EXCRETION

1. The process by which metabolic wastes and excess substances are removed from an organism.

2. Excretion also removes excess heat from a body which helps keep the body temperature constant.

3. Excretion helps maintain homeostasis.

Metabolic wastes are:1. Carbon dioxide (CO2)

from cellular respiration2. Water

from cellular respiration and dehydration synthesis

3. Nitrogen compounds (ammonia, urea, uric acid) from the breakdown of amino acids

4. Mineral salts built up during metabolism

ELIMINATION (defecation)

• Removal of undigested or unabsorbed material in the form of feces from the digestive tract.

ADAPTATIONS IN THE FAB FIVE

EXCRETION IN PROTISTS

Wastes diffuse out of the cell through the cell membrane into surrounding water

Wastes include• Carbon dioxide• Mineral salts• Ammonia (is soluble in surrounding water)

Water constantly diffuses into the cell by osmosis• Requires active transport to pump excess

water out of the cell• Contractile vacuole fill with water• When full, they will inject water from the

cell

CONTRACTILE VACUOLES

PARAMECIUM

EXCRETION IN A HYDRA

Wastes diffuse out of the cells into the surrounding water

Wastes include:• Carbon dioxide• Mineral salts• Ammonia

Water constantly diffuses into the cells by osmosis

Water is pumped out by an unknown method of active transport– Contractile vacuoles have not been seen in

hydras

ectoderm

endoderm

CO2

O2

ammonia

Mineral salts

Gastrovascular cavity

THE

HYDRA

EXCRETION IN EARTHWORMS

Nephridia = the excretory organs of the earthworm• A pair of nephridia are in each section of the

earthworm’s body

Wastes from the body cells diffuse into the fluid of the body cavities

• Wastes from the body fluid enters the nephridia at the nephrostrome

• Fluid travels through the tubule loops and into the bladder

• The bladder drains to the outside of the body through an external opening called a nephridiopore

• Dilute solution called urine– Urine made up of water, mineral salts, ammonia, and

urea

EXCRETION IN EARTHWORMS

Wastes from the blood stream pass from the capillaries into the nephridium

Useful substances (glucose and water) pass from the body fluid to the nephridium to the blood

Carbon dioxide is excreted through the moist skin

EXCRETION IN EARTHWORMS

EXCRETION IN GRASSHOPPERS

Malpighian tubules = excretory organs of grasshoppers and insects

• The malpighian tubules are bathed directly by the blood in the open circulatory system

• Wastes and water from the blood move into the tubules by diffusion and active transport

• Wastes then pass into the intestines– Water and any useful materials are

reabsorbed back into the body fluids from the digestive tract

• Dry nitrogenous wastes (uric acid) pass out of the body through the anus with other digestive waste (feces)

EXCRETION IN GRASSHOPPERS

LUNG

4. SKIN

LIVER

KIDNEY

7. Adrenal gland

6. Ureter

5. Pelvis

4. Medulla

3. Cortex

2. Renal vein

1. Renal artery

8. Kidney

9. Ureter

10. Urinary bladder

11. Urethra

HUMAN URINARY SYSTEM

EXCRETION

Definition: The process by which wastes and excess substances are removed from an organism.

Role of the Liver

1. DETOXIFICATION

2. SECRETION OF BILE

3. FORMATION OF UREA

DETOXIFICATION

• removes harmful substances from the blood (bacteria, drugs, hormones)

• changes harmful substances to less harmful forms

• substances are returned to the blood and excreted through the kidneys

Cirrhosis – overloading of the body with toxins, the liver becomes overgrown with excess tissue and it decreases function, may eventually fail leading to death

DETOXIFICATION

Cirrhosis of the Liver

Cirrhosis – overloading of the body with toxins, the liver becomes overgrown with excess tissue and it decreases function, may eventually fail leading to death

Secretion of bile

• bile salts, cholesterol, hemoglobin molecule parts are secreted to the gallbladder (where they are temporarily stored)

• secreted to the small intestine where it assists in lipid digestion

• bile salts reabsorbed and returned to the liver• rest of materials pass to the large intestines are

excreted with fecesJaundice – if bile wastes are not excreted properly

and the hemoglobin is reabsorbed, the skin takes on a yellowish color

Secretion of bile

Jaundice

if bile wastes are not excreted properly and the hemoglobin is reabsorbed, the skin takes on a yellowish color

Formation of Urea

• amino acids (from protein digestion) are broken down in the liver

• each NH2 group changed into NH3 which is used to form urea

• urea in the liver diffuses into the blood that flows to the kidneys and is excreted as urine

Formation of Urea

ADRENAL GLANDS

KIDNEYS

INFERIOR VENA CAVA

AORTA

URINARY BLADDER

URETHRA

URETER

Function1. Kidneys (produce urine)

• Remove cellular respiration waste from the blood

• Regulate concentration of substances in body fluids

2. Ureter• Passage way from the kidneys to the bladder

3. Urinary bladder• Storage of urine

4. Urethra• Passage way for urine from the bladder to

outside the body

Structure of the KidneysI. Three parts of the kidney 1. Cortex – blood is filtered through the nephrons located here 2. Medulla – made up of collecting ducts that send the filtrate (filtered

material) to the pelvis 3. Pelvis – urine drains from here into the ureter

CORTEX 1.

