20-01-23 - Abdominal wall 2: Posterior wall, neurovascular supply, femoral hernias Flashcards
Learning outcomes
- State the actions and functions of quadratus lumborum; psoas (major and minor); iliacus
- Describe muscular and vascular compartments deep to the inguinal ligament and the structures in these compartments
- Describe briefly important arterial anastomoses on the abdominal wall and explain the importance of these
- Explain the clinical anatomy of venous drainage of the abdominal wall
- Describe the general pattern of lymph drainage of the abdominal wall
- Describe the nerve supply of the skin and muscles of the abdominal wall
- Explain the anatomical correlates of femoral hernias
What is a hernia?
Where do inguinal hernias usually appear?
What is Hesselbach’s (inguinal) triangle?
What is located on its medial corners?
What causes direct inguinal hernias?
Where may structures pass through?
What is this structure parallel to?
What is it covered by?
What do structures not enter in a direct hernia?
- A condition in which part of an organ is displaced and protrudes through the wall of the cavity containing it
- Occurs in weaker areas
- An inguinal hernia usually appears above & medial to the pubic tubercle
- Hesselbach’s (inguinal) triangle is a weak area on the posterior wall of the inguinal canal, medial to the inferior epigastric vessels
- On the medial corner of the Haselbach’s (inguinal) triangle is the inguinal falx (conjoint tendon)
- Direct inguinal hernias are usually caused by a weaker conjoint tendon (usually in adult male) and increased intraabdominal pressure resulting in fat or small bowel pushing through the peritoneum and transversalis fascia in Haselbach’s triangle
- Structures may pass through the superficial inguinal ring to enter the scrotum, which is parallel to the spermatic cord
- The superficial inguinal ring is covered by peritoneum, transversalis fascia (and conjoint tendon)
- Although these structures may go pass through the superficial inguinal ring to enter the scrotum, they do not enter the inguinal canal
Inguinal and femoral hernia diagram
Where do abdominal contents move in indirect inguinal hernias?
What is the processus vaginalis?
How can persistent processus vaginalis lead to indirect inguinal hernias?
What are contents of indirect inguinal hernias covered by?
- In direct inguinal hernias, abdominal contents pass through deep inguinal ring, so will be within the inguinal canal
- The processus vaginalis is the peritoneal tunnel through which the testes migrate from the retroperitoneum toward the scrotum during embryological development
- The deep inguinal ring is normally closed, but with persistent processus vaginalis, the deep inguinal ring is open, allowing for indirect inguinal hernias to occur
- The contents of indirect inguinal hernias are covered by all the layers of the spermatic cord due to moving through the deep inguinal ring
Mechanism of hernia
- Mechanism of hernia
- On coughing & straining (e.g. micturition, defecation & parturition):
- The arching lowest fibres of the internal oblique & transversus abdominis muscles contract flattening out the arched roof of the inguinal canal so that it is lowered toward the floor
- The roof may actually compress the contents of the inguinal canal against the floor so that the canal is virtually closed
- When great straining efforts may be necessary (e.g. defecation & parturition):
- The person naturally tends to assume the squatting position
- The hip joints are flexed & the anterior surfaces of the thighs are brought up against the anterior abdominal wall
- By this, the lower part of the anterior abdominal wall is protected by the thighs
- However, particularly in the male, the inguinal region is susceptible
- to the development of hernias
Summary of hernias
- Summary of hernias
- Hernias usually present with a lump at an appropriate anatomical site
- Hernias often increases in size on coughing or straining
- Hernias reduce in size or disappears when relaxed or in supine position
- Examination may show a hernia to have a cough impulse & to be reducible
- Irreducible but non-obstructed hernias may cause little pain
- If a hernia causes obstruction (colicky abdominal pain, distension & vomiting may occur), it will be tense, tender & irreducible
- If strangulation occurs the lump will become red & tender
- Diagnosis is usually based on clinical features!
Inguinal hernia
What are the 5 muscles of the posterior abdominal wall?
What are 3 other structures present in the posterior abdominal wall?
- 5 muscles of the posterior abdominal wall:
1) Quadratus lumborum
2) Psoas major
3) Psoas minor
4) Diaphragm
5) Iliacus - 3 other structures present in the posterior abdominal wall:
1) Lumbar vertebrae and intervertebral discs – Lumbar lordosis area
2) Inferior vena cava and aorta
3) Paravertebral gutters – found between muscles, kidneys, and ascending and descending colons
What 2 structures does the quadratus lumborum originate from?
What 2 structures does the quadratus lumborum insert on?
What are the 2 actions of the quadratus lumborum?
What is the innervation to the quadratus lumborum?
What does the fascia of the quadratus lumborum form?
- 2 structures the quadratus lumborum originate from:
1) Inferior border of 12th rib
2) Transverse processes of L1-4 vertebrae - 2 structures the quadratus lumborum inserts on:
1) Iliolumbar ligament
2) Iliac crest - 2 actions of the quadratus lumborum:
1) Pulls down the 12th rib, helps descent of the diaphragm during inspiration
2) Lateral flexion of the vertebral column - The innervation of the quadratus lumborum comes from T12 – L4
- The fascia of the quadratus lumborum constitutes the lateral arcuate ligament
What 2 structures does the psoas major originate from?
