A&P 25: The Urinary System Flashcards
Urinary System
system including the kidneys, ureters, urinary bladder, and urethra
Renal hilum
vertical cleft in the medial surface of the kidney
Renal fascia
outer layer of dense fibrous connective tissue that anchors the kidney and the adrenal gland to surrounding structures
Perirenal fat capsule
fatty mass that surrounds the kidney and cushions it against blows
Fibrous capsule
transparent capsule that prevents infections in surrounding regions from spreading to the kidney
Renal cortex
most superficial region of the kidney; light-colored, granular appearance
Renal medulla
deep to the cortex of the kidney; dark, reddish-brown; exhibits cone-shaped tissue masses
Medullary/renal pyramids
cone-shaped tissue masses in the renal medulla
Renal columns
inward extensions of cortical tissue separating the medullary/renal pyramids
Lobes
each pyramid and its surrounding cortical tissue constitutes 1 of 8 of these sections of the kidney
Renal pelvis
funnel-shaped tube continuous with the ureter leaving the hilum
Major calyces
branching extensions of the pelvis form 2 or 3 of these
Minor calyces
each major calyces subdivides to form several of these cup-shaped areas that enclose the papillae
Renal arteries
large arteries of the kidney; deliver 1/4 of the total cardiac output to the kidneys each minute
Segmental arteries
as each renal artery approaches a kidney, it divides into 5 of these arteries
Interlobar arteries
within the renal sinus, each segmental artery branches further for form several of these arteries
Arcuate arteries
at the cortex-medulla junction, the interlobar arteries branch into these arteriers that arch over the bases of the medullary pyramids
Cortical radiate arteries
AKA interlobular arteries; small arteries that radiate outward from the arcuate arteries to supply the cortical tissue
Cortical radiate, arcuate, interlobar, renal veins
veins that trace the pathway of the arterial supply in reverse (except there are no segmental veins)
Renal plexus
variable network of autonomic nerve fibers and ganglia; provides the nerve supply of the kidney and its ureter; offshoot of the celiac plexus
Nephrons
structural and functional units of the kidneys; each kidney contains over 1 million of these tiny blood-processing units, which carry out the processes the form urine
Renal corpuscle
each of these structures consist of a tuft of capillaries (glomerulus)
Glomerulus
tuft of capillaries; “ball of yarn”
Glomerular capsule
cup-shaped hollow structure that makes up the renal corpuscle along with the glomerulus; AKA Bowman’s capsule
Filtrate
plasma-derived fluid; raw material that the renal tubules process to form urine
Podocytes
“foot cells”; highly modified, branching epithelial cells that make up the visceral layer of glomerular capsule
Foot processes
octopus-like podocytes terminate in these, which interdigitate as they cling to the basement membrane of the glomerulus
Filtration slits
the clefts/openings between the foot processes
Capsular space
filtrate enters this space through the filtration slits inside the glomerular capsule
Renal tubule
3cm (1.2 in) long; 3 major parts; leaves the glomerular capsule at the proximal convoluted tubule, drops into the nephron loop, then winds/twists again as the distal convoluted tubule before emptying into a collecting duct
Proximal convoluted tubule
walls of this tube are formed by cuboidal epithelial cells with large mitochondria; apical (luminal) surfaces bear dense microvilli
Nephron loop
U-shaped loom (formerly called the loop of Henle)
Descending nephron limb
descending loop of Henle
Ascending nephron limb
ascending loop of Henle
Distal convoluted tubule
walls of this tubule are cuboidal; thinner; almost entirely lack microvilli
Collecting duct
2 cell types in this duct - principal cells (with sparse, short microvilli; responsible for maintaining they body’s water and Na+ balance) & intercalated cells (cuboidal cells with abundant microvilli; 2 types, A & B; maintain acid-base balance of the blood)
Cortical nephrons
85% of the nephrons in the kidneys
Juxtamedullary nephrons
originate close to the cortex-medulla junction; play an important role in the kidneys’ ability to produce concentrated urine
Afferent/efferent arteriole
