Human Anatomy/Physiology Chapter 24
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We know that the kidneys are the most important excretory organs in the body. They remove substances from the body. What are they? Pg. 426
- 1.) nitrogenous waste.
- 2.) water.
- 3.) electrolytes.
- 4.) toxins.
- 5.) drugs.
What maintains the normal volume and composition of body fluids? Pg. 426
What are the four major organs of the urinary system? Pg. 426
- 1.) kidneys.
- 2.) ureters.
- 3.) urinary bladder.
- 4.) urethra.
List three urinary system terms. Pg. 426
- 1.) renal (latin for kidney).
- 2.) nephr (greek for kidney, nephrology)
- 3.) Urology (study of the urinary system.)
Where are the kidneys specifically located? Pg. 426
The kidneys are located high on the posterior wall of the abdominal cavity, behind the parietal peritoneum (retroperitoneal).
What protects and cushions the renal? Pg. 426
The kidneys are cushioned and protected by the renal fascia, adipose tissue pads, and the lower rib cage.
What is the indentation of the bean-shaped renal called?
Hilus. It is the point where the blood vessels, ureter, and nerves enter and exit the kidney.
What are the three distinct regions of the kidney? Pg. 427
- 1.) renal cortex.
- 2.) renal medulla.
- 3.) renal pelvis.
What is cone-shaped and combines to form the renal medulla? Pg. 427
What is each renal medulla (or renal pyramid) separated by? Pg. 427
What do the lower ends of the renal pyramids point towards and what does it do? Pg. 427
The lower ends of the pyramids point toward the renal pelvis, a basin that collects the urine made by the kidney and helps form the upper end of the ureter.
What is apart of the renal pelvis and lies between the main area of the pelvis and the renal medulla (or renal pyramid)? Pg. 427
Renal calyx (plural: calyces.) It collects the urine formed in the kidney.
How is the blood sent to the kidneys? Pg. 428
Blood is sent to the kidney by the renal artery which arises from the abdominal aorta.
Blood leaves the kidneys through the renal vein. Where does the renal vein empty the blood? Pg. 428
Inferior Vena Cava (IVC)
The renal nerves travel with the renal blood vessels to the kidney. What do the nerves accomplish? What type of nerves are they? Pg. 428
The nerves are primarily sympathetic nerves that help control blood flow to the kidney and regulate the release of renin (a blood pressure-controlling substance).
The general functions of the kidneys are to cleanse the blood of waste products, help regulate the volume and composition of body fluids, and help regulate the pH of body fluids. List some specific tasks in which the kidneys perform? Pg. 428
- 1.) Excrete nitrogenous waste such as urea, uric acid, ammonia, and creatinine.
- 2.) Regulate blood volume by determining the amount of water excreted.
- 3.) Help regulate the electrolyte content of the blood.
- 4.) Play a major role in the regulation of acid-base balance (blood pH) by controlling the excretion of hydrogen ions (H+).
- 5.) Play a role in the regulation of blood pressure through a secretion of renin.
- 6.) Play a role in the regulation of red blood cell production through the secretion of a hormone called erythopoietin.
Each kidney contains about one million nephron units. What is a nephron? Pg. 428
The nephron is a functional unit, or urine-making unit, of the kidney. Each has two parts: a tubular component (renal tubule) and a vascular component (blood vessels).
Where do are the renal tubules located and name two tubules that make up the renal tubule? Pg. 428
The renal tubules are located within the nephron unit and the nephron unit is located within a renal pyramid, which itself creates the renal medulla with other pyramids
Two tubules are:
- 1.) Proximal convoluted tubule.
- 2.) Distal convoluted tubule.
List the structures in which the urine travels through while travel to the collecting duct. Pg. 428
Glomerulus -> Bowman's capsule -> Proximal convoluted tubule -> descending limb -> Loop of henle -> ascending limb -> distal convoluted tubule -> collecting duct.
