Urinary System Flashcards
urinary system function
filter blood and create urine as a waste by-product
organs of the urinary system
kidneys, ureters, urinary bladder and urethra
excretory system functions
separating waste from body fluids and eliminating them
- metabolites - substance made/used when the body breaks down
- drugs
- toxins
homeostatic function
- maintenance of water balance
- electrolyte balance
- regulation of blood pressure (ECF balance) - maintenance of acid-base balance
endocrine function (secretory)
the kidney renin and juxtaglomerular complex
- erythropoietin -> RBC production
- prostaglandins
- kidneys convert vitamin D3 into active 1,25 dihydroxycholecalciferol
excretion
separating wastes from body fluids and eliminating them
body systems that excrete:
- respiratory, integumentary, digestive, urinary system
nitrogenous wastes and metabolic waste
- any substance that is useless to the body or present in excess of the body’s needs
- waste substance produced by the body
urea formation
- molecule that is produced by protein metabolism and found in urine
proteins -> amino acids -> NH2 removed -> forms ammonia, liver then converts ammonia to urea
liver converts ammonia to
urea
uric acid
product of nucleic acid catabolism (breakdown)
creatinine
product of creatine phosphate catabolism
blood urea nitrogen (BUN)
level of nitrogenous waste in blood
azotemia BUN
elevated BUN
- may indicate renal insufficiency
- kidneys are having trouble excreting waste which increases nitrogenous waste
Uremia BUN
syndrome of diarrhea, vomiting, dyspnea, and cardiac arrhythmia stemming from the toxicity of nitrogenous waste (too much waste for body)
- treatment is hemodialysis or organ transplant
dialysis- blood is filtered of waste and pumped back into the body
three protective coverings of the renal organ
- renal fascia - binds to abdominal wall
- perirenal fat capsule- cushions and holds kidneys in place
- fibrous capsule- encloses kidney to protect it from trauma and infection
ureter
tubular continuation that drains urine down from the kidneys to the urinary bladder
micturition
the act of urination
sympathetic stimulation innervation on the bladder
hypogastric nerve
- relaxes detrusor muscle to store urine
- constricts internal urethral sphincter
parasympathetic stimulation in the bladder
Pelvic nerve
- contracts detrusor to evacuate urine
somatic innervation in the bladder
voluntary, Pudendal nerve
- stimulation constricts external urethral sphincter
Sympathetic activity predominates (normal bladder filling)
- Pudendal nerve contracts external sphincter m. (somatic)
- hypogastric nerve contracts internal sphincter m. (sympathetic)
- inhibition of pelvic n. to detrusor m. allows relaxation
- as bladder fills, pressure stimulates sensory branch of pelvic n. and sends information to hypogastric to relax further
Parasympathetic activity predominates (normal micturition)
inhibition of hypogastric n. sympathetic activity on detrusor and internal sphincter m .
- voluntary inhibition of pudendal n. to relax external sphincter
- PSN stimulates via pelvic n. contracts detrusor m.
Renal Circulation
- high renal blood flow does not reflect O2 consumption
- high blood flow relates to the homeostatic function of the kidney (high rate of glomerular filtration)
Renal Blood Flow Chart
renal artery -> afferent arteries -> glomerulus -> THEN efferent arterioles -> venous system
Nephron
functional unit of the kidney
- 1.2 million nephrons in each kidney
- capable of forming urine
- kidneys cannot regenerate new nephrons, so with any damage to nephrons, there is less filtration or urine creation occurring
nephron composed of two principal parts:
- renal corpuscle- filters the blood plasma ( group of blood vessels, glomerulus inside)
- renal tubule- long, coiled tube that converts the filtrate into urine
renal corpuscle
consists of the glomerulus
- parietal outer later
- viscerla internal layer w/ cells called podocytes that wrap around the capillaries of the glomerulus
afferent arterioles
in the glomerulus
- produce filtrate
remaining nephron blood supply is
exclusively from efferent arteriole
formation of urine
- glomerular filtration
- tubular reabsorption
- tubular secretion
- water conservation
- excretion
glomerular filtrate
fluid that filters through the glomeruli into the Bowmans capsule
ultrafiltrate- plasma proteins, not the same as plasma. cant filter substances with an MW > than 65,000 Da
- if substance is bigger than this it can not be filtered and should NOT be present in urine (albumin, globulin, fibrinogen)
glomerular filtration rate (GFR)
quantity of glomerular filtrate formed in all nephrons of both kidneys per minute
- can show us how effective the kidneys are
- reabsorption so ur not always going to the bathroom
GFR depends upon
- osmotic pressure- salt/soluble conc. of blood (where does water want to go? water follows salt)
- hydrostatic pressure- arteriol system (increase BP and HR)
- filtration membrane characteristics:
- integrity
- thickness
- permeability
- surface area
hydrostatic pressure in capsule
drives fluid out of the capsule
Factors affecting GFR
- increase blood flow through nephron (local) or kidney (general)
- elevates the glomerular pressure, increases net filtration pressure and then increases GFR
- directly related to the diameter of blood vessels - Colloid osmotic pressure
- hypoproteinemia will increase the filtration rate - Capsular pressure
- back pressure increases the bowmans capsule hydrostatic pressure which leads to decreasing GFR
Glomerular Hydrostatic Pressure is determined by
- arterial pressure
- afferent arteriol resistance
- efferent arterial resistance
- promotes filtration - it pushes water and solutes in blood plasma through the glomerular filter
factors affecting GFR
- permeability of glomerular capillaries (hydrolic conductivity)
- increase in permeabilty will increase GFR - Surface area of the membrane
- decreases will decrease GFR
Tubuloglomerular Feeback
the kindeys response/alteration to filtation
- Juxtaglomerluar apparatus/complex = region of the nephron where afferent arterioles and distal conv. tubules come in contact
- sensory cells modify filtration rate in kidneys
Juxtaglomerluar apparatus/complex
specialized region of the nephron where the afferent arteriole and distal convoluted tubule come in direct contact
Juxtaglomerluar apparatus/complex consists of:
- Juxtaglomerular cells
- renin (made in kidneys, renin is released into bloodstream when BP is low) synthesize and storing - Macula densa cells
- sodium sensors in the distal convoluted tubule
- sense change in solute concentrations and flow rate
GFR (glomerular hydrostatic pressure) increases, explain next steps
- more filtration occurs and flow through tubule increases
- flow past macula densa increases (lower Na+ conc.)
