Lecture 2: Renal Physiology: Body Fluid Composition Flashcards Preview

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Flashcards in Lecture 2: Renal Physiology: Body Fluid Composition Deck (39):
1

Kidney Lobe

Cortex: Glomerulus + Parts of Distal and Proximal Tubule
Medulla: Collecting ducts + Loops of Henle
Nephrons: lie from deep --> outer locations
- close to junction of medulla and cortex
Collecting Ducts fuse --> Large size for larger volume --> Renal Papillae
Medullary Rays: CD + Prox. + Distal Tubule Straight bundles. Centre of Lobule. In Cortex, going too and from Medulla.
Defined by Interlobar blood vessels. - Define but not continuous

2

What types of loves do cats and mice have?

Unilobar kidneys

3

Arterial Blood supply to the kidney

Renal artery --> Interlobar arteries --> Arcuate (Arching) artery --> Interlobular artery --> Afferent arterioles

4

Function of Arterial Outer Renal Corpuscles

Corpusles Located in cortex
1. Efferent arterioles --> forms Peritubular capillary bed
2. Venous return logically in reverse order: (Interlobular --> arcuate --> interlobar)
Overall: Renal a --> Interlobar a --> arcuate a --> interlobular a --> afferent a/g --> efferent v/g --> interlobular v --> arcuate v --> interlobar v --> Renal v

5

Function of Arterial Inner Renal Corpuscles

Corpuscles Located in Medulla
1. Arterial Vasa Recta:
a) Long and straight vessels
b) bundled with Collecting duct + Loop of Henle
c) Branches to capillary bed around loops
3. Venous return occurs via the Vasa Recta (also bundled)
Overall: Renal a --> afferent a/g --> arterial vasa recta -->efferent v --> acruate v --> venous vasa recta --> Renal v

6

Function of Arterial Peritubular capillaries

Wrap around proximal tubules
- Reabsorb the nutrients which kidney's filter
- Later returning to venous capillary bed

7

Location of nephron to outer/inner renal corpuscles

Nephron sits within the Outer corpuscles Peritubular capillaries and within the Inner corpuscles Vasa Recta
- Allows countercurrent relationship of tubules (creating urine) and capillaries/vasa recta (creating blood supply)

8

What is the reasoning behind the Looping of the Vascular Vasa Recta and the Urinary Loop of Henle?

Looping preserves the medullary salt gradient
Allows:
1. Preservation of salt levels in the urine --> Able to concentrate urine when leaving the medulla
2. Medullary salt gradient --> Water extraction from nephron and reabsorption into vascular vasa recta --> preserves salt deposited in the medulla

9

Overall Flow of Outer Renal Corpuscle Arterial system

Renal a --> Interlobar a --> arcuate a --> interlobular a --> afferent a/g --> efferent v/g --> interlobular v --> arcuate v --> interlobar v --> Renal v

10

Overall Flow of Inner Renal Corpuscle Arterial system

Renal a --> afferent a/g --> arterial vasa recta -->efferent v --> arcuate v --> venous vasa recta --> Renal v

11

Cellular components of the Ureter and Bladder

1. Mucous membrane: a) lubrication b) protection for acidic urine + pathogens
2. Transitional epithelium: (when folded permits expansion and contraction)
3. Sub-epithelial CT/ Elastic Lamina Propria: allows epithelium to open and close again
4. Smooth muscle layers: ILOC 2x layers allowing for peristatic contraction
5. Outer Adventitia: a) elastic b) harbours blood supply (vasovasorum)

12

Smooth muscle components of the Ureter and Bladder

2x layers: ILOC
Inner Longitudinal + Outer Circular
= Allows for peristaltic contraction and hence movement of fluid

13

Bladder Epithelium

Bladder is a continuation of the ureter but on a larger scale
Relaxed Bladder epithelium: Folded back on itself
Contracted Bladder epithelium: Single layer

