Urinary System Flashcards
Total Body Water
Body weight = ______ + ______
Solids (40% for males, 50% for females)
Water (60% for males, 50% for females)
This difference due to sex reflects the _________ of larger mass of adipose tissues in females and larger mass of muscle tissues in males.
solids + water
proportionality
Solids →
proteins, lipids, carbohydrates, minerals
The water component (TBW) can be divided into the total body fluid:
extracellular fluid (1/3) + intracellular fluid (2/3)
TBW = ECF (1/3) + ISF (2/3)
What makes up the extracellular fluid vs the intracellular fluid?
What is main fluid input?
Main fluid input is from food and water from the gastrointestinal tract = 2500 ml water required per day
Water moves passively through fluid compartments in response to osmotic gradient
What is main fluid output?
Main fluid output occurs from kidney, lungs, GIT, skin = 2500 ml of water is lost everyday
If fluid becomes excess and accumulates in the interstitial fluid forming a clog. The body then helps drain the excess fluid through the lymphatic system from the interstitial fluid to the venous circulation.
Main electrolytes in the plasma are:
sodium, potassium, calcium, chloride and then a small amt of proteins
The concentration of these electrolytes are relatively the same in both the plasma and the ________ fluid,
except for proteins, which are found in the plasma and intracellular fluid only, not the interstitial fluid. These
electrolytes can passively move between the ______ membrane and interstitial fluid through a semipermeable membrane but require protein channels to assist movement from interstitial fluid to intracellular fluid.
interstitial
plasma
Which ions make up the extracellular fluid vs the intracellular fluid?
What is Albumin?
Albumin is the main protein found in plasma which helps maintain osmotic gradient by keeping water in blood vessels.
Bicarbonate ions are important in acid base balance
Function of the Excretory system: (3)
- To maintain homeostasis
- Controls volume of body fluids (water)
- Balances chemical composition of body fluids by balancing the solute concentration → dissolved solute concentration as well as different ions, vitamins + minerals in the body
a) Physiological fluid inside the lumen of blood vessels is part of the ______ fluid compartment?
extracellular
b) What is fluid inside of a cell called?
Intracellular fluid
c) What is fluid that is present outside of a cell called?
Extracellular fluid
d) What is the fluid in between cells called?
Interstitial fluid
e) Which compartment contains majority of fluid by mass in the human body?
Intracellular fluid compartment
f) How do body fluid compartments differ with respect to their volumes and their ionic compositions? (2)
- Volumes: ECF makes up 1/3 of the total body water (plasma = 20% + interstitial fluid = 80%) and ICF makes up 2/3 of the total body water
- Electrolytes in solution: both plasm and interstitial fluid have similar concentrations of Na+ K+ Ca2+ Cl- due to passive transport through semipermeable membrane. Only plasma and ICF have proteins such as albumin which helps to maintain osmotic gradient.
g) What are the driving forces responsible for movement of water across cell membranes and the capillary
wall?
Osmotic gradient + Osmolarity
h) What types of transport mechanisms allows for solute movement across the fluid compartments? (3)
- Passive transport: from plasma to ISF. Passive diffusion, no energy required through semipermeable
membrane. - Facilitated diffusion via protein channels allowing for movement of ions from ISF to ICF
- Active transport
Sexes:
TBW - ___% for males and ___% for females.
- Males have higher muscle mass whereas females have higher ___ content.
60%
50%
fat
Ages:
Infants:
____ of their total body weight is made up of water as they are still developing and have low body fat and low
bone mass.
_______ is dangerous for infants as it causes extreme water loss (dehydration) and hence in infants, extreme
body weight loss
Water content declines with old age.
75%
Diarrhoea
EQUATIONS
Body Weight x 0.60 = TBW
Use 60 – 40 – 20 rule to calculate ____ %
TBW = 0.60 x _____ ______
ICF = 2/3 x TBW OR ICF = 0.40 x body weight
ECF = 1/3 x TBW OR ECF = 0.20 x body weight
ISF = ECF x 0.____
Plasma = ECF x 0.____
TBW
body weight
80
20
Cells with _______ fluids are bathed in the interstitial fluids, and then blood plasma and _______ fluids will experience an exchange of contents or solutes depending on the different processes taking place within the body.
intracellular
interstitial
_______ + an
individual’s body
type + season will
change water gain
and water loss
amount.
