Urinary System Flashcards
List the 4 key anatomical components in the urinary system
2 kidneys, 2 ureters, bladder, urethra
Which body cavity are the kidneys situated in?
The abdominal cavity, below the diaphragm and behind the stomach.
Which fluid do the kidneys filter?
The blood
The urinary system (and kidneys) are one of our main systems of elimination. True or false?
True
Where is urine formed?
In the kidneys
Describe the ureters
Muscular tubes that extend from the kidneys, down the back of the abdomen. They enter the posterior part of the bladder.
Which part of the bladder do the ureters enter?
The posterior (back) part of the bladder
Describe the bladder
A muscular chamber that acts as a reservoir to contain urine, before it is expelled via muscular contraction down the urethra.
Describe the differences between the ureters and the urethra
We have 2 ureters and 1 urethra
What is the difference between the male and female urethra?
The urethra is significantly shorter (around 5 x shorter) in women than in men.
Why are women far more susceptible to urinary tract infections than men?
Because their urethra is significantly shorter than in males. The urethra connects the bladder with the outside world, so if the urethra is very short, bacteria from the outside have a very short distance to travel to get in to the bladder and cause an infection.
List some functions of the urinary system
- Excretion of unwanted substances (waste)
- Maintainance of water & electrolyte balance
- pH regulation of body fluids (especially blood)
- Regulation of blood glucose levels
- Regulation of blood pressure, volume and osmolarity
- Production of hormones (erythropoietin & calcitriol)
- Regulation of erythrocyte production
Name 2 hormones produced in the kidneys
Erythropoietin (production of red blood cells) and calcitriol (the active form of vitamin D)
What does ‘osmolarity’ mean?
The concentration of a solution
What is calcitriol?
The active form of vitamin D
What is the role of calcitriol?
It helps to absorb calcium from our foods and move it into the blood.
What role do the kidneys play in the production of red blood cells?
They detect hypoxia (lack of oxygen in the blood) and release erythropoietin, a hormone which instructs the bone marrow to start creating more red blood cells.
(The more erythrocytes you have, the more capacity you have to transport oxygen around your body).
How do the kidneys help to regulate blood pressure?
- They help to excrete excess water from the blood.
2. They help to conserve water when we’re dehydrated
What happens to blood volume when we excrete excess water in our urine? What effect does this have on blood pressure?
Blood volume lowers, therefore blood pressure lowers.
List the 3 main types of metabolic wastes excreted by the kidneys.
What do they all have in common?
- Urea
- Uric acid
- Creatinine
They all contain Nitrogen and they all have some relationship to proteins
What is urea?
A metabolite / by-product of protein metabolism
What is Uric acid?
A metabolite / by-product of purine metabolism
What is creatinine?
An end/by-product of muscle metabolism of creatine phosphate
What do urea, uric acid and creatinine all have in common?
They are all metabolic wastes, they all contain nitrogen, they all have some relationship to proteins.
What are purines? What do they create when metabolised?
A type of protein found in shellfish, game, red meats, etc. They create uric acid.
In gout, which type of metabolic waste accumulates in joints, causing pain and inflammation?
Uric acid
Why can gout sometimes be traced back to kidney disease?
Because kidney disease often means that the kidneys are not removing/excreting uric acid (the main cause of gout) from the body as effectively as they should be.
List 4 things that the kidneys excrete in urine.
- Metabolic wastes (urea, uric acid, creatinine)
- Ions (particularly hydrogen)
- Toxins (including medications)
- Hormones
Why are the kidneys relevant when it comes to removing excess acid from the body?
They excrete excess hydrogen, which is acid forming.
How do the liver and kidneys work together to excrete toxins from the body?
The liver detoxifies the toxins and then the kidneys excrete them.
The body’s water balance is mainly controlled by which organs?
The kidneys
What is the minimum quantity of urine required to clear body waste each day?
500ml per day
What happens to waste products that are not excreted through the urine efficiently?
We start to reabsorb them (not good!)
Name a condition / pathology that disrupts blood volume and causes the patient to drink lots of water / be thirsty.
Diabetes Mellitus
What are electrolytes?
Charged atoms that are in solution
List the 3 most important electrolytes regulated by the kidneys
Sodium, Potassium, Hydrogen
Na+, K+, H+
When might the taking of electrolytes be useful?
