Chapter 25: Urinary System Flashcards
Functions of Urinary system
regualtes volume and chemical makeup of extracellular and intracellular fluids; ensures long term acid base balance; excretes metabolic (nitrogenous) wastes, drugs and toxins; produces erythropoietin (hormone regulating RBC produciton) and renin (enzyme regualting BP); converts vit D to its active form; carries out gluconeogeneiss during prolonged fasting
Location of Kidneys
superior lumbar region (between T12 and L3); retroperitenial
What are the three supportive tissues that surround the kidneys?
renal fascia; perirenal fat capulse; fibrous capsule
Renal Fascia
anchors kidneys to surround structures
Perirenal Fat Capsule
cushions the kidneys
Fibrous Capsule
prevents infections from spreading to kidneys
External Anatomy of Kidney
ureter, renal blood vessels, lymphatics and nerves enter/exit kidney at renal hilum; adrenal gland sits atop kidney
3 Regions of the Kidney
renal cortex; renal medulla and renal pelvis
Renal Cortex
outermost; has granular appearance
Renal Medulla
contains renal pyramid; has striated pyramid
Renal Pelvis
funnel shaped tube continuous with ureter
Urine drains…
continurously from each pyramid; minor calyx to major calyx to renal pelvis to ureter
ADD BLOOD SUPPLY
Blood passes thru…
TWO capillary bed
Nephrons
structural and functional units of the kidney; process blood to form urine; consists of renal corpuscle and renal tubule
Renal Corpuscle
located within renal cortex; consists of two parts glomerulus and glomerular capsule
Glomerulus
ball of fenestrated capillaries; fed by afferent arteriole; drianed by efferent arteriole; filters blood to form filtrate; capillaries are higher in pressure compared to other parts of body
Glomerular Capsule is two layered
parietal layer- simple squamous epithelium; visceral layer- consists of podocytes (branching epithelial cells with foot processes that adhere to glomerulus); filtrate passes thru filatarion slits into glomerular capsular layers (cells and lg proteins can not pass)
Renal Tubule
located in cortex and medulla; consists of 3 parts- proximal convoluted tubule, nephron loop, and distal convoluted tubule
Proximal Convoluted Tubule
PCT; continuous with glomerular capsular space; confined to cortex; wall is simple cuboidal epithelium with dense microvilli (brush border)
Nephron Loop
consists of descending and ascending limbs; extend into medulla; wall of thick segment is simple cuboidal epithelium; wall of thin segment is simple squamous
Distal Convoluted Tubule
DCT; confined to cortex; wall is thin layer of simple cuboidal epithelium with few microvilli
Collecting Ducts
not part of nephron; receive filtrate from nephrons and have 2 cell types; princuple cells- maintain water and NA balance and intercalated cells- maintain acid base balance of blood
Two Types of Nephrons Exist
Cortical nephrons and juxtamedullary nephrons
Cortical Nephrons
85%; glomerulus in outer cortex; short nephron loops; efferent arteriole empties into peritubular capillary bed
Juxtamedullary Capillary Bed
15%; glomerulus nearer cortex (medulla junction); long nephron loops; efferent arteriole empties inot vasa recta capillary bed; play major role in forming concentrated urine
Juxtaglomerular Complex
JGC; region of nephron where the afferent arteriole contacts the distal portion of the ascending limb; consists of three populations of cells- granular cells, macula densa and extraglomerular mesangial cells
Granular Cells
modified smooth muscle cells in wall of afferent arteriole; function as mechanoreceptors to monitor BP; secrete renin (enzyme)
Macula Densa
modified epithelial cells in ascending limp; function as chemoreceptors to monitor NaCl in filtrate
Extraglomerular Mesangial Cells
sandwhiched between afferent arteriole and macula densa; involved in cross talk
What three processes are involved with urine formation?
glomerular filtration; tubular reabsorption; tubular secretion
Glomerular Filtration
occurs within renal corpuscles; passive, non selective process; hydrostatic pressure forces fluids and solutes thru a filatration membrane; produces a cell and protein free filtrate
Filtrate membrane consists of three layers..
fenerstrated endothelium of glomerular capillaries; basement membrane; foot processes of podocytes of the glomerular capsule
Glomerular Mesangial Cells
remove macromolecules that clog the filtration membrane
Hydrostatic Pressure in Glomerular Capillaries
HPgc = 55 mmhg; pushes water and solutes out of glomerulus into capsular space
Hydrostatic Pressure in Capsular Space
HPcs=15 mmhg; pushes water and solutes out of capsular space in glomerulus
Osmotic Pressure in the Glomerulus
OPgc= 30 mmhg; blood proteins pull water in glomerulus
Net Filtration Pressure =
(NFP); outward pressures - inward pressures = HPgc - (HPcs + OPgc) = 55 - ((15+30)= 10 mmhg
Glomerular Filtration Rate
GFR; volume of filtrate formed per min by both kidneys; normal = 120-125 ml/min
GFR determined primarily by..
