Human Anatomy: Kidneys and Ureters (Lecture Notes)

HUMAN ANATOMY
KIDNEYS AND URETERS
(Lecture Notes)

Necdet Ersöz
Gazi University Medical School

Kidneys

ü  Bean-shaped

ü  Reddish brown

ü  Retroperitoneal

ü  Lie in the extraperitoneal connective tissue, lateral to the vertebral column.

ü  Extend from approximately vertebra TXII superiorly to vertebra LIII inferiorly.

ü  The right kidney is lower than the left kidney of its relationship with the liver.

ü  Right kidney TXII – LIII

ü  Left kidney TXI – LII

ü  Largely undercover of the costal margin.

ü  With the contraction of the diaphragm (respiration), they move downward in a vertical direction by as much as 2.5 cm

ü  Excrete most of the waste products of metabolism

ü  A major role in controlling the water and electrolyte balance within the body and in maintaining the acid-base balance of the blood.

ü  The waste product is urine.

ü  On the medial concave border is a vertical slit that is bounded by thick lips of renal substance: HILUM.

ü  The Hilum extends into a large cavity: RENAL SINUS

ü  The Hilum transmits (from the front backward) : renal vein, two branches of the renal artery, ureter, the third branch of the renal artery, and also lymph vessels and sympathetic fibers.

Coverings of Kidney

ü  Fibrous capsule surrounds the kidney and is closely applied to its outer surface.

ü  Perirenal fat covers the fibrous capsule.

ü  Renal fascia is a condensation of connective tissue, lies outside the perirenal fat, encloses the kidneys and suprarenal glands, is continuous laterally with the fascia transversalis.

ü  Pararenal fat lies external to renal fascia, forms part of the retroperitoneal fat.

ü  At the lateral margins of each kidney, the anterior and posterior layers of the renal fascia fuse.

ü  This fused layer may connect with the transversalis fascia on the lateral abdominal wall.

ü  Inferiorly the anterior and posterior layers of the renal fascia enclose the ureters.

ü  Medially the anterior layer of the renal fascia continues over the vessels in the hilum and fuses with the connective tissue associated with the abdominal aorta and the inferior vena cava.

ü  Paranephric fat (pararenal fat) completes the fat and fascias associated with the kidney, accumulates posterior and posterolateral to each kidney.

Relations to Other Structures

Right Kidney (Anterior)

ü  Suprarenal gland

ü  Liver

ü  Second part of the duodenum

ü  Right colic flexure

Left Kidney (Anterior)

ü  Suprarenal gland

ü  Spleen

ü  Stomach

ü  Pancreas

ü  Left colic flexure

ü  Beginning of the descending colon

ü  Coils of jejunum

Righ Kidney (Posterior)

ü  Diaphragm

ü  Costodiaphragmatic recess of the pleura

ü  XII. Rib

ü  Psoas and quadratus lumborum muscles

ü  Transversus abdominis muscle

ü  The subcostal nerve

ü  The iliohypogastric nerve

ü  The ilioinguinal nerve (these nerves run downward and laterally)

Left Kidney (Posterior)

ü  Diaphragm

ü  Costodiaphragmatic recess of the pleura

ü  XI. and XII. Ribs

ü  Psoas and quadratus lumborum muscles

ü  Transversus abdominis muscle

ü  The subcostal nerve

ü  The iliohypogastric nerve

ü  The ilioinguinal nerve (These nerves run downward and laterally)

Right Kidney (Posterior)

ü  Diaphragm

ü  Costodiaphragmatic recess of the pleura

ü  XII. Rib

ü  Psoas and quadratus lumborum muscles

ü  Transversus abdominis muscle

ü  The subcostal nerve

ü  The iliohypogastric nerve

ü  The ilioinguinal nerve (These nerves run downward and laterally)

Kidney Location

ü  Lateral to vertebral column high on body wall, under floating ribs in retroperitoneal position.

Renal Structure

ü  Kidney has a smooth anterior and posterior surface covered by a fibrous capsule, which is easily removable.

ü  The Hilum is continuous with the renal sinus.

ü  Perinephric fat continues into the hilum and sinus and surrounds all structures.

ü  A dark brown is outer cortex

ü  A light brown is inner medulla

ü  The renal cortex is a continuous band of pale tissue that completely surrounds the renal medulla

ü  Extension of the renal cortex (the renal columns) project into the inner aspect of the kidney, dividing the renal medulla into about a dozen renal pyramids (triangular shaped tissue).

ü  Base of medulla oriented toward the cortex.

ü  Apex of medulla is renal papilla, projecting medially.

ü  Extending from the bases of the renal pyramids into the cortex are striations: medullary rays.

Renal Sinus

ü  The space within the hilum.

ü  Contains the upper expanded end of the ureter (the funnel-shaped superior end of the ureter): renal pelvis

ü  Renal pelvis divides into two or three major calyces.

ü  Major calyces divide into two or three minor calyces.

ü  Each minor calyx is intended by the apex of the renal pyramid: renal papilla

Blood Supply

Arteries

ü  Renal artery from the aorta at the level of L1 – L2 vertebra

ü  The left renal artery usually arises a little higher than the right, and the right renal artery is longer and passes posterior to the inferior vena cava.

