The Renal System Flashcards
1
Q
what similarities does the renal system share with the GI system?
A
- excretion of waste
- absorption of nutrients
- secretes/influenced by hormones
2
Q
What are the functional units of the kidney and where are they located?
A
- Nephron
- renal cortex (outer layer of kidney) mainly
3
Q
Which hormones act on the kidney to regulate its function?
A
ADH, aldosterone, ANP
4
Q
what does ANP stand for?
A
atrial natriuretic peptide
5
Q
difference between the ureter and the urethra?
A
ureter- carries urine from the kidney to the bladder
urethre- bladder to outside
6
Q
where would you find the cortex in the kidney?
A
outside, around the pyramids
7
Q
What encapsulates the kidney?
A
renal capsule, further surrounded by adipose
8
Q
what 3 sections is the kidney broken down into?
A
- Cortex- ouster layer
- Medulla - inner layer
- renal pelvis
9
Q
what is contained within the cortex?
A
-glomeruli, proximal and distal convoluted tubules
10
Q
renal corpuscles
A
small units including the glomeruli
11
Q
how is the cortex of the kidney distinguished?
A
renal corpuscles, each of which consists of a glomerulus surrounded by bowman capsule.
(convoluted tubules are the bulk of the cortex)
12
Q
in an image of the pyramids what would be the larger tubes/holes and what would be the smaller ones?
A
larger- collecting ducts
smaller-loops of henle
13
Q
what would you find within the medulla
A
renal pyramids, containing the collecting ducts and loops of henle
14
Q
What does the pelvis do?
A
major selecting duct for the products of renal filtration (urine)
15
Q
what is the pelvis made up of?
A
major and minor calyx
16
Q
what is the renal sinus?
A
the hollow space inside the kidney capsule
17
Q
which tubule comes first… proximal or distal?
A
Proximal first
18
Q
where would you find peritubular capillaries and what do they do?
A
surround the nephron tubule
reabsorption and secretion
19
Q
does each nephron have its own blood supply?
A
yes
20
Q
where do the nephrons descend from and to?
A
the cortex into the medulla
21
Q
what are the 2 types of nephrons? and which are there more of?
A
- cortical nephron (80%)
- juxtamedullary nephron
22
Q
Cortical nephron
A
mostly in the renal cortex with just the tip in the renal medulla
23
Q
juxtamedullary nephron
A
just the top in th renal cortex and the body of the loop of hence is in the renal medulla
24
Q
does the sounding tissue around the loop of hence get more or less salty as you go down?
A
more salty
25
what are the 4 fundamental mechanisms that take place in the nephron?
filtration
reabsoption
secretion
excretion
26
does the afferent of the efferent arteriole go into the glomerulus?
the afferent
| alphabetical
27
explain the glomerulus
located in the bowman capsule, uses ultra filtration to produce glomeruli filtrate
28
what percentage of blood is filtered through the filtration membrane?
20%
29
what parts make up the filtration membrane?
- capillary endothelial fenestrations
- gel-like basement membrane
- slit diaphragms within filtration slits between the foot processes (pedicels) of podocytes
30
what makes up the glomerular filtrate?
water, urea, glucose and amino acids
| similar to plasma
31
what percentage of the cardiac output do the kidneys receive?
25%
32
what is the GFR? (definition)
the amount of filtrate that forms in BOTH kidneys every minute
33
what are the average filtration rates?
females- 105ml/min (1 litre in 9-10 mins)
males - 125ml/min (1 litre in 8 mins)
34
what are the average daily volumes of GFR produced?
F-150L
| M - 180L
35
how much GFR is reabsorbed
98-99%
36
what can GFR be used to assess?
renal function
37
what does GFR being too high indicate?
filtrate passes through the tubes too quickly and can't be reabsorbed
-diabetes mellitus and diabetes insipidus
38
what does GFR too low indicate
chronic renal failure
| waste products not excreted)
39
GFR can be measured by comparing the plasma and urine concentrations of a substance that is:
Freely filtered by the glomerulus
Is NOT reabsorbed nor secreted within the tubules
Is non-toxic and not metabolised by the body
40
what is used (mainly) to measure GFR in humans)
insulin
41
why is clearance of creatine less accurate at measuring GFR than insulin?
as it is secreted and reabsorbed
42
what id the equation for working out GFR (ml/min)
(Conc. of insulin (mg/ml) in urine) X using flow per unit time (ml/min)
/
Conc. of Insulin (mg/ml) in arterial plasma
43
When is ANP released from the atrial wall of the heart?
in response to increased blood volume
| released during hypertension to help promote increased excretion of water and salts in urine
44
What happens if GFR system in the kidneys fails?
