Sem 1 - O - Posterior Wall - Fascia, Muscles, Abdominal aorta, IVC, Gonadal vessels, sympathetic chain, Lymphatics, Lumbar plexus

Question 1

A layer of fascia (sheet of connective tissue) lies between the extraperitoneal fascia and the muscles of the posterior abdominal wall. This fascia is continuous with the fascia of the anterolateral abdominal wall. What is the fascia of the anterolateral abdominal wall known as? (separates the deepest anterolateral body wall muscle from the extraperitoneal fat layer)

Answer 1

The fascia of the anterolateral abdominal wall is the transveraslis fascia

The transversalis fascia is continuous with the fascia of the posterior abdominal wall

Question 2

What are the muscles of the posterior abdominal wall?

Answer 2

The psoas major, psoas minor, quadratus lumborum, iliacus and posterior aspect of the diaphragm

Question 3

Whilst the posterior abdominal wall fascia is one continuous sheet, it is anatomically correct to name the fascia according to the structure (muscle) it overlies. WHat is the fascia over the psoas major known as? What is the fascia known as that connects this to the transversalis fascia?

Answer 3

Fascia over the psoas major is known as the psoas fascia The fascia connecting the psoas fascia to the transversalis fascia lies over the quadratus lumborum and is properly known as the thoracolumbar fascia (it is the anterior layer of the thoracolumbar fascia that connects psoas to transversalis fascia)

Question 4

The thoracolumbar fascia consists of the three layers; posterior, middle and anterior. Muscles are enclosed between these layers are what?

Answer 4

Between the anterior and middle thoracolumbar fascia lies the quadratus lumborum Between the middle and posterior thoracolumbar fascia lies the deep back muscles (erector spinae + transversospinalis muscles)

Question 5

The psoas fascia covers the psoas major muscle. It is attached to the lumbar vertebrae medially, continuous with the thoracolumbar fascia laterally and what fascia is it continous with inferiorly?

Answer 5

The psoas fascia is continous with the iliac fascia inferiorly (this is the fascia overlying the iliacus muscle)

Question 6

What does the psoas fascia thicken superiorly to form? What does the fascia over the quadratus lumborum thicken superiorly to form?

Answer 6

The psoas fascia thickens superiorly to form the medial arcuate ligament The fascia over the quadratus lumborum thickens superiorly to form the lateral arcuate ligament

Question 7

The rectus abdominus, at a certain point, is covered immediately posterior by the transversalis fascia At what point is this and why?

Answer 7

Superior to the arcuate line , the internal oblique aponeurosis splits to envelop the rectus abdominus both anteriorly and posteriorly Below the level of the arcuate line, the internal oblique aponeurosis does not split and therefore the transversus abdominus aponeurosis also comes anterior to the rectus sheath meaning the transversalis fascia lies behind the rectus abdominus

Question 8

What is formed by the downward prolongation, behind the inguinal ligament, of the abdominal fascia, the transversalis fascia?

Answer 8

The downward prolongation of the transversalis fascia forms the femoral sheath

Question 9

The femoral sheath is contained within the femoral triangle The femoral nerve, vein, artery and lymphatics are some of the structures which pass within this triangle Which structures pass within the femoral sheath?

Answer 9

Femoral triangle from lateral to medial contains (NAVY) femoral Nerve, Artery, Vein, lYmphatics The femoral artery, vein and lymhatics are contained within the femoral sheath

Question 10

What were the muscles of the posterior abdominal wall again?

Answer 10

There are five muscles in the posterior abdominal wall: the quadratus lumborum, iliacus, psoas major, psoas minor, and the diaphragm.

Question 11

Lets firstly discuss the quadratus lumborum What is its origin and insertion?

Answer 11

The quadratus lumborum arises from the iliac crest and inserts to the 12th rib and the transverse process of L1-4 vertebrae

Question 12

What does contraction of one duadratus lumborum cause? When both quadratus lumborum contract, what is the action? What is the nerve supply to the quadratus lumborum?

Answer 12

Quaratus lumborum actions Unilateral contraction- lateral flexion to same side Bilateral contraction - pressure, and fixes the 12th rib during forced expiration The nerve supply to the quadratus lumborum is the anterior rami of T12-L4 spinal nerves

Question 13

What runs over the superior aspect of the quadratus lumborum?

Answer 13

This would be the lateral arcuate ligament

Question 14

What fascia was continous with the fascia over the psoas? What is the origin and insertion of this musle?

