Three Functions of the Urinary System

1. Excretion
2. Elimination
3. Homeostatic
   Regulation

Excretion

• the removal of organic wastes from body fluids

Elimination

• Discharge of waste products into the environment

Homeostatic Regulation

• Of blood plasma volume and solute concentration

Organs of the Urinary System

• kidneys (2)
• ureters (2)
• urinary bladder
• urethra

Kidneys (2)

• perform the excretory functions of the urinary system
• produces urine located on either side of the vertebral
  column
• left kidney lies slightly superior to the right kidney
  because of liver

Urine

• fluid that contains ions, water, and small soluble
  compunds

Urinary Tract

• organs that eliminate urine
  
  1. ureters (2)
  2. Urinary Bladder
  3. Urethra

Ureters

paired tubes

Urinary Bladder

muscular sac for temporary storage of urine

Urethra

exit tube

Urination

• process of eliminating urine
• the muscular urinary
  bladder contracts and forces urine through the urethra

Homeostatic Functions of the Urinary System

• Regulates blood volume & blood pressure
  
  • by adjusting the volume of water lost in urine
    releases erythropoietin and renin
• Regulates plasma concentrations of sodium, potassium, and
  chloride
  • by controlling quantities lost in
    urine the kidneys
  • also control calcium ion levels through
    the synthesis of calcitriol
• Helps stabilize blood pH
  • by controlling
    loss of hydrogen ions and bicarbonate ions in urine
    
    
• Conserves valuable nutrients
  • by preventing
    their loss in urine while removing organic wastes
  • especially (nitrogenous wastes) urea and uric acid
• Assists the liver in detoxifying
  poisons

The left kidney lies slightly ___________ to the right kidney.

superior

The superior surface of each kidney is capped by an ______ ______.

adrenal gland

Three Concentric Layers of Connective Tissue that Protect &
Stabilize Each Kidney

1. Fibrous Capsule
2. Perinephric Fat
3. Renal
   Fascia

Fibrous Capsule

layer of collagen fibers covers outer surface of the
entire organ

Perinephric Fat

thick layer of adipose tissue that surrounds the fibrous
capsule

Renal Fascia

a dense, fibrous outer layer that anchors the kidney to
surrounding structures

Typical Adult Kidney

• reddish brown
• 10 cm long
• 5.5 cm wide
• 3 cm thick
• weighs about 150 g

Hilum

• medial indentation point of entry for the renal artery
  and renal nerves

• point of exit for renal vein and
  ureter

Renal Sinus

an internal cavity within the kidney lined by fibrous
renal capsule

Renal Cortex

• superficial portion of the kidney, in contact with the renal
  capsule
• reddish-brown and granular

Renal Medulla

consists of 6 to 18 triangular structures

Renal Pyramids

• 6 to 18 distinct triangular structures in renal medulla
• base abuts cortex tip (renal papilla projects into
  renal sinus

Renal Columns

• bands of cortical tissue separates adjacent renal pyramids
  extend into medulla granular tissue

Renal Lobe

• consists of:
  • renal pyramid overlying area of
    renal cortex
  • adjacent tissues of renal columns
  • produces urine

Urine is produced in the ____ _____.

kidney lobes

Renal Papilla

ducts discharge urine into minor calyx

Minor Calyx

cup shaped drain

Major Calyx

formed by four or five minor calyces

Renal Pelvis

• formed by 2 or 3 major calyces
• funnel shaped chamber
• fills most of the renal sinus
• connected to
  ureters, which drains kidneys

Nephrons

• microscopic, tubular structures in cortex of each renal love
• where urine production begins

Blood Supply to Kidneys

• kidneys receive 20-25% of the total cardiac output
• 1200 mL of blood flow through the kidneys each minute

Kidney receives blood through the _______ _______.

renal artery

Segmental Arteries

• recieves blood from the renal artery
• divides into interlobular arteries

Interlobular Arteries

• radiate outward through the renal columns between the renal pyramids
• supply blood to the arcuate arteries

