Transcript Urinary System Chapter 17

Objectives:
1.13.0 Identify structures and functions of the
urinary system
2.13.1 Tracing the filtration of blood from the
kidneys to the urethra
3.13.2 Recognizing diseases and disorders of the
urinary system
Urinary System:
 removes salts and nitrogenous wastes
from the blood.
 helps maintain normal concentrations
of water and electrolytes of bodily fluids
 regulates pH and volume of bodily
fluids
 helps control RBC production and blood
pressure
Organs of the Urinary System
 Kidneys
 Urinary bladder
 They are connected by the ureters.
 The urethra takes urine from the bladder to the
outside of the body.
Kidneys
 Located on either side of the vertebral
column, on the posterior wall of the
abdominal cavity.
 Left is 1.5-2.0 cm higher than the right
 Where do people feel kidney pain?
Kidney Structure
 Lateral surface is convex; medial side is
deeply concave.
 Medial depression leads to hollow
chamber called the renal sinus.
 Entrance to sinus is called hilum, and it is
also the passage for blood vessels,
nerves, lymphatic vessels, and the ureter.
Kidney Structure, continued…..
 Superior end of the ureter forms the
renal pelvis (funnel-shaped sac inside
the renal sinus)
 Renal pelvis subdivides into major
calyces (tubes, which divide into minor
calyces.
 Renal papillae project into the renal
sinus.
Kidney Structure, continued…..
 Two distinct regions in the kidneys:
 Renal medulla (inner)

Composed of conical masses (renal
pyramids) that appear striated
 Renal cortex (outer)


Forms a shell around medulla
Projects into medulla between renal
pyramids, forming renal columns
Kidney Functions
 Regulate composition and volumes of
extracellular fluids
 Secrete hormone erythropoietin (???)
 Role in activation of vitamin D
 Help maintain blood pressure
 Extracellular fluid volume
 Secrete enzyme renin
Nephrons
 The kidneys’ functional units
 About 1 million in each kidney
 Each nephron consists of:
 Renal corpuscle
 Renal tubule
Nephron, continued…..
 Renal corpuscle composed of:
 Glomerulus – tangled cluster of capillaries
that filter fluid
 Glomerular capsule –



sac-like structure surrounding the
glomerulus
Located at the proximal end of the renal
tubule
Receives the fluid filtered by the glomerulus
Nephron, continued…..
 Renal tubule:
 Transports fluid from the glomerular
capsule to a minor calyx
 Proximal convoluted tubule:
 Dips down toward the renal pelvis and
becomes the descending limb of the
nephron loop (“loop of henle”)
 Curves back up (ascending limb of the
nephron loop)
 Becomes coiled again (distal convoluted
tubule)
Nephron, continued…..
 Distal convoluted tubules from several
nephrons will merge in the renal cortex
to form a collecting duct
 In the renal medulla, several collecting
ducts will merge before emptying into a
major calyx through an opening in a
renal papilla.
Renal Blood Flow
 Renal arteries branch off the _________,
and enter the kidneys through the ____.
 Renal arteries give off several branches:
 Interlobal arteries → arcuate arteries →
interlobular arteries → afferent
arterioles
 The afferent arterioles enter the
nephrons and form the glomerulus.
Renal Blood Flow, continued…..
 Blood leaves the glomerulus through
efferent arterioles.
 The efferent arteriole branches into a
network of capillaries, called the
peritubular capillary system.
 Blood then enters the venous system of
the kidney and enters the __________
through the renal vein.
Renal Blood Flow Summary
 Abdominal aorta → renal artery →
interlobular arteries → afferent arteries →
glomerulus → efferent arteries →
peritubular capillaries → renal vein →
inferior vena cava
Movements Through Cell
Membranes
 Passive mechanisms:
 Diffusion – EX: exchange of O2 and CO2 in
the lungs
 Facilitated diffusion – uses carrier
molecules; EX: movement of glucose
through cell membrane
 Osmosis – movement of water…..
 Filtration – EX: water molecules leaving
blood capillaries
Movements Through Cell
Membranes, continued…..
 Active mechanisms:
 Active transport - moves molecules from
areas of lower concentration to areas of
higher transportation
 Endocytosis – cell membrane engulfs
substances, bringing them into the cell
 Exocytosis – a vesicle fuses with the cell
membrane to “expel” a substance
Urine Formation
1. Glomerular filtration:
 Glomerular capillaries filter blood
plasma

Produces 180 L of fluid daily! (more than 4x
total body fluid)
2. Tubular reabsorption: kidneys reclaim
water, electrolytes, and glucose needed by the
body
3. Tubular secretion
1. Glomerular Filtration
 Glomerular capillaries contain many tiny
openings, making them more permeable
than capillaries in other tissues.
 Glomerular capsule receives the
glomerular filtrate (mostly water and
same components as plasma)
 Filtration is driven by pressure
differences (net filtration pressure).
2. Tubular Reabsorption
 Composition of glomerular filtrate
entering renal tubule is different than
that of urine leaving the tubule:
 Glucose – present in glomerular filtrate,
absent in urine
 Urea and uric acid – more concentrated in
urine than in glomerular filtrate
Tubular Reabsorption,
continued…..
 Some substances pass out of the tubular
fluid, through the epithelium of the
renal tubule, and into the interstitial
fluid.
 These substances diffuse into the
peritubular capillaries.
 Reabsorption occurs throughout the
renal tubule, but mostly in the proximal
convoluted tubule.
Tubular Reabsorption,
continued…..
 Different parts of the tubule are designed
to reabsorb specific substances, using
different transport modes:
Substance
Transport
Mechanism
Portion of Tubule
Glucose
Active transport
Proximal tubule
Water
Osmosis
Throughout tubule and
collecting duct
Amino acids
Active transport
Proximal tubule
Protein
Endocytosis
Proximal tubule
Various chemicals Active transport
Proximal tubule
Sodium ions
Active transport
Throughout tubule and
collecting duct
Cl-, PO4-3, and
HCO3- ions
Passive transport Throughout tubule
(w/Na+ ions)
3. Tubular Secretion
 Certain substances move from the
peritubular capillaries into the renal
tubule.
 As Na+ is reabsorbed, they may “trade
places with” K+ or H+ ions
Urine Formation Recap
1. Glomerular filtration of plasma
2. Tubular reabsorption of substances
into the interstitial fluid: water,
glucose, sodium, potassium, calcium,
proteins, amino acids, etc.
3. Tubular secretion of substances into
urine: hydrogen and potassium ions,
etc.