chapter 18 the urinary system Flashcards
What does the urinary system consist of?
two kidneys, two ureters, the urinary bladder and the urethra
Functions of the urinary system?
-formation and removal of urine
-regulation of the volume of blood by excretion or conservation of water
-regulation of the electrolyte content of the blood
-regulation of the acid-base balance of blood
Where are the kidneys located?
upper abdominal cavity on either side of the vertebral column behind the peritoneum
what is the renal fascia?
fibrous connective tissue that helps hold the kidneys in place
what is the hilus?
passageway for ureters, vessels and nerves
What is the renal cortex?
outer tissue layer of the kidney and is made of corpuscles and convoluted tubules
What is the renal medulla?
inner tissue layer of the kidney made of loops of Henle and collecting tubules
what are the renal pyramids?
wedge shaped pieces
tip of each pyramid is its apex or papilla
what is the renal pelvis?
cavity formed by the expansion of the ureter within the kidney at the hilus
includes calyces- enclose the papillae of the renal pyramids
How does urine flow?
from the renal pyramids into the calyces, then to the renal pelvis and out into the ureter
What is the nephron?
the structural and functional unit of the kidney
each kidney contains approximately 1 million nephrons
has 2 major portions: renal corpuscle, renal tubule
what is the renal corpuscle?
consists of a glomerulus surrounded by a bowmans capsule
what is the glomerulus?
a capillary network that arises from an afferent arteriole and empties into an efferent arteriole
What is the bowmans capsule?
the expanded end of a renal tubule, encloses the glomerulus
inner layer made of podocytes which creates pores which makes the layer permeable
outer layer has no pores and is not permeable
What is the space between the inner and outer layers of bowmans capsule?
contains renal filtrate which is the fluid that is formed from the blood in the glomerulus and eventually becomes urine
What is the renal tubule?
comes from bowmans capsule and consists of:
proximal convoluted tubule
loop of Henle
distal convoluted tubule
Where does the distal convoluted tubule empty into?
a collecting tubule
What do the collecting tubules do?
they unite to form a papillary duct that empties urine into a calyx of the renal pelvis
What are the renal tubules surrounded by?
peritubular capillaries, which arise from the efferent arterioles
What is urine made out of?
blood plasma
pathway of blood flow through the kidney
enter the renal artery, through the afferent arterioles into the glomeruli to efferent arterioles, to peritubular capillaries to a series of veins. renal vein empties blood into the inferior vena cava
What processes do the formation of urine involve?
glomerular filtration, tubular reabsorption and tubular secretion
What happens in glomerular filtration?
blood pressure forces plasma, dissolved substances, and small proteins out of the glomeruli and into the bowmans capsules
fluid is no longer plasma but renal filtrate
What is the blood pressure in the glomeruli?
50 to 60 mm hg
relatively higher than other capillaries
What is the blood pressure in bowmans capsules?
very low
20% to 25% of the blood that enters glomeruli is forced out and becomes renal filtrate in bowmans capsules
What doesn’t become part of renal filtrate?
large proteins, and blood cells
What becomes part of renal filtrate?
waste products, vitamins and minerals are dissolved in blood plasma and become part of renal filtrate
What is the glomerular filtration rate? (GFR)
the amount of renal filtrate formed by the kidneys in 1 minute and averages 100 to 125 ml per minute
What is tubular reabsorption?
takes place from the renal tubules into the peritubular capillaries
most reabsorption and secretion take place where?
proximal convolutes tubules
What is active transport in the kidney?
cells of the renal tubule use ATP to transport most of the useful materials from the filtrate to the blood
Ex: glucose, amino acids, vitamins, and positive ions
What is passive transport in the kidney?
negative ions that are returned to the blood are reabsorbed following the reabsorption of positive ions
What is osmosis in the kidney?
the reabsorption of water follows the reabsorption of minerals especially sodium ions
What is pinocytosis in the kidney?
small proteins are reabsorbed to the membranes of the cells of the proximal convoluted tubules
what is the threshold level of reabsorption?
the maximum amount of glucose or amino acids that may be reabsorbed back into the kidney
What happens in tubular secretion?
substances are actively secreted from the blood in the peritubular capillaries into the filtrate in the renal tubules
The process of tubular transports these to the filtrate
waste products such as ammonia and creatine
metabolic products of medications
What is an important function of the kidney?
remove and excrete excess hydrogen ions from the blood
ADH hormone (posterior pituitary)
increases reabsorption of water from the filtrate to the blood. (urinary output decreases)
Parathyroid Hormone (parathyroid glands)
increase reabsorption of Ca+2 ions from filtrate to the blood
excretion of phosphate ions into the filtrate
Aldosterone (adrenal cortex)
increases reabsorption of Na+ ions from filtrate to the blood
excretion of K+ ions into the filtrate
water is reabsorbed following the reabsorption of sodium
(urinary output decreases)
Atrial Natriuretic peptide (atria of heart)
decreases reabsorption of Na+ ions which remain in the filtrate
sodium and water are eliminated in urine
(urinary output increases)
What organs are the most responsible for maintaining PH of blood and tissue fluid?
Kidneys
If body fluids are becoming too acidic, what does the kidney do?
secret more H+ ions into renal filtrate
return more HCO3- ions to the blood
raises PH levels back to normal
If body fluids are becoming too alkaline, what does the kidney do?
return H+ ions to the blood and excrete HCO3- ions in urine
lower PH levels back to normal
What are other functions of kidneys?
secretion of renin- blood pressure decreases
secretion of erythropoietin- blood oxygen level decreases
activation of vitamin D-
What are the ureters, urinary bladder, and urethra responsible for?
periodic elimination of urine
What are ureters?
lower posterior side of the urinary bladder
propels urine toward the urinary bladder
What is the location of urinary bladder in men and women?
women- bladder inferior to the uterus
men- bladder is superior to the prostate gland
what is the function of the bladder?
a reservoir for accumulating urine, and it contracts to eliminate urine
the part of the urinary bladder that expels urine from the bladder?
detrusor muscle
the part of the urinary bladder that permits expansion without tearing the lining?
rugae
the internal urethral sphincter is?
part of the urinary bladder that prevents outflow of urine
involuntary
What is the urethra?
carries urine from the bladder to the exterior
How long is the urethra in men and women?
women: 1-1.5 inches
men: 7 to 8 inches
Voluntary control of the urinary reflex is provided by __, which __
external urethra sphincter/ contracts to prevent urination
the part of the CNS that is directly involved with in the urination reflex is the?
spinal cord
What is urination also called?
micturition or voiding
normal urine amount
1-2 liters per 24 hours
depends on fluid intake
normal color of urine
straw or amber; darker means more concentrated, should be clear not cloudy
specific gravity of urine
1.010-1.025; a measure of the dissolved material in urine
lower the value=more diluted
normal PH of urine
range 4.6-8.0
average 6
diet has greatest effect on ph
composition of urine
95% water; 5% salts and waste products
nitrogenous waste of urine
urea- from amino acid metabolism
creatine- from muscle metabolism
uric acid- from nucleic acid metabolism
Glycosuria
presence of glucose in urine
Proteinuria
presence of protein in urine
Hematuria
presence of blood in urine
Bacteriuria
presence of bacteria in blood
Ketonuria
presence of ketones in urine
