143 - Renal Histology Flashcards
Ureters role
Connect kidneys and bladder
Kidney dimensions
11 cm x 4-5 cm x 1-2 cm
Where does the ureter originate?
At the hilum, from renal pelvis
Where do blood vessels and veins enter and leave the kidney?
At the hilum
Blood vessels at the boundary between the cortex and medulla
Arcurate vessels
Number of nephrons per kidney
0.3 to 1.5 million per kidney
Renal corpuscle
Bowman’s capsule + glomerulus
What does the nephron consist of?
Renal corpuscle and tubule
What do tubules drain into?
Collecting duct
Layers of kidney
Capsule, cortex, medulla
*Microscopic view of cortex
Blood vessels, tubules, renal corpuscles
Location in kidney of renal corpuscles
In cortex
Location in kidney of tubules
Loop down into medulla from the cortex, then return
Where do tubules join collecting ducts?
In the cortex, then collecting duct drains into renal pelvis
Two sorts of nephron
- Juxta medullary- base of cortex with tubule that loops deep into the medulla (15%) 2. Cortical - higher in cortex, tubule loops halfway into medulla (85%)
*Appearance of juxtamedullary and cortical nephrons
Is there much connective tissue in the kidney?
No
What lines the interior of Bowman’s space?
Podocytes line capillaries. Parietal cells cover interior of Bowman’s capsule.
Role of mesangial cells
Support glomerulus, provide limited connective tissue
Urinary space
Bowman’s space
Vascular space
Lumen of glomerular capillaries
Filtration in the glomerulus
Movement of fluid, solutes from vascular space into urinary space
Vascular pole
Where capillaries enter Bowman’s capsule
Urinary pole
Where tubule drains Bowman’s space
Orientation of vascular pole and urinary pole
Always 180 degrees from one another
Epithelial type of Bowman’s capsule
Squamous parietal cells
Epithelial type of tubule
Cuboidal epithelium
Crucial point at which ultrafiltrate is formed in kidneys
Interdigitations between podocytes (glycocalyx and slit membranes)
Cell type of podocytes
Epithelial
Filtration barrier
Basal lamina plus slit membrane
*Filtration barrier on glomerular capillaries
Size of molecules that can be filtered
Basal lamina traps molecuels over 69kDa
Aspects of filtration barrier 1 2 3 4
1) Fenestrated capillaries lack diaphragms 2) Basal lamina is very thick 3) Slit membranes have pores of around 3-5 nM 4) Basal lamina traps molecules above 69kDa
Relative thickness of walls of proximal/distal tubules, loop of Henle
Proximal tubule is thick walled Loop of Henle is mainly thin walled Distal tubule is thick walled
Role of kidney tubule 1 2 3 4
• Tubule modifies ultrafiltrate • Recovers water, electrolytes, glucose amino acids, proteins • Secretes creatinine, potassium, protons, ammonium, foreign molecules (eg penicillin) • Result is hyperosmotic urine, rich in urea
Structure of proximal tubule 1 2 3 4 5
• Cuboidal epithelium • Abundant microvilli • Interdigitating cell boundaries • Resorb glucose, aa’s and protein • Part in cortex is proximal convoluted tubule
Ion movement across epithelial cells of proximal tubule 1 2 3 4 5
• Basal membrane folded with many Na+K+ATPases • Na+K+ATPases pump Na+ across cell • Cl- and H2O follow • Na+, Cl- and H2O passively move across apical membrane • Energy hungry - ATP
Which limb of loop of Henle is more water-permeable?
Descending limb more permeable to water
What are walls of loop of Henle permeable to?
Urea, electrolytes
Cell type in thin limbs of loop of Henle
Squamous
Cell type in distal tubule
Cuboidal
Features of distal tubule 1 2 3 4 5 6 7
• Part in cortex is distal convoluted tubule • Cells are cuboidal, lack microvilli • Larger lumens • Have infoldings of basal membrane, more mitochondria than proximal tubules • Impermeable to water and urea but have Cl- and Na+ pumps • Ion pumps make extracellular space hyperosmotic • Blood vessels sweep away recovered water and salts
Aspects of collecting duct 1 2 3 4
• Large lumen, cuboidal cells • Normally impermeable to water and urea • Antidiuretic hormone (vasopressin) makes them permeable to water • Empty into renal pelvis
When can collecting duct become permeable to water?
When dehydrated. Antidiuretic hormone (vasopressin) makes walls permeable to water
Nephrons that can make urine more concentrated than blood
Juxtaglomerular nephrons (not cortical)
What are juxtamedullary nephrons essential for?
Hyperosmotic urine
Role of juxtaglomerular apparatus 1 2 3
• Macula densa is specialised cells of distal tubule wall • Monitor filtrate volume and Na+ concentration • Cause juxtaglomerular cells to release renin
Effect of renin
Acts on angiotensinogen, makes it into angiotensin I, then into angiotensin II
Juxtaglomerular cells cell type
Modified smooth muscle cells
Juxtaglomerular cell role 1 2
• Release renin (enzyme) • Renin converts angiotensinogen (inactive) into angiotensin I, which is converted by other enzymes into angiotensin II, a potent vasoactive hormone
Role of extraglomerular mesangial cells
Unknown
Location of vasa recta 1 2
• Capillaries from efferent arteriole envelope tubule – form vasa recta • Form hairpin loops in medulla among loops of Henle
Role of vasa recta
Crucial in concentrating urine
Organisation of the medulla 1 2 3 4
• Medulla consists of: • Thin and thick walled loops of Henle • Collecting ducts • Capillaries of vasa recta
Epithelial type of ureters
Lined with transitional epithelium
Wall of ureters. 1 2 3
• Lined with transitional epithelium • Distinct lamina propria • Thick muscularis of smooth muscle
Role of muscularis propria in ureters
Smooth muscle contracts in peristaltic waves to force urine into bladder
Role of thick lamina propria in ureters
Prevents escape of urine from ureters
Epithelial lining of bladder
Transitional epithelium
Nervous system controlling bladder
Autonomic nervous system
Epithelial type of urethra
Transitional epithelium and stratified squamous epithelium
Part of body that acts as sphincter in urethra
Where urethra penetrates pelvic floor
Things complicating male urethra
Male urethra also penetrates prostate gland and has a variety of glands, as well as the ejaculatory ducts, emptying into it