Sweating
What does this table show? (2)
- This table just shows that the amount of water within the body gained is roughly equal to the amount of water lost during different processes. This helps to maintain a somewhat balanced amount of water content within the body of the individual.
- This is also down to personal experience – not every individual will actually experience the figures above.
What is the distribution of various cations and anions within the ECF and ICF?
Plasma and interstitial fluid in the extracellular fluid have similar concentrations of ions in solution.
Notice sodium and potassium differences in the ICF and the ISF (sodium-potassium pump). Proteins inside
the cells are also higher due to protein synthesis within cells.
How do animals regulate water and salt concentrations?
- Osmosis → passive diffusion of water/solvent from a solution of low solute concentration to a solution of
high solute concentration through a semi-permeable membrane.
Animals transport salts and thereby direct water movement into and out of cells by osmosis.
- Osmolarity → concentration of solution expressed as the total number of solute particles per litre.
Considers total concentration of penetrating solutes and non-penetrating solutes
The solute concentration of a solution determines the movement of water across a selectively permeable
membrane.
Hyperosmotic =
→ high solute concentration → water moves INTO cell → cell swells and lyses
Hypoosmotic =
→ low solute concentration → water moves OUT of cell → cell shrivels
Isosmotic =
→ solute concentration = in outside and inside of cell) → no net movement → cell in osmotic balance
Tonicity =
→ measure of effective osmotic pressure gradient. The ability of a solution surrounding a cell to
gain or lose water.
1. Hypotonic
2. Hypertonic
3. Isotonic
Osmolality →
Number of dissolved particles in fluid. Osmolarity is ultimately the concentration of a solute (measured per osmole). It will determine if a certain fluid needs
to experience a net flow of water into or out of that solution.
Transport of water and ions
2 routes of transport from luminal to basolateral side of tissue:
- Transcellular transport
- Paracellular transport
What is 1. Transcellular transport?
Luminal membrane → cytosol → basolateral membrane → interstitial fluid → capillary through diffusion
Diffusion across the cytosol within the cell. Transcellular can be either active or passive, depending on what
is being
What is 2. Paracellular transport?
Movement through leaky tight junctions.
Types of transport: (2)
- Active transport
- Passive transport
Epithelia are specialized to aid transport of ions and
water through the cell and the plasma/capillary Hydrostatic + osmotic pressure allows movement between membranes
How is fluid balance maintained?
Maintaining fluid balance requires that the relative concentrations of solutes and water be kept within narrow limits. Several mechanisms have evolved for ridding the body of nitrogenous metabolites (end products of cellular metabolism) and other metabolic waste products, a process called excretion which ensures that different metabolites and all the fluid or solute concentrations of the body be maintained under the narrow limits.
Metabolic waste →
→ end products of metabolic reactions. These products depend on your lifestyle + consumption. Kidneys try to remove any substance that is deemed unnecessary or contextually useless at hat point in the metabolising process
→ metabolic waste
What is urea? (3)
- by product of breakdown of proteins
- Proteins are broken down into amino acids. Amino groups are then removed forming toxic ammonia which
is then converted into urea in the liver. - Humans excrete urea , which is less toxic than ammonia
- Protein’s amino acids forms _______→ liver converts to urea
ammonia
What are the advantages of urea?
Advantages of urea are its low toxicity and high solubility in water. Conversion of ammonia to urea is energetically expensive; excretion of urea requires less water than ammonia.
What is Uric acid?
by product of breakdown of DNA/RNA (nucleic acids)
Uric acid link to gout and kidney stones
- Product of nucleic acid catabolism
Nucleic acids are broken down into nitrogenous bases and then converted into uric acid. Is less toxic but requires a lot of energy.
3 ways to classify waste products:
urea, uric acid, ammonia
- Solubility in water
- Toxicity
- Energy costs
Functions of the Urinary System:
Structure of the Kidney:
Structure of nephron:
Basic structural components of the nephron:
Nephrons are the functional units of the kidneys:
1. Juxtamedullary nephrons:
With a long nephron loop. They from about 15% of all the nephrons within the kidneys → produce highly concentrated urine.
