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| What is the function of the structure to which the red arrow is pointing?[image] |
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Reabsorption/transport of proteins (pinocytosis)
(Dr. Mallet said that endocytosis is the process used by the proximal convoluted tubule to reabsorb proteins; Dr. Cammarata used "pinocytosis) |
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In which structure is this tissue found?
What are its notable characteristics?
[image] |
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Distal convoluted tubule
- simple cuboidal epithelium
- no brush border
- laminal borders not well-defined |
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What is the name of the main structure in the image below?
From where in the nephron is this tissue found?
What are the other cell types that you see?[image] |
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Collecting tubules
This is found deeper in the medulla - cells begin to look like proper collecting tubules (characteristic nuclei, defined lateral border)
You also see vasa recta, thin limbs |
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| To what cells are each of the pairs of arrows pointing?[image] |
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Thin limb of Henle (on the left)
Vasa recta (note red cells) |
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MD – macula densa
RC – renal corpuscle
PT - proximal tubule
DT – distal tubule
CT – collecting tubule
[image]
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What does the GLOMERULUS consist of?
Bowman's capsule?
What is Bowman's capsule's external layer?
Its internal layer?
Urinary space?
Vascular pole?
Urinary pole?
Where are filtration slits located?
What forms the basal lamina, and what does it enclose?
What is the basal lamina divided into? |
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capillary bed, fenestrated endothelial cells with no diaphragms, and mesangial cells
Bowman's capsule is a double-walled epithelial layer that encloses the glomerulus
its external layer is the parietal layer of simple squamous epithelium
its internal layer is the visceral layer of podocytes, with primary processes and secondary processes (called pedicles) which attach to the capillaries of the glomerulus
The urinary space is found b/ the parietal and visceral layers
The vascular pole is the site of the entering afferent arteriole and the exiting efferent arteriole
The urinary pole is the site of the origin of the proximal convoluted tubule
Filtration slits are located b/t adjacent pedicles of podocytes along the basal lamina
The basal lamina is formed by podocytes and endothelial cells. The basal lamina encloses the capillaries of glomeruli and intraglomerular mesangial cells
Lamina densa = physical filter
Lamina rara = charge barrier |
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What features characterize the proximal convoluted tubule?
What is the function of its epithelium? |
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PCT are within the CORTEX
They are lined by a simple cuboidal or columnar epithelium with a brush border
The epithelium absorbs macromolecules via pinocytosis and transports Na+
The epithelium has lots of mitochondria |
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| What comprises the loop of Henle? |
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Descending limb (a continuation of the PCT)
Ascending limb (continues as the DCT)
The descending limb reabsorbs filtered water
The ascending limb reabsorbs filtered NaCl, K+, and Ca++
Each limb has a thick and thin segment
- thick segments are lined by simple cuboidal epithelium
- thin segments are lined by simple squamous epithelium |
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| Where is the macula densa located? What does it do? |
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It's a modified portion of the DCT that lies adjacent to the vascular pole of the renal corpuscle
Cells of the MD monitor Na+ within the tubular fluid: when they sense a slower rate of Na+ delivery (and therefore d/c blood volume/BP), they send a signal through the juxtaglomerular mesangium, which send a signal to specialized smooth muscle cells of the afferent arteriole to constrict, thereby lowering BP |
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The "drainage system" of the nephron
What is the role of ADH? |
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DCT continues as collecting tubules lined by a simple cuboidal epithelium
CT drain into collecting ducts --> papillary ducts (a.k.a. ducts of Bellini), lined by a simple columnar epithelium
Urine drains from papillary ducts --> minor calyces --> major calyces --> renal pelvis (lined by transitional epithelium)
ADH (a.k.a. vasopressin) concentrates the urine (hypertonic) by affecting increased permeability of water and urea by collecting tubules |
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Juxtaglomerular apparatus
- Juxtaglomerular cells (JGC)
- Extraglomerular Mesangial Cells (EGM) |
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JGC are modified smooth m cells of afferent arterioles
they secrete renin under stimulation by sympathetic nerve fibers
EGM are called lacis or polkissen cells |
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Regulation of blood pressure
- renin
- Angiotensin II
- Aldosterone |
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Renin converts angiotensinogen -> AT-I
ACE converts AT-I -> AT-II
AT-II increases BP by constricting arterioles and stimulating aldosterone secretion from the adrenal glands
Aldosterone acts on cells of renal tubules to i/c absorption of Na+ and Cl- --> i/c BV --> i/c BP |
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Peritubular capillaries
From what source does blood drain into them?
What is their function? |
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Fed by efferent arterioles of cortical nephrons, which supply proximal and distal tubules
They carry away absorbed ions and low-molecular-weight proteins |
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Vasa recta
From what source do they receive blood?
