Lecture Exam 2 - Urinary System Study Guide Flashcards
Urinary system consists of:
2 kidneys
2 ureters
1 bladder
I urethra
Define: Nephrology
scientific study of the anatomy, physiology and pathology of kidneys.
Define: Urology
study of anatomy, physiology and pathology of male and female urinary systems and male reproductive system.
Know the basic seven functions of the urinary system as laid out in lecture.
1) Regulation of blood ionic composition - particularly Na+,
K+, Ca(^2+), Cl-, HPO4(^2-).
2) Regulation of blood pH - excrete H+ and conserve HCO3- in order to regulate pH.
3) Regulation of blood volume - adjust blood volume by conserving or eliminating water as necessary. Increased blood volume increases blood pressure and vice versa.
4) Regulation of blood pressure - help regulate blood pressure by secreting renin (part of reninangiotensin-aldosterone system).
5) Maintenance of blood osmolarity - by regulating loss of water and loss of solutes - maintain relatively constant blood osmolarity of 300 milliosmoles/litre (mOsm/l).
5) Production of hormones. Kidneys produce 2 hormones:
i. Calcitriol - active form of Vit D that helps regulate blood calcium homeostasis.
ii. Erythropoetin - stimulates
production of red blood cells.
6) Regulation of blood glucose level - can use the amino acid, glutamine for gluconeogenesis
(also occurs in liver). Glucose produced is released into blood.
7) Excretion of wastes and foreign substances - formation of urine to secrete wastes.
e. g. a) ammonia and urea from deamination of amino acids
b) bilirubin from catabolism of hemoglobin
c) creatine from breakdown of creatine phosphate in muscle.
d) uric acid from catabolism of nucleic acids. drugs and environmental toxins.
Where are the kidneys located with respect to the spinal column?
Located between T10 and L3.
Partially protected by 11th and 12th ribs.
Where are the kidneys located with respect to the ribs?
Partially protected by 11th and 12th ribs.
Which kidney is higher than the other and why?
Right kidney slightly lower than left kidney because of size of right liver lobe.
Approximately how long and how wide is a human kidney?
4-5 inches long 2-3 inches wide
What are the 3 coverings of the kidney?
What type of tissue makes up each of these coverings?
3 layers surround each kidney (from deep to superficial)
1) Renal capsule - dense irregular CT
2) Adipose capsule - protective
3) Renal fascia - another thin layer of dense irregular CT - anchors kidney to peritoneum
What is the pathway followed by urine when it exits the kidney?
A nephron is a functional unit of the kidney - about 1 million nephrons present in each kidney.
Urine from the nephrons drains into papillary ducts that drain into cup-like structures (calyces) and then into the renal pelvis.
Renal pelvis drains into renal sinus and into ureter.
Through what vessel does blood enter the kidney?
renal artery
What is the pathway of blood to the glomerulus?
1) Renal Artery: Brings blood supply to the kidney; divides into the smaller; Divides into small branches that end as afferent arterioles
2) Afferent Arterioles: Branch out into glomerular capillaries
3) Glomerular Capillaries: Send blood to efferent arterioles
4) Efferent Arterioles: Send blood supply into the peritubular capillaries
5) Peritubular Capillaries: Eventually drains into renal vein
* **Major Diff. betwn systemic & renal blood circulation is the presence of 2 capillary beds instead of one
Through what vessel does blood enter the glomerulus?
The afferent arteriole carries blood from the renal artery into the glomerulus. The afferent arteriole is a cluster of blood vessels supplying nephrons to a number of excretory systems whereas the glomerulus is a mass of nerve fibres. The efferent arteriole carries blood away.
Through what vessel does blood leave the glomerulus?
Blood is filtered from the glomerulus into the glomerular capsule and then passes into renal tubules.
Renal tubules made up of 3 parts:
1) Proximal convoluted tubule
2) Loop of Henle (sometimes called nephron loop)
3) Distal convoluted tubule
Where are the peritubular capillaries located?
In the renal system, peritubular capillaries are tiny blood vessels that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron.
Ions and minerals that need to be saved in the body are reabsorbed into the peritubular capillaries through active transport, secondary active transport, or transcytosis.
What percentage of total resting cardiac output is received by the kidneys?
Receive 20-25% of resting cardiac output.
Approximately how many nephrons are present in each kidney?
one million
Know the difference in structure between a cortical nephron and a juxtamedullary nephron.
Cortical nephrons - 80-85% of total nephrons:
- Renal corpuscles lie in outer portion of renal cortex.
- Short loops of Henle - mostly in cortex
- Receive blood from peritubular capillaries
Juxtamedullary nephrons -15 20% of total nephrons
- Renal corpuscles deep in cortex, close to medulla.
- Long loop of Henle - extending into medulla - has thick and thin portions.
- Receive blood from peritubular capillaries and from vasa recta.
What do the terms proximal, distal and convoluted mean with respect to renal tubules?
Proximal = part of tube attached to glomerular capsule.
