Transcript Urinary System Organs

Urinary System Organs
 Kidney – Filters blood, allowing toxins, metabolic
wastes, and excess ions to leave the body in urine
 Urinary bladder – provides a temporary storage
reservoir for urine
 Paired ureters – transport urine from the kidneys to
the bladder
 Urethra – transports urine from the bladder out of
the body
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Urinary System Organs
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Figure
Kidneys -Overview
 Blood passes through kidney – filtration occurs at
capillaries – 20% of plasma becomes filtrate
 Filtrate passes through nephrons – water and
electrolytes are reabsorbed
 Some electrolytes, drugs and toxins may be secreted
into filtrate by tubular secretion
= Urine
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Nephron
 Tubular structures that produce filtrate from plasma
 Water, electrolytes, drugs and toxins are removed or
added to filtrate as filtrate flows through tubules
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The Nephron
 Nephrons are the structural and functional units that
form urine, consisting of:
Renal corpuscle
 Glomerulus – a tuft of capillaries associated with a
renal tubule
 Glomerular (Bowman’s) capsule – blind, cupshaped end of a renal tubule that completely
surrounds the Glomerulus
 Glomerular endothelium – fenestrated epithelium
that allows solute-rich, virtually protein-free filtrate
to pass from the blood into the glomerular capsule
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Glomerular Filtration Rate (GFR)
4/11/2016
Mickey Dufilho
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Figure 25.9
The Nephron
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Figure
Renal Tubule
 Proximal convoluted tubule (PCT) – composed of
cuboidal cells with numerous microvilli and
mitochondria
 Reabsorbs water and solutes from filtrate and
secretes substances into it
 Reabsorbs 100% of glucose, amino acids, escaped
proteins, some vitamins, 60-70% of Na+, K+, Cl-,
Ca++ and water
 Secretes H+, NH3 (ammonia), drugs, toxins, uric
acid and histamine
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Renal Tubule
 Loop of Henle – a hairpin-shaped loop of the renal
tubule
 Descending Limb
 Impermeable to electrolytes, permeable to water
 80% Water is absorbed, filtrate becomes
hypertonic
 Ascending Limb
 Permeable to Na+ and Cl- but not water
 Filtrate becomes hypotonic
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Renal Tubule
 Distal convoluted tubule (DCT)
Reabsorbs:
 Na+ directed by aldosterone
 Water directed by ADH
 Ca++ directed by PTH
 Some HCO3-, depending on pH of blood
Secretes:
 NH3, K+, drugs, toxins, and creatinine
 Some H+, depending on pH of blood
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Collecting Tubule
Reabsorbs
 Na+ directed by aldosterone
 HCO3- depending on blood pH
 Urea to maintain hypertonic interstitial fluid around
nephron tubules
 Water directed by ADH
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Afferent and Efferent Arterioles
 Larger diameter vessel is incoming – afferent
 Smaller diameter vessel is outgoing – efferent and it
becomes the peritubular capillaries
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Capillary Beds of the Nephron
 Every nephron has two capillary beds
 Glomerulus
 Peritubular capillaries
 Each glomerulus is:
 Fed by an afferent arteriole
 Drained by an efferent arteriole
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Hemodialysis
 Diffusion of solutes through semipermeable
membrane
 Dialysis machine- group of tubules that act like a
nephron
 Membrane allows free passage of glucose,
electrolytes and nitrogenous wastes
 Filtration and production of filtrate is not required
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