Renal and Urinary systems Flashcards
three functions of the nephron
1) filtration
2) tubular reabsorption
3) tubular secretion
afferent arteriole
carries blood to glomerulus
efferent
a tuft of capillaries that filters a protein-free plasma into tubular component
Bowmann’s capsule
collect the glomerular filtrate
proximal & distal tubules
uncontrolled reabsorption & secretion of selective substances occur here
descending loop of henle
reabsorption water
collecting duct
receives fluid from DCTs of several nephrons as it passes b/c into medulla
fluid travel through the nephron
renal artery -> afferent arteriole -> glomerulus -> efferent =» cortical nephron & juxtamedullary nephron
glomerulus -> Bowman’s capsule -> proximal tubule -> descending of henle -> thick, ascending loop -> distal convoluted tubule -> collecting duct -> ureters -> bladder
juxtamedullary (abundance, vasculature, location)
15-20% of all nephrons; very long nephron loops, efferent arterioles branch into vasa recta and long nephron; inner part of kidney called medulla
cortical nephron
most abundant; efferent arterioles branch into peritubular capillaries around PCT and DCT; within renal cortex, tip dips into renal cortex
factors governing glomerular filtration rate (GFP)
1) surface area of membrane
2) permeability of membrane
3) net filtration pressure
functions of urinary system
regulates
- water balance
- quantity of ECF ions
- plasma volue
- A/B balance
- osmolarity
- metabolic wastes excretion
- foreign waster excretion
- erythropoietin and renin secretion
- vitamin D to active form
nephron
- structural and functional unit of the kidney
- consists of glomerulus and renal tubules, and associated blood vessels
subdivisions of tubule
- Bowman’s capsule
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
cortical nephrons
- most abundant
- almost entirely in cortex
- only small part of LOOP of henle extends to medulla
juxtamedullary nephrons
- 15-20% of all nephrons
- @ cortex-medulla junction
- loop of henle extends deep into medulla
- have unique, straight vessels called the vase recta
What establishes the medullary osmotic gradient?
cortical and juxtamedullary nephrons
Kidneys also…(2 things)
- perform gluconeogenesis during prolonged fasting
- are also endocrine glands
glomerular filtrate
fluid collected in capsular space
hematuria
- damage to filtration membrane
- presence of blood cells in glomerular filtrate
proteinuria
- damage to filtration membrane
- increased presence of protein in urine
Forces regulating NFP
Outward
1. hydrostatic blood pressure (55 mmHg)
- bigg diameter of afferent and small diam of efferent
Inward
1. blood colloid osmotic pressure (30 mmHg)
2. capsular hydrostatic pressure
glomerular filtration rate
total amount of filtrate formed by the kidneys per minute (125 mL/ min)
What happens during exercise in terms of autoregulating the GFR?
- Blood pressure increases
- Afferent arteriole CONSTRICTS to maintain GFR, otherwise risk dehydration
What happens during relaxation in terms of autoregulating the GFR?
- Systemic pressure decrease
- Afferent arteriole DILATES to maintain GFR, otherwise not enough filtration
Filtration membrane is composed of 3 layers
1) Fenestrated glomerular endothelium
2) Basement membrane
3) Filtration slits
- Permits free passage of most substances less than plasma proteins
Myogenic mechanism
- Vascular smooth muscle cells contract when stretched (high BP), reducing blood flow
- Vascular smooth muscle cells relax and dilate when not stretched (low BP), increasing blood flow
(weightlifter, the pressure, in vessel wall)
What are the mechanisms that regulate (help to maintain) glomerular blood pressure?
Kidney has 2 autoregulatory mechanisms
- myogenic mechanism
- tubuloglomerular feedback mechanism
What happens in tubuloglomerular mechanism, when there is a high osmolarity vs. a low osmolarity?
1) High osmolarity (great concentration of ions, high filtrate flow rate) in terminal portion of ascending loop of Henle, reduced absorption (too high GFR)
- Macula densa cells release chemicals that cause vasoconstriction, that constrict afferent arteriole
- GFR decreases
- Tubular filtrate flow slows
- Reabsorption of sodium and chloride ions increases
2) Low osmolarity (low bp and GFR)
In response to low osmolarity, the macula densa cells
- Release less vasoconstrictor
- Signal the JG cells to release renin, JG cells can also sense the very low bp and rel. renin in response
Glycosuria
Abnormal urinary constituent: glucose
Nonpathological: excessive intake of sugary foods
Pathological: diabetes mellitus
Proteinuria
Abnormal urinary constituent: protein
Nonpathological: excessive physical exertion; pregnancy; high-protein diet
Pathological (over 250 mg/day); heart failure, severe hypertension, glomerulonephritis; often initial sign of asymptomatic renal disease
