Urinary Flashcards
Functions of the urinary system
⭐️ excretion of unwanted substances
⭐️maintenance of water & electrolyte balance
⭐️ pH regulation of body fluids (especially blood)
⭐️ production of hormones (erythropoietin & calcitrol)
⭐️ regulation of RBC production
⭐️ regulation of blood pressure, volume & osmolarity
⭐️ regulation of blood glucose levels
What compound does the kidneys specialise in excreting
Nitrogenous wastes
(Amino acid/protein building blocks of nitrogen)
What wastes and toxins do the kidneys excrete
- Urea - metabolite of protein metabolism
- Uric acid - purine metabolism product
- Creatinine - muscle metabolism product
- Hydrogen ions - excess acidity
- Medications & toxins - detoxed in the liver
What is the minimum urine content required to clear body waste
500ml/day
What are the most important electrolytes regulated by the kidneys
Sodium, potassium & hydrogen
What are buffer substances
Molecules that can buffer/regulate changes in pH
By conjugation
What are the two primary pH control systems
Lungs - excrete co2
Kidneys - excrete hydrogen & produce buffer bicarbonate
What is calcitriols role with the kidneys
UV light triggers vitamin D precursor in skin
Kidneys converts to calcitriol
This increases bone formation (calcium absorption) & reduces calcium loss in kidneys (along with PTH)
Deficiency can cause osteomalacia and rickets
What are normal blood glucose ranges
4-7 mmol/L
Above 9 inidcatez pathology eg diabetes mellitus
What process do kidneys undergo to make glucose when hypoglycaemic
Make glucose from the amino acid GLUTAMINE
- gluconeogenesis
How do the kidneys maintain a constant blood concentration/osmolality
Conserve/eliminate water
Regulat loss of solute
Regulate blood pressure by secreting enzyme RENIN to acitivate Renin-Angiotensin-Aldosterone pathway
Where are the kidneys located
Partially protected by the 11th & 12th pairs of ribs (between vertebrae T11-L3)
Right kidney is lower than left because liver occupies space on right side superior
What layers surround the kidneys
1) renal capsule (deep layer) - connective tissue
2) adipose capsule (middle layer) - protection & support
3) renal fascia (superficial layer) - connective tissue that anchors kidneys in place
What is the renal papilla
The point of the renal medulla pyramids where urine collects to enter the ureter
What is the renal hilum
The region where blood vessels, lymph vessels, nerves & ureters enter & exit the kidney
Kidneys receive 20-25% cardiac output
What is a kidney nephron
Functional unit of the kidney
More than 1 million per kidney
Single epithelial layer
Layers:
1) renal corpuscle
2) renal tubule
What is the glomerulus
A tangled capillary network that receives blood from an afferent arteriole in the kidney
What is the bowmans capsule
A double walled epithelial cup that surrounds the glomerulus, receiving contents of filtered blood
What is the renal tubule
Filtered fluid is passed through the tubule and is important in reabsorption & secretion of various solutes
How does ADH act on the kidneys
Acts on the distal convoluted tubule to reabsorb water
What is the loop of henle
Loop in the renal tubule that descends & ascends
Function of the 2 URETERS
Peristaltic contractions of their muscle walls propel urine down down into bladder
Why do ureters have a mucous membrane
Assists in reducing friction & allows easy movement as well as a protective layer from urine
What is transitional epithelium & where found
Epithelium with ability to strectch
Found in the bladder !
What is the trigone
Located on posterior floor of bladder, small triangular shape bordered by the two ureteral openings & the urethral opening
What is the detrusor
The smooth muscle found in the muscularis layer of the bladder
The fibres accumulate & form the internal urethral sphincter
What is the urethra
Tube leading from the bladder to the exteroir of the body, passageway for urine & in males semen too
What are the 3 basic processes of urine formation
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
What molecules can pass through the glomerulus
Water & small molecules can pass through the pores in the glomerular capillaries
Mineral salts (electrolytes)
Amino acids & glucose
Ketoacids
Hormones
Creatinine
Urea
Uric acid
Toxins
How is glomerular filtration adapted
- The diameter of the efferent arteriole (ie enters at high pressure) is less than that of the afferent
- 50x more leaky than normal capillaries
What molecules cant pass through glomerular filtration pores
Leukocytes
Erythrocytes
Platelets
Plasma proteins
What 3 main filtration pressures do glomerulus depend on?