List the structures in which blood travels through when entering/exiting the nephron unit.
renal artery -> afferent arteriole -> glomerulus -> efferent arteriole -> peritubular capillaries -> venule -> larger veins -> renal vein.
What is urine initially and why does it change finally being something different? Pg. 428
Urine is formed in he nephron units as water and dissolved substances move between the vascular and tubular structures.
What are the three processes involved in the formation of urine within the nephron unit? Pg. 428
- 1.) Glomerular filtration.
- 2.) Tubular reabsorption.
- 3.) Tubular secretion.
We know that urine initially forms within the nephron units, but where in the nephron unit specifically? Pg. 430
Urine formation begins in the GLOMERULUS and BOWMAN'S CAPSULE.
What does glomerular filtration, one of the three processes involved in the formation of urine, do? Pg. 430
Glomerular filtration causes water and dissolved substances to move from the glomerulus into Bowman's capsule.
Why does filtration occur within the glomerulus? Pg. 430
Filtration occurs when the pressure on one side of a membrane is greater than the pressure on the opposite side. Blood pressure in the glomerulus is higher than the pressure within Bowman's capsule. It is this pressure difference that provides the drive force for filtration. This pressure difference is called the glomerular filtration pressure.
What substances are filtered within the glomerulus? Pg. 430
The wall of the glomerulus contains pores and acts like a sieve or a strainer. The size of the pores determines which substances can move across the wall from the glomerulus into Bowman's capsule. Small substances such as water, sodium, potassium, chloride, glucose, uric acid, and creatinine move through the pores very easily. These substances are filtered in proportion to their plasma concentration. In other words, if the concentration of a particular substance in the plasma is high, much of that substance is filtered. Large molecules such as red blood cells and large proteins cannot fit through the pores and therefore remain within the glomerulus. The water and the dissolved substances filtered into Bowman's capsule are called the glomerular filtrate. Note that the glomerular filtrate is protein-free; the presence of protein in the urine indicates abnormal nephron function (abnormally large holes in the glomerulus.
What are the substances that are filtered from the glomerulus into the Bowman's capsule? Pg. 430
Those substances, including water, are called GLOMERULAR FILTRATE.
The glomerular filtration, like anything else in nature, occurs at a certain rate. What is used to describe the rate of glomerular filtration? Pg. 430
Glomerular Filtration Rate (GFR).
Each kidney approximately filters 180 L of liquid each day, but only about 1.5 L of liquid, or urine, are excreted. What happens to the 175.5 L? Pg. 430
Most of the glomerular filtrate is reabsorbed in the kidney and returned to the circulation.
What is the process called where glomerular filtrate moves from the renal tubules into the blood of the peritubular capillaries? Pg. 430
Knowing that tubular reabsorption has filtrate move from the tubules to the peritubular capilaries, where does move of the reabsorption occur? Pg. 430
Move occurs in the proximal convoluted tubule.
What is reabsorbed into the kidneys and what are excreted? Pg. 430
The kidney chooses the type and quantity of substances it reabsorbs. Some substances, such as glucose, are completely reabsorbed. For example, the amount of glucose filtered is the same as the amount of reabsorbed, so glucose normally does not appear in the urine. Some substances are incompletely reabsorbed. For instance, over 99% of water and sodium is reabsorbed, whereas only 50% of urea is reabsorbed. Some waste products such as creatinine are not reabsorbed at all. Those substances not reabsorbed remain in the tubules, becoming part of the urine.
What are two types of transports occur within tubular reabsorption within the kidneys? Pg. 430
The reabsorption of substances by the kidney also varies with the mechanism of reabsorption. Absorption occurs through either ACTIVE or PASSIVE TRANSPORT.
What are diuretics? Pg. 430
Diuretics are drugs that increase the production of urine. The excess secretion of urine is diuresis.
What is tubular secretion? Pg. 430
Almost most of the water and dissolved substances enter the tubules because of filtration across the glomerulus, a second process moves very small amounts of substances from the blood into the tubules.
