Ch. 26: Urinary System Flashcards
What main structures are involved in the urinary system?
Kidneys (2), ureters (2), urinary bladder, urethra.
Ureters.
Transport urine from the kidneys (renal pelvis) to the urinary bladder. Retroperitoneal.
Urinary bladder.
Stores urine and expels it into the urethra.
Urethra.
Discharges urine from the body. Small tube leading from the internal urethral orifice in the floor of the urinary bladder.
Kidney functions.
1) Waste excretion.
2) Regulation of blood ionic composition.
3) Regulation of blood pH.
4) Regulation of blood volume.
5) Regulation of blood pressure.
6) Maintenance of blood osmolarity.
7) Production of hormones.
8) Regulation of blood glucose level.
Nitrogenous wastes.
Waste products that contain nitrogen. Urea, ammonia, creatine, uric acid, urobilin.
How do the kidneys regulate blood ionic composition?
Adjust the amounts of Na+, K+, Ca2+, Cl-, HPO42- ions that are excreted in the urine.
How do the kidneys regulate blood pH?
They excrete a variable amount of H+ into the urine and conserve HCO3-, which is an important buffer of H+ in blood.
How do the kidneys regulate blood volume?
They conserve or eliminate water in the urine.
How do the kidneys regulate blood pressure?
They secrete renin, which activates the RAA pathway and increases BP.
How do the kidneys maintain blood osmolarity?
Maintain blood osmolarity at 300 mOsm/L by regulating loss of water and solutes in urine.
Which hormones do the kidneys produce?
Calcitriol and EPO.
How do the kidneys regulate blood glucose level?
Use glutamine in gluconeogenesis, and then release glucose into the blood.
If ribs ___ and ___ are fractured, they can puncture the ______ and cause life-threatening damage.
11, 12, kidneys.
Which kidney is slightly lower than the other because of the liver?
Right.
Renal hilum.
Indentation near the center of the concave border of each kidney. The ureter, blood vessels, lymphatic vessels and nerves emerge from this indentation.
What are the 3 layers of tissue around each kidney?
1) Renal capsule: deep, smooth, transparent sheet of dense irregular connective tissue, continuous with outer coat of ureter, barrier against trauma, helps maintain kidney shape.
2) Adipose capsule: middle, mass of fatty tissue surrounding renal capsule, barrier against trauma, holds kidney in place.
3) Renal fascia: superficial, thin layer of dense irregular connective tissue, anchors kidneys to surrounding structures and abdominal wall.
Renal cortex.
Superficial region within the kidney. Extends from renal capsule to the bases of the renal pyramids and into the spaces between them. Divided into an outer cortical zone and inner juxtamedullary zone.
Renal columns.
The portions of renal cortex that extend between the renal pyramids.
Renal medulla.
Inner region within the kidney. Consists of renal pyramids.
Parenchyma.
Functional part of the kidney. Renal cortex and renal pyramids together. Within the parenchyma are the nephrons, which are the functional units.
Filtrate formed by the nephrons drains into…
Large papillary ducts which extend through the renal papillae and into minor or major calyces. A minor calyx receives filtrate from the papillary ducts of one renal papilla and delivers it to a major calyx. Once the filtrate enters the calyces, it becomes urine. From the major calyces, urine drains into the renal pelvis (single large cavity) and then out through the ureter to the urinary bladder.
Each kidney has ___ major calyces and ___ minor calyces.
8-18, 2-3.
_____ receive 20-25% of the resting cardiac output via the right and left __________ .
Kidneys, renal arteries.
Renal blood flow is ____ mL per minute.
1200
Within the kidney, the renal artery divides into…
Segmental arteries. Each segmental artery gives off branches that enter the parenchyma and pass through the renal columns between the renal lobes as the interloper arteries.
A renal lobe consists of…
A renal pyramid, some of the renal column on either side of the renal pyramid, and the renal cortex at the base of the renal pyramid.
Arcuate arteries.
At the bases of the renal pyramids, the interlobar arteries arch between the renal medulla and cortex, where they are known as arcuate arteries. Divisions of these arteries produce a series of cortical radiate arteries, which radiate outward and enter the renal cortex where they give off afferent arterioles.
Each nephron receives one afferent arteriole which divides into a…
Glomerulus. The glomerular capillaries reunite to form an efferent arteriole that carries blood out of the glomerulus. The efferent arterioles divide to form the peritubular capillaries which surround tubular parts of the nephron in the renal cortex. Extending from some efferent arterioles are vasa recta that supply tubular portions of the nephron in the renal medulla. Peritubular capillaries eventually reunite to form cortical radiate veins which receive blood from the vasa recta. Then the blood drains through arcuate veins to the interlobar veins running between renal pyramids.
How are glomerular capillaries different than other capillaries in the body?
They are positioned between 2 arterioles rather than between an arteriole and a venule.
Blood leaves the kidney through…
A single vein that exits at the renal hilum and carries venous blood to the inferior vena cava.
Renal nerves are part of which division of the nervous system?
Sympathetic division of ANS.
What does a nephron consist of?
A renal corpuscle, and a renal tubule.
Renal corpuscle.
Where blood plasma is filtered. Glomerulus and glomerulus/Bowman’s capsule. Double-walled epithelial cup that surrounds the glomerular capillaries. Filtered fluid passes into the renal tubule. Within renal cortex.
Renal tubule.
PCT, nephron loop, DCT. Proximal denotes the part of the tubule attached to the glomerular capsule. Distal denotes the part of the tubule that is further away. Convoluted means the tubule is tightly coiled rather than straight. Within renal cortex.
