1. EXCRETORY SYSTEM

2. EXCRETION AND THE INTERACTION OF SYSTEMS In this chapter, you will learn: Each kidney receives blood that is processed to form urine, which drains through a ureter and into the urinary bladder for excretion. Each kidney contains over one million nephrons that process blood to form urine. The functional unit of the kidney is the nephron. Each nephron filters blood, reabsorbs substances such as sodium and glucose for reuse in the body, and secretes excess or toxic substances such as urea to produce urine.

3. EXCRETION AND THE INTERACTION OF SYSTEMS In this chapter, you will learn: Antidiuretic hormone (ADH) regulates the amount of water reabsorbed in the distal tubule. Aldosterone regulates the amount of salt that is reabsorbed or secreted. The acid-base balance of the blood is adjusted by the secretion of hydrogen ions and reabsorption of bicarbonate ions. Various technologies are used to solve problems involving dysfunctions and disorders of the excretory system.

4. THE STRUCTURES AND FUNCTION OF THE EXCRETORY SYSTEM In this section, you will: Identify the main structures and functions of the human excretory system Explain the function of the nephron

5. FUNCTION The MAIN function of the excretory system is to remove wastes from the body and to regulate the volume and composition of body fluids Waste - anything the body will not use or there is more than the body will use Excretion – the process of separating wastes from the body fluids and getting rid of them

6. STRUCTURES WHICH CONCENTRATE URINE Control of urinary water loss is a major mechanism by which body water is regulated. Animals with free access to fresh water typically excrete the wastes from their blood stream in a copious urine that is hypotonic in relation to their blood (eg. frogs daily urinary out put is 25% of it body weight). Most terrestrial animals cannot afford to waste water so they excrete a hypertonic urine (ie. urine which is more concentrated than their body fluids)[ human urine 3.5 X more [ ] than blood ]

7. ORGANS OF THE EXCRETORY SYSTEM - GROSS ANATOMY

8. ORGANS OF THE EXCRETORY SYSTEM Humans have two kidneys Humans have two kidneys We are able to function with We are able to function with only one kidney Our kidneys will reabsorb Our kidneys will reabsorb any good things (water, sugar) back into our body and make the rest into urine The kidneys release urine into ureters which are two long, muscular tubes The kidneys release urine into ureters which are two long, muscular tubes

10. Urine is then moved by peristalsis to the urinary bladder to be stored temporarily When we urinate the urine exits our body through the urethra

11. URINARY BLADDER Hollow muscular sac which collects and is a reservoir for urine Held loosely in place by folds of the abdominal lining (peritoneum) In males – located in front of the rectum In females - located in front & under the uterus Full bladder holds about 200 - 400 ml

12. URETHRA Membranous tube through which urine is discharged from the urinary bladder to the exterior of the body In males - common to both the reproductive and the urinary systems In females - two systems are kept separate - urethra embedded in the anterior wall of the vagina, posterior to the pubic bone

13. MALE VS. FEMALE

14. RENAL ARTERIES Blood comes directly from the aorta therefore it is under high pressure Receives about 25% of the blood from each ventricular contraction Renal veins carry blood back to the inferior vena cava

15. FILL IN THE BLANKS!

16. REGIONS OF THE KIDNEY The kidney can be divided into three regions: Renal cortex Renal medulla Renal pelvis

17. KIDNEY STRUCTURE (A) includes some blood vessels to reinforce the connection between the circulatory and excretory systems. (B) & (C) do not include blood vessels, and identify the three regions of the kidney (C) the functional unit of the kidney: the nephron.

