chapter 15 part b

Chapter 15: The Urinary System

Part B

1.     Urinary structures

a.    Ureters

                                          i.    Slender tubes attach each kidney to the bladder

                                        ii.    Run from renal pelvis to the posterior aspect of the bladder

                                       iii.    Behind the peritoneum

                                       iv.    Peristalsis aids gravity in urine transport

b.    Urinary bladder

                                          i.    Smooth, collapsible, muscular sac

                                        ii.    Temporarily stores urine

                                       iii.    Trigone- triangular region of the bladder base

                                       iv.    Three openings: two from the ureters, one to the urethra

                                         v.    Prostate glands surround the neck of the bladder and urethra(in males)

                                       vi.    Bladder wall

1.     Detrusor muscle= three layers of smooth muscle

2.    Mucosa made the transitional epithelium

3.    Empty bladder has thick walls that are folded in

4.    Bladder expansion can occur without increasing internal pressure

                                      vii.    Capacity

1.     Moderately full bladder is about 5 inches long and holds about 500 mL of urine

2.    Maximum holding of twice that amount

c.    Urethra

                                          i.    Thin-walled tube that carries urine from the bladder to the outside of the body by peristalsis

                                        ii.    Urine release is controlled by two sphincters:

1.     Internal urethral sphincter- involuntary and made of smooth muscle

2.    External urethral sphincter voluntary and made of skeletal muscle

                                       iii.    Gender differences

1.     Length

a.    Female= more likely to get a bladder infection because it is shorter…3-4 cm

b.    Male= 20 cm

2.    Location

a.    Female- along the wall of the vagina

b.    Male- through the prostate and penis

3.    Function

a.    Female- only carries urine

b.    Male-= carries urine and is a passageway for sperm cells

2.    Micturition = voiding= urinating

a.    Both sphincters muscles must open to allow voiding

b.    Internal urethral sphincter is relaxed after stretching of the bladder

c.    Pelvic nerves initiate bladder to go into reflex contractions

d.    Urge to void is caused when urine is forced past the internal urethra sphincter

e.    External urethral sphincter must be voluntarily relaxed to void

3.    Fluid, electrolyte, acid-base balance

a.    Blood composition: depends on three factors

                                          i.    Diet

                                        ii.    Cellular metabolism

                                       iii.    Urine output

                                       iv.    Four roles kidneys have  in maintaining blood composition:

1.     Excretion of nitrogen- containing wastes

2.    Maintaining water balance of the blood

3.    Maintaining electrolyte balance of the blood

4.    Ensuring proper blood pH

b.    Water balance

                                          i.    Normal amount in body by mass

1.     Young adult female= 50%

2.    Young adult male= 60%

3.    Babies= 75%

4.    The elderly= 45%

5.    Universal solvent

6.    Water is necessary for many body functions, and levels must be maintained

                                        ii.    Distribution of body fluid

1.     Intracellular (ICF)- fluid inside cells, about two-thirds of body fluid

2.    Extracellular (ECF)- fluid outside cells,  interstitial fluid, blood plasma

                                       iii.    Link between water and salt

1.     Solutes in body include electrolytes like sodium, potassium, and calcium ions

2.    Changes in electrolyte balance causes water to move from one compartment to another (osmosis)

a.    Alters blood volume and blood pressure

b.    Impairs the activity of cells

                                       iv.    Water in = water out

1.     Sources for water intake- ingested foods and fluids

2.    Sources for water output- vaporization out of the lungs, perspiration, feces, urine

3.    Dilute urine is produced if water intake is excessive

4.    Concentrated urine is produced if large amounts of water are lost

5.    Electrolyte concentrations

                                         v.    Regulation of water and electrolyte reabsorption

1.     Osmoreceptors: cells in the hypothalamus

a.    React to changes in blood composition by becoming more active

2.    Hormones control regulation

a.    ADH = antidiuretic hormone

                                                                                          i.    Prevents excessive water loss

                                                                                        ii.    Causes kidney’s collecting ducts to reabsorb more water

                                                                                       iii.    Alcohol suppresses ADH, causing urination

                                                                                       iv.    Diabetes insipidus

1.     When ADH is not released

2.    Causes huge outputs of dilute urine

b.    Aldosterone

                                                                                          i.    From adrenal glands

                                                                                        ii.    Regulates sodium ion content of ECF

                                                                                       iii.    Promotes reabsorption of sodium ions

1.     Water follows salt

c.    Rennin-angiotensin mechanism

                                                                                          i.    Juxtaglomerular (JG) apparatus

1.     Cells stimulated by

2.    Rennin produces

3.    Angiotensin II causes

4.    Results in

c.    Maintaining acid-base balance in blood

                                          i.    Blood pH between

1.     Alkalosis =

2.    Acidosis =

3.    Physiological acidosis =

                                        ii.    Body acids

1.     P , L, A

2.    Carbon dioxide

3.    Ammonia

4.    Acid-base control systems/organs

a.    Kidneys

b.    Respiration

c.    Blood buffers

                                                                                          i.    Acids =

                                                                                        ii.    Strong acids =

                                                                                       iii.    Weak acids =

                                                                                       iv.    Bases =

                                                                                         v.    Strong bases =

                                                                                       vi.    Weak bases =

                                                                                      vii.    Action

1.     Bind to H⁺

2.    Release H⁺

                                                                                     viii.    Three major systems

1.     Protein

2.    Phosphate

3.    Bicarbonate

a.    H₂CO₃ and NaHCO₃

b.    Carbonic acid

c.    Bicarbonate ions

d.    HCl + NaHCO₃ àH₂CO₃ + NaCl

4.    Developmental aspects of the urinary system

a.    Early life

                                          i.    Functional kidneys

                                        ii.    Newborn

1.     Bladder

2.    Urine

3.    Void

                                       iii.    Young children

1.     Control of voluntary sphincter

2.    Nighttime control

3.    Bladder infections

                                       iv.    Elderly

1.     Bladder changes

2.    Associated problems

a.    Urgency

b.    Frequency

c.    Nocturia

d.    Incontinence

e.    Urinary retention