Urinary Microanatomy 1 and 2 Flashcards
what makes up the outer and inner layer of the kidney?
outer: fibroblasts and collagen fibers
inner: myofibroblasts
what role does the outer layer of the kidney do?
protection
what role does the inner layer of the kidney do?
contractibility may aid in resisting volume and pressure variations
what makes up the parenchyma
cortex and medulla
what makes up the renal lobe
renal pyramid + adjacent renal cortex and column tissue
what makes up the renal papilla
pyramid protection into the minor calyx
what makes up the area cribosa
surface of papilla w/openings of papillary ducts
describe the path of urine
minor calyx –> major calyx –> renal pelvis –> ureter
what is the uriniferous tubule
nephron + collecting duct
describe the parts of the glomerular capsule
parietal layer: simple squamous epithelium
visceral layer: layer of podocytes that covers the glomerulus
pedicels: secondary processes that interdigitate
–> gaps between = filtration slits
what are mesangial cells?
-modified smooth muscle cells
-secrete ECM for support
-regulate glomerular distension (contraction)
-keep the glomerular filtration apparatus clean from filtration residues (phagocytosis)
what are glomerular endothelium
fenestrated capillaries with no diaphragms
what are glomerular basement membranes
thick basal lamina
collagen type 4, laminin, fibronectin, entacin
what are podocyte filtration slits
filtration slit diaphragm (zipper like frame of nephrin and adhesion proteins)
what type of filter are the fenestrations
size-selective filter
what type of filter are basal lamina
physical barrier and ion-selective filter
what type of filter are filtration slit diaphragm
size-selective filter
describe the proximal tubule
-reabsorption of ions and fluid and secretion of calcitriol
what does calcitriol do
increases the uptake of calcium and its concentration in the blood
describe what you can see on histology for the proximal tubule
-simple cuboidal epithelium
-microvilli (brush border) –> irregular lumen
-lateral and basal folds –> no clear cell borders
-high concentration of mitochondria, vesicles, and lysosomes at the basal surface
what does the thin loop of henle (TLH) do?
-absorption of fluid by countercurrent exchange with vasa recta
-concentration of urine
-simple squamous epithelium –> facilitates countercurrent exchange
-few short microvilli
what does the countercurrent exchange do?
-gradient-dependent transport of fluid into blood
-lower osmolarity in ultrafiltrate and higher osmolarity in blood plasma = fluid transport into blood
describe the distal tubule (DT)?
-selective secretion and absorption of ions (osmoregulation)
-juxtaglomerular apparatus (for sodium)
describe the histology for DT
-simple cuboidal epithelium
-few short microvilli (smaller and more regular borders than the one of PT)
-lateral and basal folds (no clear cell borders)
-abundant mitochondria
describe the osmoregulation in DT
-SECRETION to the ultrafiltrate if there is a HIGH concentration of ions in the blood
-ABSORPTION to the ultrafiltrate if there is a LOW concentration of ions in the blood
describe the blood flow in the afferent arteriole in the kidney
from renal artery to the glomerular capillaries
describe the blood flow in the efferent arteriole in the kidney
from glomerular capillaries to cortical and medullar capillaries
what are efferent arterioles?
-nourish cortical and medullary tissue
-peritubular cortical capillary network
–> reabsorption of ultrafiltrate in cortex
–> endothelium secretes EPO
-peritubular medullary capillary network
–> vasa recta for countercurrent exchange (in TLH)
what is EPO
increases the rate of production of RBC’s in response to falling levels of oxygen in the tissues
what makes up the juxtaglomerular apparatus and what does it do?
-macula densa + juxtaglomerular cells
-sensor that helps maintain sodium homeostasis and regulates BP
what are macula densa
narrower and taller cells than those typical of the distal straight tubule
monitor sodium concentration in ultrafiltrate
secrete ATP, adenosine, NO and PGE2 to stimulate JGC
what are juxtaglomerular cells
specialized smooth muscle cells of the afferent arteriole wall
monitor sodium concentration in blood; secrete renin
what does renin do?
increases the reabsorption of sodium and BP by a higher transfer of fluid from tissues into blood, leading to a greater blood volume
what do the collecting ducts do
conduct urine into minor calices
describe the cortical and medullary collecting ducts
-cuboidal epithelium, large and regular lumen with distinct cell borders
-light cells –> stimulated by ADH to provide water permeability (PREDOMINANT TYPE)
-dark cells –> involved in acid-base balance
–> too basic: secretes carbonate
–> too acidic: secrete H+
describe the papillary ducts
columnar epithelium
what are the two types of nephrons and what do they do?
juxtamedullary nephron: long-looped, performs most urine concentration
cortical nephron: short-looped, performs most filtration/absorption (85%)
describe the general aspects of the urinary passages
-mucosa: transitional epithelium
-lamina propria: fibroelastic CT
-muscularis: smooth muscle, peristalsis
-adventitia: peritoneum or loose CT
describe the transitional epithelium in the bladder
stratified
number of layers increases proximal-distal
-surface cells –> secrete lipids
-intermediate cells
-basal cells
what do urothelial plaques do
lipid layer on the surface of superficial cells
describe the urinary bladder
-highly distensible; rugae
-thicker mucosa
-muscularis (detrusor muscle, multidirectional)
-serosa adjacent to peritoneal reflections
what epithelium is found in the prostatic urethra
transitional epithelium
what type of epithelium is found in the penile urethra
stratified squamous epithelium (non-keratinized)
what type of epithelium is found in the pelvic urethra
stratified/pseudostratified columnar epithelium
where can paraurethral mucous glands be found
near urethra
lined by simple cuboidal epithelium
