week 9 Flashcards
Urinary system structure + function, renal regulation + urine formation and fluid + electrolyte balance
Primary function of urinary system
- Excretion
- Osmoregulation
- Acid-based balance
Secondary function of urinary system
- EPO secretion
- Renin
- Calcitriol
- Gluconeogenesis
- Detoxification
- BP homeostasis
Functions of urinary system components (4)
Kidney - produces urine
Ureter - Transports urine towards the urine bladder
Urinary bladder - temporarily stores urine prior to elimination
Urethra - Conducts urine to exterior, in males transports semen as well
External Anatomy
adrenal gland
fibrous tissue
fat layer
Overall diagram of kidney (label)
Cortex Medulla Renal capsule Pelvis Hilum
Nephron
- corpuscle, tubules & collecting duct
- filters blood to produce urine
- adjusts levels of nutrients & wastes by:
- reabsorption
- secretion
Urinary cycle
Renal artery -> segmental arteries -> interlobar arteries -> arcuate arteries -> afferent arterioles -> glomerulus -> efferent arteriole -> peritubular capillaries -> venules -> cortical radiate veins -> arculate viens -> interlobar viens -> renal viens
Afferent and efferent arteriole
Afferent arteriole ENTERS glomerulus - blood is filtered
Efferent arteriole leaves glomerulus
Peritubular capillaries delivers blood to venules
Nerve supply
- Autonomic control
- Sympathetic nerve fibres
- Adjust rate or urine formation
- Stimulates renin release
Renal nerve sympathetic activity
- Stimulates renin release
- Enhances renal sodium and water resorption
- Causes renal vasoconstriction
Path of urine flow
Kidney pyramids Minor calyces Major Calyces Renal pelvis Ureters Bladder Urethra
Parts of urine production
glomerular filtration, relevant pressures, tubular reabsorption, tubular secretion
Roles of kidneys in BP control
autoregulation, autonomic regulation
3 parts to the Nephron
- Renal corpuscle
- Renal tubule
- Collecting duct
Renal corpuscle
- afferent arteriole
- glomerulus
- bowman’s capsule/ capsular space
- efferent arteriole
Renal tubule (3 parts)
- proximal convoluted tubule (PCT)
- loop of henle
- distal convoluted tubule (DCT)
Nephron (2 substances involved)
Blood:
- is filtered (corpuscle) to make urine
Urine:
- which is collected in tubules and emptied into collecting ducts
Juxtaglomerular cells
- receptors
- in wall of afferent arteriole
- sense change in BP
- secretes renin when BP is low
Urine formation
- glomerular filtration
- tubular reasborption
- tubular secretion
What is reabsorbed
- most water 99%
- most ions (sodium & potassium)
- all nutrients
- urea (50%)
3 forces of filtration
- glomerular hydrostatic (forces water out of capillary into capsule)
- capsular hydrostatic (water pushes back into capillary from capsule)
- colloid osmotic (proteins inside capillary draw water back into capillary)
Net filtration pressure (NFP)
- Out of blood = 50 mmHg
- Back into blood = 15+25 mmHg
- Net = 50-40 = 10mmHg out of blood
Collecting system
- receive fluid from many nephron
- begins in cotrex
- descends into medulla
- carries fluid towards minor calyx
Micturition reflex (2 parts)
SNS - Store
PNS - Pee
Polyuria
lots of urine (>30mL/kg)
Oliguria
minimal urine (0.5mL/kg)
Anuria
no urine
Storage (micturition)
garding reflex -> distension -> afferent impulse -> increase sympathetic outflow ->increase bladder outlet tone and decrease detrusor contraction -> promotes continent
Voiding (micturition)
micturition reflex -> significant distension -> intense afferent impulse -> increase parasympathetic outflow and decrease sympathetic outflow -> decrease bladder outlet tone
Glomerular Filtration Rate (GFR)
- volume of fluid filtrated per minute
- normal GFR = 90-125 ml/min
Afferent arterioles dilate - more blood flows in, increase GFR
Afferent arterioles constrict - less blood in decrease GFR
Regulation of GFR
GFR need to be constant
- Low GFR = can’t excrete waste
- Hight GFR - less time for reabsorption
Body water content
- at birth: 70-80%
- adulthood: 50-65%
- old age: 40-45%
Body water intake and loss
INTAKE
preformed: 2300ml/day
metabolic: 200ml/day
LOSS kidneys: 1500ml/day skin: 600ml/day lungs: 300ml/day GIT: 100mml/day menstrual flow
Fluid compartments
Intracellular fluid (ICF) Extracellular fluid (ECF) - plasma - interstitil fluid - other
Water in the body
- main component of all body fluids
- movement via osmosis
- if fluids are balanced so are electrolytes
- we aim for balance unless directed otherwise
Dehydration
thirst centre in hypothalamus stimulated
adjusting water volume = ADH, aldosterone
ADH
- decrease plasma volume
- collecting ducts more permeable to water
- more concentrated urine
ADH secretion
- stimulated by anything that increases loss
- inhibited by alcohol and high blood volume
- dilute urine
Electrolytes in body fluids
inside: potassium, protiens and phosphates
outside: sodium and chloride
Specific Gravity (SG)
High SG:
- urine concentrated
- more solutes in each ml
Low SG:
- urine dilute
- less solutes in each ml
Aldosterone
- retain more sodium, water (water always follows sodium)
- more water (increases blood volume thus GFR)
