Lecture 9: Urinary System Flashcards
What 3 processes are involved in the production of urine & adjustment of blood composition
- glomerular filtration
- Tubular Reabsorption
- Tubular Secretion
How many times per day does renal system filter plasma volume
more than 60 times per day
- 180L fluid per day
how much fluid does renal system excrete per day
~ 0.5 - 2.0L per day leaving 178 - 179.5 L to be reabsorbed
-99% of water that is filtered out of glomerular blood per day is reabsorbed into tubular blood
The process of filtration
- created from blood
- passive and non selective: substances (liquids, solutes) are pushed through the mebrane by hydrostatic pressure
What is a key feature of filtration
glomerular capillaries are long and have high pressure for efficient filtration
-the membrane of filtration is very permeable to H2O and solutes
what ensures elevated pressure in filtration membrane
-inferior diameter in the efferent capillaries compared to the afferent capillaries ensure elevated pressure
How does hydrostatic pressure of glomerular capillaries (blood pressure) work in filtration
Push H2O and solutes out of blood and through the filtration membrane
How does osmotic pressure of glomerular capillaries work in filtration
Due to plasma protein
How does hydrostatic pressure of capsular space work in filtration
Exerted by the liquids of the capsular space
How does movement work.in reabsorption
From filtrate to blood
- process is done actively and passively depending on substances that are being reabsorbed
How does reabsorption work in kidney
- let’s H2O and solutes EXIT from blood
- filtrate then reabsorbs (into blood) useful elements leaving behind (into filtrate) elements to EXCRETE
What is trascellular route of reabsorption
- Apical membrane -> cytosine-> basolateral membrane (can involve lateral intracellular space) -> interstitial fluid -> capillary
What is the paracellular route of reabsorption
Movement through leaky tight junction (especially proximal convoluted tubule)
What is proximal convoluted tubule (PCT)
Principal site of reabsorption
- other structures: help to adjust the blood composition to maintain homeostasis via secretion
- Control: changes in osmotic pressure (blood) in peritubular & vasa recta capillaries, H2O reabsorbed passively (osmosis) from filtrate
What happens in the loop
- permeability changes
- H2O (osmosis) in descending limb
- symport Na+, Cl- in ascending limb
What happens in Distal Convoluted Tubule (DCT)
- controlled via hormones: ADH & aldosterone
- symport Na+, Cl-
What happens in collecting duct (CD)
- hormone (ADH & aldosterone)
- Na+ channels (aldosterone used to reabsorb sodium)
- K+ channels: (aldosterone used for its reabsorption)
- H2O (ADH for its reabsorption)
- H+, HCO3 (according to blood pH, urea with or without ADH)
What are the 2 types of counter current mechanisms that concentrate urine
- Countercurrent multiplier
- ascending & descending limbs of long loop of juxtamedullary nephron - Countercurrent exchanger
- ascending & descending portions of vista recta
What osmotic gradient do the kidneys need to maintain
~ 300 mmol/ kg
What us the vasa recta
- all permeable to H2O and solutes
- with countercurrent exchanges btw the vasa recta & the interstitial fluid allows the blood remain to isomotic to surrounding (maintains the osmotic gradient )
What is the urine composition
95% water Dissolved substances: - nitrogen wastes - electrolytes - toxins - pigments - hormones - abnormal constituents
What is pyelonephritis
- infection & inflammation of entire kidney
- leads to edema, formation abscesses, accumulation of pus
- tx: antibiotic
What is pyelitis
- infection of the pelvis and calyces
- ascending urinary tract infection
- antibiotic therapy
What is anuria
- abnormally weak urinary flow
- cause: glomerular arterial pressure too low to undertake filtration
- ex: brought about via a crushing wound or an acute nephritis
What is cystitis
- inflammation of the bladder
- caused by bacteria; painful & frequent micturition
What is Urethritis
- inflammation of urethra
What is incontinence
- inability to control voluntarily micturition
- causes: emotional problems, physical pressure (pregnancy), troubles with NS, age ex. Baby or elderly
What is Enuresis
- inability to control micturition during sleep (toddler/ elderly)
What is diabetes insipidus
- state where a large quantity of dilute urine is eliminated (polyuria) & thus get also an intense thirst (polydipsia)
- lack / insufficient quantity of ADH
- tx: hormone
What is addison’s disease
- excrete large quantities of Na+, Cl-, H2O
- cause: lack/ insufficient quantities of aldosterone (& also cortisol)
- must maintain liquids / salts