How do hormones affect kidneys? Pg. 431
Several hormones act on the kidney to regulate water and electrolyte excretion. Thus these hormones play an important role in the regulation of blood volume, blood pressure, and electrolyte composition of body fluids.
List five hormones that have a significant impact on the function of the kidneys. Pg. 431
- 1.) Aldosterone
- 2.) Atrial natriuretic peptide (ANP)
- 3.) Brain natriuretic peptide (BNP)
- 4.) Antidiuretic hormone (ADH)
- 5.) Parathyroid hormone (PTH)
Where is the hormone aldosterone released, where does it primarily act within the kidney, and what does it do? Pg. 431
Aldosterone is secreted by the adrenal cortex. It acts primarily on the distal tubule of the kidney, and it stimulates the reabsorption of sodium and water and the excretion of potassium.
Why is aldosterone called the "salt-retaining" hormone? Pg. 431
It is called the "salt-retaining" hormone because of its effect on salt by having the peritubular capillaries reabsorb them from the tubules, mainly the distal tubule.
What is significantly important about one of the kidney controlling hormones aldosterone that involves blood pressure? Pg. 431
Aldosterone expands or increases blood volume. Because aldosterone increases blood volume, it also increases blood pressure. A deficiency of aldosterone causes severely diminished blood volume, decline in blood pressure, and shock.
What causes the release of aldosterone from the adrenal cortex? Pg. 431
One of the most important stimuli for the release of aldosterone is renin which is an enzyme that stimulates the renin-angiotensin-aldosterone system.
Renin is an important enzyme that causes the release of the hormone aldosterone. Where is renin released and what causes its release? Pg. 431
Renin is secreted by a specialized collection of cells called the juxtaglomerular apparatus, located in the afferent arterioles. The renin-secreting cells are stimulated when either blood pressure or blood volume declines.
List the three basic steps that leads to the release of aldosterone from the adrenal cortex. Pg. 431
- 1.) Renin activates angiotensinogen to form angiotensin I. Angiotensinogen is secreted by the liver and circulates within the blood; angiotensinogen is inactive.
- 2.) An enzyme called converting enzyme acts to change angiotensin I to angiotensin II. (Converting enzyme is found in the blood but is particularly high in the lungs.)
- 3.) Angiotensin II stimulates the adrenal cortex to release aldosterone. The aldosterone, in turn, stimulates the distal tubule to reabsorb sodium and water and to excrete potassium.
In addition to stimulating the release of aldosterone, what else does angiotensin II do? Pg. 431
It is also a potent vasopressor. Angiotensin II causes vasoconstriction and an elevation in blood pressure. Thus the activation of the renin-angiostensin-aldosterone system regulates blood volume and blood pressure.
What class of drugs is used to lower blood pressure? Pg. 431
A class of drugs called ACE inhibitors is used to lower blood pressure. ACE stands for angiotensin-converting enzyme. ACE inhibitors prevent the production of angiotensin II and aldosterone, both of which increase blood pressure.
Which kidney-hormone deals only with water reabsorption? Pg. 431
A second hormone affecting water reabsorption is antidiuretic hormone (ADH).
How does the hormone antidiuretic affect the reabsorption of water? Pg. 431
The action of ADH allows the kidneys to concentrate urine. ADH works primarily on the collecting duct by determining its permeability to water. In the presence of ADH, the collecting duct becomes permeable to water. Water is reabsorbed from the collecting duct into the peritubular capillaries. In other words, ADH decreases the excretion of water and causes excretion of a highly concentrated urine. In the absence of ADH, the membrane permeability of the collecting duct decreases, and water cannot be reabsorbed; the result is excretion of a very dilute urine. Because ADH affects the amount of water excreted by the kidneys, it plays an important role in the determination of blood volume and blood pressure. Excess ADH expands blood volume, while a deficiency of ADH diminishes blood volume.
What is the stimulus for the release of ADH? Pg. 432
- 1.) Decrease in blood volume.
