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Anatomy and Physiology > urinary system i > Flashcards

urinary system i Flashcards

1
Q

urinary system organs

A

Kidneys - major excretory organs
Ureters - transport urine from kidneys to urinary bladder
Urinary bladder - temporary storage reservoir for urine
Urethra transports urine out of body

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2
Q

Kidney Main Functions

  • water
  • endocrine
  • vitamin
  • glucose
A
  1. regulate water volume/ solute concentration
  2. regulate ECF ion concentration
  3. ensure long-term acid-base balance
  4. remove metabolic waste/toxic drugs
  5. renin to regulate BP
  6. erythropoeitin to regulate RBC production
  7. activation of vit D: calcitriol
    8 gluconeogenesis during fasting
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3
Q

Internal anatomy (cortex and medulla)

A

Renal cortex
-Granular-appearing superficial region

Renal medulla

  • -Composed of cone-shaped medullary (renal) pyramids
  • Pyramids separated by renal columns (Inward extensions of cortical tissue)
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4
Q

Papilla, lobe, and pelvis

A

Papilla
-Tip of pyramid; releases urine into minor calyx

Lobe
-Medullary pyramid and its surrounding cortical tissue; ~ 8/kidney

Renal pelvis
-Funnel-shaped tube continuous with ureter

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5
Q

calyces

A

Minor calyces
-Drain pyramids at papillae

Major calyces

  • Collect urine from minor calyces
  • Empty urine into renal pelvis
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6
Q

urine flow

A

Renal pyramid  minor calyx  major calyx  renal pelvis  ureter

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7
Q

kidney blood supply

A
  • Rich blood supply
  • arteries deliver 25% of cardiac output to kidneys each min
  • arterial flow into and venous flow out of kidneys along similar path
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8
Q

nerve supply to kidneys

A

sympathetic fibers from renal plexus

NO parasympathetic innervation

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9
Q

blood flow path

A 
aorta
renal artery
segmental artery
interlobar artery
arcuate artery
cortical radiate artery
afferent arteriole
glomerulus capillaries
efferent arteriole
peritubular capillaries or vasa recta
cortical radiate vein
arcuate vein
interlober vein 
renal vein
inferior vena cava
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10
Q

how many nephrons per kidney?

A

over a million

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11
Q

tubular parts of nephron

A 
Glomerular (Bowman’s) capsule
Proximal convoluted tubule (PCT)
Nephron loop (loop of Henle)
Descending limb →  Ascending limb
Distal convoluted tubule (DCT)
Multiple nephron tubules drain into Collecting Duct (CD)
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12
Q

blood vessel components of nephron

A 
Afferent arteriole
Glomerulus
Efferent arteriole
Peritubular capillaries
Vasa recta (if juxtamedullary nephron)
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13
Q

two parts of renal corpuscle

A

Glomerulus
-Tuft of capillaries; fenestrated endothelium  highly porous  allows filtrate formation

Glomerular capsule (Bowman's capsule)
-Cup-shaped, hollow structure surrounding glomerulus
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14
Q

glomerular capsule anatomy

A

Parietal layer - simple squamous epithelium

Visceral layer - branching epithelial podocytes

  • Extensions terminate in foot processes that cling to basement membrane
  • Filtration slits between foot processes allow filtrate to pass into capsular space
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15
Q

proximal convoluted tubule
cells
function
location

A

Cuboidal cells with dense microvilli (brush border –> high surface area); large mitochondria

Functions in reabsorption and secretion

Confined to cortex

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16
Q

nephron loop

A

Descending and ascending limbs

Proximal descending limb continuous with proximal tubule

Distal descending limb = descending thin limb; simple squamous epithelium

Thick ascending limb
-Cuboidal to columnar cells; thin in some nephrons

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17
Q

distal convoluted tubule
cell
function
location

A

Cuboidal cells with very few microvilli
Function more in secretion than reabsorption
Confined to cortex

18
Q

Collecting duct’s cells

A

Principal cells

  • Sparse, short microvilli
  • Maintain water and Na+ balance

Intercalated cells
-Cuboidal cells; abundant microvilli; two types –>A and B; both help maintain acid-base balance of blood

19
Q

collecting duct func

A

receive filtrate from many nephrons

run thru medullary pyramids –> look stripy

fuse together to get urine thru papillae into minor calyces

20
Q

2 types of nephrons

A

Cortical nephrons—85% of nephrons; almost entirely in cortex
–have peritubular capillaries

Juxtamedullary nephrons

  • Long nephron loops deeply invade medulla
  • Ascending limbs have thick and thin segments
  • Important in production of concentrated urine
  • Have vasa recta
21
Q

Nephron capillary beds (2 kinds)

A

glomerulus = all renal tubules (specialized for filtration)

Peritubular capillaries (for cortical nephrons) or vasa recta (for juxtamedullary nephrons)

22
Q

why is bp high in glomerulus

A
  • afferent arterioles larger in diameter than efferent arterioles
  • arterioles are high-resistance vessels
23
Q

peritubular capillaries

A

Low-pressure, porous capillaries adapted for absorption of water and solutes

Arise from efferent arterioles

Cling to adjacent renal tubules in cortex

Empty into venules

24
Q

vasa recta

A

Long, thin-walled vessels parallel to long nephron loops of juxtamedullary nephrons

Arise from efferent arterioles serving juxtamedullary nephrons
-Instead of peritubular capillaries

Function in formation of concentrated urine

25
Q

Juxtaglomerular complex

A

-one per nephron

Involves modified portions of

  • distal portion of ascending limb of nephron loop (some references say it involves the first part of the distal convoluted tubule)
  • afferent arteriole

Important in regulation of rate of filtrate formation and BP

includes macula densa cells, granular cells, and extraglomerular mesangial cells

26
Q

macula densa cells

A

Tall, closely packed cells of ascending limb (or first part of DCT)

Chemoreceptors; sense NaCl content of filtrate

27
Q

granular cells

A

Enlarged, smooth muscle cells of arteriole

Secretory granules contain enzyme renin (so now we do not just say renin comes from the kidney! We know exactly where it comes from.)

