Kidneys Flashcards
1
Q
Name various roles of the kidneys
A
- Regulation body fluid osmolarity & volume (Na important)
- Regulation body electrolytes
- Acid/ base homeostasis (pH H+ moderation)
- Excretion metabolic waste products
- Renal hormone production (erythropoietin/ Vit D)
2
Q
Describe the position of the kidneys
A
Left: Adjacent to costa L1, L2, L3
Right: More cranial, T13, L1, L2
3
Q
Describe the location of the kidneys in relation to the peritoneum?
A
Retroperitoneal
4
Q
Describe the structures that border the kidneys
A
- Ventral to sub lumbar muscles
- Retroperitoneal
- Right is usually more richly anchored to abdominal roof
- Dorsally covered by perirenal fat
5
Q
Identify the classification of rodent kidneys
A
Unilobar & unipyramidal medulla
6
Q
Identify the classification of ox kidneys
A
Multilobal (with lobation apparent on kidney surface) & limited fusion of cortical & medullary components
7
Q
Identify the classification of porcine kidneys
A
Multilobar & fused cortex
8
Q
Identify the classification of cat/dog/sheep kidneys
A
Multilobar & fused cortex & medulla
9
Q
Identify the classification of equine kidneys
A
Multilobar, fused cortex & medulla & heart shaped!
10
Q
What is the basic unit of a kidney?
A
RENAL LOBE
11
Q
What does the renal lobe consist of?
A
Cap of cortical tissue & pyramid of medullary tissue
12
Q
What does the kidney sinus contain and where is it located?
A
Located at the renal hilus (indentation)
Sinus contains ureter, renal artery and vein, lymph vessels and nerves.
13
Q
Describe the renal pelvis
A
A funnel shaped structure that receives urine from the papillary ducts of the kidney and passes it into the ureter
-Extends into renal parenchyma dorsally & ventrally by means of curved diverticula, the recesses of the renal pelvis
14
Q
Describe the locations of the renal medulla, renal pelvis and cortex?
A
Cortex is “external”
Medulla is between cortex and renal pelvis
15
Q
What are renal papillae?
A
The apices of the renal pyramids, the base of which are at the level of the renal cortex
16
Q
What are papillary foraminae?
A
The openings of the papillary ducts that pass urine into the renal pelvis, which leads to the ureter.
17
Q
What is a nephron?
A
Continusous tube that serves for urine production + regulation of volume and composition of extracellular fluid
–> Glomerular capsule –> proximal convoluted tubule –> proximal straight tubule –> loop of henle –> distal straight tubule –> distal convoluted tubule –> collecting tubule
18
Q
What is a renal corpuscle?
A
Glomerulus + glomerular capsule
19
Q
Where are renal corpuscles located?
A
Cortex (not the medulla)
20
Q
Describe the anatomy of the nephron’s functional unit
A
RENAL CORPUSCLE
Glomerulus + afferent/ efferent arterioles + bowman’s capsule
21
Q
How do afferent and efferent arterioles regulate glomerular filtration?
A
Constriction (to conserve) & dilation (to remove more)
22
Q
What is the function of the afferent arteriole?
A
Deliver blood to the glomerulus from the interlobular renal artery. Constrict or dilate to slow/speed up GFR
23
Q
What is the function of the glomerulus?
A
Blood is pushed through fenestrated capillaries to form ultra filtrate of plasma
24
Q
What is the function of the proximal tubule?
A
- Reabsorbs NaCl & H20, HCO3-glucose & proteins, K+, phosphate, Calcium, Magnesium, urea
- Secretes organic anions and cations
25
What is the function of the Loops of Henle?
Reabsorbs 15-25% NaCl
26
What is the function of the distal tubule?
Major site of Ca++ excretions
27
What is the function of the Principle and intercalated cells of the collecting duct?
Principle cells= reabsorb water & urea (medulla), interact with ADH (to reabsorb Na+ & CL- & secrete K+) & Aldosterone
Intercalated cells= Secrete H+, reabsorb K+
28
What is spesh about the glomerular capillary endothelium?
Presence of fenestrated pores for filtration of blood to plasma ultra filtrate
29
What specialised cells exist as part of the glomerulus to aid in blood filtration?
1. Fenestrated capillary endothelium
2. Basement membrane
3. Podocytes
30
What type of nervous innervation do the kidneys have?
Sympathetic
31
What is the role of the proximal convoluted tubule?
