kidney, kidney function, urine formation

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KIDNEY FUNCTION, AND
URINE FORMATION
BABAR KHAN
M.PHIL (MICROBIOLOGY)
CENTER FOR BIOTECHNOLOGY AND MICROBIOLOGY,
UNIVERSITY OF SWAT

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OUTLINES
• Anatomy of the excretory system
• How the kidney is organized
• How the nephron works to filter blood, recycle,
secrete, and excrete
• How filtration is regulated
• Urination reflex

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Kidney Functions
• Filter 200 liters of blood daily, allowing toxins,
metabolic wastes, and excess ions to leave the
body in urine
• Regulate volume and chemical makeup of the
blood
• Maintain the proper balance between water and
salts, and acids and bases

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Other Renal Functions
• Gluconeogenesis during prolonged fasting
• Production of renin to help regulate blood
pressure and erythropoietin to stimulate RBC
production and activation of Vitamin D
• Homeostatic regulation: ECF volume, osmolarity,
ion & pH balance
• Excretion: Metabolic wastes & foreign molecules

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Excretory System: Anatomy Review
Figure 19-1: Anatomy Summary: The Urinary System
• Kidney
• Cortex
• Medulla
• Pelvis
• Nephrons
• Ureter
• Bladder
• Urethra

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Urinary System Organs
Figure 25.1a

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Kidney Location and External Anatomy
Figure 25.2a

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Kidney Location and External Anatomy
• The bean-shaped kidneys lie in a retroperitoneal
position in the superior lumbar region and extend
from the twelfth thoracic to the third lumbar
vertebrae
• The right kidney is lower than the left because it is
crowded by the liver
• The lateral surface is convex and the medial
surface is concave, with a vertical cleft called the
renal hilus leading to the renal sinus
• Ureters, renal blood vessels, lymphatics, and
nerves enter and exit at the hilus

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Internal Anatomy
Figure 25.3b

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Other Urinary System Organs
• 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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The Nephron
• Nephrons are the structural and functional units
that form urine, consisting of:
• Glomerulus – a tuft of capillaries associated
with a renal tubule
• Glomerular (Bowman’s) capsule – blind, cup-
shaped end of a renal tubule that completely
surrounds the glomerulus

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Kidney Functions: Overview
Figure 19-3: The excretion of a substance depends on the amount that was filtered, reabsorbed, and secreted

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Nephron Functions: Overview
Figure 19-2: Filtration, reabsorption, secretion, and excretion

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URINE FORMATION
Figure 19-4: Structure of the renal corpuscle

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URINE FORMATION
Figure 19-6: Filtration pressure in the renal corpuscle

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URINE FORMATION
Figure 19-6: Filtration pressure in the renal corpuscle

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URINE FORMATION STEPS
Figure 19-5: The filtration fraction

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Regulation of GFR

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Regulation of GFR
Figure 19-9: The juxtaglomerular apparatus

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FILTRATION

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Reabsorption: 10 Active Transport
Figure 19-11: Sodium reabsorption in the proximal tubule

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Reabsorption: Secondary Active Transport
Figure 19-12: Sodium-linked glucose reabsorption in the
proximal tubule

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Reabsorption: Passive Transport & Trancytosis

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Reabsorption: Passive Transport & Trancytosis
Figure 19-13: Passive reabsorption of urea in the proximal tubule

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Reabsorption: Receptors can Limit

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Reabsorption: Receptors can Limit
Figure 19-15: Glucose handling by the nephron

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Secretion: From Peritubular Blood vessels & ECF
Figure 19-2 : Filtration, reabsorption, secretion, and excretion

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SECREATION

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Summary
• Kidney produces urine, ureter bladder
urethra
• Nephron filters, reabsorbs, secretes and excretes
• Arteriole pressure dictates GFR through
autoregulation, ANS and hormonal influences
• Most filtrate is reabsorbed & returned via
peritubular blood vessels; excess & toxic remains
are excreted
• Urination reflex uses involuntary and voluntary
paths

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