Distal = part of tube further away from glomerular capsule.
Convoluted = part of tube that is tightly coiled rather than straight.
What are the 3 parts of a renal tubule?
Renal tubule - where filtered fluid passes from renal corpuscle.
Renal tubules made up of 3 parts:
1) Proximal convoluted tubule
2) Loop of Henle (sometimes called nephron loop)
3) Distal convoluted tubule
What are the 2 major components of a renal corpuscle?
Renal Corpuscle - where blood is filtered.
Two components of renal corpuscle:
1) Glomerular capsule (Bowman’s capsule) - double-walled epithelial cup
2) Glomerulus - capillary network contained in the “cup”.
Know the detailed structure of a renal corpuscle including the names and locations of the different layers and the names locations and functions of the different cell-types.
Two components of renal corpuscle:
1) Glomerular capsule (Bowman’s capsule) - double-walled epithelial cup
2) Glomerulus - capillary network contained in the
“cup”.
Blood is filtered from the glomerulus into the glomerular capsule and then passes into renal tubules.
Bowman’s capsule - visceral and parietal layers.
Visceral layer - modified squamous epithelia cells
(podocytes - meaning foot cells).
Foot-like projections of podocytes wrap around
endothelium of glomerular capillaries forming the inner wall of the capsule.
Parietal layer - composed of simple squamous epithelium.
What is the pathway of fluid flow from the blood entering a renal corpuscle to the renal tubules?
Blood is carried out of the glomerulus by an efferent arteriole instead of a venule, as is observed in most other capillary systems. This provides tighter control over the blood flow through the glomerulus, since arterioles dilate and constrict more readily than venules, owing to arterioles’ larger smooth muscle layer (tunica media).
Efferent arterioles of juxtamedullary nephrons (i.e., the 15% of nephrons closest to the medulla) send straight capillary branches that deliver isotonic blood to the renal medulla. Along with the loop of Henle, these vasa recta play a crucial role in the establishment of the nephron’s countercurrent exchange system.
The efferent arteriole, into which the glomerulus delivers blood, empties into an interlobular vein.
How does the structure of the epithelial wall change along the renal tubules?
In descending loop of Henle - simple squamous epithelia for easy exchange of substances
In thick ascending loop of Henle (in juxtamedullary nephrons) epithelia gradually becomes cuboidal and then columnar.
Epithelial cells in thick ascending limb make contact with afferent arterioles of renal corpuscle - become crowded - often called macula densa.
Macula densa in contact with modified smooth muscle fibers of the arteriole wall - called juxtaglomerular apparatus.
What is the function of principal cells?
have receptors for ADH and aldosterone.
What is the function of intercalated cells?
play a role in homeostatic control of blood pH
What happens if one kidney is surgically removed?
If one kidney removed, 2nd kidney enlarges (compensatory hyperplasia).
Enlarged single kidney can filter 80% of amount of blood originally filtered by both.
Define: Glomerular filtration
Water and solutes in blood pass from glomerular capillaries into glomerular capsule and then into renal tubule.
Define: Tubular reabsorption
Tubular Reabsorption - return of water and other filtered substances to the blood stream.
Reabsorption can occur:
1) Between adjacent tubules -
paracellular reabsorption
2) Through an individual tubular cell - transcellular reabsorption
Define: Tubular secretion
Tubular Secretion - process of secreting unwanted substances into the tubules
-some substances (e.g. creatine) are secreted to be eliminated from the body
– others are secreted to maintain a homeostatic balance e.g. hydrogen ions are secreted to balance blood pH.
How much water is filtered through the glomerular capsules of both kidneys each day?
In healthy adults GFR = about 125ml / min in males and 105 ml / min in females. (45 gallons a day in males)
Know the definition of net filtration pressure.
Net filtration pressure (NFP) can be defined as the total pressure that promotes filtration.
Know the definitions of glomerular blood hydrostatic pressure, capsular hydrostatic pressure and blood colloid osmotic pressure. Do these pressures promote or oppose glomerular filtration?
glomerular blood hydrostatic pressure (GBHP) - PUSHING FORCE - The hydrostatic force which is the mechanical pressure exerted on the fluid of plasma by the pumping of the heart during systole and by the elastic recoil and smooth muscle contraction in the walls of the arteries between heart beats during diastole, and especially by the pressure gradient established between the afferent and efferent arterioles delivering the blood to the glomerulus, which tends to push the plasma filtrate from the capillaries of the glomerulus into the capsular space.
capsular hydrostatic pressure (CHP) - RESISTING FORCE - The hydrostatic force which is the mechanical pressure exerted on the plasma filtrate by the the elastic recoil of the glomerular capsule, which tends to push water and dissolved solutes from the plasma filtrate back into the capillaries of the glomerulus; this is the main force slowing the rate of filtrate production within the renal corpuscle itself.
blood colloid osmotic pressure (BCOP) - RESISTING FORCE - The osmotic force (water concentration gradient) which is the result of differences in water concentration between plasma and plasma filtrate, which tends to pull water from the plasma filtrate and back into the plasma in the glomerular capillaries; it results from the failure of most proteins to leave the plasma and move to the plasma filtrate, therefore, as water leaves, the proteins exert an increasing osmotic “pull” on the water in the plasma filtrate.
