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Biology 20 Excretion General, Structure & Function,

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Presentation on theme: "Biology 20 Excretion General, Structure & Function,"— Presentation transcript:

1 Biology 20 Excretion General, Structure & Function,
Four Steps to Urine Formation Hormones, Composition of Urine

2 Introduction Humans are 70% water
1/3 of this is in plasma Blood – carries nutrients, picks up waste Wastes need to be removed Composition of fluids need to be kept in balance Excretion: monitor, analyze, select, reject

3 EXCRETION Excretion is the process of removing metabolic wastes from the body. During the metabolic processes of the body, waste products are removed from the site of production by the blood. As these wastes accumulate, the kidney removes them from the blood and excretes them to the environment. The excretory product becomes urine.

4 Excretion Process of removing cellular waste Balance pH of blood Maintain water balance Happens in Kidney

To maintain homeostasis Regulates and stabilise the internal environment by controlling 4 groups of chemicals Water: Excretion of metabolic wastes: Elimination of poisonous by-products of chemical reactions: Osmoregulation fluid and salt regulation: regulation of hydrogen, sodium, potassium, calcium, chloride ions: Regulation of body fluid composition: Removal of essential nutrients that dangerous in excess:

6 WASTE PRODUCTS The principle metabolic wastes in most animals are:
Carbon Dioxide – is excreted through the respiratory surfaces Water – excreted through respiratory surfaces, skin as sweat as well as kidneys Nitrogenous Wastes – products of protein and nucleic acid digestion

7 Carbon Dioxide Water Waste Products Nitrogen Wastes

8 NITROGENOUS WASTES Ammonia – The first metabolic product of amino acid deamination – hydrolysis (protein digestion) highly toxic cannot accumulate in body must be converted into less toxic uric acid and urea Uric Acid – produced from ammonia not very soluble – can be excreted as a paste with little water loss non - toxic

9 Deamination & Urea Proteins – contain a nitrogen molecule
Amino acid – building blocks of protein Nitrogenous base Removal of N and H Occurs in the liver Byproduct – ammonia Toxic substance Ammonia combines with CO2 to form urea Urea –less toxic Uric acid – waste product from the breakdown of nucleic acids (DNA)

10 NITROGENOUS WASTES Urea – converted from ammonia
less toxic than ammonia produced in the liver can be excreted in concentrated form requires more water to excrete than uric acid

11 Urinary System

12 1. Vena cava 2.Right Kidney 3. Ureter 4. Bladder 5. Urethra 6. Aorta 7. Left Kidney 8. Renal Vein 9. Renal Artery

13 Urinary System Adrenal gland Kidney Ureters Bladder Urethra

14 ORGAN: Function Kidney: site of blood filtration Renal artery: brings blood to kidney Renal vein: brings blood back to heart Ureter: Brings waste TO bladder Bladder: Temporary urine storage site Urethra: Brings waste FROM bladder, out of system

15 The Kidney Collects waste Joins kidney to ureter Renal Pelvis
Inner area Water reabsorption Medulla Outer layer Where filtration occurs Cortex Function Structure


Three distinct regions of the kidney Cortex – outer region Medulla – just below cortex Pelvis – a hollow chamber within the medulla The cortex and medulla of each kidney are made up of a approximately one million nephrons

18 The Kidney Renal Pelvis Ureter Renal Cortex Renal Medulla Nephrons
Renal Artery Renal Vein

NEPHRON the structural and functional unit of the kidney

20 Label the following diagram
Bowman’s Capsule Glomerulus Renal artery Distal tubule Proximal tubule Renal vein Collecting duct Capillary bed Loop of Henle

21 Ball of capillaries – site of filtration
Glomerulus Leaves glomerulus, goes to vein Efferent Arteriole Brings blood to glomerulus Afferent arteriole Filter Bowman’s Capsule Collecting site for all nephrons – waste out to ureter Renal pelvis Empties waste into renal pelvis Collecting duct Leads to collecting duct Distal Tubule First tube in nephron. From BC. Reabsorption of Water Proximal Tubule FUNCTION STRUCTURE


NEPHRON the structural and functional unit of the kidney BOWMAN’S CAPSULE a double walled chamber – start of the tubule.

24 The Nephron Bowman's Capsule

GLOMERULUS network of capillaries within the Bowman’s capsule high pressure (4x higher than in capillaries)

26 The Nephron Bowman's Capsule Glomerulus The Nephron

PROXIMAL TUBULE active transport of many valuable substances back into blood network glucose amino acids sodium

28 The Nephron Proximal Convoluted Tubule

PROXIMAL TUBULE What doesn’t get absorbed? urea other toxic substances some salt much of the water

LOOP OF HENLE the long hair-pin turn!!