- paracrine from macula densa to afferent arterioles
- afferent arterioles constrict
- resistance in afferent arterioles increases
- hydrostatic pressure in glomerulus decreases
- GFR decreases `
formation of urine
- glomerular filtration
- peritubular reabsorption
- peritubular secretion
- excretion
proximal convoluted tubule
surface of nephron is covered with microvilli creating a brush border
- microvilli greatly increase SA of the cells allowing for resorptive function and putative flow sensing within the lumen
- Na+, Cl-, water reabsorbed
- urea minimally permeant
desirable solutes resorbed from urine
NaCL, sugars, amino acids
- water follows osmotically
- no change in osmolarity of urine (isosmotic to plasma)
reabsorption of other substances in proximal convoluted tubule
some parts of the tubule, especially PCT, reasbsorb large molecules
- reabsorb proteins by pinocytosis
Urea
waste produced by the body after metabolzing protein
- produced when the liver breaks down proteins or amino acids, and ammonia
- the kidneys transfer the urea from the blood to the urine
loop of henle - descending limb
high permeability for water ( ions by solvent drag) through a weak tight junction
loop of henle- ascending limb
thick part
- simple cuboidal with no brush border, NO water transport
urine concentration in loop of henle
- thin descending limb of Henle is permeable to water, but NOT solutes
- thick ascending limb of Henle is IMpermeable to water and solutes. contains active transport mechanisms for chloride and sodium
ascending and descending limb with solutes
Na and CL are reabsorbed by thick ascending limb INTO the peritublar FLUID (out of limb)
- these ions elevate the medulla osmotic pressure
- this increases osmotic flow of water out of the thin descending limb
- increased osmotic potential of tubular filtrate increases active transport in the TAL
loop of henle summary: reabsorption
descending limb:
- 25% water
ascending limb:
- 20-25% of sodium and chloride to help maintain the countercurrent system
macula densa
chemoreceptor for NaCL
functions of aldosterone
tubule and collecting duct increase Na+ reabsorption and K+ excretion by the renal tubular cells
stimuli for renin secretion
- sympathetic stimulation of the kidneys
macula densa cell cause kidneys to produce renin - circ. catechoamines- epinephrine
- local decrease in arterial pressure in afferent arteriole
stimuli for aldosterone secretion
- stimulation of the adrenal cortex by angiotension 2
- high (K) plasma
angiotensin 2 pathway
- renin is released to the blood by JGA cells due to decreased renal blood flow or perfusion
- renin converts a plasma protein (angiotensinogen) into angiotensin 1
- angiotensin-converting enzyme (ACE) in the lungs converts amgiotensin 1 into angiotensin 2
angiotensin 2
- vasoconstrictor (increases blood pressure) on efferent arterioles and increases GFR
- acts on adrenal cortex cells which then stimulates aldosterone release
- direct action on the thirst center in the hypothalamus and stimulates thirst
- directly acts on the proximal tubules of the kidney stimulating increased Na reabsorption
- increases ADH release from the neurohypophysis
summary of DCT
- water reabsorption
- calcium found and controlled by parathyriod hormone
- sodium, and choride under aldosterone control
collecting duct
intercalculated discs that secrete H+ and bicarb if needed to filtrate
PERMEABILITY TO WATER
antidiuretic hormone (ADH)
vasopressin
- peptide hormone from the neurohypophysis
- produced in the HYPOTHALAMUS
- water permeability on DCT and CD
- vasoconstriction on arterioles
- stimuli for secretion
action of ADH on kidneys
- vasopressin binds to membrane receptors
- receptors activates cAMP second messenger system
- cell inserts AQP2 water pores into apical membrane
- water is absorbed by osmosis into the blood
ADH does NOT
increase the amount of solute loss
- GFR will NOT change either
- NaCL loss is the same
- progressively more water is retained and urine becomes isosmotic to plasma
isosmotic
having the same osmotic pressure
urine specific gravity (UFG)
mass of one mililiter of solution in grams
- an indication of BOTH the number and weight of the particles in urine
diuresis
increased excretion of urine
pressure diuresis
increasing mean arterial pressure and urine flow increases
- compensatory mechanism to maintain blood pressure within normal range
- increases water and sodium output in filtrate/urine
osmotic diuresis
increased urination due to the presence of certain substances in the fluid filtered by the kidneys
- fluid eventually becomes urine
- process of osmosis created by these substances cause additional water to come into the urine, increasing its amount
diuretics
help the body get rid of sodium and water
- decrease blood pressure bc a decrease in plasma volume decreases BP
renal corpuscle
filtration ( filters blood plasma )
- nephrons
proximal convoluted tubule
reabsorption and secretion
- vital
- high permeability to water
loop of henle
ascending and descending loops
- solution concentration
descending limb: high permeability to water
ascending limb: NO permeability to water
distal convoluted tubule and collection duct
reabsorption and secretion (optional)