When exercising / doing sport, or for recovery from diarrhoea.
Sodium always travels with….
where one goes, the other will follow
Water
What is a buffer?
A substance that helps to neutralise any acidity / regulate changes in pH.
Which buffer do the kidneys predominately produce?
Bicarbonate
What 2 steps can the kidneys take to reduce excess acidity in the blood?
- Excrete excess hydrogen ions (acid forming) in the urine.
2. Produce bicarbonate as an acidity buffer
Blood pH level must remain fairly constant between…
7.35 - 7.45 pH
Which 2 body organs primarily manage blood pH control, and how?
Lungs - excrete CO2
Kidneys - excrete H+ (hydrogen) into urine and produce the buffer HCO3- (bicarbonate)
Which 2 body fluids can reliably measure blood pH?
Urine and saliva
What is the effect of excess CO2 on the blood?
It makes it acidic
What activates the vitamin D precursor in the skin?
UV rays
Which organ converts inactive vitamin D into its active form?
The kidneys
Why do we need calcitriol?
To make sure we’re absorbing all of the calcium from our foods.
Calcitriol stimulates calcium and magnesium uptake from the GIT, and reduces calcium loss in the kidneys (stops them excreting calcium).
Name 2 pathologies that a deficiency in calcitriol can cause.
Osteomalacia & rickets
What is erythropoietin (EPO)?
A protein hormone, produces in the kidneys, that stimulates erythropoiesis in the red bone marrow.
In kidney failure, erythropoietin production can be inadequate. Which pathology could this lead to?
Anaemia
Erythropoietin is released by the _____ in response to _____
Kidneys, hypoxia
How are erythropoietin levels measured?
Via blood test (EPO test)
What is the renal threshold for glucose?
9 mmol/L
What is a normal blood glucose level?
4-7 mol/L
What is the problem with high blood glucose?
It is damaging to blood vessels
Which pathology might be indicated by hyperglycaemia / glucose in the urine?
Diabetes Mellitus
How can the kidneys help us if we’re in a state of hypoglycaemia?
They are able to make glucose from the amino acid glutamine to help elevate blood sugar levels when needed.
From which amino acid can the kidneys make glucose?
Glutamine
What is gluconeogenesis?
The formation / production of glucose.
Which enzyme do the kidneys secrete to help regulate blood pressure?
Renin
An increase in the enzyme renin, has what effect on blood pressure?
Increased renin = increased blood pressure
What does retro-peritoneal mean?
Behind the peritoneum
What shape are the kidneys?
Bean-shaped
Which ribs partially protect the kidneys?
T11, T12
Why is the right kidney lower than the left?
Because the liver occupies considerable space on the right, superior to the kidney.
Name the 2 layers within the kidney
Outer cortex, inner medulla
Each kidney sits in the posterior abdomen and is surrounded by 3 layers (deep, middle and superficial layers). Name these layers.
- Renal capsule
- Adipose tissue
- Renal fascia
What is the renal capsule?
A smooth, transparent sheet of connective tissue, which maintains the kidney shape.
What is the role of the adipose capsule around the kidney?
Fatty tissue, providing physical protection and support.
What is renal fascia?
A thin layer of connective tissue that anchors the kidneys to surrounding structures, against the abdominal wall.
Where would you find the renal pyramids? What shape are they?
Within the renal medulla in the kidney.
Cone-shaped
The apex of each renal pyramid is called ______?
Renal papilla
What is the significance of the renal papilla?
It is the location in the kidney where the urine passed through into the minor and major calyces
What are the functional units of the kidney called?
Nephrons
Urine formed by the kidney nephron drains into the ________ and ________ ___________
Minor and major calyces
How many nephrons do we have per kidney?
Around 1 million
What is significant about the kidney nephrons?
The nephrons are where urine is created
Where in the kidneys would you find nephrons?
Distributed throughout the renal cortex (‘bark’) and renal pyramids
Which blood vessels supply the kidneys?
Renal vein and renal artery
Where is the hilum, and what is it?
On the concave (inner) kidney border. It is the region where everything (blood vessels, lymph vessels, nerves and ureters) enters and exits the kidney.
How much of the cardiac output goes straight to the kidneys via the renal artery?
