11. Urinary System Flashcards
1
Q
Urinary system components
A
Two kidneys
Two ureters
One bladder
One urethra
2
Q
Urinary system functions
A
- Filter/excretion of unwanted substances
- Water/electrolyte balance
- Body fluid pH regulation
- Hormone production (EPO, calcitriol)
- Regulation of red blood cell production
- Regulation of blood glucose levels
- Regulation of blood pressure, volume, osmolarity
3
Q
Which substances are excreted by the urinary system?
A
- Metabolic wastes
- Ions
- Toxins
4
Q
How is water balance controlled by the urinary system?
A
Mainly controlled by kidneys
5
Q
What are electrolytes?
A
Electrolytes are charged atoms in solution (they conduct electricity)
6
Q
What is the optimum blood pH balance?
A
Blood pH must remain between 7.35-7.45 (mildly acidic)
7
Q
What is calcitriol?
A
Active form of vit D
8
Q
What is erythropoietin?
A
Protein hormone that stimulates erythropoiesis in the red bone marrow
9
Q
What is the normal blood glucose level?
A
4-7 mmol/L
10
Q
How does the amount of urine excreted affect blood volume, pressure, concentration?
A
More water excreted = lower BP
Less water excreted (more conserved in blood) = increased BP
11
Q
Kidney shape and location
A
Reddish, bean-shaped
Retroperitoneal (behind peritoneum)
Partially protected by 11th and 12th pairs of ribs between vertebral levels T11-L3
Right kidney is lower due to liver on same side
12
Q
Kidney: external layers
A
- Renal capsule (deep layer)
- Adipose capsule (middle layer)
- Renal fascia (outer layer)
13
Q
Kidney: internal regions
A
- Renal cortex
- Renal medulla
These make up the functional portion of the kidney
14
Q
Kidney: internal regions
A
- Renal cortex: outer, light red area
2. Renal medulla: darker area composed of several cone-shaped structures (renal pyramids)
15
Q
Minor calyces
A
These surround the renal papillae of each pyramid and collects urine from that pyramid
16
Q
Major calyces
A
These are formed where several minor calyces converge. From here, the urine flows into the renal pelvis; and from there, it flows into the ureter
17
Q
How is blood supplied to the kidneys?
A
Supplied through renal artery and vein
18
Q
Nephron: definition
A
Functional unit of the kidney
More than 1 million per kidney
Single epithelial layer throughout
19
Q
Nephron: regions
A
- Renal corpuscle
2. Renal tubule
20
Q
Glomerulus
A
Network of capillaries that receives blood from an afferent arteriole (one coming in)
Very leaky
21
Q
Bowman’s capsule
A
Double-walled epithelial cup that surrounds the glomerulus, receiving contents of filtered blood
22
Q
Nephron: full composition/anatomy
A
- Glomerulus (renal corpuscle)
- Bowman’s capsule (renal corpuscle)
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
- Afferent arteriole
- Efferent arteriole
- Peritubular capillaries
23
Q
Ureters: function and length
A
Two ureters transport urine from the renal pelvis to the bladder
Each ureter is around 25-30cm long and retroperitoneal
24
Q
Ureters: layers
A
- Inner mucous membrane
- Muscularis
- Adventitia
25
Bladder: definition
Hollow, muscular organ held in place by folds of peritoneum
Acts as a reservoir for urine
Becomes spherical as it accumulates urine
Collapses when empty
26
Trigone
Small, triangular area on posterior floor of bladder
| Bordered by two ureteral openings and the urethral opening
27
Bladder: layers
1. Inner mucosa layer
2. Muscularis (or detrusor muscle)
3. Adventitia
28
Urethra
Tube leading from the bladder to the exterior of the body
Between the internal urethral sphincter (involuntary) and the external urethral sphincter (voluntary)
Female urethra = 4cm
Male urethra = 20cm
29
Urethra: male
Around 20cm long
Divided into three sections:
1. Prostatic
2. Membranous
3. Spongy
Passes through the prostate where it receives semen during ejaculation
30
Urine formation: processes
1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion
31
Golmerular filtration
Water and small molecules pass through pores in the golmerular capillaries into the Bowman's capsule
Blood cells, plasma proteins and other large molecules cannot filter through because of the size of the pores (think of a sieve). They reside in the blood
32
Blood constituents that CAN pass into the glomerular filtrate
```
Water
Mineral salts (electrolytes)
Amino acids
Glucose (but only if gone over the 9 mmol/L)
Ketoacids
Hormones
Creatinine
Urea
Uric acid
Toxins
```
33
Blood constituents that CAN'T pass into the glomerular filtrate
Erythrocytes
Leukocytes
Platelets
Plasma proteins
34
Renal capsule
Deep layer of outer region of kidney
Smooth, transparent sheet of connective tissue
Maintains kidney shape
35
Adipose capsule
Middle layer of outer region of kidney
Mass of fatty tissue
Provides protection and support
36
Renal fascia
Outer layer of outer region of kidney
Thin layer of connective tissue
Anchors kidneys to surrounding structures and keeps them in place
37
Renal cortex
Outer, light red area of the inner region of the kidney
| Contains renal corpuscle (glomerulus and Bowman's capsule) and proximal/distal convoluted tubules
38
Renal medulla
Darker area of the inner region of the kidney composed of several cone-shaped structures (renal pyramids) and Loop of Henle
39
What does the renal corpuscle consist of?