Answer 14

The psoas fascia continues with the fascia overlying the iliacus Iliac origin - origin is from the iliac fossa Insertion - inferiorly the iliacus joins to the psoas to form the iliopsoas and this inerts at the lesser trochanter of the femur

Question 15

What is the function of the iliacus and what is its nerve supply?

Answer 15

Iliacus function - flexion of the hip Nerve supply - femoral nerve (L2-4)

Question 16

The most medial muscle of the posterior abdominal wall is the psoas What is the attachment of the psoas?

Answer 16

The superficial part of the psoas attaches originates from the vertebral bodies and IV discs of T12-L4 and the deep part transverse processes of L1-L5 vertebrae

Question 17

What is the function of the psoas muscle? What is the muscle with the long tendon anterior to the psoas major?

Answer 17

Function of psoas Hip Flexion One contracting - bend trunk laterally Both contracting - raise trunk from supine position Muscle with the long tendon anterior to the psoas major is he psoas minor

Question 18

What is the nerve supply to the psoas muscle?

Answer 18

Lumbar plexus direct banches from L2-4 anterior rami

Question 19

State the attachment, function and nerve supply Quadratus lumborum Iliacus

Answer 19

Quadratus lumborum - * Attaches iliac crest to rib 12 and transverse processes of L1-4 vertebrae * One contracting - laterally flexes trunk, both contracting - pressure and fixation of rib 12 during forceful expiration (nerve - anterior rami T12-L4) Iliacus * Attaches iliac fossa and joins with psoas to insert as iliopsoas at lesser trochanter of femur * Hip flexion, nerve - Femoral nerve (L2-4)

Question 20

State the attachment, function and nerve supply of the psoas major

Answer 20

Attachment * Superficially - Vertebral bodies and IV discs of T12-L4 vertebra * Deep - Transverse processes of L1-L5 vertebrae * Distal attachment - joins with iliacus to insert at lesser trochanter of femur Function - Hip flexion * unilateral contraction - laterally flexes the trunk * Bilateral contraction - raises trunk from supine position (nerve supply - anterior rami L1-3)

Question 21

What does the psoas fascia thicken to form superiorly? What nerve pass beneath this structure? choose from * Greater splanchnic * Sympathetic chain * Least splanchnic * Lesser splanchnic

Answer 21

Superior the psoas fascia thickens to form the medial arcuate ligament - the psoas major passes behind here Least splanchnic (T12-anterior rami) and sympathetic chain pass beneath the mediala rcuate ligament

Question 22

The crus of diaphragm (pl. crura), refers to one of two tendinous structures that extends below the diaphragm to the vertebral column. There is a right crus and a left crus, which together form a tether for muscular contraction. They take their name from their leg-shaped appearance – crus meaning leg in Latin. Where does the right and left crus arise from?

Answer 22

The right crus is the longer of the two - arising fom L1-L3 vertebrae The left crus arises from L1-2 vertebrae

Question 23

The medial tendinous margins of the crura pass anteriorly and medialward, and meet in the middle line to form an arch across the front of the aorta known as what? What is the area behind this arch called?

Answer 23

The right and left crus medial tendinous margins meet in the midline to form the median arcuate ligament Behind this arch is the aortic hiatus for the aorta to pass through the diaphragm

Question 24

What level does the abdominal aorta pass through the diaphgram? What are the two arteries immediately given off from the aorta as it passes through the diaphragm?

Answer 24

The descending aorta passes through the diaphragm at the T12 vertebral level through the aortic hiatus - * immediately after passing through it gives off the inferior phrenic artery branch (this gives the superior suprarenal branch to the suprarenal glands) laterally * and the coeliac trunk anteriorly

Question 25

What level does the abdominal aorta branch at and to supply what?

Answer 25

The abdominal aorta branches at the L4 vertebral level to form the common iliac arteries which go on to supply the lower limbs (external iliac artery) and pelvis (internal iliac artery)

Question 26

State the level at which each of the arteries come off the aorta: Superior mesenteric Gonadal Median sacral Lumbar Inferior mesenteric artery

Answer 26

Superior mesenteric artery - L1 vertebral level Gonadal arteries - L2 vertebral level Median sacral artery -arises at the bifurcation of the aorta at L4 vertebral level Lumbar arteries - arise at each vertebral level Inferior mesenteric artery - L3 vertebral level

Question 27

Aorta lies almost midline with the vertebral column (obviously anteriorly) The inferior vena cava sits slightly to right of the vertebral column \* The lumbar arteries and the median sacral arteries supply what? \* Therefore what do the lumbar veins and median sacral vein drain?

