The Urinary System Flashcards
Name the basic urinary system parts and functions
a. Kidneys are major excretory organs
b. Urinary bladder is the temporary storage reservoir for urine
c. Ureters transport urine from the kidneys to the bladder
d. Urethra transports urine out of the body
What is the function of the kidneys?
a. Removal of toxins, metabolic wastes, and excess ions from the blood
b. Regulation of blood volume, chemical composition, and pH (through buffer system)
c. Endocrine functions
i. Renin: regulation of blood pressure and kidney function
ii. Erythropoietin: regulation of RBC production
Describe the general parts of the kidney
a. Retroperitoneal, in the superior lumbar region
b. Right kidney is lower than the left
c. Ureters, renal blood vessels, lymphatics, and nerves enter and exit at the hilum
Name the layers of supportive tissue
a. Renal fascia- The anchoring outer layer of dense fibrous connective tissue
b. Perirenal fat capsule- A fatty cushion
c. Fibrous capsule- Prevents spread of infection to kidney
Describe the internal anatomy of the kidney
a. Renal cortex- A superficial region with over 1 million renal corpuscles
b. Renal medulla- Triangular renal pyramids separated by renal columns
c. Papilla- Tip of pyramid; releases urine into minor calyx
What are the major calyces?
a. The branching channels of the renal pelvis that
b. Collect urine from minor calyces
c. Empty urine into the ureter
Describe blood and nerve supply to the kidneys
a. Renal arteries deliver 25% of cardiac output to the kidneys each minute
b. Arterial flow into and venous flow out of the kidneys follow similar paths
What are nephrons?
a. Structural and functional units that form urine
b. ~1.5 million per kidney
What are the two main parts of the nephrons?
a. Glomerulus: a tuft of capillaries
b. Renal tubule: begins as cup-shaped glomerular (Bowman’s) capsule surrounding the glomerulus
Describe the arterial pathway into the kidney
a. Renal artery
b. Segmental artery
c. Interlobar artery
d. Arcuate artery
e. Cortical radiate artery into the nephron
f. Afferent arteriole
g. Glomerulus capillaries
h. Efferent arteriole
Describe the vein pathway out of the kidney
a. Peritubular capillaries and vasa recta
b. Cortical radiate vein
c. Arcuate vein
d. Interlobar vein
e. Renal vein
f. Inferior vena cava
Describe renal corpuscle of nephron
a. Renal corpuscle = Glomerulus + its glomerular capsule
b. Afferent arteriole → glomerulus → efferent arteriole
c. Specialized for filtration
d. Blood pressure is high because afferent arterioles are smaller than efferent arterioles*
Describe the PCT of the renal tubule
a. Proximal convoluted tubule (PCT)
b. Found only in the cortex
c. Functions in reabsorption and secretion
Describe the loop of Henle of the renal tubule
a. Loop of Henle with descending and ascending limbs
i. Descending limb
ii. Simple squamous epithelium
b. Freely permeable to water
c. Ascending limb
i. Cuboidal and columnar cells
ii. Impermeable to water
Describe the DCT of the kidney
a. Distal convoluted tubule (DCT)
b. Function more in secretion than reabsorption
c. Confined to the cortex
Describe the collecting ducts of the kidney
a. Receive filtrate from many nephrons
b. Fuse together to deliver urine through papillae into minor calyces
Describe the peritubular capillaries
a. Surround PCT and DCT of cortical nephrons
b. Low-pressure, porous capillaries adapted for absorption
c. Arise from efferent arterioles
d. Empty into venules, then into the cortical radiate vein
Describe the vasa recta
a. Long vessels surrounding long loops of Henle of juxtamedullary nephrons
b. Also arise from efferent arterioles
c. Also empty into venules, then into the cortical radiate vein
Describe the mechanisms of urine formation
a. The kidneys filter the body’s entire plasma volume 60 times each day
b. Filtrate
i. Blood plasma minus proteins
c. Urine
i. <1% of total filtrate
ii. Contains metabolic wastes and unneeded substances
Describe the mechanical steps of urine formation
a. Glomerular filtration
b. Tubular reabsorption (leaves nephron tubules and enters blood)
i. Returns all nutrients and amino acids
ii. Returns 99% of water, salt (NaCl), and other electrolytes to the blood
c. Tubular secretion (waste enters nephron tubules from the blood)
i. Selective addition to urine (extra waste)
Describe glomerular filtration
a. Driven by hydrostatic pressure
b. The glomerulus is a very efficient filter because
i. Its filtration membrane is very permeable and it has a large surface area
ii. Glomerular blood pressure is much higher (55 mm Hg) than other capillaries
c. GFR is the volume of filtrate formed per minute by the kidneys
i. NFP (net filtration pressure)
Describe net filtration pressure (NFP)
a. The pressure responsible for filtrate formation
b. Determined by adding the applicable forces:
i. A pushing force:
ii. Glomerular hydrostatic pressure (HPg=55)
c. Two opposing forces:
i. Colloid osmotic pressure of glomerulus (OPg=30)
ii. Capsular hydrostatic pressure (HPc=15)
d. NFP = HPg – (OPg + HPc)
How are organic nutrients, water, and ions reabsorbed from nephron into peritubular capillaries?** True, but we did a slightly different way
a. All organic nutrients are reabsorbed by active transport
b. Water and ion reabsorption are hormonally regulated
What two routes can substances take during reabsorption?
