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Dthiery237
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Caylx
a cup of flowers; minor calyx
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detrudere
to push down; detrusor muscle
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fenestra
a window; fenestrated capillaries
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glomus
a ball; glomerulus
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juxta
near; juxtaglomerular aparatus
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micturition
to urinate;micurition
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papillae
small, nipple-shaped projections; renal papillae
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recus
straight;vasa recta
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retro-
behind;retroperitoneal
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Objective:
Identify the components of the urinary system and list their functions (pp.659-660)
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Urinary system performs the vital function of
removing the organic waste products generate by cells throughout the body.
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Functions of the urinary system
- Regulate blood volume and blood pressure
- Regulate plasma concentration of ions
- Help stabilize blood pH
- Conserve valuable nutrients
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Regulate blood volume and Bp
- Adjusting the volume of water lost in urine
- releasing EPO
- releasing renin
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Regulate plasma concentration of ions
- Na+, K+, Cl-, and other ions are regulated by controlling the quantities lost in the urine.
- Plasma concentration of calcium ions is regulated by synthesis of calcitriol.
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Help stabilize blood pH
pH is stabilized by controlling the loss of H+ ions and HCO3-(bicarb) in urine.
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Conserve valuable nutrients
Glucose and amino acids are conserved by preventing their excretion in urine while organic waste products are eliminated
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Organization of urinary system
- Two kidneys, produce urine
- Urine travels through paired uretersto the urinary bladder for temp storageurination occurs, contraction of muscular bladder forces the urine through the urethra and out of the body
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Objective:
Describe the structural features of the kidneys(pp.660-661)
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Kidneys are located
- on either side of the vertebral column between the last thoracic and third lumbar vertebrae.
- The right kidney often sits lower then the left.
- Both lie between the muscles of the doral body wall and the peritoneal lining
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Retroperitoneal refers to
behind the peritoneum
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Position of the kidneys are maintained by
- overlying peritoneum
- contact with adjacent organs
- supporting connective tissue
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Each kidney is covered by
a dense fibrous renal capsule and its packed in a soft cushion of adipose tissue
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Floating kidney
- Damage to the suspensory fibers may cause the kidney to be displaced.
- Dangerous because ureters or renal blood vessels may become twisted of kinked during movement.
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Typical kidney is
reddish brown and about 10 cm long, 5.5 cm wide and 3 cm thick in adults and weighs about 150 g
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Hilum
- indentation that is the site of exit for the ureter
- site which the renal artery and renal never enter and where the renal vein exits
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Renal capsule
covers the surface of the kidney and lines the renal sinus
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Renal sinus
internal cavity within the kidney
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Kidney is divided into
- the renal cotex
- renal medulla
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Renal medulla contains
18 conical renal pyramids, that projects into the renal sinus
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Renal papilla
tip of each renal pyramid
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Renal columns extend toward the
renal sinus between adjacent renal pyramids
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Urine production occurs in the
renal pyramids and overlying areas of the renal cortex
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Ducts within each renal papilla dischare urine into a cup shaped drain called
minor calyx
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Four or five minor calyx merge to form
major calyx
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Renal pelvis
funnel shaped chamber formed by the calyxs
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Renal pelvis is connects to
the ureter through which urine drains out of the kidney
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Urine production begins in the renal cortex, in microscopic tubular structures called
nephrons
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Each kidney has roughly ___ million nephrons
1.25
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Objective:
Trace the path of blood flow through a kidney
(PP.662-63)
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Each minute how many mL of blood flows through the kidneys
1200 mL
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Kidney receives blood from a
renal artery that originates from the abdominal aorta
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As the renal artery enters the renal sinus, it divides into branches that supply a series of _________ _______ that radiate outward between the renal pyramids.