31 The Nephron Loop of Henle

LOOP OF HENLE the long hair-pin turn!! some of the remaining water and salt will be returned to the blood lies in the medulla which is relatively salty (hypertonic)


34 The Nephron Distal Convoluted Tubule

35 The Nephron Collecting Duct

DISTAL TUBULE and COLLECTING DUCTS More water reabsorption This depends on the presence of certain hormones (ADH) Anti diuretic Hormone Exact amounts of substances are reclaimed to the blood very precise

37 Urine Formation Depends on three functions: Filtration Reabsorption
Movement from blood – Bowman’s capsule Reabsorption Transfer of needed nutrient back INTO blood Tubules Secretion Movement of material from blood back into nephron

38 Four Steps to Urine Formation
1) FILTRATION Occurs at the junction of the glomerulus and the wall of the Bowman’s capsule Each glomerulus receives blood from an afferent arteriole and discharges its blood into an efferent arteriole (hypertonic). Fluid and dissolved materials (nutrients, wastes, ions) in the blood plasma pass from the glomerulus into Bowman’s capsule due to a local increase in blood pressure within the glomerulus

39 Four Steps to Urine Formation
1) Filtration (con’t) this material is then called nephric filtrate blood cells, plasma proteins and platelets are too large to pass through the wall of the capillary and therefore remain within the capillary.

40 Four Steps to Urine Formation
2) REABSORPTION in the proximal tubule returns about 99% of filtrate to the blood efferent arteriole feeds second capillary network that surrounds the tubule this network receives reabsorbed substances eventually leads to renal vein

41 Four Steps to Urine Formation
2) REABSORPTION (con’t) Water rushes into the blood because of osmosis Problem Not enough water is returned this way. Solution Just actively transport water into the blood right?

42 Wrong!!! There is no way of ACTIVELY transporting water
So how can we transport more water into the blood?

43 Solution 2) Reabsorption (con’t)
active transport of solutes into the capillary bed glucose amino acids vitamins inorganic ions (Na+) water is passively reabsorbed from the proximal tubule as these solutes are actively removed from the filtrate

44 Four Steps to Urine Formation
2) Reabsorption (con’t) Reabsorption and the distal tubule. A more selective, precisely regulated reabsorption occurs in the distal tubules Additional quantities of salts and water may be reabsorbed The exact amount of each substance reclaimed occurs in the distal tubules. excess is excreted in urine e.g. glucose and diabetes

45 Four Steps to Urine Formation
3) SECRETION This is the last chance for anything to leave the blood and enter the urine Active transport Occurs in the distal tubule and collecting duct Hydrogen ion secretion – helps regulate blood pH Distal tubule Na+ moves into the blood and H+ moves into the tubule filtrate blood pH increases (ranges ) urine pH decreases (ranges )

46 Four Steps to Urine Formation
potassium secretion prevents accumulation of potassium that can create neural and muscular problems some drugs are removed from the body by secretion substances eliminated in this manner are creatine – by product of protein metabolism potassium penicillin

47 Four Steps to Urine Formation
4) Elimination Pathway collecting duct renal pelvis ureter urinary bladder urethra environment

48 Nephron Function Summary
Reabsorption CORTEX Amino Acids Na Water Glucose Water Secretion Na NH 3 K + Filtration Na Water Na Water Na Water Na ADH Na Water MEDULLA Na Active Transport Water Water Passive Transport


50 What is in urine? Excess sugars Excess salts Excess H+ ions
Urea and uric acid Excess H2O

51 Control of Excretion Disorders and Treatments

52 HORMONES ADH The Antidiuretic hormone
influences the RATE of water reabsorption into blood from collecting ducts released by the pituitary gland in the brain Osmoreceptors in brain stimulated by low blood volume and increased osmotic pressure both of those means that there is not enough water in the blood. rate of ADH secretion is increased. ADH saves water. More ADH = more H2O absorption = increased urine concentration Very yellow concentrated urine

53 Most water reabsorbed in proximal tubule
permeable Rest of tubule permeable ONLY IF ADH is present Ascending loop Distal tubule

54 Aldosterone and Sodium
Aldosterone – hormone Produced in adrenal gland Increased Na+ uptake in nephron More water may also move out Osmosis (high to low) Blood pressure Less fluid – lower blood pressure

55 Aldosterone acts on distal tubule and collecting duct
Angiotensin produced Constricts blood vessels, increase blood pressure Causes release of aldosterone Aldosterone acts on distal tubule and collecting duct More sodium reabsorbed Fluid level increase BP increases


57 Kidney Disease Diabetes Insipidus Problems with ADH production
No ADH, no H2O reabsorption Huge urine output Up to 20 L/day

58 Kidney Stones Stone removal Minerals forming solid crystals (Ca+, Na+)
Get lodged in pelvis or ureter Can tear tissues as it moves out OHMYGOODNESSMAKEITSTOPICANNOTSTANDTHEPAIN!!!!!!!!!!!!!!!! Stone removal Surgery Ultrasound catheter

59 Kidney Stones

60 Kidney Dialysis Cleaning of blood Treatment of kidney failure
Blood goes through a filter Concentration gradients remove waste


62 Continuous Dialysis

63 Kidney Donation Human system built in twos Extra kidney for backup
One kidney – can do all the work With less than 20% kidney function, problems occur Requires kidney dialysis If problem gets really bad, might need a new one  TRANSPLANT

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