Nephrons are the functional units of the kidneys:
2. Cortical nephrons:
With a short nephron loop. They from about 85%
of the nephrons within the kidneys. The blood associated with these nephrons are different as well as the general shape and size of the loops as well.
The nephron is composed of two fundamental parts:
1) Renal corpuscle
2) Renal tubule
What is the renal corpuscle?
Made of the bowman’s capsule and inner glomerulus.
What is the renal tubule?
Made of the distal convoluted and proximal convoluted tubules; as well as the loop of Henle (lies in the salty renal medulla).
True or False
The collecting ducts are not part of the nephrons because multiple tubules can drain into the same collecting duct.
True
Renal corpuscle = _________ (capillaries) + Bowman’s capsule
Capillaries run from _______ arteriole to ________ arteriole as filtration occurs from glomerulus to the
Bowman’s capsule
Glomerulus
afferent
efferent
Ultra-filtration barrier: (3)
- allows molecules < 1.8 nm freely filter (water, sodium, inulin, glucose) while molecules > 3.6 nm are not filtered (haemoglobin)
- Has 3 layers:
Endothelium of capillary which has pores called fenestration which allows almost everything through
except blood cells. Basement membrane prevents filtration of large proteins. Podocytes have finger-like projections called pedicels that have slits in them that allow for only small molecules to pass - Is charge selective
All 3 layers contain negatively charged glycoproteins which makes it difficult for negative ions to pass
Starling forces →
→ balancing forces that favour filtration and those that oppose it
Hydrostatic pressure →
→ force a fluid exerts on the walls of a compartment (walls of capillaries or Bowman’s capsule)
- Allows for fluid to be pushed out
Oncotic pressure →
→ force exerted by plasma proteins on the walls of a compartment
- Allows for fluid to be drawn in
Major driving forces of filtration: (4)
- Hydrostatic pressure of Glomerulus which forces fluid out of capillary
- Hydrostatic pressure of Bowman’s capsule
- Oncotic pressure of glomerular capillary proteins
- Ignore oncotic pressure of Bowman’s capsule as the number of proteins is very tiny
Net filtration pressure =
= HPgc – HPcs – πgc
GFR (glomerular filtration rate) is used to determine filtrate amount made by all ____ _____ for both kidneys per minute. → to determine kidney function
GFR = (surface area available for filtration x permeability of glomeruli) x Net filtration ______ (NFP)
GFR = Kf x ___
renal corpuscles
pressure
NFP
Surface area of glomerulus increased by:
Greater than usual surface area and permeability
- Branching + looping
- Fenestrations
∴ Kf is ____ therefore ____ filtration rate
________ afferent arteriole will lower glomerular blood hydrostatic pressure as less amount of blood
available for filtration. This then lowers NFP and hence the GFR.
high
high
Constricting
Urine formation
3 basic processes: (4)
- Filtration – filtering of body fluids from blood
- Reabsorption – reclaiming valuable solutes
- Secretion – adding nonessential solutes, toxins and wastes from body fluids
- Excretion – release of processed filtrate with N-wastes, toxins
FILTRATION
How does blood enter and leave the glomerulus capillary?
Notice the difference in the diameters of the afferent and the efferent arterioles; the afferent has a larger
diameter for more blood volumes, whereas the efferent arteriole has a smaller diameter for less blood volume
(after filtration). Afferent arteriole are thicker than efferent arteriole to allow for more blood to flow in
The coiling of the glomerulus also increases the surface area of the glomerular capillaries.
Reabsorption
Secretion
Blood is supplied into the afferent arteriole, it then moves into the thinner inner glomerulus capillary beds,
where the pressure of the arteriole causes the filtration to take place, and the efferent arteriole (taking blood
away) has lower pressure to allow for the processes of reabsorption and secretion to take place.
