HOMEOSTASIS—RENAL STRUCTURE & FUNCTION Flashcards
cortex
outer portion of the kidney and vascular
–>which contains an arterial network, all of the glomeruli, a dense peritubular capillary plexus, and a venous drainage system.
medulla
inner kidney which receives much less blood than the cortex and contains the collecting ducts.
pyramids
medulla
cone-shaped
where urine is formed
minor/major calyces
helps form ureter
act as collecting cups for the urine formed in the pyramids.
renal pelvis
funnel for urine
through the minor and major calyces –> pelvis–> ureter –> bladder –> urethra
renal interstitium
lies between tubules and blood vessels; <10% of renal volume; contains fluid and scattered interstitial cells (fibroblasts and others) that synthesize an extracellular matrix of collagen, proteoglycans, and glycoproteins
Is the loop of Henle located in the medulla or cortex?
Medulla
Afferent arteriole
Blood supply to kidneys. Takes blood into the glomerulus to be filtered
Efferent arteriole
Takes blood away from the kidneys
Bowman’s capsule
surrounds glomerulus
Contains a parietal and a visceral layer of stellate cells that are called podocytes
Glomerulus
A cluster of capillaries that brings blood into the kidney for filtration
What forms the Juxtaglomerular apparatus (JGA)?
distal convoluted tubule + the afferent arteriole= JGA
What is the function of the JGA?
Regulates blood pressure and the glomerulus filtration rate
distal convoluted tubule = epithelial Macula densa cells that detect sodium levels
afferent arteriole =specialized granular cells that secrete renin. Renin regulates blood pressure
What composes the convoluted tubule?
Proximal; Distal; thick and thin look of Henle
Where is most of the absorption occuring?
Proxmial convoluted tubule
What does the distal convoluted tubule mostly absorb?
Na
What is the Thick Ascending loop of Henle permable to?
Thick Ascending loop of Henle- Permeable to solute and not to water
What is the Thin Ascending loop of Henle permable to?
Thin descending loop of Henle- Permeable to water and not to solutes
Why is Thick Ascending loop of Henle signficant?
Critical role in creating an osmotic gradient and concentration of solute in urine
major excretory and non-excretory functions of the kidney
1) Regulation of Water and Electrolyte Balance
2) Excretion of Metabolic Waste
3) Excretion of Bioactive Substances That Affect Body Function
4) Regulation of Arterial Blood Pressure
5) Regulation of Red Blood Cell Production
6) Regulation of Vitamin D Production
7) Gluconeogenesis
What stimulates the bone marrow to increase its production of red blood cells ?
erythropoietin –> made in kidney
What types of molecules are easily filtered by the kidney? Difficult molecules to filter?
easy passage of small molecules
most proteins, large molecules and medium-large highly negatively charged particles more difficult.
Kidney Secretion
Molecules that do not filter through the glomerulus pass on into the efferent renal arteriole to the peritubular capillaries which surround the renal tubules. From there the molecule may be secreted into the tubular lumen where they are either excreted or reabsorbed.
Significance of the GFR equation
grading progression/improvement of chronic kidney disease and for dosing drugs which are primarily excreted via urine
low GFR= poor kidney function
Who has a higher TBW: males or females?
MALES: females typically have higher percentage of adipose tissue than males, they tend to have less body water
females= 55%
males 60% of body weight
How much of TBW is in ECF vs ICF?
1/3 TBW= ECF; 2/3 TBW=ICF
Intracellular fluid (ICF):
The water inside the cells in which all intracellular solutes are dissolved.
Extracellular fluid (ECF):
The water outside the cells.
Major cations in ICF =
Major cation in ECF = sodium (Na+)
Major anions in ECF =
Major anions in ECF = chloride (Cl-) and bicarbonate (HCO3-)
What is most abundant ion in ECF?
Na (Sodium)
ECF subcompartments are?
