Urinary System II Flashcards
Fluid filtered from the capillary blood into the bowman’s space and forms the primary urine
Filtrate
3 layers of the glomerular flitration membrane capillary wall
1) endothelium - with fenestrae
2) basement membrane
3) epithelial podocytes
Allows the fast movement of water through the epithelium of endothelial cells in the glomerular capillaries
Aquaporin 1 water channel
Principal component of filtration barrier - acts as a physical barrier and ion selective barrier
Glomerular Basement Membrane
Glomerular basement layers
Footlike extensions with filtration slits between extensions
specialized epithelium of visceral layer
Podocytes
composed of proteins: nephrin, CD2-associated protein, and podocin
Mutations in the glomerular podocytes can cause
Nephrotic syndrome
Glomerular Filtration Membrane:
(1) prevents the passage of large protein molecules
(2) prevents the passage of RBCs & WBCs
(3) prevents the passage of medium sized proteins
(1) glomerular basement membrane
(2) endothelium of glomerulus
(3) podocytes
Acts as the physical filter of the glomerular basement membrane
lamina densa
Act as the charge barrier of the glomerular basement membrane
via anionic sites
laminae rarae
Fate of filtration
Flat cells with fine cytoplasmic processes - controls glomerular blood flow
forms part of the juxtaglomerular apparatus
mesangial cells
Mesangial cells with their extracellular matrix
also attached to the capillaries and glomerulus
Mesangium
Mesangial cells located outside the corpuscle along the vascular pole
Lacis cells
3 cellular components of the Juxtaglomerular Apparatus
1) macula densa
2) extraglomerular mesangial cells
3) juxtaglomerular cells or granular cells
Specialized smooth muscle cells of afferent arteriole which contains renin in secretory granules
Juxtaglomerular cells
Location of the macula densa
terminal distal straight tubule adjacent to renal corpuscle
Site of blood pressure regulation via renin-angiotensin-aldosterone (RAA) system
Located at the vascular pole of Bowman’s capsule
Juxtaglomerular apparatus
Cells act as baroreceptors and chemoreceptors
(1) Has chemical composition similar to that of blood plasma but contains almost no proteins
(2) contains water, electrolytes as well as waste products (urea, uric acid, creatinine) and breakdown products of various substances
(1) primary urine - ultrafiltrate
(2) final urine
Determine which kidney tubule, given the function
1) reabsorbs solutes and water from the filtrate
2) reabsorbs Na and Cl from the filtrate into the interstitial fluid
3) filters small solutes from the blood
4) selectively secretes and absorbs different ions to maintain blood pH and electrolyte balance
5) aquaporins allow water to pass from the filtrate into the interstitial fluid
6) reabsorbs ions, water and nutrients; removes toxins and adjusts filtrate pH
1) collecting duct
2) ascending loop of Henle
3) glomerulus
4) distal convoluted tubule
5) descending loop of Henle
6) proximal convoluted tubule
Urine formation process
1) filtration
2) reabsorption
3) secretion
Cells of the proximal convoluted tubule
simple cuboidal epithelium w/ eosinophilic granular cytoplasm
Have microvilli on their luminal surface
actively reabsorbs from the filtrate, reabsorption of 60-65% of the water via osmosis
Initial and major site of reabsorption
- reabsorbs nearly all glucose, amino acids, and polypeptides
- proteins and polypeptides are endocytosed
- recovers most of the fluid from the ultrafiltrate of blood
Proximal convoluted tubule
Maintains the adhesion between neighboring cells at the proximal convoluted tubules
tight narrow junctions and zona adherens
Thin segment of the loop of Henle epithelium
flattened squamous epithelium
no capacity for active transport
allows free diffusion of water but is impermeable to NaCl
Thin descending limb of LOH
Highly permeable to water due to presence of aquaporins; less permeable to Na and urea
allows passive diffusion of NaCl into the interstitium; impermeable to water
via Na/K, Cl cotransporters
Thin ascending limb of LOH
take up water from the medullary interstitium and return it to the general circulation
Vasa recta
4 types of epithelial cells - thin limb
Active transport of NaCl from cell to lumen; impermeable to water due to thick glycocalyx
appear as cuboidal epitehlium
Glycocalx composed of glycoprotein tamm-horsfall protein
Thick ascending limb - distal straight tubule
Secretes potassium ions, hydrogen ions and ammonium; reabsorbs sodium, chloride, bicarbonate ions, and water (at the influence of aldosterone & ADH)
converts ammonia to ammonium ion
Distal convoluted tubule
Histology of the Distal convoluted tubule
- simple cuboidal epithelium with out brush border
- cell nucleus at apical border
- lumen is larger than proximal convoluted tubule
- paler cytoplasm
adjacent to the afferent arteriole
Drain urine from nephron to renal pelvis
Collecting tubule and duct
Epithelium of collecting tubule and duct
squamous to cuboidal simple epithelium
Types of cells in the collecting ducts
1) light cells
2) dark cells
Cells of the collecting duct
posses abundance of ADH regulated water channels - responsible for water permeability of collecting duct
Light cells or collecting duct cells
pale staining, short microvilli with single primary cilium
Cells of the collecting duct
Principal cells of the system
Light cells
Secretes hydrogen ions and bicarbonate
dark cells or intercalated (IC) cells
Blood supply to the kidney
(True/False)
The efferent arteriole carries oxygenated blood
True
These capillary networks are responsible for the actual exchange of gasses and nutrients
Vasa recta
Capillaries in the cortex
Peritubular capillaries
Innervation of the kidney
Renal plexus
Long, fibromuscular tubes that conduct urine from the kidneys to the urinary bladder
25 cm in length
Ureters
Ureter wall histology
1) mucosa - transitional epithelium on lamina propria
2) muscularis externa
3) adventitia
Glands at the ureter’s lamina propria
tubular mucus glands
Muscularix externa of the ureter
- upper - inner longitudinal and outer circular
- lower - innermost longitudinal, middle circular, outer longitudinal
(True/False)
The urinary bladder is oval shaped when filled with urine and shaped like an upside-down pyramid when empty
True
Functions as a funnel and directs urine to urethra
Trigone
2 urethral sphincter
1) internal urethral sphincter - smooth muscle
2) external urethral sphincter - skeletal muscle
Superior sphincter surrounding the neck of the bladder - where urethra originates
internal urethral sphincter
Urethral mucosa
Transitional epithelium that transitions to stratified squamous at external urethral orifice
Houses mucin producing urethral glands
Have cavernous tissue spaces that are typical of erectile tissue
urethral submucosa
urethral muscularis layer
- inner longitudinal
- middle circular
- outer longitudinal
smooth muscle that later transitions to skeletal distally
