Chapter 26: The Urinary System Flashcards
1
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Urinary System
A
Consists of 2 kidneys, 2 ureters, 1 urinary bladder and one urethra.
2
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Nephrology
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Study of anatomy, physiology and pathology of the kidneys.
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Q
Functions of Kidneys
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- Regulate blood volume, compositions, blood pressure, pH and glucose levels
- Produce 2 hormones: calcitriol and erythropoietin
- Ureters transport urine from kidneys to bladder.
- Bladder stores urine and expels it into urethra.
- Urethra discharge urine from body.
- Excretes wastes in urine.
4
Q
Kidneys
A
Reddish, kidney beans shaped organs located just above the waist between the peritoneum and the posterior wall of the abdomen.
Secretes: urea
Due to there position said to be retroperitoneal.
Has 3 layers of tissue: deep to superficial- renal capsule, adipose capsule, renal fascia.
5
Q
Renal Capsule
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Deep layer of kidney tissue
Smooth, transparent sheet of dense irregular CT that is continuous with the outer coat of the ureter.
Serves as barrier against trauma and helps maintain shape.
6
Q
Adipose Capsule
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Middle layer of kidney tissue.
Mass of fatty tissue surrounds the renal capsule.
Also protects the kidney from trauma.
Holds it firmly in place within the abdominal cavity.
7
Q
Renal Fascia
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Superficial layer of kidney tissue.
Thin layer of dense irregular CT that anchors the kidney to surrounding structures and to abd wall.
8
Q
Renal Hilum
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Found near the center of the concave border.
An indentation through which the urethra emerges from the kidneys along with blood vessels, lymphatic vessels and nerves.
9
Q
Renal Cortex
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One of two distinct regions of the kidney.
Superficial, light red region.
Is smooth texture red areas extending from the renal capsule to the bases of the renal pyramids.
Contains renal columns that are divided into outer and inner layer.
outer: cortical zone
inner: juxtamedullary zone
10
Q
Renal Medulla
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One of two district regions of the kidney.
Deep, darker reddish inner region.
Consists of several cone shaped renal pyramids.
Build up of urea can happen here due to urea recycling
11
Q
Renal Pyramids
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Found in renal medulla regions of kidney.
The base of each pyramid faces renal cortex.
Renal papilla is the apex of the pyramids.
12
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Renal Columns
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Portions of the renal cortex: cortical zone and juxtamedullary zone.
They extend between the renal pyramids.
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Q
Parenchyma
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The renal cortex and renal pyramids of the renal medulla form this functional part of the kidney.
Contained within are function structures called nephrons that form filtered fluid called filtrate.
14
Q
Nephrons
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Found within the parenchyma.
These are functional units of the kidney.
Form filtrate.
About 1 million microscopic structures that filter fluid.
15
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Papillary Ducts
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Filtered fluid that is formed by the nephrons drains into these ducts.
They extend through the renal papillae of the pyramids.
16
Q
Minor and Major Calyces
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Cup like structures where papillary ducts drain into
Each kidney has 8-18 minor calyces or 2 to 3 major calyces.
A minor calyx recieves filtrate from papillary ducts of one renal papilla and delivers it to a major calyx.
Once the flitrate enters the calyces it becomes urine and no further reabsorption can occur.
17
Q
Renal Pelvis
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Single large cavity where urine drains from the major calyces.
From here the urine moves through the ureter to the urinary bladder.
18
Q
Renal Sinus
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Cavity within the kidney where the hilum expands into.
Contains part of the renal pelvis, the calyces and branches of the renal blood vessels and nerves.
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Q
Renal Arteries
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These arteries recieve 20-25% of the resting cardiac output.
20
Q
Renal Blood Flow
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About 1200ml per min in adults. The blood flows through both kidneys.
Flow: interlobular arteries, arcuate arteries, glomerular capillaries, arcuate veins
21
Q
Afferent Arterioles
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Arteries radiate outer ward and enter the renal cortex where they branches off to form there arterioles.
Each nephron recieves one afferent arteriole.
