1. Biology: Life on Earth (Audesirk)
Chapter 30
Biology: Life on Earth (Audesirk)
The Urinary System
Chapter 30

2. The Simple Excretory System of a Flatworm
Biology: Life on Earth (Audesirk)
The Simple Excretory System of a Flatworm
Chapter 30
Excretory Pores
Nucleus
Flame Cell
Cilia
Hollow flame cells direct excess water and dissolved wastes into a network of tubes. The beating cilia of the flame cells help circulate the fluid to excretory pores.
Pharynx
Excretory Tubule
Chapter 30

3. Excretory System of the Earthworm
Biology: Life on Earth (Audesirk)
Excretory System of the Earthworm
Chapter 30
Nephridia
Coelom
This system consists of structures called nephridia, one pair per segment. Coelomic fluid is drawn into the nephrostome, and urine is released through the excretory pore. Each nephridium resembles a vertebrate nephron.
Nephrostome
Excretory Pore
Intestine
Ventral Nerve Cord
Chapter 30

4. Formation & Excretion of Urea
Chapter 30
1 In cells, amino acids are metabolized, releasing ammonia.
Ammonia NH3
2 In liver, ammonia is combined with CO2 to make urea.
urea NH2-C-NH2 || O
3 In kidneys, urea + water + other wastes = urine.
excreted in urine
1 In cells, amino acids are metabolized, releasing ammonia.
Ammonia NH3
Carried in blood
2 In liver, ammonia is combined with CO2 to make urea.
urea NH2-C-NH2 || O
1 In cells, amino acids are metabolized, releasing ammonia.
Ammonia NH3
Carried in blood
2 In liver, ammonia is combined with CO2 to make urea.
urea NH2-C-NH2 || O
Carried in blood
3 In kidneys, urea + water + other wastes = urine.
excreted in urine

5. The Path of wastes through the system
Chapter 30
The human kidneys are paired, bean shaped organs located on either side of the spinal column extending slightly above the waist.
Each is 5 inches long and 3 inches wide, 1 inch thick.
Blood carrying dissolved waste enters each kidney through the renal artery.
After the blood is filtered, it exits through the renal vein.
Urine leaves the kidney via the ureter- a narrow muscular tube. Fig 30-5 p.608

6. The Human Urinary System
Biology: Life on Earth (Audesirk)
Chapter 30
The Human Urinary System
Renal Artery
Kidney
Renal Vein
Vena Cava
Diagrammatic view of the human urinary system and its blood supply.
Aorta
Ureter
Urinary Bladder
Chapter 30

7. Chapter 30
Ureter- uses peristaltic contractions to transport urine to the urinary bladder ( the bladder)
Bladder- a hollow, muscular chamber that collects and stores urine. The walls of the bladder contain expandable smooth muscle.
Urine is kept in the bladder by 2 sphincter muscles located at the base above the junction of the urethra.
When the bladder fills, receptors on the walls signal the condition and triggers reflex contractions.

8. Bladder (cont’d)
Chapter 30
Internal sphincter – sphincter closest to the bladder opens during this reflex.
External sphincter – lower sphincter is under voluntary control so the brain can suppress the reflex unless the bladder distension becomes acute.
An average adult bladder can hold 500 mL of urine but the need to urinate is triggered by smaller amounts.
Urine makes its way out via the urethra. It is 1.5 inches in females and 8 inches long in males

9. Storage and Excretion of Urine
Chapter 30
Ureter
Bladder
Urethra

10. The Human Urinary System
Biology: Life on Earth (Audesirk)
Chapter 30
The Human Urinary System
Diagrammatic view of the human urinary system and its blood supply.
Ureter
Urinary Bladder
Urethra (in penis)
Chapter 30

11. Urine Formation Urine is formed in the kidneys.
Chapter 30
Urine is formed in the kidneys.
Each kidney has a solid outer layer where urine is made.
There is also a subdivided inner chamber called the Renal pelvis – collects urine and funnels it to the ureter.
The outer layer of the kidney includes the renal cortex overlying the renal medulla.
This outer layer has an array of tiny filters called nephrons, which is filled with blood vessels.

12. Cross Section of a Kidney
Biology: Life on Earth (Audesirk)
Renal Pelvis
Chapter 30
Renal Cortex
Cross Section of a Kidney
Renal Artery
Nephron
The cross section shows the blood supply and internal structure of a kidney. The renal artery, which brings blood to the kidney, and the renal vein, which carries the filtered blood away, branch extensively within the kidney. The two are joined by a highly permeable capillary network through which substances are exchanged between the blood and the nephrons. A nephron, considerably enlarged, is drawn to show its orientation in the kidney. The renal pelvis is the branched collecting chamber that funnels urine out of the kidney.
Renal Medulla
Renal Vein
Renal Pelvis
Ureter
Chapter 30

13. Kidney Function Summary
Chapter 30
Waste removal
Filtration by the glomerulus
Urine formation in the nephron
Tubular reabsorption
Tubular secretion
Production and concentration of urine
Maintenance of homeostasis
Regulation of water content in the blood
Regulation of levels of molecules in the blood
Maintenance of blood pH
Regulation of blood pressure and oxygen content

14. The Nephron
Chapter 30
The glomerulus – a dense knot of capillaries from which the fluid from the blood is collected.
Bowman’s capsule – a surrounding cup-like structure.
Tubule – a long twisted tube divided into:
i. Proximal tubule
ii. Loop of Henle – extends into the renal medulla
iii. Distal convoluted tubule – leads into the collecting duct

