The posterior abdominal wall

Question 1

What are the locations of the kidneys?

Answer 1

T12-L3 level.

The right kidney is slightly lower due to the liver.
The kidney is surrounded by “perirenal” or “perinephric” fat.

Renal veins are anterior to renal arteries.

Question 2

What is the external anatomy of the kidney?

Answer 2

Surrounded by fibrous capsule.
The renal artery and renal vein connect to the kidney at the hilum.

The renal pelvis also emerges from the hilum.

Question 3

What is the internal anatomy of the kidney?

Answer 3

Renal pelvis: transmits urine to the ureter. It is formed from several renal calyces which surround the tips of the renal pyramids. These tips are called the renal papilla

The parenchyma of the kidney is divided into the cortex and medulla.
Renal pyramids: triangular segments of the medulla, containing the loop of Henle of the nephrons Renal cortex: contains the renal corpuscles and renal tubules

Question 4

What are renal calculi?

Answer 4

• composed of inorganic salts, caused by dehydration.
• may pass from calyx to pelvis to ureter, becoming a ureteric calculus
• causes severe pain as it progresses through the ureter to the bladder
• pain is referred to as cutaneous nerves supplying the ureter, T11-L2. So pain passes inferiorly from “loin to the groin” as the stone moves inferiorly.

Question 5

What are the narrow parts of the ureter?

Answer 5

• Uretopelvic junction
• Pelvic brim
• Uretero- vesical junction

These are the three locations where the ureters are at their narrowest (where a stone is more likely to become stuck).

Question 6

What is the blood supply to the kidney?

Answer 6

Renal arteries from the aorta.

Left renal vein must cross aorta, below SMA.

Left renal vein has to cross over the aorta to reach the IVC (which is on the right side of your body). The left renal vein is right below the superior mesenteric artery, which can trap it sometimes – NUTCRACKER SYNDROME.

Question 7

What is nutcracker syndrome?

Answer 7

Superior mesenteric artery compresses left renal vein, restricting blood flow from kidney and gonad (as left ovarian and left testicular vein drains at the left renal vein)

Treatment: cut the left renal vein off IVC and move it down

Question 8

What are the adrenal glands?

Answer 8

Right = pyramidal
Left = crescent shaped

Cortex: secretes androgens and corticosteroids in response to stress, and increases blood pressure and heart rate. Mesoderm derived.

Medula: secretes adrenaline and noradrenaline. Neural crest-derived.

Innervation: preganglionic sympathetic fibers from spinal levels T8-L1

Question 9

What is the blood supply to the adrenal gland?

Answer 9

Superior adrenal arteries from inferior phrenic arteries

Middle adrenal arteries from the abdominal aorta near SMA

Inferior adrenal arteries from renal arteries

Question 10

What are the muscles of the posterior abdominal wall?

Answer 10

1. Quadratus lumborum
2. Psoas major
3. Iliacus

Question 11

Quadratus lumborum

Answer 11

Origin: iliac crest

Insertion: transverse processes of the upper first four lumbar vertebrae and the inferior posterior border of the twelfth rib

Function: lateral flexion of the lumbar spine

Innervation: T12, L1-L4

Question 12

Iliacus

Answer 12

Origin: Iliac fossa

Insertion: Lesser trochanter of the femur

Function: Flex hip joint

Innervation: Femoral nerve

Brings femur towards the abdomen

Question 13

Psoas major

Answer 13

Origin: Transverse processes of T12-L4

Insertion: Lesser trochanter of the femur

Function: Flex hip joint

Innervation: L1-L3 via lumbar plexus

Question 14

Psoas minor

Answer 14

Origin: Bodies of T12 and L1

Insertion: Iliopectineal (or iliopubic) eminance

Function: Flex lumbar spine (weak) Innervation: L1

Only present in 40% of people. Useless muscle

Question 15

What is the subcostal nerve?

Answer 15

Subcostal nerve (T12):
The final ‘intercostal’ nerve. It’s called subcostal because it’s not in between ribs

Sensory: region under the umbilicus
Motor: pyramidalis and quadratus lumborum

Question 16

What is the iliohypogastric nerve?

Answer 16

Iliohypogastic n. (L1)
Sensory: Skin over the lateral gluteal region and above the pubis
Motor: Internal oblique and transverses abdominis

Question 17

What is the Ilioinguinal nerve?

Answer 17

Ilioinguinal n. (L1)
Sensory: Skin over upper scrotum or mons pubis/labia major
Motor: Internal oblique and transverses abdominis

Question 18

What is the genitofemoral nerve?

Answer 18

Genitofemoral n. (L1-2):
Sensory: Skin over anterior scrotum or mons pubis
Motor: Cremaster muscle

Note that it passed through psoas major

Question 19

What is the lateral femoral cutaneous nerve?

Answer 19

Lateral femoral cuteneous n. (L2-3)

Sensory: skin of lateral thigh

Question 20

What is the femoral nerve?

Answer 20

Femoral n. (L2-4)

Anterior compartment of Thigh

Question 21

What is the obturator nerve?

Answer 21

Obturator n. (L2-4)

Adductor compartment of thigh

Question 22

What are the 6 branches of the lumbar plexus?

Answer 22

Formed by anterior divisions of L1-L4.
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.
1. Iliohypogastric Nerve – L1 (with contributions from T12)
2. Ilioinguinal Nerve – L1
3. Genitofemoral Nerve - L1-L2
4. Lateral Cutaneous Nerve of the Thigh – L2-L3
5. Obturator Nerve – L2-L4
6. Femoral Nerve – L2-L4

Question 23

Where is the root of the mesentery?

Answer 23

Root of mesentery crosses third part of the duodenum,the aorta, the inferior vena cava, the right ureter and the right gonadal arteries.

Question 24

What is the coeliac plexus?

Answer 24

Coeliac plexus = autonomic plexus consisting of paraaortic ganglia on the anterior surface of the abdominal aorta

Innervation to foregut

Question 25

What are the superior and inferior mesenteric plexus?

Answer 25

The superior mesenteric plexusprovides sympathetic innervation to the cecum, appendix, ascending and transverse colon (near to the left colic flexure).

The inferior mesenteric plexus innervates the colon from the left colic flexure to the rectum. The inferior hypogastric plexus also innervates the rectum.