Flashcards in Downing: Urinary System Deck (83):
What are the components of the urinary system?
What are the functions of the urinary system?
1. Eliminate UREA and NITROGENOUS waste
2. Maintain FLUID blance
3. Maintain SALT balance
4. Control acid-base balance
5. ENDOCRINE fxn
How mechanisms does the kidney use to carry out its functions?
1. filtration of blood plasma
2. passive diffusion
3. active secretion
4. selective reabsorption
5. exchange of hydrogen ions/formation of ammonia through acid-base regulation
What are the three layers of the capsule? What are their characteristics?
Innermost- capsule covers surface of kidney
middle- thick layer of fat
outermost- ct which binds kidney to surface structures
What passes through the hilus?
nerves and lymphatics
What does the cortex contain?
What does the medulla contain?
6-18 pyramids (base lies adjacent to cortical tissue; tips (renal papillae) point towards minor calyces of renal pelvis
What is the area cribrosa?
Tip of the papilla
Perforated by 10-25 small openings where hte terminal segments of the uriniferous tubules open into the minor calyx
What are the renal columns?
Cortical substance that extends BETWEEN the medullary pyramids
What is the renal sinus?
Cavity/potential space occupied by:
major and minor calyces
What does a kidney lobe consist of?
Medullary pyramid and surrounding cortical tissue
What does a kidney lobule consist of?
Straight tubules in a medullar ray and the cortical substance immediately surrounding the tubules.
What does the parenchyma consist of?
uriniferous tubules and blood vessels
What does a nephron do?
What are the two layers of bowmans capsule?
Parietal layer (capsular epithelium)
Visceral layer (glomerular epithelium)
Where is the parietal layer in bowmans capsule and what is it composed of?
Begins where visceral layer is reflected at the vascular pole and is continuous with the proximal convoluted tubule at the urinary pole
What ishte visceral layer composed of?
PODOCYTES that are closely applied to the GLOMERULAR endotehlium (separated only by a thick basal lamina)
What are the two distinct poles of bowmans capsule?
1. vascular (eff and aff arterioles enter and exit)
2. Urinary (parietal epith is continuous with cuboidal epith of prox CT)
What is the capsular space in bowmans capsule?
Lumen of hte tubule between the visceral and parietal epithelial layers.
Where does glomerular filtrate originally enter?
Capsular space (continuous with lumen of the proximal convoluted tubule)
What is the glomerulus?
Arterial vascular aparatus
Aff arterioles> fenestrated capillaries> capillaries reunite and form the eff arteriole
What composes the visceral epithelial layer of bowmans capsule?
What are hte components of a podocyte?
1. Primary processes
2. Secondary processes- interdigitate w/ elements of corresponding processes and surround the basal lamina of capillary endotehlium. Creates slit pores).
What are the components of the filtration apparatus?
1. Capillary endotehlium (fenestrated capillaries)
2. Basal lamina (find proteins and glycoprotein matrix)
3. Slit pores (between adjacent interdigitating foot processes of podocytes)
How do the endothelial pores act as a barrier in the filtration apparatus?
Stop CELLULAR components of blood and large particles of plasma
How does the basal lamina act as a barrier in the filtration apparatus?
1. holds back LARGE molecules
2. Hold back some CHARGED molecules
What are mesangial cells?
Similar to a pericyte--occur where adjacent capillaries are close together so that podocytes can't totally surround them
What do mesangial cells do?
1. keep glomerular filter free of debris
2. provide support where basement membrane is lacking
3. basement membrane turnover
What makes up the bulk of the renal cortex?
Proximal convultuted tubule and proximal straight tubule
What are tubules comprise of?
Simple high cuboidal OR
two columnar epitheliium
How is the cytoplasm of cells comprising the tubules unique?
More acidophilic than other tubules
What is seen on electron microscopy of proximal tubules?
1. BRUSH BORDER (closely packed microvilli)- FUZZY
2. Apical canaliculi
3. Lateral cell membranes are highly folded
4. MITOCHONDRIA in basal half of cell
5. Basal processes of cells undermine each other and make it look like there is extensive infolding (striations)
What percent of water and NaCL is reabsorbed from the tubule?
Na is ACTIVELY transported out, Cl and water follow
What else is reabsorbed in the tubule?
Glucose and amino acids
Proteins via pincocytosis
What happens to the epithelium in the thin segment of the loop of Henle?
1. APRUPT change from simple cuboidal to SIMPLE SQUAMOUS
2. Brush border stops
3. Nuclei bulge into lumen of the tubule
What surrounds the thin segment of the loop of Henle?
