Ion and Water Balance 4: Mammalian Kidneys Flashcards
1
Q
what are vertebrate kidneys’ roles in homeostasis (6)
A
- ion balance
- osmotic balance
- blood pressure
- pH balance
- excretion of metabolic wastes and toxins
- hormone production
2
Q
kidney structure: layers (2)
A
- outer cortex: renal cortex
- inner medulla: renal medulla
3
Q
how would liquids move through the kidney (5)
A
- renal cortex and renal medulla through the renal pyramid
- renal papilla
- minor calyx
- major calyx
- renal pelvis
4
Q
how does urine leave the kidneys (3)
A
- exits via the ureter
- empties into the urinary bladder
- urine leaves urinary bladder through the urethra
5
Q
nephron (2)
A
- functional unit of the kidney
- millions contained in a mammalian kidney
6
Q
nephron general composition (2)
A
- renal tubule
- vasculature
7
Q
nephron: renal tubule (2)
A
- lined with transport epithelium
- various segments with specific transport functions
8
Q
nephron: vasculature (2)
A
- glomerulus
- capillary beds surrounding renal tubule for blood supply
9
Q
glomerulus
A
- ball of capillaries where filtrate/urine is produced
10
Q
what is the glomerulus surrounded by
A
- Bowman’s capsule
11
Q
how do fluids travel through the nephron (6)
A
- glomerulus
- Bowman’s capsule
- proximal tubule
- loop of Henle
- distal tubule
- collecting duct
12
Q
what four processes are involved in urine production (4)
A
- filtration
- reabsorption
- secretion
- excretion
13
Q
urine production: filtration
A
- filtrate of blood formed at glomerulus
14
Q
urine production: reabsorption
A
- specific molecules in filtrate removed (water, ions, etc)
15
Q
urine production: secretion
A
- specific molecules added to the filtrate (toxins, etc)
16
Q
urine production: excretion
A
- urine is excreted from the body
17
Q
urine production: where does filtration occur
A
- from the glomerulus to the Bowman’s capsule
18
Q
urine production: where does reabsorption occur (5)
A
- proximal tubule
- descending loop of Henle
- ascending loop of Henle
- distal tubule
- collecting duct
19
Q
urine production: where does secretion occur (3)
A
- proximal tubule
- distal tubule
- collecting duct
20
Q
urine production: where does secretion occur
A
- from the end of the collecting duct into the external environment
21
Q
what components of the blood are filtered into the Bowman’s capsule (2)
A
- water
- small solutes
22
Q
what components of the blood are not filtered into the Bowman’s capsule (2)
A
- blood cells
- large macromolecules
23
Q
glomerular capillary structures/features (3)
A
- capillaries are leaky
- podocytes with foot processes form filtration structure
- mesangial cells pack between the capillaries
24
Q
podocytes with foot processes
A
- provide framework to support the capillaries during filtration
25
mesangial cells
- control blood pressure and filtration within glomerulus
26
mesangial cell constriction
- decrease filtrate production
27
mesangial cell dilation
- increase filtrate production
28
what is the glomerular filtration rate affected by
- blood pressure
29
what affects the blood pressure in the glomerulus (3)
- glomerular capillary **hydrostatic pressure**
- Bowman's capsule **hydrostatic pressure**
- **oncotic pressure**
30
oncotic pressure
- osmotic pressure due to protein concentration
31
direction of pressure in glomerulus: glomerular hydrostatic pressure
- toward the Bowman's capsule lumen
32
direction of pressure in glomerulus: Bowman's hydrostatic pressure
- toward the glomerulus
33
direction of pressure in glomerulus: oncotic pressure
- toward the glomerulus
34
primary urine
- initial filtrate filtered in Bowman's capsule that is isoosmotic to the blood
35
reabsorption: primary urine
- most water and salt in primary urine reabsorbed using transport proteins and energy
36
rate of reabsorption limit
- limited by number of transporters
37
renal threshold
- concentration of specific solute that will overwhelm reabsorptive capacity
38
how are transporters distributed in the nephron
- each zone of the nephron has transporters for specific solutes
39
reabsorption: how does kidney filtrate modified through the nephron (3)
- 20% of the plasma volume entering the glomerulus is deposited into the Bowman's capsule
- over 19% is reabsorbed
- less then 1% is excreted
40
reabsorption: glucose (2)
- reabsorbed by secondary transport and taken up by the blood
- Na+/K+ ATPase creates negative potential to drive Na+/glucose co-transporter
41
reabsorption: Na+ and Cl-
- primary and secondary active transport
42
passive reabsorption: osmosis (2)
- as Na+, Cl-, and other solutes are reabsorbed actively, the extracellular fluid (EF) is more concentrated than fluid in lumen
