1
Q
What are the basic components of the Urinary system?
A
- Kidneys
- Uterers
- Bladder
- Urethra
2
Q
What is the function of the uterers?
A
Move the urine from the kidneys to the bladder
3
Q
What is peristalsis?
A
It is the symetrical contraction of muscle and is a primary method of transportation of urine from the kidneys to the bladder.
4
Q
How much liquid can the bladder hold?
A
400 - 600 mL
5
Q
When does the bladder signal to void the liquid stored?
A
At 75%
6
Q
What is the function of ureter?
A
Movement of urine from the bladder out of the body
7
Q
Describe the process of urine removal from the bladder.
A
- Stretch of the bladder stimulates the PNS to contract smooth muscle and relax the internal urethral sphincter
- After the voluntary controlled external urethral sphincter is relaxed
- Urine exits the urethra
8
Q
What are the three zonas of the adrenal gland cortex?
A
- Zona glomerulosa
- Zona fasciulata
- Zona reticularis
9
Q
What hormones are secreted by the first zona of the adrenal gland cortex?
A
Zona glomerulosa - aldosterone
10
Q
What hormones are secreted by the second zona of the adrenal gland cortex?
A
Zona fasciulata - cortisol
11
Q
What hormones are secreted by the third zona of the adrenal gland cortex?
A
Zona reticularis - sex hormones
12
Q
What hormones are secreted by the medula of the adrenal glands?
A
Catecholamines - adrenaline & noradrenaline
13
Q
What are the four main homeostatic functions that are performed by the kidneys?
A
- Salt and water regulation
- Acid regulation
- Blood pressure regulation
- Removal of by-products, toxins, drugs
14
Q
What can we consider kidney as?
A
Kidney can be considered as:
- Major organ that helps to control whole body homeostasis
- An endocrine gland
15
Q
What are some of the endocrine functions of the kidneys?
A
- Renin production
- Erythropoietin (EPO) production
- VItamin D activation/deactivation
16
Q
Show all elements of the diagram
A
17
Q
What are nephrons?
A
Nephrons are functional components of kidneys.
18
Q
What are the functions of nephrons?
A
- Filtration of plasma
- Concentrating urine
- Removal of toxins and by-products
19
Q
What are the two components of a nephron?
A
- Tubular
- Vascular
20
Q
Show all elements of the following diagram
A
21
Q
What are the two main types of nephrons?
A
- Juxtamedullary
- Cortical
22
Q
What are the more common type of nephron?
A
Cortical is more common than juxtamedullary
23
Q
What is the difference in the loop on Henle in the two nephrons?
A
Juxtamedullary nephrones have long loops of henle while cortical have short once.
24
Q
What is the difference in the vascular structure between juxtamedullary and cortical nephrons?
A
Juxtamedullary have a vasa recta structure - meaning straight blood vessels. Cortical have a meshed structure.
25
What is the glomerulus?
It is the functional unit of filtration
26
What is the result of high pressure in arterioles?
Ultrafiltration
27
Which blood vessel of the glomerulus is larger?
The afferent artriole is larger than the efferent artriole
28
What is the function of smooth muscle within the arterioles?
They are able to regulate blood pressure with greater control
29
How does the filtrate move through the glomerulus?
1. In capilaries
2. Through the bowman's capsule
3. Into the proximal tubule for further prosessing
30
Which 2 structures are technically fuzed together in the juxtaglomerular aparatus?
The afferent arteriole and the distal tubule
31
What are the juxtaglomerular granular cells, what is their location and function?
1. Granular cells are specialised smooth muscle cells
2. Found primarily on the afferent arteriole
3. Function: synthesise, store and secrete renin
32
What is the process of renin release and what does it influence?
1. Renin is released by the granulwar cells in response to: low blood pressure, low NaCl in tubules via macula densa cells and sympathetic nervous drive
2. Renin is used in the RAAS system
33
What are the three main functions of the nephron?
