Week 13: Chp 61: Renal System Flashcards
What is the Renal System Composed of?
two kidneys
What is the Urinary system composed of?
two ureters, the urinary bladder, and the urethra
The Renal system and the Urinary System work together to do what?
help maintain homeostasis in the human body
ex: urine is formed as blood is filtered through the kidneys; the bladder then provides storage, and the ureters and urethra act as passages for urine to exit the body
Functions of the kidney regarding maintenance of homeostasis in the human body
- Excretion of wastes
- Regulation of fluid and electrolyte balance
- Regulation of acid-base balance
- Regulation of blood pressure
- Secretion of erythropoietin for red blood cell (RBC) production
- Activation of vitamin D
Function of the Urinary System
provides for the storage (bladder) and passage of urine, promoting continence and facilitating voiding
Kidneys
bean-shaped organs located retroperitoneally (behind the abdominal contents), one on each side of the spinal column
- held in place by connective tissue known as renal fascia
- left kidney is located slightly higher than the right because of the position of the liver
- an adrenal gland sits atop of each organ
The Outermost layer of the kidney
renal capsule
- thin, fibrous tissue serves to protect the organ and absorb shock
- capsule covers the distal surface of the kidney and extends to the medial portion of the kidney termed hilum
Hilum
indented part of the kidney
- medial portion of the kidney
- the location at which the renal artery and nerves enter the organ and the renal vein and ureters exit
Parenchyma
the inner tissue of the kidney
-lies beneath the renal capsule and contains the functional layers of the organ
When the parenchyma is viewed as a cross-section, the tissue layer laying directly beneath the renal capsule is called?
the cortex
The medulla
innermost layer of tissue and is composed of multiple pyramids
Papillae
the narrow tips of the renal pyramids
-empty urine into the calyces, cuplike collection structures
Minor Calyx
small cluster cuplike collection structures that papillae empty out into
-minor calyces, when moving toward the hilum, merge to form major calyces, which empty into the larger collection sac known as the renal pelvis
Major Calyces
what minor calyces merge into when moving toward the hilum
-major calyces then empty into the larger collection sac known as the renal pelvis
Renal pelvis
where the major calyces empty into
- can hold only 3 to 5 mL of urine
- narrows to become the ureters
The Flow of Urine
papillae of the pyramids into the minor calyces, the major calyces, the renal pelvis, and the ureters en route to the bladder
Nephron
functional unit of the kidney
-here is the work of filtering the blood to remove wastes and produce urine occurs
>80% are cortical nephrons; short in length and fully contained within the cortex region
>20% are juxtamedullary nephrons and contain structures that lie deep within the medulla
Each Nephron is Composed of What?
glomerulus, a Bowman’s capsule, and a tubular system
Nephron: Glomerulus
collection of semipermeable capillaries responsible for filtering blood
Nephron: Bowman’s capsule
structure surrounding each glomerulus
Nephron: Tubular system
composed of the proximal convoluted tubule (PCT), the loop of Henle, the distal convoluted tubules (DCTs), and a collecting tubule
>the PCT emerges from the bowman’s capsule and winds until straightening into the loop of Henle; The loop of Henle is composed of a descending and an ascending limb, each of which is responsible for reabsorbing different substances in the process of urine formation; the DCT is a continuation of the ascending limb of the loop of Henle that thickens and continues twisting until it widens further into a collecting tubule
Blood Supply of the Kidneys
receive 20 to 25% of cardiac output/ 1200 mL of blood per minute
-the renal artery, a branch of the abdominal aorta, enters the kidney at the hilum and delivers blood to the kidney; as the renal artery enters the kidney, it branches into several segmented arteries which then branch into interlobar arteries
Interlobar arteries
travel through the renal columns between the pyramids, moving outward toward the renal cortex tissue
-as they approach the renal cortex, they divide, forming arcuate arteries and then cortical radiate arteries; the branches formed off these cortical radiate arteries are the afferent arterioles
Afferent Arterioles
the branches formed off the cortical radiate arteries
- afferent arterioles for a collection of capillaries that direct blood flow to the glomeruli of the nephrons, where the process of urine formation begins
- capillaries within the glomeruli then merge into efferent arterioles to transport blood away from the glomeruli and into the peritubular capillaries
Efferent arterioles
transport blood away from the glomeruli and into the peritubular capillaries
Peritubular Capillaries
this collection of capillaries drains blood into the venous system
-the renal vein then carries blood away from the kidneys and drains into the inferior vena cava
Urine formation is formed through a continuous process of?
