lecture exam 4 Flashcards
what are the functions of the urinary system?
regulates: water balance, blood volume, blood pressure, and blood osmolarity. removes harmful substances such as nitrogenous wastes and excretes as urine. produces hormone erythropoietin. converts inactive vitamin d to active form (calcitriol).
What gland sits atop each kidney?
adrenal glands
What are the three layers of supportive tissue that surround each kidney?
Renal fascia is the superficial layer, it anchors the kidneys to surrounding structures. The middle layer is the perirenal fat capsule that provides cushioning. The deepest layer is the fibrous capsule, a clear membrane directly attached to the kidney.
What are the anatomical structures that urine would passes as it moves from the glomerulus to the urinary bladder?
Glomerulus → proximal convoluted tubule → loop of Henle → distal convoluted tubule → collecting duct → minor calyx → major calyx → renal pelvis → ureter → urinary bladder
Be able list the path of blood flow through the renal blood vessels.
Renal artery → segmental artery →interlobar artery → arcuate artery → cortical radiate artery (interlobular) → afferent arteriole → glomerulus → efferent arteriole → peritubular capillaries (and vasa recta for juxtamedullary nephrons) → cortical radiate vein (interlobular) → arcuate vein → interlobar vein → renal vein.
What is the nephron? Be able to label all major parts of a nephron, and know differences between
cortical and juxtamedullary nephrons.
Nephron is the functional unit of the kidney that forms urine by
filtering blood.
What are all parts and features of the renal corpuscle?
Renal corpuscle consists of two parts, the glomerulus and the Bowman’s (glomerular) capsule, and the space between them is the capsular space.
Large cells called podocytes sit on the glomerulus and create large filtration slits with their cellular projections (pedicels).
How does the glomerulus differ from other capillaries in the body?
larger pores and higher pressure
What is the function of the juxtaglomerular apparatus? Be able to list and define it major components. What is the function of the macula densa cells; where are they found?
Juxtaglomerular apparatus is the
junction of the afferent arteriole and ascending limb of the loop of Henle meet; this junction monitors blood pressure of the afferent arteriole via granular (juxtaglomerular) cells, and it also monitors solute concentration in the loop of Henle via macula densa cells.
What factors and pressures affect glomerular filtration rate? What factors can be implemented to increase or decrease the filtration rate? What is the chief force pushing water and solutes out of the blood across the filtration membrane? What would happen if the capsular hydrostatic pressure were increased above normal? Decreased? How is the fluid in the glomerular (Bowman’s) capsule similar/different from blood plasma?
Hydrostatic pressure is the main force that pushes solutes from the glomerulus into the capsular space. It is a passive process and occurs in only one direction. Blood cells and proteins are too large to fit through the filtration slits, creating colloid osmotic force. This force opposes hydrostatic pressure, ensuring substances continue to move from the glomerulus to the capsular space. Vasoconstriction or vasodilation of the afferent arteriole is the main method to control filtration rate (by controlling blood pressure entering the glomerulus). The fluid in the Bowman’s capsule does not contain proteins, whereas our blood plasma contains many proteins.
What are the three layers of the filtration membrane?
Capillary endothelium (prevents blood cells), basement membrane (prevents large proteins), and filtration slits created by podocytes (prevents small
proteins).
What is the function of each of the following hormones: antidiuretic hormone (ADH), aldosterone, angiotensin (ll), atrial natriuretic peptide, parathyroid hormone (PTH), and epinephrine
ADH: promotes water reabsorption in DCT/collecting duct by increasing aquaporins, aldosterone: promotes sodium reabsorption (and potassium secretion), angiotensin (ll): promotes sodium and water reabsorption, atrial natriuretic peptide: inhibits sodium reabsorption, parathyroid hormone: inhibits phosphate reabsorption and promotes calcium reabsorption, epinephrine: decreases urine output.
What stimulates the kidneys to produce renin?
Decrease in blood pressure
What takes place during tubular reabsorption?
Desirable contents such as sodium, glucose, amino acids, etc., move from the renal tubule into the peritubular capillaries in order to stay in the blood. Substances can move by either active or passive transport through the tubular cells (transcellular) or between the tubular cells (paracellular). Sodium reabsorption is primary active transport, carried out by a transport protein called a symporter. Most other nutrients are reabsorbed via secondary active transport by “piggybacking” on the sodium symporter.
