1_HST110 Intro to Kidney Structure and Function 2017 Flashcards
Homeostasis: The maintenance of relatively stable internal (X) under fluctuating (Y)
X = physiological conditions Y = environmental conditions
List 4 primary functions of the kidney
- Regulate water and electrolyte balance
- Excrete metabolic waste products and foreign substances
e. g. urea, creatinine, uric acid, drugs - Regulate acid-base balance
- Produce and secrete hormones
- Renin (regulation of blood pressure)
- Calcitriol (active form of vitamin D)
- Erythropoietin (red blood cell production)
What is the first step in production of urine?
Glomerular filtration
Glomerular filtrates include roughly everything present in blood except for what two things?
Blood cells and large molecules (e.g. proteins)
Secretion of unwanted substances involves either simply leaving the substance in filtrate or to a lesser extent (X)
X = Active secretion into the urine
Reabsorption of useful components of the filtrate (e.g. Na+, water, other electrolytes) back into the bloodstream is highly (X) to maintain what 3 types of balance?
X = Regulated
Fluid, electrolyte, and acid-base
What structures sit on top of the kidneys?
Adrenal glands
What is the port into/out of the kidney?
Hilum
What arteries feed into the hilum?
Abdominal aorta to renal artery
What veins leads away from the hilum?
Renal vain to inferior vena cava
What is the approximate size of a kidney?
12x6x4 cm (computer mouse) 0.5% of body weight, 125-170 (M) or 115-155 (F) grams
Which kidney is slightly larger?
Left is larger
What is a calyx?
Cup or receptacle features to collect urine (minor and major)
What is the tip of the renal pyramid called?
Papilla
The renal pyramid forms what border in a segmented fashion?
Corticomedullary border
What are the two major anatomical divisions of the kidney?
Cortex and medulla
The kidneys receive what percentage of cardiac output?
20-25%
Kidneys have the highest blood flow per weight for delivery of oxygen & nutrients as well as filtration and clearance. What is this blood flow?
400 mL/100g/min
Compared to heart and liver (70 mL/100g/min each)
Trace the renal circulation from the abdominal aorta to the inferior vena cava
Abdominal aorta - renal artery - interlobar arteries - arcuate arteries - interlobular arteries - afferent arterioles - glomerular capillaries - efferent arterioles - peritubular capillaries - (vasa recta) - interlobular veins - arcuate veins - interlobar veins - renal vein - inferior vena cava
How many nephrons are there in the kidney?
1.0 - 1.3 million, varying vastly
Name the 5 structures composing the nephron
Renal corpuscle (glomerulus+Bowman’s capsule), Proximal Tubule, Loop of Henle, Distal Tubule, Collecting duct system
Renal corpuscle is made up of a (X) layer of cells
X = single
The Glomerulus is surrounded by a layer of epithelial cells called (X) capsule. Blood filtered by the glomerular capillaries enters into (X) space, which then empties the filtrate into the (Y) of the nephron
X = Bowman’s Y = tubules
What are the 3 layers to the glomerular filtration barrier?
Capillary endothelial cells (fenestrated, 50-100nm)
Glomerular basement membrane (GBM)
Pococytes
Capillary endothelial cells are fenestrated with 50-100nm holes. They are freely permeable to (X)
X = water, solutes, and most proteins in the blood but not blood cells or platelets
GBM: Gel-like meshwork of (X) and (Y). Limits the passage of intermediate to large sized molecules and is (Z) charged, which repels (Z) charged proteins such as albumin
X = Glycoproteins Y = Heparan Sulfate Proteoglycans Z= negatively
What is another name for the podocyte?
Visceral epithelial cells (0f Bowman’s capsule)
Podocytes have long finger-like (X) that surround the outer surface of glomerular (Y)
X = foot processes Y = capillaries
Foot processes interdigitate and are separated by gaps called (X) bridged by a (X) diaphragm with a pore size of (Y)
X = filtration slits Y = 4 to 14 nm
Filtration slits function primarily as (X)-selective barriers and prevent proteins and macromolecules from entering Bowman’s space
X = size
What is the mesangium composed of?
Mesangial cells and mesangial matrix
What are the 6 functions of the mesangial cells?
