BIOL 2510 exam 3 WADA

Renal cortex

outer layer

renal medulla

inner layer. contains renal pyramids. drains from the nephrons

renal artery

supplies oxygenated blood to kidneys to be filtered and processed

renal vein

returns reabsorbed nutrient and ions back to body

renal calyx (minor)

right outside renal medulla. drains urine from renal pyramids to renal pelvis

renal calyx (major)

right outside of renal calyx minor, drains urine from renal pyramids to renal pelvis

renal pelvis

drains urine from renal calyx

ureter

where urine exits the kidney

hilum

entrance to renal sinus. contains:

-renal artery and vein

- ureter

- nerves

- lymphatic tissue

part of tracing a drop of filtrate

nephron-minor calyx-major calyx-renal pelvis-ureter-bladder-urethera-exit body

functions of kidney

1. homeostasis

- pH (H & HC03), blood pressure (H20), blood osmolality and ion balance (Na,K,Cl)

2. eliminate waste

- urea secretion, toxins and drugs, extra Na

3. conserve glucose and amino acid

4. hormone secretion

- renin (regulate BP)

- erythropoietin (hormone for RBC production in response to hypoxia)

5. metabolize vitamin D to its active form

nephron facts

- functions of kidneys are done by nephrons

- functional unit of the kidney

- involved in filtration of blood, reabsorption, and secretion of substances

- 1-1.5 nephrons in a kidney

order of flow in a nephron

renal artery-afferent arteriole-golerulus-efferent arteriole-peritubular capillaries/vasa recta

afferent arterioles

delivers blood to glomerulus

glomerulus

- capillary bed

- main cite of filtration

- high BP

- leaky capillary walls

- filters around 20% of blood

efferent arterioles

- takes away unfiltered blood (around 80%)

- still oxygenated blood

juxtaglomerular apparatus

where distal tubule and afferent arteriole come together. important for BP regulation

peritubular capillaries/vasa recta

collect ions and nutrient through reabsorption and return them to our body via renal vein

order of flow in nephron tubular

bowmans capsule-proximal convoluted tubule-descending loop of henle-ascending look of henle-distal convoluted tubule-collecting duct-minor/major calyx-renal pelvis-ureter-bladder-urethra-exit body

bowmans capsule

cups around glomerulus that collect filtrate from the glomerulus. where filtrate appears first

proximal convoluted tubule

attached to BC and where most reabsorption occurs (around 65%) including Na+, H2O, amino acids, and glucose

loop of henle

- crosses the border between cortex and medulla

- makes the medulla salty by actively pumping out Na+, K+, and Cl- in the ascending limb of loop of henle

- reabsorb water in the descending by osmosis. water is picked up by vasa recta

distal convoluted tubule

more reabsorption of Na and HCO3

collecting duct

collects filtrate from multiple nephrons. reabsorb H2O when needed

types of nephrons

juxtamedullary nephron & cortical nephron

cortical nephron

short loops of henle, doesnt go deep into medulla

juxtamedullary nephron

- long loop of henle that are in the medulla where there is high osmolarity gradient.

- LOH is surrounded by vasa recta which is important for establishing osmolarity gradient in renal pyramid

peritubular capillaries

around proximal and distal tubules, this is the LOH of cortical nephrons

vasa recta

- extends deep in the medulla

- helps to form concentrated urine

- supplys O2 and nutrient to kidney tissues

- surrounds LOH of juxtamedullary nephrons

what is the renal pyramid/medulla?

SALTY

3 processes of the nephron

1. glomerular filtration

2. tubular reabsorption

3. tubular secretion

filtration

filtration of the blood at the glomerulus/bowmans capsule. what is filtered is called filtrate

reabsorption

selectively move substances from filtrate back into blood. getting glucose or amino acids from filtrate

secretion

selectively move unwanted substances from blood into filtrate

excretion

what is not reabsorbed or secreted with be excreted from the body as urine

equation for nephron process

amount filtered - amount reabsorbed + amount secreted = amount excreted

glomerulus/bowmans capsule filtration

- H2O

- NaCl

- K+

- HCO3-

- glucose

- amino acids

- creatinine and urea (waste)

proximal convoluted tubule reabsorption

- K+ & NaCl (65%)