18. THE KIDNEYS In each kidney the ureter opens up to form the renal pelvis The renal pelvis receives urine from the renal tissue in the kidney

19. This renal tissue is divided into an outer renal cortex and an inner renal medulla In these two regions there are many small nephrons which are responsible for filtering various substances from the blood (surrounded by capillaries) Each nephron is separated into a filter, a tube and a duct

21. RENAL CORTEX Outer portion of the kidney Location of ultrafiltration

22. RENAL MEDULLA Inner portion of the kidney Contains renal pyramids Blood from renal arteries enters here Cat Kidney

23. RENAL PELVIS Funnel-like, proximal portion of ureter Acts as funnel for urine produced by kidney to enter ureter

24. FUNCTIONAL REGIONS OF THE NEPHRON The nephron can be divided into 3 urine producing functional regions: Filter Tubule Duct

25. THE NEPHRON The filter contains the Bowman’s capsule which surrounds a network of capillaries called a glomerulus (main filtration device) The Bowman’s capsule is connected to a small, long, narrow tubule that is twisted into a loop (reabsorption device) This loop has three sections: the proximal tubule, the loop of Henle and the distal tubule The tubule empties into a collecting duct which will reabsorb any water from the filtrate

27. BLOOD FLOW THROUGH THE NEPHRON Left and Right renal arteries  decreasing vessel size  afferent arterioles in cortex (leads into glomerulus)  through capillaries of the glomerulus (in Bowman's capsule)  efferent arteriole  peritubular capillaries which surround the renal tubule (proximal tubule, Loop of Henle, distal tubule)  merge to form venule  renal vein Blood is rich in oxygen and contains all the normal constituents such as cells, proteins, amino acids, glucose, salts, nutrients, and wastes The nephron functions to remove the wastes - wanted and unwanted substances enter into Bowman's capsule

28. KIDNEY FUNCTIONS 1. Eliminate waste Nitrogenous in the form of urea (formed in the liver from ammonia) Other wastes released from cells of the body into the blood

29. KIDNEY FUNCTIONS 2. Maintain water balance Filter and concentrate wastes in preparation for excretion in order to retain as much water an reusable materials as possible

30. KIDNEY FUNCTIONS 3. Acid-base balance of body Acidic or alkaline products are excreted Normal diet is mostly acid (can manufacture ammonia which is alkaline to increase pH)

31. KIDNEY FUNCTIONS 4. Electrolyte balance Electrolyte = small molecules which conduct electrical charge (eg. Na +, Ca 2+,K + & some acids) and which are required for muscle and nerve function

32. URINE FORMATION IN THE NEPHRON In this section, you will: Explain the function of the nephron in maintaining the composition of blood plasma Describe the function of the kidney in excreting metabolic wastes and expelling them into the environment

33. URINE FORMATION

34. URINE FORMATION IN THE NEPHRON Four processes are very important to the formation of urine: Four processes are very important to the formation of urine: 1.Glomerular filtration 2.Tubular reabsorption 3.Tubular secretion 4.Water reabsorption

35. GLOMERULAR FILTRATION Involves the glomerulus and the Bowman’s capsule Involves the glomerulus and the Bowman’s capsule Forces some of the water and dissolved substances found in plasma from the glomerulus to the Bowman’s capsule Forces some of the water and dissolved substances found in plasma from the glomerulus to the Bowman’s capsule

37. TUBULAR REABSORPTION Involves the proximal tubule and the loop of Henle Involves the proximal tubule and the loop of Henle Most of the filtrate that passes through the proximal tubule is reabsorbed and returned to the body Most of the filtrate that passes through the proximal tubule is reabsorbed and returned to the body This involves both active and passive transport mechanisms This involves both active and passive transport mechanisms ATP is used to help transport sodium ions (Na + ), glucose and other solutes back to the blood ATP is used to help transport sodium ions (Na + ), glucose and other solutes back to the blood Water follows through osmosis Water follows through osmosis

39. The loop of Henle’s main function is to reabsorb water and ions from the filtrate The loop of Henle’s main function is to reabsorb water and ions from the filtrate The descending loop of Henle is in a very salty environment causing water to diffuse from the filtrate to the capillaries through osmosis The descending loop of Henle is in a very salty environment causing water to diffuse from the filtrate to the capillaries through osmosis In the ascending loop of Henle things change and now the Na + diffuses from the filtrate into the capillaries In the ascending loop of Henle things change and now the Na + diffuses from the filtrate into the capillaries