interlobar arteries
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Acruate arteries
arch along the boundary lines between the cortex and medulla
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interloBUlar arteries
supply the cortex given rise from arcuate arteries
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Afferent arterioles
branch from each interlobular artery deliver blood to the capillaties that supply individual nephrons
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Efferent arteriole
Leaves each nephron
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Peritubular capillaries
- recieves blood from efferent arterioles,surround the proximal and distal convoluted tubules
- provide route fro pickup or delivery of substances that are reabsorbed or secreted by these portions of the nephron
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Cortical nephrons
located mostly within the cortex
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Juxtamedullary nephrons
located near the renal medulla
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Blood flow from efferent arterioles differ in
- cortical nephrons
- juxtamedullary nephrons
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In juxtamedullary nephrons, peritubular capillaries are connected to the
vasa recta, long straight capillaries that parallel the loop of henle deep into the medulla
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Juxtamedullary nephrons enable the kidneys to produce
concentrated urine
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blood flow from the peritubular capillaries and vasa recta enters a network of venules and small veins that converge on the
interlobular veins
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Mirror image of arterial supply blood from interlobular veins converge and then empty into the
arcuate , interlobar, and renal veins
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Describe the structure of the nephron and processes involved in urine formation (pp.663-666)
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Nephron
Basic functional unit of the kidney
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Nephron conisists of two main parts
- a renal corpuscle
- Renal tubule composed of two convoluted segments separated by a single U-shaped tube
- Convuluted segments are in the cortex and U shaped tube extends partially or completely into the medulla
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Renal corpuscle
nephron begins here,round structure that consists of a cup shaped chamber (bowman's capsule) that contains a capillary network, or Glomerulus
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Blood arrives at the glommerulus by way of?
Afferent and Efferent arterioles
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In renal corpuscle, blood pressure forces fluid and dissolved solutes out of the glomular capillaries and into tthe surrounding capsular space. this is called
filtration
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Filtrate
Product of filtration, a protein free solution
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From renal corpuscle,filtrate enters the renal tubule. Major segments of the renal tubule are
- Proximal convoluted tubule (PCT)
- Loop of henle
- Distal convoluted tubule(DCT)
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As filtrate travels along the tubule its compositon changesm and then is called
tubular fluid
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Collecting system
- Each nephron empties into a collecting duct
- collecting duct leaves the cortex and descentds into the medulla, and carries tubular fluid from many nephrons toward a papillary duct that delivers the fluid now called urine, into the calyces and on to the renal pelvis
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Renal corpuscle
is the site of filtration
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Filtrate leaves the renal corpuscle and enters the renal tubule. Renal tubule is responsible for
- reabsorbing all of the useful organic molecules from the filtrate
- reabsorbing over 90% of water in the filtrate
- secreting into the tubular fluid any waste products that were missed by the filtration process
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Renal corpuscle consists of
- capillary network of the glomerulus
- structure known as bowmans capsule
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Bowmans capsule
forms the outer wall of the renal corpusvle and encapsulates the glomerular capillaries
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Capsular epithelium makes up the wall of
the capsule and is continious with a specialized epithelium that covers glomerular capillaries
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Capsular space
separates the two epithelia, which revieves the filtrate and empties into the renal tubule.
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Podocytes
epithelium that covers that capillaries consists of sites called podocytes
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Characteristics of podocytes
- long cellular processes called pedicels that wrap around invidual capillaries
- thick basemnet membrane separates cappillaries and podocytes
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Glomeular capillaries are said to be
fenestrated, they contain pores
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To enter the capsular space, a solute must be small enough to pass through
- the pores of endothelial cells
- fibers of basement membrane
- filtration slits between the slender process of the podocytes
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Filtration membrane is composed of
- fenestrated capillary, basement membrane, and filtration slits
- that prevents the passage of blood cells and most plasma proteins but permits water,metabolic wastes,ionsmglucose,fatty acids, vitamens and other solutes into the capsular space.
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Most vaulable solutes will be reabsorbed by the
PCT proximal convoluted tubule
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Filtrate moves from the renal corpuscle to the first segment of the renal tubule called
PCT proximal convoluted tubule
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Cells of the PCT absorb
organic nutrients,plasma proteins and ions from the tubular fluid and release them into the intersitital fluid the surrounds the renal tubule
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As a result of the PCT, solute concentration of the intersitial fluid increases while that of the tubular fluid decreses, water then moves out of the tubular fluid by
osmosis
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Last portion of the PCT sharply bends toward the medulla and connects to the
loop of henle
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Loop is comprised of
descending limb that travels toward the renal pelvis and ascending limb that returns to the cortex
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Ascending limb
- is not permeable to water and solutes actives transports sodium and chloride ions of of the tubular fluid
- as result intersitial fluid of the medulla will contain unusually high solute concentrations
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Descending limb
- permeable to water
- as it descends into the medulla waters moves out of the tubular fluid by osmosis
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Ascending loop of henle ends where it bends and comes in close contact with the glomerulus and its vessels , the ___ begins
