Flashcards in Renal Chapter 1: Renal Functions, Anatomy, and Basic Processes Deck (55)
Describe the kidney's function in regards to regulation of water and electrolyte balance.
balance when inputs/outputs are matched. difference between input/output leads to increase/decrease in substance.
(drink water when thirsty but its also a part of foods...) kidneys respond by varying the output of water in urine.
Minerals (Na, K, Mg) components of foods, have more than enough in body.. kidneys excrete minerals at rate that matches input.
Describe the kidney's function in regards to excretion of metabolic waste.
bodies form end products of metabolic substances that have little purpose mostly and can be harmful at high concentrations:
urea (from protein)
uric acid (from nucleic acids)
creatinine (from muscle creatine), the end products of hemoglobin breakdown, metabolites of various hormones
Describe the function of the kidney in regards to excretion of bioactive substances that affect body function.
drugs and hormones in blood are removed in many ways, mostly in the liver, but a number are removed in parallel by renal process.
(physicians have to be mindful of how fast drugs are excreted in order to prescribe a dose that achieves the appropriate body levels)
Describe the kidney's regulation of blood pressure.
bp depends on blood volume, kidney's maintenance of Na and water balance achieves regulation of blood volume.
Thus, through volume control, kidneys participate in bp control
-they also generate vasoactive substances that regulate smooth muscle in peripheral vasculature
Describe the kidney's regulation of RBC production.
kidney is major source of erythropoietin (a peptide hormone that is involved in control of RBC production by bone marrow) erythropoietin stimulates bone marrow to increase production of erythrocytes.
(liver also excretes some small amounts)
renal cells that secrete erythropoietin are a particular group of cells in the interstitum.
What will stimulate the kidneys to secrete erythropoietin?
How does this relate to renal disease?
stimulus for secretion is a reduction in partial pressure of O2 in kidneys (anemia, arterial hypoxia, and inadequate renal blood flow) erythropoietin stimulates bone marrow to increase production of erythrocytes
one consequence of renal disease can be dimished erythropoietin secretion
Describe the kidney's regulation of vitamin D production.
In vivo vitamin D synthesis involves a series of biochemical transformations, the last of which occurs in the kidneys. The active form of vitamin D (1,25 dihydroxyvitamin D3) is actually made in the kidneys, and its rate of synthesis is regulated by hormones that control calcium and phosphate balance.
Describe the kidney's role in gluconeogenesis.
CNS always needs glucose.
Whenever the intake of carbs is stopped for much more than half a day our body begins to synthesize glucose (glucogenesis) from noncarb sources (amino acids from protein and glycerol from triglycerides) most occurs in liver but a substantial fraction occurs in kidneys (esp. during prolonged fast)
What is the basic way that kidneys carry out its functions?
involves transporting water and solutes between blood flowing through the kidneys and the lumina of tubules (nephrons and ocllecting tubules)
Lumen of nephron is topologically outside the body and any substance in the lumen that is not transported back into the blood is eventually excreted in the urine
Where are the kidneys? Describe their anatomic location.
lie outside the peritoneal cavity close to the posterior abdominal wall, 1 on each side of the vertebral column. Each is bean shaped. Rounded outer convex surface of each faces the side of the body. Indented surface (hilum) is medial.
Describe the hilum of the kidney.
indented surface of the bean shaped structure. faces medially.
each hilum is penetrated by a renal artery, renal vein, nerves, and a ureter, which carries urine out of the kidney to the bladder
Describe the ureter.
Ureter penetrates hilum of kidney.
each ureter is formed from funnel like structures called major calyces, which in turn are formed from minor calyces.
What are papilla?
Minor calyces fit over underlying cone-shaped renal tissue called pyramids. Tip of each pyramid is called a papilla and projects into a minor calyx.
What do the calyces do?
calyces act as collecting cups for urine formed by the renal tissue in the pyramids.
How are pyramids arranged in the kidney? What do they form?
Pyramids are arranged radially around the hilum with the papillae pointing toward the hilum and the broad bases of the pyramids facing outside, top and bottom of the kidney.
Pyramids constitute the medulla of the kidney.
What overlies the medullary tissue? What overlies that?
cortex, and covering the cortical tissue on the very external surface of the kidney is a thin, connective tissue capsule
What do tubules and blood vessels form?
working structure of both the cortex and medulla is constructed almost entirely of tubules (nephrons and collecting tubules) and blood vessels (capillaries and capillary-like vessels).
They are arranged in parallel arrays or intertwined.
between tubules and blood vessels in interstitum
Describe the interstitum.
Between the tubules and vessels is an interstitum.
contains fluid and scattered interstitial cells that synthesize an extracellular matrix of collagen, proteoglycans and glycoproteins
(comprises less than 10 percent of renal volume)
Describe some structural differences between the cortex and the medulla.
cortex has a highly granular appearance (absent in medulla)
each medullary pyramid is divisible into an outer zone (adjacent to the cortex) and an inner zone, which includes the papilla
Describe where urine formed by kidney goes.