14

Urethral Epithelium

Urethra's epithelium will change according to how close it is to the external environment/outside of the body --> becomes increasingly protective
1. Initial Transitional epithelial lining -->
2. Stratified Columnar -->
3. Stratified Squamous

15

Fat cells and Water

Fat cells dont pack that much water
Reason for proportional quantities of body water: Larger quantity of fat cells (females and elderly) = Small amount of body water (50%)

16

Variation in Levels of Human Body Water and reasoning

Average Human: 50-70% water
- Babies: 70%
- Males: 60% (42L)
- Elderly and Females: 50% (30L)
Reason for proportional quantities of body water: Quantity of fat cells --> Fat cells dont pack that much water --> therefore larger quantity of fat cells (females and elderly) = Small amount of body water (50%)

17

Where is water located in the body?

1. Inside cells/ Intracellular fluid/ ICF (28L)
2. Outside cells/ Extracellular fluid/ ECF (14L) --> (80% Interstitial fluid 11L + 20% Plasma 3L)

18

How does the water move between compartments?

All the membranes in the body are permeable to water
- with exception of Kidneys, Ureters and Bladder --> due to tight membranes/ inbuilt mechanisms
Water moves for a high to low concentration of Osmotically active molecules

19

Directionality of water movement

Water moves from a high to low concentration of osmotically active molecules

20

Osmolality

Number of osmotically active particles per UNIT WEIGHT of SOLVENT
mOsmol/kg of solvent (e.g. water)
e.g. 13 solute particles + 1 kg water
= Osmotic pressure exerted by a solution across a membrane

21

Osmolarity

Number of osmotically active particles per LITRE of TOTAL SOLUTION
e.g. 13 solute particles + (1 kg water - 13 solut particles = to make combined 1 L of total solution)
mOsmol/L

22

Comparison b/w osmolality and osmolarity

Molal solution is Approximately equal to a Molar solution
Although osmolality and osmolarity differ,
Osmolality: expression of osmotic activity per weight (kg)
Osmolarity: expression of osmotic activity per L of total solution
for clinical purposes they are similar
Osmolality has now largely replaced Osmolarity

23

Tonicity

Osmotic pressure a solute exerts across a cell membrane DUE TO BEING IMPERMEABLE--> creates water movement
- created by NON-osmotically active compounds
- Property of Solution in reference to a particular membrane
- Tonicity is NON-readily measurable mmHg (unlike osmolality)

24

Why is tonicity important

1. Cell membrane is a permeable membrane
2. Bodies are full of salt and water
3. Bodes are full of impermeable molecules --> exert pressure (as part of the solute) on cell membranes --> creates water movement

25

Plasma Membranes and Tonicity

Plasma membranes: SEMIpermeable --> Permeable to water but NOT permeable to charged molecules
Cells are full of proteins which are osmotically active but impermeable to the membrane (e.g. proteins) --> compensate by exerting pressure on membrane --> creates water movement towards the charged protein molecules

26

3x solution tonicity types

1. Hypotonic: make cells swell (water moves in as higher concentration inside cell)
2.Isotonic: cell stay the same size (water movement in and out of the cell at the same rate)
3. Hypertonic: make cells shrink (water moves out of cell as lower concentration inside cell)

27

Gibbs-Donnan Equilibrium

Charged particles separated by a semi-permeable membrane can fail to distribute evenly across the membrane due to the presence of a non-diffusible ion

28

Gibbs-Donnan Equilibrium in motion

1. Negative ions want to move down their concentration gradient
2. Positive ions want to follow negative ions (to balance charge) --> so remains electrogenic
--> now have lots of osmotically active particles on one side
3. Negative protein is drawing in molecules --> but these ions want to go back again due to THEIR OWN CONCENTRATION gradients --> -ve Charged protein molecules are still unable to cross membrane

