Podcast
Questions and Answers
Which of the following is a primary function of the kidneys?
Which of the following is a primary function of the kidneys?
- Regulation of blood glucose levels
- Conservation of water, electrolytes, and metabolites (correct)
- Storage of fat-soluble vitamins
- Production of digestive enzymes
The kidneys only have excretory functions and do not participate in endocrine functions.
The kidneys only have excretory functions and do not participate in endocrine functions.
False (B)
What three hormones are produced by the kidney?
What three hormones are produced by the kidney?
renin, erythropoietin, active Vitamin D3
The kidneys are located in the ____________ space of the posterior aabdominal wall, at the level of the T12-L3 vertebrae.
The kidneys are located in the ____________ space of the posterior aabdominal wall, at the level of the T12-L3 vertebrae.
What best describes the renal hilum?
What best describes the renal hilum?
The renal sinus is outside the kidney, where vessels, nerves, and the renal pelvis are located.
The renal sinus is outside the kidney, where vessels, nerves, and the renal pelvis are located.
List the order of structures from anterior to posterior within the renal hilum.
List the order of structures from anterior to posterior within the renal hilum.
The renal lobe consists of the renal cortex, renal medulla, and half of the adjacent renal _________.
The renal lobe consists of the renal cortex, renal medulla, and half of the adjacent renal _________.
What is a renal lobule?
What is a renal lobule?
The inner layer of the kidney capsule (ILC) is characterized by dense connective tissue and collagen fibers.
The inner layer of the kidney capsule (ILC) is characterized by dense connective tissue and collagen fibers.
List the main components of the outer layer of the kidney capsule (OLC).
List the main components of the outer layer of the kidney capsule (OLC).
The nephron's structure that includes the glomerulus and Bowman capsule is called the renal __________.
The nephron's structure that includes the glomerulus and Bowman capsule is called the renal __________.
In the nephron, what section is located between the proximal convoluted tubule and the descending limb?
In the nephron, what section is located between the proximal convoluted tubule and the descending limb?
The macula densa is located in the proximal convoluted tubule.
The macula densa is located in the proximal convoluted tubule.
What are the components of the nephron that contribute to juxtamedullary nephrons, which form an arch?
What are the components of the nephron that contribute to juxtamedullary nephrons, which form an arch?
The medullary rays are located in the cortex and consist of straight tubules and __________.
The medullary rays are located in the cortex and consist of straight tubules and __________.
The glomerulus consists of how many capillary loops?
The glomerulus consists of how many capillary loops?
Blood enters the glomerulus via efferent arterioles and exits via afferent arterioles.
Blood enters the glomerulus via efferent arterioles and exits via afferent arterioles.
What two components make up Bowman's capsule?
What two components make up Bowman's capsule?
The modified smooth muscle cells of the afferent arteriole near the glomerulus are called _______ cells.
The modified smooth muscle cells of the afferent arteriole near the glomerulus are called _______ cells.
Which of the following is a key feature of kidney filtration? (Select all that apply)
Which of the following is a key feature of kidney filtration? (Select all that apply)
The filtration slit diaphragm is composed of the protein laminin.
The filtration slit diaphragm is composed of the protein laminin.
Name three substances included in filtrate.
Name three substances included in filtrate.
The capillary endothelial cells have large 70-90nm ________ to assist with filtration.
The capillary endothelial cells have large 70-90nm ________ to assist with filtration.
The Glomerular Basement Membrane (GBM) that assists with filtration is composed of what type of collagen?
The Glomerular Basement Membrane (GBM) that assists with filtration is composed of what type of collagen?
Mesangial cells in the glomerulus primarily function to secrete hormones that regulate blood pressure.
Mesangial cells in the glomerulus primarily function to secrete hormones that regulate blood pressure.
What are the three key functions of the nephron tubules?
What are the three key functions of the nephron tubules?
The proximal convoluted tubule has a brush border made of _________ (microvilli) on its apical surface.
The proximal convoluted tubule has a brush border made of _________ (microvilli) on its apical surface.
Which of the following molecules are reabsorbed in the proximal convoluted tubule?
Which of the following molecules are reabsorbed in the proximal convoluted tubule?
The proximal straight tubule has a more developed brush border than the proximal convoluted tubule.
The proximal straight tubule has a more developed brush border than the proximal convoluted tubule.
