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29 Cards in this Set
- Front
- Back
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What are the functions of the kidneys?
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excretory:
-removal of wastes and foreign chemicals homeostatic: -regulation of water and inorganic ions balance -regulation of body fluids osmolarity and volume -regulation of pH -regulation of arterial blood pressure Metabolic: -gluconeogenesis Endocrine: -renin, EPO, 1,25 D3 (vit D) |
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Where is the kidney located?
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lumbar region of abdominal cavity, retroperitoneal organ
between T12-L3 right kidney lower than left |
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What are the tissues surrounding the kidneys and what is on the inside of the kidney?
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1. Fibrous capsule of kidney
2. Perirenal fat 3. Anterior and posterior layers of renal fascia Inside: -renal pelvis, cortex, and medulla -cortex and medulla = parenchyma |
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What is the pathway for the drainage of urine?
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nephron --> collecting ducts --> papillary duct (renal pyramid) --> minor calyx --> major calyx --> renal pelvis --> ureter --> urinary bladder
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What is the nephron and what are its components?
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morpho-functional unit of kidneys
components: -renal corpuscle (glomerulus and bowman capsule) -renal tubule Cortical nephrons: -make up 70-80 % -glomeruli located in outer cortex -short loop of henle -capillaries form network around renal tubules Juxtamedullary nephrons: -located near medulla -long loop of henle in medulla -capillaries form specialized vasa recta - role in formation of concentrated urine |
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What is the epithelium composed of in the nephron?
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Proximal tubule:
-simple cuboidal epithelial cells -apical membrane: brush border -baso lateral membrane with numerous mitochondria Thin descending and ascending limbs: -simple squamous -poorly developed apical and baso-lateral surfaces -few mitochondria Thick ascending limb and distal tubule: -simple cuboidal and low columnar -extensive infolding of baso lateral membrane -abundant mitochondria distal convoluted tubule: -simple cuboidal collecting duct: -simple cubodial -principal cells: moderately invaginated baso lateral membrane, few mitochondria, receptors for ADH and aldosterone -intercalated cells: high density of mitochondria; role in pH Inner medullary collecting duct: -poorly developed surfaces -few mitochondria |
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What are the components of the Juxtaglomerular apparatus?
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macula densa (MD) - in thick ascending limb, sensor of tubular fluid flow rate
extraglomerular mesangeal cells (EGM) granular cells - produce renin, in afferent and efferent arterioles, juxtaglomerular cells |
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What is the structure of the renal corpuscle?
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Parietal layer - outer wall of capsule:
-simple squamous with reticular fibers Visceral layer - inner wall of capsule: -contains modified cells call podocytes -podocytes have pedicles that embrace the capillaries, wrap around single endothelial layer of glomerular capillaries Endothelium or fenestrated capillaries: -large pores -allow each solute including plasma proteins to pass -NO blood can pass Basement Membrane: -fusion of endothelial and epithelial basement mebranes -DOES NOT permit filtration of plasma proteins Tubular Epithelium of Bowman's capsule: -podocytes attached to basement membrane -small pores -permits smaller materials such as water, glucose, AA, ammonia, urea, and small proteins like albumin |
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What is characteristic of innervation of the kidneys?
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ONLY sympathetic innervation
supply: -vasoconstriction of smooth muscles of renal blood vessels -renin secretion (granular cells) -Na reabsorption (renal tubule) |
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What are the basic renal processes?
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Glomerular filtraiton:
-movement of water and solutes from glomerular capillaries to bowman's capsule Tubular reabsorption: -movement of water and solutes from tubular fluid into blood Tubular secretion: -movement of solutes from blood into tubular fluid Excretion: -movement of water and solutes from kidney into bladder filtered + secreted - reabsorbed = excreted |
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What is the fundamental renal equation and how it handles different substances?
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Equation:
amount filtered + amount excreted - amount reaborbed = amount excreted filtration only: -excretion = filtration -substances that MUST be cleared from blood (ex. waste) Filtration + partial reabsorption: -excretion is less than filtration -electrolytes Filtration and complete reabsorption: -no excretion -nutrients filtration + secretion: -excretion is HIGHER than filtration |
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What are some values of Renal Blood Flow (RBF)?
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Kidney weight = 0.4 % of total body weight
Blood flow: -1250 mL/min -1800 L per day -25 % of Cardiac Output Distribution: -Cortex = 85-90 % -Cortico medullary junction = 10 % -Medulla (through vasa recta capillaries) = 1-2 % -Arterio-venous shunts = 3 % |
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What are some functions of the Renal blood supply?
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glomerular capillary bed:
-high pressure bed -ultra filtration of fluid peritubular capillary system: -low pressure bed -extremely porous -absorption of ISF |
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What is the correlation between filtration of solutes and size?
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electrolytes and small organic compounds are freely filtered as much as water
filterability of small proteins approaches 0 |
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What are some electrical properties of the glomerular filtration barrier?
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large solutes - the charge affects filtration
small solutes - the charge DOES NOT affect filtration removal of negative charges = proteinuria |
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What are characteristics of the glomerular ultrafiltrate?
