Fifth Year Biology Excretion Miss Rochford
In this Topic Excretion in plants Excretion and homeostasis Skin Organs of excretion Urinary system Kidneys Nephron Control of urine volume
Characteristics of living things 1. Nutrition 2. Respiration 3. Excretion 4. Growth 5. Reproduction 6. Movement 7. Response
Excretion Excretion: the removal of metabolic waste from the body Examples of waste: Carbon Dioxide Sweat Urea
EXCRETION IN PLANTS
Excretion in Plants Plants make their own food No surplus produced, so waste is reduced They recycle compounds within the plant: Photosynthesis Oxygen Respiration Respiration CO 2 and H 2 O Photosynthesis
Excretion in Plants Plants also store waste: Vacuoles in living cells Within dead cells Oxygen and water are the main substances excreted by plants Excreted mainly through stomata, but also through lenticels
Excretion in Plants Lenticels: small pores on a stem that function in gas exchange Stomata: openings on the underside of leaves
EXCRETION AND HOMEOSTASIS
Excretion and Homeostasis Homeostasis: the ability of an organism to maintain a constant internal environment
Excretion and Homeostasis Role of the Excretory System in Homeostasis Temperature is regulated using sweat Blood water concentration is controlled Toxins are removed
THE SKIN
Epidermis Epidermis = outer layer of skin Malpighian layer Contains melanin (skin pigment) Constantly dividing by mitosis Produces new epidermis cells Pushes new cells through granular layer
Epidermis Cornified layer New cells push through the granular layer and produce a waterproof protein called keratin Keratin builds up and the cells become hardened or cornified
Made of: Dermis Dermis = inner layer of skin connective tissue containing collagen (a strengthening protein) Sweat glands Hair follicles Sebaceous glands Blood vessels Nerve receptors
Skin Functions: Protection Epidermis Dermis Melanin Sebum A barrier preventing water loss and entry of pathogens Protects internal organs from damage (bumps and bangs) Protects from UV radiation Keeps hair moist and flexible Keeps skin moisturised
Other Skin Functions Vitamin D Production Food store Sense organ Excretion Produced by skin following UV radiation exposure Fat in adipose tissue is a food store A variety of receptors allow sensations of touch, pain and temperature Sweat glands excrete water and salts as sweat
Skin: Temperature regulation
ORGANS OF EXCRETION
Organs of Excretion LUNGS Excrete waste products of respiration o Carbon dioxide o Water vapour
Organs of Excretion SKIN Excretes: o Water o Salts These substances make up SWEAT
Organs of Excretion KIDNEYS Excrete: o Water o Salts o Urea These substances make up URINE
Organs of Excretion: Summary Organ Lungs Kidneys Skin Substance(s) excreted Carbon dioxide Water vapour Water Salts Urea Water Salts
THE URINARY SYSTEM Function of Urinary System To make and excrete URINE
Parts of the Urinary System Renal arteries Carry blood TO the kidneys Blood contains: Excess water Excess salts Urea
Parts of the Urinary System Kidneys Remove excess water, salts and urea from blood
Parts of the Urinary System Renal veins Carry blood AWAY from the kidneys to the heart Blood contains: NO waste
Parts of the Urinary System Ureters Carry urine from the kidneys to the bladder
Parts of the Urinary System Bladder Stores urine Urethra Carries urine from the bladder out of the body
Bladder Not under voluntary control Has 2 sphincter muscles at junction of bladder and urethra Babies have no control over these Control of urination = control of the sphincter reflex
Renal Artery: Entry of blood with waste and excess water Renal Vein: Exit of clean blood (without salts, waste or excess water) The Kidney FILTERS the blood, removing salts, urea and excess water Ureter: Exit of urine (formed from water, salts and urea)
Main processes of the kidneys
Main processes of the kidneys Filtration In the outer cortex of the kidney Small substances pushed out of blood into the kidney Reabsorption In the cortex and medulla of the kidney Useful materials are taken back into the blood
Main processes of the kidneys Secretion Substances like potassium and hydrogen ions are secreted from blood into the kidney cortex Controlling hydrogen ions, controls ph Too much potassium leads to nerve impulse problems
