RENAL SYSTEM Part 1 - Anatomy 2 Exam 4

Why do we need the renal system

provides us with a mechanism to filter blood

how would we describe the kidney

vascular highly perfused organ

- organ with rich blood supply

what happens as blood moves through the kidney

waste is removed

what did the renal system evolve to remove

metabolic waste products from the body

- specifically nitrogenous waste (end products of amino acid catabolism)

what is the nitrogenous waste from the body known as

urea

what are the 5 renal functions

- Excretes Metabolic End products

- regulates ion balances

- regulates osmolarity and pH

- endocrine organ

- long term regulation of blood pressure

what are the metabolic end products that are excreted

- drugs

- organic molecules

- xenobiotics

what are some of the ions regulated by the renal system (8)

Na+, K+, H+, Ca2-, Cl-, HCO3-, PO4, H20

how does the renal system control water and electrolyte homeostasis

- maintaining levels of ions (like sodium, potassium, calcium, bicarbonate)

what does maintaining levels of ions also mean that the renal system has control over

can control solute concentration of the blood

what is an important difference between the renal system and the circulatory system

renal system regulates our long-term blood pressure

how can our kidneys control long term blood pressure

ability to adjust the amount of fluid inside of our blood stream

- fluid homeostasis

what are the 4 important structures of the urinary system

- kidney

- ureter

- urinary bladder

- urethra

what are the 3 functions of the kidney

- filtration

- absorption

- secretion

function of ureter

connects the kidney to the bladder

function of the bladder

storage of urine

function of the urethra

connects bladder to external environment

where does urine go once it is produced in the kidney

travels through tubes: ureters to the bladder

where is urine temporarily stored

bladder

how does urine leave the bladder

through tube: urethra

what are the 4 anatomical parts of the kidney

- cortex

- medulla

- calyces

- nephron

what is the cortex of the kidney

outer area

- contains inner juxtamedullary region (closest to the medulla)

what is the medulla of the kidney

inner area

- contains renal pyramids

what are the 2 parts of the calyces?

minor: papillae of pyramids extend

major: converge to form pelvis

what is the nephron of the kidney? how many types and what are they

functional unit

(2 types)

- juxtamedullary

- cortical

what are the parts of the ureter that branch out called

renal calyces

- individual = calyx

if you follow a single calyx upwards, what does it leads to

triangular structures: called renal pyramid

what is the entire region inside of the pyramid called

the renal medulla

- inner most portion of the kidney

what are the regions of the renal cortex and renal medulla made from

repeating structures: nephrons

nephrons are the ____ _____ units of the kidney

basic, functional

nephrons are the structures that create and maintain...

osmotic gradients between the interstitial fluid (that surrounds them) & urine

is the gradient created and maintained by the nephron the same in all regions of the kidney?

no:

- about 300 milliosmoles in cortex

- can go to 12000 milliosmoles in deep renal medulla

what are the 5 regions of a nephron

1) renal corpuscle (bowman's capsule + glomerulus)

2) proximal convoluted tube (PT)

3) loop of Henle

4) distal convoluted tubule (DT)

5) collecting duct (CD)

where does urine that is produced by the nephron flow

flows all the way through the nephron

what is the renal corpuscle made from

- capillary network: glomerulus

what is the capillary network of the renal corpuscle surrounded by

capsule: bowman's capsule

where do things flow from bowman's capsule of the nephron

the proximal tubule & then downwards into the loop of Henle

the loop of Henle has a ___ and ___ limb

descending & ascending limb

when we come out of the ascending loop of Henle where do we go

enter the distal convoluted tubule & into the collecting duct

after it goes through the entire structure of the nephron, everything that is left in the lumen is considered what

urine

where does urine travel after it is in the collecting duct

the renal calyx & eventually into the ureter to the bladder to the urethra -> out of body

there are about _____ nephrons inside of each kidney

- each nephron produces a ___ amount of urine

1 million

- small

what are the 2 types of nephrons in our body

- cortical nephrons

- juxtamedullary

where are cortical nephrons located?

where are juxtamedullary nephrons located?

cortical: renal cortex

juxtamedullary: part in cortext part in medulla

juxtamedullary is a ___ population of nephrons that has a loop of Henle that extend into _____

- small population

- deep down into medulla

what are the functions of both of the nephron types

cortical: most renal processes

juxtamedullary: urine concentration

juxtamedullary nephrons are primarily responsible for producing ...

the osmotic gradient that is required to make concentrated urine

even though we look at a nephron that demonstrates the path of liquid, what is it important to note about the structure

nephrons are a lot more compact

- folded back on itself

- distal tubule and collecting duct are actually close to the glomerulus and bowman's capsule

what is filtration

nonselective movement of fluid & solutes out of the glomerulus and into the lumen of the nephron

where does filtration take place

only in bowman's capsule

what is reabsorption

selective movement of water or solutes from the lumen of the nephron into the BVs around the nephron

what are the BVs around the nephron known as

- cortical nephrons: peritubular capillaries

- juxtamedullary nephrons: Vaso recta

where does reabsorption take place (4)

back into blood

in the:

- proximal tubule

- loop of Henle

- distal tubule

- collecting duct

what is secretion

selective movement of water & solutes out of the peritubular capillaries & into the lumen of the nephron

where does secretion take place (3)

secretion for excretion:

