Biology unit 32.2

Primary organs of the excretory system:

Kidneys

Urine:

A liquid consisting of water, urea and other waste products

Ureter:

A tube extending from each kidney to the urinary bladder

Urinary bladder

Collapsible sac that temporarily stores urine until it is eliminated from the body.

Urethra

The urethra extends to the vagina opening in females and the penis in males

What are other excretory organs

sweat glands and lungs

Structure of the kidneys

Each kidney consists of an outer region called the renal cortex and an inner region called renal medulla. Each kidney also consists of one million microscopic filtering tubules called nephrons, each of them consisting with one tubule and its associated with blood vessels

The process of urine being secreted out by the kidney

1. Filtration: Blood pressure forces water and small solutes including urea into the Bowman’s capsule

2. Reabsorption: Water, nutrients and some salts are returned to the blood

3. Secretion: Excess salts and some toxins are transported from the blood into the filtrate

4. Excretion: Remaining urine is transported to the bladder and eventually leaves the body

What happens when the water level in the blood falls?

Hypothalamus detects high concentration in blood → Hypothalamus creates feeling of thirst and Posterior pituitary releases ADH → The person drinks more water

What happens when the water level in the blood rises?

Hypothalamus detects low concentration in blood → Pituitary releases less ADH → Kidneys absorb less water

What is done in the case of a kidney failure

Kidney transplant and dialysis

Dialysis:

The patient’s blood is pumped through tubes that function like nephrons.