Urinary System Lecture Notes, Lecture notes of Anatomy

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The

Urinary

System

Urinary system consists of six organs:

two kidneys, two ureters, urinary bladder, and urethra

Location of the

Kidney

• (^) Retroperitoneal
• (^) Located at level of T12-L
• (^) Protected by ribs 11 and 12
• (^) Right kidney slightly lower than left because of liver

Anatomy of the Kidney

Shape & size

• (^) Size of bar of soap
• (^) Lateral surface is convex
• (^) Medial surface is concave
  • (^) Hilum: indented area that receives renal nerves, vessels, and ureter Three protective CT coverings Renal fascia (outer) Binds kidney to abdominal wall Perirenal fat (middle) Cushions and holds it in place Fibrous capsule (inner) Encloses kidney Protects from infection & trauma

Anatomy (cont.)

• (^) Renal Cortex
  • (^) Filtration of blood to form urine
• (^) Renal Medulla
  • (^) Renal pyramids
  • (^) Renal papilla
  • (^) Collection of urine
• (^) Lobe of kidney
  • (^) One pyramid & its overlying cortex
• (^) Minor calyx
  • (^) Collects urine from papilla of pyramid
• (^) Major calyces
  • (^) Convergence of 2-3 minor calyce
• (^) Renal pelvis
  • (^) Convergence of 2-3 major calyce
• (^) Ureter
  • (^) Tubular continuation of pelvis
  • (^) Drains urine down to bladder

The Nephron

• (^) Each kidney has about

1.2 million nephrons

• (^) Each composed of two

principal parts

• (^) Renal corpuscle: filters

the blood plasma

• (^) Renal tubule: long

coiled tube that converts

the filtrate into urine

Nephron: Renal Corpuscle

• (^) Renal corpuscle consists of glomerulus and two-layered

glomerular (Bowman) capsule that encloses glomerulus

• (^) Glomerular filtrate collects in capsular space, flows into proximal

convoluted tubule. Note the vascular and urinary poles. Note the afferent arteriole is larger than the efferent arteriole. Why would that be?

Vascular Pole

Urinary Pole

Glomerulus

• (^) Enlarged, smooth muscle cells of arteriole
• (^) Act as mechanoreceptors that sense blood pressure

Efferent arteriole

Afferent arteriole

Glomerulus

PCT

Renal Physiology

• (^) The 3 basic functions performed by nephrons and

collecting ducts are:

• (^) Glomerular filtration - pressure forces filtration of

waste-laden blood in the glomerulus. The glomerular filtration rate (GFR) is the amount of filtrate formed in

all the renal corpuscles of both kidneys each minute.

(180 L/day in males, 150 L/day in females)

• (^) Tubular reabsorption – the process of returning

important substances from the filtrate back to the body.

• (^) Tubular secretion – the movement of waste materials

from the body to the filtrate.

Countercurrent Multiplier

Osmotic Gradient in the Renal

Medulla

Pelvis

Ureter

Kidney

function

in

context:

Diabete

s

• (^) Diabetics may have many times higher than normal (~90 mg/ ml) levels of blood glucose
• (^) In patients with diabetes mellitus, urine composition and quantity are abnormal. Hyperglycemia leads to: - (^) Glycosuria – glucose lost in urine - (^) Polyuria – excess urine release, followed by dehydration
• (^) Why does diabetes result in these symptoms?

Why

does

diabetes

lead to

polyuria

• (^) Principle cells of collecting ducts do not have glucose transporters
• (^) The excess glucose becomes an “osmotic diuretic” – a solute in the filtrate that is not reabsorbed, and therefore carries water with it in the outgoing urine
• (^) Polyuria occurs, resulting in dehydration and decreased blood volume in the diabetic patient