Consists of glomerulus and Bowman's capsule
40
What does the renal tubule consist of?
Consists of:
a) proximal convoluted tubule (PCT)
b) Loop of Henle
c) distal convoluted tubule (DCT)
41
How does urine get from the kidneys to the bladder?
Peristaltic contractions of the ureters' muscular walls propel urine towards bladder
Aided by gravity and pressure of urine
1-5 waves per min
42
Where do the ureters enter the bladder?
Through the posterior wall
43
What prevents the backflow of urine?
A physiological valve
44
Ureter: Inner mucous membrane
Transitional epithelium which is able to stretch
Also contains goblet cells which secrete mucous
Provides protection from urine
45
Ureter: Muscularis
Smooth muscle fibres
Produces peristaltic contractions
46
Ureter: Adventitia
Outer coat of connective tissue
Contains blood and lymph vessels, nerves
47
Bladder: Inner mucosa layer
Transitional epithelium supported by connective tissue
The mucosa folds to permit expansion of the bladder
48
Bladder: Muscularis (or detrusor muscle)
Middle layer of smooth muscle
At urethral opening, smooth muscle fibres accumulate and form the internal urethral sphincter (involuntary)
49
Bladder: Adventitia
Outer layer of connective tissue
50
How do the golmerular capillaries make filtration happen?
1. The diameter of the efferent arteriole is less than that of the afferent arteriole
2. Glomerular capillaries are c50x leakier than normal capillaries
3. Glomerular capillaries have a large surface area
51
What is needed for golmerular filtration to happen?
1. Blood pressure forces substances through the membrane
2. Proteins present in blood plasma within the glomerular capillaries oppose filtration (colloid osmotic pressure)
3. Back pressure of the fluid that's already filtered opposes filtration (capsular hydrostatic pressure)
52
What is the glomerular filtration rate (GFR)?
The amount of filtrate formed in the renal corpuscles of both kidneys each minute
Normal GFR should be over 90ml/min
GFR males = 125ml/min
GFR females = 105ml/min
53
How is GFR calculated?
Through a blood test
54
What can the GFR test result determine?
The severity of kidney disease
55
What can affect the GFR?
Anything affecting the 3 filtration processes e.g. severe blood loss
56
What is colloid osmotic pressure?
A form of osmotic pressure exerted by plasma proteins e.g. albumin
57
What can affect colloid osmotic pressure?
Damage to the glomerular capillaries can lead to plasma protein loss into urine
58
What happens when albumin leaks from blood into the filtrate (urine)?
Blood volume decreases and interstitial fluid volume increases causing oedema (there are other causes of oedema)
59
Albuminuria
Albumin in urine
60
Where does most tubular reabsorption happen?
In the renal tubules and collecting ducts but mostly in the PCT
61
What substances are reabsorbed during tubular reabsorption?
Water (65% in PCT)
Amino acids
Glucose
Electrolytes
62
Which mode of transport is used when substances are reabsorbed during tubular reabsorption?
Active and passive
They pass into nearby blood vessels and return to general circulation
63
What substances are secreted into the urine during tubular secretion?
Waste products - creatinine, ammonium ions, urea
Certain drugs e.g. penicillin
Excess ions e.g. H+ for pH regulation
64
Which hormones are involved in kidney reabsorption?
```
Angiotensin II
Aldosterone
Antidiuretic hormone
Atrial natriuretic peptide
Parathyroid hormone
```
65
What is the Renin-Angiotensin-Aldosterone System (RAAS)?
A system of hormones that work together to increase blood pressure
66
What triggers the RAAS?
A systolic BP below 100mmHg
67
What happens when the RAAS is triggered?
