

What does the Scarpa’s fascia become after it extends below the inguinal ligament?

Answer 12

• extends below the inguinal ligament to adhere to the fascia lata of the thigh
• continues to the scrotum to become dartos tunic
• continues into the perineum as Colles’ fascia
• extends as the superficial penile fascia. in females, ends at the clitoris and labia majora

Question 13

What is one clinical relevance of Scarpa’s fascia that could become an issue in a male with a penetrating wound or anterior pelvic fracture?

Answer 13

Accumulations of fluid trapped beneath Scarpa’s fascia cannot escape into the fascia of the thigh due to the tight connection with the inguinal ligament, but can flow downward beneath the superficial penile and dartos fascias surrounding the penis and scrotum. This could occur with a penetrating wound or anterior pelvic fracture that transects the penile urethra (urinary outflow interrupted-fluid accumulation).

Question 14

What is the deep fascia?

What is the transversalis fascia?

Answer 14

Deep fascia:
• lateral to the semilunar lines - aponeuroses of the 3 flat abdominal muscles.
• medial to the semilunar lines - layers of the Rectus Sheath which envelops the rectus abdominus muscle.

Transversalis fascia – the deepest layer of the abdominal wall (equivalent to the endothoracic fascia of the thorax.)

Question 15

How many muscles are there that form the anterolateral abdominal wall? What are those muscles?

What are the functions of the flat muscles?

What is the “added feature” of the straight muscle?

Answer 15

There are 4 muscles forming the anterolateral abdominal wall. The three flat muscles of the abdominal wall help rotate, compress and expand the abdominal cavity. The one straight muscle has the added feature of acting on the pelvis and trunk.

Question 16

Question 17

What muscle does the rectus sheath enclose? What is it composed of?

Answer 17

• a deep fascial envelope that encloses the rectus abdominus muscle.
• a fusion of the external oblique, internal oblique and transversus abdominis aponeuroses

The rectus sheath provides a firm attachment for the 3 flat muscles of the anterolateral abdominal wall with their counterparts on the other side.

Question 18

How does the rectus sheath vary above and below the arcuate line? Why does this occur?

Answer 18

• The rectus sheath varies above and below the arcuate line which is a site of transition.
• Superior to the arcuate line:
oAnterior sheath - aponeuroses of the External Oblique and Internal Oblique.
oPosterior sheath - aponeuroses of the Internal oblique and Transversus Abdominis.
• Inferior to the arcuate line:
oAnterior sheath - aponeuroses of ALL 3 LAYERS.
oThe posterior sheath is formed by the transversalis fascia.

Question 19

What aa is associated with the arcuate line? In what relation to the arcuate line does it pass? (anterior, posterior) What structure does it enter?

Answer 19

The inferior epigastric aa travels anterior to the arcuate line to enter the rectus sheath.

Question 20

What is the urachus? What is its remnant in the adult?

Answer 20

The urachus is a remnant of urinary bladder development connecting the urinary bladder with the umbilical cord. At birth it begins to shrink and fuse into a fibrotic string of tissue to become the Median Umbilical Fold. On occasion it can remain patent with leakage of urine through the umbilicus

Question 21

What are the remnants of the 2 umibilical arteries in an adult?

Answer 21

The 2 umbilical arteries reach the umbilical cord by travelling along the inside of the abdominal wall. After birth, these vessels obliterate and lie within the Medial Umbilical Folds.

Question 22

Where are the lateral umbilical folds? What aa lies within them?

Answer 22

Lateral to the medial umbilical folds. The inferior epigastric arteries lie within the Lateral Umbilical Folds.

Question 23

Where is the inguinal region? What is the inguinal canal?

What are the openings of the inguinal canal?

Answer 23

Where is it? Inguinal refers to the two creases between the abdomen and the thighs.
What is it shaped like? – an oblique passage way in the lower aspect of the anterior abdominal wall running parallel and superior to the medial half of the inguinal ligament.
Surface - roughly triangular. the medial opening of the canal is superior to the pubic tubercle.
Deep – located just lateral to the inferior epigastric vessels and immediately superior to the midpoint of the inguinal ligament.
• a canal connecting the pelvic cavity with the scrotum or labia majora.
What are the openings?
• deep ring (opening into the pelvic cavity.)
• superficial ring (opening into the proximal portion of the scrotum or the labia majora.)

Question 24

In females, what are the contents of the inguinal canal? What are the functions of its contents?

Answer 24

Female Inguinal Canal

1. Round ligament of the uterus (extends between the uterus and the labia majora).
2. Ilioinguinal nerve (L1 - a branch of the lumbar plexus; exits the superficial ring to supply the skin of the anterior part of the mons pubis and labia majora.)