Where are they found?
What do the supply? |
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capillaries fed by efferent arterioles of juxtamedullary nephrons, found parallel to long loops of Henle in the medulla
The vasa recta supply the medulla |
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Ureter
Where does it extend?
Epithelium?
Effect of contraction? |
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Extends from the renal pelvis to the urinary bladder
Lumen is lined with *transitional epithelium,* its lamina propria contains smooth muscle arranged in bundles
Smooth muscle contraction affects peristalsis, which forces urine toward the bladder |
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| A pathologist is examining renal tissue, and notices a tubular structure that has a brush border. Which structure is she examining? |
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PROXIMAL CONVOLUTED TUBULE
PCTs are lined by a simple cuboidal epithelium. These cells extend microvilli into the lumen, which creates a brush border |
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Which cells within the glomerulus form the filtration slits?
What layer in Bowman's capsule do these cells form? |
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PODOCYTES
Filtration slits along the basal lamina of the glomerulus are formed by pedicles of podocytes. These cells form the visceral (internal) layer of the Bowman's capsule. |
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| Which artery/arteriole provides blood most directly to the glomerulus? |
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AFFERENT ARTERIOLE
Blood to the glomerulus is supplied by the afferent arteriole, which branches from an interlobular artery. The efferent arteriole exits the glomerulus at the vascular pole. |
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| Urine passes from the Bowman's (urinary) space into which structure? |
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PROXIMAL CONVOLUTED TUBULE
Ultrafiltrate of blood plasma first passes through filtration slits into the Bowman's space and then into the proximal convoluted tubule |
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| What is the function of the cells of the macula densa? |
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MONITORS NA+ OF RENAL TUBULE FLUID
The macula densa monitors the level of sodium ions in the filtrate that passes within the distal convoluted tubule |
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| A renal lobule consists of: |
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COLLECTING DUCTS AND NEPHRONS
A renal lobule consists of nephrons and the collecting ducts that drain them |
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| Within the kidney, what structure(s) does the basal lamina surround? |
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GLOMERULAR CAPILLARIES AND INTRAGLOMERULAR MESANGIAL CELLS
The basal lamina serves as a barrier b/t the blood within the capillaries and Bowman's space |
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| Reduced water absorption within the kidney would be associated with a defect in which structures? |
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| PROXIMAL CONVOLUTED TUBULES |
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| Blood pressure increases in response to angiotensin II by what mechanism? |
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| CAUSING CONSTRICTION OF ARTERIOLES |
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| You have been provided an antibody to renin. You want to identify and determine the distribution of those cells within the kidney that express this protein by immunocytochemistry. Which cells would you have identified? |
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CELLS OF AFFERENT ARTERIOLES
Renin is sythesized by specialized cells of the tunica media of afferent arterioles |
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For each of the following features, name which calyx it characterizes (kidney, ureter, or urinary bladder); more than one is possible:
A. Respond to aldosterone
B. allow water to pass from the luminal contents
C. contain mucous glands in submucosa
D. lined by transitional epithelium
E. surrounded by a layer of skeletal muscle |
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A. aldosterone acts on the cells of RENAL tubules (increases absorption of Na and Cl)
B. the descending loop of Henle of the proximal tubule reabsorbs filtered water
C. none secrete mucous
D. all three are lined by transitional epithelium
E. renal tubules are surrounded by epithelium only; the ureter and bladder are surrounded by smooth muscle |
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renal artery – supplies blood to kidney
interlobar arteries – between renal pyramids
arcuate arteries – at junction of cortex amd medulla interlobular arteries – traverse cortex radially between lobules
afferent arteriole – come off at right angles to interlobular arteries and supply blood to capillaries of glomerulus
efferent arteriole – leaves glomerulus
[image] |
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| blood supply cont. (after efferent arterioles) |
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peritubular capillaries – fed by efferent arterioles of cortical nephrons
nourish proximal and distal tubules
Vasa recta – capillaries fed by efferent arterioles of juxtamedullary nephrons parallel to long loops of Henle
nourishes medulla |
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Epithelium! What is it for each of the following:
Bowman's capsule
Proximal convoluted tubule
Thick descending limb of Henle's loop
Both thin limbs of Henle's loop
Thick ascending limb of Henle's loop
Distal convoluted tubule
Collecting tubules
Collecting ducts (ducts of Bellini) |
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Parietal (external) layer: simple squamous
PCT: simple cuboidal or columnar with brush border
Thick ascending: similar to PCT
thin limbs: simple squamous epithelium
thick ascending: similar to DCT
DCT: simple cuboidal, NO brush border
CT: simple cuboidal
DoB: simple columnar
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