Water (96 %) Urine Nitrogenous waste (2.5 %, mostly urea) Salts (1.5 %) Made of: Urine flows from the medulla into the renal pelvis Gets carried into the ureter Ureter brings it to the bladder
Functions of the Kidneys Excretion Water content Salt content ph control Waste products are removed and excreted as urine Water content of urine is controlled & depends what is needed Salt content of urine is controlled & depends what is needed By controlling levels of hydrogen ions, blood ph may be controlled
THE NEPHRON
The Nephron
The Nephron Nephron: functional units of the kidney that make urine Each kidney has > 1 million nephrons They are tubes about 3 cm long Found in the cortex and medulla
The Nephron: Blood Flow Renal Artery Capillaries Afferent Arterioles Renal Venules Glomerulus Renal Veins Efferent Arteriole
The Nephron: Blood Flow Renal Artery Renal Arterioles Glomerulus Efferent arteriole Capillaries Renal Venules Renal Vein Branches into renal arterioles Each divides into a cluster of capillaries Found in each Bowman s capsule Divides to form capillaries Re-join to form renal venules Combine and leave kidney Main vessel exiting the kidney
The Nephron: Urine Production Urine is produced in the nephron Three main processes are involved in urine production: 1. Filtration 2. Reabsorption 3. Secretion
Urine Production: Filtration Afferent arteriole blood contains waste Filtration happens in the glomerulus Small molecules are forces out into the Bowman s capsule (e.g. glucose, amino acids, vitamins, urea, salts, water) They form a dilute solution called glomerular filtrate
Urine Production: Filtration How the Glomerulus structure helps filtration Higher pressure than normal blood pressure Large surface area increases area for filtration Capillary walls are porous Bowman s capsule walls are only one cell thick Not in the filtrate: Red white blood cells White blood cells Platelets Antibodies, Clotting proteins Some hormones
Urine Production: Reabsorption Proximal convoluted tubule Most of the water reabsorbed by osmosis All useful molecules reabsorbed by diffusion & active transport Glucose, amino acids, vitamins Salts reabsorbed by diffusion & active transport Proximal tubule adaptations for reabsorption: Long (14 cm) and thin-walled (one cell thick) Large surface area High concentration of mitochondria for energy
Urine Production: Reabsorption Descending limb loop of Henle Permeable to water A small amount of water is reabsorbed by osmosis Some minerals are also reabsorbed
Urine Production: Reabsorption Ascending limb loop of Henle Permeable to salts Salts move out of the nephron into the medulla fluid Starts as diffusion but is by active transport at the top of the limb The medulla is now more concentrated than tubule fluid This helps with osmosis
Urine Production: Reabsorption Water and salt reabsorption
Urine Production: Reabsorption Distal Convoluted Tubule Delicate and precise control of water, salt and ph values of blood If needed, water and salts can be reabsorbed into the blood here Collecting Duct Water permeable so a small amount of water is reabsorbed by osmosis Liquid in the duct = Urine Urine flows to the pelvis of the kidney and out through ureters
Urine Production: Secretion Distal Tubule ph of the blood maintained by secretion of: Potassium ions (K + ) Hydrogen ions (H + )
Summary of Nephron Functions Region Substances reabsorbed Proximal convoluted tubule Most salts, glucose, amino acids, vitamins Loop of Henle (descending) Some minerals Water reabsorption Most A little Loop of Henle (ascending) Some salts None Distal convoluted tubule Some salts Some Collecting duct None A little
Summary of Nephron Functions
Glomerular Filtrate vs Urine How is glomerular filtrate different to urine? 1. It has more water 2. It contains many useful molecules not usually found in urine Glucose Amino acids
CONTROL OF URINE VOLUME
Anti-Diuretic Hormone (ADH) Also known as Vasopressin It is a hormone that controls urine production Produced in the hypothalamus and stored in the pituitary gland When needed, it is sent into the bloodstream Affects the distal convoluted tubule and collecting duct More water is reabsorbed by the nephron
Homeostasis: Water levels
Control of Urine Volume
Chapter 31: Excretion DONE!!