40. TUBULAR SECRETION Involves the distal tubule Involves the distal tubule Potassium ions (K+) are passively secreted and hydrogen ions (H+) are actively secreted into the distal tubule from the capillaries Potassium ions (K+) are passively secreted and hydrogen ions (H+) are actively secreted into the distal tubule from the capillaries Also involves some reabsorption of sodium ions, chloride ions and water from the distal tubule to the capillaries Also involves some reabsorption of sodium ions, chloride ions and water from the distal tubule to the capillaries

41. WATER REABSORPTION Involves the collecting duct Involves the collecting duct The water is reabsorbed into the capillaries from the collecting duct by osmosis The water is reabsorbed into the capillaries from the collecting duct by osmosis This helps prevent humans from losing too much water and becoming dehydrated This helps prevent humans from losing too much water and becoming dehydrated This reabsorption of water causes the filtrate to become about 4X more concentrated This reabsorption of water causes the filtrate to become about 4X more concentrated This is now called urine and we are able to urinate This is now called urine and we are able to urinate

43. REABSORPTION IN THE LOOP OF HENLE

44. PARTS OF THE NEPHRON AND THEIR FUNCTIONS GlomerulusFiltration Glomerular blood pressure forces some of the water and dissolved substances from the blood plasma through the pores of the glomerular walls (filtrate) Bowman’s capsuleReceives filtrate from glomerulus Proximal tubuleReabsorption Active reabsorption of all nutrients (incl. glucose and aa) Active reabsorption of cations such as Na, K,Ca Passive reabsorption of water by osmosis Passive reabsorption of anions such as Cl and bicarbonate by electrostatic attraction Secretion Active secretion of hydrogen ions

45. PARTS OF THE NEPHRON AND THEIR FUNCTIONS Descending LOHReabsorption Passive reabsorption of water by osmosis Ascending LOHReabsorption Active reabsorption of sodium ions Passive reabsorption of chloride and potassium ions Distal tubeReabsorption Active reabsorption of sodium ions Passive reabsorption of water by osmosis Passive reabsorption of anions such as Cl and bicarbonate Secretion Active secretion of hydrogen ions Passive secretion of K+ by electrical attraction to Cl- Collecting tubeReabsorption Passive reabsorption of water by osmosis

46. MAINTAINING THE EXCRETORY SYSTEM When our kidneys reabsorb water this affects the blood volume and the concentration of solutes in our plasma This often causes the movement of water As water moves it exerts a force known as osmotic pressure

47. REGULATING REABSORPTION OF WATER In our brain we have osmoreceptors that are sensitive to changes in osmotic pressure These osmoreceptors are found in the hypothalamus

48. DEHYDRATION When our bodies become dehydrated the solute concentration in our blood increases which increases osmotic pressure This signals to the hypothalamus which tells the pituitary to release antidiuretic hormone (ADH) ADH travels to the kidneys Signals to the distal tubule and collecting duct to reabsorb more water End up having more concentrated urine

49. OVER HYDRATION Blood is too dilute which decreases the osmotic pressure This signals to the hypothalamus which tells the pituitary gland to inhibit the release of ADH With no ADH targeting the kidneys the distal tubule and collecting duct become LESS permeable to water Results in much more water being lost in the urine

51. HORMONES IMPORTANT IN URINARY SYSTEM Negative feedback loops of the endocrine system monitor and determine appropriate levels of hormones in the blood (details - Endocrine System - Bio 30)

52. ADH can also be blocked by substances known as diuretics This will cause people to pee more often and become more dehydrated Examples are alcohol and caffeine

53. REABSORPTION OF SALTS Kidneys regulate salt balance by controlling the excretion and reabsorption of Na + If the amount of Na + in blood drops this triggers the hormone aldosterone Aldosterone will stimulate the distal tubules and collecting ducts to reabsorb Na +