- waste products accumulate in blood (urea, creatine)
- pH [H+] and electrolyte balance (Na+, K+) jeopardised
- blood volume control impaired (hypertension, oedema)
45
what is the main control systems for GFR regulation?
- Myogenic autoregulation
- tubuloglomerular feedback
- neuronal regulation
46
what does myogenic auto regulation control?
constriction/dilation of *afferent* arteriole in response to changes in blood pressure
-vasodilation in afferent arteriole, increased blood flow, inc. pressure in glom. capillaries, increased GFR
47
what does tubulogglomerular feedback control?
- macula dense cells (specialised cells) in the distal tubule monitor filtered Na+ (flow rate)
- If filtered Na+/flow rate increases, GFR is decreased
48
what does neuronal regulation control with GFR?
sympathetic mediated constriction of afferent arteriole -> decreased GFR
49
does the parasympathetic NS have an effect on the kidneys?
no, the parasympathetic NS has no effect on the kidneys (does affect the GI system)
50
What is absorbed within the proximal convoluted tubule?
- essential nutrients reabsorbed back into the blood from the filtrate
- water (65%), glucose, AAs and electrolytes
51
what does reabsorption of nutrients in the proximal convoluted tubule rely on?
secondary active transport of Na+
| powered by basolateral Na+/K+ ATPase pumps
52
what secretions take place in the proximal convoluted tubule?
H+ and organic ions (acid base balance and waste)
| -variable H+ secretion depending on the acid-base balance of the body
53
how is water reabsorbed in the loop of henley? and where
passively in the descending part f the loop
54
where is Na+ reabsorbed in the loop of henley and how?
- in the ascending loop
| - actively reabsorbed by K+/Na+/2Cl- cotransporters (powered by basolateral Na+/K+ ATPase pumps)
55
How does water being absorbed in the descending and Na+ being absorbed in the ascending loop affect the filtrate leaving the loop of hence?
-means that there is a smaller volume of hypotonic filtrate leaving the loop of henle and entering the distal tubule
56
what sort of system gets the maximum amount of fluid moved out of the loop of henle?
counter current multiplier system
57
the descending loop of henle
Descending limb permeable to water, but not to solutes
| Water exits descending limb by osmosis
58
the ascending loop of henle
Ascending limb impermeable to water but not to solutes
| Na+ (and Cl-) exit ascending limb by active transport
59
which hormone controls further reabsorption of water in the collecting duct?
ADH
| anti diuretic hormone
60
what do the long loops of henle in the juxtamedullary nephron establish? and why is this important?
-vertical osmotic gradient in the renal medulla
-counter current multiplication system
-Permits variable water reabsorption from collecting ducts under control of anti-diuretic hormone (ADH)
(Concentrated urine)
61
where is ADH secreted from?
posterior pituitary
62
what does ADH do?
increases the permeability of collecting ducts to water by promoting insertion of aquaporins... therefore less urine
-water conservation
63
what is ADH secreted in response to?
- An increase in body fluid osmolality (via osmoreceptors in hypothalamus)
- A decrease in blood volume/BP (via baroreceptor reflexes)
64
Over hydration... what happens
- Diuresis
- large volume of dilute urine
- No water conservation required
- No ADH released from posterior pituitary
65
Dehydration what happens?
- Water conservation required
- ADH released from posterior pituitary
- antidiuresis
- small volume of concentrated urine produced
66
what is the juxtaglomerular apparatus?
A cluster of renal cells located within the walls of the distal convoluted tubule and the afferent arteriole (“next to the glomerulus”)
macula dense cells, juxtaglomerular cells
67
what do macula densa cells decrease GFR in response to?
Increased Na+ levels in tubule
| Increased sympathetic nervous activity
68
What do Juxtaglomerular cells release renin in response to?