arterioles that feed/drain the glomerulus
Peritubular capillaries
capillaries that cling closely to adjacent renal tubules and empty into nearby venules; arise from the high-resistance efferent arterioles so only experience low pressure; readily absorb solutes and water from the tubule cells as these substances are reclaimed from the filtrate
Vasa recta
bundles of long straight vessels formed from efferent arterioles serving the juxtamedullary nephrons
Juxtaglomerular complex (JGC)
each nephronhas this region where the most distal portion of the ascending limb of the nephron loop lies against the afferent arteriole feeding the glomerulus
Macula densa
group of tall, closely packed cells in the ascending limb of the nephron loop that lies adjacent to the granular cells
Granular cells
AKA juxtaclomerular (JG) cells; in the arteriolar walls; = enlarged smooth muscle cells with prominent secretory granules containing the enzyme renin; act as mechanoreceptors that sense the BP in the afferent arteriole
Urine
fluid containing unneeded substances such as excess salts and metabolic wastes
Glomerular filatration
passive process in which hydrostatic pressure forces fluids and solutes through a membrane
Filtration membrane
porous membrane lying between the blood and the interior of the glomerular capsule; allows free passage of water and solutes smaller than plasma proteins
Hydrostatic pressure in glomerular capillaries (HPgc)
glomerular blood pressure; chief force pushing water and solutes out of the blood and across the filtration membrane
Hydrostatic pressure in the capsule space (HPcs)
pressure exerted by filtrate in the glomerular capsule; much higher than hydrostatic pressure surrounding most capillaries because filtrate is confined in a small space with a narrow outlet
Colloid Osmotic pressure in glomerular capillaries (OPgc)
pressure exerted by proteins in the blood
Net filtration pressure (NFP)
HPgc, HPcs, and OPgc determine this pressure; largely determines glomerular filtration rate
Glomerular filtration rate (GFR)
volume of filtrate formed each minute by the combined activity of all 2 million glomeruli of the kidneys
Renal autoregulation
the kidneys adjusting its own resistance to blood flow; how the kidneys can maintain a nearly constant GFR despite fluctuations in systemic arterial BP
Myogenic mechanism
reflects a property of vascular smooth muscle (contracts when stretched and relaxes when not stretched)
Tubuloglomerular feedback mechanism
autoregulation by this flow-dependent mechanism is directed by the macula densa cells of the juxtaglomerular complex
Renin-angiotensin-aldosterone mechanism
body’s main mechanism for increasing BP
Renin
low BP causes the granular cells of the juxtaglomerular complex to release this enzyme by one+ pathways
Tubular reabsorption
reclaims most of the tubule contents and returns them to the blood; selective transepithelial process that begins as soon as the filtrate enters the proximal tubules
Active tubular reabsorption
process requiring ATP either directly (primary active transport) or indirectly (secondary active transport)
Passive tubular reasborption
diffusion, facilitated diffusion, and osmosis (substances moving down electrochemical gradients)
Aquaporins
transmembrane proteins that aid the passive tubular reabsorption of water by acting as water channels across cell membranes
Obligatory water reabsorption
water flow that obliges the body to absorb water in the proximal nephron regardless of its state of over- or underhydration
Facultatiive water reabsorption
water reabsorption that depends on ADH
Transport maximum (Tm)
max for substances that are reabsorbed using a transport protein in the membrane; reflects the number of transport proteins in the renal tubules available to ferry a particular substance (in mg/min)
Tubular secretion
reabsorption in reverse; way to clear plasma of unwanted substances is not to reabsorb them from the filtrate; moves selected substances (H+, K+, NH4+, creatinine, and certain organic acids/bases) from the peritubular capillaries through the tubule cells into the filtrate
Countercurrent multiplier
interaction between the flow of filtrate through the ascending and descending limbs of the long nephron loops of juxtamedullary nephrons
Countercurrent exchanger
