Excretory System

THE URINARY

SYSTEM

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Urinary System

Functions:

•Removes waste from the blood.

•Regulates water and pH of blood

•Controls red blood cell
production

Major Organs:

-Kidneys
-Bladder
-Ureters
-Urethra

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Where are the kidneys located?

•The kidneys are the most
important organs in the urinary system.
•They are bean-shaped organs located on either side of the spine.

•The kidneys are protected and
held in place by perirenal fat
tissue and renal fascia
(connective tissue).

•The right kidney is slightly
lower to make space for the
liver.

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What is the anatomy of a kidney?

•Each kidney is
surrounded by a renal capsule made of connective tissue.

•Cross-section of a
kidney:
•Outer cortex

•Inner medulla made of renal pyramids

•The renal pyramids are the site of urine
production.

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•After formation in the
renal pyramid, urine drains into a tube called the minor calyx (plural:
calyces), then into the
major calyx.

•The major calyces
converge at the renal
pelvis, which then forms
the ureter, ultimately
removing the urine from
the kidney and passing it to the urinary bladder.

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How is urine collected in the

kidneys?

How does blood flow through the

kidney?

•Blood flows into the kidney
through the renal artery.

•As it enters the hilum
(indented region), it
separates into increasingly
smaller arteries through the renal medulla and then cortex.

•Blood flows out in a reverse pathway and through the renal vein.

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Summary

•The kidneys are located on either side of the spine and protected by fat and a renal capsule. Urine is formed in the renal pyramids and collected in the minor and major calyces. Blood is
supplied by the renal artery and leaves through the renal vein.

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Multiple Choice

How is urine collected in the kidneys?

• Filtration in the nephrons collects waste and excess substances to form urine.
• Urine is collected in the liver
• Urine is collected in the lungs
• Urine is collected in the heart

Multiple Choice

Where, on the kidneys, is the site of urine production?

• renal pyramids

• Nephrons
• outer cortex

• inner medula

Reorder

Reorder the following path of urine

• renal pyramids

• minor calyx

• major calyx

• ureter

• urinary bladder

1

2

3

4

5

• 1
• 2
• 3
• 4
• 5

Multiple Choice

What protects the kidneys?

• Spinal cord and liver
• Lungs and pancreas
• Stomach and spleen
• Rib cage and renal capsule

Multiple Choice

Why is the right kidney slightly lower?

• Due to gravitational pull
• Due to the presence of the liver on the right side of the body.
• Because of the heart's position
• As a result of muscle imbalance

Multiple Choice

Where are nephrons located within the kidney?

• Renal pelvis and ureter
• Renal capsule and renal sinus
• Renal papilla and renal pyramid
• Renal cortex and renal medulla

•The functional unit of the kidney is a nephron,
which is a long tubular structure and associated
blood vessels.

•Most nephrons are found in the renal cortex, but some also extend into the medulla.

•Each kidney contains about 1.3 million nephrons.

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Where are nephrons found?

What is the anatomy of a nephron?

•Each nephron has two major portions:
1. Renal tubule: a 3 cm long tube with three segments (proximal convoluted tubule, nephron loop or Loop of Henle, & distal convoluted tubule)

2. Renal corpuscle: Consists of the glomerulus (a ball of capillaries) and the Bowman’s capsule (a hollow, cup-shaped structure that surrounds the glomerulus)

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How is urine formed?

•Urine is formed within the nephron using 3 major
processes:

1.

Glomerular filtration

-Blood enters through the afferent arteriole.
-Fluid and solutes from the blood pass through specialized
filtration cells called podocytes into the Bowman’s capsule.
-Once in the capsule, the fluid is called filtrate.

How is urine formed?

2.

Tubular reabsorption

-Most of the water (80%) and many ions and nutrients are reabsorbed into the blood through both passive and active transport.
-This occurs mostly in the proximal convoluted tubule.

3.

Tubular secretion

-Additional substances are actively removed from the blood (drugs, steroids).
-H+ and K+ are fine-tuned to control blood pH.

1Filtration:

-Blood enters through the
afferent arteriole.
-Fluid and solutes from the
blood pass through podocytes into the Bowman’s capsule.

-Remaining blood leaves through the efferent arteriole and the filtrate continues into the renal
tubule.

Location: Bowman’s
capsule

2

-Most of the water (80%)
and many ions and nutrients are reabsorbed into the blood
Location: Proximal (near)
Convoluted Tubule & Loop
of Henle

Reabsorption:

3

-Additional substances are actively
removed from the blood (H+, drugs,
steroids)
-Fine-tuning of K+ and H+ in the
urine to regulate blood pH
Location: Distal (far) Convoluted
Tubule

Secretion:

Overview

1

2

Summary

•Nephrons are responsible for
producing urine. Blood is filtered
within the Bowman’s capsule, then
solutes and water are regulated in the renal tubule through the processes of reabsorption and secretion.

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Multiple Choice

What are the 2 major parts pf the nephron?

• renal corpuscle and renal tubule
• renal capsule and renal duct
• kidney corpuscle and kidney tubule
• nephron capsule and nephron tubule

Labelling

Label the Nephron

Drag labels to their correct position on the image

Bowman's capsule

Proximal Convoluted tubule

Distal convoluted tubule

Loop of Henle

Glomerulus

Collecting Duct

What is the composition of urine?

•Urine is 95% water, 5% solutes

•Nitrogenous wastes contained in
urine include:
•Urea- from metabolism of proteins, is the most common solute.

•Uric acid- waste product of nucleic acid
metabolism

•Creatinine- from creatine metabolism in muscles

•Typical urine:

•Has a pH near 6

•Is straw-colored

•Is sterile

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•The specific gravity of pure water is 1.0. Urine is generally 1.001
(dilute) to 1.035 (concentrated).

•Urinalysis (urine testing) can
provide a lot of information about the body’s processes.

•Atypical substances found in urine include:

•Glucose

•Blood protein

•Red blood cells

•Hemoglobin

•White blood cells

•Bile

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•From the kidneys, urine enters the
tube-like ureters and empties into the elastic urinary bladder for storage.

•From the bladder, the urine passes
through the urethra and is released
from the body by 2 sphincter muscles.

•Just as in the rectum, there is an
internal (involuntary) sphincter and an external (voluntary) sphincter.

•Loss of control (often with age) in the
external urethral sphincter is the cause of incontinence.

•The process of emptying the bladder is called micturition or voiding.
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How does urine leave the body?

Summary

•A medical professional can test urine
(called urinalysis) to determine overall health. Urine travels from the kidneys through the ureters, is stored in the bladder and finally released through the urethra by two sphincter muscles during micturition.

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© Suburban Science 2018