Sem 1 - O - Posterior Wall - Fascia, Muscles, Abdominal aorta, IVC, Gonadal vessels, sympathetic chain, Lymphatics, Lumbar plexus Flashcards
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)
The fascia of the anterolateral abdominal wall is the transveraslis fascia
The transversalis fascia is continuous with the fascia of the posterior abdominal wall
What are the muscles of the posterior abdominal wall?
The psoas major, psoas minor, quadratus lumborum, iliacus and posterior aspect of the diaphragm
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?
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)
The thoracolumbar fascia consists of the three layers; posterior, middle and anterior. Muscles are enclosed between these layers are what?
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)
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?
The psoas fascia is continous with the iliac fascia inferiorly (this is the fascia overlying the iliacus muscle)
What does the psoas fascia thicken superiorly to form? What does the fascia over the quadratus lumborum thicken superiorly to form?
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
The rectus abdominus, at a certain point, is covered immediately posterior by the transversalis fascia At what point is this and why?
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
What is formed by the downward prolongation, behind the inguinal ligament, of the abdominal fascia, the transversalis fascia?
The downward prolongation of the transversalis fascia forms the femoral sheath
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?
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
What were the muscles of the posterior abdominal wall again?
There are five muscles in the posterior abdominal wall: the quadratus lumborum, iliacus, psoas major, psoas minor, and the diaphragm.
Lets firstly discuss the quadratus lumborum What is its origin and insertion?
The quadratus lumborum arises from the iliac crest and inserts to the 12th rib and the transverse process of L1-4 vertebrae
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?
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
What runs over the superior aspect of the quadratus lumborum?
This would be the lateral arcuate ligament
What fascia was continous with the fascia over the psoas? What is the origin and insertion of this musle?
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
What is the function of the iliacus and what is its nerve supply?
Iliacus function - flexion of the hip Nerve supply - femoral nerve (L2-4)
The most medial muscle of the posterior abdominal wall is the psoas What is the attachment of the psoas?
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
What is the function of the psoas muscle? What is the muscle with the long tendon anterior to the psoas major?
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
What is the nerve supply to the psoas muscle?
Lumbar plexus direct banches from L2-4 anterior rami
State the attachment, function and nerve supply Quadratus lumborum Iliacus
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)
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
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
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?
The right crus is the longer of the two - arising fom L1-L3 vertebrae The left crus arises from L1-2 vertebrae
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?
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
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?
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
What level does the abdominal aorta branch at and to supply what?
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)
State the level at which each of the arteries come off the aorta: Superior mesenteric Gonadal Median sacral Lumbar Inferior mesenteric artery
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
Which vein forms the anastomases between the lumbar veins?
The ascending lumbar vein form an anastomoses between the lumbar veins It connects the external iliac and lumbar veins to azygous/hemiazygous veins
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?
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
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)
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
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?
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)
Where do the testicular and ovarian arteies arise? Where do the veins drain?
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
What is the difference in location between the superior and inferior hypogastric plexus?
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
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?
Beginning of the thoracic duct CISTERNA CYHLI - begins at L1/2
Where is the lumbar plexus?
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
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
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
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?
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
The iliohypogastric and ilioinguinal nerves give off a slightly different sensory supply however How is this?
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
What are the nerve roots of the genitofemoral nerve? What doe the genitofemoral nerve innervate?
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
What muscle does gentifemoral nerve pierce once formed within the psoas?
The genitfemoral nerve pierces he psoas major and then runs inferiorly along the anterior aspect of the muscle
Which nerve of the lumbar plexus has purely a sensory function? What are its nerve roots? What does it innervate?
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
What are the nerve roots of the femoral nerve? What does it innervate?
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))
What are the obturator nerve roots? What does this nerve innervate?
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)