What is the primary characteristic of the epithelial cells in the thin descending limb of the nephron?
What is the primary characteristic of the epithelial cells in the thin descending limb of the nephron?
The thin descending limb is highly permeable to water because of the presence of __________.
The thin descending limb is highly permeable to water because of the presence of __________.
The thin ascending limb of the nephron is permeable to what molecules?
The thin ascending limb of the nephron is permeable to what molecules?
The distal straight tubule contacts the efferent arteriole to help form macula densa.
The distal straight tubule contacts the efferent arteriole to help form macula densa.
What does the macula densa portion of the distal straight tubule measure?
What does the macula densa portion of the distal straight tubule measure?
The distal convoluted tubule is relatively impermeable to water, but the reabsorption of _________ is regulated by PTH.
The distal convoluted tubule is relatively impermeable to water, but the reabsorption of _________ is regulated by PTH.
Match the cell type to its location for the cells of the Nephron.
Match the cell type to its location for the cells of the Nephron.
What is a characteristic of cells in the collecting ducts of the kidney?
What is a characteristic of cells in the collecting ducts of the kidney?
Light cells can be found in collecting tubules. They secrete K+
Light cells can be found in collecting tubules. They secrete K+
How is blood brought into, and out of, the glomeruli?
How is blood brought into, and out of, the glomeruli?
The renal hilum is located on the lateral margin of the kidney.
The renal hilum is located on the lateral margin of the kidney.
What are the three main tissue layers of the kidney capsule, from outermost to innermost?
What are the three main tissue layers of the kidney capsule, from outermost to innermost?
The functional unit of the kidney responsible for filtering blood and forming urine is the ______.
The functional unit of the kidney responsible for filtering blood and forming urine is the ______.
What type of cells are found in the proximal convoluted tubule that contribute to its absorptive function?
What type of cells are found in the proximal convoluted tubule that contribute to its absorptive function?
Match the following nephron structures with their descriptions.
Match the following nephron structures with their descriptions.
In the renal corpuscle, blood enters the glomerulus via the:
In the renal corpuscle, blood enters the glomerulus via the:
The thin descending limb of the Loop of Henle is highly permeable to sodium and urea, facilitating their reabsorption into the bloodstream.
The thin descending limb of the Loop of Henle is highly permeable to sodium and urea, facilitating their reabsorption into the bloodstream.
What specific adaptation in the bladder's transitional epithelium allows it to accommodate changes in volume?
What specific adaptation in the bladder's transitional epithelium allows it to accommodate changes in volume?
The macula densa monitors ______ concentration in the distal tubule and releases ______, ______ and ______.
The macula densa monitors ______ concentration in the distal tubule and releases ______, ______ and ______.
Flashcards
Kidney Functions
Kidney Functions
The kidneys conserve water, electrolytes, and metabolites while removing metabolic waste, maintaining acid-base balance.
Renal Hilum
Renal Hilum
Concave medial margin of the kidney; entrance to renal sinus.
Renal Sinus
Renal Sinus
Space within the kidney containing vessels, nerves, and renal pelvis.
