Chapter 26_AP2 Flashcards
Urinary System
Urine is carried from the kidneys to the urinary bladder by the
ureter.
Arrange the following structures in correct sequence:
1) ureter
2) renal pelvis
3) calyx
4) urinary bladder
5) urethra
3, 2, 1, 4, 5
Blood vessels, nerves, and the ureter enter and leave the kidney at the
hilum.
The structural and functional units of the kidney are called
nephrons.
The juxtamedullary nephrons have?
Long loops of Henle
The visceral layer of Bowman’s capsule is:
part of the filtration membrane and contains podocytes
An obstruction in the afferent arteriole would reduce the flow of blood into the
glomerulus
The filtration membrane consists of the
podocytes, capillary endothelium, and basement membrane
Urine passes from the distal convoluted tubule (DCT) to the _____ and then to the minor calyx.
collecting duct.
One feature of renal blood circulation that makes it unique is that
each nephron has at least two capillary networks
Trace the path of a red blood cell from the renal artery to the glomerulus:
1) interlobar artery
2) interlobular artery
3) arcuate artery
4) afferent arteriole
1, 3, 2, 4
The urinary bladder
stores urine until it is voided
Skeletal muscle that surrounds the urethra as it extends through the pelvic floor forms the
external urinary sphincter
Formation of filtrate depends on a
pressure gradient
The active transport of substances from the capillaries into the kidney tubules is called tubular ______.
secretion
The part of the cardiac output that passes through the kidneys is the
renal fraction
Passage of proteins into Bowman’s capsule is prevented by
the size of the capillary pores, the size of the filtration slits in the podocytes, and the size of the proteins
Decreased blood colloid osmotic pressure affects renal function by
increasing net filtration pressure
The collecting duct becomes more permeable to water when
ADH production increases
Hydrogen ions are secreted into the filtrate by both the
proximal and distal tubules
The ability of the kidney to concentrate urine depends on
a high medullary concentration gradient
A countercurrent mechanism is in
both the loop of Henle and the vasa recta
The juxtaglomerular apparatus secretes
renin
The kidneys produce renin when
the blood pressure in the afferent arteriole decreases
Atrial natriuretic hormone
is secreted when blood pressure increases
Autoregulation in the kidney involves changes in the degree of
constriction of afferent arterioles
When the tubular maximum for a substance is exceeded
the excess remains in the filtrate
When aldosterone is absent, sodium reabsorption in the nephron is
greatly decreased
Atrial natriuretic hormone increases
urine volume
List 6 functions of the urinary system
- eliminates wastes
- regulates blood volume
- regulates ion concentration
- regulates pH
- red blood cell production
- vitamin D production
The urinary system consists of:
kidneys, ureters, urinary bladder, and urethra
Location of the Kidneys:
lies behind the peritoneum on the posterior abdominal wall on each side of the vertebral column
Renal capsule:
fibrous connective
tissue. Surrounds each kidney
Perirenal fat:
Engulfs renal capsule and acts as
cushioning
Renal fascia:
thin layer of loose connective tissue that anchors kidneys and surrounding
adipose to abdominal wall
Hilum
Renal artery and nerves enter and
renal vein and ureter exit kidneys; opens into renal sinus
renal sinus
cavity
filled with fat and loose connective
tissue
Cortex:
Outer area of kidney
Medulla:
Inner area of kidney; surrounds renal sinus
Renal columns
part of
cortical tissue that extends into
medulla
Renal pyramids
cone-shaped. Base is boundary between cortex and medulla. Apex of pyramid is renal papilla, points toward sinus.
Pelvis:
enlarged chamber
formed by major calyces
Ureter:
exits at the hilum;
connects to urinary bladder
Parts of the nephron:
Bowman’s capsule, proximal
tubule, loop of Henle
(nephronic loop), distal
tubule
Urine continues from the
nephron to
collecting ducts,
papillary ducts, minor
calyses, major calyses, and the
renal pelvis
Renal corpuscle.
Bowman’s
capsule plus a capillary bed
called the glomerulus.
Glomerulus:
network of capillaries. Blood enters through afferent arteriole, exits through efferent arteriole.
Parietal layer:
outer. Simple squamous epithelium that becomes cube-shaped where Bowman’s capsule ends and proximal tubule begins
Visceral layer:
inner.
Specialized podocytes that
wrap around the
glomerular capillaries
Fenestrae:
window-like openings in
the endothelial cells of the
glomerular capillaries.
Filtrations slits:
gaps between the cell processes of the podocytes. Basement membrane sandwiched between the endothelial cells of the glomerular capillaries and the podocytes.
Filtration membrane:
capillary endothelium, basement membrane and podocytes. First stage of urine formation occurs here when fluid from blood in capillaries moves across filtration membrane into the lumen inside Bowman’s capsule.
Afferent arteriole
supplies blood to glomerulus
Efferent arteriole
drains glomerulus
Afferent and Efferent arterioles have a layer of
smooth muscle
Macula densa
Specialized tubule cells of the distal tubule. The
distal tubule lies between the afferent and efferent arterioles.