DCT begins and its passes immediately adjacent to the afferent and efferent arterioles
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DCT is an important site for
- active secretions of ions,acids,drugs, and toxins
- selective reabsorption of sodium ions from tubular fluid
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In final portions of the DCT osmotic flow of water may assist in concentrationg the
tubular fluid
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Macula Densa
Epithelial cells of the DCT are closest to the glomerulus
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Juxtaglomercular apparatus
- macula densa and juxtaglomerular cells (in the wall of the afferent arteriole)
- endocrine structure secretes hormone EPO and enzyme Renin
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DCT which is the last segment of the nephron, opens up to the
collecting system
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Colleting duct merge to form
a a papallary duct which delivers urine to the minor calyx
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Collecting system makes final adjustments to
composition of urine by reabsorbing water and reabsorbing or secreting sodium,potassium,hydrogen, and bicarbonate ions
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Functions of the nephron and collecting system in the kidney
Renal corpuscle
Filtration of plasma to initiate urine formation
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Functions of the nephron and collecting system in the kidney
Proximal convoluted tube (PCT)
Reabsorbtion of ions,organic molecules, vitamens,water
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Functions of the nephron and collecting system in the kidney
Loop of henle
- descending limb: reabsorption of water from tubular fluid
- ascending limb: reabsorption of ions; creates concentration gradient in the medulla, which enables the kidney to produce concentrated urine
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Functions of the nephron and collecting system in the kidney
Distal convoluted duct DCT
reabsorption of sodium ions;secretiomn of acids, ammonia, drugs
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Functions of the nephron and collecting system in the kidney
Collecting duct
Reabsorption of water and of sodium, and bicarbonate ions
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Functions of the nephron and collecting system in the kidney
Papillary duct
conduction of urine to minor calyx
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Objective:
List and describe the factors that influence filtration pressure and the rate of filtrate formation. (pp.666-668)
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Primary function of urine production is to
maintain homeostasis by regulating volume and composition of the blood
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Homeostatic process of urine production involves secretion of dissolved solutes especially the following three metabolic wastes
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urea
- most abundent organic waste
- generate about 21 grams of urea daily
- most of it during breakdown of amino acids
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Creatinine
- generated in skeletal muscle tissue through the breakdown of creatine phosphate.
- Body generates roughly 1.8 g daily
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Uric acid
- Produced during the breakdown and recycling of RNA
- you generate about 480 mg of uric acid daily
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Kidneys minimize water loss by producing urine that is
4 to 5 times more concentrated then normal body fluids.
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To maintain homeostasis kidneys perform 3 processes
- Filtration
- reabsorption
- secretion
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Filtration
Bp forces water across the filtration membrane in the renal corpuscle
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Reabsorption
- removal of water and soulute molecules from the filtrate and their re entry into the circulation at the peritubular capillaries
- Filtrate occurs after filtrate enters the renal tubule.
- passive through osmosis
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Secretion
is the transport of solutes out of the peritubular epithelium and into the filtrate.
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Kidneys can continue to work efficiently only so long as
- filtration
- reabsorption
- secretion proceed in proper balance
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Filtration occurs exclusively in the
renal corpuscle, across the capillary walls of the glomerulus
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Reabsorption of nutrients occurs primarily at the
PCT
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Active secretion occurs primarily at the
DCT
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Regulation of the amount of water, sodium ions and potassium ions lost in the urine results from interactions between the
loop of henle and collecting system
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Blood pressure at the glomerulus tends to foce water and solutes out of the bloodstream and into the
capsular space
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For filtration to occur
the outward force must exceed any opposing pressures such as osmotic pressure of the blood.
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Filtration pressure is
the net foce that promotes filtration
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Filtration pressure at the glomerulus is higher than cappillary blood pressure elsewhere in the body because
- of the slight difference in the diameters of the afferent and efferent arterioles.
- Efferent are slighly smaller in diameter
- result creates backup that increases BP in glomerular capillaries
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Filtration pressure is very low around
10 mmHg
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If glomerulur pressure falls signifigantly...
kidney function will stop
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Reflexive changes in the diameters of the afferent, efferent arterioles or glomerular capillaries can compensate for
minor variations in blood pressure
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Reninangiotension system is a mechanism that
is one of the mechanims that responsible for regulating BP and blood volume
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Glomerular filtration
process of filtrate production at the glomerulus
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Glomerular Filtration Rate (GFR)
- The ammount of filtrate produced in the kidneys each minute.
- 6 square meters of filtration surface
- GFR averages around 125 mL per min
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Tubular reabsorption is an
extremely important process
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Inability to reclaim watter that enters filtrate is known as
Diabetes insipidus(caused by inadequate ADH secretion)
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Objective:
Describe the changes that occur in the tubular fluid as it moves through the nephron and exits as urine(pp.668-671)
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Reabsorption and secretion in the kidney involve a combination of
diffusion,osmosis, and carrier mediated transport.
