Higher Human Biology Unit 23 The Continuation of

Higher Human Biology Unit 23: The Continuation of Life Chapter 23: Removal of Materials from the Blood. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 1

Learning Intentions To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood. 09/03/2021 Success Criteria 1. Describe the role of the liver in: I. Conservation of useful substances II. Detoxification of toxic materials III. Removal of bilirubin IV. Production of urea Mrs Smith Ch 22 The delivery of nutrients to cells 2

Removal of materials from the body The circulatory system is vital for the removal of materials from the body. The main organs that help remove unwanted materials are: The lungs 09/03/2021 The liver Mrs Smith Ch 23 The Removal of Materials from Blood The kidney 3

1. The Lungs Carbon Dioxide is a waste product of respiration CO 2 is transported to the lungs, via the blood plasma, to be removed from the body in the form of bicarbonate ions (HCO-3). As blood flows through the pulmonary system these bicarbonate ions combine with hydrogen ions (H+) to form carbonic acid (H 2 CO 3). An enzyme then breaks the carbonic acid down into water and CO 2: Concentration of CO 2 in blood plasma > Concentration CO 2 in air • So CO 2 diffuses out of the blood into the lungs down a concentration gradient. Breathing, which exhales air rich in CO 2, maintains this gradient. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 4

Diffusion in the alveoli 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 5

Excretion of carbon dioxide Excretion = the elimination of waste products of metabolism e. g. • Removal of CO 2 (waste product of respiration) at the lungs. • Release of bile pigment in bile. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 6

2. Role of Liver The liver removes materials from the blood by: • Conservation of useful substances. – e. g. glucose, plasma proteins • Detoxification of toxic materials which are potentially toxic. • Removal of bilirubin and its excretion as bile. • Production of urea. Liver maintains a stable internal environment, and provides cells with optimum conditions 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 7

Liver: Conservation of useful substances Glucose Level regulated • excess stored as glycogen which can be converted to glucose as needed. 09/03/2021 3 types of Plasma proteins Maintains a stable pool • some undergo deamination in the liver • meanwhile new molecules are synthesised Mrs Smith Ch 23 The Removal of Materials from Blood Components of blood plasma Regulated • Stable internal environment maintained • living cells have optimum conditions for growth & development 8

Detoxification of toxic materials • Certain substances which gain access to or are produced by the body as a result of metabolic reactions are potentially toxuc. • They would do the body harm if left unaltered. • These substances are detoxified by liver cells. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 9

Detoxification occurs in one of 4 ways • Substances are detoxified by liver cells in one of 4 ways…. . A. B. C. D. 09/03/2021 Chemical Alteration Chemical Breakdown Chemical attachment (conjugation). Uptake by macrophages Mrs Smith Ch 23 The Removal of Materials from Blood 10

A. Chemical alteration • Biologically active molecules (e. g. Drugs) are rendered inactive by being chemically altered in the liver. • The products are then excreted in bile or released into the bloodstream and removed by the kidneys. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 11

B. Chemical breakdown Hydrogen peroxide, a highly toxic by-product of metabolism is broken down by the enzyme catalase into harmless substances. Liver cells are rich in catalase. 2 H 2 O 2 TOXIC 09/03/2021 catalase 2 H 2 O + O 2 Harmless Mrs Smith Ch 23 The Removal of Materials from Blood 12

B. Chemical breakdown • Alcohol (ethanol) gets converted in the liver, by a series of enzyme –controlled steps to acetyl Co. A, which acts as a respiratory substrate for aerobic respiration. • Too much alcohol damages cells. Regular consumption of alcohol to excess can cause permanent liver damage leading to a fatal liver condition called cirrhosis. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 13

C. Chemical attachement • Some unwanted substances (e. g. Certain types of food preservative) become attached to liver cells to the amino acid glycerine. • This acts as a molecular label which is recognised as waste by the kidneys and excreted. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 14

D. Uptake by macrophages • Foreign particles are removed by macrophages (phagocytic cells) which line the liver’s blood vessels. • If for example an animal is injected intravenously with a suspension of carbon particles, samples of liver obtained only minutes later show numerous carbonladen macrophage cells. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 15