Describe/draw kidney structure.
collects in renal pelvis, flows through ureter into bladder, then is eliminated in urethra
The outer portion
(cortex) contains all the glomeruli. The collecting ducts form a large portion of the inner kidney (medulla),
giving it a striped, pyramid-like
appearance, and these drain into the renal pelvis. The papilla is in the inner portion of the medulla.
Describe the nephron. How many/ what does it consist of?
1 million nephrons in each kidney
each nephron consists of a spherical filtering component, called the renal corpuscle and a tubule extending from the renal corpuscle
renal corpsule is responsible for the initial step in urine formation (a separation of protein-free filtrate from plasma)
Draw the relationships of component parts of a long-looped nephron.
See printout/p 15 book
(Combination of glomerulus and Bowman's capsule is the renal corpsule.
What does the renal corpsule consist of?
the glomerulus, or glomerular capillaries, surrounded by a balloon like hollow capsule: Bowman's capsule
Blood enters and leaves Bowman's capsule through arterioles that penetrate the surface of the capsule at the vascular pole.
fluid filled space (urinary space or Bowman's space) exists within the capsule.
Refer to figure 1-3 p 16
Describe the layers in the filtration barrier in the renal corpsule.
Describe distinguishing characteristics of each layer.
Describe path of filtrate.
What is the functional significance?
-capillary endothelium of glomerular capillaries
-thick basement membrane
-single-celled layer of epithelial cells
first layer, endothelial cells of capillaries is perforated by many large fenestrae ("windows") freely permeable to everything except RBC and platelets
middle layer- gel like meshwork of glycoproteins and proteoglycans
third layer - has podocytes (has pedicels or foot processes that embed in basement membrane... interdigitate wtih pedicels from adjacent podocytes
(filtrate, once through the endothelial cells and basement membrane, travels through the space in between pedicels to enter Bowman's space)
this anatomic arrangement permits the filtration of large volumes of fluid from the capillaries into Bowman's space but restricts filtration of large plasma proteins such as albumin.
Describe the layers of tubule and how they are linked together.
single layer of epithelial cells resting on basement membrane
tight junctions between adjacent cells
Draw a structure of connecting nephrons beginning with the renal corpsule (Bowman's capsule and glomerulus).
The pathway taken by fluids flowing within a nephron always begins in the cortex (in Bowman’s capsule), descends into the medulla (descending limb of the loop of Henle), returns to the cortex (thick ascending limb of the loop of Henle), passes down into the medulla once more (medullary collecting tubule), and ends
up in a renal calyx. Each renal calyx is continuous with the ureter, which empties
into the urinary bladder, where urine is temporarily stored and from which it is intermittently eliminated. The urine is not altered after it enters a calyx. From this point on, the remainder of the urinary system serves only to maintain the fluid composition established by the kidney.
proximal convoluted tubule drains Bowman's capsule
consists of coiled segment: proximal convoluted tubule, followed by a straight segment, the proximal straight tubule, which descends toward medulla
proximal straight tubule drains to descending thin limb of Henle's loop.
ascending thin limb of Henle's loop- beyond this, the epithelium thickens, then have thick ascending limb of Henle's loop which rises back to cortex.
end of thick ascending is macula densa then have beginning of distal convoluted tubule. connecting tubule, cortical collecting tubule
How does blood enter each kidney? (Cortex and medulla)
(Where are these arteries never found?)
enters through renal artery
(divides into interlobar, arcuate, and interlobular arteries)
afferent arterioles branch off interlobular and lead to glomerulus
(these arteries are found ONLY in cortex, never medulla)
20% plasma (no erythrocytes) entering glomerulus is filtered from glomerulus into Bowman's capsule and 80% is left to flow on to the next vascular segment
medulla receives less blood... no glomeruli in medulla. efferent arterioles from juxamedullary glomeruli do not branch into peritubular capillaries but instead descend downward into the outer medulla where they divide into parallel vessels called vasa recta
How are glomerulus capillaries different from most?
in most organs, capillaries recombine to form the beginning of venous system but the glomerular capillaries instead recombine to form another set of arterioles called efferent arterioles.
Thus, blood enters each glomerulus through a single afferent arteriole
and leaves via a single efferent arteriole at the vascular pole of Bowman’s capsule
Describe the vasa recta.
Blood supply to medulla.
The beginnings of the descending vasa recta are like arterioles, with pericytes containing smooth muscle in their walls, but become more capillary like as they descend (see Figure 1–6). The ascending vasa recta have a fenestrated endothelium
like that found in the glomerular capillaries. Therefore, the vasa recta,
in addition to being conduits for blood, also participate in exchanging water and
solutes between plasma and interstitium