A drop in BP within afferent arteriole
| Renin activates the renin-angiotensin-aldosterone system to increase BP back to normal
69
how does the JGA monitor and responds to a fall in blood pressure and GFR
by activating the renin-angiotensin-aldosterone system (RAAS)
70
macula densa cells
regulate GFR in the short-term via tubuloglomerular feedback
Modified epithelial cells
Distal tubule
Monitor filtered Na+ within distal tubule
71
juxtaglomerular cell
Modified smooth muscle cells
Afferent arteriole
Secrete renin
72
Renin-Angiotensin-Aldosterone System(RAAS)
- renin released from juxtaglomerular cells in kidney in response to low BP
- renin act on angiotensinogen which is secreted from the liver
- angitensinogen is converted to angiotensin I
- angiotensin I is converted to angiotensin II by angiotensin converting enzyme
- Angiotensin II is a potent vasoconstrictor and causes release of aldosterone
- aaldosterone released from the adrenal gland which increases reabsorption of Na+ in the nephron
- osmosis, increase H2O reabsorption, larger Blood vol. and hence higher BP
73
What other hormone is released by the kidney in response to blood loss?
EPO
| Erythropoietin
74
what do ADH and RAAS both do?
lead to the conservation of water in the body.
75
ADH is a short-tem effector in response to dehydration
Increase in plasma osmolarity
Increased body loss of water (sweating during exercise)
Reduced intake of water (thirst centre in hypothalamus)
76
RAAS is a long-term response to decreased ‘Body fluid volume
Loss of both water and salt resulting in no change in osmolarity
Injury (blood loss) or illness (prolonged diarrhoea)
77
Atrial natriuretic peptide (ANP)
– opposes action of aldosterone and ADH increase excretion of water & Na+ (natriuresis
78
Aldosterone
water + Na+ reabsorption; K+ secretion)
79
Parathyroid hormone (PTH)
Ca2+ reabsorption)
80
ADH
water reabsorption
81
what are the 3 main functions of the urinary system?
-regulation, excretion and production
82
what does the urinary system produce?
Gluconeogenesis (production of glucose from non carbohydrate sources, i.e. protein)
Production of hormones (i.e. Erythropoietin, renin)
83
what does the urinary system excrete?
Removal of metabolic wastes (from the blood, which is excreted into the urine)
Removal of foreign chemicals from the body (pesticides, drugs and food additives)
84
what does the urinary system regulate?
water and inorganic ion balance (acid/base)
85
electrolyte imbalance leads to disease
K+ conc – reduced by 1/3 of K+ - paralysis – nerves unable to generate AP
Ca2+ conc – reduced by 1/2 - tetanic skeletal muscle contractions
86
where is Na+ largely located?
Largely located extracellularly – primary determinant of extracellular fluid volume
Disorders of sodium – think water content!
87
what is hypernatramia?
- Much rarer than hypo
| - Always associated with increased plasma osmolarity – potent stimulator of thirst
88
what is Hyponatramia?
low levels of sodium in the blood, range of causes that are present with varying blood volumes
89
where is K+ mainly located?
Largely located intracellularly – primary determinant of extracellular fluid volume
90
what is hypokalaemia?
low levels of K+ in the blood
91
what does hypokalaemia cause?
Causes: diuretics, diarrhoea/vomiting, hyperaldosteronism
Majority of deficit is intracellular
Leads to intracellular hyperpolarization (intracellular loss extracellular)
RMP further from threshold potential (muscle weakness)
92
Reason for hyperpolarisation with hypokalaemia-
low K outside, creates greater conc gradient with inside, natural leaky K channels are likely to leak ‘more’, thus more K leaves the cell, causing the hyperpolarisation. From researching a little, there appears to be more going on than just this, but was leading me more and more into electrophysiology.
93
Hyperkalaemia
high K+ in the blood
94
what does Hyperkalaemia
| cause
Renal failure, tissue damage, acidosis, aldosterone impairment (spironolactone)
Clinical features – ECG changes, Kussmaul breathing (hyperventilation)
Depolarisation of excitable cells
95
acidosis
- both K+ and H+ compete to be secreted into the urine. When acidosis is present more H+ makes it out and K+ is left behind to contribute to the rise in extracellular K+
96
The depolarisation as a result of hyperkalaemia-
high K outside causes an increase in voltage gated Na channel opening in the first instance, which depolarises the cell, then these channels are inactivated once it reaches a certain voltage leading to overall inhibition of the cell.
97
what are the 2 specialised cells determining final K+ secretion? location?
principle cells and intercalated cells
| -both located in the late DCT and cortical CD
