Unit 3.D:The Excretory System

Index

1. The Urinary System in Humans

2. Excretion

3. The anatomy of the kidneys

4. The production of urine

5. Diseases of excretory system

1. Parts of the Urinary System in Humans Kidneys they remove urea and other

waste products from the blood and form urine.

Ureters they carry urine from the kidney to the bladder

Bladder it stores urine before it is released from the body. It has a muscular wall.

Urethra It carries urine out of the body.

• Men urethra is common to the reproductive system

• Women urethra is an independant tube

2. Excretion

Excretion is the elimination of waste products that are produced by the body cells.The cells release the waste substances into the blood. The blood must, therefore,be purified.

Metabolic waste products are:

• Nitrogen compounds excess of protein is broken down in the liver and forms urea

• Carbon dioxide• Water• Mineral salts

EXCRETORY ORGAN WASTE PRODUCTS

Lungs Carbon dioxide, water vapour

Kidneys Urea, water and salts

Skin Water and salts

4. The anatomy of the kidneys

Each kidney is made up of thousands of small functional units knownas nephrons. Each one of these nephrons filters and purify the blood independently.

Blood enters the kidneys through the renal arteries

Glomerulus = capsule which contains lots of blood capillaries

Nephron

Bowman’s capsule surrounds the glomerulus

The tubules and the loop of Henle carry the urine to the ureters

Renal cortex Bowman’s capsules

Renal medulla loops of Henle and collecting ducts

Renal pelvis ducts which collect the urine produced by the nephrons.

4. The production of urine

The formation of urine is a very selective process. Urine contains: water toxic substances (urea, uric acid, etc.)

ureauric acid

ammonia

The composition of sweat is similar to urine. It is produced by filtering the blood that reaches the skin.

Activity 4, page 71

1. Filtering:Substances go from the glomerulus to the Bowman’scapsule

2. Reabsorption:Water and useful substances go back from the tubulesto the blood

3. Urine (water, urea, uric acid, salts) arrives to the renal pelvis, where reaches the ureters.

5. Diseases of Excretory System

Kidney stones crystals of uric acid

Cystitis inflammation of the bladder caused by a bacterial infection.

Renal insufficiency kidneys do not filter the blood correctly and waste products are not removed from the blood

Hemodialysis  filtering of blood in an apparatus to remove waste products. It is performed in cases of kidney failure.

Kidney transplant

Video Urinary System, the nephron