1. The enzyme renin is released by the kidneys into the blood
2. Angiotensinogen (inactive) gets converted to angiotensin I in the liver
3. Angiotensin I is converted to angiotensin II by the angiotensin-converting enzyme (ACE) in the lungs
4. Angiotensin II causes release of aldosterone from the adrenal cortex
68
Angiotensin II
1. Triggers vasoconstriction which increases blood pressure
2. Triggers the pituitary gland to release ADH
3. Stimulates the adrenal cortex to produce aldosterone
69
Aldosterone
Increases renal sodium and water reabsorption which increases BP
70
Antidiuretic Hormone (ADH)
Increases the permeability of the DCT, increasing water reabsorption in the kidneys
71
What stimulates the secretion of ADH?
Reduced water concentration in the blood, and lowered blood volume, causes increased blood osmotic pressure
Osmoreceptors in the hypothalamus stimulate the posterior pituitary gland to secrete ADH
72
Atrial Natriuretic Peptide (ANP)
Inhibits the reabsorption of sodium and water in the renal tubules
Increases urine output and lowers BP
73
What stimulates the secretion of ANP?
A large increase in blood volume promotes the release of ANP from the heart
It's released from the myocardium in response to atrial stretch
74
Which hormones does ANP suppress?
ADH
| Aldosterone
75
Parathyroid Hormone (PTH)
Released by the parathyroid gland in response to low blood calcium levels
Increases blood calcium levels by:
1. Stimulating renal reabsorption of calcium and magnesium
2. Increasing osteoclast activity
3. Stimulating release of calcitriol (increases gut calcium absorption)
76
Urine flow
Nephrons - papillary ducts of renal pyramids - minor/major calyces - renal pelvis - ureters - bladder
77
Urine composition
```
Water (96%)
Urea (2%), uric acid, creatinine
Ammonia
Sodium, Potassium, Phosphorus, Sulphur
Hormones
Oxalates (rhubarb, spinach, beetroot)
```
78
What stimulates the micturition process
When the volume in the bladder exceeds 200-400ml, stretch receptors in the bladder wall transmit nerve impulses to the spinal cord (S2 and S3)
79
Micturition process: infants
Increase in bladder volume generates a micturition reflex leading to contraction of the detrusor muscle and relaxation of the internal AND external urethral sphincters
80
Micturition process: adults
Nervous system matures and consciously inhibits the reflex contraction of the bladder and relaxation of the internal urethral sphincter
Adults can control the external urethral sphincter and pelvis floor muscles
81
When do we learn to initiate and stop micturition voluntarily?
In early childhood
82
How much urine do we produce a day?
1-2 litres
83
What colour should urine be?
Yellow/amber coloured
84
What is the odour of urine?
Slightly aromatic
| Sweeter in diabetics
85
What is the pH of urine?
4.5-8 pH
| Average 6
86
Homeostasis: Skin
Kidneys convert vit D precursor made in the skin into its active form, calcitriol
87
Homeostasis: Skeletal
The kidneys help adjust blood levels of calcium and phosphate
88
Homeostasis: Muscular
Kidneys help to adjust blood calcium levels, required for muscle contraction
89
Homeostasis: Nervous System
Kidneys can perform gluconeogenesis to provide glucose for neurons, especially during fasting or starvation
90
Homeostasis: Endocrine
Kidneys produce calcitriol and EPO
91
Homeostasis: Lymphatic
Adjustment of water reabsorption affects the volume of interstitial fluid and lymph
Urine flushes out microbes
92
Homeostasis: Respiratory
Lungs and kidneys help adjust pH of body fluids
93
Homeostasis: Digestive
Calcitriol increases absorption of dietary calcium
94
Homeostasis: Reproductive
In males, the urethra is the passageway for urine and semen
95
Homeostasis: Cardiovascular
Kidneys can alter blood volume and pressure by adjusting water reabsorption (renin)
96
Signs/symptoms of urinary tract pathology
1. Frequent, urgent and painful urination
2. Red urine (blood or beetroot?)
3. Pain in loin (lower back)
4. High urine volume with great thirst
5. Low or no urine volume
6. Nausea and vomiting
7. Oedema (loss of albumin)
8. Exhaustion (anaemia, blood loss into urine)
97
Signs/symptoms of renal disease
1. Pallor (due to anaemia)
2. Frothy urine (due to proteinuria)
3. Oedema (due to plasma protein loss)
4. Itchy skin (due to uraemia)
5. Altered mental state (common with UTIs)
6. Puffy face/bags under eyes
7. Dehydration
8. Flapping tremor
98
Urinalysis: what can the dipstick test?
