Renal/Urinary system Flashcards
(116 cards)
1
Q
What is the role of the urinary system?
A
→ Maintain water and chemical balance in the body
→ Endocrine roles
- RBC production
- Blood pressure
2
Q
What are the main components of the urinary system?
A
1) The kidneys
2) 2 ureters (one for each kidney)
3) Bladder
4) Urethra
5) Regulatory nerves & muscles
3
Q
What does the kidney structure allow?
A
- Blood to be brought into close proximity w/ nephron for filtering
- A pathway for urine to be removed from the kidney (to be stored then secreted)
- Protection
4
Q
Kidneys:
- Location
- Vessels passing through hilum
A
- Behind the peritoneum, surrounded by fat pad, below adrenal gland; right kidney lower bc of liver
- Located at the T12-L3 vertebral level
- Arteries, veins, lymphatics and nerves pass through hilum
5
Q
What are the structures of the kidneys?
A
- Cortex
- medulla
- pelvis
- fibrous capsule
6
Q
Inner medulla structure
A
- Divided into pyramids
- Each medullary pyramid ends in a papilla
7
Q
Outer cortex structure
A
- Continuous layer
- Renal columns
8
Q
Direction of urine flow
A
papilla → minor calyx → major calyx → renal pelvis → ureter
9
Q
Features of blood supply to the kidney
- What region does filtration occur
- Structure of the arteries leading up to the kidney
A
- Filtration occurs in the cortex of the kidney
- Renal arteries arise from the abdominal aorta
- Branching arteries get smaller & smaller until they reach the cortex
10
Q
Flow of blood to/through the kidneys
A
Renal arteries → series of arteries → afferent arterioles → glomerulus → efferent arteriole → peritubular capillaries → series of veins → renal vein → IVC
11
Q
What are vasa recta?
A
- Blood vessels alongside the loop of Henle of Juxtamedullary nephrons
- extensions of the peritubular capillaries
12
Q
What specialised cells do afferent arterioles have?
What do they form part of?
What is their function?
A
- Juxtagomerular cells
- Form part of JGA
- Detect change in pressure (mechanoreceptors)
13
Q
What is the nerve supply to kidneys?
A
- Renal plexus (network of autonomic nerves and ganglia)
- Sympathetic nerves act to adjust diameter of renal arterioles and thus regulate blood flow
14
Q
What are the two types of nephron?
A
- Cortical nephron
- Juxtamedullary nephron
15
Q
Cortical nephron features
A
- 85% (most abundant type)
- Lies mainly in cortex
16
Q
Juxtamedullary nephron features
A
- Extends deep into medulla
- Important for the formation of concentrated urine
17
Q
Nephron functions?
A
1) Selectively filter blood
2) Return anything to be kept to the blood
3) Carry waste away for storagee & expulsion
18
Q
Nephron components
A
- Bowmans capsule
- Renal tubules
- Collecting duct
19
Q
What is each nephron associated with?
A
- A glomerulus
- Peritubular capillaries
- Vasa recta
20
Q
Glomerulus features
A
- Filtration
- Thin-walled, single layer of fenestrated endothelial cells
- Fed and drained by arterioles
- High pressure and tightly regulated
21
Q
Peritubular capillaries
- Function
- Location
- Arise from?
- High/low pressure?
A
- Absorption
- Adjacent to renal tubules
- Arise from efferent arterioles draining glomerulus
- Low pressure
22
Q
Structure of renal corpuscle
A
- Consists of the glomerulus surrounded by the Bowmans capsule
- B/w these two structures is the blood-urine barrier
23
Q
Structure of Bowmans capsule
A
→ Two layers - Outer parietal layer - simple squamous - Inner visceral layer - podocytes → b/w two layers - "bowmans space" → Pedicels wrap around podocytes to form filtration slits
24
Q
Podocyte features
A
- Surround the glomerular capillaries
- V branched, v specialised epithelium
- Branches form interwining foor processes - ‘pedicels’
- Filtration slits form b/w pedicels
- Filtered blood (filtrate) goes thr’ slits & passes into Bowmans space
25
What does/doesn't the Blood-urine Barrier filter?
