The Kidneys and the Ureters
Advertisements help pay for this website. Thank you for
your support.
Urogenital
diaphragm and ischiorectal fossa | Main Anatomy
Index | The suprarenal glands
Last updated 30 March 2006
The Kidneys
- The kidneys (L. renes) lie in the paravertebral gutters,
at the level of L12 to L3 vertebrae.
- Their long axes are almost parallel with the axis of the body.
- The ureter runs inferiorly from each kidney and passes over the pelvic brim at the bifurcation of
the common iliac artery.
- This runs along the lateral wall of the pelvis and enters the urinary bladder.
- The kidneys' functions are:
- The removal of excess water, salts
and products of protein metabolism;
- The maintenance of pH;
- Production and release of erythopoietin, which controls
blood cell production;
- Synthesis and release of renin to influence blood
pressure;
- And the production of 1,25-hydroxycholecalciferol
(activated for of vitamin D) for control of calcium metabolism.
Position, Form,
and Size of the Kidneys
Click here for a diagram of the position of the
kidney from the posterior aspect.
- The superior parts of the kidneys are protected by the
thoracic cage and are tilted so that their superior poles
are nearer to the median plane than their inferior poles.
- The right kidney lies at a slightly lower level than
the left one.
- This is due to the large size of the right lobe
of the liver.
- Each kidney has anterior and posterior
surfaces, medial and lateral
margins (borders), and superior and inferior poles.
- The lateral margin is convex.
- The medial margin is indented
or concave where the renal sinus
and renal pelvis are located.
- 10-11 cm in length;
- 5-6 cm in width;
- 2.5-3 cm in thickness;
- They weigh about 135-150 grams;
- The left kidney is often slightly longer than the right
one.
- Each kidney is ovoid in outline.
- Its indented medial margin gives it a somewhat bean-shaped appearance.
- At this concave part of each kidney is a vertical cleft, the renal hilum
(hilus).
- Here, the renal artery enters and the renal
vein and renal pelvis leave the kidney.
- The hilum leads into a space within the kidney called
the renal sinus, which is about 2.5
cm deep.
- The renal sinus is occupied by the renal pelvis, renal calices, renal vessels
and nerves, and varying amounts of fat.
- From anterior to posterior are the:
- Renal vein
- Renal artery
- Renal pelvis
Surface
Anatomy and Markings of the Kidneys
- In thin adults with poorly
developed abdominal muscles, the inferior pole of the
right kidney is usually palpable in the right lateral
region.
- It is a firm, smooth, somewhat rounded mass that descends during inspiration.
- The normal left kidney is not
usually palpable.
- The levels of the kidneys change during respiration and with changes in posture.
- Each kidney moves about 3 cm in a vertical
direction during the movements of the diaphragm that occurs with deep breathing.
- The hilum of the left kidney
lies in the transpyloric plane, about 5
cm from the median plane.
- This plane cuts through the superior part of the right kidney.
- From the posterior aspect of the kidney (important for
surgery), the inferior pole of the right
kidney is about a fingerbreadth superior to
the iliac crest and that its superior
pole is superior to the 12th rib.
Gross Structure of
the Kidneys
Click here for a diagram of the gross structure of
the kidneys.
The Fibrous Capsule
- Each kidney is invested in a strong, fibrous
capsule.
- It passes over the lips of the hilum to line the renal sinus and become continuous
with the walls of the calices.
- The kidney and its capsule are surrounded by pararenal fat,
but it is sparse on its anterior surface.
- This fat is less dense and thus an outline of the kidney is
usually visible in radiographs, CTs and MRIs.
The Renal Pelvis
- This is continuous inferiorly with the ureter.
- It is surrounded by fat, vessels
and nerves in the renal sinus.
- The word pelvis is derived from the Greek word pyelos, meaning basin.
- Within the renal sinus, the renal pelvis usually
divides into two wide, cup-shaped
major calices (G. flower cups).
- Each major calyx (calix) is subdivided into 7 to 14 minor calices.
- The urine empties into a minor calyx from the collecting tubules that pierce the tip of the renal papilla obliquely.
- It then passes through the major calyx, renal pelvis, and the ureter
to enter the urinary bladder.
Renal Fascia and
Renal Fat
- Each kidney, invested by the fibrous renal capsule,
is also embedded in a substantial mass of perirenal fat
that constitutes the fatty renal capsule.
- Very little fat lies anterior to the kidney.
- The fatty renal capsule is in turn covered by fibroareolar tissue called the renal
fascia.
- This fascia encloses the kidney, its surrounding
fibrous and fatty capsules, and the suprarenal
(adrenal) glands.
- These covering help to maintain the position of these organs.
- Superiorly, the renal fascia is continuous
with the fascia on the inferior surface of the diaphragm
(the diaphragmatic fascia).
- Medially, the anterior layers of the fascia on the right and left sides blend
with each other anterior to the abdominal aorta and inferior vena cava.
- The posterior layer of renal fascia fuses
medially with the fascia over the psoas major muscle.
- The layers of renal fascia are loosely united inferiorly
and may easily be separated.
- The encasement of the kidney in fat is an important
factor in anchoring it in position.
Relations of the Kidneys (Ashwell)
- For the anterior relations of the left
kidney, it is composed of 7 "S":
- Suprarenal;
- Splenic;
- Stomach (gastric part);
- Splenic vessels;
- Sweetbread (the pancreas);
- Small intestine (duodenum, ileum and jejunum);
- Splenic flexure (or left colic flexure).
