The excretory system

By the end of today’s class you should be able to:

State the function, location, products of the skin and lungs as organs of excretion

Explain temperature regulation in humans.

Refer to the different methods of temperature regulation in animals -- Ectotherms and Endotherms

Excretion is the removal of waste products of metabolism from the body.

3.4.6 The Excretory System in the Human

The excretory system plays a role in homeostasis:

(i) it maintains the ideal composition of an organism's fluids,including fluid balance and chemistry.

(ii) it prevents the build up of poisonous wastes in our bodies.

OUR EXCRETORY SYSTEM

In the liver, excess amino acids are split into a carbohydrate and urea.

The main waste products made in our body are water, carbon dioxide and nitrogenous (nitrogen-containing) wastes.

Our lungs

• We excrete carbon dioxide and water vapour from our bodies using our lungs

Our skin

In our skin our sweat glands excrete water and some salts.

In today’s lesson you should learn about

• The role of the skin in the excretory system and in homeostasis

The role of skin..

Role of Skin in Homeostasis -- Temperature Regulation

Role of Skin as Excretory Organ – removal of sweat

Temperature Regulation

Temperature influences the rate of enzyme-controlledreactions that sustain life.

Mammals and birds are endotherms (warm blooded): their source of heat is internal [from their own metabolic heat].

Most animals are ectotherms (cold blooded) — they lose or gain heat by moving into areas where temperature is suitable, e.g. fish, amphibians, reptiles.

The SKIN

Skin and temp control• http://

www.abpischools.org.uk/page/modules/skin/skin3.cfm

How does your skin act when body temp drops too low...

– Erector muscles in the skin form goose bumps so warm air is trapped by hairs

– Blood vessels contract blood flows under adipose tissue so and this reduces heat loss through the skin

– The brain causes us to shiver this produces heat - Body temperature is raised

Skin and temp control in cold conditions

– No goose bumps are formed so warm air is escapes through hairs

– Blood vessels expand and this causes heat loss through the skin

– We sweat, the sweat evaporates from our skin and this takes away body heat

Skin and temp control in warm conditions

Blushing – what’s going on here?

•Body temperature rises with embarrassment

•Skin tries to cool us down

•Blood vessels in face dilate

•Face goes red

This loss of water, as sweat, must be replaced—that is why it is important to drink water before, during and after exercising to maintain the balance of water and salts in the body.

Can you..

Explain the role of the excretory system in homeostasis

Explain temperature regulation in humans.

Refer to the different methods of temperature regulation in animals -- Ectotherms and Endotherms

State the function, location, products of the skin lungs as organs of excretion

By the end of the lesson you should be able to:

• Know the structure of the urinary system in humans

• Know the basis function of each of the following – kidneys, ureter, urinary bladder, urethra

• Describe the role of the kidney in regulating body fluids,

• Identify the site of filtration and reabsorbtion in the kidney.

• Describe the pathway of urine from the kidney to the urethra

The urinary system consists of the kidneys, the bladder and some ducts (tubes).

Cortex

Medulla

Pelvis

Ureter

As urine is produced, it flows into the renal pelvis, then into theureter, to the bladder.

The kidneys work by filtering the blood and then absorbingback what the body needs to keep. The wastes are allowedpassed to the bladder, for storage and release.

Reabsorption

Filtration

Cortex

Medulla

Ureter

Pelvis

Some substances, especially potassium and hydrogen ions, are also secreted from the blood into the cortex region of the kidney!

Cortex

Medulla

Ureter

Pelvis

Urine is composed of water, urea, salt, and traces of other substances such as hormones.

The bladder stores the urine, which flows through the urethra to the outside.

Water is lost from the body through a number of ways:

Lungs – some water gets evaporated as we exhale

Skin – by evaporation from cells and through sweat.

Intestines – in the faeces (undigested food).

Kidneys – in the urine

Homeostasis – Water Levels in the Body

We have no control over the amount of water lost each day from the lungs, skin or intestines.

So the kidneys are the water control (osmoregulatory) organs of the body – conserving or eliminating water as the body requires.

– Identify Cortex, Medulla, Pelvis, Ureter

A = Cortex B = Medulla D = PelvisC = Ureter

A

B

C

D

LEARNING CHECK

– Identify Site(s) of Filtration and Reabsorption

Reabsorption

Filtration

Cortex

Medulla

Ureter

Pelvis

LEARNING CHECK

– Identify Site(s) of Filtration and Reabsorption

Reabsorption

Filtration

Cortex

Medulla

Ureter

Pelvis

LEARNING CHECK

Can you…

• Label the structure of the urinary system in humans

• Know the basis function of each of the following – kidneys, ureter, urinary bladder, urethra

• Describe the role of the kidney in regulating body fluids,

• Identify the site of filtration and reabsorbtion in the kidney.

• Describe the pathway of urine from the kidney to the urethra

By the end of today’s lesson you should be able to:

• Describe the nephron structure and it’s associated blood supply.

Higher level only

KIDNEY LS

The nephron.

H 3.4.8 The Nephron as a Unit of Kidney Function

The renal artery divides into afferent arterioles and then into a capillary network (glomerulus) at the top of each nephron.

Higher level only

1. Filtration

Blood enters the glomerulus under pressure which force filters the plasma into the lumen of Bowman's capsule

Higher level only

Everything except large proteins and blood cells goes into Bowman's capsule

The part of the blood that goes into Bowman's capsule is called the Glomerular filtrate.

Higher level only

2. Reabsorption

the glomerular filtrate passes from the Bowman's capsule into the proximal convoluted tubule where reabsorption of substances needed by the body takes place.

Higher level only

Glucose, amino acids, some salts and water are reabsorbed back into the blood by osmosis, diffusion and active transport.

Higher level only

As the filtrate passes into the Loop of Henly and distal convoluted tubule more water is reabsorbed.

Loop of Henle

Distal convoluted tubule

Higher level only

English, Theology, History, Philosophy

More water can be reabsorbed in the collecting duct - This is controlled by the hormone ADH and depends on how much water is in the blood.

Collecting duct

Higher level only

Everything that remains after reabsorption, is called the urine. It passes into the pelvis of the kidney, down the ureter and out into the bladder for storage.

Higher level only

ADH: Anti Diuretic Hormone

• When water levels in the body are too low then the hypothalmus in the brain releases ADH.

• If raised ADH levels in the blood are detected by the collecting duct more water will be reabsorbed back into the blood!

Higher level only

Adaptations of the nephron for absorption

1. The distal convoluting tubule, proximal convoluting tubule and loop of Henle walls are only one cell thick

1. The efferent arteriole is located very close to the distal convoluting tubule, proximal convoluting tubule and loop of Henle, – this makes it easier for substances to pass from the nephron into the blood vessels during reabsorption.

Higher level only