flow of blood through the ascending and descending portions of the vasa recta
Medullary osmotic gradient
osmotic gradient that allows the kidneys to vary urine concentration dramatically
Diuretics
chemicals that enhance urinary output
Renal clearance
volume of plasma from which the kidneys clear (completely remove) a particular substance in a given time, usually 1 minute; C=UV/P where U is the concentration of the substance in the urine (mg/mL), V = flow rate of urine formation (mL/min) and P = concentration of the substance in the plasma (mg/mL)
Chronic renal disease
GFR less than 60mL/min for at least 3 months
Renal failure
GFR less than 15mL/min; filtrate formation decreases or stops completely
Uremia
clinical syndrome associated with renal failure; “urine in the blood”; includes fatigue, anorexia, nausea, mental changes, and muscle cramps
Hemodialysis
procedure using an artificial kidney apparatus, passing the patient’s blood through a membrane tubing that is permeable only to selected substances; the tubing is immersed in a solution that differs slightly from normal cleansed plasma; retains/adds needed substances, removes wastes, excess ions
Urochrome
yellow color of urine is due to this pigment that results when they body destroys hemoglobin
Specific gravity
ratio of the mass of a substance to the mass of an equal volume of distilled water
Urea
largest component of urine by weight, apart from water; derived from the normal breakdown of amino acids
Nitrogenous wastes
metabolic wastes
Uric acid
end product of nucleic acid metabolism
Creatinine
metabolite of creatine phosphate, which is found in large amounts in skeletal muscle tissue where it stores energy to regenerate ATP
Ureters
slender tubes that convey urine from the kidneys to the bladder
Renal calculi
kidney stones
Urinary bladder
smooth, collapsible, muscular sac that stores urine temporarily
Trigone
smooth, triangular region of the bladder base outlined by the openings of the ureters and the urethra; infections tend to persist in this region
Detrusor
muscular layer of the bladder; consists of intermingled smooth muscle fibers in inner and outer longitudinal layers and a middle circular layer
Urethra
thin-walled muscular tube that drains urine away from the bladder and conveys it out of the body
Internal urethral sphincter
at the bladder-urethra junction, the detrusor smooth muscle thickens to form this involuntary sphincter
External urethral sphincter
voluntary sphincter surrounding the urethra as it passes through the urogenital diaphragm
External urethral orifice
external opening of the urethra
Prostatic urethra
in males, the portion of the urethra running within the prostate
Intermediate part of the urethra
AKA membranous urethra; runs through the urogenital diaphragm; extends about 2cm from the prostate to the beginning of the penis
Spongy urethra
15cm long; passes through the penis and opens at its tip via the external urethral orifice
Micturition
urination; voiding; act of emptying the bladder
Incontinence
after the toddler years, this is usually a result of weakened pelvic muscles following childbirth or surgery, physical pressure during pregnancy, or nervous system problems
Urinary retention
condition in which the bladder is unable to expel its contained urine; common after general anesthesia
Catheter
slender drainage tube inserted into the urethra to drain urine and prevent bladder trauma from excessive stretching
Pronephros
1st tubule system that forms during the 4th week of development
Pronephric duct
connects the pronephros (gone by the 6th week) to the cloaca; persists and is used by the later-developing kidneys
Mesonephros
2nd renal system; claims the pronephric duct; comes to be called the mesonephric duct
Metanephros
when the mesonephric kidneys degenerate, this 3rd set makes its appearance
Ureteric buds
hollow structures that push superiorly from the mesonephric duct into the urogenital ridge
Ureteric ducts
the distal ends of the ureteric buds form the renal pelves, calyces, and collecting ducts & their unexpanded proximal parts, now called this, become the ureters
Urogenital sinus
as the metanephros is developing, the cloaca subdivides to form the future rectum and anal canal & this, into which the urinary and genital ducts empty