22
Q
Glomerulus
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Filters blood.
Tangled ball shaped capillary network that is formed when the one afferent arteriole is received by the nephron.
These capillaries are unique because they are positioned between two arterioles rather than between an arteriole and a venule.
23
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Efferent Arterioles
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Formed when the glomerular capillaries reunite and carries blood out of the glomerulus.
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Peritubular Capillaries
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Form when the efferent arterioles divide.
They surround tubular parts of the nephron in the renal cortex.
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Vasa Recta
Extend from efferent arterioles.
Long, loop shaped capillaries that supply tubular portions of the nephron in the renal medulla.
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Renal Vein
Single veins where blood leaves the kidney.
Exits at the renal Hilum and carries venous blood to the inferior vena cava.
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Renal Nerves
Orientate in the renal ganglion and pass through renal plexus into the kidneys along with the renal arteries.
Therese nerves are a part of the sympathetic division of the ANS.
Most nerves are Vasomotor nerves that regulate the flow of blood through the kidneys by causing vasodilation or vasoconstriction of renal arterioles.
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Renal Corpuscle
One part of the nephron where blood plasma is filtered.
Two components: glomerulus (capillary network) and the glomerular capsule or Bowmans capsule (double walled epithelial cup that surrounds the glomerular capillaries).
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Glomerular Caspule
Filters blood plasma.
Consists of:
1. visceral layer- modified simple squamous epi cells called podocytes. Foot-like projections that wrap around the single endothelial cells of the glomerular capillaries and form the inner wall of the capsule.
2. parietal layer - simple squamous epi, forms the outer wall of the capsule
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Renal Tubule
One of two parts of the Nephrons.
When sunstance are excreted from these tubes that substance leaves the bloodstream.
Consist of 3 parts:
1. Proximal convoluted tubule (PCT) - part that is attached to the glomerular capsule. Reabsorbs mort of the sunstance.
2. Nephron loop or loop of henle
3. Distal convoluted tubule (DCT) - consists of principal cells. Contains peritubular capillaries for tubular secretion.
Part that is further away
Convoluted means: the tubule is tightly coiled rather than straight.
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Collecting Duct (CD)
Single duct where the distal convoluted tubules empties.
These collecting ducts then unite and converge into Sertraline hundred large papillary ducts which drain into minor calyces.
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Descending Limb of the Nephron
First part of the nephron loop.
Begins at the point where the proximal convoluted tubule takes its final turn downward.
Begins in the renal cortex and extends downward into the renal medulla.
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Ascending Limb of the Nephron Loop
Where the nephron loop makes a hairpin turn and returns to the renal cortex where it terminated at the distal convoluted tubule.
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Cortical Nephrons
About 80-85% of nephrons are cortical nephrons.
Their renal corpuscles lies in the outer portion of the renal cortex and they have a short nephron loop that lie mainly in the cortex and penetrate only into the outer region of the renal medulla.
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Juxtamedullary Nephrons
The other 15-20% of nephrons.
Their renal corpuscles lie deep in the cortex close to the medulla and they have a long nephron loop that extends into the deepest region of the medulla.
Ascending limb of this nephron consists of 2 portions:
1. Thin ascending limb
2. Thick ascending limb.
The long loops enable the kidneys to excrete very dilute or very concentrated urine.
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Capsular Space
Space between the two layers of the glomerular capsule.
Continuous with the lumen of the renal tubule.
Fluid from the glomerular capillaries enters this space.
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Principal Cells
Found in the last part of the DCT and collecting ducts.
Have receptors for both antidiuretic hormone (ADH) and aldosterone. These 2 hormones regulate their functions.
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Intercalated Cells
Found at the last part of DCT and collecting ducts.
Plays a role in the homeostasis of blood pH by secreting H+ and reabsorbing HCO3.
Also reabsorbs potassium.
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Juxtaglomerular Cells (JG)
Found alongside the macula dense.
Modified smooth muscle fibers found in the wall of the afferent arteriole (sometimes in efferent).
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Juxtaglomerular Apparatus (JGA)
Formed by the macula densa and JG cells.
