Urinary System Flashcards
What are the four components of the urinary system?
- Kidneys
- Ureters
- Urinary bladder
- Urethra
What are the four functions of the urinary system?
- Filtration
- Active absorption
- Passive absorption
- Secretion
Kidneys receive _____% of total blood flow
20-25%
Talk me through the process of the urinary system very generally
Blood arrives at kidneys > filter to make ultrafiltrate > passive and active absorption > reabsorb the essential fluids and electrolytes to return to the body + metabolic waste is removed
What stimulates the release of erythropoietin by the kidneys? What does it do?
Low blood oxygen levels > kidneys release erythropoietin > stimulates the production of RBC in the bone marrow
What stimulates the release of renin by the kidneys? What does it do - overall effect?
Low sodium levels or low blood volume > release of renin > increase in blood pressure
What are the two layers to the capsule of the kidney?
- Outer fibrous layer
2. Inner layer of myofibroblasts
What is a unique feature of the inner layer of the capsule of the kidney?
It has a contractile function which allows it to withstand pressure changes
What is the hilum of the kidney?
The hilum is a concave region that serves as the entry point for the renal artery, exit point for renal vein, and ____
What is the renal pelvis?
Funnel-shaped opening at the beginning of the urter
What are the two parts of the renal pelvis?
- Major Calyx
2. Minor Calyx
How many medullary pyramides does each person have?
10-18
What are medullary rays?
Extensions of medullary pyramids into the cortical region
The space between the medullary rays is the cortical labyrinths
What is the cortical labyrinth? What does it house?
The outer cortex region between medullary rays
Houses the renal corpuscles + convoluted tubules + collecting tubules
Why does the outer cortex stain dark red?
95% of the vasculature present in the kidney is housed in the outer cortex
Talk me through the vasculature of the kidneys starting at the hilum
Renal artery enters at hilum > divides into interlobar arteris > runs along medula region next to the pyramid > takes a sharp turn at cortical-medullaruy junction > acruate cessels (AA and AV) > sharp turn and enter cortext > interlobular vessels > glomerular capillaries > portal arteriole system > efferent arteriole > secondary capillary system
What does the portal arteriole system do?
The afferent arteriole provides blood to the glomerular capillaries and delivers blood to efferent arteriole
What does the secondary capillary system in the kidneys do?
Provides nourishment for the kidney itself
What demarcates the boundary between the cortex and the medulla?
Arcuate vessels
What kind of staining does the medulla have?
Stains lightly
What is the renal corpuscle?
Houses the glomerular capillaries and associated tubules
What specific tubules do the medullary rays consist of?
Straight tubules
Cortical collecting tube
What is the vasa recta?
Unique capillary system that runs parallel to the collecting duct it the medulla
What is the papilla?
The point where the medullary pyramid comes to an apex
What kind of tissue is the papilla made of?
Simple columnar epithelium
What tissue type if the minor calyx made of?
Transitional eptithelium
Talk me through urine movement
renal corpuslce > PCT > loop of Henle > DCT> collecting duct > papilla > minor calyx > major calyx > renal pelvis > ureter > baldder > urethra
Where it the medullary pyramid the widest?
At the cortical region
What is the function of transitional epithelium?
Allows for distension of structures such as the ureters, bladder, and urethra
What constitutes a kidney lobe?
Medullary pyramid + associated cortical tissue
Lobes are subdivided into ______
Lobules
What constitutes a kidney lobule?
Central medullary ray + surrounding cortical material
What is a renal secretory unit?
Kidney lobule
Medullary rays + Cortical labyrinth
When are the lobes of the kidney most apparent?
In a fetus - there is evident CT invagination
The CT disappears soon after birth
What is the functional unit of the kidney?
Nephron
What is Bowman’s capsule?
Incases the renal corpuslce
What are the two layers of Bowman’s capsule?
- Visceral layer
2. Parietal layer
What is the tissue type of the visceral layer of Bowman’s capsule?
Podocytes?
What is the tissue type of the parietal layer of Bowman’s capsule?
Simple Squamous Epithelium
What is the function of the PCT? (2)
- Majority of reabsorption
2. Turn the ultrafiltrate into tubular fluid
In the PCT ___% of glucose and amino acids and _______ of salt and water are reabsorbed
100%
A lot
What is the function of the nephron loop/loop of Henle? (2)
- Concentration of urine
2. water and salt reabsorption to interstitial fluid
What are the 4 components of the loop of Henle / nephron loop?
