Chapter 26 Flashcards
Urinary system
Consists of two kidneys, two ureters, one urinary bladder, and one urethra.
What is the order of urine flowing through the urinary system?
Kidneys (filter blood of wastes and excrete them into urine) -> ureters -> urinary bladder -> urethra
What are the eight functions of the kidneys?
- Excretion of wastes.
- Regulation of blood ionic composition.
- Regulation of blood pH.
- Regulation of blood volume.
- Regulation of blood pressure.
- Maintenance of blood osmolarity.
- Production of hormones.
- Regulation of blood glucose level.
Nitrogenous wastes
What urea, ammonia, creatinine, uric acid, and urobilin are collectively known as. All contain nitrogen, hence the name nitrogenous wastes.
Describe the location, description, and function of the kidneys
True or false: the kidneys are said to be retroperitoneal.
True
Renal hilum
Indentation through which the ureter emerges from the kidneys, along with blood vessels, lymphatic vessels, and nerves.
What are the three layers that surround each kidney? Describe them:
- Renal capsule: deep layer; is a smooth, transparent sheet of dense irregular connective tissue that is continuous with the outer coat of the ureter. Serves as a barrier against trauma and helps maintain the shape of the kidneys.
- Adipose capsule: middle layer; is a mass of fatty tissue surrounding the renal capsule. Protects the kidneys from trauma and holds it firmly in place within the abdominal cavity.
- Renal fascia: superficial layer; is a thin layer of dense irregular connective tissue that anchors the kidney to the surrounding structures and to the abdominal wall.
What are the two distinct regions of the kidneys? Describe them:
- Renal cortex: superficial, light red region of the kidneys.
- Renal medulla: deep, darker reddish-brown inner region of the kidneys.
Renal pyramids
Found within the renal medulla.
Renal papilla
Narrower end of renal pyramids. Point towards the renal hilum.
What two zones can the renal cortex be divided into?
- Cortical zone (outer)
- Juxtamedullary zone (inner)
Renal columns
What the cortical zone and juxtamedullary zone are collectively referred to as.
Parenchyma
What the renal cortex and renal pyramids of the renal medulla are collectively referred to as.
Nephrons
Functional units of the kidneys. Found in the parenchyma.
What is the path of urine drainage?
Collecting duct -> papillary duct -> minor calyx -> major calyx -> renal pelvis -> ureter -> urinary bladder
Renal sinus
Cavity within the kidney that contains part of the renal pelvis, the calyces, and branches of the renal blood vessels and nerves. Adipose tissue helps stabilize the position of these structures in the renal sinus.
What is the path of blood in the kidneys?
Renal artery -> segmental arteries -> interlobar arteries -> arcuate arteries -> cortical radiate arteries -> afferent arterioles -> glomerular capillaries -> efferent arterioles -> peritubular venules -> cortical radiate veins -> arcuate veins -> interlobar veins -> renal vein
Vasa recta
Long, loop-shaped capillaries that extend from some efferent arterioles. Supply tubular portions of the nephron in the renal medulla.
Renal nerves
Many of them originate in the renal ganglion and pass through the renal plexus into the kidneys along with the renal arteries. Renal nerves are part of the sympathetic division of the
autonomic nervous system. Most are vasomotor nerves that regulate the flow of blood through the kidney by causing vasodilation or vasoconstriction of renal arterioles.
Renal corpuscle
Part of a nephron where blood plasma is filtered.
What are the two components of a renal corpuscle? Describe them:
- Glomerulus: capillary network
- Glomerular capsule (Bowman’s capsule): a double-walled epithelial cup that surrounds the glomerular capillaries. Filters blood plasma before passing into the renal tubule.
What are the three components of the renal tubule?
- Proximal convoluted tubule (PCT)
- Nephron loop (loop of Henle)
- Distal convoluted tubule (DCT)
Collecting duct (CD)
What distal convoluted tubules (DCT) empty into. Collecting ducts then unite and converge into several hundred large papillary ducts, which drain into the minor calyces.
What is the difference between the descending limb of the nephron loop and the ascending limb of the nephron loop?
Descending limb of the nephron loop: the first part of the nephron loop that begins at the point where the proximal convoluted tubule takes its final turn downward. It begins in the renal cortex and extends downward into the renal medulla.
Ascending limb of the nephron loop: the second part of the nephron loop when it makes the hairpin turn and returns to the renal cortex where it terminates at the distal convoluted tubule.
What is the difference between cortical nephrons and juxtamedullary nephrons? (Image of both on pg. 928-929)
Cortical nephrons: 80-85% of nephrons; their renal corpuscles lie in the outer portion of the renal cortex, and they have short nephron loops that lie mainly in the cortex and penetrate only into the outer region of the renal medulla. The short 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 cortex, close to the medulla, and they have a long nephron loop that extends into the deepest region of the medulla. Long nephron loops receive their blood supply from peritubular capillaries and from the vasa recta that arise from efferent arterioles.