- Share properties with smooth muscle cells
- Provide structural support for glomerular capillaries
- Secrete extracellular matrix
- Phagocytize cells
- Secrete prostaglandins and proinflammatory cytokines
- May influence glomerular filtration
What 3 structures comprise the juxtaglomerular apparatus?
Macula densa (– (“dense spot”) specialized cells of the thick ascending limb that pass between the afferent and efferent arterioles)
Extraglomerular mesangial cells
Granular cells of the afferent arteriole – produce, store, and release the hormone renin
The JGA is on component of the (X) involved in regulating renal blood flow and glomerular filtration rate
X = tubuloglomerular feedback mechanisms
Each tubule is made up of (X) of epithelial cells, separated by (Y), resting on a tubular basement membrane
X = a single layer Y = tight junctions
Nearly all tubular epithelial cells possess a primary cilium at their apical surface, which may play a role in sensing (X)
X = urine fluid flow
What is the first tubule segment, continuous with the Bowman’s capsule consisting of a coiled segment (X) followed by a straight segment (Y), which extends towards the medulla?
Proximal Tubule
X = proximal convoluted tubule Y = proximal straight tubule
The proximal tubule reabsorbs what percentage of the glomerular filtrate?
55-60% (65-70% by other estimates)
What is the primary site of NaCl and water reabsorption in the nephron?
Proximal tubule
At their apical membrane, proximal tubule cells have a (X) with numerous microvilli that increase surface area to optimize the reabsorption of solutes and water. This is the only tubule segment with this feature
X = brush border
Cytoplasm of proximal tubule cells contain numerous (X) needed for active transport processes
X = mitochondria
Name the 3 segments of the Loop of Henle
Thin descending limb
Thin ascending limb
Thick ascending limb
What percentage of filtered NaCl is reabsorbed by the LOH?
25-35% (15-25% by other estimates)
The LOH plays a critical role in what function of the kidney?
Concentration of the urine
What percentage of filtered NaCl is reabsorbed by the Distal Convoluted Tubule?
~5%
What is the primary site for regulation of calcium in the kidney?
Distal Convoluted Tubule
The collecting duct is divided into what 2 structures?
Cortical and medullary collecting ducts
The cortical collecting duct consists of what cells with which functions?
Principal cells - reabsorption of NaCl and secretion of K+
Intercalated cells - regulate acid-base balance
The medullary collecting duct is responsible for regulation of transport of water and urea under the influence of what hormone?
ADH
The Proximal Tubule Reabsorbs what percentage of filtered substances from the glomerular filtrate?
NaCl and water
HCO3-
Glucose & Amino Acids
65-70%
90%
Almost all
What other electrolytes and molecules does the PT reabsorb?
K+, PO43-, Ca2+, Mg2+, urea, uric acid
What is the major site of ammonia production in the nephron?
Proximal Tubule
The LOH participates in (X) to produce a concentrated urine
X = countercurrent exchange
What is the major site of active regulation of Mg2+ excretion?
LOH
Name the 3 key features of the cortical collecting duct
Principal cells: reabsorb Na+ and Cl-, secrete K+
Intercalated cells: secrete H+, reabsorb K+, secrete HCO3-
Reabsorbs water in presence of ADH
What is the final site of modification of the urine?
Medullary collecting duct
What is reabsorbed and secreted in the medullary collecting duct?
Reabsorbs NaCl
Reabsorbs water and urea, depending on presence of ADH
Secretes H+ and NH3
The efferent arteriole forms what type of capillaries in the juxtamedullary nephrons that are not formed in the cortical nephrons?
Vasa recta
Peritubular capillaries are formed in both
Where do efferent fiber (TO the kidney) originate?
Sympathetic nerve fibers originating in the celiac plexus (T10-L2)
Does the kidney have parasympathethic innervation?
No, just sympathetic
What are the effects of sympathetic nervous stimulation of the kidneys?
Cause vasoconstriction
Increase tubular Na+ reabsorption
Stimulate renin secretion by granular cells of the JGA
What 2 types of receptors are found in the afferent (sensory) fibers (FROM the kidney)?
Baroreceptors in interlobular arteries and afferent arterioles respond to changes in perfusion pressure
Chemoreceptors in the renal pelvis respond to high extracellular levels of K+ and H+
What are the 3 renal processes and what is the formula for urinary excretion derived from these processes?
Filtration, Reabsorption, & Secretion
Urinary Excretion = Filtration - Reabsorption + Secretion