Helps regulate blood pressure within the kidneys via a negative feed back.
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Urine Production performed by the Nephrons and Collecting Ducts
Normal voulme: 2L/Day
1. Glomerular filtration: blood plasma and dissolved substances get filtered into the glomerular capsule
2. Tubular reabsorption: along the renal tubule and collecting ducts, water ions and other substances get reabsorbed from the renal tubule lumen into the peritubular capillaries and then into blood
3. Tubular secretion: along the renal tubule and collecting ducts, substances such as waste, drugs and excess ions get secreted from, the peritubular capillaries into the renal tubules. Remove substance from blood. These substances make the way into urine.
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Glomerular Filtrate Flow
Fluid that enters the capsular space.
Daily volume is 150 L in adult females and 180 L in adult males.
Flow: glomerular capsule, proximal convoluted tubule (PCT), loop of henle, distal convoluted tubule (DCT), collecting duct.
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Filtration Fraction
The fraction of blood plasma in the afferent arterioles of the kidneys that becomes glomerular filtrate.
0.16-0.20
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Filtration Membrane
Formed by the glomerular capillaries and the podocytes. They form this leaky barrier.
Permits filtration of water and small solutes but prevents filtration of most plasma proteins and blood cells.
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3 Filtration Membrane Barriers
Substances filtered from blood cross 3 filtration barriers
1. Fenestrations (pore) of glomerular endothelial cell: prevents filtration of blood cells but allows components of blood plasma to pass through
2. Basement membrane of glomerulus: prevents filtration of larger proteins
3. Slit membrane between pedicles: prevents filtration of medium sized proteins.
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Mesangial Cells
These cells are located among the glomerular capillaries and in the cleft between afferent and efferent arterioles.
These contractile cells help regulate glomerular filtration.
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Glomerular Filtration Depends on 3 Main Pressures
1. Glomerular blood hydrostatic pressures (GBHP): blood pressure in glomerular capillaries. About 55 mmHg. Promotes filtration by forcing water and solutes in blood plasma through the filtration membrane.
2. Capsular hydrostatic pressure (CHP): pressure excreted against the filtration membrane by fluid already in the capsular space and renal tubule. Opposes filtration, represents a back pressure. About 15 mmHg.
3. Blood colloid osmotic pressure (BCOP): due to the pressure of proteins such as albumin, globulins and fibrinogen in blood plasma, opposes filtration. About 30 mmHg.
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Glomerular Filtration Rate (GFR)
Is the amount of filtrate formed in all renal corpuscles of both kidneys each min.
Average is 125 mL/min in males, 105 mL/min in females.
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Renal Autoregulation of GFR
The capability where the kidneys themselves help maintain a constance renal blood flow and GFR despite normal everyday changes in blood pressure.
Consists of 2 mechanism:
1. Myogenic mechanism: occurs when stretching triggers contraction of smooth muscle cells in the walls of afferent arterioles.
2. Tubuloglomerular feedback: part of renal tubules, the macula densa provided feedback to the glomerulus.
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Neural Regulation of GFR
Kidneys are supplied by sympathetic ANS fibers that release norepinephrine. This causes vasoconstriction lower renal blood flow that has 2 consequences;
1. It reduced urine output which helps conserve blood volume
2. It permits greater blood flow to other body tissues.
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Angiotensin II on Kidneys
Hormone regulation of GFR.
Low blood volume or low blood pressure stimulates renin to produce this hormone
Affects are:
1. Decreases GFR
2. reabsorb of certain ions
3. Stimulates release of aldosterone
4. A potential vasoconstrictor that narrows both afferent and efferent arterioles and reduces renal blood flow thereby decreasing GFR.
.
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Atrial Natriuretic Peptide (ANP)
Hormonal regulation of GFR
Secreted by cells in the atria of the heart.
Stretching of the atria as occurs when blood volume increases it stimulates secretion of ANP. This causes relaxation of the glomerular mesangial cells.
ANP increases the capillary surface area available for filtration.
