what is the main function of the kidneys (general)

major excretory organ, maintain the body's internal environment

how do the kidneys maintain the body's internal environment

regulating total water volume and total solute concentration in water, regulating ion concentrations in ECF, ensuring long-term acid base balance, excreting metabolic wastes, toxins, drugs, producing erythropoietin and renin (regulate RBC production and BP respectively), activating vitamin D, and carrying out gluconeogenesis if needed

what does the urinary system include

kidneys, ureters, urinary bladder, urethra

transport urine from kidneys to urinary bladder

ureters

temporary storage reservoir for urine

urinary bladder

transports urine out of the body

urethra

location of the kidneys

retroperitoneal, in the superior lumbar region

why is the right kidney lower than the left kidney

the right kidney is crowded by the liver

where are the adrenal (suprarenal) glands

sitting atop each kidney

which part of the kidney is convex and which is concave

convex lateral surface; concave medial surface with vertical renal hilum

leads to internal space of the kidneys, renal sinus - ureters, renal blood vessels, lymphatics, and nerves enter and exit here

renal hilum

posterior view of the kidneys in relation to ribs

what are the 3 supportive tissue layers surrounding the kidneys

renal fascia (anterior and posterior), perirenal fat capsule, fibrous capsule

what are the three distinct regions of the internal kidney

renal cortex, renal medulla, renal pelvis

granular appearing superficial region

renal cortex

deep to cortex, composed of cone shaped medullary (renal) pyramids

renal medulla

what are the medullary (renal) pyramids structured like

broad base of pyramid faces cortex, papilla (tip of pyramid) points internally, renal pyramids are separated by renal columns, inward extensions of cortical tissue, lobe - medullary pyramid and its surrounding cortical tissue; about 8 lobes per kidney

funnel-shaped tube continuous with ureter

renal pelvis

what does the renal pelvis have

minor calyces, major calyces

cup shaped areas that collect urine draining from pyramid papillae

minor calyces of renal pelvis

areas that collect urine from minor calyces, empty urine into renal pelvis

major calyces of renal pelvis

urine flow goes from what to what

renal pyramid -> minor calyx -> major calyx -> renal pelvis -> ureter

label the renal cortex, renal medulla, major calyx, papilla of pyramid, renal pelvis, minor calyx, ureter, renal pyramid in renal medulla

homeostatic imbalance: infection of renal pelvis and calyces

pyelitis

homeostatic imbalance: infection or inflammation of entire kidney, severe cases can cause swelling of kidney and abscess formation, and pus may fill renal pelvis

pyelonephritis

pyelonephritis infections in females are usually caused by what

fecal bacteria entering urinary tract

how are kidneys and blood related

kidneys cleanse blood and adjust its composition, so it has a rich blood supply

what delivers about 1/4 of cardiac output to kidneys each minute

renal arteries

arterial flow:

rena -> segmental -> interlobar -> arcuate -> cortical radiate (interlobular)

venous flow:

cortical radiate -> arcuate -> interlobar -> renal veins (no segmental veins)

nerve supply

via sympathetic fibers from renal plexus

label the following: cortical radiate vein, cortical radiate artery, arcuate vein, arcuate artery, interlobar vein, interlobar artery, segmental arteries, renal vein, renal artery

structural and functional units that form urine

nephrons, more than 1 million nephrons per kidney

two main parts of the nephron

renal corpuscle, renal tubule

what are the two main parts of the renal corpuscle

glomerulus, glomerular capsule

tuft of capillaries composed of fenestrated endothelium - highly porous capillaries, allows for efficient filtrate formation

glomerulus

plasma-derived fluid that renal tubules process to form urine

filtrate

what is also called the bowmans capsule

glomerular capsule

cup shaped, hollow structure surrounding glomerulus

glomerular capsule

two layers of the glomerular capsule

parietal layer and visceral layer

which layer is simple squamous epithelium

parietal layer

which layer clings to glomerular capillaries; branding epithelial podocytes

visceral layer

extensions terminate in foot processes that cling to basement membrane, filtrate slits between foot processes allow filtrate to pass into capsular space

podocytes

3 cm long, consists of single layer of epithelial cells, but each region has its own unique histology and function

renal tubule

what are the three major parts of the renal tubule

proximal convoluted tubule, nephron loop, distal convoluted tubule

where does that distal convoluted tubule drain into

collecting duct

cuboidal cells with dense microvilli that form brush border (increases surface area, have large mitochondria), functions in reabsorption and secretion, confined to cortex

proximal convoluted tubule (PCT)

formerly called loop of henle, U shaped structure consisting of two limbs - descending and ascending

