Flashcards in L17 - Histology of the Urinary system Deck (108):
What is the principal functions of the urinary system?
Maintenance of water, electrolyte and acid-base homeostasis
What is the normal expected urine volume per day?
What is Polyuria (too many) / oligouria (too little) a homeostatic disorder of?
Homeostasis of urine production
What are the most important toxic metabolites that require breakdown in body?
Nitorgen-containing compounds as products of protein breakdown
e.g. urea and creatinine
What actions of the urinary system do the principal functions involve? (what happens to the urine?)
Production, passage, storage and voiding of urine
What is secreted by the juxtaglomerular cells that regulate blood pressure?
renin (angiotensinogenase): cleaves angiotensinogen > makes angiotensin I > regulate blood pressure
What is the consequence on urine production volume by lack of ADH in Diabetes insipidus?
Lack of ADH > lose ability
to reabsorb water from distal convoluted tubule and collecting ducts >
large volume of urine production (up to 22 liters/day)
What are the four structures that make up the urinary system?
What is the kidneys' function?
Control urine production and urine composition
How are the ureters and urethra similar in function?
Both for passage of urine
What is the function of the urinary bladder?
storage and voiding of urine
How would you describe kidneys as an organ?
Kidneys are compound tubular glands covered by a thin capsule of dense connective tissue and embedded in a layer of fat
(renal capsule> perirenal fat >renal fascia> pararenal fat)
What is the location and level of the kidneys?
Right kidney is inferior to left kidney
What is the renal fascia made of?
thin layer of loose connective tissue
What passes through the hilum of the kidneys?
renal artery / vein (more anterior), nerves, ureter
What is the renal sinus?
cavity within the kidney
occupied by the renal pelvis, renal calyces, blood vessels, nerves and fat
What are the pyramids in the kidney?
The pyramids made of tubules that transport urine from the cortex to the calyces
Where and what is renal papilla?
where the renal pyramids in the medulla empty urine into the minor calyces
How is renal papilla duct formed?
medullary collecting ducts converging to form a papillary duct
How is the renal pelvis formed?
Fused major calyces
The kidney can be divided functionally into which two sections?
What marks the start of the transport portion of the kidney?
major and minor calyces
What and where are the three physiological constrictions along the ureter?
Pelviureteric junction- after renal pelvis
Pelvic brim- crossing with external iliac artery
Uretero-vesical junction- before entrance into bladder
What artery does the renal artery branch from?
What is the sequenc eof circulation from the renal artery to micro-circulation?
Renal artery > Segmental artery > InterLOBAR artery > Arcuate artery > interLOBULAR artery > microcirculation
What are the arteries before and after arcuate artery in kidney?
InterLOBAR is before
interLOBULAR is after
What preceeds interlobar artery in kidney?
How are interlobar arteries arranged in kidney? (where does it lead to)
ascend within renal
columns toward cortex
Where are do arcuate arteries exist in kidneys?
arch over base of
Where do interLOBULAR arteries end up in the kidney?
Is the nephron open-ended or blind-ended?
What is the uriniferous tubule of the kidney? What structures does it consist of?
The functional unit of the kidney that collects and conducts urine
Consists of a nephron + collecting tubule
(Renal corpuscle + PCT + Loop of Henle + DCT + collecting tubule)
Are the two components of the uriniferous tubule from the same embryonic origin?
Where are distal and proximal convoluted tubules located relative to the renal corpuscle?
PCT and DCT are adjacent to the renal corpuscle
What are the two types of nephrons? How are they distributed?
Does the loop of Henle of cortical nephron extend into the medulla? How about juxtamedullary nephrons' loop of Henle?
Cortical nephron: Yes but not deep into medulla
Juxtamed. nephron: Yes and deep into medulla
What forms the peritubular capillary network?
Efferent glomerular arterioles of the CORTICAL nephron
What is the difference in location between the renal corpuscle of cortical vs juxtamedullary nephron?
Renal corpuscle nearer to periphery of cortex
Renal corpuscle near cortical medullary border/ in the juxtamedullary cortex
What is the sequence for urine drainage inside the kidney?
nephron > collecting ducts > papillary ducts >
minor calyses > 3 major calyses > renal pelvis
What structures does the glomerular filtrate go through inside the uriniferous tubule?
Renal corpuscle > Proximal convoluted tubule > Loop of Henle > Distal convoluted tubule > Cortical Collecting duct > Medullary collecting duct
What is the Medullary Ray made of ?
Consists of Collecting tubule and segments of the loop of Henle of CORTICAL nephron
What is the difference between the structures formed from the efferent glomerular arteriole of the cortical and juxtamedullary nephrons?