- H2O (65%)

- Amino acid and glucose (100% at this location)

- HCO3- (90%)

proximal convoluted tubule secretion

some drugs and H+

descending loop of henle reabsorption

WATER (25%)

ascending loop of henle reabsorption

SODIUM

distal convluted tubule reabsorption

- NaCl (5%)

- H2O

- HCO3-

distal convoluted tubule secretion

K+ and H+

collecting duct reabsorption

- NaCl (5%)

- H2O when needed

- Urea (maintaining osmolarity gradient in medulla

excretion from nephron

- H20

- NaCl

- K+

- HCO3-

- creatinine (biproduct of muscle metabolism. only thing not absorbed or secreted)

- urea (main component of urine)

hormonal control in nephron process

- aldosterone (NaCl reabsorption (water follows))

- Antidiuretic hormone (ADH) (H2O reabsorption)

how much volume entered is in urinary excretion

1%

how much blood that enters afferent arterioles is returned to systemic circulation

99%

podocytes

epithelial cells of bowmans capsules (lowest layer)

fenestrated endothelial cells

In the basement membrane (top layer), these cells have large, open pores (leaky). lets Na+ and glucose through, WBC and proteins cant get through.

glomerular filtration rate (GFR)

- volume of filtrate formed between glomerulus and bowmans capsule each minute.

- average is 125 mL/min or 180 L/day

- dependent on NFP

Net filtration pressure (NFP)

net force that determines how much H2O and solute leave the blood in the glomerulus

pressure favoring filtration

- hydrostatic pressure in glomerular capillaries (HPgc).

- force exerted by BP

- 55 mmHg

- high compared to other capillaries because diameter of afferent arteriole is larger than diameter of efferent arterioles

- push out of glomerulus

- pressure can change depending on the diameters of AA or EA

Pressure opposing filtration

- colloid osmotic pressure in glomerular capillaries (OPgc)

- force created by proteins in the blood

- 30 mmHg

- hinders movements of fluid into BC

- hydrostatic pressure in BC (HPbc)

- force exerted by filtrate in the BC

- 15 mmHg

- interfered with movement of filtrate into BC

formula for pressures

NFP = HPgc - OPgc - HPbc

- favors filtration

- if you get negative, it opposes filtration

relationship between new filtration pressure and GFR

increase NFP, increase GFR

NFP formula

hydrostatic P of GC - colloid osmotic P of GC - hydrostatic P of BECAUSE

hydrostatic P of GC

- changes with BP inside the GC

- alter diameter of AA or EA

colloid osmotic P of GC

- changes with number of proteins

- increase proteins, increase fluid in GC, decrease GFR

afferent arteriole relationship of diameter and GFR

direct relationship

efferent arteriole relationship of diameter and GFR

inverse relationship

macula densa cells

monitor concentration of Cl in tubule

CHEMORECEPTOR

granular cells

- monitor pressure in afferent arteriole

- secrete renin (BP regulation)

- MECHANORECEPTOR (sense change in pressure)

2 intrinsic controls of GFR (keeping GFR constant)

myogenic mechanism & tubuloglomerular feedback

myogenic mechanism

- high blood flow in afferent arteriole (AA will vasoconstrict, lowering GFR)

- low blood flow in afferent arteriole (AA will vasodialate, increasing GFR)

tubuloglomerular feedback

- macula densa cells detects NaCl concentration in filtrate

- slow moving filtrate --> low concentration of NaCl in filtrate (more time), AA vasodialate, GFR increase

- fast moving filtrate --> high NaCl concentration in filtrate. AA vasoconstrict, GFR decrease

regulation of GFR (extrinsic)

LOW BP

- increase renin

- increase angiotensin II

- increase aldosterone

- increase ADH

- increase HR

all to work to increase the BP

HIGH BP

- decrease renin

- decrease angiotensin II

- decrease aldosterone

- decrease ADH

- slower HR

- ANP

all work to decrease BP

Atrial natriuretic peptide (ANP)

- hormone that is released by atria due to atrial stretch when there is an increase in blood volume.