20 - 25% (approx 1.2 litres of blood per minute)
This indicates just how important the kidneys’ job is in filtering the blood.
What is the functional unit of the kidney?
Nephron
Name the 2 parts of a nephron
- Renal Corpuscle (glomerulus & Bowman’s capsule)
2. Renal Tubule (consists of 3 sections)
Name the 2 parts of the renal corpuscle
Glomerulus & Bowman’s capsule
What is the glomerulus?
A tangled capillary network within the kidney nephron that receives blood from the afferent arteriole.
What structure surrounds the glomerulus in a kidney nephron, and recieves contents of filtered blood?
The Bowman’s Capsule
Why is the glomerulus around 50 times leakier/more permeable than the average capillary?
To further encourage substance exchange / filtration in the kidney
Name the 3 regions of the renal tubule (within a kidney nephron).
- Proximal convoluted tubule (reabsorb about 65% of water here)
- Loop of Henle
- Distal convoluted tubule
Which hormone acts on the distal convoluted tubule in the kidney nephron, to reabsorb water?
ADH (Anti-diuretic hormone)
The 2 ureters transport urine from the ________ to the _______
Renal pelvis, bladder
What propels urine towards the bladder?
Peristaltic contractions of the ureters muscular walls (aided by gravity and pressure of the urine itself)
What prevents back flow of urine from the bladder, back up the ureters?
A physiological valve
Why shouldn’t we get bacteria entering and colonising in the urinary system / tract (in theory)?
Because it’s a sterile system.
How many layers of tissue form the wall of the ureters?
3
What is a lumen?
The inside of a tube / vessel
List the 3 layers of tissue that form the wall of the ureters.
- Inner mucous membrane
- Muscularis
- Adventitia
What is the main characteristic of transitional epithelium?
It is able to stretch
Why does the inner mucous membrane of the ureters have goblet cells that secrete mucous?
To protect the epithelial lining of the ureters from the harsh/acidic/toxic urine.
What is the function of the muscularis layer of the ureters?
It consists of smooth muscle fibres, which produce peristaltic contractions to push the urine downwards towards the bladder.
Which of the 3 layers of tissue forming the walls of the ureters consists of connective tissue, containing blood, lymph vessels and nerves?
The adventitia
What is the urinary bladder?
A hollow, muscular organ that acts as a reservoir for urine.
What holds the bladder in position?
Folds in the peritoneum
What sits just below the bladder in males?
The prostate gland.
The urinary bladder is composed of 3 layers of tissue. Name them.
- Inner mucosa layer
- Muscularis
- Adventitia
What is the name of the smooth muscle in the bladder?
Detrusor
What is the name of the involuntary sphincter at the bottom of the bladder, at the urethral opening?
Internal Urethral Sphincter
Which is under voluntary control (over 5yrs of age) - the internal urethral sphincter, the the external urethral sphincter?
The external urethral sphincter
What is bladder cancer most associated with?
Smoking cigarettes (both active and passive smoking)
What is the name of the tube leading from the bladder to the exterior of the body, and what does it do?
The urethra. It is a passageway for discharging urine.
Which gland does the male urethra pass through?
The prostate gland
Name the triangular area in the posterior bladder wall
Trigone
Which muscle forms the internal urethral sphincter?
Detrusor
What is the average length of the male and female urethras?
Female = 4cm Male = 20cm
Name the smooth muscle found in the bladder wall.
Detrusor
To produce urine, how many basic processes do the nephrons and collecting ducts perform?
3
Name the 3 basic processes performed by the nephrons and collecting ducts, to produce urine.
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
Where does glomerular filtration occur?
In the renal corpuscle
Where does tubular reabsorption occur?
In the renal tubules
Where does tubular secretion occur?
In the renal tubules
List 2 ways in which the glomerulus is perfectly designed to filter the blood as effectively as possible
- Glomerular capillaries = a large, tangled surface area for filtration.
- Glomerular capillaries are around 50 times more leaky than average capillaries, allowing more exchange of substances.
- The efferent (outgoing) arteriole is very narrow, compared to the afferent (incoming) arteriole. Therefore, the blood pressure in the glomerular capillaries is high.
What substances pass through pores in the glomerular capillaries into the Bowman’s capsule?
Water and small molecules
What is the name of the blood vessel that carries blood into the glomerulus?