Liver: Detoxification of Materials: SUMMARY Toxic substances, that have either been eaten or produced in metabolic reactions, must be destroyed to prevent them harming the body. Liver cells detoxify such substances. Detoxification by liver cells Chemical alteration Biologically active molecules altered in the liver. Products excreted in bile or released into blood and removed by kidneys Chemical attachment (conjugation) Unwanted substance become attached by liver cells to the amino acid glycine. This acts as a chemical label which is recognised as a waste by the kidneys and excreted Uptake by macrophages Macrophages line the liver’s blood vessels removing foreign particles Chemical breakdown 16 (see next page)

Learning Intentions To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood. 09/03/2021 Success Criteria 1. 3. Describe the role of the liver in: I. Conservation of useful substances II. Detoxification of toxic materials III. Removal of bilirubin IV. Production of urea Mrs Smith Ch 22 The delivery of nutrients to cells 17

3. Removal of bilirubin When red blood cells reach the end of their 120 day life span, they are destroyed by macrophage cells in the liver, bone marrow and spleen, Haemoglobin is broken down by theses cells into a yellow pigment called bilirubin. Biliruben is releases into the blood giving blood plasma its yellowish colour. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 18

Excretion of bilirubin Bilirubin molecules, removed from the blood plasma by the liver, are added to bile with the aid of enzymes and become bile pigment (Conjugated bilirubin). This has no useful role in digestion so is released in bile. In the gut, bilirubin is converted by bacteria to the brown pigment that gives faeces its brown colour. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 19

4. Jaundice Bilirubin accumulates in the bloodstream when: • Liver cells can’t absorb bilirubin (due to illness e. g. hepatitis). • The bile duct becomes blocked preventing the release of bile to small intestine. • Red blood cell destruction is excessively high. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 20

4. Jaundice is caused by excessively high concentrations of bilirubin. Baby’s can be screened for Bilirubin using a light meter that is placed on the baby’s head. 09/03/2021 21

Learning Intentions To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood. 09/03/2021 Success Criteria 2. Determining the quantity of urea in urine samples Mrs Smith Ch 22 The delivery of nutrients to cells 22

Production of Urea: Deamination • Unlike carbohydrate and lipid, protein is not stored in the body. Excess amino acids are absorbed from the gut then undergo deamination in liver cells. • De-amination needs oxygen • It produces an organic acid • It produces ammonia which goes to the ornithine cycle. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 23

5. Production of urea During this process, the amino acid is broken down to form ammonia and an organic acid. Organic acid (Kreb cycle intermediate or pyruvic acid) Used for energy release in respiation Breakdown of amino acids Ammonia Passes into blood and leaves the liver by the hepatic vein. It is removed from the blood at the kidneys. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood + CO 2 Very toxic Urea Less toxic + H 2 O 24

Fate of deaminated amino acids • Depending on which amino acid has been deaminated the organic acid may be pyruvic acid or one of Krebs Cycle intermediates. • It can then enter the respiratory pathway or be used for energy release. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 25

Ornithine cycle • Since ammonia is formed during deamination of an amino acid is highly toxic, it is immediately passed to the ornithine cycle. • This cycle is controlled by enzymes in the liver cells. • Here Ornithine is constantly regenerated. • During this cycle , ammonia reacts with carbon dioxide to form less toxic urea and water. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 26

Urea production • During the conversion of ammonia into urea, two molecules of ammonia and one molecule of carbon dioxide combine to form one molecule of urea and one of water. Assisting this process there is a cyclical conversion of ornithine into citrulline, arginine, and then back to ornithine again. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 27

Where does the urea go? • Urea is then passed into the bloodstream and then leaves the liver by the hepatic vein. • It is removed from blood by the kidneys. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 28

Determining the quantity of urea in ‘urine’ samples The combination of urea with water is catalysed by the enzyme urease: Urea + H 2 O urease ammonium carbonate (an alkali) The quantity of urea in the original solution is directly related to the quantity of alkali produced. This can be determined by the volume of acid needed to neutralise the alkali. Methyl orange, an indicator, is used to show the change from alkali (orange) to acid (red). 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 29

Using solutions of known concentration to plot a calibration graph Using urea solutions of known concentration a calibration graph can be drawn. • Four solutions of know urea concentration are made up. • Following enzyme activity at 37 o. C, each solution is titrated against hydrochloric acid. • The volume of hydrochloric acid needed to neutralise the alkali in each solution is indicated by methyl orange changing colour. • This is repeated for each conc many times and results are pooled and averaged. • The results are then plotted to make a calibration graph. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 30

