The Excretory System

Purpose

Contributes to homeostasis by helping regulate the volume, electrolyte composition, pH of internal environment and by eliminating metabolic waste products.

Waste Products

Some are metabolicE.g. Water, salts, CO2, and ureaUrea is a toxic compound that is produced

when amino acids are used for energy (contain nitrogen).

Three Main Organs of Excretion 1.) Kidneys

These are the main organs of excretion. They are responsible for removing excess water, urea & other excess mineral wastes from the body.

The kidneys act as filters to remove wastes that are collected and transported by the blood.

E.g. Surplus in water or electrolyte (salt) in blood = kidneys excrete in the urine.

Three Main Organs of Excretion

2.)Lungs Every time we exhale, we get rid of small amounts

of water vapor and CO2. CO2 is the waste product of cells that must be

removed from the body so you can take in oxygen.

Three Main Organs of Excretion

3.) Skin: Excretes excess

water, salts, and small amounts of urea through sweating.

The Urinary System

Made up of the: Left and right kidneys Ureters Bladder Urethra

Removes wastes and toxins from the blood and produces urine.

Urine: made of water, excess salts, & urea

How is this different from the excretory system?

Structure of Kidney

2 bean shaped kidneys Located on either side

of the spinal column, near the lower back

Each kidney is about the size of your fist

Each are attached to a renal artery & a renal vein

Structure of Kidney

Each are attached to a renal artery & a renal vein

Renal artery carries blood from the heart’s aorta, this blood is unfiltered and full of wastes collected from the whole body!!

The renal vein carries blood that has been filtered out of the kidney

Structure of Kidney

A ureter leaves each kidney with fluid that contains excess water, salts, urea & other waste products

Ureters lead to the bladder, where liquid wastes are deposited/stored until released as urine from the body.

Expulsion of wastes from bladder is controlled by specific sphincter muscles – voluntary control.

Anatomy of a Kidney

If you cut a kidney in half you will find 2 distinct regions:

1. Inner Part: Renal Medulla

2. Outer Part: Renal Cortex

Anatomy of a Kidney Nephrons

Found in the renal cortex

Working parts of the kidney

Each acts as an individual unit of filtration

About 1 million nephrons per kidney

http://www.pitt.edu/~anat/Abdomen/Kidneys/Kidneys.htm

http://www.as.miami.edu/chemistry/2086/chap26/chapter%2026-new_part1.htm

Nephrons A. Filtration

The nephron begins with Bowman’s Capsule (BC)

BC is a hollow bulb that surrounds a ball of capillaries known as the glomerulus

BLOOD ENTERS BC via the renal arteryWalls of the BC are permeable so blood is

filtered throughFiltered materials (urea, glucose, salts, &

some vitamins) are called filtrates.

Nephrons Filtration Cont’d

Platelets, red and white blood cells are too large to pass, so they remain in the blood

Filtration of blood occurs in the Glomerulus & BC

Adult kidneys filter approx. 180L of blood daily.

Nephrons Re-Absorption

Some filtrates are valuable & can’t be lost, so the body reabsorbs them.

Capillaries in the blood reabsorb valuable materials through active transport.

Water returns to blood through osmosis, 99% of the water that is filtered out of BC is reabsorbed into your blood

Takes place in the tubules of the nephronExcess fluid leaves the BC, enters the tubules

and is called URINE.

Nephrons Re-absorption Cont’d

First part of tubule is the Proximal Convoluted Tubule (PCT).

The PCT carries fluid down into the Loop of Henle (LH).

Urine is concentrated at the LH.The urine then moves up the Distal

Convoluted Tubule where it eventually meets the ureter

Nephrons Re-absorption Cont’d

Purified blood returns to the body through the renal vein, which runs to the Inferior Vena Cava

The urine then moves from the nephrons to the ureters and goes to the bladder where it is stored

Once urine is ready to leave the body, the urine will be expelled through the urethra.

Recap:

http://www.as.miami.edu/chemistry/2086/chap26/chapter%2026-new_part1.htm

http://www.ask.com/wiki/Proximal_convoluted_tubule

http://www.colorado.edu/intphys/iphy3410saul/outlines08fall/nephron.gif

http://www.agefotostock.com/age/ingles/enam01b.asp?foto=13173541&key1=&foto_clave=BSI-3555309&famp=1

Kidney Failure

You have two kidneys in the body located on either side of the spine and extend a little below the ribs.

Your kidneys are bean-shaped organs and is about the size of a fist.

The kidneys receive approximately 10% of the blood that is pumped out of our heart every minute.

Your kidneys are responsible for the following:Regulate fluidsBalance chemicalsRemove wastesSecrete hormones

Condition Explanation:

Progressive in nature Anemia possible – lack of iron Malnutrition (lack of appetite) Decrease well-being Increased risk for heart disease

Toxins build up in blood Weight gain (excess fluids, swollen ankles,

puffiness) Fluid imbalances – dizziness – nausea

Treatment Options:

GeneralLimit fluid intake, high carb, low protein, low

potassium dietToo much potassium can cause irregular

heartbeat

HaemodialysisMost common methodUse of a machine (size of dishwasher) –

blood flow through special filter to remove and filter wastes

Clean blood returned to bodyStrict schedule – 3 times a week for 3 to 5

hours each time

Side effects Less energy Loss of time

Once a month blood is tested to see how effective dialysis is – may not work forever!

Peritoneal DialysisRemoves extra water, wastes, and chemicalsCleansing solution passed through catheter

into abdomenAfter a couple of hours the solution is drainedDoes not require a machineStrict dietMore recent advances, more flexibility (done

at home)

Kidney TransplantationReceive a healthy kidney from a living donor

or a recently deceased donorWhen effective recovers quality of health AND

lifeYields longer life expectancyCould be long waiting lists (shortage of

donors)Typical Surgery Risks (bleeding, infection,

etc.)Anti-rejection medications after surgery – may

weaken immune systemRisk of rejection (body doesn’t accept kidney)