urinary system

micturition / urination

process of releasing urine from urinary bladder through urethra

what makes urine yellow in colour ?

urochrome/urobilin from haemoglobin breakdown

micturition can be accelerated using ?

diuretics

where are the kidneys located ?

retroperitoneal space

what structures make up the lobes of the kidney ?

renal pyramids

the kidneys are supplied by what artery ?

renal

blood supply to and from kidneys

3 major functions of kidneys

regulate blood volume

remove urea

regulate acid-base balance

what hormones do the kidneys produce ?

erythropoietin and renin

what is the glomerulus ?

tuft of capillaries adapted for filtration

the Bowman’s capsule is connect to the PCT by

the urinary pole

how much plasma is filtered per minute by the kidneys (avg. GFR rate) ?

120-140ml

what is filtrate ?

plasma without proteins or cells

how much plasma is reabsorbed after filtration ?

119 - 124ml

label the nephron structures

1 - bowmans capsule

2 - glomerulus

3, 4, 5 - loop of henle

6, 7 - collecting duct

8 - distal CT

9 - proximal CT

the loop of Henle lies in what section of the kidney ?

medulla

what are the functional units of the kidney ?

nephrons

3 stages of nephron function

1. glomerular filtration

2. tubular reabsorption

3. tubular secretion

what regulates GFR ?

• arteriole vasoconstriction

• mesangial cell contraction

• podocyte permeability

what is reabsorbed in the PCT ?

K+ Na+ amino acids glucose water

what is reabsorbed in the loop of Henle

Na+

what is reabsorbed in the collecting duct

water

how much urine is produced per minute on average ?

1ml / min

how long are the ureters and where are they located ?

20cm either side of vertebral column

what prevents urine back flow from the bladder to kidneys ?

ureterovesical valves

what are the three layers of the ureter wall ?

• inner mucosa

• muscularis

• outer adventitia

how much urine can the bladder hold ?

500ml (max 1000)

what are the 3 layers of the bladder ?

• mucosa - transitional epithelium

• muscular layer - longitudinal and circular muscles

• fibrous adventitia

the internal / bladder neck urethral sphincter is composed of what muscle type ?

smooth muscle - involuntary

what muscle controls voluntary urination ?

external urethral sphincter - skeletal muscle

urine passes from where to the ureter ?

renal pelvis

how do the male and female urethra differ ?

length - male urethra longer

nervous control of micturation

sympathetic - senses bladder stretch, relaxes bladder and internal sphincter

parasympathtic - external sphincter, automatically contracts bladder

blood in the urine indicates

infection

what is diuresis ?

increased production of urine

what’s the difference between water diuresis and osmotic diuresis ?

water - more water ingested than body requires

osmotic - more solute excreted than normal

how do diuretics work ?

increase water and NaCl excretion via kidneys

role of kidneys in homeostasis

remove urea, control water/ion balance, regulate BP, maintain pH

what organ carries out the urea cycle ?

liver

in the urea cycle ammonia is converted to

urea and excreted in urine

osmolarity

total number of dissolved particles in solution

what is the standard body fluid osmolarity ?

295mOsml/L

what is the juxtaglomerular complex ?

structure that regulates each nephron's function

next to glomerulus

what cells detect NaCl in the distal tubule ?

macula densa cells

name 3 ways GFR is regulated

1. myogenic mechanism

2. tubuloglomerular feedback

3. renin-angiotensin-aldosterone system

what triggers renin release ?

low BP, low NaCl or SNS activation

how does ADH increase BP ?

increases water, urea and sodium reabsorption, and vasoconstriction