Cortical nephron efferent glomerular arterioles form the peritubular capillary network
Juxtamed. nephron efferent glomerular arterioles form the VASA RECTA
What is the difference between the structures surrounded by the peritubular capillary network and Vasa Recta?
Peritubular capillary network surrounds the convoluted tubules of nephrons in the cortex
Vasa Recta surrounds the limbs of Loop of Henle
In which of the two types of nephrons is the Loop of Henle longer?
The juxtamedullary nephron has longer Loop of Henle
The cortex and medulla of kidneys is divided into which 4 sections?
Cortex- Outer cortex, juxtamedullary cortex
Medulla- Outer medulla, Inner medulla
What structures of nephron is prominent in the medulla?
Only Loop of Henle and Collecting duct
Are the renal corpuscle and convoluted tubules of juxtamedullary nephron located in the Medulla?
No, located in the juxtamedullary cortex
What is the sequence of venous vessels from microcirculation to inferior venan cava in the kidneys?
Microcirculation / peritubular capillaries > InterLOBULAR vein> Arcuate Vein> InterLOBAR vein> Renal Vein > Inferior VC
(No segmental vein)
Are the peritubular capillary networks continous with Vasa Recta?
Yes, the two capillary beds are linked
This is called Portal Circulation
What is the sequence of vessels in the microcirculation of the kidney?
Interlobular artery > Afferent arteriole > glomerulus > Efferent Arteriole > then to:
1) Peritubular capillaries > Vasa Recta > either arcuate vein or interlobular vein
2)Directly to interlobular vein
3)to Peritubular caplillaries > Interlobular vein
Which two veins can Vasa Recta lead to?
Which two vessels can Peritubular capillaries lead to?
Which two vessels can efferent arteriole lead to?
What is the path that Vasa Recta (formed by juxtamedullar nephron efferent arterioles) takes in the kidneys?
course along with loops of Henle into the medulla > then to cortex
Where in the kidney are Arcuate A/V located?
What is located between renal pyramids?
Is corticomedullary junction same as juxtamedullary cortex?
What are the epithelium types in parietal (outer) and visceral (inner) Bowman's capsule?
Parietal layer = simple squamous epithelium
Visceral layer = specialized podocytes, highly specialized simple squamous epithelium
What is the role of Mesangial matrix?
Produce Extra-cellular matrix for structural support of the glomerulus
What is glomerular tuft?
20-40 loops of fenestrated capillaries
In visceral epithelium, what structures does the plasma ultrafiltrate pass through from the glomerular capillary to urinary space?
Glomerular capillary endothelium > Fenetration > Basal Laminae (fused basement membrane between podocyte and endothelial > Filtration slit diaphragm between podocyte pedicels > Urinary space
What are pedicels of podocytes?
Finger-like projections, space between is called filtration slit
What 2 components make up renal corpuscle?
Glomerulus and Bowman's capsule
What structure faces the vasuclar pole and what faces the urinary pole?
Vascular pole: DCT, Afferetn and Efferent arterioles
Urinary pole: PCT
What are juxtaglomerular cells?
muscle cells of
What is the role of juxtaglomerular cells?
(converts angiotensinogen to angiotensin I > angiotensin II)
Act as mechanoreceptors, sensitive to BP
What are macula densa cells?
specialized / modified epithelial cells of distal
What is the role of macula dense?
Sensitive to osmolarity (e.g. amount of NaCl in distal
convulated tubules) and volume of filtrate =
regulates glomerular filtration rate
What cells has gap junction with juxtaglomerular cells and lies bteween macular densa and glomerulus?
Lacis cell (extraglomerular mesangial cells)
What is the Proximal convoluted tubule epithelium?
3 special features?
1) Microvilli (at luminal
2) Mitochondria in basal infoldings/invaginations
3) Apical tight junctions + intercellular junctions (alternating ridges along basal part of cell)
What microscopy features do proximal convoluted cells have?
eosinophilic than DCT
No distinctive cell border
Does PCT reabsorb most of water and solutes?
Yes about 70% of all reabsorption
What is reabsorbed in the PCT?
Actively reabsorb Na+ ,amino acid, (small) proteins,glucose
Reabsorb water by osmosis
What is the pathway of reabsoption of PCT?
tubule cell >
interstitial fluid >
What is the chang ein epithelium of Loop of Henle from descending limb to ascending limb?
1. Initial part of descending limb: simple cuboidal epithelium
2. Latter part of descending limb: simple squamous epithelium
3. Initial part of ascending limb: simple squamous epithelium
4. Distal part of ascending limb: simple cuboidal epithelium
Epithelial cells interlock with each other
What is the role of Loop of Henle?
