EXCRETION

Distinguish between egestion and excretion

Excretion is the process by which metabolic waste (waste from chemical reactions in cells) is removed from the body

Egestion is the removal of undigested dietary fiber as feces.

What is bilirubin?

Made in the liver from broken-down red blood cells, added to bile, and exits in faeces

Why is excretion important?

It removes many harmful waste products and prevents the buildup of them which could damage and kill cells

List the FOUR excretory organs in humans

Kidneys

Lungs

Skin

Liver

What does the liver excrete?

Bile pigments

State two substances excreted by the skin

Urea, Water and Salts (forms sweat), Heat

State FOUR products excreted by animals

1. Water

2. Carbon Dioxide

3. Urea

4. Bile Pigments

5. Nitrogenous Compounds

6. Heat

List THREE products excreted by plants

• Carbon Dioxide

• Oxygen

• Water

• Organic Waste Products (tannins, alkaloids, anthocyanins, calcium oxalate)

Briefly explain how plants excrete oxygen, carbon dioxide and water vapour

Gases diffuse out through the stomata of leaves and lenticels of bark-covered stems.

How do plants excrete organic waste products? (tannins, calcium oxalate, etc.)

• Organic waste products are stored in dead, permanent tissue.

• They can also be converted into insoluble substances (oils/crystals). In this insoluble form they don’t react in osmotic processes and can be stored in the bark, petals, fruits, etc.

• THEY ARE REMOVED DURING SHEDDING

The kidney excrete water, nitrogenous waste (mainly urea) and salts as?

Urine

How many kidneys does a human have?

2

Each kidney is divided into three regions: ______, ______ and _______

Cortex, Medulla and Pelvis

What is the name of the blood vessel that brings blood to the kidney?

Renal Artery

What is the name given to the tubes that carry urine to the bladder?

Ureters

Each kidney is composed of thousands of ______ that produce urine

Nephrons

In what region of the kidney is the Bowman’s Capsule?

Cortex

What is the ‘glomerulus’?

Cluster of capillaries that lead to the Bowman’s capsule

List the names of the three sections of the kidney tubule

1. First Convoluted Tubule

2. Loop of Henle

3. Second Convol

What is the function of the collecting duct?

To collect urine from multiple nephrons and further concentrate/dilute it by reabsorbing water and electrolytes

Urine is produced in the nephron by 2 processes. What are they called?

Ultra-Filtration & Selective Reabsorption

Explain what occurs during ultra-filtration

Ultra filtration occurs in the glomeruli. The change in diameter of the capillary entering the glomerulus from an arteriole decreases causing a high pressure in the glomerulus. This forces out small molecules into the Bowman’s Capsule forming filtrate. Large molecules remain in the blood.

List THREE molecules that filtrate contains

Water, Urea, Amino Acids, Salt, Hormones, Vitamins, glucose

Explain the process of selective reabsorption

Selective reabsorption is the process by which useful substances are reabsorbed into the blood while passing through the nephron.

First Convoluted Tubule: glucose, amino acids, hormones, vitamins and some water and salt are reabsorbed

Loop of Henle: some water is absorbed

Second Convoluted Tubule: Some salts and some water are reabsorbed

Water is reabsorbed by?

Osmosis

What is ‘osmoregulation’?

The regulation of the concentration of blood plasma and body fluids.

What causes dehydration in the body? (make reference to osmosis and cells)

When body fluids become too concentrated, water leaves body cells by osmosis. The cells shrink and the body becomes dehydrated. If too much water leaves, metabolic reactions cannot take place and cells die.

State 2 ways in which the body can ‘gain’ water

Through drinking

Through food

Water is produced by cells during respiration

List 3 ways in which the body can lose water

In urine

In sweat

During exhalation

Crying

Explain what takes place in the body (mention the brain) when body cells become too concentrated

The hypothalamus detects that blood plasma is too concentrated and stimulated the pituitary gland to secrete antidiuretic hormone (ADH). The blood carries the ADS to the kidneys where it makes the walls of the second convoluted tubules and the collecting ducts more permeable to water. Most of the water is reabsorbed from the filtrate back into the blood.

Why does kidney failure tend to cause death.

When kidney failure occurs, the nephrons stop working and so they are unable to remove waste and regulate body fluids. This causes harmful waste like urea to build up in the blood which is toxic to humans.

What TWO processes can be used to treat kidney failure

Dialysis and Kidney Transplant