Afferent arteriole
List 3 things that are unable to filter through the glomerular capillaries into the Bowman’s Capsule.
Why can’t they filter through?
Blood cells, plasma proteins, large molecules
They’re too big to fit through the pores in the glomerular capillaries.
List some blood constituents that pass through the glomerular capillaries and into the glomerular filtrate.
Water Mineral salts (electrolytes) Amino Acids Glucose Hormones Creatinine Urea Uric acid Toxins
List 4 blood constituents that cannot pass through into glomerular filtrate, so remain in the glomerular capillaries (and therefore the blood).
Leukocytes
Erythrocytes
Platelets
Plasma Proteins
What is the glomerular filtration rate (GFR)?
The amount of filtrate formed in the renal corpuscles of both kidneys each minute.
How is GFR calculated?
Through a blood test. It is part of a normal kidney function test.
What does GFR stand for?
Glomerular filtration rate
What should a normal average GFR be?
Over 90mls/minute
What could a low GFR indicate?
Kidney disease
What is colloid osmotic pressure?
A form of osmotic pressure exerted by proteins (notably albumin)
What can lead to lower blood albumin levels, and albumin in the urine?
Damage to glomerular capillaries, allowing larger molecules and plasma proteins such as albumin to leak through into glomerular filtrate.
What can cause frothy urine?
Plasma proteins leaking into the urine from the kidneys.
What percentage of glomerular filtrate is reabsorbed into the bloodstream along the renal tubules and collecting ducts (tubular reabsorption)?
99%
List 3 things that are pulled from glomerular filtrate back into the blood during tubular reabsorption.
Water
Amino acids
Glucose
Electrolytes
In tubular reabsorption, where does most of the actual reabsorption occur?
In the PCT (proximal convoluted tubule)
List 5 hormones that have an influence on the kidneys (affecting renal reabsorption of sodium, chloride, calcium and water, and the secretion of potassium)
Angiotensin II Aldosterone Antidiuretic hormone Atrial Natriuretic peptide Parathyroid hormone
What does ‘angio’ mean?
Vessel (any). NOT the heart.
What does the hormone Angiotensin II cause?
Vasoconstriction
What do aldosterone and Antidiuretic hormone (ADH) have in common?
Both work on the kidneys, and cause the kidneys to reabsorb water. So both have the effect of increasing blood pressure.
Which 3 kidney-related hormones increase blood pressure?
Angiotensin II, Aldosterone and Antidiuretic hormone
What does atrial natriuretic peptide (hormone) do?
Acts on the kidneys to lower blood pressure
What does parathyroid hormone do?
Elevates / increases blood calcium levels by a) telling the kidneys to reabsorb calcium that is due to be excreted and b) release calcitriol.
What 2 things do the kidneys do in response to the release of parathyroid hormone?
- Reabsorb calcium
2. Release calcitriol (vitamin D)
What is calcitriol and what is it released by?
Calcitriol is the active form of Vitamin D, released by the kidneys
What is the RAAS and what does it do?
The RAAS is a system of hormones that work together to increase blood pressure.
What does RAAS stand for?
Renin-Angiotensin-Aldosterone System
What is renin?
An enzyme
Which 4 organs are involved in the Renin-Angiotensin-Aldosterone System (RASS)?
- Kidneys (release renin enzyme)
- Liver (converts Angiotensinogen into Angiotensin I)
- Lungs (converts Angiotensin I into Angiotensin II)
- Adrenal cortex (releases Aldosterone)
Where is the hormone aldosterone released from?
Adrenal cortex
What does the ACE enzyme do, and where is it found?
Converts Angiotensin I into Angiotensin II.
In the lungs
(ACE = Angiotensin Converting Enzyme)
Where is the hormone Angiotensin II formed?
In the lungs
Which organ detects a drop in blood pressure?
Kidneys
Which organs do the adrenal glands sit on top of?
The kidneys
List 3 actions of the hormone Angiotensin II.
It raises blood pressure, by causing:
- Vasoconstriction
- Release of Aldosterone from the adrenal cortex
- Release of ADH (Anti Diuretic Hormone) from the posterior pituitary.
What does Aldosterone do?
Increases renal sodium and water reabsorption, to increase blood pressure.
Where is Anti Diuretic Hormone (ADH) formed, and then released from?
