Physiology Of Kidneys(physiology) Flashcards
(32 cards)
List 5 functions of the kidneys
-Role in homeostasis
-Regulation of BP
-Haematopoietic function
-Excretion of waste
-Calcium homeostasis
What are the two types of nephrons, state the differences.
•Cortical nephron:
-Has a short loop of henle.
-Glomeruli is in the outer cortex.
•Juxtamedullary nephron:
-Has a large glomeruli
-Has a long loop of henle
-Glomeruli is in the corticomedullary junction
-Has juxtaglomerular apparatus for renin secretion.
What is the diff btwn the blood supply of cortical nephron and juxtamedullary nephron?
-Cortical:- has afferent and efferent arterioles as well as peritubular capillaries.
-Juxtamedullary- Has vasa recta in addition to those arteries of cortical nephron.
In which blood vessels does blood flow from the renal arteries to renal veins
Renal arteries—Segmental arteries—Interlobar artery—Arcuate artery—Interlobar artery—Afferent arteriole—Glomerulus—Effrerent arteriole—Peritubular capillaries(cortical) /—Vasa recta(juxta)—Interlobar vein—Arcuate vein—Interlobar vein—Renal veins.
What are the functions of a nephron(6)
•Production of filtrate.
•Excretion
•Reabsorption of water and ions.
•Reabsorption of all organic nutrients.
•Secretion of waste into tubular fluid.
•Modification of fluid volume and osmolarity.
How much fluid is filtrated per day
180 litres
The filtration membrane of the nephron consists of:(3)
-Capillary endothelial cells
-Basement membrane
-Tubular epithelial cells
What perpetuates the glomerular filtration?
Glomerullar capillary pressure (hydrostatic pressure)
How much of the plasma goes for glomerular filtration and how much is excreted?
-80%, less than 1%
Why can’t proteins get filtered into the convoluted tubules?
Because the bowman’s capsule has negatively charge glycoproteins which repels with the plasma proteins.
The basement membrane consist of three layers namely:
Lamina rara interna- fused to endothelium
Lamina densa
Lamina rara externa- fused to epithelium
What is the function of lamina densa?
Counts the number of sodium ions moving past to the distal convoluted tubule.
What cells are found in the epithelium of the filtration membrane, that is attached to the BM?
Podocytes
What three types of pressure affects glomerular ultrafiltration? What role do each play?(3)
•Glomerular capillary pressure (pressure exerted by blood on glomerular capillaries)- promotes filtration
•Hydrostatic pressure in the bowman’s capsule (exerted by the filtrate)-opposes filtration
•Colloid osmotic pressure (Exerted by plasma proteins)- Against filtration
What equation is used to calculate the net filtration pressure?
Net filtration pressure= Glomerular capillary pressure - Colloid osmotic pressure - Hydrostatic pressure
What is meant by Glomerular Filtration Rate (GFR)?
Total quantity of ultrafiltrate formed in both kidneys per unit time.
Two factors that influence the GFR
Net filtration pressure
Filtration coefficient
Two ways in which renal blood flow (RBF) can be regulated
Autoregulation
Non-renal factors
Explain the myogenic response theory of autoregulation
•Stretch of the afferent arteriole smooth muscle cell wall (e.g. high BP), this cause pressure gated ion channels to open, muscle depolarizes, voltage gated calcium channels open.
•Huge influx of calcium ions inside the cells.
•Muscle contraction and increased resistance, caused decrease in RBF and filtration pressure.
•Blood pressure decreases, relaxation of afferent arteriole, GRF also decreases.
Explain the tubuloglomerular feedback theory of autoregulation of RBF
-GRF increases
-Flow through tubules increases.
-Flow past the macula densa increases.
-Paracrine from macula densa causes afferent arteriole to constrict.
-Increased resistance in afferent arteriole.
-Hydrostatic pressure decreases.
-GRF decreases.
What are the non-renal factors affecting RBF?(2)
Hormones and autonomic neurons
Intergrated centers outside kidney can override local controls.
What are the factors causing vasoconstriction, which can affect the RBF
•Sympathetic nerves and catecholamines
•Angiotensin 2, endothelins, thromboxane A2, ADH.
Factors causing vasodilation which can affect the RBF
High GFR and naturesis.
Glococorticoids, prostaglandins, cAMP
Factors affecting the filtration coefficient
•Hormones can act on podocytes
-Causes change in glomerular filtration slits.
- If wider slits, high surface area, high GFR.
•Contraction of mesangeal cells (in endothelial cells of glomeruli)
-Less sa for filtration, GFR decreases.
