Urinary System Part 1 Flashcards
External Structures of the Kidney:
-Kidneys
Retroperitoneal- location
Renal capsule- surrounds each
- Imbedded in mass of fat
Renal fascia- fibrous tissue surrounding the capsule and fat layer that attaches the kidney to posterior abdominal wall
- Hilum- medial indentation for entry/exit blood vessels, nerves, lymph vessels, ureter
Structures of the Kidney
- Renal cortex
- Renal medulla
- Renal pyramids
- Renal columns
- Minor calyx
- Major calyx
- Renal pelvis
Nephron
Nephron 1.2 million nephrons per kidney Functional unit of the kidney 3 kinds Superficial cortical nephrons Extend partially into medulla Midcortical nephrons Juxtamedullary nephrons Extend deep into medulla- urine concentration
Nephron- Tubular structure with subunits that contribute to urine formation
- Renal corpuscle
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
Nephron- Tubular structure with subunits that contribute to urine formation:
-Renal corpuscle
Glomerulus- “tuft of capillaries”
Bowman capsule
Mesangial cells-support, contractile, phagocytic, produce vasoactive substances, control flow
Bowman space- Space inside Bowman’s capsule
Nephron
- Glomerular filtration membrane (wall of glomerular capillary for filtration)
- Glomerular endothelium
- Basement membrane
–Capillary epithelium
Also referred to as podocytes or visceral epithelium
Filtration slits
Nephron
Juxtaglomerular apparatus
- Juxtaglomerular cells- around the afferent arteriole where it enters renal corpuscle
- Macula densa- portion of distal convoluted tubule with specialized sodium and chloride sensing cells.
Nephron
- Renal tubules Proximal tubule Loop of Henle Distal tubule Collecting duct --- Principal cells-resorb Na and H2O, secrete K --- Intercalated cells- secrete H, bicarbonate, resorb K
Structures of the kidney: Blood Vessels
- Renal arteries
- Interlobar arteries
- Arcuate arteries
- Interlobular arteries
- Afferent arterioles
- Glomerular capillaries
- Efferent arterioles
- Peritubular capillaries and vasa recta
Ureters
- 30 cm long
- Long, intertwining muscle bundles
- Pass obliquely though posterior aspect of bladder
- Peristaltic activity
- Micturition compresses the lower end of the ureter to avoid urine reflux
Bladder
- Detrusor muscle
- Transitional epithelium-barrier to prevent water and solutes moving between urine and blood
- Trigone- between openings ureters and urethra
- Micturition reflex
Urethra:
- internal and external sphincters (muscles)
- 3 to 4 cm in females
- 18 to 20 cm in males
Renal Blood flow:
Receive 1000 to -1200 mL of blood per minute
-Glomerular filtration rate (GFR)
1) Plasma vol per unit
time
2) Directly related to
perfusion pressure
in glomerular
capillaries
3)Directly related to
renal blood flow
(RBF)
Regulation of Renal Blood Flow:
- Autoregulation
- Try to keep RBF and GFR constant
- Myogenic mechanism
1) ↓Arterial pressure → ↓ stretch afferent arteriolar SM → arteriole relaxes → increase RBF
2) ↑ Arterial pressure → ↑ stretch afferent arteriolar SM → arteriole contracts → decrease RBF
-Tubuloglomerular feedback
–Macula densa cells sense flow and sodium and triggers compensatory changes in arteriolar resistance and GFR
Regulation of Renal Blood Flow:
Neural regulation
-Baroreceptor reflex response to Systemic BP
- Sympathetic ANS- NE stimulates
vasoconstriction when systemic BP decreases
Hormones
- Renin- angiotensin systems
- Natriuretic peptides- atrial natriuretic peptide (ANP) from right atrium
Renal Blood Flow: Nephron Function
-Glomerular filtration
The process of forming a protein-free plasma across the glomerular capillaries Net filtration pressure - Glomerular hydrostatic pressure -Capsular hydrostatic pressure - Blood oncotic pressure Filtration rate
Glomerular Filtration: Nephron Function
- Tubular reabsorption
-Tubular secretion
-Excretion
-Tubular transport
Proximal tubule
Loop of Henle and distal tubule
Glomerulotubular balance- proximal tubule adjusts rate to counter GFR to maintain Na and water balance
Tubular reabsorption:
- Movement fluids and solutes from the tubular lumen to the peritubular capillary plasma
- Mechanisms are both active and passive
Tubular Secretion:
- transfer of substances from the plasma of peritubular capillary to the tubular lumen
- Not water
- Transport mechanisms are both active and passive
Excretion:
-Elimination of urine
Tubular Transport:
-General name for movement of ions or water across the tubule membranes
Nephron Function- Simultaneous
Concentration and Dilution of Urine
Countercurrent exchange system
- Contributes to production of concentrated urine
- Fluid flows in opposite direction through parallel tubes
- Fluid moves up and down the parallel limbs of the loop of Henle
- The longer the loop, the greater the concentration gradient
Concentration and Dilution of Urine:
- Urea
- Catecholamines
- Antidiuretic hormone (ADH)
- Urodilantin
- Natriuretic peptide
- Diuretics
Renal Hormones:
- Vitamin D
- Erythropoietin
Tests of Renal Function:
- Clearance and glomerular filtration rate Inulin Creatinine -Clearance and renal blood flow - Blood tests Plasma creatinine concentration Plasma cystatin C concentration Blood urea nitrogen (BUN)
Tests of Renal Function: Urinalysis
-Urine color
-Urine pH
-Specific gravity
-Urine sediment
RBCs
Casts
Crystals
WBCs
Tests of Renal Function: Urinalysis
-Urinalysis Reagent strips (dipsticks) Glucose Bilirubin Urobilinogen Leukocyte esterase Nitrates Ketones Proteins RBCs, hemoglobin, and myoglobin
Aging and Renal Function:
- Decrease in kidney size
-Decrease in renal blood flow and GFR
-Number of nephrons decrease due to renal vascular and perfusion changes
-Glomerular capillaries atrophy
-Tubular transport response decreases
-Increased bladder symptoms
Urgency, frequency, and nocturia