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Cells at the PCT actively reabsorb organic nutrients,plasma proteins, and ions from filtrate and then transport them into
intersititial fluid that surrounds the renal tubule
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Osmotic forces pull water from the wall of the PCT into the surrounding intersitial fluid. TJe reabsorbed materials and water diffuse into
peritubular capillaries
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PCT reclaoms what % of the volume of filtrate produced at the glomerulus, along with virtually all of the glucose, amino acidsm and other organic nutrients.
60-70%
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PCT also actively reabsorbs
ions, including sodium,calcium,bicarb,magnesium,phosphate amd sulfate ions
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Ion pumps of the PCT are individually
regulated and may be influenced by circulating ion or hormone levels
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Active secretions into the tubular fluid (like hydrogen) play important role in
regulation of pH,
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What compounds are ignored by the PCT and other segments of the renal tubule
Uric acid and urea
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From the PCT, the loop of henle reabsorbs more then % of remaining water as well as % of sodium and chloride ions that remain in the tubular fluid
half and 2/3
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Descending limb
is permeable to water but not other solutes
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Ascending limb is impermeable to both
water and solutes
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the ascending limb actively pumps
sodiumand chloride ions out of the tubular fluid and into the interstitial fluid of the renal medulla
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concentration gradient at the bend of the descnding limb
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roughly half of the volume of filtrate that enters the loop of henle is reabsorbed in the
descending limb
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Most of the sodium and chloride ions are removed in the
ascending limb
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the filtrate declines to around
1/3 of the concentration of plasma
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By the time filtrate reaches the DCT roughly % of solutes and water have been reabsorbed
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DCT is connected to a collecting duct that
drains into the renal pelvis
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As filtrate passes through the DCT and collecting duct final adjustments are made in its
compostion and concentration, composition depends on the types of solutes present, concentration depends on volume of water in which the soultes are dissolved
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DCT and collecting duct are impermeable to solutes, changes in composition can only occur through
- active reabsorption or secretion
- Primary function of DCT is active secretion
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Throughout most of the DCT , tubular cells actively transport sodium ions out of the tubular fluid in exchange for
potassium or hydrogen ions
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DCT and collecting ducts contain ion pumps that respond to the hormone
Aldosterone, produced in the adrenal cortex
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Aldosterone secretion occurs in response to lowered
sodium ion concentraions or elevated potassium ion concentraions in the blood
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Higher the aldosterone levels the
more sodium ions reclaimed and more potassium ions are lost
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The ammount of water reabsorbed along the DCT and collecting duct is controlled by circulating levels of
ADH
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In absense of ADH the DCT and collecting duct are
impermeable to water
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Higher the ADH, the greater the water permeability and the more
concentraited the urine
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Overview of kidney function and urine formation
step 1
- Glomerular filtration produces a filtrate that resembles blood plasma byt contains few plasma proteins
- filtrate has same osmotic concentration as plasma or intersitial fluid
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Overview of kidney function and urine formation
Step 2
- PCT, 60-70% of water is reabsorbed and almost all of the dissolved nutrients are reabsorbed.
- osmotic concentration of tubular fluid remains unchanged
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Overview of kidney function and urine formation
Step 3
PCT and descending limb of the loop of henle, water moves into the surrounding intersititial fluid and leaves a small fluid volume of highly concentrated tubular fluid (20% of origional flitrate)
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Overview of kidney function and urine formation
Step 4
- Ascending limb of henle, impermeable to water and solutes
- tubular cells actively pump Na+ and Cl- out of tubular fluid
- because Na+ and Cl- are removed urea accounts for a greater proportion of the solutes in the tubular fluid
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Overview of kidney function and urine formation
Step 5
- DCT and collecting duct determine final composition and concentration
- these segments are impermeable to solutes but ions may be actively transported into or out of the filtrate under the control of hormones such as aldosterone
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Overview of kidney function and urine formation
Step 6
- Concentration of urine controlled by variations in water permeability of the DCT and collecting ducts
- Segments are impermeable to water unless exposed to ADH
- absence of ADH= no water reabsorption occur, produces diluted urine
- High concentrations of ADH= collecting ducts become freely permeable to water and produces small volume of conentraited urine.