- Drains bowman's capsule
- Reabsorption of nutritionally important substances
- Reabsorption of H20, Na, glucose, AAs
32
What is the role of the loop of henle?
Reabsorbs water & ions from the urine & controls urine conc
33
What is the role of the distal convoluted tubule?
Regulates K+, Na+, pH & further dilutes urine
34
What is the role of the collecting tubule?
Drains nephron
Final Na+ regulation
Reabsorbs 15-25% NaCl
35
Where does the blood supply to kidneys come from?
Renal artery that arises from the aorta. Divides into segmental arteries that supply the hilus --> branch into lobular arteries --> interlobular arteries --> afferent arterioles
36
How does blood drain from kidney?
Leave glomerulus via efferent arterioles --> travel around peritubular capillary network (around loop of henle) --> venous channels that make hepatic vein that eventually joins the inferior vena cava.
Veins= satellite & stellate veins
37
How do the afferent arterioles regulate the blood supply to the kidneys?
Afferent arterioles are close to the distal tubule (specifically the macula dense) so can signal to the
38
What is the function of stellate veins?
Veins that drain the capsule & outer cortex into interlobular veins
39
Describe the epithelium of the proximal collecting tubule
Simple cuboidal epithelium
Apical surface microvilli
Basal striations
Strongly eosinophilic cytoplasm
40
Describe the epithelium of the loop of henle
Simple squamous epithelium
| Large nuclei which bulge into lumen
41
Describe the epithelium of the distal convoluted tubule
Simple cuboidal epithelium
No brush border!!
Larger lumen
Pale eosinophilic
42
Describe the epithelium of the collecting tubules
Thick simple cuboidal epithelium
Central round nucleus
Cells slightly bulge into lumen
43
What is ADH
Anti-diuretic hormone
44
What is the basic function of ADH
Acts on tubules to promote resorption of water into the medulla
45
Where is ADH released from?
Pituitary gland
46
Where is aldosterone released from?
Adrenal cortex
47
What is the function of aldosterone?
Promotes Na and H20 absorption
| Involved in acid/base balance
48
What is the juxtaglomerular apparatus?
Specialised structure located as vascular pole of corpuscle b/w afferent & efferent arterioles that helps regulate renal blood pressure.
49
What is the juxtaglomerular apparatus comprised of?
1. Macula densa
2. Juxtaglomerular cells
3. Mesangial cells 8
50
Describe the macula densa
columnar epithelial cells of the DST/DCT touching vascular pole of renal corpuscle
51
Where are macula densa cells located?
On DCT/ DST. In contact with vascular pole of corpuscle (no basement membrane in between), specifically the mesangial cells
52
What is the role of the macula densa?
Act as a chemoreceptor to mediate NaCl conc
53
Where are mesangial cells located?
Between the arterioles and the macula densa, extending into the glomerulus
54
What is the role of mesangial cells?
Apparently for chemoreception, phagocytosis, support. Overall they influence glomerular perfusion!!
55
Where are juxtaglomerular cells located?
Along the afferent arteriole, where it enters the renal corpuscle
56
What is the role of juxtaglomerular cells?
Baroreception
| Release of renin!!
57
Describe the histology of the urinary passage (renal pelvis to urethral opening)
Transitional epithelium
Impermeable (tight junctions)
Epithelium > lamina propria > tunica muscularis of 3 layers smooth muscle (not bladder) > adventitia/ serosa depending on position
58
What about the histology of the renal pelvis lends horsies their unique urine?
mucus glands in pelvis submucosa & proximal ureter
59
What are the three areas of the bladder?
Apex (cranial)
Body (main)
Neck (caudal)
60
What're the organs comprising the urinary system
kidney > ureters > bladder > urethra
61
What portions of the urinary system are shared with the repro tract in the male & female?
Male- none
| Female- urethra shared at vestibule
62
Briefly describe the innervation of the kidney
- Sympathetic NS innervation
- Nerve endings on afferent & efferent arterioles
- Noradrenaline
- B adrenergic receptors
63
What are the 6 hormones that exert activity over the kidneys?
1. Antidiuretic hormone (ADH)
2. Aldosterone
3. Atrial Natriuretic peptides (ANPs)
4. Parathyroid hormone
5. Angiotensin II
6. Vitamin D
64
Where is ADH released from?
Posterior pituitary
65
What is the action of ADH on the kidney?
Promotes H20 reabsorption in the collecting ducts
66
Where is aldosterone released from?
Adrenal cortex
67
What stimulates the release of aldosterone?