Urea Concentration Calibration Curve 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 31

Using a calibration graph to calculate the urea content of unknown samples The following experiment is carried out on a sample of urine (urea concentration unknown) and compared to the calibration curve. Many repeats done to increase reliability of results. to increase surface area to aid mixing of enzyme & substrate + 2 crushed urease tablets o In water bath at 37 C for 90 mins Flasks shaken at 15 min intervals Optimum temperature for enzyme activity 50 cm 3 urea solution (urea + water) 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood After 90 mins, 20 drops of methyl orange added + 0. 1 M HCl until indictor turns red 32

Task: Torrance-TYK pg 178 Qu 1 -3 09/03/2021 Mrs Smith Ch 20: Transport Mechanisms - The Cardiac Cycle 33

Learning Intentions To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood. 09/03/2021 Success Criteria 4. Label a diagram of a kidney nephron 5. Explain the mechanism of kidney function to include I. Ultrafiltration Mrs Smith Ch 22 The delivery of nutrients to cells 34

6. Structure of the Kidney 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 35

6. The Kidneys: Structure Each kidney has about a million tiny filtering units called nephrons. 09/03/2021 36

Each nephron is composed of several part glomerulus Bowman's capsule nephron blood capillaries collecting duct The capillaries in the glomerulus are narrower than the capillary that supplied it with blood. What effect will this have 37 on the blood pressure in the glomerulus?

Nephrons • Each nephron is composed of several parts. • A glomerulus is enclosed in a cup-shaped Bowman’s capsule which leads into a long kidney tubule surrounded by a dense network of blood capillaries. • Two regions of the tubule possess several twists and turns and are therefore described as convoluted. The proximal convoluted tubule is the twisted region at the greater distance from the Bowman’s capsule. • The long, U-shaped stretch of tubule between the convoluted regions is called the loop of Henle. • Each kidney tubule leads to a communal collecting duct. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 38

The Kidney Nephron Knot of tiny blood vessels The blood enters the nephron via the renal artery and leaves via the renal vein. At the glomerulus the blood is filtered and the filtrate gathers in the bowman’s capsule. The filtrate then passes along the tubule to the communal collecting duct. 09/03/2021 Has many twists & turns Bowman’s capsule Loop of Henle 39

The Kidneys: Function: Production of Urine • The kidneys remove waste material from the blood and excrete them in urine. • The production of urine involves the – ultrafiltration of blood – reabsorption of useful materials from the filtrate. • Since urine contains urea, a nitrogenous waste, the kidneys are described as organs of nitrogenous excretion. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 40

7. Ultrafiltration • Ultrafiltration happens at the Bowman’s capsule. • Blood containing waste products enters the kidney by the renal artery which divides into about a million branches each supplying a glomerulus. • Each glomerulus consists of a coiled knot of blood capillaries. This arrangement enables a large surface area of blood vessel to be in contact with the inner lining of the Bowman’s capsule. • It is at this interface ultrafiltration takes place 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 41

09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 42

Ultrafiltration- Basement membrane filter. The layer of cells which makes up the capillary wall of a glomerulus differs from a normal capillary because. . . • It has pores which are large enough to let ALL the substances within plasma pass through. • The porous layer is attached to a highly permeable thin layer of non-living material called the basement membrane. • The basement membrane has no pores but acts as a filter that. . . – Allows small molecules such as glucose, water, salts & urea to pass through. – Prevents large molecules of plasma protein from leaving the blood stream. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 43

Protein molecules pass through the fenestrated endothelial layer of the capillaries, but are prevented from passing into the cavity of Bowman’s capsule by the basement membrane glucose water ions protein 09/03/2021 urea Mrs Smith Ch 23 The Removal of Materials from Blood 44

Blood Pressure • Plasma proteins which remain in the blood plasma tend to draw water back from the filtrate in the capsule by osmosis. • In addition filtrate already present in the capsule tends to resist the delivery of further filtrate into the capsule. • Successful ultrafiltration of blood depends on the blood in the glomeruli being at high enough pressure to overcome both of these factors and force filtrate out of the plasma. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 45

Ultrafiltration and Blood Pressure. • High blood pressure in the glomerulus is needed to force the filtrate out of the blood plasma. This is maintained because: – The blood vessels leading to the glomerulus come from the renal artery, which is a branch from the aorta so carries blood at high pressure – The blood vessels entering the glomerulus are wider than the blood vessels leaving it, causing a bottleneck and the blood to be squeezed Did you know? An adult has ~ 4. 5 l of blood, but the kidneys filter ~ 1500 l of blood/day! 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 46