Mechanoreceptors; sense blood pressure in afferent arteriole

28
Q

extraglomerular mesangial cells

A

Between arteriole and tubule cells
Interconnected with gap junctions
May pass signals between macula densa and granular cells

29
Q

how much urine is produced per day vs the amount of fluid processed?

What are the 3 processes of urine formation

A

180 L processed/day –> 1.5 L urine/day

  1. glomerular filtration
  2. tubular reabsorption
  3. tubular secretion
30
Q

definitions of the 3 processes

A

glomerular filtration = produces cell-and protein- free filtrate

Tubular reabsorption = selectively returns 99% of substances from filtrate to blood in renal tubules and collecting ducts

Tubular secretion = selectively moves substances from blood to filtrate in renal tubules and collecting ducts

31
Q
  • how many times a day do the kidneys filter the body’s plasma volume?
  • how much of the body’s oxygen do the kidney’s use at rest?
  • from what is the urine produced?
A

60 times

20-25%

From filtrate (from glomerular filtration) = blood plasma minus proteins

Urine = <1% of oringinal filtrate –> contains metabolic wates and inneeded substances

32
Q

energy requirements of glomerular filtration

A
  • passive
  • no metabolic energy required
  • hydrostatic pressure forces fluids and solutes thru filtration membrane
  • no reabsorption into capillaries of glomerulus
33
Q

Filtration membrane

definition and layers

A

Porous membrane between blood and interior of glomerular capsule
-Water, solutes smaller than plasma proteins pass; normally no cells pass

  1. Fenestrated endothelium of glomerular capillaries
  2. Basement membrane (fused basal laminae of two other layers)
  3. Foot processes of podocytes with filtration slits; slit diaphragms repel macromolecules
34
Q

Filtration membrane: what can pass and what can’t

A

Macromolecules “stuck” in filtration membrane engulfed by glomerular mesangial cells

Allows molecules smaller than 3 nm to pass
(Water, glucose, amino acids, nitrogenous wastes)

Plasma proteins remain in blood  maintains colloid osmotic pressure  prevents loss of all water to capsular space

Proteins in filtrate indicate a filtration membrane problem. Protein in urine is abnormal!

35
Q

pressures that affect filtration

A

Outward:
hydrotatic pressure in glomerular capillaries = glomerular bp
-chief force pushig water and solutes out of blood
-high (55 mm Hg) –> most capillary beds = 26 mm Hg

Inward:
Hydrostatic pressure in capsular space
-pressure of filtrate in capsule (15 mm Hg)
Colloid osmotic pressure in capillaries
-"pull" of proteins in blood (30 mm Hg)

Sum:
Net filtration pressure
-outward force of 10 mm Hg
-resposible for filtrate formation and glomerular filtration rate

36
Q

Glomerular filtration rate

A

Volume of filtrate formed per minute by both kidneys (normal = 120–125 ml/min)

GFR directly proportional to

  • NFP – primary pressure is hydrostatic pressure in glomerulus
  • Total surface area available for filtration – glomerular mesangial cells control by contracting
  • Filtration membrane permeability – much more permeable than other capillaries
37
Q

regulation of glomerular filtration: intrinsic

A

Intrinsic controls (renal autoregulation)

  • act locally within kidney to maintain GFR
  • if glomerular hydrostatic pressure falls by only 18%, GFR = 0
  • maintains constant GFR w/in MAP of 80-180
  • 2 methods: myogenic mechanism and tubuloglomerular feedback mechanism
38
Q

Myogenic Mechanism

A

smooth muscle contracts when stretched

high BP = smooth muscle stretch –> constriction of afferent arterioles = restricted blood flow into glomerulus (protects from damage)

low bp –> dilation of afferent arterioles

39
Q

Tubuloglomerular Feedback Mechanism

A

Flow dependent mechanism directed by macula densa cells –> respond to filtrate NaCl concentration

If GFR is high –> filtration flow rate is high –> there’s a shorter reabsorption time –> there’s high filtrate NaCl levels –> there’s constriction of afferent arteriole –> decreases NFP and GFR –> more time for NaCl reabsorption

opposite for low GFR

40
Q

Extrinsic controls of glomerular filtration

A

Extrinsic controls maintain systemic blood pressure

  • sympathetic NS and Renin-Angiotensin-Aldosterone mechanism –> can negatively affect kidney func
  • takes precedence over intrinsic controls if systemic BP <80 or >180 mm Hg
41
Q

Extrinsic controls: sympathetic NS

A

If extracellular fluid volume extremely low (bp is low)

  • NE released by SNS and Epitnephrine released by adrenal medulla
  • systemic vasoconstriction and higher bp
  • constriction of afferent arterioles –> lower GFR –> increased blood volume and pressure
42
Q

Extrinsic Controls: Renin-Angiotensin- Aldosterone Mechanism

A

Main mechanism for increasing blood pressure –Three pathways to renin release by granular cells

  1. Direct stimulation of granular cells by sympathetic nervous system
  2. Stimulation by activated macula densa cells when filtrate NaCl concentration low
  3. Reduced stretch of granular cells in afferent arteriole

Anatomy and Physiology (50 decks)

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