2.6 - role of kidney in homeostasis (TRIPLE)

What are the 2 functions of the kidneys?

1. Regulate water content of the blood

2. Remove waste products from the blood

What is urea and where is it made?

• Urea is a poisonous substance made of amino acids

• Urea is made in the liver

What do your kidneys remove, from where?

Your kidneys remove urea and excess salt ions

from your blood.

What is urine?

Urea and salt dissolved in water

Describe the journey of the blood to and from the kidney

• Blood from the heart,

• Through the renal artery INTO the kidney

• Blood LEAVES the kidney through the renal vein

• Blood travels via vena cava,

• Back to the heart

What is the ureter and its job?

The ureter is the tube that carries urine from the kidneys to the bladder

What is the urethra and its job?

The urethra is a tube that carries urine out of the body from the bladder

Label the kidney:

Label the human excretory system:

What is ultrafiltration?

Filtration of small molecules under pressure from the capillary knot into the Bowman’s capsule

What is selective reabsorption?

Useful molecules being reabsorbed back into the blood from the tubule

Describe the process of ultrafiltration

1. The arteriole bringing blood to the capillary knot is wider than the one taking it away, so high pressure builds up

2. High pressure forces small molecules in the blood out of the capillary and into the Bowman’s capsule

What particles are and aren’t filtered during ultrafiltration?

Are filtered: small molecules (water, urea, salts, glucose)

Are NOT filtered: particles too big to leave the capillaries (large plasma proteins & red blood cells)

Describe the process of selective reabsorption

1. The blood capillaries around the kidney tubules reabsorb useful substances from the fluid in the kidneys back into the blood

2. The remaining fluid (containing urea, excess water & salts) passes to the collecting duct.

This fluid is now called urine

What does ADH stand for, and what does it control?

ADH: anti-diuretic hormone

ADH controls water content of the blood

What is the effect of ADH?

ADH increases tubule permeability, allowing our kidneys to reabsorb more water back into the blood

What in our body monitors water levels?

The brain

Describe the process that takes place in our body if there’s too much water in our blood?

1. The pituitary gland in our brain releases LESS ADH

2. The kidneys reabsorb LESS water

3. Therefore making more DILUTE urine

Describe the process that takes place in our body if there’s too little water in our blood?

1. The pituitary gland in our brain releases MORE ADH

2. The kidneys reabsorb MORE water

3. Therefore making more CONCENTRATED urine

What is added to the patient’s blood if they require to use a dialysis machine, and why?

BLOOD THINNERS

Prevents blood clotting and prevents a blockage

The _____ ______ takes blood INTO the dialysis machine

The renal artery takes blood INTO the dialysis machine

The _____ ____ takes blood AWAY from the dialysis machine

The renal vein takes blood AWAY from the dialysis machine

What is a COUNTER-CURRENT FLOW, and why is it needed?

The dialysis fluid flows in the opposite direction to the blood

It is needed in order to maintain a concentration gradient for diffusion

What does the dialysis solution contain, and why?

• There is NO UREA - so urea diffuses from the blood and into the dialysis solution across a concentration gradient

• Equal concentration of GLUCOSE AND SALT IONS compared to the blood - prevents losing these substances

What are 2 options may a patient with kidney failure choose?

• Dialysis machine

• Kidney transplant

3 positives and negatives of going on a DIALYSIS MACHINE

• Non-invasive

• No drugs needed

• No problems with rejection

• Temporary treatment

• Diet restrictions

• Patient must visit hospital several times a week

3 positives and negatives of a KIDNEY TRANSPLANT

• Potential to cure problem for years

• No diet restrictions after treatment

• Patient doesn’t have to regularly visit the hospital

• Involves major surgery

• Patient must take immunosuppressant drugs everyday for the rest of their life

• New kidney could be rejected

What does the presence of protein in urine indicate?

Kidney disease

What does the presence of glucose in urine indicate?

Diabetes