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Clinical note: Acute renal failure
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Acute renal failure (ARF)
is a deteriroation in renal function over hours or days that causes the accumulation of toxic wastes and causes the loss of internal homeostasis
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ARF usually results from
a decline in blood flow
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Prerenal failure
result from lack of bloodflow to the kidney
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intrinsic renal failure
Problem with the kidney itself
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Postrenal failure
problem in urine flow
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Depressed renal blow flow and substances that are toxic to the kidney cause
renal cell ischemia and death
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recovery depends upon
restoration of renal blood flow
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Objective:
Discuss the process of urination and how it is controlled (pp.672-674)
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Normal kidney function depends on adequate
glomerular filtration rate (GFR)
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GFR is regulated three ways
- By local automatic adjustments in glomerular pressure
- through activities of the sympathic devision of the ANS
- throught the effects of various hormones (hormonal mechanisms result in long term adjustments)
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Local, automatic changes in the diameters of the afferent arterioles,efferent arteroles and the glomerular capillaries can compensate for
- minor variations in blood pressure
- for example reducation in blood flow and decline in glomerular filtration pressure trigger dialtion of afferent arteriole and glomerular capillaries and constrict efferent arteriole
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Autonomic regulation of kidney function occurs primarily through the
sympathetic division of the ANS
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Sympathetic activation has what types of effects
direct and indirect
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direct effects of the sympathetic division
- is powerful constriciton of afferent arterioles ,which decreases the GFR and slow production of filtrate
- Triggered by crisis such as acute reduction in BP or a AMI
- Sympathetic activation can overide the local regulatory mechanism that act to stabilize GFR
- as crisis passes, GFR will return to normal
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Major hormones involved in kidney function control
- Angiotension II
- ADH
- aldosterone
- ANP
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Hormones regulated by the renin-angiotension system are
- angiotension II
- Aldosterone
- ADH
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Renin-angiotension system- renin
- If GFR remains low the juxtaglomerular apparatus releases the enzyme reninin into circuation
- Renin converts angiotensiogen to angiotension I
- ACE concerts Angiotension I to II
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Effects of angiotensions II
- Brief powerful constriction in peripheral capillary beds, that elevates Bp in renal arteries
- triggers constriction of efferent arterioles awhich elevates glomular pressure and filtration rates
- Trigers release of ADH in the CNS which stimulates reabsorption of water and soium ions and induces senation of thirst
- at the adrenal gland, stimulates secretion of aldosterone by the adrenal cortex and E and NE by the adrenal medullae, sudden dramatic increase in BP
- at the kidneys aldoserone stimulates sodium reaborption along the DCT and collecting system
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ADH
- inceases the water permeability of the DCT and collecting duct which stimulates the reabsorption of water from the tubular fluid
- induces sensation of thirst
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ADH release occurs
- under angiotension II stimulation
- and independently when hypothamic neurons are stimulated by a reducation in bp or incease in solulte concentration of circulating blood
- specialized hypothalmic neurons are called osmoreceptors
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Aldosterone
- stimulates reabsorption of sodium ions and secretion of potassium ions along the DCT and collecting duct
- occurs primarily under angiotension II stimulation and inresponse to a rise in potassium ion concentration of the blood
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ANP artial natriuretic peptide
- opposes those of the renin angiontension system
- released by atrical cardiac muscle cells when blood volume and bp are too high
- ANP affects the kidney by a decreasein the rate of sodium ion reabsorption in the DCT,leads to increased sodium loss in the urine
- dilation of the glomerular capillaries which resulse in increased flomerular filtration and urinary water loss
- inactivation of the renin angiotension sysmtem through the inhibition of renin,aldosterone, and ADH secretion
- net loss of sodimm ions
- lowers bp and blood volume
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Objective:
Describe the structures and function of the ureters ,urinary bladder,and urethra(pp.675-680)
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Structures of the urinary tract are responsible for the
transport,storage,and elimination of urine
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Ureters
pair of muscular tubes that conduct urine from the kidneys
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Ureteral openings within the urinary bladder are slit like ,which
is a shape that prevents backflow of urine when the bladder contracts
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Wall of bladder contains
transitional epithelium , middle later of longitudal and circular bands of smooth muscle and outer connective tissue layer continues with renal capsule
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Every 30 sec a _______ contraction begins at the renal pelvis and sweeps across the ureter and forces urine towards the bladder
peristaltic
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Cannuli
kidney stones,presence is known as nephrolithiasis
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Urinary bladder
hollow muscular organ that sotres urine prior to urination. demensions depends on destention
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trigone
triangular area that the urinary bladder is bounded by the ureteral openings and enternce to the uretha
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Neck of the urinary bladder
contains the internal uretharl sphincter, surrounds the urethral entrance
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internal urethral sphinter
provides involuntary control over dischage of urine from the bladder
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