The Excretory SystemChapter 13 Section 3

The Organs of the Excretory System

The excretory system collects wastes produced by cells and removes the wastes from the body

Excretion- process of removing wastes Urea- chemical that comes from the breakdown of proteins Kidneys- 2 major organs that eliminate urea, excess water,

and some other waste materials Urine- watery fluid produced by kidneys that waste is

eliminated in Ureters- two narrow tubes from which urine flows from the

kidneys to the urinary bladder Urinary bladder- a sacklike muscular organ that stores urine Urethra- small tube from which urine leaves the body

The Excretory System

The Kidney

The Filtering Process

Kidneys act as filtersNephrons- tiny structures that remove

wastes from blood and produce urine

Filtering Out Wastes

Blood flows from the kidneys through arteries to capillaries in a nephron

Capillaries are surrounded by a capsule connected to a long tube

In the capillary cluster, urea, glucose, other chemicals, and some water move out of the blood and into the capsule

Formation of Urine

Urine forms from the filtered material that passes into the capsule

Filtered materials flow through the long, twisting tube

As liquid moves through the tube, many needed substances are reabsorbed into the blood stream

Urea and other wastes remain in the tube

Fluid remaining in the tube is urine

Analyzing Urine for Signs of Disease

Chemical analysis of urine can be useful in detecting some medical problems

Urine normally contains no glucose or protein

Glucose in urine may indicate diabetes

Protein in urine can be a sign of kidneys not functioning properly

Water Balance in the Body

The excretory system helps maintain homeostasis by regulating the amount of water in the body

Your excretory system maintains the amount of water needed in the body by excreting excess fluid and reabsorbing needed fluids

Other Organs of Excretion

Most wastes produced by the body removed through the kidneys

Other organs of excretion are the lungs, skin, and liver

Lungs excrete carbon dioxide and water

Skin excretes wastes through perspiration

The liver breaks down wastes before they are excreted; old RBC hemoglobin recycles to bile

Review

What is the function of the excretory system?

Describe the two stages of urine formation.

What roles do the lungs, skin, and liver play in excretion?

How do the kidneys help regulate the amount of water in the body?