Term
| describe the hilum of the kidney and what passes through it |
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Definition
hilum or hilus is on the medial side
entrance of nerves and arteries - exit of veins and lymphatics
exit of the ureter, the tube that joins the kidney to the bladder |
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Term
| describe the shape of the kidney |
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Definition
| bean-shaped organ with convex lateral surface and concave medial surface |
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Term
| describe the renal pelvis |
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Definition
expanded upper end of the ureter
divides into two or three major calyces (calyx is singular) which in turn, divide into minor calyces
kidney has clearly distinguishable cortex and medulla |
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Term
| what is found in the medulla of the kidney? |
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Definition
lighter inner region of kidney
composed of 10-18 pyramidally-shaped structures called the medullary pyramids
from the bases of the medullary pyramids, medullary rays extend into the cortex |
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Term
| describe characteristics of the cortex of the kidney |
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Definition
darker, outer region
associated with each medullary pyramid is a region of cortex which comprises a renal lobe.
The cortical tissue associated with each medullary ray forms a renal lobule |
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Term
| what are found in between medullary pyramids in the kidney? |
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Definition
| cortical tissue called columns of Bertin |
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Term
| what are nephrons, what are they made up of, and what do they form? |
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Definition
filtering units of the kidney
drain into collecting tubules which in turn drain into collecting ducts which empty into the minor calyces
made up of a renal corpuscle, a proximal convoluted tubule, a thin and thick limbs of the loop of Henle, and a distal convoluted tubule
nephron and its collecting tubule forms a uriniferous tubule, the functional unit of the kidney |
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Term
| the inner medulla of the kidney has mostly collecting ducts which drain into what? |
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Definition
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Term
| what is a renal corpuscle? |
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Definition
blood filtering component of the nephron
consists of a tuft of capillaries - the glomerulus which is surrounded by a double-walled epithelial-lined capsule called Bowman's capsule.
inner layer - visceral layer
tightly adherent to the capillary tuft
cells that form the visceral layer are very specialized epithelial cells called podocytes.
outer layer - parietal layer
simple squamous epithelium |
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Term
| what are the 2 types of poles found in a renal corpuscle? |
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Definition
vascular and urinary pole
the vascular pole has an afferent arteriole which branches to form the glomerular capillaries and an efferent arteriole which carries blood away from the glomerulus
the urinary pole is the where the proximal convoluted tubule begins |
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Term
| what cells compose the visceral layer of the bowman's capsule? |
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Definition
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Term
| where is the urinary space located in the renal corpuscle and what does it receive? |
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Definition
Between visceral and parietal layers
receives the filtrate from the glomerular capillaries |
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Term
| what structure marks the point at which the proximal convoluted tubule begins? |
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Definition
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Term
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Definition
modified epithelial cells of the visceral layer of Bowman's capsule
have interdigitating foot processes (pedicels) which cover the outer surfaces of the glomerular capillaries
filtration slits - slit-like spaces between pedicels - spanned by thin slit diaphragm |
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Term
| what are the 3 components of the filtration barrier? |
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Definition
Endothelial cells of glomerular capillaries - fenestrated capillaries with no diaphragms
Basement membrane –fused basal laminae of endothelium and podocytes
Podocyte - filtration slits and diaphragms |
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Term
| describe the glomerular basement membrane and its 3 discrete layers |
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Definition
fused basal laminae of the endothelium and the podocytes
three discrete layers
two laminae rarae on either side of a central, dense lamina densa
collagen type IV of the lamina densa acts as a physical filter
Protein size cut-off is about 69kDa, the size of albumin.
anionic heparan sulfate of the laminae rarae act as a charge barrier that prevents the passage of charged particles |
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Term
| what do mesangial cells synthesize and where are they located? |
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Definition
Synthesize extracellular matrix
Support the capillaries of the glomerulus
Phagocytic and thereby keep the filtration barrier clean
May be contractile, have receptors for vasoconstrictors such as angiotensin II |
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Term
| describe the 2 basic mechanisms of glomerular injury |
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Definition
immune - depositions of antigen-antibody complexes in the glomerular basal laminae - depending on the disease, these complexes may form in situ or be trapped complexes from the circulation as in post-streptococcal glomerulonephritis
non-immune - a number of different conditions can cause non-immune glomerular damage - one is hypertension. Hypertension can cause endothelial and epithelial damage, mesangial cell proliferation in response to the injury and basal laminar thickening |
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Term
| what is goodpasture syndrome and what organs does it involve? |
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Definition
Involves lungs and kidneys
Antibodies made to type IV collagen
Males with average age of onset 29yo
IgG binding to basement membrane type IV collagen
Normal individuals should not have bound antigens in the basement membrane |
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Term
| describe the proximal convoluted tubule and where it begins |
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Definition
begins at the urinary pole of the renal corpuscle
transition from simple squamous to simple cuboidal or columnar with a striated or brush border
longest tubule of the nephron and therefore more numerous in cross section than distal tubules
in routine H and E sections brush border, which is formed by numerous microvilli, appears irregular or disorganized and the lumen is often collapsed |
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Term
| what are some histological features of the proximal convoluted tubule? |
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Definition
Apical cytoplasm has canaliculi and pinocytotic vesicles involved in protein absorption
Basal and lateral membranes invaginated
These acidophilic cells have numerous mitochondria in basal folds indicative of ion transporting cells
Histological features
acidophilic, large cells
3-5 spherical nuclei in cross section
disorganized brush border
no visible lateral cell borders |
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Term
| what percent of sodium and water is absorbed in the proximal convoluted tubule? |
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Definition
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Term
| what percent of glucose, amino acids and small proteins are absorbed in the proximal convoluted tubule? |
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Definition
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Term
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Definition
| sugar in the urine (happens during diabetes mellitus) |
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Term
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Definition
protein found in the urine
usually occurs when the glomerular basement membranes are damaged and proteins enter the urine in large quantities |
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Term
| what is the longest tubule in the nephron? |
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Definition
| the proximal convoluted tubule |
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Term
| describe the loop of henle |
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Definition
Long u-shaped tube extending from the proximal convoluted tubule in the cortex down into medulla and then back into the cortex to empty into the distal convoluted tubule.
