CHAPTER 25 A&P
Peritubular capillaries arise from
Efferent arterioles, cling to adjacent renal tubules in cortex, and empty into venules
Minor calyx
-Branch of major calyx -Collects urine from pyramid
Renin-angiotensin mechanism
-Granular cells release renin -Renin acts on angiotensinogen to form angiotensin I -Angiotensin I is converted to angiotensin II -Angiotensin II causes mean arterial pressure to rise and simulates the adrenal cortex to release aldosterone -Systemic and glomerular blood pressure rise
Net filtration pressure
-Pressure responsible for filtrate formation -Main controllable factor determining glomerular filtration rate (GFR). -NFP= HPg-(OPg+HPc)= 10 mm Hg
Three layers of bladder wall
-Transitional epithelial mucosa -Detrusor muscle -Fibrous adventitia
Three parts of renal tubule
1. Proximal convoluted tubule (closest to renal corpuscle) 2. Nephron loop 3. Distal convoluted tubule (farthest from renal corpuscle)
Renal arteries deliver
1/4 (1200 ml) of cardiac output to the kidneys each minute
Lobe
A medullary pyramid and its surrounding cortical tissue
Nephron capillary beds: Glomerulus
Afferent arteriole to glomerulus to efferent arteriole. -Specialized for filtration
Dilute urine is created by
Allowing this filtrate to continue into the renal pelvis
Filtration membrane
Allows passage of water and solutes smaller than most plasma proteins
Kidneys regulate
Blood volume (water balance), salts, the acid/base balance and pH
Granular cells (juxtaglomerular or JG cells)
Enlarged, smooth muscle cells of arteriole -Secretory granules contain enzyme renin -Mechanoreceptors sense blood pressure in afferent arteriole
Macula densa
Tall, closely packed cells, chemoreceptors that sense NaCl content of filtrate
Urinary bladder
Temporary storage reservoir for urine
JGA involves modified portions of the
Distal portion of the distal convoluted tubule and afferent (sometimes efferent) arteriole
Glomerulus blood pressure is high because
Efferent arterioles are smaller in diameter than afferent arterioles, and arterioles are high-resistance vessels (55 mmHg)
Vasa recta arise from
Efferent arterioles of juxtamedullary nephrons instead of peritubular capillaries
Filtrate is diluted in the
Ascending loop of Henle
Extraglomerular mesangial cells
Between arteriole and tubule cells, interconnected with gap junctions -May pass signals between macula dense and granular cells
Proximal convoluted tubule (PCT)
Composed of cuboidal cells with numerous microvilli, reabsorbs water and solutes from filtrate and secretes substances into it
Renal medulla
Cone shaped medullary (renal) pyramids separated by the renal columns
85% of nephrons are ______
Cortical nephrons, located in the cortex
Distal convoluted tubule (DCT)
Cuboidal cells without microvilli that function more in secretion than reabsorption
Glomerular capsule (Bowman's capsule)
Cup-shaped, hollow structure surrounding glomerulus
Podocytes
Extensions terminate in foot processes that cling to basement membrane. Filtration slits between foot processes allow filtrate to pass into capsular space
Renal capsule
Fibrous connective tissue
Fenestrations of filtration membrane prevent
Filtration of blood cells
Urine formation involves _____
Glomerular filtration, tubular reabsorption, secretion
List and describe three pressures operating at the filtration membrane, and explain how each influences net filtration pressure
Glomerular hydrostatic pressure is the chief force pushing water and solutes across the filtration membrane. The higher the glomerular hydrostatic pressure, the more filtrate is pushed across the membrane. Colloid osmotic pressure of plasma proteins in the glomerular blood, and capsular hydrostatic pressure exerted by fluids in the glomerular capsule, drive fluids back into the glomerular capillaries. The net filtration pressure equals glomerular hydrostatic pressure minus the sum of colloid osmotic pressure of glomerular blood and capsular hydrostatic pressure.
