anatomy 2 exam 3 choi

urinary system components

kidneys, ureters, urinary bladder, urethra

when filtrate is converted to urine different physiological processes occur:

elimination of metabolic wastes

regulation of ion levels

regulation of acid-base balance

regulation of blood pressure

elimination of biologically active molecules

elimination of metabolic wastes

kidneys remove waste within filtrate so these substances don’t reach toxic levels within blood

regulation of ion levels

kidneys help control bloods ion balance, like Na, K, Ca, phosphate ions by eliminating them via urine

regulation of acid base balance

kidneys, by altering levels of H and bicarbonate ions

regulation of blood pressure

help by excreting fluid in urine, regulating fluid loss helps regulate blood volume

kidneys can release renin which is required for production of angiotensin

elimination of biological active molecules

small molecules are filtered but aren’t reclaimed and then become part of urine

kidneys function in addition to filtering blood and processing filtrate

formation of calcitriol

production and release of erythropoietin

potential to engage in gluconeogenesis

formation of calcitriol

this hormone increases absorption of calcium from small intestine (increased blood calcium concentration)

production and release of erythropoietin

your kidneys can respond to low oxygen levels by secreting (EPO) hormone (increased erythrocyte formation)

potential to engage in gluconeogenesis

during fasting/starvation, kidneys may produce glucose from noncarbohydrate sources to maintain normal glucose levels

kidneys take care of blood by

removing unwanted materials from blood

maintaining blood plasma ions

regulating blood pH

altering blood volume

regulating number of erythrocytes

maintaining blood glucose levels during fasting/starving

kidney anatomy

symmetrical bean shaped organ

hilum

adrenal gland on tophi

hilum

concave medial border where vessels, nerves, and ureter connects to kidney

kidneys located

posterior wall, lateral to vertebral column

left - between T12 and L3

right - inferior to left

tissue layers surrounding and supporting kidney

fibrous capsule

perinephric fat (adipose capsule)

renal fascia

paranephric fat

fibrous capsule/renal capsule

directly adhere to external surface of kidney

dense irregular CT

maintain shape, protects form trauma, prevents pathogens from penetrating

perinephric fat (adipose capsule)

adipose CT

provides cushioning and stabilizatino

renal fascia

dense irregular CT

anchors kidney to surrounding structures

paranephric fat

outermost layer surrounding the kidney

composed of adipose CT — cushion and stabilize

renal ptosis and hydronephrosis

loss of adipose CT in thin or elderly with anorexia

• dropping of kidney

can cause kink in ureter

• decrease urine flow

• urine backs up into proximal part of ureter

• enlargement of renal pelvis

parenchyma

functioning tissue

renal cortex and medulla re

renal columns

extensions of cortex, projects into medulla and subdivide it into renal pyramids

corticomedullary junction

wide base of renal pyramids, external edge of medulla, where it meets the cortex

renal papilla

medially directed tip of renal pyramidre

renal sinus

medially located space

urine drainage area

minor and major calyces and renal pelvis

functional anatomy of kidney includes:

nephrons

collecting tubules

collecting ducts

other associated structures n

nephrons

microscopic, functional filtration unit of kidney consist of a renal corpuscle and renal tube

almost all reside in the cortex

renal corpuscle

enlarged round portion of a nephron within renal cortex

composed of glomerulus and glomerular capsule

glomerulus

thick tangle of capillary loops

blood enters by afferent arteriole and exits by efferent arteriole

glomerular capsule/bowman’s capsule

formed by visceral and parietal layers

between layers = capsular space that receives filtrate, then modified to form urine

opposing poles of renal corpuscle

vascular and tubular

vascular pole

where afferent and efferent arterioles are attached to glomerulus

tubular (urinary) pole

where renal tubule originates

renal tubule

makes up remaining part of nephron

proximal convoluted tubule, nephron loop/loop of Henle, distal convoluted tubule

proximal convoluted tubule

first region of renal rube, originates from tubular pole, brush border, most reabsorption occurs here

proximal tubule cells/epithelium

simple cuboidal packed with mitochondria because of high ATP demand for active transport

also contains apical microvilli

regions of nephron loop/loop of henle

descending and ascending limb

descending limb

thin segment of simple squamous epithelium

permeable to water (aquaporins), impermeable to solutes

• water moves out into hypertonic medulla → filtrate becomes concentrated

ascending limb

thick segment, cuboidal cells with mitochondria

impermeable to water, actively transports Na, K, Cl out into medulla

• filtrate becomes diluted as ions leave but water cannot follow

c

countercurrent mechanism

descending limn loses water; ascending limp pumps out ions →creates osmotic gradient