1) Plasma (intravascular fluid) 2) Intersitital fluid
Plasma (intravascular fluid):
The fluid that circulates in the blood vessels. The aqueous component of blood. The fluid in which the blood cells are suspended
Interstitial fluid:
The fluid that actually bathes the cells. An ultrafiltrate of plasma, formed by filtration processes across the capillary wall; contains very little if any protein
How much of ECF is Intersitial fluid and plasma?
3/4 Intersitial fluid ; 1/4 Plasma (intravascular fluid)
Water balance is regulated by
thirst and ADH (anti-diuretic hormone)
Role of ADH
ADH released from the hypothalamus –>stimulates water conservation in the nephron be stimulating more water reabsorption in the collecting duct.
What contributes most to water intake?
Water content in food
Discuss “third-spacing”
the movement of body fluid to a non-functional space, i.e. outside of the extracellular (i.e. intravascular, interstitial) and intracellular spaces
–> not easily moved back into ECF or ICF
Examples of third-spacing
Pleural Effusion; Ascites
Ascites vs. interstitial edema
Ascites: fluid accumulation in the peritoneal cavity.
Interstitial edema: fluid accumulation in the tissues/spaces between cells
Ascites is most commonly due to
portal hypertension
Common causes for interstitial edema
1) decreased osmotic pressure (not enough albumin to keep water in)
2) Increased venous hydrostatic pressure: e.g. heart failure, sodium retention -> hypervolemia
3) Increased vascular permeability: e.g. inflammation
4) Blocked lymphatic drainage: e.g. parasitic infection (can you say filariasis?), cancer growing in lymphatics
Osmosis
diffusion of water across a selectively permeable membrane –> water moves to the area of higher concentration
Osmolarity (osmol/L) or Osmolaity (osmol/kg)
osmotic concentration –> higher osmolarity of a solution, the lower the water concentration
Tonicity
Refers to the ability of a solute to cross a membrane and affects volumes of cells or a compartment
Hypertonic
cell = SHRINK
Hypotonic
cell = SWELL
Isotonic
No net water movement
Discuss sodium’s role in volume homeostasis
Hypervolemia reflects sodium retention Hypovolemia reflects sodium deficiency
REMEMBER: water follows sodium
Na function
1) influences the degree of water retention in the body and participates in the control of acid-base balance.
2) Regulates ECF water balance, maintains blood volume, transmitting nerve impulses and contracting muscles (Muscle contractility).
Na regulation
ALDOSTERONE!
1) glomerulo-tubular balance
2) Atrial natriuretic factor- induces Na+ excretion by decreasing Na+ reabsorption - get rid of Na+
3) Antidiurtic hormone (ADH) – Produced by the hypothalamus when there is an increase in plasma [Na+]. Promotes reabsorption of water in the kidney.
K function
cell cycle regulation
muscle excitability
ICF water balance
K regulation
plasma K
Aldosterone
nephron tubular rates
HCO3- function
Acts as an extracellular buffer for acid-base balance; determinant of pH
HCO3- regulation
primarily regulated by the kidneys and some at liver
Ca2+ function
stored in bone membrane excitability bone formation coagulation hormone actions
CA2+ regulation
Alteration of intestinal absorption is the main way Ca++ is regulated. 1) Parathyroid hormone 2) Vitamin D 3) calcitonin 4)pH
What is the most abdundant intracellular cation
K+
How is K regulated by renal function and secretion?
Aldosterone –> ATPase pump –> K out/ Na in
Aldesterone increases membrane permeability to K+ –> stimulates the sodium-potassium ATPase pump –> facilitates passage of Na+ through channels= secretion of K+ into the renal tubular lumen for excretion. (Na in and K out)
What are the effects of K on serum pH?
Serum pH – If pH decreases, plasma [K+] increases
Insulin/Epinephrine both stimulate?
Both stimulate the entry of potassium (K+) into the cells.
What is the Most abundant mineral in body?
Ca2+
How does parathyroid regulate Ca2+?
raises blood [Ca++] by promoting intestinal absorption and increased renal tubular reabsorption=increasing plasma [Ca++].