1. Glomerular filtration
2. Tubular secretion
3. Tubular resorbtion
34
How do capilary blood vessels facilitate the movement of substances in the glomerulus?
1. Blood vessels are **fenestrated**
2. Fenestrations **allow the pessage of some waste products but not whole cells**
3. They move according to **concentration gradients**
35
What are the three layes of the glomerular barrier that facilitate filtration?
1. Lumen of the capilaries
2. Basement membrane
3. Lumen of Bowman's capsule
36
What is the glomerular filtration rate?
It is the rate of filtered fluid through both kidneys per minute. It is a measure of total kidney function. Normal 125 ml/min
37
How can we calculate the GFR?
By using substances that can be freely filtered and not at all resorbed. SUch substance is creatinine - a bi-product of muscle metabolism.
38
What s the formula for GFR?
GFR = (urine concentraion x urine flow)/plasma concentration
39
What is bowman's capsule hydrostatic pressure?
It is the pressure that oposes filtration due to the fact that the bowman's capsule already has some liquid in it, so the liquid pushes in the opposing direction to the filtration
40
What is plasma colloid osmotic pressure?
It is a pressure that is excereted by large protein molecules that keeps the water and deisolved substances within vascular system
41
What is the relationship between GFR and Net filtration pressure?
Increased net filtration pressure increases the GFR (the relationship is proportional)
42
What are the two autoregulation mechanism that are used to control GFR?
1. Myogenic mechanism
2. Tubularglomerular feedback
43
What is the myogenic mechanism?
It is the automatic contraction of muscles in response to stretch to high blood flow
44
What is the tubularglomeluar feedback?
1. Detection of concentration of Na+ and Cl- in the distal tubule by macula densa cells
2. If flow rate is high = Na+ and Cl- is high = vasoconstriction = reduction in GFR
3. If flow rate is low = Na+ and Cl- is low = vasodilation = increased GFR
45
What is the diarrhoea cascade and how does it reduce GFR?
1. Diarrhoea occurs
2. Recudction in plasma volume (colloid osmotic pressure increases)
3. Decrease in venous return
4. Reduction in blood pressure (Reduced capillary pressure)
5. Baroreceptor stimulus
6. Contriction of afferent arteriole
7. Reduced flow
8. Reduced GFR
46
What are podocytes?
They are cells that cover basal lamina of the bowman's capsule
47
How can podocytes function?
The movement of actin like filaments allows them to increase their size, constrict the area of filtration thus reduce GFR
48
What can go wrong with glomerular filtration?
The destruction of podocytes, basement mebrane or charge barrier will allow proteins to be filtrated, thus reduce the plasma-colloidosmotic pressure. This can lead to back pull of fluids into the blood vessels resulting in oedema.
49
What is the reabsorbtion in the tubules, how is it achived and what regulates it?
1. Reabsorption - the taking up of solutes fomr the filtrate back into the peritubular capilaries.
2. Substance such as gucose, amino acids, sodium, Cl- and water can be reabsorbed
3. This is achieved by osmosis, diffusion and active processes
4. Can be regulated by Aldosterone and Vasopressin
50
What is ecretion in the tubules, how is it achieved and what can regulate it?
1. Secretion - the taking up of solutes from peritubular capillaries back into the filtrate
2. K+, H+ and some drugs are secreted
3. Achieved by active processes
4. Can be hormone controlled by Aldosterone
51
How do the substances travel between the tubules and peritubular capilaries?
Through the interstitial fluid
52
What are the two modes of reabsorption?
1. Passive reabsorption - no energy use, down the concentration gradient
2. Active reabsorption - energy is used, against concentrwation gradient
53
What do cells in the proximal tubule have that helps them with reabsorption?