54. DISORDERS OF THE EXCRETORY SYSTEM Urinary tract infection One of the most common disorders Two types: Bladder and urethra are infected = cystitis Only urethra infected = urethritis More common in women Symptoms: painful to pee, need to pee often, bloody or brown urine, chills, fever, nausea, vomiting Can result in permanent kidney damage Treatment is usually antibiotics but can turn to surgery

55. Kidney stones Kidney stones Crystalline formations in the kidney Crystalline formations in the kidney Form due to excess calcium in urine Form due to excess calcium in urine Can also be caused by repeating urinary tract infections, insufficient water consumption, low activity Can also be caused by repeating urinary tract infections, insufficient water consumption, low activity Treatment depends on how large the stones are Treatment depends on how large the stones are Some pass through the urinary tract easily, medications can help break some down, ultrasound shock waves, surgery Some pass through the urinary tract easily, medications can help break some down, ultrasound shock waves, surgery

57. KIDNEY STONES

58. DIABETES INSIPIDUS A type of diabetes that is found in people who have insufficient amounts of ADH in their body People who do not have enough ADH tend to pee A LOT (up to 8L per day) Are thirsty all the time and become severely dehydrated

59. PROBLEMS WITH KIDNEY FUNCTION Renal insufficiency – when kidneys cannot maintain homeostasis because of nephron damage This can be caused by: kidney infection, high blood pressure, diabetes, trauma, poisoning, atherosclerosis, tubule blockage People can survive with up to 75% of their nephrons damaged or destroyed – more than this and homeostasis can not be maintained Once this happens a person needs either a kidney transplant or dialysis

61. Artificial kidney has saved many lives but is a poor substitute for the real thing Dialysis is both physically and psychologically wearing (up to 6 hrs. 3 X per week) Risk of infection and clotting of the blood from dialysis makes kidney transplants are a better alternative, unfortunately the demand outstrips the supply

62. DISORDERS - URINARY SYSTEM Kidney failure – CAPD Continuous ambulatory peritoneal dialysis

63. HEMODIALYSIS & PERITONEAL DIALYSIS

64. Kidney failure - Transplants The procedure is relatively easy Connections are made to the iliac artery, vein and ureter Problem: immune rejection - immune system recognizes a foreign intruder and attempts to destroy it (auto-immune suppressants are used to help the body accept the kidney) Leading cause of death among kidney recipients is infections thus ↓ effectiveness of the immune system ↑ the risk of infection difficulties

66. CHAPTER REVIEW Draw diagrams of the excretory system. What wastes are produced by the human body? Describe the functions of each major structure in the excretory system. How does the excretory system interact with blood and circulation? Why do wastes need to be eliminated from the body?

68. CHAPTER SUMMARY The metabolic activities of cells, including energy release, maintenance, and repair, produce substances that change the balance of the volume of water and the concentration and composition of dissolved substances in the body’s fluids. The excretory system removes these materials to maintain the optimal volume of water and composition of body fluids, dispose of wastes, and recycle the non-waste substances. The substances in question include carbon dioxide; water; ions of sodium (Na + ), chloride (Cl – ), and hydrogen (H + ); and other compounds resulting from the breakdown of proteins and nucleic acids. The excretory system also plays a key role in maintaining the acid-base balance (pH) in the blood.

69. CHAPTER SUMMARY The organs of the excretory system are the kidneys, the ureters, the urinary bladder, and the urethra. The kidneys contain millions of tiny nephrons that each contain a filter, a tube, and a duct. The nephrons filter out waste and reabsorb substances such as sodium and water for reuse by the body’s systems. The resulting filtrate, known as urine, is sent through the ureters to the urinary bladder for temporary storage until it is eliminated from the body through the urethra. Disorders of the excretory system include urinary tract infections, kidney stones, and renal insufficiency. Renal insufficiency may require dialysis or a kidney transplant in order to ensure that wastes are secreted rather than building up to toxic levels in the body.