Urinary System 11 Flashcards
List 5 functions of urinary system
- Excretion of unwanted substances
- Water & electrolyte balance
- pH regulation - esp blood
- Hormone production - erythropoietin & calcitriol
- Red blood cell production regulation
- Blood glucose regulation
- Blood pressure, volume and osmolarity regulation
5 substances excreted by urinary system
Metabolic wastes - urea, uric acid and creatinine
Ions - hydrogen
Medications & toxins
Minimum urine content required to clear body waste
500ml/day
Which organ mostly controls water balance
Kidneys
What do Urea, Uric acid and Creatinine all contain?
Nitrogen - the kidneys specalise in removing nitrogenous wastes
What is Creatinine an end product of?
Muscle metabolism
What is uric acid an end product of?
Purine metabolism
What is Urea an end product of?
Protein metabolism
3 Most important electrolytes regulates by the kidneys
Sodium
Potassium
Hydrogen
What do buffers do?
Regulate changes in pH
CO2 is acidic. Kidneys excrete H+ into urine to produce bicarbonate to buffer the pH.
How should blood pH remain as?
7.35-7.45pH
What is the active form of vitamin D?
Calcitriol
Which organ converts vitamin D into its active form?
Kidneys
What does the hormone calcitriol do?
Stimulates calcium and magnesium uptake from the GIT
Reduces calcium loss in the kidneys
Which hormone stimulates erythropoiesis (red blood cell synthesis)?
Erythropoietin
How is Erythropoietin secreted
by kidneys into bloom (10% produced by liver)
What is erythropoietin released in response to?
Hypoxia - negative feedback system
What happens to erythropoietin in renal failure?
Production of erythropoietin is inadequate leading to anaemia
What is the renal threshold for glucose?
9 mmol/L
What is normal blood glucose levels?
4-7mmol/L
What does hypoglycemia indicate?
A pathology e.g. diabetes mellitus
What can kidneys make glucose from?
Amino acid glutamine
It helps to elevate blood sugar levels when hypoglycaemic - glucooneogenesis
How does the urinary system regulate blood volume, pressure and concertration
- it conserves or eliminates water in urine
- regulates ‘solute’ to help maintain constant blood concentration
- regulate blood pressure by kidneys excreting renin
What does renin do
It activates the renin-angiotensin aldosterone pathway
Increased renin causes an increase in blood pressure
Facts about kidneys
Reddish, bean-shaped organs that are retorperitoneal
Right kidney is lower (due to liver)
Perform major functions of the urinary system and secrete urine into the ureters
What 3 layers surround the kidneys?
Renal capsule
Adipose capsule
Renal fascia
What is the renal capsule
Deep layer - smooth, transparent sheet of connective tissue
Maintains kidney shape
What is the kidney’s adipose capsule
Middle layer of the kidney - mass of fatty tissue
Provides protection and support
What is the kidney’s renal fascia?
Outer, superficial layer
Thin layer of connective tissue that anchor the kidneys
What two regions are kidneys divided into?
Renal cortex
Renal medulla
What is the renal cortex
Superficial light red area
What is the renal medulla
Dark red area composed of
Renal pyramids
Apex of each renal pyramid is the renal papilla
What is the nephron
Functional unit of the kidney made from renal pyramids and renal cortex
Where does urine formed by the nephron drain into?
Minor and major calyces
What is the hilum
On the concave kidney border - the region where blood vessels, lymph vessels, nerves and ureters enter and exit the kidney
Where does the kidney’s blood supply come from?
Renal artery and renal vein
Kidney receives 20-25% of cardiac output despite its mass only accounting for 0.5% of body weight
What are the two parts of the nephron?
Renule corpuscle
Renal tubule
What is in the renal corpuscle
Glomerulus - tangled capillary network that receives blood
Bowman’s capsule
3 sections of the renal tubule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
What is the key role of the renal tubule?
Important role in reabsorption and secretion
Which hormone acts on the distal convoluted tubule to reabsorb water?
Antidiuretic hormone
Where does the nephron sit?
Renal corpuscle and both convoluted tubules - in renal corext
Loop of Henle - extends into renal medulla
What do the two ureters do?
Transport urine from the renal pelvis to the urinary bladder
How long are ureters and where do they sit in the body
25-30cm
Retroperitoneal
What propels urine along ureters?
Peristaltic contractions
What is the physiological valve
Valve that prevents the backflow of urine in the ureters
Three layers of the uteters
- inner mucous membrane
- muscularis
- outer adventitia
(same as the bladder)
Info on the ureters inner mucous membrane
Contains transitional epithelium which is able to stretch
Contains mucus secreting goblet cells for protection
What is the ureters muscularis made from
Smooth muscle - creates peristaltic contractions to move urine
What is the ureters adventitia made from and what does it contain?
Connective tissue
Contains blood and lymph vessels and nerves
What is the urinary bladder
Hollow, muscular organ that is a reservoir for urine
How full is the bladder when the desire to urinate occurs?