Question 25

In males, what are the contents of the inguinal canal? What are the functions of its contents?

Answer 25

Male Inguinal Canal

1. Ilioinguinal nerve (L1 - a branch of the lumbar plexus that exits the superficial ring to supply the skin of the lateral and anterior scrotum.)
2. Spermatic cord (formed during descent of the testis and contains structures related to the testis.) begins at the deep ring, courses through the inguinal canal to exit the superficial ring to enter the scrotum.

Question 26

What are the contents of the spermatic cord?

Answer 26

Key Concept: The Spermatic Cord is a “2-way street” conveying materials to and from the testes.
The structures in the spermatic cord include the:
• vas (ductus ) deferens
• artery to vas deferens (embedded in wall of vas deferens and from the inferior vesical artery)
• testicular artery (from the abdominal aorta);
• pampiniform plexus of veins (testicular veins);
* Do not try to find the following structures, but know they are present
• *cremasteric artery and vein (small vessels associated with the cremasteric fascia);
• *genital branch of the genitofemoral nerve (innervation to the cremasteric muscle);
• *sympathetic and visceral afferent nerve fibers;
• *lymphatics

Question 27

What are the coverings of the spermatic cord? Where do they come from?

Answer 27

Coverings of the spermatic cord :
A. external spermatic fascia from the external oblique
B. cremasteric fascia and the loops of cremasteric muscle from the internal oblique
C. internal spermatic fascia from the transversalis fascia. h

Question 28

How is the inguinal (Poupart’s) ligament formed?

Where does it extend from?

What are its openings?

Answer 28

The inguinal (Poupart's) ligament :
• formed when the lower border of the external oblique folds under itself forming a trough-like structure which forms most of the inguinal canal. (“looks like a taco shell” quote from Dr. Keith Millikan, general surgeon.)
• extends from the anterior superior iliac spine to the pubic tubercle.
• Deep inguinal ring – internal opening
• Superficial inguinal ring – external opening (medial end of the ligament)

Question 29

What fibers are associated with the superficial inguinal ring?

Answer 29

• Superficial inguinal ring – external opening (medial end of the ligament)
• lateral (inferior) crus fibers .
• medial (superior) crus fibers.
• Intercrural fibers.

Question 30

Question 31

What are the boundaries of the inguinal canal?

Answer 31

The Inguinal Canal.
• Anterior wall - aponeurosis of the external oblique.
• Posterior wall - transversalis fascia. reinforced along its medial one-third by the conjoint tendon of the transversus abdominis and internal oblique.)
• Roof (superior wall) - arching fibers of the transversus abdominis and internal oblique.
• Floor (inferior wall) - inguinal ligament

Question 32

male

Answer 32

female

Question 33

Describe the process of formation of the inguinal canal and descension of gonads in males.

Answer 33

The Inguinal Canal and Spermatic Cord are formed during descent of the testis and conveys structures related to the testis between the deep ring and the scrotum.

The gonads develop first in the abdominal cavity and then “descend.” The ovaries stay in the pelvic cavity, but the testes continue into the scrotum. In order to get to their final location the testes pass through the deep inguinal ring, the inguinal canal and the superficial inguinal ring. The gubernaculum (pictured) guides the descent of the gonads.

Question 34

What is the route for an indirect inguinal hernia? What is the relation of the herniated organs to the inferior epigastric vessels? How many layers of spermatic fascia is this type of hernia covered by?

Answer 34

Indirect inguinal hernias - abdominal contents protrude through the deep inguinal ring lateral to the inferior epigastric vessels. After passing through the inguinal canal and superficial ring, the viscera can continue and coil in the scrotum. Indirect hernias follow the route taken by the testis and are found within the spermatic cord. They are covered by the 3 layers of spermatic fascia.

Question 35

What is the route for a direct inguinal hernia? What is the relation of the herniated organs to the inferior epigastric vessels? How many layers of spermatic fascia is this type of hernia covered by?

Answer 35

Direct inguinal hernia - abdominal contents protrude through the weak area of the posterior wall of the inguinal canal medial to the inferior epigastric vessels (in the inguinal [Hesselbach’s] triangle). Direct hernias rupture through the posterior wall of the inguinal canal and are usually found on the surface of the spermatic cord and bulge at the superficial ring. They may be covered by only the external layer of spermatic fascia.

Question 36

hydrocele

Answer 36

Hydrocele – an abnormal accumulation of fluid in the cavity of the tunica vaginalis

Question 37

vasectomy

Answer 37

Vasectomy – cutting and ligation of the ductus deferens