filtration, reabsorption, secretion, and concentration
Glomerular Filtration
begins as blood is filtered across the semipermeable membrane of the glomerulus
- occurs non-selectively based on particle size
- the membrane filters particles primarily by their size
- the capillary pores do not normally allow large particles such as plasma proteins and blood cells to pass through the membrane; however, in conditions that increase capillary membrane permeability (i.e. diabetes mellitus and renal failure), plasma proteins and blood cells may escape through the membrane and into the urine
Process when blood enters the capillaries of the glomerulus
glomerular filtrate is formed via hydrostatic pressure, which forces electrolytes, water, and small particles such as urea nitrogen, creatinine, and glucose from the blood across the glomerular membrane into the bowman’s capsule
- the glomerular filtrate or ultrafiltrate then flows from the bowman’s capsule into the PCT, where it is termed tubular filtrate
Glomerular filtration rate (GFR)
amount of blood filtered by the glomeruli in a set amount of time
normal: 125 mL/min
>the reabsorption that occurs beyond the glomerulus returns much of this volume to the body
>1 to 3 L of filtrate is excreted as urine each day
Glomerular filtration rate is dependent on several factors
- systemic blood pressure
- blood flow
- blood volume
The kidneys have the ability to change the pressure within the glomerular capillaries through what?
the dilation and constriction of the afferent arterioles that direct blood into the glomerulus and the efferent arterioles that guide blood away from the glomerulus
the constriction of the afferent arterioles and dilation of the efferent arterioles leads to what?
decreased pressure within the glomerular capillaries and a decreased filtration rate
Dilation of the afferent arterioles or constriction of the efferent arterioles results in?
increased glomerular capillary pressure and an increased filtration rate
Tubular reabsorption
second phase of urine production
- movement of water and solutes from the tubular filtrate back into the blood
- accomplished through both active and passive transport
- the kidneys allow for selective reabsorption of certain substances to occur within the tubular system
- to avoid dehydration, up to 99% of the glomerular filtrate is reabsorbed and returned to the blood, mainly in the PCT; PCT responsible for reabsorbing 65% of the glomerular filtrate
What hormones control the permeability of the DCT membrane?
aldosterone and antidiuretic hormone (ADH)
Aldosterone
hormone secreted from the adrenal cortex that increases the reabsorption of sodium in the DCT
-because water follows sodium, the reabsorption of water is also increased
Maximum amount of glucose kidneys can reabsorb
“renal threshold” or “transport maximum”
-220 mg/dL (meaning that all at blood glucose levels of 220 or less, all glucose is bound to the transport proteins and returned and reabsorbed in the blood; at higher levels, the transport proteins become saturated, resulting of presence of glucose in the filtrate and subsequently in the urine
Tubular Secretion
third phase of urine formation
-movement of solutes from the blood into the filtrate
-substances move from the capillaries into the renal tubule cells and then into the urine to be excreted from the body
>substances: potassium ions (k+) and hydrogen ions (H+); both are secreted back into the filtrate in quantities necessary to maintain stable electrolyte and blood Ph levels
Urine Concentration
following tubular secretion, the urine must be concentrated prior to its excretion from the body; without the kidneys ability to concentrate the urine, the body would quickly experience dehydration due to large volume losses
-loop of Henle plays a major role in this; the descending portion is permeable to water and is responsible for reabsorbing the additional water required to concentrate the urine
What is the major organ responsible for maintaining water balance within the body?
the kidneys
For fluid balance to be maintained the kidneys must ensure what?
that the volume of water taken into the body is equal to the volume of water lost from the body
Water is taken in through the body from what?
liquids and foods
-water is also present in the body as a product of metabolism
Water losses occur through what?
perspiration (water from sweat glands), urination, defecation, cutaneous transpiration (water loss through the epidermis), and exhalation
Osmolality
measure of the concentration of solutes including electrolytes and ions, contained in the blood
-the osmolality of the fluid inside the cells and the fluid outside the cells is nearly equal because water is allowed to pass freely along the cell membrane
>when less water is taken into the body, the osmolality increases because the solutes are more concentrated as a result of the decreased water content
>when excess water is taken into the body, serum osmolality decreases because the excess water dilutes the concentration of solutes
What is capable of detecting changes in the osmolality of the blood?
the hypothalamus
Homeostasis: What happens when serum osmolality increases because of dehydration?