- proximal tubule

- distal tubule

- collecting duct

filtration, reabsorption, and secretion happen ...

continuously

since filtration is nonselective, about ___% of the blood that is sent to the kidney is filtered

- how much is reabsorbed

20

- vast majority

what would happen if the blood was not reabsorbed

we would be peeing every 5 minutes

- have to continuously drink water with electrolytes to maintain homeostasis

over a typical day, how much of the blood is filtered by the kidney

- ____ liters of fluid every day

entire volume of the blood is filtered 50 or 60 times

- just under 200 liters

large filtration volume allows for ____

speed

what would slow and calculated filtration require us to have

would be required to have a mechanism to transport every possible substance that could end up in our blood

summarize how blood is filtered and reabsorbed

most of the blood enters the lumen of the nephron: water, solutes, and bad things

- reabsorb the things that we want -> we have transporters fort them

what is the major advantage of the non-selective filtration system

allows us to have speed AND selectivity

where does the non-selective filtration process take place

in the renal corpuscle

- because it is highly vascular

what is the vessel that carries blood into the corpuscle known as

afferent arteriole

where does the blood go after it enters the afferent arteriole

spreads through the capillary network, the golmerulus

where does blood travel after it goes through the glomerulus

blood goes out through the efferent arteriole

in the glomerulus the afferent arteriole ________ while the efferent arteriole ____

afferent: brings blood in

efferent: sends blood out

the glomerulus is made up of

fenestrated endothelial cells

what are fenestrated endothelial cells

- have relatively few tight junction proteins -> a little more paracellular transport

what is the glomerulus surrounded by

an epithelial cell lining: podocytes

what do podocytes do

wrap themselves around the glomerular capillaries

- help regulate filtration

what are the spaces between the cells in the glomerulus

filtration slits

what else is found between the glomerular endothelial cells and the podocytes

negatively charged extracellular matrix

What does the negatively charged extracellular matrix do?

helps block large or unwanted particles, especially negatively charged ones, from passing through the filtration barrier

Why don't blood cells get filtered out of the glomerulus?

the spaces between cells are too narrow: preventing large things like RBCs, WBCs, and platelets from passing through — this is called size exclusion

can plasma proteins pass through paracellularly?

often get repelled by the negatively charger matrix proteins

- typically not filtered

what are really the only things that can pass through the filtration slits

water, solutes, and really small molecules

what is the stuff that is able to be filtered out of the glomerulus into the capsular space is refered to as

filtrate / ultrafiltrate

- essentially plasma minus proteins and cells

since filtration is nonselective, what is this movement referred to as

bulk flow: governed by blood (hydrostatic) pressure

what are 3 important aspects of the filtration barrier

- fenestrated epithelium

- basement membrane (charged matrix proteins)

- podocytes

what does it mean that filtration has size exclusion

filtration is RBC and protein free

what is needed for bulk flow to occur in the glomerulus

pressure gradient

- specifically hydrostatic pressure inside of the glomerulus (like BP)

What pressure relationship is needed for filtration to occur in the glomerulus?

The pressure in the glomerulus must be higher than:

1) The pressure inside Bowman's capsule

2) The osmotic pressure from solutes in the blood

- outwards pressure > inward pressure

what is the pro-filtration force

- hydrostatic pressure inside of glomerulus (GBHP)

what are the 2 anti-filtration forces

- hydrostatic pressure inside capsule (CHP)

- colloid osmotic force (BCOP)

what is GFR

Glomerular filtration rate

- rate at which the blood is filtered into the capsule

what is GFR for normal people

- 90-120mL / min average

- 180 liters per day

what happens if any of the pressures in the renal corpuscle change

GFR will change

the afferent arteriole has a _______ radius than the efferent arteriole at rest

- what does this help to create

slightly larger

- helps to create the pressure necessary for filtration

what can glomerular pressure be changed by

by changes to the radius of either the afferent or efferent arterioles

what would happen if we constricted the afferent arteriole

we would prevent blood from moving into the glomerulus

- decrease hydrostatic pressure inside the glomerulus -> decrease GFR

(kink in garden hose)

what would happen if we dilated the afferent arteriole

brings more blood into the glomerulus & increase the hydrostatic pressure

- increases GFR

is it possible to produce same effects by adjusting radius of efferent arteriole

yes: but mostly happens to afferent

what would happen if we constricted the efferent arteriole

- increase blood inside the glomerulus (would not be able to leave)

- increase pressure & increase GFR

what would happen if we dilated the efferent arteriole

easier for blood to leave the glomerulus

- pressure drops & GFR decreases

what are the 3 mechanisms to regulate GFR to changes in pressure

3 variables

1) arterial pressure

2) afferent arteriole resistance

3) efferent arteriole resistance

filtration is determined by ____ which is determined by ___

filtration is determined by hydrostatic pressure and hydrostatic pressure is determined by blood pressure

if filtration is determined by hydrostatic pressure which is determined by blood pressure, does blood pressure changes affect kidney function?

usually does not happen under normal circumstances bc GFR stays relatively constant

how do we change GFR

we would need an extremely low or high pressure

- needs to be drastic because we have the ability to make minor changes to renal blood flow