11. Urinary System Flashcards
(140 cards)
1
Q
Give urinary system components
A
Two kidneys
Two ureters
One bladder
One urethra
2
Q
Name 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
What are electrolytes?
A
Electrolytes are charged atoms in solution (they conduct electricity)
4
Q
What is the optimum blood pH balance?
A
Blood pH must remain between 7.35-7.45 (mildly alkaline)
5
Q
What is calcitriol?
A
Active form of vitamin D
6
Q
What is erythropoietin?
A
Protein hormone that stimulates erythropoiesis in the red bone marrow
7
Q
What is the normal blood glucose level?
A
4-7 mmol/L
8
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
9
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
10
Q
Kidney: external layers
A
- Renal capsule (deep layer)
- Adipose capsule (middle layer)
- Renal fascia (outer layer)
11
Q
Kidney: internal regions
A
- Renal cortex: outer, light red area
- Renal medulla: darker area composed of several cone-shaped structures (renal pyramids)
12
Q
Minor calyces
A
These surround the renal papillae of each pyramid and collects urine from that pyramid
13
Q
Major calyces
A
Formed where several minor calyces converge
14
Q
Kidney blood supply
A
Renal artery
20-25% of cardiac output (despite kidney representing 0.5% of body weight!)
1.2L/min
Renal vein
drain deoxygenated blood to Inferior Vena Cava
15
Q
Nephron: definition
A
Functional unit of the kidney
More than 1 million per kidney
Single epithelial layer throughout
16
Q
Nephron: regions
A
Renal corpuscle
Renal tubule
17
Q
Nephron: anatomical labels to know
A
Glomerulus
Bowman’s capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
Afferent arteriole
Efferent arteriole
Peritubular capillaries
18
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
19
Q
Ureters: layers
A
- Inner mucous membrane
- Muscularis
- Adventitia
20
Q
Bladder: definition
A
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
21
Q
Trigone
A
Small, triangular area on posterior floor of bladder
Bordered by two ureteral openings and the urethral opening
22
Q
Bladder: layers
A
- Inner mucosa layer
- Muscularis (detrusor muscle)
- Adventitia
23
Q
Urethra
A
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
24
Q
Urethra: male
A
Around 20cm long
Divided into three sections:
- Prostatic
- Membranous
- Spongy
Passes through the prostate where it receives semen during ejaculation
25
Urine formation: processes
1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion
26
Blood constituents that CAN pass into the glomerular filtrate
Water
Mineral salts (electrolytes)
Amino acids
Glucose
Ketoacids
Hormones
Creatinine
Urea
Uric acid
Toxins
27
Blood constituents that CAN'T pass into the glomerular filtrate
Erythrocytes
Leukocytes
Platelets
Plasma proteins
28
Renal capsule
Deep layer of outer region of kidney
Smooth, transparent sheet of connective tissue
Maintains kidney shape
29
Adipose capsule
Middle layer of outer region of kidney
Mass of fatty tissue
Provides protection and support
30
Renal fascia
Outer layer of outer region of kidney
Thin layer of connective tissue
Anchors kidneys to surrounding structures and keeps them in place
31
Renal cortex
Superficial, light red area of the kidney
The renal corpuscle and both convoluted tubules (proximal and distal) lie in the renal cortex
This means that filtration of blood (in the renal corpuscle) occurs in the renal cortex
32
Renal medulla
Darker area of the inner region of the kidney
Composed of several cone-shaped structures (renal pyramids)
Contains Loop of Henle (part of renal tubules)
33
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
34
Where do the ureters enter the bladder?
Through the posterior wall
35
What prevents the backflow of urine?
A physiological valve
36
Ureter: Inner mucous membrane
Transitional epithelium which is able to stretch
Also contains goblet cells which secrete mucous
Provides protection from urine
37
Ureter: Muscularis
Smooth muscle fibres
Produces peristaltic contractions
38
Ureter: Adventitia
Outer coat of connective tissue
Contains blood and lymph vessels, nerves
39
Bladder: Inner mucosa layer
Transitional epithelium supported by connective tissue
The mucosa folds to permit expansion of the bladder
40
Bladder: Muscularis (detrusor muscle)
Middle layer of smooth muscle
At urethral opening, smooth muscle fibres accumulate and form the internal urethral sphincter (involuntary)
41
Bladder: Adventitia
Outer layer of connective tissue
42
What enables filtration to take place at the golmerular capillaries?
