URINARY SYSTEMKIDNEYS AND URETERS

OBJECTIVES

• 1- Describe the normal site, size, shape and position of the kidney

• 2- Delineate the surface anatomy of the kidney• 3- Describe the facsia surrounding the kidney• 4- Describe the blood supply of the kidney• 5- Describe the beginning termination, and parts of the

ureter• 6- Discuss the normal sites of ureteric constrictions

Organs of the Urinary System

Copyright © 2008 Pearson Education, Inc., publishing as

Benjamin Cummings

• Organs of theUrinary system• Kidneys• Ureters• Urinary bladder• Urethra

Figure 23.1a

Kidneys

Location and External Anatomy of Kidneys

• Bean shaped organs• Located retroperitoneally• Lateral to T12–L3 vertebrae • R kidney lower than L (due to R lobe of liver)• kidney levels change during respiration and postural

changes• Average kidney• 12 cm tall, 6 cm wide, 3 cm thick• tilted: superior poles are closer to midline than inferior

• Hilum• On concave surface • Vessels, lymphatics and nerves enter and exit

• Renal capsule surrounds the kidney

Copyright © 2008 Pearson Education, Inc., publishing as

Benjamin Cummings

Relationship of the Kidneys to Vertebra and Ribs

Figure 23.1b

Renal fascia and fat

1. renal fascia (outer)• Extraperitoneal fascia, attaches kidney to posterior

abdominal wall – flexible, allows kidney to move with respiration

• covered by a layer of fat (Pararenal or paranephric)• The suprarenal glands are included inside this layer

2. perirenal fat (middle layer)• protective cushion• Completely surrounds the kidney

3. renal capsule (innermost)• layer of collagen fibers - barrier against trauma,

infection etc.• kidney hangs suspended by collagen fibers and

packed in soft cushion of adipose tissue

Internal anatomy

outer cortex: pale, inner medulla

• 6-18 conical renal pyramids

• apex - renal papilla projects into the renal sinus

renal columns • extensions from cortex

inward to renal sinus between adjacent renal pyramids

Internal anatomy

• ureter enters renal sinus, it expands to form a chamber called - renal pelvis

• pelvis branches to form 2-3 major calyces

• branch further to form 6-8 minor calyces

• Each minor calyx surrounds the papilla of a renal pyramid

• ducts within papilla connect to wall of the calyx and discharge urine produced in the cortex and medulla

• Urine passes through the calyces into the ureter

•Blood Supply• Single renal artery arises

just inferior to the origin of the superior mesenteric artery between vertebrae LI and LII

• 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.

• Extra hilar arteries???

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

• 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.

Blood supply of the kidney:

Renal arteries from abdominal aorta enter hilum and branch:

1. Interlobar arteries - pass through renal columns and reach junction between medulla and cortex

2. Arcuate arteries run parallel with the base of the pyramids

3. Interlobular arteries move up into the cortex and branch to form the afferent arteriole

The peritubular capillaries unite to form the interlobular veins, arcuate vein, interlobar vein, renal vein

The renal vein exits at hilus and joins the IVC

Nephron

= Functional unit of the kidney, ~ 1 million nephrons per kidney!

Tubular components:

1. Glomerular (Bowman’s) capsule –2. Proximal convoluted tubule – 3. Loop of Henle - hair-pin loop• thin descending limb, thick ascending limb

4. Distal convoluted tubule - last section • specialized region - Juxta glomerular apparatus

Distal convoluted tubule opens into the collecting system collecting ducts papillary ducts

minor calyx…

Vascular components of nephron

Made up of blood vessels:

1. Glomerulus - network of capillaries within Bowman’s capsule

2. Afferent arteriole - leading into glomerulus

3. Efferent arteriole - leading out of glomerulus

4. Peritubular capillaries - surrounding tubules

5. Vasa recta - specialised loops of blood vessels around long Loop of Henle (juxtamedullary nephrons)

Nephrons: 85% are cortical, 15% are juxtamedullary Martini p957

Ureters

Ureters Pyelogram (colour-enhanced)

• tubes that transport urine from renal pelvis to bladder

• 20-30 cm long

• Run from the renal pelves, pass over the pelvic brim at the bifurcation of the common iliac arteries.

• Then along the lateral wall of the pelvis, to enter the UB

• Sites of constriction of the ureters:1- At the junction of the ureter and the renal pelvis ( Ureteropelvic junction)

2- Where the ureters cross the common iliac arteries at the pelvic brim

3- during their entery through the wall of the urinary bladder.

Stones become lodged in these sites

•THANK YOU