- Allows free passage of water and small molecules
- Restricts passage of most proteins
- RBCs not filtered
26
What are the 3 layers of the Blood-urine barrier?
1) Fenestrated endothelium of glomular capillary
2) Fused basement membrane
3) Filtration slits b/w the pedicels of the podocytes
27
What are the 4 section of the nephron and what do they allow?
- Proximal convoluted tubule (PCT)
- Loop of Henle
- Distal convoluted tube (DCT)
- Collecting duct
They allow reabsorption
28
Proximal convoluted tubule (PCT)
- Function
- Structure
- Surrounded by?
```
→ Bulk reabsorption
→ Surrounded by peritubular capillaries
→ Structure
- Cuboidal epithelial cells
- Dense microvilli (brush border)
- Rich in mitochondria for active transport
- Leaky epithelium
```
29
Loop of Henle
- Surrounded by?
- Function
- Structure
→ Surrounded by vasa recta (Juxtamedullary nephrons only)
→ Length is important in production of highly concentrated urine
→ Structure
- Descending limb: reabsorption of water from filtrate
- Thick (superior) section: similar to PCT
- Thin (inferior) section: simple squamous epithelium
- Ascending limb: reabsorption of NaCl from filtrate
- Thin (inferior) section: simple squamous epi
- Thick (superior) section: similar to DCT
30
Distal convoluted tube (DCT)
- Function
- Structure
- Specialised cells?
→ Fine tuning
→ Cuboidal epithelium (thinner than PCT)
→ Fewer mitochondria and microvilli (no brush border)
→ Macula dense cells located where DCT contacts afferent arteriole; chemoreceptors which detect Na+ conc.
31
Collecting duct
- Function (incl. what controls it)
- Structure (incl. cell types)
→ Fine tuning
→ Filtrate from several DCTs drains into one collecting duct, which empty at papilla
→ simple cuboidal epithelium
- Principal cells - reabsorption
- Intercalated cells - acid/base balance
→ Reabsorption influence by ADH, thr' use of aquaporins
32
Juxtaglomerular apparatus (JGA): where is it and what does it do?
→ Located where DCT lies against afferent arteriole
→ Controls glomerular filtration rate ensuring system working at full capacity
→ Stabilises blood pressure
33
Specialised cells and main role of the
- Afferent arteriole
- DCT
```
→ Afferent arteriole
- JG cells
- Mechanoreceptors
- Release renin in response to blood pressure, which stimulates angiotensin II formation
→ DCT
- Macula densa cells
- Chemo receptors
- Detect sodium concentration in filtrate
```
34
Ureters:
- Arise from?
- Descend where relative to the peritoneum?
- Motility pattern?
- Arise from each renal pelvis at each hilum
- Descend retroperitoneally through abdomen, vertically
- Peristaltic waves move urine → bladder
35
Layers of the Ureters and what they're made of
1) Mucosa - transitional epithelium, stratified
2) Muscularis - inner longitudinal, outer circular smooth muscle layer (opposite to GI tract, prevents backflow)
3) Adventitia - FCT
36
What motility pattern do the ureters use?
Peristalsis
37
What are the ureters lined with? What does it do?
- Protein plaques
| - For protection; stops urine from leaking
38
What is the significance of the way in which the ureters join connect to the bladder?
- Run obliquely through the wall of bladder at its posterolateral (side, back) corners
→ Act as sphincter/valve;
- compressed by increase bladder pressure to prevent back flow of urine
39
Urinary bladder
- What it is and what it does
- Structure when empty and when full
- How many openings?
- Contains what region?
- Collapsible, muscular sac, stores and expels urine
- When empty, collapses along rugae (folds)
- When full, expands w/out great ↑ in pressure
- 3 openings: 2 for entry of ureters, 1 for urethra
- Trigone: triangular region b/w openings; infections persist here
40
Position of bladder: Males vs Females
```
→ Male bladder
- Anterior to rectum
- Superior to prostate gland
→ Female bladder
- Anterior to vagina and uterus
```
41
What are the 3 layers of the bladder wall?
| What are they made up of?
