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.
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
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
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 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)
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.
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
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
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
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
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
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
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