1. Microcvilli to increase surface area and thus increase reabsorption
2. Increased number of mitochondria for energy production for active transport
3. Glucose, amino acids, 65% of the sodium, Cl-, K+ and water are reabsorbed unregulated back into the peritubular capilaries
Overall the proximal tubules reabsorbes 65% of Na+ and 65% of water
54
What is rebasrobed in the descending loop of henle?
1. Water
2. NOT salts
55
What is reabsorbed in the ascending loop of henle?
1. Salts
2. NOT water
56
Overall how much salt and water does the loop of henle reabsorb?
25% of Na+ and 15% of water
57
What is the make up and function of distal tubule?
1. It rarley contains microvilli thus is perfect for secretion
2. Regulates pH through reabsorbtion of bicarbonate and secretion of hydronium ions
3. Fine tuning of Na+ and K+ with aldosterone
4. Secretion of drugs, metabolites and toxins
58
What happens in the collecting duct?
1. Fine tuning of water reabsorption controlled by vasopressin
2. Fine tuning of Na+ and K+ with Aldosterone
Overall collecting duct absorbes 4-5% Na+ and 5% of water
59
What is the countercurrent multiplier mechanism?
It is a mechanism by which desscending and ascending loops of henley are able to creat an osmotic gradients thus release more water and ions into the medula respectivley
60
What is a tubular maximum reabsorption?
It is a theoretic process in which active transport mechansism can reabsorbed substances at max. Beyond tubular maximum reabsorbtion rate can not increase and surplus of materials is lost in urine.
61
How does diabetes mellitus relate to maximum tubular reabsorbtion?
Diabetes mellitus is a condition where there is a large amount of glucose in blood.
Upon filtration in the glomerulus it is released in the tubular system.
Due to high amounts the glucose excides the maximum tubular reabsorption rate thus is excreted in urine.
This cause a shift in osmotic pressure against reabsorption thus increasing the urine volume.
Thus the thirst is increased.
62
Outline once again the cosntant and variable Na+ reabsorptions in the tubular system of the nephron.
Constant:
1. Proximal tubule 65%
2. Ascending loop of henle 25%
Variable:
1. Ditant convoluted tubule and collecting 0-10%
63
What is the importance of sodium in relation to water?
High sodium load = increased water reabsorption
64
What is the function of granular cells?
Granular cells on the afferent arteriole release renin in response to:
1. Low salt levels
2. Low blood pressure
3. Extra cellular fluid volume decrease
65
WHat are the three mechanisms of rening release?
1. Baroreceptor like - granular cells can act as baroreceptors
2. Stimulation from macula densa cells that detect changes in salt in the distal tubule
3. SNS signalling
66
What is the mechanism of renin?
Renin works via RAAS system to increase Na+ reabsorption
67
What is the mechanism of work of aldosterone?
Aldosterone is part of the RAAS and increase the reabsorption of Na+ by kidneys.
This changes the osmotic pressure to hold more water.
Thus increasing blood volume.
Increasing blood pressure.
68
What is the mechanism of work of angiotensin II?
Angiotensin II triggeres the relaaese of vasopressin by the posterior putunitary gland.
Vasopressin is able to increase the water reabsobtion in kidney tubules by binding to type 2 vasopressin receptor and increasing the work of aquapourins 2 and increasing there number in the collecting duct.
69
Describe the aldosterone triggered process in the cellular wall of the distal tubule in 5 steps.
1. Aldosterone binds with cytoplasmic receptor
2. Initiation of transcription
3. Synthesis of new protein channels
4. Modulation of existing channels
5. Modified and new channels are able to reabsorb more Na+ and secrete K+
70
What can overproduction due to very low blood pressure lead to?
Overproduction of aldosterone can lead to high fluid retention and this odema
71
How do ACE inhibitors help with regulation of hypertension?
ACE is a hormone that converts Angiotensin 1 into Angiotensin 2 trigeering aldosterone releae and vasocontriction.
IF ACE is blocked, angiotensin 1 can not be converted into angiotensin 2 thus it is undable to cause vasocontriction and increase sodium retention.