1) Mucosa
- Transitional epithelium
2) Detrusor muscle
- Meshwork of longitudinal, circular & oblique smith muscle fibres (squeeze urine from bladder during urination - no motility pattern)
3) Adventitia
- Connective tissue
42
Urethra
- structure
- function
- Epithelium (incl. changes)
- Thin walled muscular tube
- Drains urine from bladder → out of body
→ Epithelium changes:
1) Transitional near bladder
2) Columnar (provides goblet cells → produce mucous)
3) Stratified squamous near external opening
43
Male vs Female urethra
```
→ Male
- Long
- Part of reproductive system
- Male urethra has 3 sections (due to length)
1) Prostatic urethra
2) Membranous urethra
3) Spongy/penile urethra
→ Female
- Short
- Separate from RS
```
44
Internal urethral sphincter features
- Junction of bladder and urethra
- Detrusor muscle (smooth)
- Involuntary control - parasympathetic innervation
45
External urethral sphincter features
- Where urethra passes through the urogenital diaphragm
- Skeletal muscle
- Voluntary control
46
Process of urination
Bladder expands → APs to brain → urgency → inner sphincter relaxes → conscious relaxation of external sphincters → urination
47
Urine composition - Normal
- 95-98% water (approx. 1.5L/day)
- Creatinine
- Urea
- H+, NH3
- Na+, K+
- Drugs (anti-viral, diuretics)
- Toxins
48
Urine composition - Pathogenic
- Glucose
- Protein
- Blood
- Haemoglobin
- Leucocytes
- Bacteria
49
What is normal Urine
- Look
- Taste
- Smell
```
→ Look
- Clear, light or dark amber
→ Taste
- Acidic (pH 5-7) - not sweet
↳ depends on diet
→ Smell
- None
```
50
What is pathogenic Urine
- Look
- Taste
- Smell
```
→ Look
- Golden red, brown, blue
→ Taste
- Sweet (diabetes)
→ Smell
- Like fruits (diabetes, ketosis, chronic alcohol abuse)
- Rotten (infection, tumour)
```
51
Functions of the kidneys (8)
1) Water and salt homeostasis
2) Filteration
3) Reabsorption
4) Hormone production (EPO)
5) Metabolism
6) Gluconeogenesis
8) Excretion drugs, endogenous metabolites & toxins (aspirin, anti-viral drugs, urea, uric acid, herbal toxins)
9) pH regulation
- Excrete excess HCO3-, H+
52
What are the basic nephron functions?
1) Filtration
2) Secretion
3) Re-absorption
53
How much of the cardiac output does the kidney receive?
20-25%
54
What does reabsorption do?
Which of the following are partially/completely reabsorbed:
- Na+ and K+
- glucose
- Removes useful solutes from the filtrate & returns them to blood
- Na+ and K+ partially reabsorbed
- glucose entirely reabsorbed
55
Function of basic nephron secretion
gets rid of substances that can't make it through the filtration barrier but need to be excreted in the urine
56
What defines renal filtration?
- Renal blood flow
- Filtration barrier
- Driving forces
57
Kidney filtration:
- Rate
- Produces what amount?
- Takes place at a rate of 125mL/min (180L/day)
| - Produces only 1.5 of urine/day
58
How is blood pressure monitored in the kidney?
DCT senses how much vol. is filtered and thus monitors BP
59
What is the rate of blood supply to the kidney?
1-1.2L/min
60
What substances are filtered by the glomerular?
| And not filtered?
- Small substances → freely filtered
| - Large substances → NOT filtered
61
What is Glomerular filtration influenced by?
1) Pressure gradient b/w glomerular capillary and Bowmans space
2) Permeability of glomerular capillary
3) SA of glomerular capillary
62
How do you calculate effective filtration pressure?