Blood Supply of the
Kidney
Renal Arteries
Click here to go to the renal arteries
under "The Blood Vessels of the Abdomen and Pelvis."
- This arises from the aorta below the level of the superior mesenteric artery.
- Each renal artery gives off one or more inferior suprarenal
arteries and branches that supply the perirenal tissue,
renal capsule, pelvis
and the proximal part of the ureter.
- Accessory renal arteries are common (30% of
individuals).
- They usually arise above or below the main renal artery and follow the hilum.
Segmental Arteries
- Near the hilum each artery divides into anterior and posterior divisions, which in turn divide into segmental arteries.
- These supply the 5 renal vascular segments (apical,
superior (anterior), inferior, middle (anterior) and posterior).
- Each vascular segment is supplied by end arteries,
i.e., there are no anastomoses.
- The initial branches of the segmental arteries are lobar,
usually one to each pyramid.
- However, before entry they subdivide into 2 or 3 interlobar arteries.
- At the junction of the cortex and medulla,
each interlobar artery divides into arcuate
arteries.
- These diverge at right angles.
- Interlobular arteries diverge from the arcuate arteries to ascend into the
cortex, to give rise to the glomerular arteries.
Venous Drainage of
the Kidneys
Click here
to go to the "Blood Vessels of the Abdomen and Pelvis."
- The renal veins drain into the IVC.
- The left renal vein is longer than the right renal vein and receives the left
suprarenal veins and left gonadal vein.
- On the right, these drain directly into the IVC.
Renal Innervation
Click here to go
to "The Nerves and Lymphatics of the Abdomen and Pelvis."
- The coeliac ganglion and plexus;
- The aorticorenal ganglion;
- The lower thoracic splanchnic nerves;
- The 1st lumbar splanchnic nerve;
- And the aortic
plexus.
- The plexus usually
continues into the kidney around the renal arteries.
- Most renal nerves are vasomotor.
- Sensory nerves pass back to the CNS with the thoracic splanchnic nerves.
- The renal plexus gives rise to the ureteric and gonadal plexuses.
Lymphatic Drainage
of the Kidneys
- This is to the lumbar nodes.
The Ureters
- These are thick-walled, expandable
muscular ducts with a narrow lumen.
- They carry urine from the kidneys
to the urinary bladder.
- As urine passes along the ureters, peristaltic waves occur
in their walls.
- Each ureter is continuous above with the funnel-shaped renal pelvis.
The Abdominal Ureter
- The abdominal part of the ureter is about 12.5 cm long and 5 mm wide.
- This closely adheres to the parietal peritoneum and is retroperitoneal
throughout its entire course.
- It descends almost vertically, anterior
to the psoas major muscle.
- As the right ureter descends, it is closely related to
the IVC, the lumbar lymph nodes
and the sympathetic trunk.
- The ureter crosses the brim of the pelvis and the external iliac
artery, just beyond the bifurcation of the common iliac artery.
The Pelvic Ureter
- They continue to a point about 1.5 cm superior to the ischial spines.
- Each ureter then curves anteromedially, superior to the levator
ani muscle, where it is closely adherent to the peritoneum.
- The ureters pass obliquely through the bladder wall.
- When the bladder distends, the ureters are compressed
and flattened, thus preventing regurgitation of urine and
the chance of ascending infections.
- The narrowest parts of the bladder are at the pelviureteric region, when it begins.
- It is also narrow along the intramural course in the bladder.
- Furthermore, the ureter may kink at the pelvic brim.
- At these sites, there is the likelihood of impaction of ureteric
stones.
In the Male
- In the male, the only structure that passes between the
ureter and the peritoneum is
the ductus deferens.
- The ureter lies lateral to this duct and enters the posterosuperior angle of the bladder,
just superior to the seminal vesicle.
In the Female
- In the female, the ureter descends on the lateral wall
of the pelvis minor.
- Here it forms the posterior boundary of the ovarian fossa.
- As it descends, the ureter passes medial to the origin
of the uterine artery.
- It continues to the level of the ischial spine.
- Here it is crosses superiorly by the uterine
artery.
- It passes close to the lateral part of the fornix of the vagina, especially on the left
side.
- Like in the male, the ureter enters the bladder at the posterosuperior angle.
Blood Supply of the
Ureters
Click here to go to "The Blood
Supply of the Abdomen and Pelvis."
- The blood supply is from the following arteries:
- The renal;
- The abdominal aorta;
- The gonadal;
- The common iliac;
- The internal iliac;
- And the vesical and uterine
arteries.
- Depending on the part of the ureter, there is a different arterial supply.
- There are good longitudinal anastomoses between these
vessels.
- The venous drainage follows a similar pattern to
arterial supply.
Innervation of the
Ureters
Click here to go to "The
Innervation and Lymphatic Supply to the Abdomen and Pelvis."
- This is through the ureteric plexus, which is derived
from the renal, aortic, superior and inferior hypogastric
plexuses.
- Ureteric supply is these is derived from-
- Sympathetic: T10-12, L1;
- Parasympathetic: S2-4.
- Afferent pain fibres pass back to T11,
T12 and L1.
- Ureteric pain is severe and spasmodic
(renal colic) and is referred to the groin, labia majora, scrotum and anterior thigh.