What structure does the psoas major insert on?
What are 3 actions of the psoas major?
What is the innervation to the Psoas major?
What does the fascia of psoas major constitute?
- 2 structures the psoas major originate from:
1) Transverse processes of lumbar vertebrae
2) Bodies of T12-L4 and IV discs - The psoas major inserts on the lesser trochanter
- 3 actions of the psoas major:
1) Flexion of the thigh (with iliacus)
2) Flexion of the trunk (with iliacus)
3) Lateral flexion of the vertebral column - The innervation to the psoas major comes from L1-3
- The fascia of psoas major constitutes the medial arcuate ligament
What structure does the psoas minor originate from?
What 2 structures does the psoas minor insert on?
What is the innervation to the psoas minor?
- The psoas minor originates from the Bodies of T12-L1 (and partially on the inguinal ligament)
- 2 structures the psoas minor inserts on:
1) Pectineal line
2) iliopectineal eminence - The innervation to psoas minor is from L1
What 3 structures does the iliacus originate from?
What structure does the iliacus insert on?
What is the innervation to the iliacus?
What is the action of the iliacus?
- 3 structures the iliacus originates from:
1) Iliac fossa (fills it)
2) Iliac crest
3) Anterior sacroiliac ligament - The iliacus inserts on the Lesser trochanter
- The innervation to the iliacus comes from the Femoral nerve (L2-4)
- The action of the iliacus is flexion of the thigh (with psoas major)
How is this space between the inguinal ligament and the hip bone divided?
What is the femoral sheath continuous with?
What 4 structures are transmitted in the muscular compartment?
What 2 structures are transmitted in the vascular compartment?
- The space between the inguinal ligament and the hip bone is divided by the femoral sheath into muscular and vascular compartments
- The femoral sheath is continuous with transversalis and iliac fascias
- 4 structures transmitted in the muscular compartment:
1) Psoas major
2) Iliacus
3) Femoral nerve
4) Lateral cutaneous nerve of the thigh (own lateral most quarter of muscular compartment underneath the inguinal ligament) - 2 structures are transmitted in the vascular compartment:
1) Femoral vessels
2) Femoral branch of genitofemoral nerve
What structure exists medial to the vascular compartment?
What is the femoral ring an opening to?
What 4 structures is the femoral ring bounded by?
What is the femoral ring closed by?
How can herniation in this area occur?
- Medial to the vascular compartment, between the lacunar ligament and femoral vein, is the femoral ring
- The femoral ring is the opening of the femoral canal, a conical shaped potential space where fascia becomes lose.
- 4 structures the femoral ring bounded by:
1) Inguinal ligament (Anteriorly)
2) Lacunar ligament (Medially)
3) Pectineus or pectineal ligament (Posteriorly)
4) Femoral vein (Laterally) - The femoral ring is closed by extraperitoneal tissue
- If intraabdominal pressure is high or the extraperitoneal tissue is weak, the contents of the abdominal cavity can herniate into the femoral canal, which will form a femoral hernia
What is the femoral ring often associated with?
How can be differentiate from an inguinal and femoral hernia?
Which groups are femoral hernias more common in?
- The femoral ring is a weak area and often associated with abnormal protrusion of the abdominal organs into the femoral canal
- The pubic tubercle can be a useful landmark to differentiate an inguinal from a femoral hernia
- A femoral hernia appears below & lateral to the pubic tubercle, and is more prone to strangulation than inguinal hernias
- Femoral hernias are 20x more common in females
Femoral hernia diagram
What is the arterial supply to abdominal wall like?
What are the 7 arteries that supply the abdominal wall?
- The abdominal wall is supplied by numerous arteries, with good anastomosis between all the vessels
- 7 arteries that supply the abdominal wall:
1) Intercostal arteries
2) Lumbar arteries (posteriorly)
* Branches of the abdominal aorta
3) Superior epigastric arteries
* Branch of the internal thoracic artery (branch of subclavian)
* Descends behind the rectus abdominis, in rectus sheath
* Anastomoses with the inferior epigastric arteries either side of the midline
4) Inferior epigastric arteries
* Branch of the external iliac
* On the medial side of the deep inguinal ring
* Enter the rectus sheath and ascend behind the rectus abdominis
5) Superficial epigastric arteries
* Branch of femoral artery
6) Superficial circumflex iliac arteries
* Branch of femoral artery
7) Deep circumflex iliac arteries
* Branch of external iliac artery
* Runs laterally, parallel to the inguinal ligament
What can happen if supply to the lower limbs is cut off due to blockage in the abdominal aorta from obesity?
- If supply to the lower limbs is cut off due to blockage in the abdominal aorta from obesity, collateral circulation can be formed
- Blood can go through the subclavian, internal thoracic, superior epigastric, reverse through the inferior epigastric, into the external iliac, and into the femoral artery (continuation of external iliac), which will supply the lower limbs
What accompanies the arteries of the abdominal wall?