distal convoluted tubule

fewer microvilli (no brush border) → less reabsorption surface area

cuboidal cells, fewer mitochondria

• reabsorbs Na and Cl

impermeable to water unless ADH is present

involved in Ca reabsorption under parathyroid hormone control

collecting duct

often considered part of the renal tubule system

principal cells and intercalated cells

principal cells

respond to ADH (water permeability) and aldosterone (Na reabsorption/K secretion)

intercalated cels

regulate acid-base balance (H+ or bicarbonate)

cortical nephron

renal corpuscle located near edge of cortex

short loop of Henle that barely penetrates the medulla

produces “dilute” urine

~85% of nephrons

filtrate and reabsorption of solutes and nutrients

efferent arteriole forms peritubular capillaries around PCT and DCT

Juxtamedullary nephron

~15%

renal corpuscle is adjacent to corticomedullary junction

long loop of Henle deep into medulla

vasa recta (long straight capillaries) run parallel to the loop of Henle

key role in concentrating urine via countercurrent multiplier system

crucial during dehydration, allowing water reabsorption

urine formation

several nephrons drain into each collecting tubule

• 1000s of collecting tubules empty into larger collecting ducts which project through medulla toward renal papilla

collecting duct drains into a papillary duct

then papillary duct drains into minor calyx

juxtaglomerular apparatus

comes in close contact with afferent arteriole of same nephron

• serves as sensor and regulate that helps the kidney control filtration rate and systemic blood pressure

granular cells, macula densa,

granular cells

modified smooth muscle cells of afferent arteriole

• act as baroreceptors (detect BP changes)

• secrete renin when BP drops

macula densa

modified epithelial cells within wall of DCT

signal granular cells to release renin by detecting changes in NaCl concentration of the DCT

low blood pressure detected/response

→ less filtration and slower filtrate movement → more time for reabsorption

• low NaCl levels → release of renin

high blood pressure detected/response

→ more filtration and faster filtrate movement → less time for reabsorption

a filtrate is formed when blood flows __

through the glomerulus, and some components enter capsular space

2 fluid patterns (as a result of filtrate through glomerulus)

flow of blood into and out of kidney

flow of filtrate, tubular fluid, and urine through the nephron and other urinary structures

when blood 1st enters from afferent arteriole into the glomerulus__

the blood is filtered

when blood reaches the 2nd capillary bed of either the peritubular capillaries or the vasa recta __

the exchange of respiratory gases, nutrients and waste occur

(after gas, nutrient, and waste exchange) peritubular capillaries and vasa recta then__

drain into network of veins

when blood flows through the glomerulus and filtered:

both water and solutes move from blood plasma across filtration membrane and into bowmans capsule to form filtrate

then PCT→ loop of Henle → DCT→ collecting tubule → collecting ducts …

once tubular fluid enters papillary duct its now called

urine !

flow of urine

minor → major calyx → renal pelvis → ureter → urinary bladder→ urethra

when is fluid called filtrate?

when in capsular space

when is fluid called tubular fluid?

first when entering PCT

remains while in loop of Henle, DCT, collecting tubules, collecting ducts

when is fluid called urine?

first in papillary duct

then in minor + major calyx, renal pelvis, ureter, urinary bladder, urethra

urine is formed through

(glomerular) filtration, (tubular) reabsorption, (tubular) secretion

glomerular filtration

occurs at renal corpuscle - specifically across glomerular capillaries and Bowmans capsule

• water and solutes are separated from blood plasma , then cross the filtration membrane to enter Bowman’s capsule

this separated fluid is what the filtrate is

tubular reabsorption

along renal tubule and collecting duct, mainly in proximal convoluted tubule

substances move from tubular fluid → into peritubular capillaries

typically all vital solutes and most water in filtrate are reabsorbed

• excess remain in the tubular fluid

tubular secretion

movement of solutes out of blood within the peritubular capillaries and vasa recta into the tubular fluid

materials that are moved into the tubules are to be eliminated from the body

secretion results in excretion (urine)

tubular reabsorption and secretions are

occurring in opposite directions

during reabsorption: substances move from tubular fluid to blood; secretion: blood into tubular fluid

generally more reabsorption than secretion

filtration membrane is

porous, thin, negatively charged structure that serves as a filter

composed of 3 layers: endothelium of glomerular capillary (fenestrated), basement membrane of glomerular capillary, visceral layer of Bowman’s capsule

for a substance to become part of filtrate must pass through layers

endothelium of glomerular capillary (filtration membrane)

allows plasma an dissolved substances through, but not large structures. I.e. formed elements (RBC, WBC, platelets)