a. Transcellular – through the cells
b. Paracellular – between the cells
How are Na+, water, cations, and fat-soluble substances transported?
a. Na+ (most abundant cation in filtrate)-
Actively transported out of the tubule by Na+-K+ pumps
b. Water is reabsorbed by osmosis, aided by pores called aquaporins
c. Other cations and fat-soluble substances exit via diffusion
Name and describe the reabsorptive capabilities of PCT
a. Site of most reabsorption
b. 65% of Na+ and water
c. All nutrients
d. Bicarbonate and other electrolytes
e. Small proteins and AAs
Name and describe the reabsorptive capabilities of Loop of Henle
a. Descending limb: H2O
b. Ascending limb: Na+, K+, Cl−
Describe which hormones are reabsorbed in DCT
a. Ca2+ (PTH)
b. Na+ (aldosterone) Cl - follows the Na+
What is reasbsorbed in the Collecting duct?
Water (ADH)
Describe tubular secretion from peritubular capillaries to nephron
a. Eliminates undesirable substances like urea and uric acid
b. Rids the body of excess K+
c. Controls blood pH by altering amounts of H+ or HCO3– in urine
Describe regulation of urine concentration and volume
a. Osmolality of body fluids
iii. The kidneys maintain osmolality using countercurrent mechanisms
Describe when the countercurrent mechanism occurs
a. Occurs when fluid flows in opposite directions in two adjacent segments of the same tube
i. Filtrate flow in the loop of Henle (countercurrent)
ii. Blood flow in the vasa recta (countercurrent)
What is the role of countercurrent mechanisms? (not important)
a. Establish and maintain an osmotic gradient from renal cortex through the medulla
b. Allow the kidneys to vary urine concentration
How is urea recycled?
a. Urea moves between the collecting ducts and the loop of Henle
i. Secreted into filtrate by facilitated diffusion in the ascending thin segment
b. Contributes to the high osmolality in the medulla
Describe the color and transparency of urine (WTF…)
a. Clear, pale to deep yellow (due to urochrome)
b. Drugs, vitamin supplements, and diet can alter the color
c. Cloudy urine may indicate a urinary tract infection
Describe the pH, gravity, and odor of urine
a. ~pH 6, with a range of 4.5 to 8.0 (wide range)
b. Specific gravity
i. 1.001 to 1.035, dependent on solute concentration
c. Odor
i. Slightly aromatic when fresh
ii. Develops ammonia odor upon standing
iii. May be altered by some drugs and vegetables
What is the chemical composition of urine?
a. 95% water and 5% solutes
b. Nitrogenous wastes: urea, uric acid, and creatinine
c. Other normal solutes
Describe the ureters
a. Move urine from kidneys to bladder
b. Retroperitoneal
c. Enter the base of the bladder through the posterior wall
i. As bladder pressure increases, distal ends of the ureters close, preventing backflow of urine
Define and describe renal calculi
a. Kidney stones form in renal pelvis
i. Crystallized calcium, magnesium, or uric acid salts
b. Larger stones block ureter, cause pressure and pain in kidneys
Describe the urinary bladder
a. Muscular sac for temporary storage of urine
b. Retroperitoneal, on pelvic floor posterior to pubic symphysis
i. Males—prostate gland surrounds the neck inferiorly
ii. Females—anterior to the vagina and uterus
c. Detrusor muscle (three layers of smooth muscle) allows forceful expulsion of urine
d. Trigone
i. Smooth triangular area outlined by the openings for the ureters and the urethra
ii. Infections tend to persist in this region
Describe the female urethra
a. Female urethra (3–4 cm):
i. External urethral orifice is anterior to the vaginal opening, posterior to the clitoris
Describe the male urethra
a. Selectively carries both semen and urine
b. Three named regions
i. Prostatic urethra (2.5 cm)—within prostate gland
ii. Membranous urethra (2 cm)—passes through the urogenital diaphragm
iii. Spongy urethra (15 cm)—passes through the penis and opens via the external urethral orifice
What controls micturition?
Pontine control centers mature between ages 2 and 3
