Kidneys and posterior abdominal wall Flashcards
Where are the kidneys?
Lie outside the peritoneum (extra-peritoneal), behind the peritoneal cavity (retro-peritoneal), one on each side of the upper lumbar vertebrae. They typically extend from T12 to L3, although the right kidney is often situated slightly lower due to the presence of the liver.
What structures surround the kidneys?
Each kidney is embedded in perinephric fat and is covered in renal fascia.
On the medial border of the kidney is the renal hilum, which is where the renal vessels, nerve, lymphatics and ureter enter or leave the kidney.
Posteriorly they lie against the muscles of the posterior abdominal wall, including the diaphragm, psoas major, quadratus lumborum and the transversus abdominis.
Anteriorly the right perinephric fat and kidney is in contact with the liver, duodenum and coils of intestine, whereas the left perinephric fat and kidney is in contact with the stomach, spleen, pancreas and coils of the intestine.
What is the function of the kidneys?
Their main function is to filter and excrete waste products from the blood. They are also responsible for water and electrolyte balance in the body.
What are the external layers of the kidneys?
Renal capsule – tough fibrous capsule.
Perirenal fat – collection of extraperitoneal fat.
Renal fascia (also known as Gerota’s fascia or perirenal fascia) – encloses the kidneys and the suprarenal glands.
Pararenal fat – mainly located on the posterolateral aspect of the kidney.
What are the internal layers of the kidneys?
The renal parenchyma can be divided into two main areas – the outer cortex and inner medulla.
The cortex extends into the medulla, dividing it into triangular shapes – these are known as renal pyramids.
The apex of a renal pyramid is called a renal papilla.
Each renal papilla is associated with a structure known as the minor calyx, which collects urine from the pyramids. Several minor calices merge to form a major calyx.
Urine passes through the major calices into the renal pelvis, a flattened and funnel-shaped structure.
From the renal pelvis, urine drains into the ureter, which transports it to the bladder for storage.
What is the renal hilum?
The medial margin of each kidney is marked by a deep fissure, known as the renal hilum. This acts as a gateway to the kidney – normally the renal vessels and ureter enter/exit the kidney via this structure.
What is the blood supply for the kidneys?
The kidneys are supplied with blood via the renal arteries, which arise directly from the abdominal aorta. The renal artery enters the kidney via the renal hilum. At the hilum level, the renal artery forms an anterior and a posterior division, which carry 75% and 25% of the blood supply to the kidney, respectively. Five segmental arteries originate from these two divisions.
How do the segmental arteries supply the kidneys?
Each segmental artery divides to form interlobar arteries. They are situated either side every renal pyramid.
These interlobar arteries undergo further division to form the arcuate arteries.
At 90 degrees to the arcuate arteries, the interlobular arteries arise.
The interlobular arteries pass through the cortex, dividing one last time to form afferent arterioles.
The afferent arterioles form a capillary network, the glomerulus, where filtration takes place. The capillaries come together to form the efferent arterioles.
In the outer two-thirds of the renal cortex, the efferent arterioles form what is known as a peritubular network, supplying the nephron tubules with oxygen and nutrients. The inner third of the cortex and the medulla are supplied by long, straight arteries called vasa recta.
What is the venous drainage system of the kidneys?
The kidneys are drained of venous blood by the left and right renal veins. They leave the renal hilum anteriorly to the renal arteries, and empty directly into the inferior vena cava.
What is the renal sinus?
The renal sinus is a fatty compartment located within the medial aspect of the kidney. It communicates with the perinephric space. It contains the renal hilum and is bordered by renal parenchyma laterally.
What are the medullary columns?
A medullary extension of the renal cortex in between the renal pyramids. It allows the cortex to be better anchored. Each column consists of lines of blood vessels and urinary tubes and a fibrous material.
What are the suprarenal glands?
AKA Adrenal glands
Close to the upper pole of each kidney lies a suprarenal gland embedded in the perinephric fat. The right suprarenal gland is tetrahedral and lies behind the liver and inferior vena cava. The left suprarenal gland is crescent-shaped and lies behind the stomach and pancreas.
What do the suprarenal glands do?
They secrete steroid and catecholamine hormones directly into the blood.
Are the suprarenal glands intraperitoneal or retroperitoneal?
They are retroperitoneal, with parietal peritoneum covering their anterior surface only.
What is the structure of the suprarenal glands?
The adrenal glands consist of an outer connective tissue capsule, a cortex and a medulla.
How do arteries, veins, nerves and lymphatics enter the suprarenal glands?
Veins and lymphatics leave each gland via the hilum, but arteries and nerves enter the glands at numerous sites.
What does the cortex of the adrenal glands do?
The cortex is yellowish in colour. It secretes two cholesterol derived hormones – corticosteroids and androgens.
What are the layers of the adrenal cortex?
Zona glomerulosa – produces and secretes mineralocorticoids such as aldosterone.
Zona fasciculata – produces and secretes corticosteroids such as cortisol. It also secretes a small amount of androgens.
Zona reticularis – produces and secretes androgens such as dehydroepiandrosterone (DHES). It also secretes a small amount of corticosteroids.
What does the medulla of the adrenal glands do?
The medulla lies in the centre of the gland, and is dark brown in colour. It contains chromaffin cells, which secrete catecholamines (such as adrenaline) into the bloodstream in response to stress.
