Biology Chapter 8

What are metabolic activities?

Chemical activities that occur within our body cells all the time

What are metabolic waste products?

Substances produced in metabolic reactions that are harmful or toxic to our bodies

What are some metabolic waste products?

Carbon dioxide

Urea

Mineral salts or ions

Water

What is excretion?

The remoal of metabolic waste products, toxic substances and substances in excess of the body’s requirement

What are excess mineral salts, excess water and urea excreted as?

Urine and sweat from kidneys and skin

What are carbon dioxide and water vapour excreted as?

Gas in exhaled air from the lungs

Carbon dioxide and water are products of aerobic respiration. (T/F)

True

When there is an abnormally high level of carbon dioxide in the blood, …

a condition called hypercarbia occurs where a person might suffer from headache, confusion, rapid breathing and premature heartbeats

How is urea produced?

Absorbed amino acids are transported to the liver, distributed around the body and then assimilated, to synthesise proteins found in the blood plasma like fibrinogen used in blood clotting

When there is an abnormally high urea concentration in the blood, it may cause :

abdominal pain, nausea and vomiting

In rare cases, irregular heartbeats and muscle cramps

Why are excess salts and ions harmful?

They may lower the water potential in the blood plasma, making the blood more concentrated, causing water to pass out of cells and into the blood by osmosis. The cells become dehydrated.

Why is excess water harmful to our body?

Excess water increases blood plasma’s water potential, causing water molecules to move from blood plasma into tissue cells by osmosis, making the cells swell and burst

Why is excretion important?

The body excretes metabolic waste products like urea and toxic substances so that they do not accumulate to a level that becomes harmful to the body

What do people use to get rid of the body odour caused by sweat?

People use antiperspirant that contains aluminium which blocks sweat ducts and reduces the amount of sweat that reaches the skin surface

What does the human urinary system contain?

A pair of kidneys

A pair of ureters

A urinary bladder

Urethra

What is the shape and size of a kidney?

The kidneys are a bean-shaped organs

What is the function of kidneys?

The main function is to excrete erua and excess salt and water as urine

What does each kidney contain?

Numerous nephrons

What is the ureter?

The ureter is a narrow tube that connects the kidney to the urinary bladder, which is where urine passes through

What is the urinary bladder?

The urinary bladder is an elastic muscular bag that stores urine

What is the urethra?

The urethra is the duct through which urine passes from the bladder to outside the body

What are nephrons?

Nephrons are the basic functional units of the kidney which are tiny kidney tubules where urine is formed

What are the parts of a nephron?

Bowman’s capsule

Proximal convoluted tubule

Loop of Henle

Distal convoluted tubule

Several nephrons open into a tube called the …

collecting duct

Bowman’s capsule is a …

cup-like structure

The proximal convoluted tubule is the …

first coiled tubule

The distal convoluted tubule is the …

second coiled tubule

The loop of Henle is a …

U shaped tubule

The collecting duct is a …

straight tubule that leads to the ureter

Explain the process of how blood enters a nephron

Nephrons are surrounded by blood capillaries that are connected to the renal artery and renal vein. Blood enters the kidney by the renal artery and branches to form the afferent arteriole which brings blood into the glomerulus. Each arteriole further braches into a mass of blood capillaries in the Bowman’s capsule known as glomerulus. An efferent arteriole transports blood away from the glomerulus. Blood leaving the glomerulus continues into blood capillaries surrounding the nephron. These blood capillaries unite to form venule, which lead into a branch of the renal vein

Blood enters the kidney by the renal artery and leaves the kidney by the …

renal vein

What are the 2 main processes for urine formation?

Ultrafiltration

Selective reabsorption

What does ultrafiltration involve?

High blood pressure in the glomerulus as afferent arteriole is wider than efferent arteriole

Blood plasma is forced out of glomerular blood capillaries into Bowman’s capsule

Filtered blood plasma called glomerular filtrate contains small, soluble molecules like salt, water, glucose, amino acids, and urea

How is the glomerulus suited to urine formation?

It is a network of blood capillaries which provides a large surface area for filtration to occur

Blood capillaries have one-cell-thick walls and tiny pores in them

Blood capillaries are covered by a thin, partially permeable membrane that only allows small molecules to pass through. It is impermeable to blood cells, platelets and large molecules like proteins

In a normal adult, how much glomerular filtrate is produced per minute?

120cm3

What is selective reabsorption?

It is the process where only substances the body needs are reabsorbed, like most water via osmosis, some salts, and all glucose and amino acids via active transport

What are waste products that are passed out of the nephron as urine?

Excess water

Urea

Mineral salts

What is reabsorbed in the proximal convoluted tubule?

Most water via osmosis

Most mineral salts via active transport and diffusion

All glucose and amino acids via active transport

What is reabsorbed in the distal convoluted tubule?

Some water via osmosis

Some mineral salts via active transport

What is reabsorbed in the loop of Henle?

Some water via osmosis

Some mineral salts via osmosis

What is reabsorbed in the collecting duct?

Some water via osmosis

What is osmoregulation?

Osmoregulation is the control of water potential and solute concentration in the blood to maintain a constant water potential in the body

If the blood plasma becomes too diluted, …

water will enter the blood cells by osmosis. The blood cells will swell and even burst. The tissue cells will also swell because water from blood plasma will move into cells

If the blood plasma becomes too concentrated, …

water will move out of the cells by osmosis. The body cells and tissue cells will become completely dehydrated and shrink. They will not be able to perform metabolic functions properly, which is possibly fatal

What controls the amount of water in the blood plasma?

Anti-diuretic hormone(ADH)

Where is the ADH produced?

ADH is produced by a region of the brain called the hypothalamus

How is ADH released?

It is released by the pituitary gland

ADH increases,,,

water absorption at the collecting duct

What are kidneys’ role in osmoregulation?

They are osmoregulators, because they help to regulate the water potential and solute concentration in the blood

When water potential of blood plasma increases above the normal level, …

The hypothalamus detects the increase in water potential of the blood. The pituitary gland is stimulated to secrete less ADH into the bloodstream. Cells in the walls of the collecting duct become less permeable to water. Less water is reabsorbed from the collecting duct into the surrounding blood capillaries. A larger volume of dilute urine is produced. Water potential of blood decreases to normal level.

When water potential of blood decreases below the normal level, ….

The hypothalamus detects the decrease in water potential of blood. The pituitary gland is stimulated to secrete more ADH into the bloodstream. Cells in the walls of the collecting duct become more permeable to water. More water is reabsorbed from the collecting duct into the surrounding blood capillaries. A smaller volume of concentrated urine is produced. Water potential of blood increases to normal level.

Why are kidneys important?

The kidneys are osmoregulators and are excretory organs.

As excretory organs, …

the kidneys excrete metabolic waste produts like urea, excess water, mineral salts, in the form of urine.

As osmoregulators, …

the kidneys regulate the solute concentration and water potential in the blood, maintaining a constant water potential in the blood