Where to these veins drain into superiorly and posteriorly?
Where do these veins radiate out from?
Where can superficial epigastric and superficial circumflex iliac veins drain to?
What is the role of para-umbilical veins?
What is caput medusae?
- All the arteries of the abdominal wall are accompanied by veins
- The veins of the abdominal wall drain into the:
1) Internal thoracic & axillary veins superiorly
2) Femoral & external iliac veins inferiorly - The veins of the abdominal wall radiate out from the umbilicus
- Superficial epigastric & superficial circumflex iliac veins can drain into the proximal end of the great saphenous vein rather than femoral vein
- Para-umbilical veins connect the system through the umbilicus to the portal veins of the liver
- The term ‘caput medusa’ is used for the appearance of distended and engorged umbilical veins, radiating across the umbilicus
What is the superficial anterior and posterior lymph drainage of the abdominal wall?
- Superficial anterior and posterior lymph drainage of the abdominal wall:
- Anterior
- Above umbilicus - anterior axillary nodes
- Below umbilicus - superficial inguinal nodes
- Posterior
- Above iliac crests - posterior axillary nodes
- Below iliac crests - superficial inguinal nodes
Where is lymph from the deeper abdominal wall drained superiorly and inferiorly?
- Lymph from the deeper abdominal wall is drained by vessels alongside the epigastric vessels
- Superiorly to the parasternal nodes then to the mediastinal nodes
- Inferiorly to the external iliac then to the para-aortic nodes
What innervates the abdominal muscles and skin?
What muscles do nerves pass between?
How is the rectus abdominis supplied?
What 2 nerves does L1 contribute to?
What structure are both of these nerves branches of?
What do they supply?
- Abdominal muscles and skin are supplied by T7-L1 spinal nerves
- Nerves pass between internal oblique & transversus abdominis and supply them
- Nerves enter the rectus sheath to supply rectus abdominis
- L1 contributes to:
1) Iliohypogastric
2) Ilioinguinal nerves - Both of these nerves are branches of the lumbar plexus
- They supply the inferior part of the abdominal wall
What nerves supply the epigastrium, umbilicus, and pubic region?
What structure refer pain to these regions?
- Epigastrium (The upper part of your abdomen just below your rib cage) – supplied by T6-7
- Pain is referred from the stomach and oesophagus to this region
- Umbilicus – supplied by T10
- Pain is referred from appendix, gonad & small intestine to this region
- Pubic region – supplied by T12 (subcostal nerve)
- Pain is referred from lower colon, bladder & uterus to this region
What is shingles caused by?
Where do rashes appear?
When is the skin painful? Who is at risk of shingles?
- Shingles is cause by the reactivation of varicella zoster virus that is dormant within nerve cells
- The rash (blisters) can form a band along the course of a nerve (dermatome) on one side of the body
- The skin remains painful until after the rash has gone
- If you had chickenpox, you may be at risk
Where is the lumbar plexus formed?
Where is it visible?
What nerve roots make up the lumbar plexus?
What 7 structures the lumbar plexus supply?
- The lumbar plexus is formed in the psoas major muscle, branches of which is visible on the posterior abdominal & pelvic walls
- The lumbar plexus is made up from the ventral rami of L1-3 + big part of L4
- 7 structures the lumbar plexus supplies:
1) Abdominal muscles
2) Extensor compartment of the thigh
3) Adductor compartment of the thigh
4) Lower limbs
5) Pelvic girdle
6) Gluteal muscles
7) Muscles around hip joint
What are the 7 nerves that make up the lumbar plexus?
- 7 nerves that make up the lumbar plexus:
1) Iliohypogastric (L1)
2) Ilioinguinal (L1)
* Nerve 1 and 2 supply lower parts of the abdominal wall muscles
3) Genitofemoral (L1,2)
* Pierces anterior surface of psoas major and runs on the anterior surface
* Goes through deep inguinal ring through the inguinal canal and passes through the superficial inguinal ring
4) Lateral femoral cutaneous (Lateral cutaneous nerve of thigh) (L2,3)
5) Obturator (L2,3,4)
* Goes towards obturator foramen towards obturator canal
6) Femoral (L2,3,4)
* Biggest branch
* Found between psoas major and iliac, pushes under inguinal ligament, and through the muscular compartment
7) Lumbosacral trunk
* Branch to sacral plexus
Where does the psoas muscle and its sheath arise?
How can infections affect the psoas muscle and its sheathe?
What is this condition known as?
How can it present?
What can it be confused with?
- The psoas muscle and its sheath arise not only from the lumbar vertebrae but also from the intervertebral discs between each vertebra
- Infection (e.g Tuberculosis and salmonella discitis) can pass into the psoas muscle sheath, spread within the muscle and sheath, and may even appear below the inguinal ligament as a mass in the groin area
- This mass is known as a psoas abscess
- Patient pay present with fever and or night sweats (signs of TB)
- Psoas abscesses can be confused with femoral (usually) or inguinal hernia