nephron loop

proximal part is continuous with proximal tubule, distal portion also called descending thin limb, simple squamous epithelium

descending limb

thick (but can be thin in some nephrons), cuboidal or columnar cells

ascending limb

cuboidal cells with very few microvilli, function more in secretion than reabsorption, confined to cortex

distal convoluted tubule (DCT)

receive filtrate from many nephrons, run through medullary pyramids, fuse together to deliver urine through papillae into minor calyces

collecting ducts

what are the two major groups of nephrons

cortical and juxtamedullary

make up 85% of nephrons, almost entirely in cortex

cortical nephrons

long nephron loops deeply invade medulla, ascending limbs have thick and thin segments, important in production of concentrated urine

juxtamedullary nephrons

renal tubules are associated with what two capillary beds

glomerulus, peritubular capillaries ... juxtamedullary nephrons are associated with vasa recta

capillaries are specialized for filtration, different from other capillary beds because they are fed and drained by arteriole

glomerulus

enters glomerulus, arises from cortical radiate arteries

afferent arteriole

leaves glomerlus, feed into either peritubular capillaries or vasa recta

efferent arteriole

why is BP high in glomerulus

afferent arterioles are larger in diameter than efferent arterioles, arterioles are high resistance vessels

around the proximal and distal convoluted tubules, water and many solutes moves from tubules into peritubular capillaries; some solutes (not water) move from peritubular caps into tubules

peritubular capillaries

long, thin walled vessels parallel to long nephron loops of juxtamedullary nephrons, function in formation of concentrated urine

vasa recta

each nephron has 1, involves modified portions of distal portion of ascending limb of nephron loop and afferent (sometimes efferent) arteriole; important in regulating rate of filtrate formation and BP

juxtalomerular complex (JGC)

what are the three things that JGC includes

macula densa, granular cells (JG cells), extraglomerular mesangial cells

cells contain chemoreceptors that sense NaCl content of filtrate

macula densa

enlarged, smooth muscle cells of arteriole, act as mechanoreceptors to sense BP in afferent arteriole

granular cells (Juxtaglomerular or JG cells)

may pass signals between macula densa and granular cells

extraglomerular mesangial cells

how many L of fluid is processed daily in the kidney

180 L

how many L of urine is formed daily

1.5 L

how many times per day do the kidneys filter the bodys entire plasma volume

60 times

at rest, what % of oxygen used by the body is consumed by the kidneys

20-25%

what is filtrate (produced by glomerular filtration) composed of

blood plasma minus proteins

what is urine

<1% of original filtrate, contains metabolic wastes and unneeded substances

what are the 3 processes involved in urine formation and adjustment of blood composition

1. glomerular filtration. 2. tubular reabsorption. 3. tubular secretion

produces cell- and protein- free filtrate

glomerular filtration

selectively returns 99% of substances from filtrate to blood in renal tubules and collecting ducts

tubular reabsorption

selectively moves substances from blood to filtrate in renal tubules and collecting ducts

tubular secretion

a passive process (no metabolic energy required), hydrostatic pressure forces fluids and solutes through filtration membrane into glomerular capsule, no reabsorption into capillaries of glomerulus occurs

glomerular filtration

porous membrane between blood and interior of glomerular capsule, allows water and solutes smaller than plasma proteins to pass (normally no cells can pass)

the filtration membrane

what are the three layers of the filtration membrane

fenestrated endothelium of glomerular capillaries, basement membrane, foot processes of podocytes

fused basal laminae of two other layers

basement membrane

which layer of the filtration membrane has filtration slits? Slit diaphragms repel macromolecules

foot processes of podocytes

label the following: efferent arteriole, afferent arteriole, glomerular capsular space, proximal convoluted tubule, parietal layer of glomerular capsule, glomerular capillary covered by podocytes that form the visceral layer of glomerular capsule

label the following: cytoplasmic extensions of podocytes, filtration slits, podocyle cell body, fenestratons (pores), glomerular capillary endothelium, foot processes of podocyte

forces that promote filtrate formation, hydrostatic pressure in glom capillaries is essentially glom BP

outward pressures

forces inhibiting filtrate formation, hydrostatic pressure in capsular space, colloid osmotic pressure in capillaries

inward pressures

sum of forces, pressure responsible for filtrate formation, main controllable factor determining GFR

net filtration pressure NFP

NFP equation

(HPgc)-(HPcs+OPgc)

outward-inward pressures

volume of filtrate formed per minute by both kidneys (normal is 120-125ml/min)

GFR

GFR is directly proportional to:

NFP, total surface area available for filtration, filtration membrane permeability

how does GFR affect systemic BP

increased GFR causes inc urine output, which lowers BP