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Renin-Angiotensin-Aldosterone System
When blood volume and blood pressure decrease the walls of the afferent arterioles are stretched less and the juxtaglomerular cells secrete the enzymes renin into the blood.
Renin clips off 10 amino acid peptide called Angiotensin I from angiotensinogen which is synthesized by hepatocytes.
By clipping off 2 or more among acids angiotensin converting enzyme (ACE) converts angiotensin I to angiotensin II.
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Angiotensin II affects on Renal Physiology
Angiotensin II is the active from of the hormone.
1. Decreases the glomerular filtration rate by causing vasoconstriction of the afferent arterioles.
2. Enhances reabsorption of Na and H2O in the proximal convoluted tubule by stimulating the activity of NA -H antiporters.
3. Stimulates the adrenal cortex to release aldosterone. A hormones that in turn stimulus the principal cells in the collections ducts to reabsorbed more Na and secrete more K.
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Antidiuretic Hormone (ADH)
Or vasopressin.
Is released by the posterior pituitary when osmolarity of extracellular fluid is increased or a decrease in blood volume.
Regulates filtered water reabsorption by increasing the water permeability of principal cells in the last part of the distal convoluted tubule and throughout the collecting duct.
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Aquaporin-2
Water channel protein found within tiny vesicles of principal cells.
ADH stimulus insertion of the aquaproin-2 contains vesicles into the apical membranes via exocytosis.
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The Degree of Facultative Water Reabsorption caused by ADH
Depends of 3 things:
1. Normal hydration: under normal conditions enough ADH is present in the blood to cause reabsorption of 19% of filtered water in the late distal tubule and collecting ducts.
2. Dehydration: when the body is dehydrated the concentration of ADH increases in blood. Thus causes an increase in the amount of filtered waters that is reabsorbed in the late distal tubule and collecting ducts.
3. Over-hydration: when the body is over hydrated the concentration of ADH in blood will decrease. This in turn decreased the amount of filtered water that is reabsorbed in the late distal tubule and collecting ducts.
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Urine (Water Volume)
Water accounts for about 95% of total volume of urine
Normal total volume is 1-2 L in 24hrs.
Color is a yellow or amber.
Transparent when freshly voided.
Mildly aromatic.
PH: 4.6-8.0
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Blood Test for Kindeys: BUN and Creatinine.
Blood Urea Nitrogen (BUN): measures the blood nitrogen that is part of the urea resulting from catabolism and domination of amino acids. Can be treated by decreasing protein intake.
A high amount can be caused by renal obstruction.
Creatinine: measures kidney function, results from the catabolism of creatine phosphate in skeletal muscle. Normal blood creatine levels remains steady. A leave of about 1.5 mg/dl is poor renal function.
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Renal Plasma Clearance
Is the volume of blood that is cleaned or cleared of a substance per unit of time.
Expressed in units of milliliters power min.
High level: indicated efficient excretion of a substance in the urine
Low level: indicated inefficient excretion.
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Renal Plasma Flow
The amount of plasma that passes through the kidneys in 1 min.
Typical: 650 mL per min
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Ureters
Transport urine from the renal pelvis to the urinary bladder.
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3 Tissue Layers of the Ureters
Deep to Superficial
1. Mucosa: epithelium layer, mucous membrane with transitional epi.
Contains: lamina propria - underlying layer of areolar CT with collagen, elastic fibers and lymphatic tissue.
2. Muscularis: intermediate coat. Throughout most of the length of ureters. Composed of inner longitudinal and outer circular layers of smooth muscle fibers.
3. Adventitia: areolar CT contain blood vessels, lymphatic vessels and nerves that serve the muscularis and mucosa.
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Urinary Bladder
Is a hallow, distensible muscular organ situated in the pelvic cavity posterior to the pubic symphysis.
Males: directly anterior to the rectum.
Females: anterior to the vagina and inferior to the uterus.
Folds of the peritoneum hold the urinary bladder in place.
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Trigone
Small triangular area on the floor of the urinary bladder.
Has a smooth appearance.
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Internal Urethral Orifce
Found on the 2 posterior corners of the trigone.
