65: Urinary System II (Histo) Flashcards
thick descending portion of loop of Henle
Proximal Straight Tubule
Where is the Proximal Straight Tubule found?
in the medullary ray of the cortex & also in outer medulla
Longer in juxtamedullary nephrons and are found in the medulla
Thin segment of Loop of Henlé
What type of epithelium is in the Thin segment of Loop of Henlé?
thin simple squamous in both ascending and descending limbs in short nephrons
Arteriole and venule rectae form loops parallel to the loop of Henlé (fenestrated capillaries)
Help maintain osmotic gradient in interstitium
Vasa Recta (Countercurrent exchange system)
Hypertonic interstitium
causes loss of water from the arterioles as they descend into medulla and gain water into the venules as they ascend to the corticomedullary
junction
Also called distal straight tubule
Thick ascending limb
Where is the Distal Straight Tubule found?
in the medullary ray of the cortex & also in outer medulla
Functions of Distal Straight Tubule
Transports ions from the lumen of the tubule to the interstitium via active transport
Reabsorbs: Ca2+, Mg 2+, Na+, & HCO3-
Secretes: K+, H+, NH4
Parathyroid regulated Ca2+ reabsorption
Relatively impermeable to H20
Highest Na+/K+ ATPase
activity
What type of epithelium is in the Distal convoluted tubule?
Simple cuboidal epithelium
Fewer and shorter microvilli however extensive basal folds
Apically placed nucleus
Distal convoluted tubule
Modified cells of the distal straight tubule
Located at vascular pole
Senses changes in Na+
concentration w/n lumen of the distal tubule
Macula densa
regulates blood pressure
Juxtaglomerular apparatus
Juxtaglomerular apparatus components
Macula densa
Extraglomerular mesangial cells
(Lacis / Polkissen cells)
Juxtaglomerular cells (JG cells): modified smooth muscle cells of afferent arteriole Produce renin ( cleaves angiotensinogen to angiotensin I)
potent vasoconstrictor
stimulates aldosterone secretion from adrenal cortex
angiotensin II
What does aldosterone stimulate?
reabsorption of Na+ and secretion of K+ by
connecting tubules and collecting ducts
Connecting tubules
Connect DCT to cortical collecting duct
Contain cells from DCT and CD (principal
cells)
Play important role in secretion of K+ into
lumen
Found in the medullary ray of the cortex
Cortical collecting duct
What leads into cortical collecting duct?
Connecting tubules
All nephrons within a renal lobule drain into ____ cortical collecting duct
one
What epithelium makes up cortical collecting duct?
simple cuboidal epithelium
What epithelium makes up Medullary collecting ducts?
simple cuboidal transitions to simple
columnar epithelium
Ducts of Bellini
several Medullary collecting ducts that merge to form papillary ducts
Most abundant cells of collecting ducts
Pale staining
true basal infoldings
Single primary cilium: short scattered microvilli
Abundant ADH regulated Aquaporins
(AQP- 2) channels
Light or principal cells
least abundant cells of collecting ducts
Not present in the inner medulla
Microvilli and microplicae at apical
cytoplasm
Secretion of H+ or bicarbonate
Dark or intercalated cells
Where do Medullary collecting ducts empty?
at the area cribrosa (a
region having a sieve-like appearance) on the apex of a renal papilla
connective tissue of
the kidney which surrounds the nephrons, ducts and neurovasculature
Renal interstitium
What are the two main cell types of cortical interstitium?
fibroblasts and
mononuclear cells
resemble myofibroblasts
present along the
descending vasa recta
Medullary interstitium
functions to transit and store urine
Excretory Passages
What are some Excretory Passages?
minor and major
calices, renal pelvis, ureter, urinary bladder and urethra
Excretory passages have _____, _______, and ______
mucosa
muscularis
adventitia
Transitional epithelium
Superficial: single layer of dome
shaped (umbrella) cells, shape of the cell depends on the
filling state
Intermediate (pear shaped cells) abundant desmosomes
Basal layer: stem cells
Abundant tight junctions: impermeable to salts and water
on the apical surface of superficial cells of Urothelium (contains crystalline uroplakin which contributes to the permeability barrier)
Urothelial plaques
Apical scalloped surface of Urothelium covered by the ______
Uroplakin
Fusiform vesicles of Urothelium
Flattened elliptical vesicles
conduit between the renal pelvis and the urinary bladder
Ureter
Layers of Ureter
–Mucosa: Epithelium + lamina propria
–Muscularis:
upper two-thirds, has longitudinal layer surrounded by circular layer of
smooth muscles
lower one-third has an
additional longitudinal smooth muscle layer towards the outside
(Contraction of these muscle layers produces peristaltic
waves)
–Adventitia
Urinary bladder cells
Mucosa: Epithelium + fibroelastic CT
_______ of the bladder is thick and consists of smooth muscle arranged in an inner longitudinal, middle circular
and outer longitudinal layer (oblique orientation of muscles)
Muscularis
Conveys urine from the bladder to be evacuated outside
Urethra
Segments of Male urethra
–Prostatic : transitional epithelium
– Membranous: pseudostratified columnar
– Spongy : Pseudostratified columnar until the fossa navicularis where it is lined by
stratified squamous epithelium
– Mucus-secreting glands (of Littre) are located in the subepithelial connective
tissue throughout the passage.
Segments of Female urethra
short compared to male’s
Initial part lined by transitional epithelium and
terminal part by stratified squamous epithelium
Muscularis is composed of an inner longitudinal and an outer circular layer of smooth muscle
