Module 7: The Urinary System Flashcards
Urinary System
Upper urinary system
2 kidneys
*Forms urine
2 ureters
*Drains urine
Lower urinary system
Urinary bladder
*Stores urine
Urethra
*Urine leaves body
Kidneys
Principal organs
Primary functions
Regulate volume and composition of extracellular
fluid (ECF)
Excrete waste products from the body
Other functions
Control BP
Make erythropoietin
Activate vitamin D
Regulate acid-base balance
Kidney Macrostructure
Bean-shaped organs; right lower than left
Located retroperitoneally; T12 to L3
Adrenal gland lies on top of each kidney
Cushioned and supported by fat, connective tissue
Capsule - a fibrous membrane covering the surface
-Shock absorber, protects the organ
Hilus on medial side
-Renal artery and nerves enter
-Renal vein and ureter exits
Kidney Structure
Cortex
Outer layer
Medulla
Inner layer
Pyramids
Papillae
Apices of pyramids
Calyces
Funnel urine to pelvis
Ureter
Urine from pelvis to bladder
Microstructure
Nephron —functional unit
Glomerulus
Bowman’s capsule
Tubular system—proximal convoluted tubule, loop of
Henle, and collecting tubules
Cortex—glomerulus, Bowman’s capsule, and
proximal tubule
Medulla—loop of Henle and collecting tubules
Kidney Blood Supply
Blood flow to kidneys
1200 mL/min
20% to 25% of cardiac output
Aorta to renal artery; forms afferent arteriole and
divides to form glomerulus (capillary network); unites
in efferent arteriole to form peritubular capillaries;
empty into renal vein; empties into inferior vena cava
Urine Formation
Physiology of urine formation
Outcome of complex, multistep process
* Filtration
* Reabsorption
* Secretion
* Excretion of water, electrolytes, and metabolic waste
products
Primary function of the kidneys
-Filter the blood
-Maintain internal homeostasis
Glomerulus
Glomerular function
Blood is filtered by hydrostatic pressure
Passes through semipermeable membrane into
Bowman’s capsule
Glomerular filtrate passes down tubule
* Normally, filtrate does not contain blood cells, platelets, or large plasma proteins
Glomerular filtration rate (GFR)
* Normal is ~125 mL/min
* Only average of 1 mL/min excreted as urine after
reabsorption processes
Tubular Function
Reabsorbs essential materials, excretes
nonessential ones
Reabsorption: from tubules to capillaries
Secretion: from capillaries to tubules
* Proximal convoluted tubule: 80% electrolytes 100% glucose, amino acids, and small proteins; secretion H+ and creatinine
* Loop of Henle: reabsorb Na+, Cl− and water
* Descending limb: water, some sodium, urea, other solutes
* Ascending limb: chloride, sodium
Distal convoluted tubule: water balance
Antidiuretic hormone (ADH)
* Important in water balance
* Regulated by posterior pituitary gland
Aldosterone
* Reabsorption of Na+ and water; excrete K+
* Released from adrenal cortex
Distal convoluted tubule: acid-base balance
Bicarbonate (HCO3−) reabsorbed
Hydrogen ions (H+) secreted
Maintain ECF pH 7.35 to 7.45
Right atrium: water balance
Atrial natriuretic peptide (ANP)—increases Na+
excretion; inhibits renin, ADH, and angiotensin II to
suppress aldosterone; increased GFR causing
increased urine output
Renal tubules: calcium (Ca2+) balance
Parathyroid hormone (PTH) — Ca2+ reabsorption;
decreased phosphate (PO42− ) reabsorption
Vitamin D activation
Needed to absorb Ca2+ from GI tract
Other Kidney Functions
Other functions of kidneys
Red blood cell (RBC) production
* Erythropoietin—hormone secreted in response to
hypoxia and decreased renal blood flow
BP regulation
* Renin-angiotensin-aldosterone system
* Prostaglandin synthesis—vasodilation; decreased BP
and SVR
Ureters
Ureters
Carry urine from pelvis to bladder
* 10 to 2” peristaltic, one-way flow
Ureter joins
* Renal pelvis at the ureteropelvic junction (UPJ)
* Bladder at the ureterovesical junction (UVJ)
Narrowed at junctions—obstruction –> renal colic
Reflux can occur with incomplete UVJ closure
Bladder
Bladder
Serves as a reservoir for urine; does not absorb;
uroepithelium stretches
* Normal adult urine output: 1500 mL/day
* 200 to 250 mL—mild distention and urge to urinate
* 400 to 600 mL—moderate distention—uncomfortable
* 600 to 1000 mL capacity
Trigone: 2 ureteral openings and bladder neck
Bladder muscle (detrusor)
Urachus—attachment to abdominal wall
Urination, micturition, voiding
Urethrovesical unit
Formed by bladder, urethra, and pelvic floor muscles
Voluntary control = continence
* Distention of bladder stimulates stretch receptors
* Impulses sent from brain to T11-L2 and S2-S4
* Not time to void—inhibitor impulses stimulated
* Time to void—impulses from spinal cord causes
relaxation and contraction of bladder neck, sphincter,
and pelvic floor muscles
Gerontologic Considerations
Effects of Aging on Urinary System
Anatomic changes
10% decrease in size, weight, blood flow each
decade starting at age 30, similar decline in
glomerular function starting at age 40
Atherosclerosis accelerates decrease of renal size
with age
* Decreased GFR and urinary concentrating ability
Yet, continue to maintain fluid homeostasis
Kidney
Decreased renal blood flow causes decreased GFR
Altered hormonal levels result in:
* Decreased ability to concentrate urine
* Altered excretion of water, sodium, potassium, & acid
Urethra and Bladder
Female: decreased elasticity and muscle support —
increased infections and incontinence
Male: enlarged prostate alters urinary patterns
Assessment of Urinary System
Subjective Data
Functional health patterns
Health perception–Health management pattern
Nutritional–metabolic pattern
Elimination pattern
* General manifestations, edema, pain, patterns of
urination, urine output and urine composition
Activity–exercise pattern
Functional health patterns
Sleep–rest pattern
* Nocturia
Cognitive–perceptual pattern
* Mobility, visual acuity, dexterity, incontinence, pain
Self‑ Perception–self‑ concept pattern
Role–relationship pattern
Sexuality–reproductive pattern
* Incontinence is not directly related to sexual problems,
but can have devastating effects on self-esteem and
intimate relationships
