Ch.25: Urinary System Part 2: Flashcards
Urine formation and the adjustment of blood composition involves three processes:
Glomerular filtration
Tubular Reabsorption
Tubular Secretion
_______ contains unneeded substances such as excess salts, and metabolic waste.
Urine
_______ contains everything found in blood plasma except protiens
Filtrate
__________ __________, is a passive process in which hydrostatic pressure forces fluids and solutes through a membrane. Viewed as a simple mechanical filters because filtrate formation does not directly consume metabolic energy. NONSELECTIVE
Glomerular filtration
The _________ _______, lies between the blood and interior of the glomerular capsule. It’s porous membrane allows free passage of water and solutes smaller than plasma proteins
Filtration membrane
Filtration membrane has 3 layers:
- Fenestrated endothelium of the glomerular capillaries
- Basement membrane (negative charge)
- Foot processes of podocytes of the glomerular capsule
The visceral layer of the glomerular capsule is made of ___________ that have filtration slits between their foot processes.
Podocytes
Molecules such as _____, ______, ______ _____, _________ _______ pass freely from the blood into the glomerular capsule.
water, glucose, amino acids, and nitrogenous waste
_________ molecules pass with greater difficulty, barred from entering the tubule. Keeping the plasma proteins in the capillaries maintains the colloid osmotic pressure of the glomerular blood, preventing the loss of all its water to the capsular space
Larger
_________ _______ promote filtrate formation
Outward pressure
________ ________ in the glomerular capillaries is essentially glomerular blood pressure. It is the chief force pushing water and solutes out of the blood and across the filtration membrane. The BP in the glomerulus is extremely high. 55 mm Hg . Due to the high resistance of the efferent arteriole that feeds them.
Hydrostatic pressure
________ ______ _______ in the capsular space of the glomerular capsule would “pull” filtrate into the tubule. Pressure is essentially zero because no proteins enter the capsule.
Colloid osmotic pressure
______ _______ inhibit filtrate formation by opposing HP
inward pressure
The hydrostatic pressure in the capsular space and colloid osmotic pressure in the glomerular capsule determine the ____ ________ ______
net filtration pressure
The _________ ______ ______ is the volume of filtrate formed each minute by the combined activity of all 2 million glomeruli of the kidneys.
Glomerular filtration rate
______ is the main controllable factor. Controlled by the changing diameter of the afferent arteriole
NFP
________ ______ ___ surrounding these glomerulus capillaries can fine tune the GFR by contracting to adjust the total surface area available for filtration
Glomerular mesengial cells
_________ ________ are thousands of times more permeable than other capillaries because of their fenestrations
Glomerular capillaries
The 3 Mechanisms for GFR regulation:
Myogenic Mechanism
Tubular feedback Mechanism
Neural and Hormonal Mechanism
By adjusting its own resistance to blood flow, a process called _____ _________
renal autoregulation
________ ________ reflects a property of the smooth muscle, it contracts when stretched and relaxes. Rising Bp causes the afferent arteriole to constrict. This constriction restricts blood flow into the glomerulus and prevents glomerular blood flow into the glomerular blood pressure from rising to damaging levels. Vice versa
Mygoenic Mechanism
_________ _______ __________: is directed by the macula densa cells of the juxtaglomerular complex. Located in the ascending walls of the loop of henle. Responds to filtrate NaCl concentration. When GFR increases,leads to not enough time for re-absorption to occur, as well as the NaCl concentration remains high. The macula densa cells respond by releasing vasoconstrictors chemicals (ATP and others) that cause intense constriction of the afferent arteriole and reducing blood flow into the glomurulus. This drop in blood flow decreases NFP and GFR slowing the flow and allowing time. Vice versa
Tubuloglomerular feedback mechanism
When the volume of the extracellular fluid is normal and the sympathetic nervous system is at rest, the renal blood vessels are ______ and renal autoregulation mechanisms prevail.
dilate
When blood pressure falls, ___________ released by sympathetic nerve fibers and __________ released by the adrenal medulla causes vascular smooth muscle to constrict, increasing peripheral resistance and bringing blood pressure back up toward normal
Norepinephrine and epinephrin
The ______ ______ _______ mechanism is the body’s main mechanism for increasing the blood pressure. Regulates GFR indirectly
Renin-angiotensin-aldosterone
Low blood pressure causes the granular cells of the JGC to release ________.
Rennin
_________ __________ is SELECTIVE transepithelial process that begins as soon as the filtrate enters the proximal tubules.
Tubular Reabsorption
Reabsorbed items include:
glucose, amino acids, water, sodium
Normally, the _____ reabsorbes all of the glucose and amino acids in the filtrate and 65% of the Na+ and water
PCT
Water can leave the ___________ limb of the nephron loop but not the ________ limb, where aquaporins are scarce or absent in the tubule cell membrane
Descending/ Ascending
Virtually no ________ reabsorption occurs in the descending limb of the nephron loop, but they are reabsorbed both actively and passively in the ascending limb,
Solute
______ inhibits diuresis or urine output. Makes the principle cells of the collecting ducts more permeable to water by causing aquaporins to be inserted into their apical membranes.
ADH (Antidiuretic hormone)
__________ fine tunes reabsorptions of the remaining Na+, increases blood volume or pressure. Conserve Na+
Aldosterone
_________, reduces blood Na+ thereby decreasing blood volume and pressure. Released by cardiac atrial cells when blood volume/ pressure is elevated.
ANP (atrial natriuretic peptide)
___________ ___________: moves selected substances from the peritubular capillaries through the tubule cells into the filtrate.
Tubular secretion
4 Importance of Tubular Secretion:
- Disposing of substances (drugs and toxins)
- Eliminating undesirable substances or end products
- Ridding the body of excess K+
- Controlling blood pH
_________, chemicals that enhance urinary output, Alcohol inhibits ADH. Most ??? inhibit Na+ associated symporters
Diuretics