Arcuate Arteries

• arch along the boundary between the cortex and medulla of the kidney

Afferent Arterioles

• delivers blood to the capillaries supplying individual nephrons

Cortical Radiate Veins/Interlobular Veins

• deliver blood to the arcuate veins
• empty into interlobar veins

Interlobar Veins

• drain directly into renal vein

Renal Nerves

• innervate the kidneys and ureters
• enters each kidney at the hilum
• follows the branches of the renal arteries to reach individual nephrons

Sympathetic Innervation

1. Adjusts rates of urine formation
   • by changing blood flow and blood pressure at the nephron
2. Stimulates the release of renin
   • which restricts water and salt loss in urine by stimulation reabsorption by the nephron

The Nephron

• consists of:
  1. renal tubule
  2. renal corpuscle

Renal Corpuscle

• a spherical structure consisting of:
  1. glomerular (Bowman's) capsule
     • cup shaped chamber
  2. glomerulus
     • a capillary network
• squamous cells

Glomerular (Bowman's) Capsule

• cup shaped chamber

Renal Tubule

• begins at renal corpuscle
• long tubular passageway

Glomerulus

• consists of 50 intertwined capillaries
• projects into the glomerular (Bowman's) capsule
• blood leaves the glomerulus in an efferent arteriole

Efferent Arteriole

• flows into a network of capillaries called peritubular capillaries
• drain into small venules that return blood to the venous system

The process of filtration takes place in the _______ ________.

renal corpuscle

Blood Pressure

• forces water and dissolved solutes out of the glomerular capillaries into capsular space

Filtration

• takes place in the renal corpuscle
• produces protein free solution (aka filtrate)
  • similar to blood plasma

Filtrate

• protein-free solution (similar to blood plasma)
• moves from renal corpuscle to renal tubule

Three Functions of the Renal Tubule

1. Reabsorb useful organic nutrients that enter filtrate
2. Reabsorb more than 90% of water that enter filtrate
3. Secrete waste products that failed to enter renal corpuscle through filtration at glomerulus

Proximal Convoluted Tubule

• reabsorption of water, ions, and all organic matter
• cuboidal cells with abundant microvilli

Distal Convoluted Tubule

• secretion of ions, acids, drugs, and toxins
• variable reabsorption of water, sodium ions, and calcium ions
• cuboidal cells with few microvilli

Descending Limb of Loop of Henle

• further reabsorption of water
• squamous cells

Ascending Limb of Loop of Henle

• reabsorption of sodium and chloride ions
• low cuboidal cells

As the filtrate travels along the renal tubule, it is now called ______ _____.

tubular fluid

Collecting System

• series of tubes that carry tubular fluid away from the nephron
  1. collecting ducts
  2. papillary ducts

Each nephron empties into the __________ _________.

collecting system

Collecting Ducts

• receives fluid from many nephrons
• carried fluid to papillary ducts that drain into a minor calyx
• cuboidal to columnar cells
• reabsorption of water, sodium ions

Papillary Ducts

• columnar cells
• conducts tubular fluid to minor calyx

Cortical Nephrons

• 85% of all nephrons
• located mostly in superficial cortex of kidney
• nephron loop is short
• efferent arteriole delievers blood to a network of peritubular capillaries

Juxtamedullary Nephrons

• 15% of nephrons
• long nephron loops that extend deep into the medulla
• peritubular capillaries are connected to the vasa recta

Vasa Recta

• long straight capillaries that parallel the nephron loop

The Nephron Loop (Loop of Henle)

1. descending limb
   • fluid flows toward the renal pelvis
2. ascending limb
   1. fluid flows toward the renal cortex

The Juxtaglomerular Complex

• an endocrine structure that secretes:
  1. hormone erythropoietin
  2. enzyme renin
• formed by:
  1. macula densa
  2. juxtaglomerular cells

Macula Densa

• epithelial cells of DCT
• near renal corpuscle
• tall cells with densely clustered nuclei

The of Urine Production

• maintain homeostasis
  • by regulating volume and composition of blood
  • including excretion of metabolic waste products

Three Organic Waste Products

1. Urea
2. Creatinine
3. Uric Acid

Organic Waste Products

• dissolved in bloodstream
• are eliminated only while dissolved in urine
• removal is accompanies by water loss