Answer 27

Lumbar arteries and median sacral artery supply the posterior abdominal wall (lumbar arteries also help supply lateral abdominal wall\_ Therefore the lumbar veins and median sacral vein drain the posterior abdominal wall

Question 28

At what level is the inferior vena cava formed and where does it drain?

Answer 28

\* Inferior vena cava formed by the uniting of the common iliac veins at L5 vertebral level \* lies to the right and parallel o the aorta \* pierces the central tendon of the diaphragm at the caval opening at the level of T8 \* drains to the right atrium at the heart

Question 29

Which vein forms the anastomases between the lumbar veins?

Answer 29

The ascending lumbar vein form an anastomoses between the lumbar veins It connects the external iliac and lumbar veins to azygous/hemiazygous veins

Question 30

How is the azygous vein formed? What does the azygous vein drain? Which right posterior intercostal vein does not drain into the azygous vein and why?

Answer 30

The azygous vein is a direct continuation of the right ascending lumbar vein (name changes when the subcostal vein drains) The azygous vein drains 2-11 posterior intercostal veins + subcostal vein The 1st right posterior intercostal vein instead drains directly into the right brachiocephalic vein

Question 31

What forms the hemiazygous vein? What veins drain into the hemiazygous veins?

Answer 31

The hemiazygous vein is a continuation of the left ascending lumbar vein (the name changes when the subcostal vein drains into it) It drains the 9-11 posterior intercostal veins and the subcostal veins

Question 32

What is the venous drainage of the posterior intercostal veins? (this is posterior mediastinum knowledge, only asking because the azygous veins are formed from the ascending lumbar veins which are posterior abdominal wall)

Answer 32

Right posterior intercostal 1st - drains direct to right brachiocephalic vein 2-11 + subcostal vein - drain into azygous vein Left posterior intercostal 1-4 - drain into the left brachiocephalic vein 5-8 - drain into the accessory hemiazygous 9-11 + subcostal vein - drain into hemiazygous

Question 33

The lumbar veins are veins running along the inside of the posterior abdominal wall. They are the lumbar equivalent of the posterior intercostal veins The lumbar veins drain the posterior abdominal wall to where?

Answer 33

the 1st and 2nd lumbar vein drain the posterior abdo wall into the ascending lumbar vein The 3rd and 4th drain into the IVC The 5th drains into the iliolumbar branch of the common iliac vein (this is the branch that gives off the ascending lumbar vein which connects all the lumbar veins)

Question 34

Where do the testicular and ovarian arteies arise? Where do the veins drain?

Answer 34

Gonadal arteries arise direct from the aorta on the lateral aspect at the L2 vertebral level Right gonadal vein drains direct to the IVC Left gonadal vein drains to the left renal vein which then drains to the IVC Left suprarenal vein also joins the left renal vein

Question 35

The sympathetic ganglia receive sympathetic innervation from the spinal cord T1-L2 \* Autonomic fibres form plexuses in abdomen – fibres from sympathetic chains \* The sympathteic chains run either side of vertebral column the full length of the abdomen What do the right and left sympathetic chains join to form inferiorly?

Answer 35

Inferiorly the sympathetic chains fuse to form the ganglion impar

Question 36

What is the difference in location between the superior and inferior hypogastric plexus?

Answer 36

Superior hypogastric plexus is a plexus of nerves situated on the vertebral bodies anterior to the bifurcation of the abdominal aorta L4 The plexus divides into R+L hypogatsric nerves which travel down into the pelvis to form the infeiror hypogastric plexus on either side of the rectum

Question 37

Both superior and inferior hypogastric plexus contain mixed modalities (both sympathetic and parasympathetic) The superior hypogastric plexus receives contributions from the two lower lumbar splanchnic nerves (L3-L4), which are branches of the chain ganglia. They also contain parasympathetic fibers which arise from pelvic splanchnic nerve (S2-S4) and ascend from Inferior hypogastric plexus; Why do they contain branches from pelvic splanchnic nerves?

