Objectives

The Excretory System in the Human

Explain the role of the excretory system in homeostasis the ability and necessity to maintain constancy of body temperature, fluid balance and chemistry.State the function, location, products of the skin/lungs/urinary system.

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

humans.

Outline the basic macrostructure & function for the urinary excretory system - Kidney/Ureters/Urinary Bladder/Urethra

Explain the role of Kidney in regulating body fluids.

Describe the processes of filtration , reabsorption and excretion in the medulla & renal pelvis.

Describe pathway of urine from kidney to urethra

Excretion is the removal of metabolic waste from the body

Metabolism is the sum of all the chemical reactions in an organism

Excretion is one of the 7 characteristics of living things (MRS NERG)

Plants do not have the same need for excretion as animals. Some of their wastes are stored in vacuoles. Some stored waste is lost when plants lose their leaves, bark, seeds etc.

Stomata & Lenticels

Plants lose water and oxygen. Water and oxygen are lost through the stomata on the under surface of leaves during the day and the lenticels on stems.

At night plants lose carbon dioxide through their stomata and lenticels

Homeostasis

Homeostasis is the maintenance of a constant internal environment in an organism.

Homeostasis means that humans maintain a constant temperature (37C), fluid balance etc.

Temperature regulation in animals

It is important to maintain a constant temperature because temperature regulates enzyme controlled reactions in the body.

Animals use 2 methods to control their temperature:

1. Ectotherms: Gain or lose heat from or to their external environment (cold blooded animals) e.g. fish and frogs

2. Endotherms: Generate their

own heat from metabolic reactions (warm blooded animals) e.g. birds and

mammals

Temperature regulation in humans

The skin plays a major role in temperature regulation in humans

It consists of 2 layers

1. Outer epidermis

2. Inner dermis

Beneath these layers is subcutaneous tissue which contains adipose tissue

Epidermis

1. Malpighian layer – cells are constantly dividing by mitosis to produce new epidermis cells

2. Keratin is a waterproof layer on the surface of the skin

3. Specialised cells in the malpighian layer produce a coloured pigment called melanin which gives colour to skin (freckles and moles occur where melanin is quite concentrated)

The SKIN

4. Melanin protects skin against UV light. DermisConsists of connective tissue containing a tissue called

collagen. It contains a variety of structures e.g. nerve receptors,

sweat glands etc. Functions of Skin1. Protection

– The epidermis protects the body and acts as a barrier against entry of pathogens.

- Dermis – protects internal organs- Melanin – protects skin from harmful UV light

2. Vitamin production Vitamin D is produced in the skin in following exposure to UV light. Vitamin D helps intestine absorb light.

3. Food StoreFat is stored in the adipose tissue

4. Sense OrganSkin has a variety of receptors e.g touch and hot/cold receptors

5. Excretion Sweat glands in the skin secrete water and salts form the body.

6. Temperature regulationa) In cold conditions the skin helps retain heat by

1. Erector muscles contract forming goose bumps and this causes hairs to stand on end and trap a layer of warm air that reduces heat loss from body.2. Blood vessels contract(vasoconstriction) and thisreduces heat loss fromthe skin. 3. Muscles relax and contract very rapidly and we shiver which Produces heat to raise our body temperature

b. In warm weather we reduce our temperature by 1. producing sweat and when this water evaporates it cools down our skin. (in normal weather we can lose about 1 litre of sweat per day). 2. When we get too hot blood vessels in our skin expand (dilate) and come near the surface of the body. This increases heat loss from the body and cools us down. Our faces turn red.

Controlling body temperature

Body temperature is controlled by the thermo-regulatory centre in the ________. It is kept at 370C as this is the best temperature for __________ to work in. If the body becomes too hot then blood vessels _________ and sweat glands release ________. If the body is too ______ then blood vessels constrict and muscles start to __________.

Words – sweat, enzymes, cold, dilate, shiver, brain

Quiz

LEARNING CHECK

• What is an endotherm?

• What is an ectotherm?

• List the functions of the skin.

• What is our normal body temperature?

• What happens when we get too hot ?

• What happens when we get too cold?

• What part of the brain detects changes in our temperature?

Excretion & Homeostasis

Role of excretory system in homeostasis

1. Regulates body temperature

2. Controlling osmosis

3. Controlling concentration of body fluids.

4. Removing wast products of metabolism from the body.

Organs of excretion

1.Lungs – excrete water and carbon dioxide

2.Skin – excretes water & salts as sweat

3.Kidneys – Main excretory organ in humans. They excrete water, salts and urea in the form of urine.

OUR EXCRETORY SYSTEM

Quiz

• What is excretion?

• What role does excretion play in homeostasis in the body?

• Name the main waste products of the body.

• Name the main excretory organs of the body.

The Urinary System

Consists of:

2 kidneys

Two ureters

The Bladder

The Urethra

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

Kidneys are:

Fist sized organs located just below the diaphragm in the small of the back.

Kidney bean shaped with a depression called the hilium

Blood from the Aorta enters the kidney through 2 renal arteries

Every minute about 20% of our blood passes into the kidneys

Cleaned blood leaves the kidneys through the renal vein into the vena cava

A section through the kidney shows an outer darker region(cortex) and a lighter inner zone (medulla).

Cortex

Medulla

Pelvis

Ureter

– Identify Cortex, Medulla, Pelvis, Ureter

A = Cortex B = Medulla D = PelvisC = Ureter

A

B

C

D

Quiz

KIDNEY LS

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 allowedpass to the bladder, for storage and release.

Reabsorption

Filtration

Cortex

Medulla

Ureter

Pelvis

1. Filtration—In the outer cortex, small molecules like glucose,amino acids, water, urea and salts filter out of the blood intonarrow tubules.

2. Reabsorption—blood vessels reabsorb back useful nutrients from the tubules. Urea, excess salts and water, are allowed to continue down the tubule and on to the bladder.

3. Secretion is the production and release of chemicals from cells.

Some substances, especially potassium and hydrogen ions, are secreted from the blood into the tubule in the cortex region.

When the blood becomes too acidic, hydrogen ions are secreted into the urine.

By controlling the hydrogen ion concentration in the blood, the kidneys control blood pH.

3. Urine is composed of about 96% water, urea, salt, and traces of other substances such as hormones.

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

– Identify Site(s) of Filtration and Reabsorption

Reabsorption

Filtration

Cortex

Medulla

Ureter

Pelvis

Quiz

LEARNING CHECK

• What is filtration?

• What is reabsorption?

• What is secretion?

• What is the difference between the kidney and the bladder?

• What is urine?

Being a land animal, we have a continuous need to conserve water.

Water must be taken in daily and its loss must be carefully regulated.

Water is taken in as food and drink, and is also formed inside the cells during some reactions, especially respiration.

Homeostasis – Water Levels in the Body

Water is lost from the body through our lungs, skin, intestines and kidneys.

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

Lungs – some water gets evaporated as we exhale from our warm, damp lungs.

Skin – by evaporation from cells and through sweat.

Intestines – in the faeces (undigested food).

Kidneys – in dissolving the poisons and wastes we wish to excrete from 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.

LEARNING CHECK

• Name the ways we gain water.

• Name the ways we lose water.

• What is osmoregulation?

Functions of the Kidney1.Excretion – Kidney removes waste products from the blood stream and changes them to urine. 2.Osmoregulation – Kidneys control water content of the body.3.Salt Concentration – Kidneys control the salt concentration of body fluids e.g. blood. If we eat too much salt the kidney will increase the salt content of our urine.4.pH Control – Kidneys control the pH of body fluids e.g. blood. Normal pH of blood is 7.4