Renal Lobe
Renal Lobe
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OLC (Outer Layer of Capsule)
OLC (Outer Layer of Capsule)
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ILC (Inner Layer of Capsule)
ILC (Inner Layer of Capsule)
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Nephron
Nephron
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Renal Corpuscle
Renal Corpuscle
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Glomerulus
Glomerulus
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Bowman's Capsule
Bowman's Capsule
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Afferent Arterioles
Afferent Arterioles
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Efferent Arterioles
Efferent Arterioles
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Podocytes
Podocytes
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GBM Function
GBM Function
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Macula Densa
Macula Densa
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Juxtaglomerular Cells
Juxtaglomerular Cells
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Mesangial Cells
Mesangial Cells
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Tubule Sequence
Tubule Sequence
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Proximal Convoluted Tubule
Proximal Convoluted Tubule
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AQP-1
AQP-1
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Thin Descending Limb
Thin Descending Limb
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Distal Convoluted Tubule
Distal Convoluted Tubule
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Collecting Tubule
Collecting Tubule
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Light cells (Principal)
Light cells (Principal)
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Dark cells (Intercalated)
Dark cells (Intercalated)
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Blood Re-entry
Blood Re-entry
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Vasa Recta
Vasa Recta
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Dome cell
Dome cell
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Ureter
Ureter
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Urethra
Urethra
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Study Notes
Kidney Functions
- Excretes metabolic waste
- Conserves water, electrolytes, and some metabolites
- Functions as an endocrine organ
- Produces renin and erythropoietin
- Converts Vitamin D3 (25-OH) precursor to active Vitamin D3 (1,25-(OH)2)
- Balances acid-base levels and plasma pH
- Affects composition and volume of extracellular fluid
- Controls arterial blood pressure
Gross Anatomy of the Kidney
- Located retroperitoneally at the level of T12-L3 vertebrae
- Renal hilum includes are concave medial margin, entrance to renal sinus (space), vessels, nerves, calices, and renal pelvis
- Veins are anterior to the arteries and renal pelvis
Kidney Organization
- Renal lobe: cortex, medulla, and half of adjacent renal column
- 8-18 renal lobes exist per kidney
- Renal columns consist of cortical tissue surrounding the medullary pyramid
- Renal lobule: 'renal secretory unit', medullary ray and surrounding cortex
Kidney Capsule Layers
- Outer layer (OLC), is dense connective tissue with:
- Collagen fibers
- Fibroblasts
- Inner layer (ILC) contains:
- Myofibroblasts
- Few collagen fibers
Nephron Components
- Renal corpuscle, including the glomerulus and Bowman's capsule
- Proximal convoluted tubule
- Proximal straight tubule
- Thin descending limb
- Ascending thin limb
- Thick ascending limb (distal straight tubule)
- Macula densa in the thick ascending limb
- Distal convoluted tubule
- Connecting tubule
- Cortical collecting duct
- Outer medullary collecting duct
- Inner medullary collecting duct
Cortex vs Medulla
- Cortex: Includes the renal corpuscle (glomerulus & Bowman’s capsule) Proximal convoluted tubule, Distal convoluted tubule
- Medulla
Medullary Rays
- Located in the cortex
- Contain straight tubules and collecting ducts
Renal Corpuscle
- Glomerulus: capillary tuft of 10-20 capillary loops (glomerular capillaries)
- Bowman's capsule: double layered epithelial cup (visceral layer, capsular space, parietal layer)
- Blood enters via Afferent arterioles and exits via Efferent arterioles
Filtration Components
- Capillary endothelial cells have fenestrations (70-90nm diameter)
- Glomerular basement membrane (GBM) is 300-370nm thick basal lamina created by capillary endothelial cells and podocytes (visceral layer of Bowman's capsule)
- Composed of collagen type IV, laminin, nidogen, entactin, heparin sulfate proteoglycans, glycoproteins
- Podocytes (visceral epithelial cells/visceral layer Bowman's capsule) have pedicels/foot processes
- Interdigitate to create filtration slits about 40nm wide
- Filtration slit diaphragm is composed of the protein nephrin
- Luminal surface of capillary endothelial cells is glycocalyx coated by plasma proteins
- Subpodocyte space is a narrow space between foot processes and podocyte cell body
Glomerular Basement Membrane (GBM)
- Physical barrier, restricting proteins > 70kDa or 3.6nm radius,like albumin & hemoglobin
- Ion-selective barrier, restricting anionic particles
Filtration Slits
- Bridged by filtration slit diaphragms, intercellular protein sheet between podocyte pedicels (foot processes).