15. An Individual Nephron and Its Blood Supply
Chapter 30
Collecting Duct
Distal Tubule
Proximal Tubule
An Individual Nephron and Its Blood Supply
Bowman’s Capsule
Arterioles
Branches of Renal Artery Renal Vein
Loop of Henle
Capillaries

16. What does the kidney filter?
Chapter 30
2 million nephrons
Filter 180 litres/day
All but 1.5 litres is reabsorbed
Minimum output of urine is mL/day

17. Material Filtered in 24 Hrs
Chapter 30
Substance filtered
Amount reabsorbed
Glucose 1.8Kg
100%
Na+
99.4%
Cl-
99.2%
HCO3 -
99.9%

18. Kidney function-waste removal
Chapter 30
Kidney function-waste removal
a. Filtration by the glomerulus
Water, nutrients and wastes are forced into fluid in Bowman’s capsule by pressure in the capillaries of the glomerulus

19. Urine Formation in the Nephron
Biology: Life on Earth (Audesirk)
Urine Formation in the Nephron
Chapter 30
Loop of Henle
1 Filtration
3 Tubular Secretion
A summary of events that occur during the formation of urine in the nephron.
Filtration: Water, nutrients, & wastes filtered from glomerular capillaries into Bowman’s capsule.
Reabsorption: Most water & nutrients reabsorbed from proximal tubule to blood.
Tubular Seceretion: In the distal tubule, additional wastes are actively secreted into the tubule from the blood.
Concentration: In the collecting duct, additional water may leave the blood, creating urine more concentrated than the blood.
2 Tubular Reabsorption
4 Concentration
Chapter 30

20. b. Urine formation in the nephron 1) Tubular reabsorption
Chapter 30
b. Urine formation in the nephron
1) Tubular reabsorption
in the proximal tubule, most nutrients and water are reabsorbed into the blood
2) Tubular secretion
in the distal tubule additional wastes (H, K, NH3) and drugs are actively secreted into the tubule from the blood

21. c. Production and concentration of urine
Chapter 30
c. Production and concentration of urine
in the collecting duct additional water may be secreted back into the blood, making the urine more concentrated and the blood less concentrated
the loop of Henle creates a concentration gradient through which the collecting duct passes
as the filtrate (urine) passes through the collecting duct it becomes the same concentration as the surrounding gradient (1200 mosm)milliosmolar

22. Chapter 30

23. Chapter 30

24. Related topics to urinary system
Chapter 30
A. Hypertension
B. Urine testing
C. University life and "hyperdiuresis"
D. Dialysis and kidney transplantation

25. Function-maintenance of homeostasis
Chapter 30
a. Regulation of water content in the blood
In the case of dehydration, sensors in the brain stimulate the release of the hormone ADH (antidiuretic hormone also called vasopressin)
ADH is released from the pituitary
It passes through the blood to the kidneys where it stimulates the release of water back into the blood from the distal tubule and the collecting duct.
When water balance is normal, the ADH secretion is stopped.

26. Chapter 30

27. Homeostasis in excretory system
Chapter 30
Homeostasis in excretory system

28. b. Regulation of levels of molecules in the blood
Chapter 30
b. Regulation of levels of molecules in the blood
Penicillin, salicylates (aspirin) excreted
glucose, proteins, and amino acids are all reabsorbed.
phosphate, sulfate, lactate, vit. C all reabsorbed.

29. c. Maintenance of blood pH
Chapter 30
c. Maintenance of blood pH
Most important buffer system is bicarbonate ion (HCO3- )
buffers maintain constant pH
kidney reabsorbs bicarbonate when blood is acidic and produces bicarbonate to further buffer the blood.

30. d. Regulation of blood pressure and oxygen content
Chapter 30
d. Regulation of blood pressure and oxygen content
when blood pressure falls, kidneys release renin into the blood. This causes formation of angiotensin.
angiotensin causes arterioles to constrict increasing blood pressure. Constriction also causes less blood to be filtered, maintaining water balance and further increasing blood pressure.
for low oxygen levels, kidneys release erythropoietin, stimulating red blood cell growth

31. Cross Section of a Kidney
Biology: Life on Earth (Audesirk)
Renal Pelvis
Chapter 30
Renal Cortex
Cross Section of a Kidney
Renal Artery
Nephron
The cross section shows the blood supply and internal structure of a kidney. The renal artery, which brings blood to the kidney, and the renal vein, which carries the filtered blood away, branch extensively within the kidney. The two are joined by a highly permeable capillary network through which substances are exchanged between the blood and the nephrons. A nephron, considerably enlarged, is drawn to show its orientation in the kidney. The renal pelvis is the branched collecting chamber that funnels urine out of the kidney.
Renal Medulla
Renal Vein
Renal Pelvis
Ureter
Chapter 30

32. Regulation of Water in Blood
Biology: Life on Earth (Audesirk)
Regulation of Water in Blood
Chapter 30
Sensors in hypothalamus gauge osmotic concentration
Deviations cause posterior pituitary to turn ADH release on or off
ADH restores blood osmotic concentration
Red = increased osmotic concentration
Green = decreased osmotic concentration 1 5
The water content of the blood is regulated in part by a negative feedback mechanism. Sensors in the hypothalamus gauge the concentration of solutes in the blood; deviations from a set point cause the anterior pituitary gland to turn on or turn off a release of the hormone ADH. Any perturbation of the system (for example, by dehydration) triggers a change that will restore blood solute concentration to the appropriate level (red arrows indicate increased osmotic concentration; green arrows indicate decreased concentration). 2 3 4
Chapter 30

33. Chapter 30
The End