Liver releases angiotensinogen --> activated by RENIN from juxtaglomerular cells --> active form angiotensinogen II stimulates aldosterone release from adrenal cortex
68
What is the action of aldosterone on the kidneys?
Adds Na channels to collecting tubule --> increases Na reabsorption back into blood
69
Where are Atrial Natriuretic Peptides (ANPs) released from?
Cardiac cells
70
Describe the action of ANPs
Inc GFR through dilating aas --> Na excretion --> Dec blood volume --> Dec BP
71
Where is parathyroid hormone released from?
Parathyroid gland
72
Describe the action of parathyroid hormone on the kiddies
Phosphate excretion, Ca reabsorption, VitD production
73
How does oncotic pressure influence glomerular filtration?
Opposes filtration into bowman's space
74
Describe how starling's forces aid glomerular filtration
Force in glomerular capillaries are affected by dilation/constriction of afferent arterioles --> force determines how much blood is released
75
Describe how glomerular cells and capillary blood pressure in interact to affect GFR please
Pressure in glomerular capillary --> Mesangial cells relax to ^ SA --> Podocytes relax to ^ SA --> GFR increases
76
Which basic cardiovascular and (glomerular) anatomic factors affect GFR? Weird question soz
```
Net Filtration pressure
Blood pressure
Hydrostatic pressure bowman's space
Oncotic pressure in glomerular capillary
Permeability
Surface area
```
77
Which factors affect net filtration pressure in the glomerulus?
Net filtration pressure (NFP) is the sum of the opposing hydrostatic and colloid osmotic (oncotic) pressures acting across the capillary
1. Hydrostatic blood pressure
2. Hydrostatic pressure in bowman's space
3. Oncotic pressure in glomerular capillary
78
What are the 4 factors that determine which molecules are filtered by the glomerulus
1. Filtration barrier (3 layers of filtration + influence on size + charge)
2. Starling forces (bulk flow process)
3. Autoregulation (controls renal blood flow & GFR)
4. Influence of Hormones/ Nerves (regulates blood flow & GFR e.g. haemorrhage)
79
what are the constituents of glomerular filtrate?
Water + small solutes (except if bound to proteins e.g. penicillin) --> progressive molecular filtering as molecules increase
80
What is the equation to describe GFR?
GFR= NFP (blood pressure - hydrostatic pressure bowman's space - glomerular oncotic pressure) x Permeability & SA
81
What is an example of pre-renal kidney problems?
Blood flow reduced to kidney, so cannot adequately filter
| E.g. stenosis (narrowing BV), heart failure, haemorrhage, fluid loss from body (diarrhoea), low protein
82
What is an example of intra-renal failure?
Glomerular nephritis
83
What is an example of post-renal failure?
Kidney stones
| Anything slowing or stopping filtering process e.g. kinked urethra
84
How is GFR regulated?
Autoregulation!
GFR and renal blood flow are autoregulated to minimise fluctuations in blood pressure accompanying daily activities unrelated to need for kidneys to regulate H20 and salt excretion, such as normal elevation in BP accompanying exercise.
85
Increased vasoconstriction = ____ GFR
Decreased
86
What is the limiting step in the formation of Angiotensin II?
Renin, as released by the juxtaglomerular cells
87
Which two intrarenal mechanisms contribute to autoregulation?
1. Myogenic mechanisms --> smooth muscle contracts inherently in response to increased arterial pressure & vice versa. Afferent arteriole automatically does this when stretched b/c of an inc arterial driving pressure, limiting blood flow to glomerulus despite elevated arterial pressure.
2. Tubuloglomerular feedback --> Macula densa chemoreceptor cells. In response to a rise in salt in distal tubule, the macula densa cells release ATP and adenosine, constricting afferent arterioles & reducing glomerular blood flow & returning GFR to normal. When salt is low in distal tubule (due to low GFR and low arterial pressure) macula densa cells secrete nitric oxide which causes vasodilation.
88
How will a large decrease in arterial blood pressure due to haemorrhage effect renin secretion and nervous activity? And what does this mean for overall GFR?
Haemorrhage = Dec arterial blood pressure.
INC activity of renal sympathetic nerves + juxta cells sensing low pressure --> INC renin secretion --> INC angiotensin II (= INC tubular Na+ & H20 reabsorption)--> INC constriction of renal arterioles = DEC RBF & GFR
89
Name 3 vasoconstrictors
Angtiotensin II
Sympathetic nerves
Endothelin
90
Name 3 vasodilators
Prostaglandins
Nitric Oxide
Bradykinin
91
What is the conc of Ammonium ions in wee?