A renal corpuscle includes the ______
Glomerulus and glomerular (Bowman's) capsule
Kidney function in prolonged fasting
Gluconeogenesis
Descending limb of nephron loop reabsorbs
H2O
Ureters, renal blood vessels, lymphatics, and nerves enter and exit at the _____
Hilus
Juxtaglomerular apparatus (JGA)
Important in regulation of filtrate formation and blood pressure
Blood vessels of the renal columns are called ____
Interlobar
Juxtamedullary nephrons
Involved in the production of concentrated urine
The right kidney is lower than the left because
It is crowded by the liver
Negatively charged basement membrane repels
Large anions such as plasma proteins
Vasa recta
Long vessels parallel to long loops of Henle that function in formation of concentrated urine
Peritubular capillaries
Low pressure, porous capillaries adapted for absorption of water and solutes
Slit diaphragms also help to propel
Macromolecules
Juxtaglomerular complex (JGC) three cell populations
Macula densa, granular cells, extraglomerular mesangial cells
The kidneys are the
Major excretory organs
Urine has ____
Metabolic waste such as urea and uric acid
Ascending limb of nephron loop reabsorbs
Na+, K+, Cl-
The functional unit of the kidney is called a ____
Nephron
The sequence from the formation of a drop of urine to its elimination from the body:
Nephron, collecting duct, minor calyx, major calyx, renal pelvis, ureter, urinary bladder, urethra
Glomerular capsule structure
Parietal layer: simple squamous epithelium Visceral layer: branching epithelial podocytes
Urine passes through the ____
Pelvis of the kidney to ureter to bladder to urethra
Urochrome
Pigment from hemoglobin breakdown, gives urine color
Glomerular filtrate is least likely to contain _____
Plasma proteins
Endocrine function of the kidneys
Produce erythropoietin for the regulation of RBC production
Glomerular filtration
Produces cell- and protein-free filtrate by a passive process in which hydrostatic pressure forces (blood pressure) forces fluids and solutes through a membrane
Urine crystals in the renal pelvis are called
Renal calculi
Two main parts of nephrons
Renal corpuscle and renal tubule
Urine flow:
Renal pyramid to minor calyx to major calyx to renal pelvis to ureter
The kidneys lie in a ______ position in the ______
Retroperitoneal; superior lumbar region
If a substance is transported from the plasma of the peritubular capillary into the fluid of the renal tubule, it is said to be
Secreted
As the renal artery approaches the kidney, it branches to supply the renal tissue. The correct sequence starting from the renal artery:
Segmental, interlobar, arcuate, cortical radiate
Tubular secretion
Selectively moves substances from blood to filtrate in renal tubules and collecting ducts
Tubular reabsorption
Selectively returns 99% of substances from filtrate to blood in renal tubules and collecting ducts
Urine pH
Slightly acidic (4.5-8.0)
Substances reabsorbed in PCT
Sodium, all nutrients, cations, anions, water, urea and lipid-soluble solutes, small proteins
Renal cortex
Superficial region
Major calyx
The branching channels of the renal pelvis that collect urine from minor calyces and empty urine into the renal pelvis
Renal pelvis
The funnel-shaped tube within the renal sinus
Explain how filtration works in the glomerular capillaries
The glomerular capillaries are fenestrated, allowing fairly large molecules to pass through. The substances must pass through the basement membrane, where they are further selected for size by the filtration slits of the podocytes.
Papilla
Tip of a pyramid, releases urine into minor calyx
Glomerular filtration rate
Total amount of filtrate formed per minute by the kidneys (normal 120-125 ml/min)
Kidneys remove
Toxins, metabolic wastes, and excess ions from the blood
The area between the ureters and urethra is called the ____ in a bladder
Trigone
Glomerulus
Tuft of capillaries; fenestrated endothelium, highly porous, allows filtrate formation
Most important non reabsorbed substances
Urea, creatinine, uric acid
Kidneys activate
Vitamin D