Ultrafiltration – Rate of production of filtrate and urine. • A human adult contains about 4. 5 litres of blood. • During its continuous circulation round the body, blood repeatedly enters the kidneys and undergoes filtration. • Each day a human adult’s kidneys filter a total volume of around 1500 litres of blood and produce about 180 litres of glomerular filtrate. • However the production of urine is only about 12 litres. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 47

Learning Intentions To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood. 09/03/2021 Success Criteria 5. Explain the mechanism of kidney function to include II. Re-absorption Mrs Smith Ch 22 The delivery of nutrients to cells 48

8. Reabsorption About 180 l of glomerular filtrate is produced every day but only 1 -2 l of urine is produced, because ~ 99% of the water in the filtrate is reabsorbed into the bloodstream. Apart from the plasma proteins and water, the chemicals in blood plasma and glomerular filtrate are very similar. Reabsorption occurs at various points along the tubule that come into contact with the blood capillaries. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 49

A. Reabsorption of Salts: Proximal convoluted tubule Glucose & amino acids absorbed by epithelial cells lining the tubule. 90% Sodium ions (Na+) from glomerular filtrate actively pumped across epithelial cells, as they are combined with Chloride (Cl-) ions in the form of salt, they to pass into the blood 09/03/2021 50

Diffusion Active transport Facilitated diffusion Sodium ions in the lumen of the proximal convoluted tubule 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 51

A. Reabsorption of Water: Proximal convoluted tubule Water The active transport of glucose, sodium ions (and other solutes such as amino acids) into the blood stream reduces the blood plasma's concentration relative to that of the glomerular filtrate. Water therefore passes into blood by osmosis. This movement of water is a form of passive transport and does not require energy. About 85% of water is reabsorbed from the proximal convoluted tubule. 09/03/2021 52

09/03/2021 The transport of glucose, amino acids and ions into the epithelial cells creates a gradient of water potential across the lining of the tubule; water is Mrs Smith Ch 23 from The Removal of therefore withdrawn the tubule by osmosis, Materials from Blood such that approximately 85% 53

Reabsorption of Glucose : Proximal convoluted tubule Epithelial cells are structurally suited to their function: Many microvilli for large surface area Many mitochondria to provide energy for active transport (of glucose) Carrier molecules carry glucose across cell membranes 09/03/2021 Image source: people. eku. edu 54

interstitia l fluid lume n epithelial cells microvilli intercellula r spaces 09/03/2021 many mitochondri Mrs Smith Ch 23 The Removal of Materials a from Blood 55

Diabetes Untreated sufferers of diabetes mellitus have so much glucose in their blood plasma that some of the glucose in the glomerular filtrate is not reabsorbed by the epithelial cells of the proximal convoluted tubules. This is excreted in urine. 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 56

B. Reabsorption: Loop of Henle • Each U-shaped loop of Henle lies in the medulla • Consists of a descending limb and an ascending limb • At the descending limb – Water is reabsorbed back into the bloodstream by Osmosis – Salts are not reabsorbed here • At the ascending limb – water is not reabsorbed as the thick wall of the tubule is impermeable to water – Salts are pumped out of the filtrate into the tissue fluid This creates a low water concentration by high solute concentration 57

C. Reabsorption: Distal convoluted tubule Sodium chloride (salt) is reabsorbed from the distal convoluted tubule by being actively pumped into the bloodstream, but in smaller quantities. Water also passes from the distal convoluted tubule into the bloodstream 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 58

D. Reabsorption: Collecting Duct Because the medullary tissue fluid has a low water concentration (due to the action at the ascending limb of the loop of Henle) the kidney tissues can reabsorb lots of water by osmosis from the collecting ducts. The volume of water needed to return the bloods water concentration to normal is reabsorbed from the filtrate. The rest is passed out in the urine. 09/03/2021 59

D. Reabsorption from Collecting Duct is controlled by the hormone ADH Image source: www. uic. edu No ADH Present - Collecting Duct is NOT permeable to water and large volume of urine is produced 09/03/2021 ADH Present - Collecting Duct is permeable to water and a small volume of urine is produced Mrs Smith Ch 23 The Removal of Materials from Blood 60