Proximal tubule:
simple cuboidal
epithelium with many microvilli
Loops of Henle
Ascending limb and descending limb
Ascending limb
first part
simple squamous epithelium
and thin, distal part thicker and
simple cuboidal
Descending limb
first part
similar to proximal tubule.
Latter part simple squamous
epithelium and thinner
Distal tubule
shorter than
proximal tubule. Simple cuboidal,
but smaller cells and very few
microvilli
Collecting ducts:
form where many distal tubules come together. Larger in diameter, simple cuboidal epithelium. Form medullary rays and lead to papillary ducts
Arterial supply:
- Renal arteries branch from abdominal aorta
- Segmental arteries branch from renal
- Interlobar arteries ascend within renal
columns toward cortex - Arcuate arteries branch and arch over
the base of the pyramids - Interlobular arteries project into cortex and
give rise to afferent arterioles
The part of the circulation involved with urine formation
- Afferent arterioles supply blood to glomerulus
- Glomerulus
- Efferent arterioles exit the renal corpuscle
- Peritubular capillaries form a plexus around the proximal and distal tubules
- Vasa recta: specialized parts of peritubular capillaries that course into medulla along with loops of Henle, then back toward cortex
Venous drainage
11. Peritubular capillaries drain into interlobular veins and lead to 12. Arcuate veins 13. Interlobar veins 14. Renal veins
Filtrate
water, small molecules, ions that can pass through membrane; pressure forces it across filtration membrane
Renal blood flow rate
1176 mL/min
Renal plasma flow rate:
renal blood flow rate X fraction of
blood that is plasma: 650 mL/min
Filtration fraction:
part of plasma that is filtered into lumen of
Bowman’s capsules; average 19%
Glomerular filtration rate (GFR):
amount of filtrate produced
each minute. 180 L/day
Average urine production/day:
1-2 L. Most of filtrate must be
reabsorbed
Filtration membrane
filtration barrier. It prevents
blood cells and proteins from entering lumen of
Bowman’s capsule, but is many times more permeable
than a typical capillary
Filtration pressure:
pressure gradient responsible for
filtration; forces fluid from glomerular capillary across
membrane into lumen of Bowman’s capsules
Forces that affect movement of fluid into or out of the lumen of
Bowman’s capsule
Glomerular capillary pressure (GCP): blood pressure inside capillary tends to move fluid out of capillary into Bowman’s capsule
– Capsule hydrostatic pressure (CHP): pressure of filtrate already in the lumen
– Blood colloid osmotic pressure (BCOP): osmotic pressure caused by proteins in blood. Favors fluid movement into the capillary from the lumen. BCOP greater at end of glomerular capillary than at beginning because of fluid leaving capillary and entering lumen
High glomerular capillary pressure results from
Low resistance to blood flow in afferent arterioles
– Low resistance to blood flow in glomerular capillaries
– High resistance to blood flow in efferent arterioles: small diameter vessels
Changes in afferent and efferent arteriole diameter alter filtration
pressure
Dilation of afferent arterioles/constriction efferent arterioles increases
glomerular capillary pressure, increasing filtration pressure and thus
glomerular filtration
Autoregulation of GFR
Involves changes in degree of constriction in afferent arterioles
Sympathetic stimulation of GFR: norepinephrine
– Constricts small arteries and afferent arterioles
– Decreases renal blood flow and thus filtrate formation
– During shock or intense exercise: intense sympathetic stimulation, rate of filtrate formation drops to a few mm
Tubular reabsorption
occurs as filtrate flows through
the lumens of proximal tubule, loop of Henle, distal
tubule, and collecting ducts
Tubular reabsorption results because of:
– Diffusion – Facilitated diffusion – Active transport – Symport – Osmosis
Diffusion between cells:
from lumen of nephron into interstitial fluid – Depends on rate of transport of same solutes through the cells of the tubule – K+, Ca2+, and Mg2+
Descending thin segment of loop of Henle is:
highly permeable to water and
moderately permeable to urea,
sodium, most other ions
(passive).
Ascending thin segment of loop of Henle is:
not permeable to water, but is permeable to solutes. Solutes diffuse out of the tubule and into the more dilute interstitial fluid as the ascending limb projects toward the cortex. Solutes diffuse into the descending vasa recta.
Tubular Secretion
Moves metabolic by-products, drugs, molecules
not normally produced by the body into tubule of
nephron
Atrial natriuretic hormone
– Produced by right atrium of heart when blood volume increases stretching cells
– Inhibits Na+ reabsorption
– Inhibits ADH production
– Increases volume of urine produced
– Venous return is lowered, volume in right
atrium decreases
Tubular load
Total amount of substance that passes through filtration
membrane into nephrons each minute
Tubular maximum
Maximum rate at which a
substance can be actively
absorbed
Urine Movement
Hydrostatic pressure forces urine through
nephron
Ureters:
bring urine from
renal pelvis to urinary
bladder. Lined by transitional
epithelium
Urinary bladder:
hollow muscular container. In pelvic cavity posterior to symphysis pubis. Lined with transitional epithelium;
Trigone:
interior of urinary bladder. Triangular area between the
entry of the two ureters and the exit of the urethra. Area expands
less than rest of bladder during filling