2 ureteral openings into the urethra.
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3 Coats that Make Up the Wall of the Urinary Bladder
1. Mucosa: deepest coat. Is surrounded by intermediate Muscularis known detrusor muscle,
Consists of 3 layers of smooth muscle fibers: inner longitudinal, middle circular and outer longitudinal layers.
2. Transitional Epi: mucous membrane. Permits stretching
Rugae is also present to permit expansion.
3. Lamina propria: underlying layer.
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Internal Urethral Sphincter
Formed by circular fibers.
Found around the opening to the urethra
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External Urethral Sphincter
Is inferior to internal urethral sphincter.
Composed of skeletal muscle
A modification of the deep muscle of the perineum.
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Serosa of the Urinary Bladder
Fund over the superior surface of urinary bladder.
A layer of visceral peritoneum.
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Micturition
Discharge of urine from the urinary bladder.
Occurs via a combination of involuntary and voluntary muscle contractions.
When volume exceed 200-400 mL, pressures within the bladder increase and the stretch respects in the walls will transmit nerve impulses into the spinal cord.
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Micturition Center
Impulses that are propagated when stretch receptors from the bladder reach the sacral spinal cord segments S2 and S3.
Triggers spinal reflex knows as Micturition reflex.
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Urethra
Small tube leading from the internal urethra orifice in the floor if the urinary bladder to the exterior of the body.
In both males and females, the urethra is terminal portion of the urinary system.
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3 Anatomical Regions of Male Urethra
Consists of stratified columnar and pseudo stratified columnar epi.
1. Prostatic urethra: passed through the prostate
2. Intermediate membranous urethra: shortest portion, passes through the deep muscles of the perineum
3. Spongy urethra: the longest portion, passes through the penis.
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Prostatic Urethra
Contains 3 openings
1: ducts that transport secretions from the prostate
2 and 3: Seminal vesicles and Ductus Vas deferens: deliver sperm into the urethra and provide secretions that both neutralize the acidity of the female reproductive tract and contribute to sperm motility and viability.
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Bulbourethral Glands
Ducts that empty into the spongy urethra.
These ducts deliver alkaline substance proportional to ejaculation that neutralizes the acidity of the urethra.
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Urethral Glands
Ducts that discharge mucus during sexual arousal.
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Proximal Convoluted Tubule (PCT)
Part of nephrons that reabsorbs the most substances
Reabsorbs 65 % of filtratered water
Is lined with cells that have a border of microvilli. This increase the surface area for reabsorption and secretion.
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Basal Lamina
Layer of filtration membrane that is composed of collagen fibers and proteoglycans in a glycoproteins matrix.
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Podocytes
modified simple squamous epi cells found in the visceral layer of the globular capsule that
Filters blood plasma.
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Tubular Secretion
Cells secrete wastes, drugs, excess ions and other material into the filtrate of the renal tubule and collecting ducts.
The substances eventually exit the kidney via the ureters.
Can occur from the pertitubular capillaries located int he DCT.
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Uric Acid
The breakdown product Nucleic acids that is eliminated by the kidneys.
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Macula Densa
Columnar tubular cells found in the wall of the nephron loop.
Together with the juxtaglomerular cells is the juxtaglomerular apparatus.
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Waste Management of Other Body System
The lungs, buffer systems,blood, liver, GI tract and sweat glands all play a role in the transport process excretion of waste products.
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Erythropoietin
Renal hormone that stimulates production of RBC.
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Calcitriol
Renal hormone that is an active form of vitamin D. Helps regulate calcium hemostasis.
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Kidneys and Liver
Can synthesize amino acids, glutamine and new glucose molecules.
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Calcium
Most important ion regulated by the kidney.
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Peristaltic Contractions
Peristaltic waves along the urethra move urine towards the bladder.
Hydrostatic pressure and gravity also contribute to the flow of urine.
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Epithelium of the Prostaic Urthra
Epi is continuous with that of the urinary bladder
Consist of transitional epi that becomes stratified columnar and pseudo stratified columnar epi.
