Posterior Abdominal Wall

Question 1

Vertebrae

Answer 1

• The bodies of _five lumbar vertebra_e are projecting into the midline of the posterior abdominal area
• The prominence is due to the secondary curvature (forward convexity of the lumbar part of the vertebral column)
• LI to LV

Question 2

How to distinguish lumbar from cervical and thoracic vertebrae ?

Answer 2

Based on their size;

1. much larger than all the others
2. vertebrae bodies are massive and progressively increase in size
3. pedicles are short and stocky
4. transverse process arelong and slender
5. articular processes oriented medially and laterally ( which promotes flexion and extension in this part of the vertabreae column
6. spinous processes are large and stubby

Question 3

Midline boundary and Sacrum

Answer 3

The midline boundary of the posterior abdominal wall, inferior to the lumbar vertebrae consists of;

1. the upper margin of the sacrum

Sacrum

1. is formed by the fussion of the five sacral vertabrea into a single wedge- shaped bony structure
2. is broad superiorly and narrows inferiorly
3. concave anterior surface
4. convex anterior surface

Structures 3 and 4 contain anterior and posterior sacral foramina for the anterior and posterior rami of the spinal nerves to pass through

Question 4

Pelvic Bones

Answer 4

The ilia

1. component of each pelvic bone
2. attach laterally to the sacrum at the sacro-iliac joints
3. upper part of each illium expands outward into a thin wing area (the iliac fossa)

The medial part of this region of each iliac bone, and the related muscles are components of the posterior abdominal wall

Question 5

Ribs

Answer 5

• Superiorly, ribs XI and XIII complete the bony framework of the posterior abdominal wall
• These ribs are unique since;
  
  1. they do not articulate with the sterum or other ribs
  2. they have a single articular facet on their hands
  3. they do not have necks or tubercles

Rib XI

• is posterior to the superior part of the left kidney

Rib XII

1. is posterior to the superior part of both kidneys
2. serves as point of attachment for numerous muscles and ligaments

Question 6

Muscles

Answer 6

Muscles form the

1. medial–> psoas major and minor
2. lateral–> quadratus lumborum
3. iniferior–> iliacus muscle
4. superior–> diaphgram

..boundaries of the posterior abdominal wall

Question 7

Psoas Major

Answer 7

1. covers the anteolateral surface of the bodies of the lumbar vertebrae
2. fills in the space between the vertebral bodies and tranverse processes
3. each of these muscles arises from the bodies of vertebraea TXII and all five are lumbar vertebrae
4. Each muslcle passes inferiolry along the pelvic brim
5. Continues into the anterior thigh under the inguinal ligament to attach to the lesser trochanter of the femur
6. flexes the thigh at the hip joint when the trunk is stabilized and flexes the trunk against gravity when the body is supine
7. It is innervated by anterior rami of nerves L1 to L3

Question 8

Psoas minor

Answer 8

1. can sometimes by abscent
2. lying on the surface of the psoas major
3. slender muscle that arises from vertebrae TXII and LI ( and the innervating vertebrae discs)
4. its long tendon inserts into the pectineal line og the pelvic brim and to the ilioopubic eminence
5. weak flexor of the lumbar vertebral colum
6. innervated by the anterior ramus of nerve L1

Question 9

Vasculature

Answer 9

Abdominal aorta

1. begins at the aortic hiatus of the diaphragm
2. approximately at TXII
3. passes down on the anterior surface of the vertebrae LI to LIV
4. Divides into
   
   1. Right common iliac arteries
   2. Left common iliac arteries
5. The bifurcation can be distinguished by
   
   1. 2.5 cm bellow the umbilicus
   2. a line extending between the highest points of the iliac crest
6. Branches can be classified as
   
   1. visceral
   2. posterior
   3. terminal

Question 10

Visceral Branches

Answer 10

• Supply organs
• Either paired or unpaired

Three unpaired

1. Celiac branch –> abdominal forgut
2. Superior mesenteric –> abdominal midgut
3. Inferior mesenteric–> abdominal hindgut

Paired visceral branches

1. superior suprarenal arteries–> small lateral branches of the andominal aorta arising just above the renal arteries
2. Renal arteries–> lateral branches
3. Testicular/Overian arteries –> anterior branches arise bellow the origin of the renal arteries

Question 11

Posterior branches

Answer 11

• Vessels suplying the diaphgram or body wall
• they consist of
  
  1. Inferior phrenic arteries ( arise directly inferior to the aortic hiatus either from the abdominal aorta or from the celiac trunk, they provide arterial supply to the suprarenal gland
  2. Lumbar arteries;
  3. Median sacral arteries–> just superior to the bifurcation

Question 12

Inferior Vena Cava

Answer 12

1. returns blood from all structures bellow the diaphgram to the right atrium of the heart
2. formed when the two common iliac veins come together at the level of vertebrae LV ( just to the right of the midline)
3. ascends to the right of the abdominal aorta
4. leaves the abdomen by piercing the central tendon of the diapgram at level TVIII

Tributaries ( a vein that empties into a larger vein)

1. common iliac veins
2. lumbar veins
3. renal veins
4. inferior phrenic veins
5. hepatic veins

Lumbar veins are unique;

• not all lumbar veins drain directily into the vena cave

1. fifth lumbar vein; drains into the iliolumbar vein, a tributary of the common iliac vein
2. thrid and fourth lumbar veins; drain into the inferior vena cava
3. first and second empthy on the ascending lumbar veins

( Ascending lumbar veins)

1. long
2. anastomosing venous channels with the azygos and hemi-azygos veins of the thorax
3. if the inferior vena cava is blocked the ascending lumbar veins become important collateral channels between the lower and upper parts of the body

There are no tributaries from the abdominal part of the gastrointestinal tract, the spleen, the pancreas ot the gall bladder because these structures arecomponents of the portal venous system which passes through the liver