the brain is stimulated to produce the sensation of thirst
-it also increases the release of ADH (antidiuretic hormone) from the posterior pituitary gland; ADH regulate water balance by altering the permeability of the tubular membrane, making it more permeable to water and resulting in the increased absorption of water
Homeostasis: what happens when serum osmolality decreases when excess water is taken into the body
the secretion of antidiuretic hormone is suppressed
-the kidneys then produce more dilute urine to rid the body of excess water and to restore serum osmolality
Kidneys: Electrolyte balance
kidneys reabsorb and secrete electrolytes to maintain levels within normal ranges
- the PCT is responsible for reabsorbing up to 80% of the electrolytes contained in the filtrate
- the rate of reabsorption and secretion of each electrolyte is dependent on the concentration of that electrolyte in the serum
ex: when a higher-than-normal electrolyte is detected, the kidneys act by increasing the secretion of this electrolyte; when a specific electrolyte level is lower than normal, the kidneys increase the reabsorption of that electrolyte to restore homeostasis
Example of homeostasis of electrolyte balance regarding low sodium
the release of the hormone aldosterone from the adrenal cortex is stimulated when serum levels of sodium are decreased (hyponatremia), causing increased reabsorption of sodium (Na+) in the distal tubule
-as a result, sodium is reabsorbed, increasing serum sodium levels; water is also reabsorbed
Example of homeostasis of electrolyte balance regarding high potassium
in hyperkalemia, aldosterone is secreted, resulting in excretion of k+, making more potassium in the urine
Acid-Base Balance
to maintain homeostasis the pH of the blood must constantly remain between 7.35 and 7.45
- less than 7.35 = acidosis
- greater than 7.45 = alkalosis
Kidneys role in acid-base balance
renal regulation of pH is the last mechanism to activate but,
- in instances of acidosis, the kidney tubules excrete H+ and reabsorb bicarbonate ions (HCO3) to increase serum pH to normal level
- in cases of alkalosis, the kidney tubules reabsorb H+ and excrete HCO3 to decrease pH to normal levels
What is the only organ that is able to fully excrete h+ from the body?
the kidneys
Kidneys are responsible for producing what hormones?
renin, erythropoietin, activated vitamin D, bradykinin, and PGs (prostaglandins)
Renin
aids in blood pressure regulation within the body
- it is produced and released when receptors in the kidneys sense a decrease in blood flow, volume, or pressure
- renin is also released when decreased levels of sodium in the renal blood supply are detected
What happens in the release of renin
(renin-angiotensin-aldosterone system)
- upon release, renin interacts with angiotensinogen released from the liver to produce angiotensin I, which, with the aid of angiotensin-converting enzyme (ACE) secreted from the lungs, results in the formation of angiotensin II
- angiotensin II restricts blood vessels, resulting in increased blood pressure
- in addition, angiotensin II stimulates the adrenal glands to release aldosterone; aldosterone causes increased sodium reabsorption and subsequent water reabsorption in the DCT
- angiotensin II also stimulates the hypothalamus to stimulate thirst
what hormone is produced by the kidneys in response to decreased renal blood flow and hypoxia?
erythropoietin
- erythropoietin stimulates the bone marrow to produce RBCs
- in cases of renal impairment and failure, erythropoietin is produced in insufficient quantities, and a resulting anemia occurs
Vitamin D
obtained through diet and exposure to ultraviolet radiation, but must be activated in order for it to be useful to the body
-the kidneys turn vitamin D to its active form, but is first started in the liver
The steps for activation of Vitamin D in the body
begins in the liver, where vitamin D is converted to calcidiol, then continues to the kidneys, where calcidiol is converted to its active form, 1,25-dihydroxycholecalciferol or calcitriol
- the activated form of vitamin D is required for calcium to be absorbed in the GI tract
- a patient with renal impairment can have deficiencies in activated vitamin D, and as a result decreased serum calcium levels
- because of the inverse relationship between calcium and phosphate, serum phosphate is typically increased in patients with renal impairment
relationship between calcium and phosphate
they have a inverse relationship
- when calcium is increased, phosphate is low
- when calcium is decreased, phosphate is high
Activated Vitamin D is needed for what?
the activated form of vitamin D is required for calcium to be absorbed in the GI tract
Prostaglandin
hormones produced by various tissues of the body
- typically affect the tissues surrounding their site of production
- the kidneys produce prostaglandin E2 and prostacyclin; these PGs function within the kidneys to trigger vasodilation, resulting in increased blood flow to the kidneys and increased sodium and water excretion
- prostaglandins synthesized in the kidneys may also play a role in lowering systemic blood pressure as a result of decreasing vascular resistance
What prostaglandins do the kidneys produce?
prostaglandin E2 and prostacyclin
- these function within the kidneys to trigger vasodilation, resulting in increased blood flow to the kidneys and increased sodium and water excretion
- prostaglandins synthesized in the kidneys may also play a role in lowering systemic blood pressure as a result of decreasing vascular resistance
As the quantity of functional kidney tissue decreases in renal failure, the production of prostaglandins also decreases. the absence of the vasodilating effects of PGs may be a contributing factor to what?
the development of hypertension associated with renal failure
Bradykinin
a hormone released by the kidneys in response to the presence of prostaglandins (PGs), ADH, and angiotensin II
-it increases the permeability of the capillary membrane to certain solutes and dilates the afferent arteriole to ensure adequate reabsorption of solutes and blood flow to the kidneys
The nurse expects to observe which of the following altered laboratory values in a patient diagnosed with renal failure? A. Decreased Calcium B. Increased Calcium C. Decreased phosphorus D. Increased Hematocrit
A. decreased calcium
in addition to a increase in phosphorus because of their inverse relationship