MEDULLA 2.

PELVIS 3.

RENAL VEIN 4.

RENAL ARTERY 5.

URETER 6.

NEPHRONS

The filtering of wastes from the blood takes place in the nephrons.

Part of the structure is in the cortex and part is in the medulla.

NEPHRONS1. Glomerulus – tight ball of capillaries

where blood is filtered

2. Bowman’s Capsule – collects filtrate that has been filtered from the blood

3. Renal Tubule – passes filtrate from Bowman’s Capsule to the collecting duct

4. Loop of Henle – a loop of renal tubule

5. Collecting duct – one collecting duct receives filtrate from many different nephrons and drains it from the medulla

The Major Functional Unit of the Kidney is the Nephron

Bowman’s CapsuleCollecting Duct

Collecting Tubule

Capillary network Loop of Henle

Renal Vein

Renal Artery

Glomerulus

1. Bowman’s capsule

2. arterioles

3. renal artery

4. glomerulus

5. capillary network

6. renal vein

10. collecting tubule

9. collecting duct

7. venule

to pelvis

The Nephron

8. Loop of Henle

URINE FORMATION

1. FILTRATION

2. REABSORPTION

Filtration• Takes place in the glomerulus and the Bowman’s capsule

Bowman’s capsule

capillary

water *molecules are smallamino acids enough to pass through

urea the capillary to wall salts into Bowman’s capsule

*blood cells and proteins are too large to pass from the capillary to the Bowman’s capsule

URINE FORMATION

Urine FormationII. Reabsorption• While filtrate travels down the renal tubules, the volume of filtrate is

reduced• 99% of the water, all glucose and amino acids, and many salts are

passed back into the blood

renal tubulesWater is reabsorbed by osmosis

Other materials are reabsorbed by active transport

capillary

Filtrate left is highly concentrated (urine)Urine flows from the renal tubules to the collecting ductUrine passes from the kidneys into the ureters and on to the bladder

glucosewatera. a.salts

Control of kidney function• The kidneys are responsible for keeping

homeostasis, which is achieved by regulating the volume and concentration of body fluids; which is controlled by selectively filtering and reabsorbing materials from the blood.

The kidney has an auto-regulation mechanismo The rate of filtration and reabsorption

responds to changes in blood pressure and the composition of the blood

Control of kidney function

In other words; kidney function is controlled primarily by the composition of the blood.

The kidneys are also controlled by

The nervous system and hormonesoWhen cells in the hypothalamus (part of the

brain) are in a hypertonic environment (cells are losing water), they stimulate thirst.

oChanges in blood volume also stimulates receptors in the heart that in turn stimulate the release of certain hormones that affect the rates of reabsorption in the kidneys (therefore changing the blood volume)

• Substances that crystallize are called kidney stones

• If kidneys fail – artificial kidney function through dialysis

Kidney Stones

Kidney Dialysis

Structure of the Skin

NERVES

POREHAIR

EPIDERMIS

SEBACEOUS GLAND

KERATIN

HAIR FOLLICLE

SWEAT GLAND

DERMIS

Structure of the Skin

Epidermis• Tightly packed epithelia

cells• Deepest level made up of

rapidly dividing cells• As cells push up, they die

off• Produce keratin (tough,

waterproofing protein) for protection of the dermis

EPIDERMIS

Structure of the SkinDermis• Made of elastic, connective

tissue• Supports skin• Contains blood vessels, lymph

vessels, nerves, sense receptors, sebaceous glands (oil secretions), sweat glands (coiling tubes that open to pores), and hair follicles

DERMIS

Structure of the Skin

Adipose tissue

• A layer of fat

Adipose tissue

Functions of the Skin1. As a barrier

– Keeps microorganisms out– Keeps water in

2. Removal of heat– Increased blood flow to the surface of the

skin cools the blood– Sweat evaporates off the skin causing

cooling

3. Keeps the body warm– Decreased blood flow to the skin keeps the

core warm

The most important function of the skin

(as an organ of excretion)is

Removal of heat

primarily by sweating