- Descending thick segment / proximal straight tubule
- Descending thin limb
- Accending thin limb
- Accending thick segment / distal stright tubule
What are the main functions of the DCT? (2)
- Secretion
2. Absorption
What is the function of macula densa cells? Where are they found? What type of cell are they?
Specialed cells that sense sodium concentration and blood volume and tell the juxtaglomerular cells
Located in DCT
Tall columnar cells that are thin
What is the function of the capillary system? What does it include
final adjustments
Cortical collecting duct
What tissue type lines the corical collecting duct? What does this indicate about its function?
Moves from squamous > cuboidal > progressively become taller and taller
Indicative of secretion and absoption
What are the four components of the renal corpuscle?
- Glomerulus
- Bowman’s Capsule
- Vascular pole
- Urinary pole
What is the function of podocytes?
Reinforce the junctions of the flomerulus
What tissue type makes up the glomerular capillaries?
Simple squanmous epithelium
What is Bowman’s space / Urinary space?
White space between visceral and parietal layer
Contains the filtrate
What is the vascular pole?
Where the afferent arteriole delivers blood into capillaries and the efferent arteriole exits after it goes through the glomerular capillaries
What is the vascular in close proximity to?
The macula densa cells in the DCT
What is the urinary pole?
Where the parietal layer of Bowman’s capsule transitions to the PCT
The exit point for urine to enter the PCT
What are the four parts of the glomerular filtration barrier?
- Podocytes
- Filtration slits bridged by slit diaphragms
- Fenestrated capillaries
- Glomerular basement membrane
What is the function of the glomerular filtration barrier?
It allows for the filtration of blood in order to create the ultrafiltrate
In what order does the blood travel through the different parts of the glomerular filtration barrier?
Blood > endothelial cells > fused basement membanre (podocytes + endothelial cells) > filtration slits
On the other side of the filtration slits its known as the ultrafiltrate
What are the 3 parts of the glomerular basement membrane?
- Lamina rara externa
- Lamina densa
- Laimina rara interna
What is the function of the glomerular basement membrane? What aspects of the membrane help it do this? (2)
- Size exclusion; type IV collagen fibers in the lamina densa and filtration slits
- Charge exclusion; GAGs repel negatively charged ions
What are pedicels?
Podocytes have primary processes called trabeculae, which wrap around the glomerular capillaries. The trabeculae in turn have secondary processes called pedicels.
Pedicels interdigitate, thereby giving rise to _____?
Filtration slits
Glomerular capillaries are enriched with what to allow for the rapid movement of water?
AQ1 (aquaporin 1)
What is included in the juxtaglomerular apparatus (3)?
- Macula densa
- Juxtaglomerular cells
- Mesangial cells
What are juxtaglomerular cells?
Smooth muscle cells in the afferent and efferent arterioles
What do juxtaglomerular cells release?
They release renin in response to low sodium / low blood volume in order to increase blood pressure
What are mesangial cells? Where are they found?
Act as the macrophages of the kidneys - phagocytose large molecules and foreign invaders. Can also release cytokines and other chemical signals.
Surround glomerular capillary tufts (tuft = network of capillaries)
What is the renin-angiotensin-aldosteron system (RAAS)?
Low sodium / low blood volume > sensed by macula adherens > tell juxtaglomerular cells > release renin > cleaves angioteninogen > angiotensisn I > cleaved by angiotensin converting enzyme (ACE) > angiotensin II > increases blood pressure by
- Vasocontriction
- Adrenal cortex > release aldosteron > acts on tubles > increased sodium reabsorption and water retention
- Hypothalamus > produce and release antidi
Where is angiotensin made? Does it circulate in an active or inactive state?
Made in the liver, then circulates through plasma in an inactive state
What is an ID difference between the PCT and DCT?
The PCT has a brush border which makes it have a fuzzy appearance
The DCT has a clear lumen
What modifications does the PCT have on its apical (2), lateral (1), and basal (2) domains?
Apical - brush border, zonula occludens
Lateral - Plicae
Basal - interdigitated basal processes, basal striations
Because PCT have plicae on the lateral domain - what does this mean for ID?
You can’t distinguish cells laterally - the lateral domain is not evident on a micrograph
Do the PCT, DCT, or collecting ducts have obvious lateral domains?
Collecting ducts
What is the function of the Loop of Henle?
Responsible for the establishment of an osmotic gradient in the medulla
What are the two types of nephrons?
- Cortical Nephrons
2. Juxtamedullary Nephrons
Which parts of the loop of Henle are cortical nephrons? (3)
Corpuscle - outer cortex
Short Loop
Bend - outer medulla
What is the function of Juxtamedullary nephrons?