1. The diameter of the efferent arteriole is less than that of the afferent arteriole
2. Glomerular capillaries are ~50x leakier than normal capillaries
3. Glomerular capillaries have a large surface area
43
How is net pressure achieved in golmerular filtration?
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)
44
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
45
How is GFR calculated?
Through a blood test
46
What can the GFR test result determine?
The severity of kidney disease
47
What can affect the GFR?
Anything affecting the 3 filtration processes e.g. severe blood loss
48
What is colloid osmotic pressure?
Osmotic pressure exerted by plasma proteins e.g. albumin
49
What can affect colloid osmotic pressure?
Damage to the glomerular capillaries premitting plasma protein loss into urine (albuminuria)
50
What happens when albumin leaks from blood into the filtrate (urine)?
Blood volume decreases and interstitial fluid volume increases causing oedema (note: there are other causes of oedema)
51
Albuminuria
Albumin in urine
52
Where does most tubular reabsorption happen?
In the renal tubules and collecting ducts but mostly in the PCT
53
What substances are reabsorbed during tubular reabsorption?
Water (65% in PCT)
Amino acids
Glucose
Electrolytes
54
Which mode of transport is used when substances are reabsorbed during tubular reabsorption?
Active and passive
Substances pass into peritubular capillaries and return to general circulation
55
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
56
Which hormones are involved in kidney reabsorption?
```
Angiotensin II
Aldosterone
Antidiuretic hormone
Atrial natriuretic peptide
Parathyroid hormone
```
57
What is the Renin-Angiotensin-Aldosterone System (RAAS)?
A system of hormones that work together to increase blood pressure
58
What triggers the RAAS?
A systolic BP below 100mmHg
59
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
60
What does Angiotensin II do?
1. Triggers vasoconstriction which increases blood pressure
2. Triggers the pituitary gland to release ADH
3. Stimulates the adrenal cortex to produce aldosterone
61
What does Aldosterone do?
Increases renal sodium and water reabsorption which increases BP
62
What does Antidiuretic Hormone (ADH) do?
Increases the permeability of the DCT, increasing water reabsorption in the kidneys
63
What stimulates the secretion of ADH?
Osmoreceptor cells in the hypothalamus detect an increase in the osmolarity of the blood.
This triggers the release of ADH from the posterior pituitary gland.
| osmolarity = concentration of a solution
64
What does Atrial Natriuretic Peptide (ANP) do? How ?
Increases urine output and lowers BP
Inhibits the reabsorption of sodium and water in the renal tubules
65
What stimulates the secretion of ANP?
| From where?
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
66
Which hormones does ANP suppress?
ADH
Aldosterone
67
What does Parathyroid Hormone (PTH) do? How ?
| Where is it released from? In response to what?
Increases blood calcium levels by:
1. Stimulating renal reabsorption of calcium and magnesium
2. Increasing osteoclast activity
3. Stimulating release of calcitriol (which increases gut calcium absorption)
Released by the parathyroid gland in response to low blood calcium levels
68
Pathway of urine flow
Nephrons - papillary ducts of renal pyramids - minor/major calyces - renal pelvis - ureters - bladder-urethra
69
Urine composition
```
Water (96%)
Urea (2%), uric acid, creatinine
Ammonia
Sodium, Potassium, Phosphorus, Chloride, Sulphur
Hormones
Oxalates
```
70
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)
71
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
72
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 pelvic floor muscles
73
How much urine do we produce a day?
1-2 litres
74
What colour should urine be?
Yellow/amber coloured
75
What is the odour of urine?
Slightly aromatic
| Sweeter in diabetics
76
What is the pH of urine?
