Chapter 19 - Urinary System Flashcards
Functions
- filters metabolic wastes and toxins from plasma
- metabolizes drugs and toxins
- regulates electrolyte comp. and volume in plasma
- helps maintain blood pH and HCO3
- produces urine
- synthesizes hormones renin and EPO
Renin
hormone that helps regulate blood volume and BP
- constricts arterioles, stimulating aldosterone and ADH secretion
Erythropoietin
hormone that controls RBC formation and maturation
Nephron
- microscopic functional unit of the kidney
- renal corpuscle
- renal tubule
Renal corpuscle
- glomerulus
- Bowman’s capsule (visceral and parietal layers)
- macula densa
- juxtaglomerular cells
Renal tubule
- PCT
- loop of henle
- DCT
- sensory cells - point where the DCT makes contact w/ the macula densa
What is the order of function of the nephron?
1- blood enters glomerular capillaries from aff. arteriole; exits via eff. arteriole
2- filtrate enters Bowman’s space
3- PCT
4- Loop of henle
5- DCT
- most salts, water and nutrients are reabsorbed; additional waste products/drugs/toxins are secreted
6- collecting tubule, collecting duct
7- renal pelvis
Renal corpuscle
- filtration barrier
- capillary endothelial cells and visceral layer of bowman’s capsule and basal lamina - fenestrated capillaries
- podocytes have feet that envelop the capillaries
- glomerular filtration rate is about 120 mL/min
-fenestrated capillaries
PCT
- receive filtrate from Bowman’s space
- cuboidal epithelium w/ brush border and mitochondria
- majority of water and electrolytes reabsorbed here
- main site for reabsorption for nearly all organic nutrients like glucose and amino acids
- active transport couples to Na-K ATPase
Loop of henle
- U shaped part of renal tubule that extends into medulla
- reabsorbs 15-25% of H2O and salts - continues to absorb more water to maintain fluid homeostasis
Thin descending limb of loop of henle
- simple squamous epi
- permeable to H2O but not to salts
- H2O drawn out by osmosis due to hypertonic environment in medulla
Thick ascending limb of loop of henle
- simple cuboidal epithelium, lacking microvilli
- impermeable to H2O but reabsorbs salts
- responsible for hypertonic environment in medulla
DCT
- simple cuboidal epi, mainly mitochondria but no microvilli
- reabsorbs 5-15% of H2O and salts - final adjustment of K, H in tubular fluid
- principal site of active drug secretion, critical for drug elimination
- site of aldosterone action
Aldosterone action in DCT
- increases Na reabsorption and K secretion
- aids in NaCl retention
Juxtaglomerular apparatus
- group of cells adjacent to the glomerulus
- macula densa senses Na in filtrate
- if Na is low, JG cells secrete renin into aff. arteriole
- results in increase of BP and blood volume
- secrete EPO
Macula densa of juxtaglomerular app.
- specialized cells in DCT, adjacent to aff. arteriole
- sense Na in DCT filtrate
Juxtaglomerular cells of juxtaglomerular app.
- smooth muscle in aff. artiole tunic media, adjacent to macula densa
Collecting tubules and ducts
- conducts filtrate from end of nephron to renal papilla/minor calyces
- cuboidal cells, gradually becoming columnar as diameter of duct increases
- last point of salt and H2O reabsorption
- site of ADH action
ADH action in collecting tubules and ducts
- ADH increases H2O permeability of tubules/ducts
- allows formation of hypertonic urine
- if ADH is low, urine will be dilute
Ureter
- conducts urine from renal pelvis to urinary bladder
- transitional epith
- CT
- smooth muscle
- external CT
- distal portion is stratified squamous
- ureters, urinary bladder
Urinalysis
- med lab tests to measure concentration of various metabolites, glucose, blood, protein in urine
- proteinuria - elevated protein, indicates problem with glomerular filtration barrier
- hematuria - presence of RBCs, infection or problem with filtration barrier
Blood urea nitrogen
- concentration of urea in blood is an indicator of renal function
- urea is a product of protein catabolism
- urea itself is not toxic, but other nitrogenous wastes are and elevated levels cause cognitive impairment
Serum creatinine
- product of creatine-P breakdown in muscle
- elevated levels indicate renal failure
Hyperglycemia
- caused by lack of insule - insufficient secretion or insulin resistance
What does prolonged hyperglycemia cause?
- reduces glucose reabsorption by PCT -> high osmolarity filtrate -> reduced H2O reabsorption -> polyuria
What are the chronic complications of hyperglycemia?
- diabetic retinopathy
- diabetic neuropathy - proteinuria is an early sign
What structure is shown here? What does each letter indicate?
L1 - renal corpuscle
L2 - glomerulus
L3 - capsular space
R1 - PCT
R2 - DCT
R3 - Loop of Henle
R4 - Thin descending limb
R5 - Thick ascending limb
R6 - Renal tubule