Responsible for urine concentration due to increased concentration gradient
What parts of the loop of Henle are juxtamedullary nephrons?
Corpuscle - inner cortex
Long, thin Loop
Bend - inner medulla
Cortical nephrons comprise ___% of the Loop of Henle, while Juxtamedullary comprise ____%
80, 20
In the descending loop of Henle what is moving in and out? What is not moving? Is it active or passive transport?
Descending loop is water permeable
Na is not moving
Passive transport - osmosis
In the ascending loop of Henle what is moving in and out? What is not moving?
NaCl is moving
Water is not moving
In the ascending loop of Henle, where is active transport happening? Passive?
Active transport on the thick branch
Passive transport in the thin branch
In the decending loop of Henle the fluid goes from _______ to _________
Isomotic to hyperosmotic filtrate
In the acending loop of Henle the fluid goes from _______ to __________
Hyperosmotic to hypoosmotic filtrate
What are the three functions of the DCT?
- Reabsorption of sodium and bicarbonate ion
- Secretion of K, H, and ammonium
- Responds to aldosterone
What tissue type is the DCT made of?
Simple cuboidal epithelium
Which has larger cell size: PCT or DCT?
PCT has larger cells
How does the DCT respond to aldosterone?
Aldosterone > increase Na and fluid retention > increase blood pressure
Which is longer, more torteourus, and more abundant - PCT or DCT?
PCT
What tissue type makes up the collecting tubule and cortical collecting ducts?
Squamous to cuboidal
What tissue type is the medullary collecting ducts?
Cuboidal that transition to columnar
How are collecting tubules and collecting duct ID?
Clear cell boundaries
Are the collecting tubules and collecting ducts considered part of the nephron?
No
The collecting tubules and collecting ducts are ______ water permeable
Selectively
What two specialized cell types does the medullary collecting duct have?
- Principal (light) cells
2. Intercalated (dark) cells
What are principal cells? What apical modifications do they have? For what purposes? (2)
Cells in the medullary collecting duct
1. Primary cilia = mechanosensor to monitor fluid flow
2. AQP-2 = permit water movement back to the body and concentrate urine
(Also have Ca channels to increase water permeability)
AQP-2 channels are sensitive to which hormone?
ADH
What are intercalated (dark) cells? What is their function? How do they carry out their function?
Cells in the medullary collecting duct
They are sensitive to pH
If it is too acidic > secrete protons
If it is too basic > secrete bicarbonate
What is responsible for creating the Countercurrent Exchange System?
The vasa recta
Where is urine stored?
The bladder
Where is urine voided?
The urethra
What is the urine flow from the collecting ducts?
Collecting ducts > minor calyx > major calyx > renal pelvis > ureter > urinary bladder
What tissue type lines calyces, ureters, bladder, and proximal urethra?
Transitional Epithelium (Urothelium)
What is the trend seen in the layers of cells in the transitional epithelium as you move from the calyces to the bladder?
Layers increase from calyces to bladder
What is the function of urothelial plaques?
Urothelium has invaginations into the cytoplasm which allow for expansion of the apical region when distension is needed
How does the luminal surface change from a distended bladder and that of a relaxed bladder?
??
What is the function of the ureter?
Conducts urine from renal pelvis to bladder
What tissue type is the ureter composed of?
Transitional epithelium
What does the lamina propria of the ureter look like? The muscle layers? Does it have an adventitia or a serosa?
Thin lamina propria
Extensive smooth muscle
Adventitia
What are the three layers of the smooth muscle surrounding the ureter?
Inner longitudinal Middle circular Outer longitudinal (varies)
The contraction of smooth muscle gives the ureter’s lumen its characteristic ____ shape
Star
What three specific muscles are located in the bladder?
- Detrusor muscle
- Internal urethral sphincter
- External urethral sphincter
Which of the urethral sphincters is smooth muscle and involuntary movements? Skeletal and voluntary?
Internal = smooth, involuntary External = skeletal, voluntary
What is the Detrusor muscle?
The smooth muscle of the bladder
What three openings are in the bladder?
2 ureters - in the upper region
1 urethra - in the lower region
What is the function of the urethra?
Conveys urine form bladder to exterior
How does the size, structure, and function of the urethra differ between males and females?
Females; urethra is only a urinary duct, also short
Males; urethra is the urinary duct and genital system, longer
What are the 3 regions of the male urethra?
- Prostatic
- Penal - removal/avoiding of urine
- Membraneous
