11/27: Urinary System Flashcards
The kidney has several important homeostatic, hormonal, and metabolic
functions that include:
- The maintenance of water and electrolyte homeostasis.
- Regulation of acid-base balance in conjunction with the respiratory system.
- Excretion of metabolic waste products, especially the toxic nitrogenous
compounds. - Production of renin for blood pressure control and erythropoietin, which
stimulates red blood cell production in the bone marrow. - Conversion of vitamin D into active form for the regulation of calcium
balance
How many segmental (lobar) aa are per kidney?
5
Each lobar artery is an?
“end artery”
What does each segemental artery give off?
Interlobar aa
arcuate aa
intralobular aa
afferent arterioles
What drains the glomeruli and forms capillary networks?
Efferent arterioles
What drains cortical nephrons and forms peritubular capillary network while taking up substances resorbed by tubular epithelium?
Efferent arterioles
What is the functional unit of the kidney?
Nephron
What are the two main components of the kidney?
Renal corpuscle and renal tubule
What filters blood plasma?
renal corpuscle
What modified filtrate to form urine?
Renal tubule
What is the nephron composed of?
Renal corpuscle
Proximal convoluted tubule
Loop of henle
Distal convoluted tubule
Collecting tubule/duct
Where are capillaries found around?
Proximal/Distal convoluted tubule and loop of henle
What capillaries are found around PCT/DCT? LH?
Pertibular capilaries; Vasa Recta
What capillaries are found around LH?
Vasa recta
What filters fluid from blood?
Renal corpuscle
What portion modifies filtrate into urine?
Tubular portion
The type of nephron depends on?
Location in cortex and of their henle loop
What types of cortical can there be?
Subcapsular (short loops)
Midcortical (inetermediate)
Juxtamedullary (long)
What is the role of the kidneys?
Maintenance of internal fluid composition and volume (internal environment)
Capillaries invaginate into?
Bowman’s capsule
What are the capillaries in contact with?
Visceral layer (podocytes)
What epithelium is the parietal layer?
Simple squamous epithelium
What is the renal corpuscle separated by?
Urinary (bowman’s) space
What is the function of mesengial cells?
Secrete mesangial matrix, vasoactive factors, and cytokines
What are the main structural compinents of the mesangial matrix?
Collage type IV
Laminin
Fibronectin
Proteoglycans
What is the primary phagocytic function of mesangial cells?
Remove trapped residues and aggregated protein from the basement membrane, thus keeping the filter free of debris
What has been suggested in changing the filtration pressure of the glomerulus?
Contractile properties of mesangial cells
Where are extraglomerular mesangial cells located?
Between the afferent arteriole and the efferent arteriole towards the vascular pole
Where are intraglomerular mesangial cells located?
Inside the glomerulus in between the capillaries
Fluid from capillaries leaks into the urinary space through?
Complex filtration barrier
What are the 3 components of the filtration barrier?
- Fenestrated capillary endothelium
- Basal lamina (basement membrane)
- Podocytes of the visceral layer of bowman’s capsule (epithelial cells (podocytes) with pedicles (foot projections))
What is on some components of both basal lamina (glycoprotein podocalyxin) and surface of podocyte processes?
High polyanionic charge
What type of capillaries are glomerular capillaries?
Fenestrated
Large pores not covered by a diaphragm
What are glomerular capillaries permeable to?
Water, urea, glucose, and small proteins
What is the barrier on glomerular capillaries for?
Formed elements in blood and large macromolecules
What does the lamina rarae contain?
Type IV collagen
Laminin
Fibronectin
Negatively-charged proteoglycans
What crosses the basal lamina freely?
Water, ions, and small organic molecules
What crosses the basal lamina reasonably freely?
Peptide hormones and small proteins
What does each pedicel have?
Glycocalyx of negatively-charged podocalyxin
What are pedicels separated by?
Cleft filtration slits
What are pedicles covered by?
Porous slit diaphragm made of protein nephrin
What does the pedicel additionally act as?
Barrier to large macromolecules, proteins, negatively charged molecules and blood cells
What have phagocytic functions?
Podocytes
Where does blood enter glomerulus via?
Afferent arterioles
What forces fluid through fenestrae of capillary endothelium?
Arteriole pressure
What is trapped by the basal lamina?
Large molecules
What are stopped by the basal lamina and podocytes?
Negatively charged molecules
What passes through pores in slit diaphragm to enter the urinary space -> PLT?
Fluid
What is the site of “bulk operations”?
Proximal convoluted tubule
Where does the site of bulk operations begin?
At urinary pole
What is the proximal convoluted tubule the primary site for?
Water resorption, removes 75% of water and ions (Na, Cl)
What is found only in the cortex?
Proximal convoluted tubule
What is the proximal convoluted tubule lined by?
Eosinophilic cuboidal/low columnar epitheliam
What is in the center of the proximal convoluted tubule?
Centrally placed nucleus
What is the border of a proximal convoluted tubule?
Microvilli and well-defined brush border
Describe the lateral border of the proximal convoluted tubule
Indistinct due to interdigitations
The proximal tubule has extensive reabsorption of…
glomerular filtrate (microvilli)
The proximal tubule has a reduction in…
fluid volume
What is endocytosed in the PCT?
Proteins and small peptides
What 3 things pass through the proximal tubule via a small transmembrane channel?
Na+ (active transport)
Cl- (passive diffusion)
H2O (AQP-1, aquaporin-1)