4.5-8 pH
| Average 6
77
# Urninary system homeostatic links with other systems:
Skin
Kidneys convert vit D precursor made in the skin into its active form, calcitriol
Uraemia can occur if urea accumulates due to kidney disease
78
# Urninary system homeostatic links with other systems:
Skeletal
The kidneys help adjust blood levels of calcium and phosphate
79
# Urninary system homeostatic links with other systems:
Muscular
Kidneys help to adjust blood calcium levels, required for muscle contraction
80
# Urninary system homeostatic links with other systems:
Nervous System
Kidneys can perform gluconeogenesis to provide glucose for neurons, especially during fasting or starvation
Kidneys regulate sodium and potassium levels via tubular secretion and reabsorption.
81
# Urninary system homeostatic links with other systems:
Endocrine
Kidneys produce calcitriol and erythropoietin
82
# Urninary system homeostatic links with other systems:
Lymphatic
Adjustment of water reabsorption affects the volume of interstitial fluid and lymph
Urine flushes out microbes
83
# Urninary system homeostatic links with other systems:
Respiratory
Lungs and kidneys work together to regulate pH of blood and all body tissues
84
# Urninary system homeostatic links with other systems:
Digestive
Calcitriol increases absorption of dietary calcium
85
# Urninary system homeostatic links with other systems:
Reproductive
In males, the urethra is the passageway for urine and semen
86
# Urninary system homeostatic links with other systems:
Cardiovascular
Kidneys can alter blood volume and pressure by adjusting water reabsorption (renin)
87
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)
88
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
89
Urinalysis: what can the dipstick test?
```
Leukocytes
Ketones
Nitrites
Urobilinogen
pH
Erythrocytes
Protein
Glucose
Specific gravity
```
90
Urinalysis: what can urine microscopy test?
```
Volume
Colour
Odour
pH
Leukocytes
Erythrocytes
Casts (clumps formed in nephrons)
Bacteria
Specific gravity
Microalbuminuria
```
91
What can leukocytes indicate in urinalysis?
UTI
92
What can ketones indicate in urinalysis?
Ketoacidosis (complication of diabetes mellitus) or ketone diet
93
What can nitrites indicate in urinalysis?
Bacteria
| UTI
94
What can urobilinogen indicate in urinalysis?
Liver pathology
95
What can erythrocytes indicate in urinalysis?
UTI
Tumour
Kidney stones
96
What can protein indicate in urinalysis?
Kidney disease
97
What can glucose indicate in urinalysis?
Diabetes mellitus
98
What can specific gravity indicate in urinalysis?
Dehydration
Glucosuria
Proteinuria
99
What can casts indicate in urinalysis?
| Casts - clumps of blood cells/bacteria that have formed in the nephron
Nephron disease
100
What can microalbuminuria indicate in urine microscopy?
Kidney disease
| (early indicator of Diabetic kidney)
101
What blood test parameters exist for the urinary system
```
Glomerular filtration rate (GFR)
Urea
Creatinine
Electrolytes
Inflammatory markers (ESR/CRP)
Leukocytes
```
102
Urinary system medical examinations
```
Ultrasound
Renal arteriography
X-rays
CT (ureteric obstruction)
MRI (malignancy)
Cystoscopy (bladder camera)
```
103
Dysuria
Painful, burning urination
104
Polyuria
Large quantity of urine
105
Oliguria
Little urine (<400ml/day)
106
Anuria
No urine
107
Proteinuria
Protein in urine
108
Bacteriuria
Bacteria in urine
109
Nocturia
Night-time urination
110
Haematuria
Blood in urine
111
Which metabolic wastes are excreted by the urinary system?
Urea,
Uric acid
Creatinine
(All contain nitrogen)
112
How are toxins excreted by the urinary system?
Medications and toxins are mostly detoxified in the liver and then excreted via the kidneys
113
Which electrolytes are regulated by the kidneys?
Sodium (Na+)
Potassium (K+)
Hydrogen (H+)
114
What can electrolytes form to regulate changes in pH?