Reabsorption – Summary • Proximal convoluted tubule – Glucose – Salt (Sodium+Chloride ions) – Water Active Transport Osmosis • Descending Loop of Henle – Water Osmosis • Ascending Loop of Henle – Salts (Sodium+Chloride ions) Active Transport • Distal Convoluted Tubule – Salts (Sodium+Chloride ions) – Water 09/03/2021 Active Transport Osmosis 61

Learning Intentions To understand how the liver, lungs and kidneys are involved in the removal of materials from the blood. 09/03/2021 Success Criteria 6. Analyse data on glomerular filtrate, tubule fluid and urine composition and rates of production Mrs Smith Ch 22 The delivery of nutrients to cells 62

Role of ADH Water content of blood too low Salt eaten or much sweating Brain releases much ADH Too much water drunk Water content of blood normal High volume of water passes into blood High volume of water reabsorbed by kidney Small volume of concentrated urine 09/03/2021 passed to the bladder Water content of blood too high Brain releases little ADH Low volume of water passes into blood High volume of dilute urine passed to the bladder Low volume of water reabsorbed by kidney 63

ADH and Osmoregulation The volume of water reabsorbed varies greatly. This is regulated by the concentration of anti-diuretic hormone (ADH) present in the bloodstream. ADH increases the permeability to water of the distal convoluted tubules & collecting ducts. Regulation of Blood Water Concentration 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 64 Image source: www. bbc. co. uk

ADH and Osmoregulation High Water Concentration • When the water concentration of the blood is high, very little ADH is released into the blood stream from the pituitary gland. • The distal convoluted tubules and collecting ducts remain practically impermeable to water and almost none is reabsorbed from these regions of tubule. • A large volume of dilute urine is therefore. produced 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 65

ADH and Osmoregulation Low Water Concentration • When the water concentration of the blood is low, the situation is reversed and a small volume of concentrated urine is produced. • This mechanism allows the kidneys to plat an osmoregulatory role in the maintenance of the body’s internal steady state. (more in chapter 24) 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 66

Task: Torrance-TYK pg 183 Qu 1 -3 09/03/2021 Mrs Smith Ch 20: Transport Mechanisms - The Cardiac Cycle 67

Task: Torrance AYK pg 184/185 Qu’s 1 -6 09/03/2021 Mrs Smith Ch 19 The need for transport 68

Essay Questions: SQA 2005 Describe the function of the liver under the following headings i. Production of urea. (2) ii. Metabolism of carbohydrates. (5) iii. Breakdown of red blood cells. (3) 09/03/2021 Mrs Smith Ch 19 The need for transport 69

Guide to ‘H’ Grade Essays Essay 35 pg 83 Discuss the role of the liver under the following headings i. Metabolism of protein. (5) ii. Detoxification. (5) iii. Conservation of useful substances (5) 09/03/2021 Mrs Smith Ch 19 The need for transport 70

Guide to ‘H’ Grade Essays Essay 35 pg 83 Give an account of the role of the kidneys with reference to the following: i. Ultrafiltration. ii. Reabsorption. 09/03/2021 (8) (7) Mrs Smith Ch 19 The need for transport 71

TASK: Match the correct word with its meaning on each page! 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 72

Word Meaning Kidney Carries unpurified blood to the kidney Renal artery Carries purified blood away from the kidney Renal vein Chemical messenger Ureter Carries urine from the kidney to the bladder Bladder Gland that releases ADH Urethra Stores urine ADH Carries urine out of body Hormone Organ that filters the blood Pituitary gland Hormone that regulates water balance 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 73

Word Meaning Network of very thin blood vessels Glomerulus U-shaped kidney tubule that reabsorbs water into the Bowman’s capsule bloodstream Tiny knot of blood capillaries in Blood capillaries the Bowman’s capsule where filtration of the blood occurs Nephron Cup-shaped structure that collects glomerular filtrate from the blood Loop of Henle Tiny filtering unit in the kidney 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 74

Word Meaning Waste liquid excreted by the body Tube that carries urine away from Collecting duct several kidney tubules Nitrogen containing waste product Dialysis made in the liver from surplus Glomerular filtrate amino acids Fluid produced from filtration of Urine the blood in a glomerulus Artificial filtration of blood Urea through a selectively permeable membrane to remove waste products 09/03/2021 Mrs Smith Ch 23 The Removal of Materials from Blood 75