HPgc
dilation of afferent arteriole (constriction of efferent arteriole) does what to GFR
increases it
Constriction of afferent arteriole ( or dilation of efferent arteriole) does what to GFR
decreases it
What are the two types of control that regulates GFR?
intrinsic and extrinsic
Intrinsic Control
renal autoregulation; kidney adjusts its own resistance to blood flow; involves two mechanisms that directly regulate GFR- myogenic mechanism (targets smooth muscle of afferent arteriole) and tubuloglomerular feedback mechanism (directed by macula densa of cells of the JGC); regulates when mean arterial pressure is 80-180 mmhg (so in a relatively normal range)
Extrinsic Control
override intrinsic controls if mean arterial pressure is <80 or >180 mmhg; involves 2 mechanisms that indirectly regulate GFR- neural mechanism (SNS) and hormonal mechanism (renin-angiotensis-aldosterone mechanism)
Tubular Reabsorption
process of reabsorbing (actively or passively) selected materials from renal tubules and collecting ducts, returining them to the blood stream; most reabsorption occurs from PCT; reabsorption in DCT and collecting tubes is regulated by hormones
ADH
targets collecting ducts; increase h20 reabsorption
Aldosterone
targets DCT and collecting ducts; increase sodium and h20 reabsorption
Atrial Natriuretic Peptide
ANP; targets collecting ducts; decreases na and h20 absorption
PTH
targets DCT ; increase ca reabsorption
Tubular Secretion
active process of moving selected materials from the peritubular capillaries into the filtrate for elimination in urine; diposes of certain drugs; eliminates undesirable substances (urea, uric acid); rids body of excess k; controls blood pH (H and HCO3)
Osmotic Gradient
reason kidneys have the ability to generate dilute and concentrated urine; ranges from 300 (cortex) - 1200 (pelvis) milliosmoles in renal medulla
Diuretics
increases water output; given to people who tend to retain fluid (diabetics, heart failure, increased BP)
Normal Output of Urine
800-1200 ml/day
Chemical Composition of Urine
h2o (95%) and solutes (5%); nitrogenous wastes (urea, uric acid); ions (na, k, po3, so4, ca, mg, hco3)
Urinalysis
may reveal presences of abnormal substances ADD THESE
Physical Characteristics of Urine
transparent (cloudiness indicates UTI); yellow color due to eurochrome; slightly aromatic; pH ~6 (ranges from 4.5-8); specific gravity (solute concentration) 1.001-1.035
Ureters
muscular tubes transporting urine from kidneys to urinary bladder; mucosa is transitional epithelium; muscularis has additional extern longitudinal layer in lower 1/3
Urinary Bladder
collapsible, muscular sac that stores urine temporarily; 3 layers - mucosa: transitional epithelium; muscularis: internal, circular and external collectively called detrusor muscle; adventitia or serosa (depends on area); mucosa of empty bladder forms folds called rugae; ureters penetrate posterior bladder wall so that bladder pressure forces ends of ureters to close (prevents backflow)
Trigone
triangular area outlined by opening of ureters and urethra; area most infected
Urethra
muscular tube transporting urine from bladder to exterior; mucosa transitions from transitional epithelium to pseudostratified columnar to stratified squamous
Internal Urethral Sphicter
smooth muscle; located at bladder-urethra junction; controlled by ANS
External Urethral Sphincter
skeletal muscle; at urogenital diaphragm; controlled by somatic NS
Female Urethra
1.5 in long; transports urine only
Male Urethra
8 in long; transports urine and semen; subdivided into 3 regions (prostatic, membranous, penile)
Micturition
aka urination, voiding; 3 simultaneous events occur- detrusor muscle contracts, internal urethral sphincter relaxes, external urethral sphincter relaxes; controlled by pontine micturition center and pontine storage center
Micturition in Infants
stretching of bladder initaties a spinal reflex but they can not control it; between ages 2-3 brain can override reflexive urination
Pyelerphritis
kidney infection
Glomerulonephritis
inflammation of glomeruli
Cystisis
bladder infection; experience painful urination (dysuria) and in females usually caused by fecal bacteria
Urethritis
infection of urethra
Renal Calculi
kidney stones; caused when crystals form from ca, mg, or uric acid
Chronic Renal Disease
GFR less than 60 ml/min for at least 3 months; leading cuase is diabetes mellitus (44%) followed by hypertension (28%)
Auria
urinary output less than 50 ml per day (kidneys must process 400-500 per day to excrete nitrogenous wastes)
Renal Failure
GFR less than 15 ml / min; treatment- hemodialysis or transplant