Buffer substances
A buffer can bind with free H+ ions resisting increase in H+ avoiding increase in acidity
115
How much urine does a person need to pass a day to clear body waste
500ml/day
116
What can alter the water balance feedback mechanism?
Pathologies e.g. untreated diabetes mellitus
117
How is vitamin D synthesised?
UV light activates a vitamin D precursor in the skin
The kidneys convert inactive vitamin D into its active form - **Calcitriol**
118
What functions does calcitriol play?
Increases bone formation by :
1) Stimulating calcium and magnesium uptake from GIT.
2) Reducing calcium loss in kidneys
119
How is calcium uptake increased by calcitriol?
1. Stimulates calcium and magnesium uptake from GIT
2. Reduces calcium loss in kidneys (along with PTH)
120
What can a vitamin D deficiency cause?
Rickets
Osteomalacia
121
How is EPO secreted and under what conditions?
Secreted by kidney interstitial cells into the blood
Released in response to hypoxia (negative feedback)
122
What happens to EPO production in renal failure?
EPO production is inadequate and results in anaemia
123
How is EPO measured?
On blood EPO test
124
What is the renal threshold for glucose?
9 mmol/L
125
What happens if blood levels of glucose go above the renal threshold?
Glucose can't be reabsorbed from the nephrons into the blood when passing through the kidney tubules.
It is therefore present in the urine (glucosuria)
126
What is hyperglycaemia an indication of?
A pathology e.g. diabetes mellitus
127
How do kidneys elevate blood sugar levels when a person is hypoglycaemic?
Kidneys make glucose from glutamine (an amino acid)
Process is called gluconeogenesis
128
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/osmolarity
3. Regulating blood pressure by secreting the enzyme renin. This activates the Renin-Angiotensin-Aldosterone pathway (increased renin causes an increase in blood pressure)
129
What percentage of the cardiac output (blood) does the kidney receive?
20-25% (1.2L blood per min)
130
What role does the renal tubules play?
Involved in reabsorption and secretion of various solutes
131
How much fluid is in the bladder when the desire to urinate occurs?
200ml
132
What is the total capacity of the bladder?
600-700ml
133
Which unwanted substances are excreted by the urinary system?
**Metabolic Wastes**
* Urea: a metabolite of protein metabolism
* Uric acid: product of purine metabolism
* Creatinine: an end product of muscle metabolism
All contain nitrogen; the kidneys specialise in removing nitrogenous wastes.
**Ions**
In particular hydrogen (H+).
**Toxins**
Medications and toxins are mostly detoxified in the liver and then excreted via the kidneys.
134
How is blood pH balance maintained in the body ?
Blood pH must remain fairly constant between 7.**35** - 7.**45**
There are 2 primary pH control systems:
* Lungs: Excrete CO2 (the more CO2 in blood = more acidic)
* Kidneys: excrete H+ into urine and produce the buffer HCO3- (bicarbonate)
135
Which hormones are produced by the kidneys ?
Calcitrol
Erythropoietin
136
What is erythropoietin (EPO) ?
What does it stimulate ?
A protein hormone that stimulates erythropoiesis (red blood cell synthesis) in the red bone marrow.
137
Hilum
On the concave kidney border. The region where blood vessels, lymph vessels, nerves and ureters enter and exit the kidney.
138
Describe the structure of the renal corpuscle ?
Consists of glomerulus and Bowman’s capsule:
* The **glomerulus** is a tangled capillary network that receives blood from an afferent arteriole
* The **Bowman’s capsule** is a double-walled epithelial cup that surrounds the glomerulus, receiving contents of filtered blood
139
Describe the structure of the renal tubules
Consists of 3 sections:
1. Proximal convoluted tubule.
2. Loop of Henle.
3. Distal convoluted tubule.
* Filtered fluid is passed through the tubule.
* Important role in reabsorption and secretion of various solutes.
* Anti-Diuretic Hormone (ADH) acts on the distal convoluted tubule to reabsorb water.
140
What percentage of glomerular filtrate is reabsorbed by the renal tubules
99%