basement membrane of glomerular capillary (filtration membrane)

restricts passage of large plasma proteins, while allowing smaller substances to pass through

visceral layer of Bowman’s capsule (filtration membrane)

composed of podocytes

pedicels of 1 podocyte interlock with pedicels of another

between pedicles is filtration slits that restrict passage of most small proteins

freely filtered substances (filtration membrane)

water, glucose, amino acids, ions, urea, hormones, water soluble vitamins, and ketones can easily pass through and become filtrate

not filtered substances (filtration membrane)

formed elements and large solutes, restricted from becoming part of filtrate

limited filtration (filtration membrane)

intermediate sized proteins are generally not filtered due to size or negative charge, only limited amounts can become part of filtrate

filtrate is

filtered plasma with certain solutes and minimal amount of protein

(components of blood that aren’t filtered exit the renal corpuscle through efferent arteriole)

pressures associated with glomerular filtration

filtrate is formed due to the differences between hydrostatic pressure of blood and opposing osmotic blood pressure and fluid pressure in Bowman’s capsule

glomerular hydrostatic pressure

pushes water and some dissolved solutes out of blood

glomerulus → bowman’s capsule

blood colloid osmotic pressure

pressure exerted by the blood due to unfiltered dissolved solutes it contains (plasma proteins; colloid)

capsular hydrostatic pressure

pressure created by filtrate present already within Bowman’s capsule

presence of this filtrate prevents movement of additional fluid from the blood into the Bowman’s capsule G

Glomerulus filtration rate (GFR)

rate at which the volume of filtrate is formed (volume/time)

influenced by net filtration pressure (NFP)

as NFP increases this also increases and vice versa

Increased HP→ Increased NFP also increases

GFR

amount of filtrate formed

solutes and water remaining in tubular fluid, substances in urine

(decreases filtrate reabsorbed)

GFR primary influenced by

changes in luminal diameter of afferent arteriole

alteration of the surface area of he filtration membrane

processes involved with GFR regulation

intrinsic control (within kidney)→ renal autoregulation that keeps it at normal level

extrinsic control (external to kidney)

• → nervous system regulation results in decrease

• → hormonal regulation results in increase

renal regulation (intrinsic control) (GFR)

maintain a constant blood pressure and GFR despite systemic atrial pressure changes

only effective if systemic mean atrial blood pressure is between 80 and 180 mmHg

what happens is MAP is too low?

filtration and elimination of urine ceases, resulting in accumulation of toxic metabolic wastes in the blood wh

what happens when MAP is too high?

increase in both glomerular blood pressure and GFR → increased amount of urine

neural control sympathetic division (extrinsic control) (GFR)

decrease in GFR

through vasoconstriction of afferent arteriole and decreased surface area of filtration membrane

hormonal control atrial natriuretic peptide (extrinsic control) (GFR)

increased GFR to eliminate fluid from the blood

released from atrial cardiac muscle cells into blood in response to the stretch of chambers

causes vasodilation in afferent arteriole

substances that weren’t initially filtered at the glomerulus can also be eliminated from blood into

tubular fluid via secretion

substances must cross the simple epithelium of tubule wall

• can pass through via paracellular transport or transcellular transport

transcellular transport

a substance must cross through 2 plasma membrane

1. luminal membrane: in contact with tubular fluid

2. basolateral membrane: rests on basement membrane

reabsorption and secretion occurs along entire nephron tubule, collecting ducts and tubule, but most reabsorption occurs__

in the PCT, where uptake processed are aided by microvilli

transport maximum

maximum amount of substance that can be reabsorbed across the tubule epithelium

• depends on the number of transport proteins in the epithelial cell membrane

• as long as tubular fluid contains no more than this amount of glucose, all of the glucose will be absorbed. If it exceeds this any additional glucose will not be absorbed

renal threshold

the maximum plasma concentration of a substance that can be transported in the blood without being excreted in the urine

substances reabsorbed from tubular fluid back into blood

nutrients and small amounts of filtered plasma proteins

glucosuria

in healthy individuals: no glucose in urine

in diabetes mellitus: glucose found in urine

glucose acts as a osmotic diuretic meaning

it pulls water with it, more glucose left in renal tubule →more water pulled in

polydipsia

excessive dehydration and thirst

• frequent urination, intense thirst, fatigue

proteinuria

protein in the urine

may be caused by renal disease that results in higher than normal filtration of plasma proteins

will result in blood concentration of all plasma proteins to decrease

see increased blood concentration of these plasma proteins

if tubule cells are damaged they can’t reabsorbed small proteins that pass the filter → proteins stay in urine