Renal Block Flashcards
What is the primary role of the kidneys?
What are their specific functions?
- To maintain the volume and composition of body fluids despite wide variation in daily intake of water and solute
- Regulate water and inorganic ion balance (osmolarity)
Balance acid/base equilibrium
Eliminate metabolic waste products (i.e. urea, uric acid, creatinine)
Eliminate foreign compounds
Gluconeogenesis
Secrete hormones
Draw and label the Lobule of the kidney. Where is it located?
The lobule of the kidney is centered on the Medullary Rays
What are the functional units of the kidney called?
Nephrons
Which 2 cell types make up the collecting duct, and what are their functions?
- Principal cells - NaCl reabsorption and K+ secretion
- Intercalated cells - acid-base balance
Define Renal Lobe
A single pyramid with is overlying cortex
Define Renal Lobule
A single medullary ray with adjacent cortical labyrinth.
A functional unit that consists of collecting duct and all the nephrons that it drains
What is the function of the renal cortex?
site of glomerular filtration
What is the function of the renal medulla?
Drainage of collecting ducts into renal pelvis and ureter
Name the vessels of renal veins in order of fluid flow
Renal vein → Interlobular vein → arcuate vein → interlobular vein → stellate veins
note that the ascending vasa recta branches off from the arcuate vein as does the interlobular vein
vasa recta is located in the pyramid of the medulla
Name the vessels of renal arteries in order of fluid flow
Renal artery → interlobar artery → arcuate artery → interlobular artery → afferent arteriole → superficial glomerulus → efferent arteriole → peritubular capillary beds
note that the efferent arteriole of the juxtamedullary glomerulus becomes the descending vasa recta
vasa recta is located in the pyramid of the medulla
Name the sections of the renal tubules in order starting with Bowman’s Capsule
Bowman’s Capsule → proximal convoluted tubule → descending loop of Henle → thick ascending loop of Henle → macula densa (cells) → distal convoluted tubule → cortical collecting duct → outer medullary collecing duct → inner medullary collecting duct → papillary duct (duct of Bellini)
How is the Medullary Ray defined?
It sits right at the border between the cortex and the medulla and it encompasses only straight tubules (from the loops of Henle and the collecting tubule)
Renal Hilum
Area where blood vessels and nerves enter and exit the kidney. Concaved part of the “bean shape”
Approximately how many nephrons are there/kidney?
1 million
Which structures make up each nephron?
a “tuft of capillaries” and a renal tubule, which forms a cup shape around the capillaries
- glomerular capsule/Bowman’s capsule
What are the 2 types of nephrons and what are their primary characteristics?
-
Cortical nephron
- most nephrons are in this category (85%)
- have short loops of Henle -
Juxtamedullary nephron
- the glomeruli of these nephrons are found at the border between the cortex and medulla
- have long loops of Henle
- heavily involved in urine concentration
- make up 15% of nephrons
What are the sections of the medulla and how are they defined?
Outer Medulla
- outer stripe: thick tubular segments and outer medullary collecting ducts
- inner stripe: thick and thin tubular segments and outer medullary collecting ducts
Inner Medulla
- thin tubular segments and inner medullary collecting ducts
What makes up the Renal Corpuscle?
The glomerulus and Bowman’s Capsule
Describe the orientation of the epithelial cells that line the renal tubules
The luminal membrane of the cells faces the lumen of the tubule, while the basolateral membrane of the cells is in contact with interstitial fluid and peritubular capillaries.
There are tight junctions between these cells.
What lines Bowman’s Space?
Bowman’s space is surrounded by 2 epithelial layers
What are the 2 Fluid-filled spaces of the Renal Corpuscle, and what makes up the fluid that fills each of them?
Describe the function of the space if specific
Vascular Space
- structure: glomerular capillaries
- fluid: plasma, RBCs, WBCs, proteins, electrolytes, etc
Urinary Space
- structure: Bowman’s space (lined by 2 epithelial layers)
- fluid: ultrafiltrate plasma
- function: this is the first step in urine formation
Name the cells that make up the vascular pole of a Renal Corpuscle and state where they are located (in relation to other structures)
Macula densa cells are found near the distal convoluted tubule
Smooth muscle cells line the afferent and efferent arterioles
Juxtaglomerular cells
Extraglomerular mesangial cells
Mesangial cells
Foot processes (pedicels) of podocytes
Name the cells that make up the urinary pole of a Renal Corpuscle and state where they are located (in relation to other structures)
Podocyte (visceral layer)
Parietal layer (Bowman’s Capsule)
Name the functions of Mesangial Cells
- Provide mechanical support
- Control GBM material turnover
- Regulate blood flow
- Secrete vasoactive substances
- Respond to angiotensin II
Describe the structure of a podocyte
The podocyte is part of the visceral layer. It is comprised of a cell body, primary process, secondary process, and pedicels (branch from secondary processes). It is lined internally by the basal lamina and a layer of endothelial cells of the glomerulus. Between podocyte processes are filtration slits.
What is the function of a podocyte?
The final passage of fluid from the glomerular capillary to Bowman’s space occurs through the filtration slits between the pedicels of the podocyte.
Podocytes surround glomerular capillaries and provide structural support
Foot Processes surround the basement membrane and are responsible for podocyte termination
Filtration Slits are clefts between foot processes where filtrate enters Bowman’s space
Name the structure that comprise the Glomerular Filtration Barrier (excluding cells, proteins, and large molecules)
Vascular Space - glomerular capillary endothelium
Shared Space - basement membrane (filtration membrane)
Tubular Space - Podocytes and Bowman’s Capsule
- Podocytes are epithelial cells, which all other cells are endothelial
What role do glomerular capillaries play in filtration?