30-50mEq
92
What is the conc of Na+ ions in pee?
50-130mEq
93
What is the conc of K+ in urine?
20-70mEq
94
In what part of the nephron does regulated Na+ reabsorption occur?
Collecting duct
95
Angiotensin II stimulates the secretion of what hormone?
Aldosterone
96
What structure detects changes in the delivery of Na+ to the distal tubule?
Macula Densa
97
Which regulatory molecule stimulates an INC in GFR and a decrease in Na+ reabsorption?
Atrial natriuretic peptide
98
The sympathetic nervous system stimulates renin release from the __ cells
Juxtaglomerular cells
99
Where are the juxtaglomerular cells located?
Afferent arterioles
100
In which part of the nephron is the macula densa located?
Distal tubule
101
What is the stimulus for release of Angiotensin II?
Renin + dec extracellular volume (ECV)
102
What is the action of Angiotensin II?
Constricts afferent & efferent arterioles to drop RBF & GFR via mesangial cell contraction
103
What is the stimulus for sympathetic nerve activation to the kidneys?
Decreased ECV
104
Describe how decreased ECV stimulates the nervous system of the kidneys & what ultimate effect this has?
Dec ECV = noradrenaline released by the sympathetic nerves & circulating adrenaline binds to adrenoreceptors on afferent arterioles --> DEC GFR & RBF
105
What is endothelin?
A vasoconstrictor that acts on the kidneys
106
What causes the release of endothelin?
1. Angiotensin II
2. ADH
3. Shear stress of RBCs scraping endothelium
107
What is the action of prostaglandins on the kidney?
Vasodilation --> prevent excessive renal ischemia where renal vasoconstriction is too severe!
108
What is the stimulus for the release of prostaglandins?
Angiotensin, shear stress in BV, vasoconstriction that is too severe!
E.g. during dehydration
109
What is the stimulus for the release of nitric oxide?
Shear stress in BV, bradykinin
110
What is the action of nitric oxide?
Endothelial relaxation --> vasodilation
111
In terms of H20, is more excreted or reabsorbed each day?
Reabsorbed! (178L)
| 0.5-3L excreted
112
In terms of Na+, is more filtered, excreted or reabsorbed each day?
Reabsorbed! (25,050mEq)
| 100-250mEq excreted
113
Is Na+ a normal constituent of urine?
yes
114
Is K+ a normal constituent of urine?
yep
115
Is NH4+ a normal constituent of urine?
yah
116
Is Ca++ a normal constituent of urine?
uh huh
117
Is Cl- a normal constituent of urine?
Yas
118
Is glucose a normal constituent of urine?
nope
119
Is Urea a normal constituent of urine?
Yas qween
120
Are amino acids a normal constituent of urine?
no
121
Is creatinine a normal constituent of urine?
yes
122
Is bilirubin a normal constituent of urine?
nada
123
Are ketones a normal constituent of urine?
fk no
124
In terms of Na+ reabsorption in the PCT, how is Na+ reabsorbed from the tubular lumen? (transport systems!)
Luminal entry= carrier mediated & Na+ channels
125
In terms of Na+ reabsorption in the PCT, how is Na+ transported into plasma? (transport systems!)
Via Na+/K+-ATPase pump on the basolateral aspect of the membrane (i.e away from the lumen!)
126
How is Na+ transported at the lumen of the proximal tubule (remember, prox tubule reabsorbs nutritionally important solutes!)
1. Na+ co-transported with glucose/ phosphate/ amino acids
| 2. Na+ counter transported with H+
127
How is Na+ transported at the lumen of the loop of henle?
1. Na+ is co-transported with K+ and 2Cl-
| 2. K+
128
What is the 4 major roles of selective excretion in maintaining internal fluid homeostasis?
1. Maintenance of proper levels of inorganic solutes (Na+, K+ Cl-, H+, CO2)
2. Maintenance proper plasma volume
3. Remove shit from blood
4. Maintenance osmotic balance
129
What is the importance of peritubular capillaries?
They supply renal tissue with blood and are important in exchanges between the tubular system and blood during conversion of the filtered fluid into urine. They are intertwined around the tubular system. They rejoin venues and ultimately drain into the renal vein, by which blood leaves the kiddy.
