Histology of the Urinary System Flashcards
what type of epithelium makes up the parietal layer of bowmans capsule
simple squamous
Parietal layer of Bowman’s capsule
Outer layer that separates the corpsucle from the surrounding tissue. Formed of simple squamous epithelium
Distinct cell types found in the collecting duct
1.) Principle Cells (main cell type) 2.) Intercalated cells of the collecting ducts
Function of the proximal convoluted tubule
1.) Reabsorb amino acids, proteins, glucose, and ions that were filtered from the blood within the corpuscle 2.) Eliminate organic solutes, drugs, and toxins
Does urine get modified in the conducting system?
No- once the urine reaches the conduction system it is no longer modified
what cell type forms the visceral layer of Bowman’s capsule
podocytes (modified epithelium)
What is the loop of Henle
Straight thick and thin tubules that connect the proximal and distal convoluted tules. Consists of ascending (going to the capsule) and decending (going to the medulla) tubules
Urinary Space (Bowman’s space)
space between the parietal and visceral layer of bowmans capsule. The ultrafiltrate is colledcted here before going to the proximal convoluted tubule
What type of epithelium lines the prostatic urethra in males
Transitional epithelium
what makes up the renal corpuscle
consists of glomerulus surrounded by Bowman’s capsule
Describe the cortex and the medulla in a living specimen
in a living specimen the cortex is dark red/brown (90-95% of the blood passing through the kidney is in the cortex) and the medulla is light colored
what drains the glomerulus
efferent arteriole
muscularis of the urinary bladder
forms the detursor muscle. Thicker than in the ureter- inner longitudinal, Middle circularis, sometimes outer longitudinal)
where is the thick descending limb located
in the outer stripe of the outer medulla
What type of epithelium lines the penile (spongy) urethra in men
pseudostratified columnar epithelium (replaced with non-keratinized statifed squamous more distally)
What froms the outer stripe of the outer medulla
thick tubules (ascending and descending)
what structure conducts urine form the urinary pelvis to the urinary bladder? What epithelium lines this structure
Ureter- transitional epithelium
Venous drainage of the kidney
Peritubular capillaries - stellate veins- interlobar veins - arcuate veins
extraglomerular mesangial cells - where are they located? What do they do?
located in the cleft between the afferent and efferent arteriles and the macula densa. Provide structural support and transmit signals from the macula densa (about Cl concentrtaion) to the juxtaglomerular cells
Histologicla features of the proximal convoluted tubule
1.) Formed of cuboidal cells with a prominent brush border (microvilli) 2.) Apical regions have tight junctions 2.) Basal stiations (mitochondira for ion pumps) 3.) Interdigitating lateral membranes
What cell type lines the collecting duct
simple cuboidal epithelium (becomes low columnar distally)
Basal membrane of glomerular capillaries
basal membranes f the endothelial cells of the capillaries and the podocytes fuse to form a single basal lamina
what arteries signify the corticomedullary junction
arcuate arteries
Thick acending limb (Distal Straight Tubule)
lined with simple cuboidal (** NO brush border - can differentiate from the thick descending limb) still has basal striations (mitochondria). Impermeable to water and urea
what cell types make up the distal convoluted tubule
simple cuboidal cells without a brush border. Prominent Basal striations
where does the proximal convoluted tubule begin
urinary pole of bowmans capsule
descibe the tonicity of the fluid that leaves the proximal convoluted tubule (to plasma)
isotonic
Juxtaglomerular cells
modified smooth muscle cell that exhibs secretory activity (granules contain renin) - release of renin results in the production of angiotensisn II (enothelial cells) and aldosterone (adrenal glands)
Thin descending limb
lined with simple squamous epithelium. Highly permeable to water (water can diffuse out)
role of aldosterone in the juxtaglomerular apparatus
stimulates reabsorption of sodium by the principle cells in the collecting duct
Mesingeal cells (functions)
Contractile cells that play a role in 1.) glomerular blood folw (have a receptor for angiotensin II - activation reduces glomerular blood flow) 2.) Structural support for the glomerulys 3.) phagocytosis- clean up the residue and proteins trapped in the basal lamina
Urinary pole
area of bowmans capsule where the proximal convoluted tuble originates from (to drain the urinary space)
which type of nephron has a short loop of henle
cortical nephrons - does not contains an ascending thin segment
are the lateral membranes of principle cells visible on light microscope
Yes- their lateral membranes do not interdigitate (helps to distinguish between collecting ducts and nephron tubules)
what form filtration slits
interdigitated pediciles
Renal pelvis
large resovoir located in the kidney that opens to the ureter
Cortical labyrinth
found in the renal cortex - formed by convoluted tubules (form the squiggly part of the tubules)
ureter muscularis
two or theree layers ( uper longitudinal, middle circular, sometimes outer longitudinal)
Describe the tonicity of the fitrate in the thin descending limb
hyperosmotic - the thin descending limb is highly permeable to water so now the filtrate is hyperosmotic.
what forms the macula densa
the epiltelial cells of the thick ascedning limb adjacent to the afferent arteriole. Epithelia are taller and narrower compared to surrounding cuboidal epithelium.