ü  Renal artery divides into five segmental arteries then enters the hilum of the kidney, 4 in front, 1 behind the renal pelvis.

ü  Are distributed to different segments or areas of the kidneys.

ü  Five arterial segments have been identified.

ü  The apical segment occupies the anteromedial region of the superior pole.

ü  The superior (anterior) segment includes the rest of the superior pole and the central anterosuperior region.

ü  The inferior segment encompasses the whole lower pole.

ü  The middle (anterior) segment lies between the anterior and inferior segments.

ü  The posterior segment includes the whole posterior region between the apical and inferior segments.

ü  From each segmental artery, lobar arteries arise (one for each renal pyramid).

ü  Before entering the renal substance, each lobar artery gives off 2 or 3 interlobar arteries.

ü  Interlobar arteries run toward the cortex on each side of the renal pyramid.

ü  At the junction of the cortex and the medulla, gives off the arcuate arteries. Arcuate arteries arch over the bases of the pyramids, give off several interlobular arteries (that ascend in the cortex).

Anatomy of the Nephron

ü  Glomerulus

ü  Proximal Tubule

ü  Loop of Henle

ü  Distal Tubule

Nephron

ü  Renal corpuscle: only in cortex (tuft of capillaries called glomerulus, surrounded by cup-shaped, hollow glomerular capsule)

Uriniferous tubule is the main structural and functional unit.

ü  To left is a single, uriniferous tubule.

ü  More than a million of these tubules act together to form the urine.

ü  Three main mechanisms: glomerular filtration, tubular reabsorption, and tubular secretion.

ü  Two major parts: a urine-forming nephron, a collecting duct which concentrates urine by removing water from it.

ü  Multiple renal veins contribute to the formation of the left and right renal veins, both of which are anterior to the renal arteries.

ü  Importantly, the longer left renal vein crosses the midline anterior to the abdominal aorta and posterior to the superior mesenteric artery and can be compressed by an aneurysm in either of these two vessels.

ü  The lymphatic drainage of each kidney is to the lateral aortic lymph nodes around the origin of the renal artery.

Ureters

ü  Muscular tubes

ü  Extend from the kidneys to posterior surface of the urinary bladder

ü  The urine is propelled along the ureter by peristaltic contractions of the muscle coat, assisted by the filtration pressure of the glomeruli.

ü  Each ureter is approximately 25 cm long.

ü  Have three constrictions along its course: where the renal pelvis joins the ureter, where it is kinked as it crosses the pelvic brim, and where it pierces the bladder wall)

ü  The renal pelvis narrows as it passes inferiorly through the hilum of the kidney and becomes continuous with the ureter at the ureteropelvic junction.

ü  Inferior to this junction, the ureters descend retroperitoneally on the medial aspect of the psoas major muscle. At the pelvic brim, the ureters cross either the end of the common iliac or the beginning of the external iliac arteries, enter the pelvic cavity.

Relations

Right Ureter

ü  Anteriorly duodenum, terminal part of the ileum, right colic and ileocolic vessels, right testicular or ovarian vessels, root of the mesentery of the small intestine.

ü  Posteriorly right psoas muscle which separates it from the lumbar transverse processes, bifurcation of the right common iliac artery.

Left Ureter

ü  Anteriorly sigmoid colon, sigmoid mesocolon, left colic vessels, left testicular or ovarian vessels.

ü  Posteriorly left psoas muscle which separates it from the lumbar transverse processes, bifurcation of the left common iliac artery.

The inferior mesenteric vein lies along the medial side of the left ureter.

ü  As the ureters cross the bifurcation of the common iliac artery or the beginning of the external iliac artery they pass over the pelvic brim, thus leaving the abdomen and entering the lesser pelvis.

ü  The pelvic parts of the ureters run on the lateral walls of the pelvis, parallel to the anterior margin of the greater sciatic notch, between the parietal pelvic peritoneum and the internal iliac arteries.

ü  Opposite the ischial spine, they curve anteromedially, superior to the levator ani, and enter the urinary bladder.

ü  The inferior ends of the ureters are surrounded by the visceral venous plexus.

ü  The ureters pass obliquely through the muscular wall of the urinary bladder in an inferomedial direction, entering the outer surface of the bladder approximately 5 cm apart, but their internal openings into the lumen of the empty bladder are separated by only half that distance.

ü  This obliquely passage through the bladder wall forms a one-way “flap valve”, the internal pressure of the filling bladder causing the intramural passage to collapse. In addition, contractions of the bladder musculature act as a sphincter preventing the reflux of urine into the ureters when the bladder contracts, increasing internal pressure during micturition.

ü  Urine is transported down the ureters by means of peristaltic contractions, a few drops being transported at intervals of 12-20 sec.

ü  In males, the only structure that passes between the ureter and the peritoneum is the ductus deferens, it crosses the ureter within the ureteric fold of peritoneum.

ü  The ureter lies posterolateral to the ductus deferens and enters the posterosuperior angle of the bladder, just superior to the seminal gland.

ü  It then passes close to the lateral part of the fornix of the vagina and enters the posterosuperior angle of the bladder.

Note: These notes are taken from Gazi University Faculty of Medicine Prof. Dr. Rabet GOZIL’s anatomy lectures.