- causes water to move out of the lumen to higher osmolarity
43
passive reabsorption: passive diffusion (2)
- as water leaves by osmosis, other substances (urea) becomes more concentrated in lumen
- substances by out of lumen by passive diffusion down its concentration gradient
44
what kind of molecules are moved during secretion (5)
- K+
- NH4+
- H+
- pharmaceuticals
- water-soluble vitamins
45
what is required for secretion (2)
- transport proteins
- energy
46
proximal tubule specialization
- most solute and water reabsorption
47
distal tubule specialization
- reabsorption completed for most solutes here
48
collecting duct specialization (2)
- drains multiple nephrons
- carries urine to renal pelvis
49
what accounts for the differences in transport and permeability in tubule regions of the nephron
- differences in epithelium along the tubule
50
proximal tubule epithelium (2)
- long microvilli extend into lumen
- tight junctions between cells
51
loop of Henle descending limb epithelium (2)
- lack tight junctions between cells
- lack microvilli
52
loop of Henle ascending limb epithelium (2)
- microvilli extend toward the basolamina
- tight junctions between cells
53
collecting duct epithelium (2)
- contains principal and intercalated cells
- tight junctions between cells
54
how is reabsorption conducted in the proximal tubule (2)
- many solute reabsorbed by Na+ cotransport
- water follows by osmosis
55
what is reabsorbed in the proximal tubule (11)
- Na+
- Cl-
- K+
- Ca2+
- HCO3-
- water
- glucose
- amino acids
- vitamins
- urea
- choline
56
what is secreted in the proximal tubule (4)
- H+
- NH4+
- toxins
- drugs
57
what is reabsorbed in the descending limb
- water
58
what is reabsorbed in the ascending limb (6)
- Na+
- Cl-
- K+
- Mg2+
- Ca2+
- NH4+
59
what is reabsorbed in the distal tubule (4)
- Ca2+
- Na+
- Cl-
- water
60
what is secreted in the distal tubule (2)
- H+
- K+
61
what is reabsorbed in the collecting duct (8)
- Na+
- Cl-
- K+
- Ca2+
- HCO3-
- H+
- urea
- water
62
what is secreted in the collecting duct (3)
- K+
- H+
- NH4+
63
what occurs in the descending limb of the loop of Henle (3)
- water is reabsorbed
- volume of primary urine decreases
- primary urine becomes more concentrated
64
what occurs in the ascending limb of the loop of Henle (3)
- no water movement, impermeable to water
- ions are reabsorbed
- primary urine becomes dilute
65
how does the osmotic gradient change after the loop of Henle (2)
- reabsorbed ions accumulate in interstitial fluid
- osmotic gradient created in the medulla
66
nephron countercurrent multipliers: structures (2)
- loop of Henle
- collecting duct
67
countercurrent multiplier function
- create osmotic gradients that facilitate transport processes
68
how is the gradient of the renal medulla maintained
- vena cava capillaries
69
what does the osmotic concentration of the final urine depend on
- permeability (aquaporins) of the distal tubule and collecting duct, which can be regulated
70
what urine will result from impermeable distal tubule and collecting duct
- dilute urine due to low water reabsorption
71
what urine will results from permeable distal tubule and collecting duct
- concentrated urine due to high water reabsorption
72
mechanism for concentrating urine (4)
1. ascending limb of loop of Henle actively pumps Na+ out of tubule lumen
2. Cl- and K+ follow
3. causes increased ion concentration in interstitial fluid of medulla
4. water moves passively out of the descending limb by osmosis
73
how does the vasa recta function with the loop of Henle (6)
1. ions pumped out of ascending loop (↑osmotic pressure outside, ↓OP inside)
2. water flows out of descending tubule by osmosis (↑OP in descending tubule, becoming more [ ])
3. blood entering vasa recta is isoosmotic with the cortex
4. as blood moves deeper into medulla, it loses water and picks up ions from interstitial fluid (↑osmolarity)
5. when blood of vasa recta flows back toward cortex, high plasma osmolarity attracts water being lost from descending limb, ↓osmolarity of the blood
74
what occurs in longer loop of Henle (2)
- medulla gradient is larger
- more water reabsorption is achieved, helping with water conservation
75
excretion process (3)
- urine leaves kidneys and enters urinary bladder via ureters
- urine temporarily stored in the bladder
- urine leaves bladder via urethra
76
what controls urine flow from the bladder
- sphincters of smooth muscle
77
what controls the sphincters opening/closing at the urethra (2)
- spinal cord reflex arc
- can be influences by voluntary controls