Effective filtration pressure = (glomerular hydrostatic pressure + capsular osmotic pressure) - (glomerular osmotic pressure + capsular hydrostatic pressure)
63
What are the glomerular driving forces?
→ Blood pressure (PGC) is the main driver for filtration
→ Forces opposing filtration are osmotic pressure in the glomerular capillary (πGC) and fluid pressure in Bowman capsule (PBS)
64
Blood vs. primary urine composition in terms of:
1. NaCl conc.
2. albumin conc.
- Both have NaCl conc. of 145mM (thus, isotonic primary filtrate)
- Blood contains 50g/L albumin, whereas urine contains none
65
What is renal clearance?
| How do you calculate it?
The RATE at which substances (that can be detected in plasma and urine) is CLEARED by the kidneys per unit time. (unit mL/min)
Clearance = conc. of substrate in urine x (vol. of urine produced/conc. of substrate in plasma)
66
Glomerular filtration rate (GFR):
- What is it?
- Normal value
- How can it be estimated?
- Amount of fluid filtered per unit time.// Vol. of plasma filtered per time.
- Normally 125mL/min
- Tightly regulated: variation b/w people; ↓ slowly from age 30
- Can be estimated using renal clearance
67
Which substances can be used as a measure of GFR?
Inulin and Creatinine
68
Inulin and Creatinine can be used as a measure of GFR bc they? (3 reasons)
1) Aren't reabsorbed from the tubule
2) Aren't secreted into the tubule
3) Aren't metabolised
69
What is more commonly used out of Inulin and creatinine? Why ?
Creatinine bc its already in the body and is only filtered, not reabsorbed
70
How does Creatinin conc. indicate kidney function?
- Plasma creatinin is low if both kidneys are working
| - Plasma creatinin fairly normal if only one is working
71
What is the filtration fraction?
FF = GFR/Renal Plasma Flow
| → ratio b/w blood flow and filtration in the kidney
72
What is the filtered load?
| How to calculate?
- Amount of a particular substance/solute filtered per minute.
- FL = GFR x Solute plasma conc.
73
Solutes which are only reabsorbed? (not secreted)
- Glucose
- Water
- Na+
- Cl-
- PO4-
- Ca2+
74
Solutes which are only secreted? (not reabsorbed)
```
Organic cations
- Monoamines
- Drugs
Organic anions
- Endogenous compounds (eg bile salts)
- Drugs (eg penicillin; 'PAH')
```
75
Where is PAH (organic anion) secreted?
| Active or passive?
Proximal tubules
| Active transport
76
What substances are both reabsorbed and filtered, depending on homeostatic requirements?
- K+
- NH3
- H+
- HCO3-
- Urea
77
What are the routes of transport?
1) Between cells - Paracellular
| 2) Through cells - Transcellular
78
Paracellular (between cells) features
- "leaky" = bulk reabsorption (PCT)
- Single barrier; permeability depends on 'tightness' of tight junction
- No transport proteins
79
Transcellular (through cells) features
- "tight" channels/energy
- More selective: hormonal control
- 2 barriers; apical (mucosal) and basolateral membrane
- usually involves membrane transport proteins
80
```
Proximal tubule:
- Function
- Reabsorbs what proportion of:
sodium, water, chloride, glucose, AAs, K+, PO43-, Ca2+, HCO3-, urea
- Secretes?
```
```
→ BULK reabsorption/secretion
- 66% sodium, water, chloride
- All filtered glucose & AAs
- Most of K+, PO43-, Ca2+
- 80% of filtered HCO3-
- 1/2 of urea
→ Secretes organic acids, drugs, H+
```
81
How does sodium reabsorption happen?
Transport of many solutes is coupled to Na+ reabsorption (glucose, AAs); Na+/K+ pump keeps [Na+] in cell low so this can keep occurring.
- 3 Na+ into interstitial, 2K+ into cell
82
Where does sodium reabsorption happen?