Acts as a countercurrent multiplier system to establish a hypertonic gradient in the medullary interstitium |
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Term
| ADH causes production of what type of urine? |
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Definition
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Term
| when is hypotonic urine produced? |
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Definition
| Hypotonic urine is produced when ADH release is inhibited as by high water intake. Diabetes insipidus is a disease in which ADH is not produced and copious amounts of hypotonic urine are produced |
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Term
| what does the loop of henle allow for? |
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Definition
| allows water to be drawn from the collecting tubules and ducts under the influence of antidiuretic hormone (ADH) from the paraventricular nucleus of the hypothalamus and released in the posterior lobe of the pituitary |
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Term
| what is the osmolarity of blood? |
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Definition
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Term
| what is the osmolarity of the interstitium deep in the medulla? |
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Definition
| 4 times that of blood (~1200 mOsm/liter) |
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Term
| what are the functions of the vasa recta in the kidney? |
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Definition
Form a countercurrent exchange system.
Passive system
As vessels descend in the medulla, lose water.
Blood osmolarity=interstitial osmolarity
As they ascend toward cortex, they gain water. |
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Term
| describe the structure and function of the distal convoluted tubule |
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Definition
Last segment of nephron
present in cortex
simple cuboidal epithelium
Basal membrane invaginations with mitochondria - ion transport
Final adjustment of ionic balance
absorb sodium and secrete potassium into filtrate (in the presence of aldosterone)
secrete hydrogen and ammonium ions to adjust pH |
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Term
| compare and contrast the distal convoluted tubule to the proximal convoluted tubule |
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Definition
| larger lumen, smaller cells (more cells in cross section) lighter staining, no brush border, lateral borders are not discernable with light microscope. Fewer sections of distal tubules as compared to proximal because they are shorter |
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Term
| what composes the juxtaglomerular apparatus and what is its function? |
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Definition
Includes the macula densa, juxtaglomerular cells, and extraglomerular mesangial cells.
JG apparatus regulates blood pressure by activating the renin-angiotensin-aldosterone system.
JG cells are specialized smooth muscle cells of afferent arteriole.
JG cells synthesize and release renin |
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Term
| where is the macula densa located? |
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Definition
Modified portion of the distal convoluted tubule.
Contacts parent renal corpuscle at vascular pole near afferent arteriole.
Cells of macula densa are columnar with tightly packed nuclei.
Monitor NaCl concentration in the tubular fluid.
Regulate glomerular filtration rate (GFR) release of renin by JG cells |
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Term
| describe the renin-angiotensin-aldosterone system in general |
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Definition
Renin, released by JG cells, converts angiotensinogen to angiotensin I.
Angiotensin I is converted to angiotensin II by angiotensin-converting enzyme (ACE) in endothelium of lung capillaries.
Angiotensin II stimulates the synthesis and release of aldosterone from the zona glomerulosa of the adrenal cortex.
Aldosterone increases the reabsorption of sodium and consequently water, by distal convoluted tubules and collecting ducts and by doing so, raises blood pressure.
Angiotensin II is a POTENT vasoconstrictor. |
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Term
| essential hypertension is a result of what? |
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Definition
overproduction of ACE
It was found that essential hypertension was associated with normal 24-hour renin and aldosterone levels.
It was found that snake venom from a South American snake inhibited angiotensin-converting enzyme in the lung.
ACE inhibitors are derivatives of the snake venom |
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Term
| where are collecting tubules and ducts located and what are their functions? |
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Definition
Urine from the distal convoluted tubule passes into collecting tubule in cortex, then into larger collecting duct in medulla
Collecting tubules are located in the medullary rays
simple cuboidal epithelium with poorly stained cytoplasm and prominent intercellular borders
Collecting (papillary) ducts in medulla
simple columnar epithelium with lightly stained cytoplasm and clearly distinguishable cell boundaries.
The collecting ducts open at the tip of the papilla into minor calyx.
Become permeable to water in response to antidiuretic hormone (ADH)
water flows into the hypertonic medullary interstitium resulting in the formation of hypertonic urine in the collecting ducts
Aldosterone causes ducts to reabsorb Na+ and thus water and thereby concentrate urine and increase BP |
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Term
| urinary passages and the bladder are lined by what type of epithelium? |
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Definition
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Term
| describe the characteristics of the urinary passages' and bladder's epithelial layers |
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Definition
Lined by transitional epithelium.
impermeable to salts and water
specialized to accomodate distensibility.
Lamina propria - dense collagenous layer with no muscularis mucosa
No submucosa
Two layers of muscle
inner - longitudinal
outer- circular |
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