They are fenestrated to allow for the passage of solute-rich fluid. Proteins are typically excluded from passage due to their size, which results in a filtrate that is low in protein.
What are the primary proteins that comprise the filtration slit between podocytes?
Podocin
Nephrin
NEPH-1
What is the pathophysiological result of mutations in proteins comprising the filtration slit?
Proteinuria and Nephrotic Syndrome
What are some broad characteristics of the renal vasculature?
All blood that flows through the kidneys flows through glomeruli.
All glomeruli are located in the cortex
There are 2 types of capillary beds that exist in series
- glomerular capillaries (afferent and efferent arterioles)
- postglomerular capillaries (peritubular capillaries and vasa recta)
What forces are responsible for the movement of fluid and solute from the capillaries to Bowman’s Capsule?
Fluid moves by bulk flow due to high hydroststic pressure caused by the afferent and efferent arterioles, which only feed and drain a relative small volume of capillaries
What happens to most of the filtrate that moves into Bowman’s Capsule?
It is reabsorbed by renal tubules and returned to the blood through peritubular and vasa recta capillaries
What is the function of the primary cilia found in proximal tubules of the kidneys?
Mechanosensor - sense changes in flow rate of tubule fluid
Chemosensors - sense/respond to compounds in surrounding fluid
They initiate calcium-dependent signalling pathways involved in kidney cell function, proliferation, differentiation, and apoptosis
What structures make up the juxtaglomerular apparatus?
The macula densa cells at the top of the thick ascending limb of the loop of Henle come into close proximity with the afferent arteriole of the same nephron
Cells that make up the apparatus:
- macula densa cells (of thick ascending limb of loop of Henle)
- juxtaglomerular cells (of afferent arteriole)
- extraglomerular mesangial cells
What is the primary secretion of the juxtaglomerular apparatus?
Renin, which is an endocrine signal
What are the structural characteristics and functions of the Juxtaglomerular cells (granular cells) in the afferent arteriole?
Mechanoreceptors - stretch receptors sense stretch in the afferent arteriole, innervated by the sympathetic nervous system
Renin is stored in secretory granules held in enlarged smooth muscle cells
Cells are part of the Renin-angiotensin system (RAS), which raises blood pressure
What are the structural characteristics and functions of the Macula Densa cells of the TAL?
Tall, closely packed, tubular epithelial cells that are adjacent to granular JG cells
Chemoreceptors respond to changes in NaCl content of filtrate
Cells are critical regulators of Blood Pressure. They work in tandem
What are the structural characteristics and functions of the Glomerular Mesangial Cells?
They are smooth muscle-like cells
They help regulate blood flow in the glomerulus by contraction
They engulf macromolecules that get hung up during filtration
What is the primary function of the loops of Henle?
They are responsible for establishing the interstitial osmotic gradient
They are a countercurrent multiplier
What is the function of renal circulation?
It is responsible for:
- Returning reabsorbed solutes to circulation and maintaining hyperosmotic interstitial medulla
- Concentrating Urine - countercurrent exchange system
What is the primary function of the juxtaglomerular apparatus?
Regulating blood pressure
Define tonicity and describe the outcomes for cells that are hypertonic and hypotonic
Tonicity - ability of solute to cross cell membrane (relative concentration of solute on each side of membrane). Refers to the solution surrounding the cell.
Hypertonic causes cell to shrink
Hypotonic causes cell to swell
Define osmole
The amount of substance that dissociates in solution to form 1 mole of osmotically active particles
i.e. 1 mole of NaCl = 2 osmoles of solute
Define osmolality
osmoles/kg H2O
- completely dependent on the # of molecules in the solution
- Normal value for body fluids: 290 mOsmoles/kg solution
Define osmolarity
osmoles/L solution
*In dilute solutions, the osmolality ~ osmolarity
What is the normal range and concentration in plasma/cell of Na+?
(in mmol/L)
Normal Plasma Range - 135-145
Plasma Concentration - 142
Cell - 15
What is the normal range and concentration in plasma/cell of K+?
(in mmol/L)
Normal Plasma Range - 3.5-5.0
Plasma Concentration - 4.4
Cell - 140
What is the normal range and concentration in plasma/cell of Ca2+?
(in mmol/L)
Normal Plasma Range - 1.14-1.3
Plasma Concentration - 1.2
Cell - 100 nM
What is the normal range and concentration in plasma/cell of H+?
(in pH)
Normal Plasma Range - 7.38-7.42
Plasma pH - 7.4
Cell - ~7.2
What is the normal range and concentration in plasma/cell of Cl-?
(in mmol/L)
Normal Plasma Range - 100-108
Plasma Concentration - 102
Cell - 10
What is the normal range and concentration in plasma/cell of HCO3-?
(in mmol/L)
Normal Plasma Range - 22-28
Plasma Concentration - 24
Cell - 10
What is the normal range and concentration in plasma/cell of Protein?
(in g/dl)
Plasma Concentration - 7
Cell - 40
What is the normal range and concentration in plasma/cell of Glucose?
(in mg/dl)
Normal Plasma Range - 70-110
Plasma Concentration - 100
What is the normal range for and plasma/cell osmolality?
(in mosmol/kg H2O)
Normal Plasma Range - 285-295
Plasma Concentration - 290
Cell - 290
What is the most abundant substance in the body?
Water
What types of fluid make up extracellular fluid?
Interstitial fluid, intravascular compartment fluid, lymph, and transcellular fluid
What volume of fluid is contained in the 3 primary fluid compartments?
What is the total body water (TBW)?
Interstitial Fluid - 11 L
Intracellular Fluid - 28 L
Plasma - 3 L
Total Body Water - 42 L