Function of kidney tubule
1.) Reabsorb materials from the ultrafiltrate 2.) Secrete materials into the ultrafiltrate
how can you distinguish between a nephron tubule and a collecting duct
no lateral membranes seen in the nephron tubule, DO see lateral membranes in the collecting duct
what structure is unique to the cortex
renal corpuscles (spherical structures)
Kidney Calyces
receive urine from collecting ducts - urine flows from minor calyces to major calyces and then into the renal pelvis
Arterial Supply to the kidney (overview)
Renal - Lobar - Interlobar- Arcuate - Interlobular- Afferent arterioles- Glomerular Capillaries- Efferent Arterioles - Peritubular capillaries (cortical nephrons)/ Vasa Recta (juxtamedullary nephrons)
Describe the tonicity of the filtrate in the thick ascending limb
hypotonic due to the transport of sodium and chloride ions from the lumen to the interstitium
three major components of the juxtaglomerular apparatus
1.) Juxtaglomerular cells 2.) Macula densa 3.) Extraglomerular mesangial cells
what structures make up the cortex of the kidney
kidney tubules, renal corpuscles, blood vessels, interstitial connective tissue
Bowman’s Capsule
fenestrated capillaries surrounded by a double layer of epithelium . Blood is brought in by afferent arterioles and then out through the efferent arteriole
Subdivisions of the kidney
1.) Cortex 2.) Outer stripe of the outer medulla 3.) Inner stripe of the outer medulla 4.) Inner medulla
Renal pyramid orientation
base faces the cortex, apex (renal papilla) faces the minor calyx
Collecting duct function
recieves urine form nephrons through the connecting tubule
where is the thin ascending limb found
in the inner medulla
Pedicle
small digit like processes of podocytes. Interdigitate with neighboring pedicles to form filtration slits
connecting tubule
connects the distal tubule to the collecting duct. Lined with simple cuboidal epithelium
What type of epithelium lines the membranous urethra in males
pseudostratified or stratified columnar
Function of the thick ascending limb
transport sodium and chloride ions from the lumen to the interstitium (makes the filtrate hypotonic)
Types of nephrons
1.) Juxtamedullary nephrons 2.) Cortical nephrons
Role of principle cells
located in the collecting duct 1.) Respond to vasopressin (or antiduretic hormone ADH) - open water channels from the lumen of collecting ducts to decrease the volume and increase the concerntration of urine (water flows out due to high osmolarity in the medullary interstitial space) 2.) reabsorb Na and Cl and secrete K
Thin ascending limb
lined with simple squamous epithelium. IMPERMEABLE to water but highlt permeable to NaCl
Medullary rays
Found within the renal Cortex: Radial rays formed by the straight tubules and the collecting duct
Podocytes
form numerous processes that begin from the cell body and cover the surface of the capillaries of the glomerulus
juxtaglomerular aparatus role
important in regulating blood pressure through the production of renin
Where does the thick ascedning limb begin and end
begins in the inner stripe of the outer medulla and travels through the outer stripe into the cortex
describe the capsule of the kidney
DICT (fibroblasts, Myoblasts- not as developed in humans, collagen fibers)
Filtration Slit Diaphragm
Found at the base of the filtration slit. Made up of the glycocalyx of the adjacent cells (forms a negative barrier)
Are the lateral membranes of nephron tubules visible on light microscope
no - interdigitating lateral membranes
The medulla consists mostly of
renal tubules and collecting ducts
Renal pyramids
8-12 per kidney. Formed of renal tubules
What forms the inner stripe of the outer medulla
thick (ascending) and thin (descending)
Visceral Layer of Bowman’s capsule
inner layer that covers the glomerulus.
Function of the Renal Corpuscle
Filtration of blood
Major functions of the kidney
Remove metabolic waste, conserve body fluid, produce urine that helps regulate body fluids, endocrine organ ( EPO, Renin)
Macula densa function
sense chloride concentration in the tubule
what arteries travel between the renal pyramids to the corticomedulary jucntion
interlobar arteries
Vascular pole
area of bowmans capsule where vlood vessels enter and exit the corpuscle
Thick decending limb (Proximal Straight tubule)
lined with cuboidal epithelium. Specialized for absorption (not as much as the proximal convoluted tubule)
Glomerular capillaries
numerous fenestrae (DO NOT have diaphragms)
Role of intercalated cells of the collecting duct
regulate the pH of the urine. Transport H+ and HCO3- in and out of the tubule
Where does the thin descending limb originate
begins in the inner stripe of the outer medulla and travels down to the inner medulla
What forms the inner medulla
mostly thin tubules and collecting ducts
What forms the tip of the renal pyramid
area cribosa - the location where the collecting duct empties into the minor calyx
function of the distal convoluted tubule
reabsorption of Na, Cl, and HCO3
Hilum of the kidney
medially located ventricle fissure where blood vessels, nerves and ureter enter and exit the kidney
what is the functional unit of the kidney
the nephron
what supplies the glomerulus
afferent arteriole
Ducts of Bellini
Large papillary ducts that form from the merger of collecting ducts towards the apex of the pyramid -empty into the minor calyx
Renal columns
projections of cortex between the pyramids of the medulla
what type of epithelium lines the female urethra
initially lined with transitional epithelium- replaced by pseudostratified columnar in the middle with non-keratinized squamous epithelium towards the distal end
vasa recta role
help remove water from the medullary interstitium. Made up of Decending (run to pyramid) and Ascending (run back to corticomedullary junction)
Glands of littre- what are they? Where are they most often found?
pockets of mucosal epithelium lined by mucous secretung cells
Most common in the penile urethral of the male and all along the female urethra
What limb of the loop of Henle enterst the vacular pole of bowmans capsue
Thick ascending limb
Renal Tubules are made up of
1.) Cortical Labyrinth 2.) Medullary Rays
Descibe the tonicity of the filtrate in the thin ascending limb
because the thin ascending limb is permable to ions but impermeable to water, NaCl leaves and the fitrate becomes hyposmotic (hypotonic) - this makes the medullary tissue hyperosmotic.