- 2.) Increase in the concentration of solutes in the plasma.
Name to natriuretic pepties. Pg. 432
Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP).
What do the two natriuretic peptides do? Pg. 432
They cause excretion of sodium. This process is called natriuresis. They also decrease the secretion of aldosterone by the adrenal cortex. The effect is decreased sodium and water reabsorption.
Where are the two natriuretic peptides secreted from? Pg. 432
ANP is secreted by the walls of the heart's atria in response to an increase in the volume of blood. BNP is secreted by the walls of the ventricles in response to elevated ventricular pressure.
T/F. Are the effects of natriuretic peptides similar to the effects of aldosterone and ADH?
F. The effects of the natriuretic peptides are opposed to the effects of aldosterone.
Where is the parathyroid hormone secreted and what role does this play? Pg. 433
Parathyroid hormone (PTH) is secreted by the parathyroid glands. It does not affect water balance but plays an important role in the regulation of two electrolytes, calcium and phosphate. PTH stimulates the renal tubules to reabsorb calcium and excrete phosphate. The excretion of phosphate is called the "phosphaturic effect" of PTH.
What is the primary stimulus for the release of PTH? Pg. 433
The primary stimulus for the release of PTH is a low plasma level of calcium.
What is in urine? Pg. 433
Urine is a sterile fluid composed mostly of water (95%), nitrogen-containing waste, and electrolytes. Important nitrogenous waste includes urea, uric acid, ammonia, and creatinine.
What is the yellowish urine color caused by? Pg. 433
The light yellow color of urine is due to a pigment called urochorme, formed from the breakdown of hemoglobin in the liver.
What does oligo mean? Pg. 433
Oligo means "scanty". Oliguria refers to a urine output of < 400ml/24hrs.
What does "specific gravity of urine"? PG. 433
Specific gravity is the ratio of the amount of solute to volume. The specific gravity of urine ranges from 1.001 to 1.035, depending on the amount of solute (substances such as Na+ and creatinine) in the urine.
Does more or less solute increase the "specific gravity"? Pg. 433
The more solute, the higher is the specific gravity.
Do the kidneys filter more or less water when one is dehydrated? And as a result, what happens to the volume of urine? Pg. 433
If a patient is dehydrated, the kidneys filter less water; as a result, the volume of urine decreases. The ratio of solute to volume in the urine therefore increases.
What causes "nephrotic syndrom"? Pg. 435
Nephrotic syndrom is what happens when the pores in the glomerular membrane become too large. Remember: the size of the glomerular pores determines what gets filtered; proteins such as albumin are normally too large to pass through the pores.
How is "nephrotic syndrome" characterized? Pg. 435
Nephrotic syndrom is characterized by the excretion of large amounts of protein in the urine (albuminuria).
What does the loss of protein from the blood result in? Pg. 435
What does the protein albumin do and what are the negative side effects caused to it by nephrotic syndrome? Pg. 435
Albumin results in a shift of water from the blood into the tissue spaces, causing generalized edema and ascites. Nephrotic syndrome can develop in response to different insults: trauma, drugs, infection, chronic diseases such as diabetes mellitus, and collage diseases.
What does "nephrotic syndrome" respond favorably to? Pg. 435
Nephrotic syndrom often responds favorably to steroid (prednisone) therapy; the prednisone decreases the size of the glomerular pores thereby decreasing the glomerular filtration of albumin.
What causes "Glomerulonephritis"? Pg. 435
The glomeruli can be injured in response to an autoimmune reaction to a pathogen, usually the group A beta hemolytic streptococcus. TA person develops a streptococcal throat infection. The person's immune system reponds to the streptococcus in a way that the glomeruli are damaged. The damaged glomeruli cannot function normally and the person experiences heaturia (blood in the urine), albuminuria, edema, and hypertension. As glomerular function declines, GFR decreases and serum creatinine rises (an indication of renal failure). The person develops azotemia, the accumulation of nitrogenous waste such as urea and creatinine. The autoimmune reaction to streptococcus is called glomeruloneprhitis; it may be acute or chronic. NOte! Glomerulonephritis is not an infection and therefore cannot be treated with an antibiotic. What is treatable is the initial streptococcal throat infection. An antibiotic can cure the throat infection and prevent glomerulonephritis. Poststreptococcal glomerulonephritis is preventable.