- Nephrin is main protein, creates pores
- Other molecules that aid are (Neph1, Neph2, FAT1, FAT2, P-cadherin)
- Regulation of the actin cytoskeleton is important to control size, patency, and selectivity
Mesangial Cells
- Phagocytose and use endocytosis to eliminate trapped material
- Produce matrix to support glomerulus
- Contractile to regulate glomerular distension
Kidney Tubules
- Naming is based on: course (convoluted or straight) and location (proximal or distal) and thickness (thin or thick)
- They include the following:
- Proximal convoluted tubule
- Originates at Bowman's capsule
- Proximal straight tubule, which is the thick descending limb of loop of Henle
- Thin descending limb
- Makes hairpin turn
- Thin ascending limb
- Distal straight tubule (thick ascending limb of loop of Henle)
- Contacts afferent arteriole and forms macula densa
- Distal convoluted tubule
- Empties into collecting duct
- Proximal convoluted tubule
Proximal Convoluted tubule
- Consists of cuboidal cells with Brush border (microvilli) and AQP-1 (water channel)
Proximal Convoluted tubule Functions:
- Reabsorption of :
- Sodium via a Na+/K+-ATPase pump
- Glucose via Na+
- amino acids via amino acid transporters
- small poylpeptides via H+ peptide cotransporters
- Proteins/large peptides (endocytosis)
- Bicarbonate
- Excretion of exogenous organic acids & bases
- Converts Vitamin D3 (25-OH) to Vitamin D3 (1,25-(OH)2)
Thin Descending Limb
- Consists of epithelial cells (squamous-taller)
- Highly water permeable
- Less permeable to Na+ & urea
Thin Ascending Limb
- Consists of epithelial cells (squamous-taller)
- Highly permeable to Na+ and Cl via (Na+/K+/ Cl- cotransporters, Na+/K+-ATPase pump)
- Impermeable to H2O
- Produces uromodulin
- Influences reabsorption and the ability to concentrate urine
Distal Straight Tubule
- Consists of cuboidal cells (light eosin
Distal Convoluted Tubule
- Contains Macula densa near its end, with:
-Taller' cuboidal cells and part of the juxaglomerular apparatus
- These monitor Na+ concentration and release NO, ATP, adenosine, PGE2
- Cuboidal cells with No brush border
- Relatively impermeable to H2O
- Responsible for the reabsorption of Ca2+ (PTH-regulated)
Juxtaglomerular Apparatus Components
- Macula densa - distal tubule cells that monitor Na+ level in tubular fluid, and release NO, ATP, adenosine, and/or PGE2
- Juxtaglomerular cells consists of smooth muscle cells that produce renin (presence of secretory vesicles)
- Mesangial cells (Lacis cells)
- It is responsible for Sodium, blood volume homeostasis and Glomerular filtration rate When there are low concentrations of Sodium or reduced blood volume it activates the RAAS
Collecting Tubule
- Consists of cuboidal cells
- Light/principle cells, which secrete K+
Collecting Ducts
- Consist of squamous-cuboidal-columnar cells, which duct size increases closer to the papilla
- Contains Light cells (principal cells) and Dark cells (intercalated cells)
- The latter determine final urine osmolarity
- Responsible for reabsorb H2O, Na+, and urea
- Finally responsible for the secretion of H+ and HCO3-
Light Cells
- Most abundant cells in the collecting duct, includes a single primary cilium and are ADH responsive
Interstitial Tissue
- It is ~7% of cortex and ~20% of medulla
- Composed of fibroblast-like cells (secrete collage, glycosaminoglycans, and erythropoietin), myofibroblasts (found in medulla, not cortex), macrophages, lymphocytes and dendritic cells Collecting Tubules and Ducts
- Lead to the formation of the area cribrosa (papilla and calyx)
- These connect to a minor calyx
- Then a major calyx
- And finally the renal pelvis and superior ureter
Renal Lobules
- From the renal pyramid these connect via papilla to a minor calyx
- Followed by a major calyx and the renal pelvis and superior ureter
- 1 papilla: 1 minor calyx
- 2-3 minor calices : 1 major calyx
- 2-3 major calices : renal pelvis
Kidney Blood Flow
- Most reabsorbed material re-enters the blood
- The endothelial cells of the peritubular capillaries synthesize erythropoietin
Vasa Recta
- These consist of arterioles that turn into a hairpin to descend into the medullary pyramid
- The countercurrent exchange system passive diffusion of both salt and water between the blood and intestitium
Transitional Epithelium (Urothelium)
- Lines calyces, ureters, bladder, and urethra initial segment
Ureter
- The submucosa isn't present
- Smooth muscle layer consist of there layers:
- Longitudinal (inner)
- Circular (middle)
- Longitudinal (outer) - only seen distal end
Urinary Bladder
- Contains the detrusor muscle of muscularis
- Includes 3 indistinct layers of Smooth muscle
Male Urethra
- The Prostatic urethra is transitional epithelium
- The Membranous urethra is transitional epithelium - location of external urinary sphincter (at urogenital diaphragm)
- The Penile (spongy) urethra is: - Pseudostratified columnar epithelium until distal end - Transitions to squamous epithelium
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