1. Chapter 15 The Urinary System

2. Functions of the Urinary System
1. Elimination of waste
Nitrogenous wastes
Toxins
Drugs
2. Regulates homeostasis
Water balance
Electrolytes
Acid-base balance in the blood
Blood pressure
RBC blood cell production
Activation of vit. D

3. Organs of the Urinary system
Kidneys
Ureters
Urinary bladder
Urethra

4. Location of the Kidneys
Against dorsal wall
T12 to L3
Right lower than left
Attached to ureters, renal blood vessels, & nerves at renal hilus
Atop kidney is adrenal gland

5. Coverings of the Kidneys
1. Renal capsule
Surrounds kidney
2. Adipose capsule
protection
keeps kidney in location

6. Regions of the Kidney Renal cortex – outer region
Renal medulla – inside the cortex
Renal pelvis – inner collecting tube

7. Kidney Structures
Medullary pyramids – triangular regions of tissue in medulla
Renal columns – extensions of cortex-like material inward
Calyces – cup-shaped structures that funnel urine towards renal pelvis

8. Blood Flow in the Kidneys

9. Nephrons Structural and functional units of the kidneys Forms urine
Main structures
a. Glomerulus
b. Renal tubule

10. Glomerulus Specialized capillary bed
Arterioles on both sides (maintains high pressure)
Large afferent arteriole
Narrow efferent arteriole
Capillaries covered with podocytes from the renal tubule
Glomerulus sits within a glomerular capsule (1st part of the renal tubule)

11. Renal Tubule Glomerular (Bowman’s) capsule Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule

12. Types of Nephrons 1. Cortical 2. Juxtamedullary entirely in cortex
most nephrons
2. Juxtamedullary
at boundary of cortex & medulla

13. Peritubular Capillaries
Arise from efferent arteriole
Normal, low pressure capillaries
Attached to venule
Cling to renal tubule
Reabsorb substances from collecting tubes
Urine Formation
Filtration
Reabsorption
Secretion

14. Filtration Nonselective passive process
Water and solutes smaller than proteins are forced through capillary walls
Blood cells cannot pass out to the capillaries
Filtrate is collected in the glomerular capsule and leaves via the renal tubule

15. Reabsorption Peritubular capillaries reabsorb
- Some water, Glucose, Amino acids, Ions
Some passive, most active
Most reabsorption occurs in proximal tubule
Not Reabsorbed
Nitrogenous waste products
- Urea
- Uric acid
- Creatinine
Excess water

16. Secretion – Reabsorption in Reverse
Materials move from peritubular capillaries into renal tubules
H+ & K+
Creatinine
Materials left in renal tubule move to ureter

17. Formation of Urine
Figure 15.5

18. Characteristics of Urine
Yellow due to pigment urochrome (from break-down of hemoglobin) & solutes
Sterile
Slightly aromatic
Normal pH of ~ 6
Specific gravity of to 1.035

19. Ureters Slender tubes from kidney to bladder
- Continuous with renal pelvis
- Enter the posterior aspect of the bladder
Runs behind the peritoneum
Peristalsis aids gravity in urine transport

20. Urinary Bladder Smooth, collapsible, muscular sac
Temporarily stores urine
Trigone – 3 openings
- Two from ureters
- One to urethrea

21. Urinary Bladder Wall Detrusor muscle – pushes down
3 layers of smooth muscle
Walls - thick & folded in empty bladder
Transitional epithelium - expands without increasing internal pressure

22. Urethra Thin-walled tube Carries urine from bladder by peristalsis
Release controlled by 2 sphincters
Internal urethral sphincter (involuntary)
External urethral sphincter (voluntary)

23. Urethra Gender Differences
Length
- Females – 3–4 cm (1 inch)
- Males – 20 cm (8 inches)
Location
- Females – along wall of the vagina
- Males – through the prostate and penis
Function
- Females – only urine
- Males –urine and sperm

24. Micturition (Voiding)
Both sphincters must open
internal relaxes after bladder stretches
Activation - impulse to spinal cord and back via pelvic splanchnic nerves
external voluntarily relaxes

25. Maintaining Water Balance
Normal amount of water in humans
- Adult females – 50%
- Adult males – 60%
- Babies – 75%
- Old age – 45%
Water is necessary for many functions and levels must be maintained
Water intake = water output
Sources for water intake
- foods and fluids
- metabolic processes
Sources for water output
- Vaporization from lungs
- perspiration
- feces
- Urine

26. Distribution of Body Fluid
Intracellular fluid (inside cells)
Extracellular fluid (outside cells)
- Interstitial fluid
- Blood plasma
Figure 15.7

27. Link Between Water and Salt
Changes in electrolyte balance causes water to move from one compartment to another
- Alters blood volume & blood pressure
- Can impair the activity of cells

28. Regulation of Reabsorption
Hormones
- Antidiuretic hormone (ADH) prevents excessive water loss in urine
Aldosterone regulates sodium
Triggered by the renin-angiotensin mechanism
Monitored by kidneys and hypothalamus

29. Maintaining Blood pH Normal Blood pH
- Alkalosis – pH above 7.45
- Acidosis – pH below 7.35
Most ions are metabolic byproducts
Most pH balance is maintained by kidneys
Other acid-base controlling systems
- Blood buffers
- Respiration

30. Blood Buffers Molecules to prevent dramatic changes in [H+]
- Bind to H+ when pH drops
- Release H+ when pH rises
Three major chemical buffers
Bicarbonates
Phosphates
Proteins

31. Buffering Systems

32. Fetal/Newborn Developmental Aging Functional kidneys by 3rd month
Bladder is small in newborn
Urine cannot be concentrated
Developmental
Control of voluntary sphincter ~ 18 mos
Urinary infections - common problems
Aging
Bladder shrinks
Decline in function
Retention if prostate enlarges (males)