What are the most important hormone regulators of electrolyte reabsorption and secretion?
Aldosterone increases sodium reabsorption, ANP inhibits sodium reabsorption, parathyroid hormone
increases calcium reabsorption.
water follows __
sodium
What substance (i.e. ions) directly affect the reabsorption of virtually every other nutrient?
sodium and water
Describe the concept of transport maximum (Tm). How does it help regulate electrolyte homeostasis?
Nutrient reabsorption is mostly done via symporters (active transport proteins), and when all symporters are active the transport maximum is reached and all nutrients will be secreted until symporters become available. Helps prevent an overabundance of nutrients.
What is the function of the loop of Henle? How does it establish the medullary osmotic gradient?
The loop of Henle allows the nephron to concentrate urine by fluid moving in opposite directions through
semipermeable tubes, adjusting the concentration throughout.
Describe the differences in permeability of the descending limb and ascending of the loop of Henle
(differentiate the thick and thin segments).
The descending limb (thin) allows only water to diffuse, and the ascending limb (thick) allows electrolytes to only diffuse
The mechanism that establishes the ___ depends most on the permeability properties of the loop of Henle.
medullary osmotic gradient
What substances are reabsorbed in the PCT, descending limb and ascending of the loop of Henle, DCT, and collecting duct? What substances are secreted or not reabsorbed? What are reasons why substances are either not reabsorbed or are incompletely reabsorbed from the nephron?
Reabsorbed in PCT is most filtrate (water, ions, nutrients, etc.), secreted in PCT is hydrogen, ammonia, and drugs. Descending limb of loop secretes water only, ascending limb of loop secretes electrolytes only. Reabsorption in DCT/collecting duct regulated by hormones: Aldosterone increases sodium reabsorption and increases calcium secretion, parathyroid hormone increases calcium reabsorption, and ADH increases water reabsorption. Substances will be secreted if they are waste products, toxic, or excess solutes; examples are H+, K+, NH4 +, creatine, etc.
How can cells of the renal tubules raise or lower blood pH?
Acids produced by cellular metabolism accumulate in the blood, which increases acidity (lowers pH), and need to be removed. The main method to raise the pH (remove excess hydrogen ions) is to combine bicarbonate ions that act as a buffer to the hydrogen, which neutralizes it. To lower pH (increase hydrogen ions), carbonic acid can dissociate into hydrogen and bicarbonate.
Why does alcohol acts as a diuretic?
Inhibits the release of ADH, meaning less water is reabsorbed and instead is secreted in urine.
How is dilute or concentrated urine manufactured?
ADH controls the amount of water that is reabsorbed; large amounts of ADH secretion results in higher water reabsorption, which concentrates the urine. If no ADH is secreted, the DCT/collecting duct are impermeable to water.
Normal blood osmolality is approximately __ mOsm/kg.
300
Define the following: electrolytes, nonelectrolytes, intracellular, interstitium.
Electrolytes dissociate in water to ions and include inorganic salts, acids, bases, etc., and they have high osmotic power (have an electrical charge). Nonelectrolytes do not dissociate in water and include glucose, lipids, urea, creatine, etc., and carry no electrical charge. Intracellular means within a cell, and interstitial means between cells.
Describe how body water content changes throughout life
Infants are roughly 75% water as they have low body fat and bone mass. As they develop the water content slowly decreases, reaching about 60% water for adult males and about 50% water for adult females (due to higher fat content and less muscle mass). Elderly have around 45% water content.
What is the blood component that links the external and internal fluid compartments?
plasma
What forces regulate the movement of fluids between cellular compartments? What force causes net water flow across capillary walls?
Hydrostatic pressure and osmotic pressure regulate movement between compartments.
What ion(s) is highest in the intracellular fluid? What ion(s) is highest in the interstitial fluid and blood?
Intracellular fluids are high in potassium, hydrogen, phosphate and low in sodium, chloride, and bicarbonate. Extracellular fluids are high in sodium, chloride, bicarbonate and low in potassium, calcium, and phosphate.