→ Occurs
- PCT (66%)
- TAL (25%)
- DCT (5%)
- CCT (3%)
83
PCT:
- what type of epithelium
- Permeability to water
- Which pathway(s)?
- Leaky epithelium
- High water permeability
- Transcellular (AQP1) and paracellular
84
CCT:
- what type of epithelium
- Permeability to water
- Which pathway(s)?
- Tight epithelium
- Low water permeability
- ONLY trancellular (AQP2)
85
Loop of Henle:
- Function of each section
- Effect on filtrate
→ Descending limb (tDLH): removes water from filtrate (leaky), impermeable to salt
→ Thick ascending limb (TAL): removes NaCl from filtrate (tight), impermeable to water; makes surrounding interstitial in medulla hyperosmotic - 'Hyperosmotic medullary gradient' (HOMG)
- Leaves filtrate inside tubules v. dilute
86
Distal tubule &collecting duct
- Function
- Hormonal control
→ Fine tuning of electrolytes, pH & water
- Reabsorb remaining NaCl & water
- Secrete K+ & H+
→ Hormonal control
- Na+ reabsorption/K+ secretion: aldosterone
- Water reabsorption: ADH
87
Body water volume?
```
TBW = 55-60% of body weight
→ 2/3 ICF
→ 1/3 ECF
- 1/5 plasma
- 4/5 interstitial fluid
```
88
What is osmolarity?
No. of ions or solutes per volume of water
| - e.g. 145mM NaCl = 145mM Na+ + 145mM Cl- = 290mosmol/L
89
What is
- ISO osmolarity
- HYPO osmolarity
- HYPER osmolarity
```
ISO = same
HYPO = lower
HYPER = higher
```
90
What is tonicity
Effect of a solution on cells
91
What proportion of water is reabsorbed in different parts of the nephron?
- PCT: 66%
- tDLH: 25%
- CCT: 2-8%
92
What is PCT driven by?
Na+ reabsorption (isotonic)
93
Urine tonicity through the nephron
- isotonic in PCT (300mosmol/L)
- hypertonic in tDLH
- hypotonic in TAL
- hypertonic in CCT (anti-diuresis)
94
Body osmolarity:
- Relative osmolarity of ECF and ICF (incl. value/s)
- How does dehydration and rehydration affect vol?
- Fluid shifts b/w ECF & ICF to equalise
→ Have the same osmolarity: 275-295mosmol/L
- Dehydration: water is lost only from ECF
- Hyperhydration: water is gained only by ECF
95
How does ADH regulate body osmolarity?
TBW alters plasma (ECF) osmolarity
1) detected by osmoreceptors in hypothalamus
2) Stimulates pituitary gland
3) ADH alters permeability of renal collecting duct (CD), so water is retained/excreted to balance initial TBW
4) Plasma osmolarity stable
5) Cell vol. stable
96
ADH synthesis; location and direction of travel
→ In cell body of central neurons (hypothalamus)
| → Axonal transport to posterior pituitary
97
ADH release; location and stimulus
- From posterior pituitary into bloodstream
→ Stimulated by:
- increase ECF osmolarity
- decrease blood volume
98
ADH actions/role:
1) Inserts water channels (aquaporins - AQP2) into luminal membrane of CD
2) Increase H2O reabsorption in the collecting duct
99
How is filtrate altered when ADH is present?
→ ANTI-DIURESIS
- Collecting duct more permeable to water; reabsorbed from CD
- Small vol. of concentrated (high osmolarity) urine
100
How is filtrate altered when ADH is absent?
→ DIURESIS
- Collecting duct impermeable to water; majority remains in CD
- Large vol. of dilute (low osmolarity) urine
101
Water homeostasis: Fast system
- Reacts to?
- Corrected by?
- Reacts to changes in osmolarity
| - ADH system
102
Water homeostasis: Slow system
- Reacts to?
- Corrected by?
- Affect of loss/gain of isosmotic solutions?
