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BIO 156

Chapter 9

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The Urinary System

Organs of Excretion

Cells of the body produce a number of wastes that

must be excreted to maintain homeostasis.

Organisms must have a system for eliminating waste.

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Excretory organs remove waste and help regulate

inorganic ions and water. The major metabolic wastes and substances

include:

Ammonia

Urea Uric acid

Bile pigments

Urochrome

Carbon dioxide

Water

Inorganic ions

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The Urinary System

Humans have several organ systems that rid the body

of wastes; one of the most important is the urinarysystem.

The urinary system consists of the kidneys, ureters,bladder, and urethra.

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Kidneys removeimpurities from the bloodand help regulate the waterlevels and ionicconcentrations of theblood.

Blood enters the kidneys

in the renal arteries whosebranches deliver it tomillions of nephrons.

The nephrons produceurine, which drains from

the kidneys into thebladder via the ureters.

Urine is voided throughthe urethra.

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Anatomy of the

Urinary System

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The human kidneyconsists of two

zones: an outer

cortex and inner

medulla.

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Nephrons consist of two parts, a glomerulus and a renal tubule.

The renal tubule consists of four parts:

1. Bowmans capsule

2. The proximal convoluted tubule

3. The loop of Henle4. The distal convoluted tubule

Bowmans Capsule

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Blood filtration in nephrons

involves three processes:

Glomerular filtration is a

physical filtration process

Tubular reabsorption helps

conserve valuable nutrients

and ions.

Tubular secretion is the

transport of waste products

from the peritubular capillariesinto the renal tubule.

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Antidiuretic

Hormone

(ADH )Secretion

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Aldosterone Secretion

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Water balance is also affected by several

chemicals, like caffeine and alcohol (ethanol).

Caffeine increases urine output without affectingADH secretions.

Ethanol inhibits the secretion of ADH by the

pituitary.

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Kidney stones can block the outflow of

urine and cause severe kidney damage.

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Renal failure may occur suddenly or

gradually and can be treated by

dialysis, a mechanical filtering of theblood.

Polycystic Kidney Disease

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Health and Homeostasis

The kidneys help maintain the proper levels of

nutrients and waste in the body. They also help

eliminate toxins in the body and maintain blood pH.

Kidneys can be damaged by severe blood loss,

bacteria, and toxic chemicals.

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End of Chapter 9