130
Describe glomerular filtration
As blood flows through the glomerular capillaries, blood pressure forces protein-free plasma through fenestrations in the capillaries, into bowman's space. This is a non-selective filtration process.
131
Where does the proximal tubule lie?
Kiney cortex
132
What ultimately happens to substances that are reabsorbed via the tubules?
Peritubular capillaries carry substances to the venous system then to heart to be recirculated.
133
Describe the tubular secretion of the proximal tubule.
Tubular secretion is the selective transfer of substances from the peritubular capillary blood into the tubular lumens. E.g. of organic ions
134
What is the overall role of the loop on henle?
Osmoconcentration
135
What is the position of cortical nephrons vs. juxtamedullary nephrons?
Cortical nephrons= outer cortex
| Juxtamedullary nephrons= inner cortex
136
Which type of nephron plunges further into the medulla?
Juxtamedullary nephron plunges way further into the medulla, whereas cortical nephrons (at the outer cortex) form a hairpin loop and only dip into the medulla
137
What are vasa recta?
The peritubular capillaries of juxtamedullary nephrons. These capillaries form hairpin vascular loops which run in close association with the tubules. This parallel arrangement forms the striated appearance of the medulla.
138
Does glomerular capillary blood pressure favour or oppose glomerular filtration?
Favour
139
Does plasma-colloid osmotic pressure favour or oppose glomerular filtration?
Oppose
140
Does bowman's capsule hydrostatic pressure favour or oppose glomerular filtration?
Oppose
141
Two intrarenal mechanisms contribute to auto regulation of glomerular filtration. Describe the myogenic mechanism.
- Inherent property of vascular smooth muscle, that arterioles contract in response to stretch due to an increase in pressure
- Afferent arterioles contract in response to INC arterial pressure, limiting blood supply to glomerulus
142
Two intrarenal mechanisms contribute to auto regulation of glomerular filtration. Describe the tubuloglomerular feedback mechanism.
This involves the juxtaglomerular apparatus. The macula densa cells detect changes in salt levels.
- If GFR INC due to arterial pressure, INC fluid & INC salt so macula densa cells release ATP and adenosine.
- This causes adjacent arterioles to constrict, DEC glomerular BF and returning GFR to homeostasis.
143
How does extrinsic sympathetic control of the GFR interact with autoregulatory control of GFR?
Extrinsic sympathetic nervous system innervation can override intrinsic autoregulatory control.
144
What is the role of Na+ reabsorption in the proximal tubule?
Reabsorption of glucose, amino acids, Cl-, urea, H20
145
What is the role of Na+ and Cl- reabsorption in the loop of henle?
Critical role in the kidneys ability to adjust ECF osmolality by producing urine of varying conc and volumes, depending on need to conserve or eliminate salt or H20
146
what is the role of Na+ absorption in the distal portion of the nephron?
Regulation of ECF volume, secretion of K+ and H+
147
Where is the only place in the nephron tubule that salt isn't reabsorbed?
Descending loop of Henle! important for osmoconcentration gradient
148
There are functional distinctions between the limbs of the loop of henle that allow it to form a vertical concentration gradient. Describe the functional significance of the descending limb.
- Highly permeable to H20 (aquaporins abundant, always open)
- No active transport of Na+
149
There are functional distinctions between the limbs of the loop of henle that allow it to form a vertical concentration gradient. Describe the functional significance of the hairpin turn.
- Low water permeability (no aquaporins)
| - No active salt transport
150
There are functional distinctions between the limbs of the loop of henle that allow it to form a vertical concentration gradient. Describe the functional significance of the ascending limb.
- Active transport of NaCl out of the tubular lemon into ISF
| - Always permeable to H20, so salt leaves tubular fluid without H20 osmotically following.
151
Where is angiotensin produced?
Liver
152
What are the major actions of Angiotensin II?
Na & H20 retention @ proximal tubule and vasoconstriction.
Stimulation aldosterone secretion from adrenal gland vasoconstriction.
Stimulation ADH from hypothalamus & thirst
153
How does Angiotensin II affect GFR
reduces
154
How does Angiotensin II increase Na & H20 retention and where does this happen?
Proximal tubule
Activates Na+/H+ antiporter
Stimulates GIT to reduce cAMP
155
Where is renin produced
Juxtaglomerular cells
156
Describe the pathway through which Angiotensin II is produced?
Renin (from juxtaglomerular cells) turns Angiotensinogen (in plasma) into angiotensin I --> ACE cleaves this to form effector molecule Angiotensin II