Create hypertonicity gradient between collecting ducts and interstitium
When is renin secreted? What 2 cells is it made and secreted by?
When BP is low:
1) Detected by macula densa by decreased sodium concentration in DCT due to decreased glomerular filtration rate
2) Detected by Juxtamedullar cells (mechano-receptors)
What is the difference in water and solute permeability between ascending and descending limbs of the Loop of Henle?
Descending= impermeable to salt but permeable to water
Ascending pumps of salt but impermeable to water
What is the pairing of vasa recta to the limbs of the loop of henle?
Descending limb coupled with ascending Vasa Recta
Ascending limb coupled with descending Vasa Recta
Interstitium in between
DCT epithelium? 3 sepcial features?
Simple cuboidal epithelial cells with:
1) Mitochondria in basal folding/ invagination
2) Intercellular junction (impermeable to water)
3) Sparse microvilli
How does DCT cells compare to PCT cells morphological?
Shorter, appear less in a section
Less brush border on luminal surface (few/sparse microvilli)
More distinctive border
What is the function of the DCT?
Achieve acid-base and water balance by:
Absorption of water, Na+, HCO3-
Excretion of K+ and H+
Which of the DCT's membranes are responsible for transport of which ions?
Apical membrane: countertransport (reabsorb Na+, Cl-; excrete H+, K+)
Basal membrane: active transport/symport (reabsorb Na+, Cl-; excrete K+)
How do the lumens of PCT and DCT compare?
PCT=Thicker wall, Smaller lumen
DCT= Thinner wall, Bigger lumen
Collecting tubule/ duct function?
Controlled reabsoption of water under influence of ADH
What epithelium and cell types are in collecting ducts?
Simple Cuboidal epithelium
Principal and Intercalated (dark) cells
Function of medullary collecting tubules?
Hypothalamus synthesizes ADH > release from
posterior lobe of pituitary > collecting tubules respond to increase permeability to
water > water moves out > produce concentrated urine
What is the difference in function between the two types of collecting duct cells?
Principal (light) cells: mechanosensor of fluid flow and contents
Intercalated (dark) cells: Mediate acid-base transport, water impermeable
What are the two roles of interstitial cells?
Maintenance of renal architecture and production of erythropoietin
(Produces 1,25-dihydroxycholecalciferol/ active vitamin D to increase Calcium levels during UV exposure)
How does the DCT relate to renin/ angiotensin / aldosterone?
Angiotensinogen (liver) > angiotensin I > angiotensin II
Increased K+ + angiotensin II act on adrenal cortex > increase aldosterone secretion > reabsorb Na+, Cl-, excrete K+
How does transitional epithelium change?
Contracted (fat) and Distended (slim) states of viscus
Contracted/non-distended state of viscus:
Cuboidal basal, polygonal middle, columnar upper
Transitional epithelium vesicles role?
Reserve segments of surface membrane to incorporate into surface when lumen is distended
What are the layers and lumen of the ureter?
Transitional epithelim (urothelium) >Lamina propria >Inner spiral (longitudinal) muscle >Outer spiral (circular) muscle> Outermost longitudinal layer (in lower third) >Adventitia
What is the role of the ureter?
Hollow fibromuscular tubes that deliver urine from renal pelvis to urinary bladder via peristaltic smooth muscle contraction
What is the lamina propria of the ureter made of?
Dense collagenous and elastic connective tissue
What is the adventitia of ureter made of?
Loose connective tissue with autonomic nerve plexuses, clood vessels and lymphatics
Which muscle layer in ureter is for peristaltic movements to move urine?
Outermost longitudinal layer in lower third
What is the role of the urinary bladder?
Receive and stor urine until neural stimulation cause it to contract and expel urine via urethra
What three structures surrounding the male kidney is not found in female?
L/R ductus deferens
L/R seminal vesicle
What is the lining of the bladder?
Transitional epithelium> Lamina propria > 3 layers of Detrusor muscle
What is the difference in neural control between the external detrusor muscle and the internal urethral sphincter?
External detrusor = Somatic NS
Internal urethral sphincter = Autonomic NS
Where is the trigone?
triangular area between entry of 2 ureters and exit of urethra
Compare male and female urethra location and length?
Length: Female shorter
- female: opens into vestibule anterior to vaginal opening
- male: from inferior part of urinary bladder through penis
3 sections of male urethra and epithelium?
Prostatic > Membranous > Spongy/penile
epithelium (most) >
Non-keratinized stratified squamous epithelium (tip of penis)
Is the change in epithelium in female urethra the same as in male?
Transitional > Pseudo. Col.> NKSS
How does urine movement change through the urinary system?
Through nephron: hydrostatic pressure
From renal pelvis > ureters > urinary bladder: peristalsis