objectives: 1. 13.0 identify structures and functions of the urinary system 2. 13.1 tracing the...
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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 SystemKidneysUrinary bladderThey are connected by the ureters.The urethra takes urine from the bladder
to the outside of the body.
KidneysLocated 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 medullaProjects into medulla between renal
pyramids, forming renal columns
Kidney FunctionsRegulate composition and volumes of extracellular fluids
Secrete hormone erythropoietin (???)
Role in activation of vitamin DHelp maintain blood pressure
Extracellular fluid volumeSecrete enzyme renin
NephronsThe kidneys’ functional unitsAbout 1 million in each kidneyEach nephron consists of:
Renal corpuscleRenal tubule
Nephron, continued…..Renal corpuscle composed of:
Glomerulus – tangled cluster of capillaries that filter fluid
Glomerular capsule – sac-like structure surrounding the
glomerulusLocated at the proximal end of the
renal tubuleReceives 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 FlowRenal 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 SummaryAbdominal aorta → renal artery →
interlobular arteries → afferent arteries → glomerulus → efferent arteries → peritubular capillaries → renal vein → inferior vena cava
Movements Through Cell MembranesPassive 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 Formation1. 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 FiltrationGlomerular 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 ReabsorptionComposition 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 SecretionCertain substances move from the peritubular capillaries into the renal tubule.
As Na+ is reabsorbed, they may “trade places with” K+ or H+ ions
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