Lecture 28: Kidneys Flashcards
Where are kidneys in body cavity?
Primarily retro-peritoneal
What sits on top of the kidney? Are they connected?
The adrenal glands, which are not connected physically. But have a functional connection, i terms of the hormones they release that mediate sodium uptake.
Kidney blood supply
The branch of the aorta, the renal arteries. They lie posterior to the renal vein, which drains the venous blood of the kidneys. The renal veins drains into the IVC.
Length of renal veins
L. renal vein 2x longer than R. renal vein. THis means the l. testicular vein drains directly into the l. renal vein
Where is the ureter
Drains inferiorly from that kidney
Parts of the kidney
cortex, medulla, papilla, calyces
Renal column
Extension of renal cortex, which separates two renal pyramids (sections of renal medulla).
Renal papilla
The tip of the renal medulla, opening into one of the nine minor calyxes, which opens into one of two major calyxes. The major calyx opens into the renal pelvis which drains into the ureter.
purpose of kidney
filter blood and produce urine. 180 liters of fluid is filtered daily, 1-2 liters of urine is produced.
Urine formation
involve filtration, secretion and reabsorption of fluid by the renal corpuscles and tubules.
Separate functions of kidneys
Remove metabolic waste, foreign substance and drugs.
Regulate volume and composition of water and electrolytes in the extracellular fluid
control acid base balance
renin and erythropoietin creation: endocrine function
convert vitamin d into active form
gluconeogenisis –> make glucose from amino acids during starvation
what is the nephron
the functional unit of the kidney, 1 million in each kidney.
Components are the corposcule and the renal tubule
Parts of the renal tubule
The proximal convoluted tubule (PCT), the loop of henle, the distal convoluted tubule.
Parts of the corposcule
the bowman capsule, the glomerulus
parts of the bowman capsule
parietal layer, visceral layer (podocytes), the bowmans (urinary) space.
glomerulus
Many capillaries in a ball, supported by mesangium (mesangial cells, ECM)
Loop of Henle
Thick descending limb (PCT), thin limb (the bottom loop), thick ascending limb (distal convoluted tubule)
Does the nephron contain the collecting duct?
No. It has a different embryological primordial.
podocytes structure
Modified epithelial cells of the visceral layer of bowman’s capsule. Sit on top of the capillaries of the glomerulus on their surface . Have primary foot process that branch into secondary foot processes that extend over entire glomerular basement membrane, creating covering network. These feet are divided by narrow slits called filtration slits.
efferent arteriole vs. afferent arteriole
The afferent arteriole enters the glomerulus, the efferent arteriole exits the glomerulus.
What sits between the efferent and afferent arterioles
The distal tubule.
Schema of renal circulation
Renal artery –> afferent arterioles–>capillaries –> efferent arterioles–> capillaries surrounding tubule OR vasa recta wrapping around the loop of Henle in the medulla –> Renal vein.
Glomerular basement membrane
Sits directly on top of the capillaries of the glomerulus. The secondary foot processes sits directly on the glomerular basement membrane.
Podocytes contents/function
cytoplasm contains actin filaments, lysosomes, microtubules, and have contractile and phagocytic properties.
They are partially responsible for creating the glomerular basement membrane.
Three components of the filtration barrier
The filtration barrier sits between the bowmans capsule and the glomerulus. Made up of:
fenestra between capillaries –> basement lamina –> filtration slits between podocyte feet
What can go through the filtration barrier
Hemoglobin, 65000 mw and smaller molecules- pass thru; Albumin, 68000 mw and larger molecules are retained.
Some proteins can go through. Ions can go through. Vitamins can go through. What else?
Mesangium
CT that sits between the capillaries of the glomerulus. Mesangial cells and mesangial matrix. Provides mechanical support.
functions of the mesangium
matrix production, which supports the glomerular cap.
Contractile, which can impact the rate of filtration
phagocytic of immune complexes that do not go through filtration and escape near mesangium.
Are proliferative in cases of glomerular disease
Can produce vasoactive substances that can induce constriction of afferent and efferent arterioles (endothelins)
Distal convoluted tubule cells
simple cuboidal
PCT cells
microvilli simple cuboidal, called the brush border
loop of henle cells
Squamous
collecting tubule cells
simple cuboidal
PCT vs. DCT AZO dye
will label the brush border blue in the PCT.
lysosomes –> red
PCT qualities
Microvilli, endocytic vesicles, lysosomes, mitochondria, lateral plasma membrane interdigitation (infoldings of basal lateral PM containing mitochondria –> typical of of ion transporting epithelia), basal PM infoldings
lateral plasma membrane interdigitation
infoldings of basal PM containing mitochondria –> typical of of ion transporting epithelia
This leads to indistinc cell borders. These infoldings contain mitochondria with sodium pump localized in the membranes. It is active transport, need mitochondria. Amino acids and glucose are also transported out of the cell.
why does PCT have apical surface microvilli?
asorptin of 80% of ultrafiltrate
microvilli membranes on PCT purpose?
transport proteins for transporting sodium, amino acids and glucose into the cell
endocytic vesicles and lysosomes purpose?
breakdown absorbed proteins
mitochondria PCT purpose
energy for active transport
DCT qualites
sparse microvilli, nuclei featured on the top of the cell, basal PM infoldings but no lateral interdigitation, mitochondria
Aldosterone
mediates the active transport of sodium from the tubular fluid of DCT into renal interstitium
basal plasma membrane infoldings of DCT why?
Na+-K+ ATPase pump for active transport of Na+ from the tubular fluid into the renal interstitium
Collecting duct cells
pale staining cells, cuboidal to columnar, lack brush border, distinct cell borders (no interdigitation)
Function of collecting duct
reabsorption of water from the ducts, is controlled bi antidiuretic hormone (ADH; vasopressin) from the posterior pituitary glands
Justaglomerular (JG) apparatus;
Involved in the regulation of systemic blood pressure via the renin-angiotensin aldosterone system)
Parts of JG apparatus
Macula densa of the DCT, JG cells ( renin-producing, protease), extraglomerular mesangial cells (lacis cells)
Where is the macula densa
The point of the DCT that passes between the afferent and efferent arterioles. Only the half side that is in contact with the JG cells of the afferent/efferent arterioles. Called so because they are larger/denser than the other cells of the DCT. The cells are very crowded together.
Where are the JG cells
The cells of the afferent (mostly)/efferent(few) arterioles that are in contact with the macula densa. Modified smooth muscle cells of the arterioles.
Urinary passage
Minor calyces –> major calycess –> renal pelvis –> ureter –> urinary bladder –> proximal urethra
Types of cells in excretory passages
Transitional epithelium/uroepithelium; lamina propria –> collagenous tissue –> smooth muscle (2 or 3 layers) –> adventitia or serosa (blood vessels, lymphatics or nerves) what is serosa/adventita? is this list from inside to outside?
Placques of transitional epithelium
Thickened plasma membranes, coverings of pillowing cells on top.
Urinary bladder characteristics and functions
Conduit of urine
Impervious to water
Resistant to bacteria
Stretch to cover varying size of bladder
Significance of plaques unknown possibly contribute to membrane strength and impermeability