- ANP decreases renin

- decrease renin = decrease angiotensin II

- decrease ADH = decrease water reabsorption in nephron

2 common means of reabsorption in PCT, LOH, DCT

1. Na+/K+ ATPase uses energy

- to pump Na+ against its gradient its concentration gradient

2. Using the established concentration gradient of Na+, nutrient such as glucose, amino acids, and ions come into the tubule cells

proximal tubule active transport

Na+/K+ ATPase

Na+ - H+ ATPase --> H+ secretion

Na+ - HCO3-ATPase --> HCO3- reabsorption

proximal tubule secondary active transport

- Na+ contransporter/symporter

- use energy that Na+ going down its concentration gradient

proximal tubule facilitated diffusion (passive)

- water through aquaporin on both sides

- glucose, amino acids on the basolateral side

proximal tubule paracellular route (passive diffusion)

Cl-, Ca++, K+

HCO3- reabsorption is coupled with H+ secretion

loop of henle ascending limb active transport on basolateral side

Na+/K+ ATPase

loop of henle ascending limb secondary active transport on apical side

- Na+ contransporter (uses the Na+ concentration gradient created by the Na+/K+ ATPase)

- K+ and Cl- into cell with sodium

- diffusion of Cl- and K+ on basolateral side

loop of henle descending limb facilitated diffusion (passive)

water through aquaporin

distal tubule active transport

Na+/K+ ATPase

distal tubule secondary active transport

- Na+ contransporter

- Cl- moves into cell as Na+ goes down concentration gradient

distal tubule facilitated diffusion (passive)

- water through aquaporin on both sides

aldosterone release in distal tubule is caused by:

1. low systemic BP

2. low plasma sodium

3. high plasma K+ concentration

limit of reabsorption

all substances reabsorbed via transport proteins (facilitated diffusion) is limited by the number of transport protein present

transport maximum

the maximum amount of a given solute that can be transported by the renal tubule

renal threshold

plasma concentration of solute at which the substance starts to appear in the urine

osmolarity

a measure of solute concentration

isosmotic

equal osmolarity

hyposmotic

relatively lover osmolarity

hyperosmotic

relatively higher osmolarity

where does countercurrent mechanisms occur

loop of henle and vasa recta

(establishing salt gradient in medulla surrounding LOH and vasa recta)

countercurrent

exists when fluids flow in opposite directions in parallel and adjacent tubes

1. 2 limbs of LOH

2. 2 limbs of vasa recta

3. descending LOH and ascending LOH

4. descending vasa recta and ascending vasa recta

establishing a salt gradient

countercurrent multiplication

- a process that uses energy to create an osmotic gradient (salt)

countercurrent exchanger

- a process where osmotic gradient is maintained

osmolarity in proximal tubule

isosmotic compared to blood

osmolarity in distal tubule

hyposmotic compared to blood

descending LOH with osmolality

- freely permeable to water

- impermeable to NaCl

- water leaves with osmosis

- water picked up by vasa recta

- osmolarity increases as going down LOH

ascending LOH with osmolality

- impermeable to water

- makes medulla salty

- actively pumps out Na, Cl, and K

- filtrate osmolarity decreases as it moves up the ascending LOH

countercurrent multiplier

multiplication because ascending LOH actively pumps ions into the medulla without any water, decreasing osmolarity, becoming hyposmotic by the time filtrate leaves LOH

- descending is mostly solute reabsorption

- ascending is mostly water

- in the medulla is osmolarity gradient is maintained

countercurrent exchanger

the vasa recta preserve the medullary gradient while reabsorbing water and solutes

urine concentration hormonal control

ADH from posterior pituitary

H2O with urine concentration

increase of ADH:

- aquaporin on the apical membrane of collecting duct

- increase water reabsorption

- osmolarity of filtrate increases as moving down CD

release of ADH causes:

- low systematic BP

- high blood osmolarity

- high blood concentration of Na+

Urea with urine concentration

- increase of ADH increases urea absorption at CD

- strengthens medullary osmotic gradient

diabetes insipidus

- insufficient production of ADH (neurogenic DI)

- insensitivity of nephrons to ADH (nephrogenic DI)

symptoms: excessive urination, dilute urine, thirst