• Performs the vital function of removing the organic waste products generated by cells throughout the body.– Regulates blood volume, pressure, and pH– Regulates plasma concentration of ions– Conserving valuable nutrients– Excreting unnecessary waste (salts and

nitrogen)

The Urinary System (17.1)

The Urinary System (17.2/10)

• Kidneys (17.3)– Filter urea out of the

blood– Control water

balance in the blood – Produce urine

• Ureters– Tubes that carry

urine from the kidneys to the urinary bladder

The Urinary System (17.10)

• Urinary Bladder– A flexible sack that

stores urine until excretion

• Urethra– A tube that exits

through male and female genitalia

– Expulses urine from the system

Your kidneys are located higher than you may think… (17.2)

Inside the kidney (17.2)

How much urine is produced per day?

It varies depending on the following:• Quantity of water ingested

• Types of food ingested• Quantity of water eliminated through

perspiration• Level of physical activity• Ambient temperature

Homeostasis of body water (17.4)

• Too little water Too much water

↓ blood volume ↑ blood volume

not enough blood

Tissues deprived of O2 and nutrients

↑ blood pressure

Heart attack, stroke, etc

DEATH DEATH

How do the kidneys maintain homeostasis of body water?

(17.4)- EXCRETE wastes (eg. urea, uric acid)

- Selectively reabsorb (into the bloodstream) substances that are in short supply (eg. Water,

salts, sugar).

Function of the Kidneys (17.3):

The main function of the kidneys is to filter blood and eliminate wastes

– Kidneys are selectively permeable: some substances pass through them, others do not

this allows the kidneys to filter the blood: unwanted material (waste) is kept inside

the kidney and disposed of through the ureters

wanted material remains in the bloodstream or is selectively reabsorbed into the bloodstream

Selective reabsorption of water

• ADH (antidiuretic hormone) is released from the pituitary gland and travels through the blood to the kidney where it promotes water reabsorption, thus preventing its loss in the urine.

Anatomy of the kidney (17.2)

• Renal artery: – Blood enters the kidneys here– Branches off to form renal arteriole which

leads blood into the nephron

• Renal vein– Receives purified/filtered blood from the

kidney

Cross Section of a Kidney (17.2)

Anatomy of the Kidney: - the nephron (17.3/5)

• where filtration occurs in the kidney

• each kidney contains nearly 1 million nephrons

• located in the outer layer (renal cortex) of the kidneys

• Consists of the glomerulus, the bowman’s capsule and the collecting tubules

Anatomy of the Kidney:- the nephron (17.5)

• Glomerulus– Ball of vessels– Wastes, water and

minerals diffuse from the blood into:

• Bowman’s Capsule– Surrounds the glomerulus– Receives the diffused

material from the glomerulus

• Collecting tubule – Collects remaining waste

that was not reabsorbed in to blood

Proximal convoluted tubule

Distal convoluted tubule

Where does the excretion of wastes and reabsorption of water occur? (17.8)

During this journey water is then reabsorbed, into

the renal venule

Wastes are excreted into Bowman’s capsule,

and continue into the collecting tubule

Bowman’s Capsule

Animation: http://www.biologymad.com/resources/kidney.swf

filtrate (water, salt)

BOWMAN’S CAPSULE

MEM

BRANE

BASEMENT

sand, salt, water

residue: sand

ultrafiltrate (water,salt, sugar, urea)

large molecules (proteins), salt,

sugar, urea, waterresidue:

large molecules (proteins)

PAPER

FILTER

ERLENMEYER FLASK

(17.6)

Filtration Process (17.6)

1) Blood enters the kidneys through the renal arteries,

2) The renal arteries branch into smaller arterioles which bring blood to the nephron.

3) Inside the nephron, the arterioles branch into an even smaller ball of capillaries called the glomerulus.

4) Wastes, water and minerals diffuse from the capillaries (glomerulus) into Bowman’s capsule

Filtration Process (17.6)

5) Necessary salts and water will re-enter the blood stream at the venules which flow into the renal vein and then the inferior vena cava.

6) The remaining waste passes through the proximal convoluted tubule, loop of Henle, and DCT and is then collected in the collecting tubule

7) The collecting tubules empty into the ureter, which takes waste to the bladder where it is stored.

8) When the bladder becomes full it will send a signal to the brain.

9) The brain then sends a signal back to the bladder for the waste to be excreted out of the body through the urethra.

Overview of the Urinary System

Overview of the Urinary System