200ml
What is the total capacity of the bladder?
600-700ml
What is the small triangular area of the bladder called?
Trigone
What are the three layers of the urinary bladder?
- Inner mucosa layer
- Muscularis
- Adventitia
(same as the uretas)
In the bladder what is the transitional epithelium supported by
Connective tissue
What is another name for the muscularis in the urinary bladder?
Detrusor
What is the sphincter called in the muscularis
Internal urethral sphincter - involutary
What is the adventitia in the urinary bladder?
Connective tissue (same as the urethra)
What is the urethra?
Tube leading from the bladder to the exterior of the body - passageway for discharging urine
What does the male urethra pass through?
Prostate
What is the typical length of the female and male urethra?
Female 4cm
Male 20cm
What is the key difference beween the internal urethral sphincter and the external urethral sphincter
Internal = involuntar
External = voluntar
What are the 3 basic processes of urine formation?
- Glomerular filtration - in the renal corpuscle
- Tubular reabsorption - renal tubules
- Tubular secretion - renal tubules
4 ways glomerular capillaries are adapted for filtration
- large surface area
- 50 x more leaky that normal capillaries
- Efferent artieriole is less than the afferent arteriole
What can and what can not pass through the glomerular capilleries into the Bowman’s capsule?
CAN- water and small molecules - amino acids, mineral salts, hormones , creatinine, urea, uric acid
CAN NOT - blood cells, plasma proteins and other large molecules- leukocytes, platelets
What 3 pressures does glomerular filtration depend on?
- Blood pressure - promotes
- osmotic pressure - opposes
- capsular hydrostatic pressure - opposes
What is the glomerular filtration rate?
The amount of filtrate formed in the renal corpuscle of both kidneys each minute
What is a normal glomerular filtration rate?
over 90ml/min (males 125ml/min, females 105ml/min)
How is glomerular filtration rate calculated?
Through a blood test
What is glomerular filtration rate used to determine?
Severity of kidney disease
What is colloid osmotic pressure?
Osmotic pressure exerted by proteins
What can damage to glomerular capillaries lead to?
Plasma protein loss into urine
Albumin leaks into the filtrate
Less albumin in the blood makes it hypotonic making fluid via osmosis from blood to tissues - can lead to oedema
In tubular reabsoption how about of the glomerular filtrate is reabsorbed into the bloodsteam
Around 99%
What are the main components of the glomerular filtrate that are reabsorbed
Water
Amino acids
Glucose
Electrolytes
Where does most reabsorption occur?
In the proximal convoluted tubules
What substances get excreted into tubular fluid?
Waste products - creatinine, urea
Certain drugs
Exess ions
5 hormones that affect kidney reabsorption of sodium, chloride, calcium and water
- angiotensin II
- Aldosterone
- Antidiuretic hormone
- Atrial natriuretic peptide
- Parathyroid hormone
What does the renin angiotensin-aldosterone system do?
Increases blood pressure
What are the 4 main stages of the renin angiotensin-aldosterone system
If systolic BP is below 100mmHg the afferent arteriole walls stretch and…
- enzyme renin is released by kidneys into blood
- angiotensinogen ins converted into angiotensin I in the liver
- Angiotensin I is converted into angiotensin II by agiotensin-converting enzyme (ACE) in lungs
- Angiotensin II causes release of aldosterone from the adrenal cortex
What does angiotensin II trigger?
Vasoconstriction to increase blood pressure
What hormone does angiotensin II trigger the pituitary gland to release?
Anti-diuretic hormone
What does aldosterone do?
Increases renal sodium and water reabsorption
What does antidiuretic hormone do?
Reduces water concentration in the blood by increasing water reabsorption in the kidneys
Posterior pituitary secretes ADH
What does atrial natriuretic peptide do?
Inhibits the reabsorption of sodium and water into the renal tubules
Increase urine output, reduces blood volume which lowers blood pressure
What does parathyroid hormone do?
Released by the parathyroid gland in response to low blood calcium levels
Stimulates renal reabsorption of calcium and magnesium
Increases osteoclast activity
Stimulates calcitriol release
Stages of urine flow
- formed in nephron
- drains into papillary ducts (in the renal pyramids)
- drains into the minor and major calyces
4 drains into the renal bladder - drains into the bladder through the ureters
What does micturition mean
Discharge of urine from the bladder
When do the bladder stretch receptors transmit nerve impules
When the bladder exceeds 200-400ml
What triggers the mituration reflex in infants and adults
Infants - contraction of the detrusor muscle
Adults Conscious initiation and stop mituation
Where is the mituration reflex
Spinal cord levels S2 and S3
How much urine do we typically produce in 24 hours?
1-2l
pH of urine
4.5-8 (average 6)
Composition of urine
Water 96%
Urea 2% uric acid and creatinine
Ammonia
How does the urine system effect other systems?
Integumentary - vitamin D precursor