What is the blood supply for the adrenal glands?
Supplied by the superior, middle and inferior adrenal arteries.
What are the ureters?
The ureters are two thick tubes which act to transport urine from the kidney to the bladder. They arise from the renal pelvis, are approximately 25cm long and are situated bilaterally.
What is the pathway of the ureters?
The ureters descend through the abdomen, along the anterior surface of the psoas major. Here, the ureters are a retroperitoneal structure (located behind the peritoneum).
Upon reaching the bladder wall, the ureters pierce its lateral aspect in an oblique manner. This creates a one way valve, where high intramural pressure collapses the ureters – preventing the back-flow of urine.
What is the arterial and venous supply of the ureters?
The arterial supply to the ureters can be divided into abdominal and pelvic supply:
Abdominal – renal artery, testicular/ovarian artery, and ureteral branches directly from the abdominal aorta
Pelvic – superior and inferior vesical arteries.
Venous drainage is carried out by vessels that correspond to the aforementioned arteries.
What is the nervous supply of the ureters?
Nervous supply to the ureters is delivered via the renal, testicular/ovarian and hypogastric plexuses. Sensory fibres from the ureters enter the spinal cord at T11-L2, with ureteric pain referred to those dermatomal areas.
What is the posterior abdominal wall?
The region behind the abdominal cavity which extends from the attachments of the diaphragm above to the pelvic brim below.
What makes up the posterior abdominal wall?
It consists of the lumbar spine together with the psoas and quadratus lumborum muscles. Structures running along the posterior abdominal wall include the inferior vena cava, the aorta with its associated autonomic plexuses and lymph nodes. The sympathetic trunk continues into the abdomen on either side of the lumbar spine. More laterally the ureters pass down from the kidneys towards the pelvis on the surface of the psoas muscle and the gonadal vessels run down over the ureters to supply the gonads.
What is a Intravenous urogram (IVU)?
A chemical (contrast medium) has been injected into a vein and distributes throughout the body. The chemical has two properties, it absorbs X-rays and it is excreted by the kidney making the urine appear white on an X-ray.
Where does the abdominal aorta bifurcate?
The abdominal aorta bifurcates into the common iliac arteries at L4 (the surface marking of the aortic bifurcation is the umbilicus).
What is the internal iliac artery?
The internal iliac artery is the major artery of the pelvis. It originates at the bifurcation of the common iliac artery into its internal and external branches at L5-S1. At the superior border of the greater sciatic foramen, it divides into anterior and posterior trunks.
What does the anterior trunk of the internal iliac artery give rise to?
Obturator artery - supplies the muscles of the thigh’s adductor region
Umbilical artery - supplies the superior aspect of the urinary bladder
Inferior vesical artery - supplies inferior bladder, prostate gland, seminal vesicles
Vaginal artery - additional branches to the inferior bladder and rectum
Uterine artery - travels within the cardinal ligament along the uterus
Middle rectal artery - supplies the distal part of the rectum
Internal pudendal artery - major supply of perineum
Inferior gluteal artery - supplies gluteal muscles and the hip joint
What does the posterior trunk of the internal iliac artery give rise to?
The posterior trunk gives rise to arteries that supply the lower posterior abdominal wall, posterior pelvic wall and the gluteal region which are made up of 3 branches:
Iliolumbar artery - The lumbar branch supplies psoas major, quadratus lumborum and the posterior abdominal wall. The iliac branch supplies the muscles and bone around the iliac fossa.
Lateral sacral arteries (superior and inferior) - supply structures in the sacral canal, and the skin and muscle posterior to the sacrum.
Superior gluteal artery - major blood supply to the muscles and skin of the gluteal region.
What are the gonadal arteries?
Gonadal arteries - the ovarian artery is the major gonadal artery in the female. It arises from the abdominal aorta and descends towards the pelvis and branches into an ovarian branch and tubal branches.
What is the median sacral artery?
Median sacral artery - originates from the abdominal aorta where it bifurcates into the common iliac arteries. Contributes to the arterial supply of the L4 and L5 vertebrae, sacrum and the coccyx.
What is the superior rectal artery?
Superior rectal artery - terminal continuation of the inferior mesenteric artery. It gives rise to branches that supply the rectum.
What is the external iliac vein?
The external iliac vein is a continuation of the femoral vein (the major vessel draining the lower limb). It ascends along the medial aspect of the external iliac artery, before joining with the internal iliac vein to form the common iliac vein. During its short course, the external iliac vein receives the inferior epigastric and deep circumflex iliac veins.
What is the internal iliac vein?
The internal iliac vein is responsible for the majority of pelvic venous drainage, and receives numerous tributaries from veins that drain the pelvic region.
What veins drain into the internal iliac vein?
Superior and inferior gluteal veins – drains the buttock and upper thigh.
Internal pudendal vein – drains the reproductive organs and part of the rectum (via the inferior rectal vein).
Obturator vein
Lateral sacral veins – drains part of the sacrum.
Middle rectal vein – drains the bladder, prostate (in males only), and part of the rectum.
Vesical veins – drains the urinary bladder via the vesical venous plexus.
Uterine and vaginal veins – drain the female reproductive organs via the vaginal and uterine venous plexuses.