Answer 37

The pelvic splanchnic nerves need to supply the hindgut of the abdomen and therefore need to travel along the inferior mesenteric artery - the superior hypogastric plexus is on the way to the inferior mesenteric artery pre-aotic plexus

Question 38

Lymph form the pelvis generally drains to the iliac nodes Where does lymph from the body wall, tesits/ovaries and kidneys drain? Where does lymph form the digestive tract drain?

Answer 38

Lymph from body wall, tesits/ovaries and kidneys all drain to para-aortic nodes (lateral to the aorta) Lymph from digestive tract drain to pre-aortic nodes (anterior surface of aorta) - these nodes are around the coeliac, superior mesenteric and inferior mesenteric arteries depending on the area of the digestive tract (foregut, midgut and hindgut respectively)

Question 39

The lymph from the digestive tract all drain to the preaortic nodes before draining to the intestinal trunk which drains to the beginning of the thoracic duct What is the beginning of the thoracic duct known as and at what level is this?

Answer 39

Beginning of the thoracic duct CISTERNA CYHLI - begins at L1/2

Question 40

Where is the lumbar plexus?

Answer 40

The lumbar plexus is a plexus of nerves formed from the anterior rami of spinal nerves L1-4 ith some contributions from the subcostal nerve (T12) Its branches form within the psoas major muscle

Question 41

The anterior rami of the L1-L4 spinal roots divide into several cords. These cords then combine together to form the six major peripheral nerves of the lumbar plexus. These nerves then descend down the posterior abdominal wall to reach the lower limb, where they innervate their target structures. There are some sensory branches to the skin of the pelvis but lumbar plexus mostly supplies the lower limb What are the six major peripheral nerves of the lumbar plexus? State their nerve roots

Answer 41

Iliohypogastric nerve - L1 Ilioinguinal nerve - L1 Genitofemroal nerve - L1,2 Lateral cutaneous nerve of the thigh - L2,3 Obturator nerve - L2,3,4 Femoral nerve - L2,3,4

Question 42

Both iliohypogastric and ilioinguinal nerves arise from the birfurcation of the L1 anterior rami Which is superior? They both run across the quadratus lumborum before peircing which muscle? What do they both provide motor supply to?

Answer 42

Remember ilioHypogastric is superior to the ilioInguinal as H comes before I They run across the quadratus lumborum before piercing the tranversus abdominus to provide motor supply to the internal oblique and transversus abdominus muscles

Question 43

The iliohypogastric and ilioinguinal nerves give off a slightly different sensory supply however How is this?

Answer 43

Iliohypogastric nerve provides sensory supply to lateral gluteal skin and pubic skin Ilioinguinal nerve passes through the superficial inguinal ring to provide sensory to the skin on medial thigh and In men - sensory to root of penis/scortum In women - sensory to mons pubis/labia majora

Question 44

What are the nerve roots of the genitofemoral nerve? What doe the genitofemoral nerve innervate?

Answer 44

Genitofemoral nerve - anterior rami fo L1,2 Genital branches pass through the inguinal canal: Provides sensory innervation to the scrotum and motor to cremaster muscle (men) and sensory to the mons pubis/labia majora (women) Femoral branch Skin of upper anterior thigh

Question 45

What muscle does gentifemoral nerve pierce once formed within the psoas?

Answer 45

The genitfemoral nerve pierces he psoas major and then runs inferiorly along the anterior aspect of the muscle

Question 46

Which nerve of the lumbar plexus has purely a sensory function? What are its nerve roots? What does it innervate?

Answer 46

This is the lateral cutaneous nerve of the thigh - anterior rami of L2,3 It enters the thigh at the lateral aspect of the inguinal ligament, where it innervates the skin over the anterior and lateral aspect of the thigh

Question 47

What are the nerve roots of the femoral nerve? What does it innervate?

Answer 47

Femoral nerve - L2,3,4 Sensory to skin over anterior thigh & medial leg Motor to pectineus, sartorius, iliacus, and anterior compartement of thigh muscles (femoral nerve supplies all the anterior compartment of the thigh (flexors of thigh at hip joint and extensors of leg a knee joint except the psoas major))

Question 48

What are the obturator nerve roots? What does this nerve innervate?

Answer 48

L2,3,4 - supplies sensory innervation 2 medial thigh Motor supply to adductors of the thigh (medial compartment of thigh) - adductor longus, brevis, magnus and gracilis (also supplies obturator externus which is a muscle of the medial compartment however this muslces function is to laterally rotate the hip)