Formed in the hypothalamus, released by the posterior pituitary
What is the effect of Anti Diuretic Hormone?
Increases water reabsorption in the kidneys.
What causes the release of Anti Diuretic Hormone?
Reduced water concentration in the blood / lowered blood volume.
What substance inhibits ADH and why is this significant?
ADH is inhibited by alcohol. This is why drinking causes excess/urgent urination.
What do Anti Diuretic Hormone and Aldosterone have in common?
Both work on the kidneys, both cause reabsorption of water.
Which hormone is released by the atria in the heart when blood pressure rises too high?
Atrial natriuretic peptide (ANP)
Which hormone reduces blood pressure, by inhibiting the reabsorption of sodium and water in the kidney’s renal tubules?
ANP (Atrial Natriuretic peptide)
Which organ releases the hormone ANP?
The heart (in response to atrial stretch)
What is the action of parathyroid hormone?
Increases blood calcium levels, by:
- Increasing the activity of osteoclasts.
- Stimulating calcitriol release
- Stimulating renal absorption (rather than excretion) of calcium & magnesium
Where in the kidney is urine formed?
In the nephrons
What is micturition?
Weeing! The discharge of urine from the bladder.
Involves contraction of the bladder and relaxation of the internal (involuntary) and external urethral sphincters (voluntary in adults & over 5’s)
At what point do we start to get the urge to urinate?
When the volume in the bladder exceeds 200 - 400mls stretch receptors in the bladder send impulses up to the spinal cord, which results in the urge to urinate.
Which population of people have sweeter smelling urine?
Diabetics
How much urine is produced in a 24hr period normally?
1 - 2 litres.
We have to expel at least 500mls a day to get rid of core toxins and wastes.
What percentage of urine is water?
96%
Why do we find a lot of urea in urine (2%)?
Because we’re constantly metabolising a lot of proteins. The by-product of this is urea.
List 4 signs / symptoms of a urinary tract pathology
- Frequent & painful urination, with urgency
- Red urine (blood or beetroot?!)
- Pain in the loin
- High urine volume with great thirst
- Low or no urine volume
- Oedema
- Exhaustion (i.e, in kidney disease)
How would you differentiate between kidney back pain and musculoskeletal back pain?
- If the pain is movement related, it’s generally musculoskeletal.
- If the onset was mechanical (lifted funny, slept funny) its generally musculoskeletal.
List 3 signs of renal disease
- Pallor (due to anaemia, not producing erythropoietin)
- Frothy urine (leak of proteins into urine)
- Oedema (due to protein loss)
- Itchy skin (due to build up of wastes, i.e, urea)
- Altered mental state (common in UTI’s)
- Puffy face & bags under the eyes
- Dehydration
- Flapping tremor (too much urea in the blood)
How would you check for dehydration?
Skin pinch / recoil test on back of hand
Where would you see a flapping tremor, and what would it indicate?
In the outstretched hands. Indicates too much urea in the blood (kidney issues / disease)
What are the 2 forms of urinalysis?
- Dipstick analysis
2. Urine microscopy
What is a cystoscopy?
A medical examination (camera up into the bladder)
What is dysuria?
Pain on urination
Why can renal disease cause oedema?
Because loss of albumin into urine has an impact on osmotic pressure. Albumin pulls water into the blood, so if it’s not there, water goes into the tissues instead.
Which levels of the spinal cord are involved in the micturition reflex?
S2 & S3
What pathology might glucosuria indicate?
Diabetes mellitus (Glucosuria = glucose in the urine)
What might elevated nitrates on a urine dipstick test indicate?
A bacterial urinary infection
Is urine normally slightly acidic or alkaline?
Slightly acidic
What does GFR stand for and how is it measured?
Glomerular Filtration Rate.
Measured via blood test
What technical term describes blood in the urine?
Haematuria
What does polyuria mean?
Lots / large quantity of urine
What technical term describes protein in the urine?
Proteinuria
What does the term ‘oliguria’ mean?
Little urine (less than 400mls per day)
What technical term describes protein in the urine?
Bacteriuria
What is nocturia?
Night urination (waking to urinate)
What term describes a lack of / no urine?
Anuria
Diuretics are medications which increase loss of _____ and _____ from the kidneys
Sodium and water