Capillares- vasa recta
Efferent vessels of the juxtamedullary glomeruli
What happens to the epithelium of the distal straight tubule (thick segment)?
1. EpithelIum becomes SIMPLE CUBOIDAL
2. LESS acidophilic
3. LARGE LUMEN than proximal
4. MORE NUCLEI seen around circumference of tubule.
What is the macula densa?
Eliptical disc of elongated cells in wall of ascending limb where it contacts the afferent arteriole
Where does the distal convoluted tubule begin?
At the vascular pole of the renal corpuscle
How does the distal convoluted tubule differ from the proximal tubules?
(similar to ascending thick segment)
What does ADH do in the distal convoluted tubule?
INCREASES permeability of cells to water>
forms concentrated urine
What does hte arched region of the collecting tubule do? Where is it?
Receives urine from distal convoluted tubule
What does the straight region of the collecting tubule do? Where is it?
Medullary rays and medulla
Unites with adjacent tubules as they run toward hte renal papillae>
form larger collecting ducts called papiallry ducts
What do papillar ducts do?
Open on the area cribrosa at the apex of each papila
What is the epithelium of the collecting tubules?
Simple cuboidal to low columnar
What are the two types of cells in the epithelium of collecting tubules?
1. Light cells (CD cells)
2. Dark cells (IC cells)
Which cells of the collecting tubules play a role in acid base balance by resorption/secretion of bicarbonate and acid?
Describe the nuclei and cytoplasm of a collecting tubule.
Nuclei- one level
cytoplasm- clear/light staining
What is the function of the collecting tubule?
Water resorption (ADH)
Acid base balance
What are the juxtaglomerular cells?
Wall of AFF arteriole (among smth muscle cells)
What do juxtaglomerular cells contain?
What is the macula densa?
Densely packed cells of the distal tubule
Where is the macula densa located?
Adjacent to juxtaglomerular cells at the vascular pole
Where are extraglomerular mesangial cells located?
In the angle between aff and eff arterioles at vascular pole of the glomerulus
What is the function of the juxtaglomerular apparatus?
How does the JGA maintain bp
Decrease in BP>
JG cells secrete renin
Jg cells respond to FALLING bp
What does the macula densa do in the distal tubule?
Monitors the NA concentration
What happens to Na when there's low BP?
Decrease in plasma Na conc>
low plasma Na>
What does angio II do directly?
Constricts arterioles> increased BP
What does angio II do indirectly?
Stimulates zona glomerulosa of adrenal cortex> release aldosterone> distal kidney tubles> Na/Water resorption> increased BP
Describe the arterial blood supply.
Describe the path from the juxtamedullary glomeruli to the renal vein.
Describe the path from the juxtacapsular or mid cortical glomeruli to the renal vein.
cortical peritubular capillary network>
What are the two types of vasa recta?
1. Arteriolae rectae (descending vessels, CONTINUOUS epithelium)
2. Venae rectae (ascending vessels, FENESTRATED epithelium)
What is the nerve supply to the kidneys?
How does constriction of afferent arterioles affect filtration rate/urine production?
REDUCES filtration rate and DECREASES urine production
How does constriction of efferent arterioles affect filtration/urine prodution?
INCREASES filtration and INCREASES urine production
What does a loss of SNS innervation do?
Leads to increased urinary output
Is extrinsic nerve supply essential for normal renal function?
NO- transplanted kidneys function normally
What are the characteristics of the mucosa of the ureter?
1. Epithelium (transitional)
2. Basement membrane
3. lamina propria- well developed
What are the 4 layers of the ureter?
Describe the muscular coat of the ureter.
Upper 2/3- two layers of smooth muscle (inner-longitudinal, outer- circular)
Lower 1/3 (outer, longitudinal)
How do peristlatic waves affect the ureter?
Move urine down from renal pelvis to bladder
What is the adventitia of the ureter composed of?
Rich blood supply/lymphatic vessels
nerve plexuses (some sensory fibers)
What are the 4 layers of the urinary bladder?
What are the 3 layers of the mucosa?
1. Epithelium (transitional)
2. basement membrane
3. lammina propria
What are the three distinct layers of the muscular coat of the bladder?
1. inner longitudinal
2. middle circular
3. outer longitudinal
What forms the internal urethral sphincter?
The middle circular layer of hte muscular coat ( thickened around orifice of the urethra)
What forms the adventitia of the bladder?
What plexus innervated the bladder?
Sends numerous fibers into muscular coat
HOw long is the female urethra?
short (2-3 cm)
What are the components of the female urethra?
1. Mucosa (transitional near bladder and stratified squamous the rest of hte way)
2. muscular wall (primarily smooth muscle w/ some mixing with skeletal at end)