What two portions does the ascending limb of the nephron loop of juxtamedullary nephrons consist of?
- Thin ascending limb
- Thick ascending limb
Glomerular capsule (Bowman’s capsule)
Consists of visceral and parietal layers.
Podocytes
Modified simple squamous epithelial cells found in the visceral layer of the glomerular capsule. Form the inner wall of the capsule.
Capsular space
The space between the two layers of the glomerular capsule, which is continuous with the lumen of the renal tubule.
What type of cell(s) make up the proximal convoluted tubule (PCT)?
Simple cuboidal epithelial cells with prominent brush borders of microvilli.
What type of cell(s) make up the nephron loop: descending limb and thin ascending limb?
Simple squamous epithelial cells.
What type of cell(s) make up the nephron loop: thick ascending limb?
Simple cuboidal to low columnar epithelial cells.
What type of cell(s) make up most of the distal convoluted tubule (DCT)?
Simple cuboidal epithelial cells.
What type of cell(s) make up the last part of the distal convoluted tubule (DCT) and all of the collecting duct (CD)?
Simple cuboidal epithelium consisting of principal cells and intercalated cells.
Macula densa
What columnar tubule cells in the final part of the ascending limb of the nephron loop are known as. They make contact with the afferent arteriole serving the renal corpuscle.
Juxtaglomerular (JG) cells
Modified smooth muscle fibers found in the walls of afferent (and sometimes efferent) arterioles.
Juxtaglomerular apparatus (JGA)
What the juxtaglomerular (JG) cells and the macula densa are collectively referred to as. The JGA helps regulate blood pressure within the kidneys.
Principal cells
Found in the last part of the distal convoluted tubule (DCT) and in the collecting duct (CD). Large amount of them. Have receptors for antidiuretic hormone (ADH) and aldosterone.
Intercalated cells
Found in the last part of the distal convoluted tubule (DCT) and in the collecting duct (CD). Small amount of them. Play a role in the homeostasis of blood pH.
What three basic processes do nephrons and collecting ducts perform to produce urine?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion (removes a substance from the blood)
Glomerular filtrate
The fluid that enters the capsular space.
Filtration fraction
The fraction of blood plasma in the afferent arterioles of the kidneys that becomes glomerular filtrate.
Filtration (endothelial–capsular) membrane
Leaky barrier formed by glomerular capillaries and podocytes. Permits filtration of water and small solutes but prevents filtration of most plasma proteins and blood cells.
What are the three filtration barriers of the filtration (endothelial–capsular) membrane? Describe them:
- A glomerular endothelial cell: contain fenestrations (pores) and mesangial cells (contractile cells that help regular glomerular filtration)
- Basement membrane
- Filtration slit formed by a podocyte: contain pedicels (footlike processes extending from podocytes that wrap around glomerular capillaries), filtration slits (spaces between pedicels), and slit membranes (thin membranes that extends across each filtration slit)
What are the three reasons that the volume of fluid filtered by the renal corpuscle is much larger than in other blood capillaries?
- Glomerular capillaries present a large surface area for filtration because they are long and extensive. Mesangial cells regulate how much surface area is available. When mesangial cells are relaxed, surface area is maximal, and glomerular filtration is very high. Contraction of mesangial cells reduces the available surface area, and
glomerular filtration decreases. - The filtration membrane is thin and porous. Despite having several layers, the thickness of the filtration membrane is only 0.1 mm. Glomerular capillaries also are about 50 times leakier than blood capillaries in most other tissues, mainly because of their large fenestrations.
- Glomerular capillary blood pressure is high. Because the efferent arteriole is smaller in diameter than the afferent arteriole, resistance to the outflow of blood from the glomerulus is high. As a result, blood pressure in glomerular capillaries is considerably higher than in blood capillaries elsewhere in the body.
Glomerular filtration depends on three main pressures. One pressure promotes filtration and two pressures oppose filtration. What are these three main pressures? Describe them:
- Glomerullar blood hydrostatic pressure (GBHP): the blood pressure in glomerular capillaries. Generally, GBHP is about 55 mmHg. Promotes filtration by forcing water and solutes in blood plasma through the filtration membrane.
- Capsular hydrostatic pressure (CHP): the hydrostatic pressure exerted against the filtration membrane by fluid already in the capsular space and renal tubule. CHP opposes filtration and represents a “back pressure” of about 15 mmHg.
- Blood colloid osmotic pressure (BCOP): is due to the presence of proteins such as albumin, globulins, and fibrinogen in blood plasma, also opposes filtration. Average BCOP in glomerular capillaries is 30 mmHg.