```
Leukocytes
Ketones
Nitrites
Urobilinogen
pH
Erythrocytes
Protein
Glucose
Specific gravity
```
99
Urinalysis: what can urine microscopy test?
```
Volume
Colour
Odour
pH
Leukocytes
Erythrocytes
Casts (clumps formed in nephrons)
Bacteria
Specific gravity
Microalbuminuria
```
100
What can leukocytes indicate in urinalysis?
UTI
101
What can ketones indicate in urinalysis?
Ketoacidosis (complication of diabetes mellitus) or ketone diet
102
What can nitrites indicate in urinalysis?
Bacteria
| UTI
103
What can urobilinogen indicate in urinalysis?
Liver pathology
104
What can erythrocytes indicate in urinalysis?
UTI
Tumour
Kidney stones
105
What can protein indicate in urinalysis?
Kidney disease
106
What can glucose indicate in urinalysis?
Diabetes mellitus
107
What can specific gravity indicate in urinalysis?
Dehydration
Glucosuria
Proteinuria
108
What can casts indicate in urinalysis?
Nephron disease
109
What can microalbuminuria indicate in urinalysis?
Kidney disease
110
Urinary system blood test parameters
```
Glomerular filtration rate (GFR)
Urea
Creatinine
Electrolytes
Inflammatory markers (ESR/CRP)
Leukocytes
```
111
Urinary system medical examinations
```
Ultrasound
Renal arteriography
X-rays
CT (ureteric obstruction)
MRI (malignancy)
Cystoscopy (bladder camera)
```
112
Dysuria
Painful, burning urination
113
Polyuria
Large quantity of urine
114
Oliguria
Little urine (<400ml/day)
115
Anuria
No urine
116
Proteinuria
Protein in urine
117
Bacteriuria
Bacteria in urine
118
Nocturia
Night-time urination
119
Haematuria
Blood in urine
120
Which metabolic wastes are excreted by the urinary system?
Urea,
Uric acid
Creatinine
(All contain nitrogen)
121
Which ion is excreted by the urinary system?
Hydrogen (H+)
122
How are toxins excreted by the urinary system?
Medications and toxins are mostly detoxified in the liver and then excreted via the kidneys
123
Which electrolytes are regulated by the kidneys?
Sodium
Potassium
Hydrogen
124
What can electrolytes form to regulate changes in pH?
Buffer substances
125
How much urine does a person need to pass a day to clear body waste
500ml/day
126
What can alter the water balance feedback mechanism?
Pathologies e.g. untreated diabetes mellitus
127
What are the two primary pH control systems?
1. Lungs: excrete CO2
| 2. Kidneys: excrete H+ into urine and produce bicarbonate buffer
128
How is vit D synthesised?
UV light activates a vit D precursor in the skin
The kidneys convert inactive vit D into its active form
129
What functions does calcitriol play?
Increases bone formation by increasing blood calcium levels
130
How is calcium uptake increased by calcitriol?
1. Stimulates calcium and magnesium uptake from GIT
| 2. Reduces calcium loss in kidneys (along with PTH)
131
What can a vit D deficiency cause?
Rickets
| Osteomalacia
132
How is EPO secreted and under what conditions?
Secreted by kidney interstitial cells into the blood
Released in response to hypoxia (negative feedback)
133
What happens to EPO production in renal failure?
EPO production is inadequate and results in anaemia
134
How is EPO measured?
On blood EPO test
135
What is the renal threshold for glucose?
9 mmol/L
136
What happens if blood levels go above the renal threshold?
Glucose can't be reabsorbed from the nephrons into the blood when passing through the kidney tubules
137
What is hyperglycaemia an indication of?
A pathology e.g. diabetes mellitus
138
How do kidneys elevate blood sugar levels when a person is hypoglycaemic?
Kidneys make glucose from glutamine (an amino acid)
Process is called gluconeogenesis
139
How is blood volume/pressure/concentration regulated by the kidneys?
1. Conserving or eliminating water in urine
2. Regulating loss of solute in the urine which helps to maintain a constant blood concentration/osmolality
3. Regulating blood pressure by secreting the enzyme renin. This activates the Renin-Angiotensin-Aldosterone pathway (increased renin causes an increase in blood pressure)
140
What percentage of the cardiac output (blood) does the kidney receive?
20-25% (1.2L blood per min)
141
What role does the renal tubules play?
Involved in reabsorption and secretion of various solutes
142
How much fluid is in the bladder when the desire to urinate occurs?
200ml
143
What is the total capacity of the bladder?
600-700ml