Is Glomerulonephritis an infection? Pg. 435
No it is not an infection hence can't be treated with an antibiotic.
What is an example of the consequences of renal tubular damage? Pg. 435
Acute Tubular Necrosis (ATN) is an example. A common cause of ATN is a prolonged period of hypotension (as in shock) in which the tubules are deprived of blood and the tubular cells die.
Where is E.coli found and what syndrome is it capable of causing within the kidneys? Pg. 435
Infections, such as E.coli is found in contaminated beef and can destroy the kidneys causing a lethal hemolytic uremic syndrome (HUS).
What is kidney failure called? Pg. 435
Kidney failure is called renal suppression and this is when the kidneys no longer make urine. The blood is not cleansed of its waste, and substances that should have been excreted in the urine remain in the blood. This condition is called uremia, which literally means urine in the blood. Uremia may be prevented with an artificial kidney, a form of dialysis. The artificial kidney consists of a cylinder filled with plasmalike solution called the dialysate. The patient's blood is passed through a series of tiny tubes immersed in the dialysate. Waste products in the blood, such as potassium, creatnine, uric acid, and excess water, diffuse out of the tubules into the dialysate. The blood is thus cleansed of these waste products and returned to the patient. Because this procedure cleanses blood like a kidney, it is called an artificial kidney.
What are two ways to described "blood in the urine"? Pg. 435
Uremia and hematuria.
What is the second form of dialysis? Pg. 436
The second form of dialysis is peritoneal dialysis. With this procedure, the peritoneal cavity of the patient is used as the cylinder of an artificial kidney, and dialysate is infused into the peritoneal cavity. Waste products diffuse from the blood into the dialysate. The dialysate eventually drains out of the periotneal cavity and is discarded.
What is azotemia? Pg. 435
Azotemia is the accumulation of nitrogenous waste such as urea and creatinine.
What do you call the autoimmune reaction to streptococcus? Pg. 435
You call that glomerulonephritis.
What pathogen group usually causes glomerulonephritis? Pg. 435
Group A beta hemolytic streptococcus.
Urine contains nitrogenous-containing waste in addition to 95% water and electrolytes. Name some nitrogenous waste. Pg. 433
- 1.) urea,
- 2.) uric acid.
- 3.) ammonia.
- 4.) creatinine.
What are two electrolytes that the parathyroid hormone regulates? Pg. 433
- 1.) Calcium.
- 2.) Phosphate.
What do you call the excess secretion of urine? Pg. 430
What forms the urinary tract? Pg. 436
The ureters, bladder, and urethra.
Within the four layers that make up the wall of the bladder, which is an involuntary smooth muscle? Pg. 438
The detrusor muscle.
What area within the bladder do most infections persist? Pg. 438
The trigone, which is a triangular area formed by three points: the entrance points of the two ureters and the exit point of the urethra.
Which of the two sphincter muscles near the exit of the bladder is voluntary and mainly assists all in prevent the emptying of the bladder? Pg. 438
The external sphincter muscle which is composed of skeletal muscle and is voluntarily controlled.
List the three ways in which expelling urine from the bladder can be described. Pg. 438
- 1.) Urination.
- 2.) Micturition.
- 3.) Voiding.
What is the micturition reflex? Pg. 438
As the bladder fills with urine, stimulated stretch receptors send nerve impulses along sensory nerves to the spinal cord. The spinal cord reflexively sends motor nerve impulses back to the bladder, causing the bladder wall to contract rhythmically and the internal sphincter muscle to relax. This response is called the micturition reflex.
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