```
→ Reacts to changes in volume
→ corrected via sodium retention/excretion
→ Losses from ECF don't change osmolarity (bc isosmotic)
- no gradient change
- no movement of water in/out cells
- Thus, volume loss restricted to ECF
- circulating vol. ↓, BP ↓
→ gains of isosmotic solutions
- vol. gain restricted to ECF
- Circulating vol. ↑ & BP ↑
```
103
What 3 sensor mechanisms defect ΔECF vol. (in response to haemorrhage)
1) High pressure baroreceptors (aorta, carotid)
- pressure sensors
2) Low pressure baroreceptors (vena cava, right atrium)
- volume sensors
3) Intra-renal baroreceptors (kidney: JG cells in afferent arteriole and macula densa cells in distal tubule)
104
How do high pressure baroreceptors regulate pressure?
→ Signal to brainstem; CVS centres
→ Regulates via:
- Renal nerve activity (sympathetic)
- ADH
105
How do low pressure baroreceptors regulate pressure?
→ Signals to brainstem; CVS centres
→ If stimulated by high vol, atrial release of ANP (ANH)
- ANP promotes loss of sodium in the urine → promotes water excretion
106
How do Intra-renal sensors regulate pressure?
```
→ Afferent arteriole (mechanoreceptors)
- Senses changes in BP
- Alters renin secretion (JGA): renin stimulates angiotensin ll formation
→ Macula densa (chemoreceptors)
- Senses flow rate via Na+ conc in DT
- Alters renin secretion (JGA)
```
107
ECF vol. regulation Renin-Angiotensin System (RAs)
1) Renin (enzyme) secreted by JGA
2) Renin cleaves angiotensinogen into angiotensin l
3) Angiotensin l → angiotensin ll by angiotensin converting enzyme (ACE)
4) Angiotensin ll: vasoconstrictor (incr. TPR) and stimulates aldosterone release (incr. Na+ reabsorption)
108
Renal blood flow regulation?
1) Intrinsic (auto regulation)
- Myogenic vascular smooth muscle (afferent arteriole)
- Tubuloglomerular feedback (TGF): via JGA
2) Extrinsic
- Sympathetic vasoconstrictor nerves
- Angiotensin ll
109
Integration of systems @ HIGH circulating vol. & renal flow
- Mechanisms adjust to ↑ Na+ exretion
- Causes osmotic gradient → water loss
- ↓ vol. (BP)
110
Integration of systems @ LOW circulating vol. & renal flow
- Mechanisms activated to retain Na+
- Retain water
- Restore vol. (BP
111
ANP:
- Secreted by?
- In response to?
- Effects?
```
→ ANP secreted by atria in response to ↑ vol.; which:
- ↑ Filtered load of Na+
- ↓ Tubular reabsorption of Na+
- ↓ Renin secretion
therefore
- ↑ Na+ excretion
- ↑ water excretion
- ↓ vol. & BP
```
112
RAS: Stimuli for renin release from JGA when ECF vol. low
1) ↓ renal flow pressure in afferent arteriole
2) ↓ delivery of NaCl to macula densa (low vol. = low filtration = less in tubules)
3) Renal sympathetic nerves (activated by baroreceptors) each of these stimuli are activated when the body needs to conserve or restore vol.)
113
RAS: Effects to ↑ vol
- Stimulates reabsorption of Na+
- ↑ aldosterone secretion which also stimulates Na+ reabsorption
- Powerful vasoconstrictor (ATll): ↑ total peripheral resistance
- Hypothalamus: thirst, ADH release
114
Aldosterone:
- What is it
- Secreted from?
- Stimulated by?
- Acts on?
- Effect?
- Steroid hormone secreted from adrenal gland
- Stimulated by Angiotensin ll (& ↑ extracellular k+ levels)
- Acts on distal tubule & collecting duct; ↑ reabsorption of Na+ (& secretion of k+)
115
Isosmotic losses
- Diarrhea
- Vomiting
- Burns (bleeding)
116
Isosmotic gains
- Renal failure
| - Excess IV fluids