How does vitamin D regulate Ca2+?
increasing Ca++ uptake in the intestines and kidney
How does calcitonin regulate Ca2+?
acts the opposite of parathyroid hormone and causes bone uptake of Ca++, reducing plasma [Ca++]
How does pH regulate Ca2+?
Decreased pH decreases Ca++ binding to plasma proteins
H+ function
pH determinant
H+ regulation
1) diet
2) metabolic production of CO2
3) GI
4) Buffers
Cl- function
maintains fluid and electrolyte balance and is and an important component of gastric juice
Cl- regulation
high bicarbonate= low Cl-
PO4-3 (Phosphate) function
- Important in the structure of bones
- structure and functioning of all cells and DNA.
PO4-3 (Phosphate) regulation
1) Vitamin D- increase phosphate with increase of Ca++ absorption
2) Parathyroid- inhibits renal reabsorption of phosphate at proximal tubule
Most common extracelluar anion?
Cl-
Clinical Feature, Lab Assessment and Tx: Hyponatremia
Clinical: low NA ion concentration ;
Lab Assessment: urine sodium, fena, osmolaity; Tx: if hypervolemic→diuretics & fluid restriction; if hypovolemic→saline; if euvolemic→ fluid restriction, perhaps saline plus loop diuretics.
Clinical Feature, Lab Assessment and Tx: Hyperonatremia
Clinical: too much Na concentration;
Lab Assessment: Hx + PE, urine osm, serum osm, urine Na Tx: determine if chronic or acute; Calculate TBW deficit; can give oral water or IV.
Clinical Feature, Lab Assessment and Tx: Hypokalemia
Clinical: Parasthesias, muscl cramps or weakness, ileus, cardiac arrhythmia, ECG: flat T waves, ST depression;
Lab Assessment: Hx + PE, FeK chemistries;
Tx: Potassium supplementation (oral or IV depending on severity).
Clinical Feature, Lab Assessment and Tx: Hyperkalemia
Clincal: Parasthesias, muscle weakness, cardiac arrest. ECG: peaked T waves, PR prolongation, QRS widening;
Lab Assessment: Hx + PE, chemistries, urine potassium excretion.;
Tx: CaGluconate IV for cardiac stabilization; bicarbonate; beta agonist, insulin/ glucose. Potassium removal via urine or stool.
Clinical Feature, Lab Assessment and Tx: Hypocalcemia
Clinical: Tetany, muscle spasm, cramps, seizures, arrhythmia, hypotension, and bradycardic.;
Lab Assessment: Mg, PTH, Vit D levels,
Phos level.; Tx: Depends on severity and acuity; IV or Hypo Ca.
Clinical Feature, Lab Assessment and Tx: Hypercalcemia
Clinical: “stones, bones, groans, psychiatric overtones”; HTN, GI symptoms, MS changes, polyuria, kidney stones.;
Lab Assessment: PTH; Phos; Vit D level; Tx: increase urinary excretion of Ca (loop diuretic/ saline); if in renal failure consider dialysis
Clinical Feature, Lab Assessment and Tx: Hypermagnesemia
Clinical: weakness, N/V, decreased respirations, HTN, arrhythmia & asystole, decreased or absent tendon reflexes, bradycardia;
Lab: Chemistries serum Mg levels;
Tx: IV CaGluconate, IV diuretics, dialysis
Clinical Feature, Lab Assessment and Tx: Hypophosphatemia
Clinical: Decreased GI absorption (malnutrition, Vit D deficiency, malabsorption, binders); myalgia, weakness, rhabdomyolysis, MS changes
Lab: Chemistries;
Tx: Treat by repleating
Clinical Feature, Lab Assessment and Tx: Hyperphosphatemia
Clinical: Decreased renal excretion; hypocalcemia, tetany, metastatic soft tissue calcification, secondary hyperPTH.;
Lab: chemistries;
Tx: cellular shifting and elimination
Role of Erythropoietin
an essential hormone for red cell production
osmoregulation is primarily regulated by?
ADH
the concentration of what ion determines ECF volume?
Sodium