The DCTs of several nephrons empty into…
A collecting duct. CDs then unite and converge into several hundred large papillary ducts which drain into the minor calyces.
Within a nephron, what does the nephron loop connect?
The PCT and DCT.
Cortical nephrons.
80-85% of nephrons. Their renal corpuscles lie in the outer part of the renal cortex. Short nephron loops that lie in the renal cortex and penetrate only into the outer part of the renal medulla. Nephron loops receive their blood supply from peritubular capillaries that arise from efferent arterioles.
Juxtamedullary nephrons.
15-20% of nephrons. Their renal corpuscles lie deep in the renal cortex close to the renal medulla. Long nephron loops that extend into the deepest region of the renal medulla. Nephron loops receive their blood supply from peritubular capillaries and vasa recta that arise from efferent arterioles. The ascending limb of this nephron loop consists of a thin ascending limb followed by a thick ascending limb. The lumen of the thin ascending limb is the same as in other areas of the renal tubule, it is only the epithelium that is thinner.
_____ nephrons enable the kidneys to excrete very dilute or very concentrated urine.
Juxtamedullary.
A single layer of ___ cells forms the entire wall of the glomerular capsule, renal tubule and ducts.
Epithelial.
What are the 2 layers of the glomerular capsule?
Visceral and parietal.
Visceral layer of glomerular capsule.
Modified squamous epithelial cells (podocytes). Pedicels wrap around the single layer of endothelial cells of the glomerular capillaries and form the inner wall of the capsule.
Parietal layer of glomerular capsule.
Simple squamous epithelium. Forms outer wall of capsule.
Fluid filtered from the glomerular capillaries enters which region of the glomerular capsule?
Capsular space between the visceral and parietal layers, which is continuous with the lumen of the renal tubule.
Proximal convoluted tubule.
Simple cuboidal epithelial cells. Brush border of microvilli on apical surface.
Which cells make up the descending limb and first part of the ascending limb of the nephron loop?
Simple squamous epithelium.
Which cells make up the thick ascending limb of the nephron loop?
Simple cuboidal to low columnar epithelium.
Juxtaglomerular apparatus.
Juxtaglomerular cells + macula densa. Regulates blood pressure within the kidneys.
Distal convoluted tubule.
Begins shortly after the macula densa. Principal cells, which have receptors for ADH and aldosterone. Intercalated cells, which play a role in the homeostasis of blood pH.
Signs of kidney dysfunction do not become apparent until function declines to less than ___ of normal because remaining nephrons adapt.
25%
Surgical removal of one kidney stimulates ____ of the remaining kidney.
Hypertrophy. The remaining kidney will be able to filter blood at 80% of the rate of 2 normal kidneys.
To produce urine, nephrons and collecting ducts perform which 3 basic processes?
1) Glomerular filtration.
2) Tubular reabsorption.
3) Tubular secretion.
Glomerular filtration.
Water and solutes in blood plasma move across the walls of glomerular capillaries, where they are filtered and move into the glomerular capsule and then renal tubule.
Tubular reabsorption.
As filtered fluid flows through the renal tubules and collecting ducts, tubule cells reabsorb 99% of the filtered water and solutes. The water and solutes return to the blood as it flows through the peritubular capillaries and vasa recta.
Tubular secretion.
As filtered fluid flows through renal tubules and collecting ducts, the renal tubule and duct cells secrete other materials into the fluid. Transfer of materials from the blood and tubule cells into the glomerular filtrate.
The rate of urinary excretion of any solute is…
Rate of glomerular filtration + rate of tubular secretion - rate of tubular reabsorption.
Glomerular filtrate.
Fluid that enters the capsular space of the glomerulus.
Filtration fraction.
The fraction of blood plasma in the afferent arterioles of the kidneys that becomes glomerular filtrate. Usually 150 L females, 180 L males.
Filtration membrane of glomerulus.
Glomerular capillaries and podocytes. Leaky barrier. Permits filtration of water and small solutes. Prevents filtration of most plasma proteins and blood cells. Consists of 3 filtration barriers.
What are the 3 filtration barriers of the filtration membrane of the glomerulus?
1) Glomerular endothelial cells.
2) Basement membrane.
3) Filtration slit.
Glomerular endothelial cells.
Leaky because they have large fenestrations. Permits all solutes in blood plasma to exit glomerular capillaries. Prevents filtration of blood cells. Mesangial cells are contractile cells that help regulate glomerular filtration, and they are in the cleft between afferent and efferent arterioles.
Basement membrane (of filtration membrane of glomerulus).
A layer of acellular material between the endothelium and podocytes consists of collagen fibres and negatively charged glycoproteins. The pores allow water and most small solutes to pass through. The negative charge of the glycoproteins repel plasma proteins, preventing their filtration.
Filtration slit.
Extending from each podocyte are thousands of pedicels that wrap around glomerular capillaries. The spaces between pedicels are filtration slits. A slit membrane extends across each filtration slit and permits the passage of molecules.
Less than 1% of which protein passes the slit membrane because it is slightly too big?
Albumin.
Why would the volume of fluid filtered by the renal corpuscle be larger than in other blood capillaries?
1) Glomerular capillaries present a large SA for filtration because they are long and extensive. While mesangial cells are relaxed, SA is maximal and glomerular filtration is very high.
2) Filtration membrane is thin and porous.
3) Glomerular capillary blood pressure is high because the efferent arterioles are smaller than the afferent arterioles.