29

Gradients involved in the Gibbs-Donnan Equation

1. Competing electrical and concentration gradients --> At Equilibrium --> Side with proteins is More negatively charged --> creates voltage gradient
2. More osmotically active particles are on the protein side (greater osmolality) --> water flow to the protein side (oncotic pressure)
3. Cells need to balance osmotic pressures across their membranes otherwise they'll burst --> Solution: Pump osmotically active ions (Na+) out using the Na+/K+ ATPase transporter
4. Creates 2x Opposing Donn and Gibb equilibriums, BOTh of which H2O is a part of (High Na vs High K& High Protein) --> Balanced water movement equal across membranes
5. Intracellular movement slows and ECF becomes isotonic --> ICF and ECF compartments have identical osmolality (300mOsmol/kg), regardless of having different compositions

30

Osmolarity b/w bodily compartments

Despite differences in composition, the ICF and ECF compartments have identical osmolality (300mOsmol/kg)
Inside cell: lots of K and charged protein
Outside cell: lots of Na
- All due to Na/K ATPase
Note: plasma is similar to interstitium, except greater amount of protein (albumin/immune complexes) being pushed around

31

Hypotonic ECF osmolality

Decreased Na concentration outside of cells --> Relatively greater Na concentration of osmotically active particles inside of cells --> Water moves via osmosis into cell --> cells swell --> try to return to equilibrium --> (If swell excessively --> burst --> Death)
Note: swollen brain = painful
Remove water from ECF to dilute
e.g. Excessive water consumption --> body needs to remove the H2O in order to concentrate the NA --> maintains isotonic environment

32

What are concentration gradients referring to?

Relatively greater number of osmotically active particles
Water movement occurs to try and reach equilibrium again/ isotonic environment

33

Hypertonic ECF osmolality

Increased Na concentration outside of cells --> Relatively smaller Na concentration of osmotically active particles inside of cells --> Water moves via osmosis out of cell into ECF --> cells shrink --> try to return to equilibrium --> (If shrink excessively --> Death)
Note: shrunk brain = painful
Add water to ECF to dilute

34

Control of ECF Osmolality

ECF osmolality control is critical for cell survival --> tightly controlled --> varies 1-2%
ECF osmolality (salt concentration) is largely regulated by altering water levels --> more rapid response to water levels > salt levels

35

How is the Tight control of ECF osmolality regulated?

Altering water levels
--> as ECF volumes (H2O content) is primarily dependant on the amount of Na --> as Na is the most osmotically active solute in the ECF
--> results in ECF volume levels being less tightly controlled (more dynamic range of 15% regulation)

36

Maintenance of compartment sizes

1. Kidney: major regulator of water and salt homeostasis (i.e. ECF osmolality and volume)
2. Starling Forces:
- change in plasma protein levels --> change in oncotic pressure -- change in starling forces

37

Oedema

Causes: Inflammation, Obstruction (lymphatic or venous), sodium retention, Low serum albumin
--> Changes in charged/osmotically active plasma protein levels --> change in starling forces in plasma --> fluid movement into the interstitial space --> Abnormal expansion of the interstitial fluid compartment
Can be localised or general

38

Balance b/w daily intake and output for an adult at room temperature

What goes in (salt and water) = Has to come out
Water intake: Total: 2.5L
1. Drinking 1.2L
2. In Food 1L
3. Metabolism 300mL
Water Out-take: Total 2.5 L
1. Insensible 700mL
2. Sweat 100mL
3. Faeces 200mL
4. URINE 1.5L = MAJORITY URINE AND SALT OUTPUT of the body

39

Role of urine

Urine = largest components of the balanced 2.5L daily water outake = 1.5L = as urine contains the majority of urine and salt output of the body
Urine ouput and urine Osmolality VARIES --> in order to balance water and salt levels
--> allows water intake to be completely balanced by water output
Note: if water intake isnt balanced by water output --> expansion --> change in osmolality outside of 1-2% tightly regulated range --> need dialysis