- Blood pressure in the glomerular capillaries force substances through
- Proteins present in blood plasma maintain osmotic pressure & oppose blood pressure
“Blood colloid osmotic pressure” - Back pressure of fluid already passed through in the tubule opposes filtration
“Capsular hydrostatic pressure”
What is the glomerular filtration rate (GFR)
The amount of filtrate formed in the renal corpuscles of both kidneys each minute
Males = 125ml/min
Females = 105ml/min
Normal should be over 90ml/min
Calculated through a blood test helps determine kidney disease
Anything affecting 3 filtration pressures will affect GFR
What is colloid osmotic pressure
A form of osmotic pressure exerted by proteins (notably albumin)
What can damage of the glomerular capillaries lead to
Can lead to plasma protein loss into urine, specifically albuminuria
Less albumin in blood makes it hypotonic, fluid moves from blood into tissues
Decreases blood volume & interstitial fluid volume increases leading to oedema
What is most commonly reabsored into the bloodstream in the renal tubules & collecting ducts
Water (65% in PCT)
Amino acids & glucose
Electrolytes
Most reabsorption occurs in the proximal convoluted tubule
What does angiotensin mean
Angio = vessel
Tensin = constriction
2 Triggers vasoconstriction which increases blood pressure & triggers pituitary release of ADH & adrenal cortex to produce aldosterone
What 5 hormones affect kidney reabsorption of sodium, chloride, calcium, water & potassium secretion
- Angiotensin II
- Aldosterone
- ADH
— all 3 increase blood pressure - Atrial Natriuretic peptide
— works to lower blood pressure - Parathyroid hormone
— elevates blood calcium lvls
What is the overall effect of the ‘RAAS’ system
Increases blood pressure
Angiontensin II = vasoconstriction
Aldosterone = water reabsorption in kidneys
What are the effects of Atrial Natriuretic Peptide
Inhibits reabsorption of sodium & water in the renal tubules
ANP is released in response to atrial stretch, reducing blood volume and increasing urine output hence lowering blood pressure
Also suppresses release of ADH & aldosterone
How does PTH increase blood calcium
Stimulates renal reabsorption of calcium & magnesium
Increases osteoclast activity
Stimulates calcitriol release (increasing gut calcium absorption)
What does micturition mean
The discharge of urine from the bladder
What is the micturition reflex
When volume in bladder exceeds 200-400ml stretch receptors in bladder wall transmit nerve impulses to spinal cord at levels s2 & s3
Generating a micturition reflex, relaxing internal urethral sphincter (& external in infants)
What are the usual compounds found in urine
Water (96%)
Urea (2%) uric acid & creatinine
Ammonia
Na, K, Cl, P, S
Hormones
Oxalates (found in fruit & veg)
What signs & symptoms need to be looked out for indicating urinary system pathology
Frequent & painful urination with urgency
Red urine (blood or foods?)
Pain in the loin
High urine volume with great thirst
Low or no urine volune
Nausea & vomiting
Oedema
Exhaustion
Common signs of renal disease
- pallor (due to anaemia)
- frothy urine (proteinuria)
- oedema
- signs of itching skin (uraemia)
- altered mental state (common with UTIs)
- puffy face & bags under eyes
- dehydration (slow skin recoil) & flapping tremor (shaking wrists when extended)
main types of urine analysis
- Dipstick test
- Urine microscopy
- Blood test - GFR, Urea, creatinine, electrolytes
- Ultrasound, cystoscopy, MRI, CT
- Inflammatory markers
What are casts
Groups of cellular materials that clump together in kidney nephrons
Dysuria
Painful, burning urination
Oliguria & polyuria
Polyuria = large quantity of urine
Oliguria = little urine (<400ml/day)
Anuria
No urine
Nocturia
Night urination - waking to urinate
Why can increased glomerular permeability lead to oedema
Loss of plasma proteins leads to low plasma osmotic pressure, so fluid moves out of capillaries into tissues = oedema
What are the use of diuretics
Meds which increase loss of sodium & water from kidneys
Reduce reabsorption from kidney tubules
Used for oedema & hypertension
Common bacterial cause of cystitis
E.coli
What is glomerulonephritis
Immune mediated disease that causes glomerular inflammation
Autoimmune reaction (type III hypersensitivity) where antigen-antibody immune complexes are formed in response to infection. These are deposited in the glomeruli where they trigger immune response, causing leaky capillaries & leukocyte proliferation allowing proteins & erythrocytes to escape into urine
Immune mediated can occur 1-3 weeks after bacterial infection (often from upper respiratory tract) eg children can develop post-streptococcal glomerulonephritis
What is nephrotic syndrome
A collection of signs & symptoms associated with increased glomerular permeability & heavy proteinuria
Not a cause but a syndrome Eg lupus can be cause
Why are you more likely to develop kidney disease when diabetic
Diabetes mellitus elevates blood pressure
Glomerulosclerosis occurs as a result of increased intra-glomerular pressure
Kidenys are often enlarged
Glomeruli often become damaged & proteins leak leading to associated syndrome
What are renal calculi usually made of
80% calcium oxalate & phosphate
What is haemodialysis
Used in cases of renal failure, blood is taken through a machine whereby mimicing excretory function of kidneys to remove wastes/balance electrolytes etc
What is peritoneal dailysis
Same case as mimicing kidney functions in states of renal failure but envolving extraction through the peritoneum itself, utilising the highly vascular semi-permeable membrane to allow for diffusion of fluids & dissolves substances
Tube inserted into abdomen which administers dialysis fluid, through which waste products diffuse into, removal occurs via a shunt & changing dialysis solution when in excess
What is the renal threshold for glucose
9mmol/L
What is a metabolic waste excreted by kidneys
Uric acid
What forms the renal corpuscle
The glomerulus & bowmans capsule
What hormones are produced by the kidneys
Erythropoietin & calcitriol (converts vitamin D inactive form to active)