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no cellular elements
protein free iso-osmotic to plasma 125 mL/min = GFR (105 in females): -amount of filtrate formed in all the renal corpuscles of both kidneys per unit time 600 mL/min = RPF Filtration fraction (the proportion of renal plasma that is filtered) = GFR / RPF: -normal value = 20 % |
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What are the Starling Forces in the GF?
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Hydrostatic P of blood in glomerular capillaries:
-55 mm Hg -favors filtration Hydrostatic P of ultrafiltrate in Bowman's space: -15 mm Hg -Opposes filtration Oncotic Pressure of blood in glomerular capillaries: -opposes filtration -mean value = 30 mm Hg oncotic pressure of ultrafiltrate: -negligible Net Flitration P = 55-15-30 = 10 mm Hg Net ultrafiltration pressure always favors filtration |
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What are some regulations of RBF and GFR?
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Autoregulation (intrinsic control):
-maintain its blood flow -respond to change in mean renal arterial P between 85-200 mm Hg --DO NOT regulate urine flow -prevent large changes in GFR dude to changes in BP Extrinsic control: -afferent and efferent arteriolar constriction by SNS -when severe disturbance: mainly effect on afferent arterioles (lower RBF and GFR which increases blood flow to other organs and lowers urine output |
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What are the two types of autoregulation?
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Myogenic autoregulation:
-controls smooth muscle contraction in afferent arterioles in response to changes in renal perfusion P process: increase stretch of arterial wall --> opening of Ca channels --> contraction of smooth muscle cells --> increased resistance leading to decrease blood flow Tubuloglomerular Feedback: -is overall selective control of afferent arterioles in response to distal tubule fluid and solute flow -increase renal AP --> increase RBF and hydrostatic P --> GFR --> increase rate of fluid flow in renal tubule --> increase rate of solute delivery to macula densa in JGA --> activation of macula densa cells which form and release ATP and ADP --> activation of purinergic receptors on mesengeal and smooth muscle cells of afferent arterioles --> afferent arteriole constriction |
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What happens in constriction of efferent and afferent arterioles?
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afferent --> decrease GFR and RPF
efferent --> decrease RPF, increase GFR |
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What are some extrinsic regulations of RBF?
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Catecholamines - similar effects as SNS
Angiotensin II: -Low levels - constriction of efferent arteriole (lowers RBF but increases GFR and hydrostatic P) -High levels (ex hemorrhage) - constriction of both afferent and efferent (lowers RBF and GFR) Atrial Natriuretic Peptide (ANP): -dilation of afferent arterioles but constriction of efferent arterioles Prostaglandins: -cause vasodilation of both afferent and efferent arterioles -counter vasoconstriction by SNS and ATII |
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What is the tubular processing of the ultrafiltrate?
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Reabsorption:
-movement of water and solutes from filtrate in lumen to peritubular capillaries -net reabsorption: filtered load is greater than excretion rate Secretion: -movement of substances in opposite direction -net secretion: filtered load is less than excretion rate filtered load = GFR x Plasma conc of X (Px) Excretion rate = Urine flow rate (V) x Urine conc. of X (Ux) |
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What are the 2 pathways of movement of water and solutes?
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Paracellular pathway:
-between cells through "leaky" tight junctions -passive diffusion -solvent drag - movement of water drags solutes with it Transcellular pathway: -through the cell -passive diffusion (lipid soluble) -endocytosis -facilitated diffusion |
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What is Primary Active transport and examples?
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primary active transport through the baso-lateral membrane (Na+/K+ ATPase pump)
passive diffusion through the apical membrane |
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What are examples of Secondary Active Transport?
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Co-transport:
-AA & glucose reabsorption -glucose and AA diffuse passively from cell into ISF Counter-transport: -secretion of H+ |
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What is the Transport Maximum and properties of it?
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maximum amount of a given solute that can be transported per minute by renal tubules
characteristics: -carriers are easily saturated and have a high affinity for the substrate -low back leak Mechanism: -saturation as tubular load increases Importance: -when it is reached, increase in substance concentration in plasma --> doesnt change reabsorption or secretion Lack of Tm (ex. Na+): -time gradient transport |
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What is threshold concentration?
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the plasma concentration of a solute in the plasma at which it begins to appear in the urine
High threshold: (ex. glucose, AA, Vit C) -completely reabsorbed at normal plasma level Low threshold (HPO4, Na+): -not completely reabsorbed and always present in urine No threshold substances (creatine and urea): -are not reabsorbed actively |
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What is the pathway for the Kidney blood supply?
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Renal artery --> segmental artery --> interlobar arteries --> arcuate arteries --> interlobular arteries --> afferent arteries --> glomerular capillary --> efferent arterioles -->
peritubular capillary --> interlobular veins --> arcuate veins --> interlobar veins --> segmental veins --> renal vein |
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What are examples of threshold subtances?
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Glucose
Na-Glucose transport across apical membrane GLUT 1 and GLUT 2 glucose carrier on the baso-lateral membrane |