72
Describe the constant and variable water reabsorption paterns in the tubules of the nephron.
Constant:
1. Proximal tubule 65%
2. Descending loop of henle 15%
Variable:
1. Collecting duct and sital tubule 5-19.4%
73
How does the mechanism of vasopressin release occur?
1. Hypothelamus receptors detect the hgih salt concentrtions
2. Receptors send a signal to the posterior pituitary gland via neurosecretory cells
3. Vasopressin is released
74
How can baroreceptros stimulate the release of vasopressin?
1. Baroreceptors on the aortic arch detect low blood pressure and via SNS signal the posterior pituitary gland
2. Vasopressin is released
75
How can vasopressin act as a vasoconstrictor?
Vasopressin is able to binf to V1 receptor on the smooth muscle and cause the contriction of the muscle
76
What is the difference between osmolarity and blood pressure vasopressin release mechanisms.
Osmolarity:
1. Day-today response
2. Very sensetive
3. Fast acting
Blood pressure:
1. Emergencies only
2. Not sensetive to small changes
77
78
What intercellular events are triggered by vasopressin?
1. Vasopressin in blood is able to bind to the basolateral membrane of a distal or collecting tubule cell
2. This binding activates cyclic AMP
3. AMP promotes the insertion of the water channels in the opposite membrane that faces the tubule, which is impermiable to water without aquapourins
4. Water is able to enter the tubular cell and exit into the peritubular fluid and into the capillary
79
What happens with urine when there is no vasopressin present?
1. It becomes diluted
2. Volume increases
80
What happens to urine when vasopressin is present?
1. Urine reduces in volume
2. Urine is more concentrated
3. Blood pressure increases
81
Where is Atrial Natriuretic peptide released?
It is released from the atria of the heart
82
Where is Brain Natriuretic Peptide released?
It is released from the ventricles of the heart
83
What stimulates the release of ANP and BNP?
High plasma volume detected by the baroreceptors
84
What is the objective of ANP and BNP release and how do the peptides achive it?
Main objective: Reduction of blood pressure in nephron.
Methods:
1. Inhibition kidney Na+ reabsorbtion
2. Inhibitng the effect of RAAS
3. DIlation of afferent arterioles in glomerulus
Also inhibition of Sympathetic drive thus decrease in cardiac output
85
On a cellular level, how does ANP decrease the reabsorption of sodium?
1. ANP binds to sodium channels on the luminal membrane
2. Block the channels
3. Block sodium reabsorption
4. Block water reabsorption
86
How does ANP inbiti the RAAS?
ANP is able to inhibit the Aldosterone
87
How does ANP increases the GFR?
It is able to increase the GFR through vasodilation of the Afferent arteriole.
This means that more blood is able to travel for filtration increasing the GFR.
88
Why is K+ imortant?
K+ helps to regulate the resting membrane potential of cells thus cells are very sensetive to K+ fluctuations in the plasma
89
Which preocess relating to K+ occurs in the proximal tubule?
Constant active rebasorption, up to 100%
90
What process in regards to K+ occurs in ascending loop of henle?
Active reabsorption up to 20-30%
91
What process occurs in the distal tubule and collecting duct in regards to K+?
Controlled active secretion 1-80%
92
What hormone increases the secretion of K+?
Aldosterone through the Sodium - Potasium pump
93
During haemorrhage, what do kidneys do in regards to potassium?
Kidneys try to secrete as much potasium as possible in order to conserve as much sodium as possible.
94
How does respiratory acidosis occur?
Acidosis occurs due to increased CO2 levels in blood. Increaased CO2 increases the ionisation of H2CO3 to H+ and HCO3-.
95
How does metabolic acidosis occur?
Acidosis occurs due to increasing H+ levels in blood due to lactic acid or ketone bodies.
This reduces the amount of bicarbonate as they are used to buffer the said increase in H+