Know how the glomerular blood hydrostatic pressure, capsular hydrostatic pressure and blood colloid osmotic pressure relate to one another and how to calculate net filtration pressure if given values for each of these different pressures.
Net filtration pressure (NFP) can be defined as the total pressure that promotes filtration.
NFP = GBHP (Glomular blood hydrostatic pressure) - CHP (capsular hydrostatic pressure) - BCOP(blood colloid osmotic pressure)
NFP = 55mmHg - 15mmHg - 30mmHg = 10mmHg
GBHP = glomerular blood hydrostatic pressure CHP = capsular hydrostatic pressure BCOP = blood colloid osmotic pressure
What and where is the macula densa?
The macula densa provides feedback to the glomerulus.
Epithelial cells in thick ascending limb make contact with afferent arterioles of renal corpuscle - become crowded - often called macula densa.
What is the juxtaglomerular apparatus?
Macula densa in contact with modified smooth muscle fibers of the arteriole wall - called juxtaglomerular apparatus.
Define Glomerular Filtration Rate (GFR).
GFR = the amount of fluid formed in all the renal corpuscles of both kidney each minute.
In healthy adults GFR = about 125ml / min in males and 105 ml / min in females.
What will happen if GFR is too high?
If GFR too high - needed substances may pass out of body too quickly.
What will happen if GFR is too low?
If GFR too low - everything may be reabsorbed including some waste products.
FILTRATION FRACTION –
Define the term filtration fraction.
Approximately what is the filtration fraction in a healthy individual?
the ratio of the glomerular filtration rate (GFR) to the renal plasma flow (RPF).
Filtration Fraction, FF = GFR/RPF
The filtration fraction, therefore, represents the proportion of the fluid reaching the kidneys which passes into the renal tubules. It is normally about 20%.
FILTRATION MEMBRANE –
What are the components of the filtration membrane?
glomerular capillary endothelial cells
glomerular basement membrane
podocytes of visceral layer of glomerular capsule
FILTRATION MEMBRANE –
How do the endothelial cells in the glomerulus differ from those in capillaries in other locations?
The endothelial cells of the glomerulus contain numerous pores (fenestrae) that, unlike those of other fenestrated capillaries, are not spanned by diaphragms. The cells have fenestrations that are 70 to 100 nm in diameter. Since these pores are relatively large, they allow for the free filtration of fluid, plasma solutes and protein. However they are not large enough that red blood cells can be filtered.
FILTRATION MEMBRANE –
What is the function of mesangial cells?
Mesangial cells are specialized cells around blood vessels in the kidneys, at the mesangium. They are specialized smooth muscle cells that function to regulate blood flow through the capillaries, usually divided into two types, each having a very distinct function and location:
Extraglomerular mesangial cells
Intraglomerular mesangial cells
FILTRATION MEMBRANE –
What is the function of the basal lamina in the glomerulus?
Filtration barrier – The filtration barrier is composed of the fenestrated endothelium of the glomerular capillaries, the fused basal lamina of the endothelial cells and podocytes, and the filtration slits of the podocytes.
The barrier permits the passage of water, ions, and small molecules from the bloodstream into the Bowman’s space. The barrier prevents the passage of large and/or negatively charged proteins (such as albumin).
The basal lamina of the filtration barrier is composed of three layers. The first layer is the lamina rara externa, adjacent to the podocyte processes. The second layer is the lamina rara interna, adjacent to the endothelial cells. The final layer is the lamina densa which is a darker central zone of the basal lamina. It consists of the meshwork of type IV collagen and laminin which act as a selective macromolecular filter
FILTRATION MEMBRANE –
What type of tissue makes up the basal lamina?
The basal lamina consists of a mixture of collagens, laminin (glycoprotein), perlecan (heparan sulphate glycoprotein), entactin (glycoprotein). These proteins can bind to each other to make a highly crosslinked extracellular matrix as shown in this diagram.
FILTRATION MEMBRANE –
What are pedicels?
Pedicels are the long processes of the podocytes that wrap around the capillaries, and leave slits between them. Blood is filtered through these slits, each known as a slit diaphragm or filtration slit
FILTRATION MEMBRANE –
What are filtration slits?
slits between the pedicels of the podocytes
GLOMERULAR FILTRATION –
How do mesangial cells contribute to the ability of the glomerular capillaries to filter large volumes of fluid?
TBD
GLOMERULAR FILTRATION –
Why are the glomerular endothelial cells leaky? How much more leaky are they than other endothelial cells?
TBD
GLOMERULAR FILTRATION –
What makes the glomerular blood pressure higher than mean arterial blood pressure?
TBD