Filtration Membrane
Layers of glomerular capillaries: (3)
- Capillary endothelium covered in pores or fenestrations
- Basement membrane
- Single epithelial lining of Bowman’s capsule with podocytes with filtration slits which facilitate filtration process
Glomerular filtration:
→ movement of protein-free solution of fluid and solutes from blood (glomerulus) into the glomerular capsule (Bowman’s)
- Structures of the renal corpuscle facilitate filtration
- Driven by high blood pressure in glomerular capillaries
Glomerular hydrostatic pressure promotes ______ whereas Blood osmotic pressure and Capsular hydrostatic pressure ______ filtration.
filtration
oppose
Regulation of filtration rate
When you are under resting conditions vs stressful conditions: (3)
- Constriction of arterioles (redistribute blood to parts of the body that need help rather than kidneys) → diameter adjustment
- During resting conditions, afferent arteriole diameter is adjusted
- During stressful conditions, afferent and efferent arteriole diameter are adjusted
Glomerular filtration rate (GFR)
Volume of filtrate formed per minute by both kidneys (normal = ___-____ ml/min)
An increase or decrease in systemic blood pressure will affect GFR
120 – 125
Filtration of small molecules is nonselective
- filtrate in Bowman’s capsule is a mixture that mirrors the concentration of various solutes in the blood
plasma = ______ ______
- Filtrate = blood plasma - plasma protein and blood cells
glomerular filtrate
Proteinuria:
appearance of protein in urine
Glomerulonephritis:
damage to glomeruli
Glomerulonephritis:
damage to glomeruli
Haematuria:
presence of blood in urine
What happens to the glomerular filtrate? (3)
- The amount of filtrate formed = 125ml/min; 180 L per 24hrs
- We excrete 1.5l/day (~1ml/min)
- What happens to the remaining 178.5l? → Reabsorbed & placed back into blood circulation
What is the Proximal Convoluted Tubule?
Role in reabsorption of sodium, glucose, amino acids, and chloride ions
This is the longest and the most coiled part of the renal tubule, therefore it only makes sense that the most
reabsorption takes place then.
65% - 70% water reabsorbed
What are the features of the proximal convoluted tubule? (2)
- Brush border (microvilli) → increase SA for absorption
- Mitochondria → provide energy for active transport
Two processes, active and passive processes, drive the reabsorption process as a whole. The reabsorption of
____ (and the presence of the sodium potassium pump) begins this entire process.
sodium
How does Sodium reabsorption take place? (3)
- 67% reabsorbed in proximal tubule → vital role in reabsorbing glucose, AA, water, Cl, and urea
- 25% reabsorbed in ascending loop of Henle → occurs with Cl and K → vital role in ability to produce urine of various concentrations and volumes
- 8% absorbed in distal convoluted tubules and collecting ducts, varies in subjected to hormonal control (aldosterone and the Renin-Angiotensin system).
Sodium potassium pump → to maintain gradient so that sodium can be reabsorbed
- ____ concentration of Na+ from inside the cell to a high concentration of Na+ outside the cell.
- ____ concentration of K+ from outside the cell to a high concentration of K+ inside the cell.
Low
Low
What is the Main driving force is reabsorption of sodium? (7)
- Active transport (sodium-potassium pump) of Na+ from proximal tubule cell to the interstitial fluid close
to the peritubular capillary - It diffuses into the capillary which forms an electrical gradient from the accumulation of cations
- Movement of sodium also forms concentration gradient allowing for further facilitated diffusion of
sodium - This concentration gradient drives the movement of chlorine ions from the tubule to the interstitial fluid
and then to the capillary
The electrical gradient of sodium in the capillary is balanced by the movement of chlorine ions forming
an osmotic gradient
Due to movement of positively charged ions, the chloride negative ions are driven across the proximal
tubule cell membrane as well. This is done to neutralise the electrical differences. - The osmotic gradient causes water to flow from high concentration to a low concentration from tubule to
capillary - Secondary active transport/co-transport, the glucose and amino acids diffuse into the interstitial fluid
because of the processes of sodium movement across the membranes. - Glucose + amino acids diffuse through the tubule to the interstitial fluid to the capillary
Tubular reabsorption returns filtered water and solutes to blood
Proximal tubule has _____ receptors which can only bind to a certain amount of glucose so if there is high amounts of glucose in blood, the protein receptors will be overloaded and not be able to accept anymore glucose to be reabsorbed therefore glucose will come out in the urine
(Glucosuria – common in Diabetes mellitus)
_____ of filtered glucose, amino acids, bicarbonate and
50% urea are reabsorbed
protein
100%
