Week 6 - Fluid And Electrolytes/Urinary System Flashcards
Functions of water
- acts as a solvent, allowing electrolytes to ionise
- is a reagent in many chemical reactions
- acts as a transport medium (eg blood)
- is a lubricant (eg synovial fluid and mucus)
What are the two major fluid compartments in the body?
- intracellular fluid
- extracellular fluid
Where is the intracellular fluid located in the body and what fraction is it in regards to the body’s fluid?
- located inside the cells (cytosol)
- 2/3 of the bodies fluid
Where is extracellular fluid located in the body, and what fraction is it in regards to the body fluids?
- located outside of the cell
- 1/3 of the bodies fluid
What type of fluid is plasma? And what is it known as?
Type of extracellular fluid, known as the third fluid compartment
Name some sources of fluid input
- food and drink
- produced by cells
Name some Sources of fluid output
- kidneys as urine
- lungs with expired air
- skin by diffusion and by sweat
- intestines as faeces
What happens if the body has excess water in it?
- excess water in the body causes over-hydration, and cells start to overfill
What happens if the cells start to overfill due to the excess water and over hydration?
- causes increased workload of the heart and shortness of breath (SOB)
- may cause swelling of the neurons in the brain due to hyponatraemia
What happens if the body doesn’t have enough water (has insufficient water)
The body causes dehydration, and a drop in blood volume (therefore drop in blood pressure)
What happens when the body is in dehydration and there is a drop in blood volume?
- can cause decreased renal function and a decreased tissue perfusion
Describe the fluid movement
- water, other nutrients and waste products move from capillaries to interstitial spaces as a result of hydrostatic pressure - ‘pushing’
- water moves from the interstitial space into cells primarily as a result of osmosis - ‘pulling’
- proteins such as albumin play a large part in the osmotic “pull” of fluids and in the blood stream
Define osmolarity
Total solute concentration in a solution
Define Tonicity
Describes how the solution affects the cell
What is an isotonic solution?
Solutes and water in fluid and cells are equal
- cells retain their size and shape
- same osmolarity of blood plasma
- if RBC are in isotonic solution, water molecules move in and out of the cell at the same rate
What is a hypertonic solution?
Solutions have in too many solutes and therefore greater water loss from cells
- higher osmolarity than the cytosol of body cells
- if RBC are in hypertonic solution, water molecules move out of the cell faster than they enter
- cells shrink in size (crenation)
What is a hypotonic solution?
Solutions have less solutes than cells, therefore water moves into the cells
- lower osmolarity than the cytosol of body cells
- if RBC are in hypotonic solution water molecules move into the cell faster than they exit
- cells increase in size and can burst (haemolysis)
What fluid is the most prevalent in extracellular compartments?
Sodium (Na)
What fluid is most prevalent in intracellular compartments?
Potassium (K)
Define electrolytes
A substance which forms ions in a water solution
What is the chemical equation for electrolytes in water?
NaCl —> Na+ + Cl-
What happens when you manipulate electrolyte concentration?
We can alter the movement of bodily fluids via osmosis
What are electrolytes?
A tool to control the movement of fluids between the fluid compartments
When does dehydration happen?
It occurs when water loss is greater than waiter gain, therefore is a decrease in volume and an increase in osmolarity of body fluids
What does dehydration stimulate?
The production of aldosterone via the renin-angiotensin-aldosterone (RAA) pathway
What detects the increase of osmolarity?
By the thirst centre in the hypothalamus which triggers the urge to drink
What is the main way to regulate body water balance?
Adjusting the volume of water intake
What three hormones regulate fluid loss? (Via the kidneys)
- atrial natriuretic peptide (ANP)
- antidiuretic hormone (ADH)
- Aldosterone
How does the body regulate loss of body water or excess solutes?
By regulating how much water and solutes are lost in the urine
What happens during exercise to fluid loss?
Increases amounts of water and solutes are lost through sweating and exhalation
What does sodium retention cause?
Water retention
- Oedema is the abnormal accumulation of interstitial fluid
What are the causes of sodium retention?
- Renal failure
- hyperaldosteronism
What happens when there is excessive loss of sodium?
Causes excessive loss of water (low blood volume)
- due to inadequate secretion of aldosterone
- high dose of diuretic meds or wrong type of diuretic
What are three examples of extracellular fluid?
- serous fluid
- endolymph
- perilymph
What is the lymphatic system?
A component of the circulatory system
Where does the lymphatic system run alongside?
Runs alongside the venous blood vessels
- contains clear fluid called lymph
What is lymph made of?
- water
- white blood cells
- large proteins
- fats
When does the lymphatic system re-join the venous system?
Before the blood reaches the right atrium
What is the function of the lymphatic system?
- includes an immune system (destroys microbes and cancerous/foreign cells)
- drain (excess interstitial fluid from tissue spaces & return it to the venous blood supply, maintaining fluid balance)
- transport (lipids and liquid soluble vitamins from the vili in the small intestine to the blood)
True or false: the lymphatic capillaries are high-pressure vessels widespread in connective tissues?
False
True or false: the lymphatic capillaries deliver nutrient rich fluid to the tissue
False
True or false: the lymphatic capillaries have rightly connected cells which prevent the movement of fluid into or out of the lymph capillary
False
True or false: the lymphatic capillaries drain excess interstitial fluid containing small proteins, cellular debris, pathogens and cancer cells
True
What are 4 factors that can impact the flow of lymph through lymphatic vessels?
- rate of lymph formation
- gravity
- valves prevent back flow of lymph
- respiratory pump helps to draw lymph upwards in side vessels
Define interstitial fluid
Fluid between cells
What causes the water from plasma to move from the arterial end of the capillary to the venous end of the capillary?
- hydrostatic pressure pushes water component of plasma through pores in the thin-walled capillary
- blood pressure causes fluid to move by filtration
What causes interstitial fluid to return to the Venus end of the capillary?
Hypertonic solution generated in the venous end when water moves out of the arterial end. This hypertonic solution (containing Albumin and other proteins) causes water to be pulled back into the venous end
How does interstitial fluid become lymph?
- Water moves from the interstitial space into the lymph vessels down a pressure gradient
- Overlapping cells of lymph vessels prevent fluid moving back into interstitial space
Define oedema
The presence of abnormally large amounts of fluid in the intercellular tissue spaces of the body
How do you reduce oedema in a limb?
Gravity facilities drainage of excess interstitial fluid through the lymphatic system allowing fluid to rejoin the venous circulation
Three locations where oedema is more likely to occur
- lungs
- brain
- gravity dependent areas such as limbs and lower back
What is Albumin?
A protein that helps to regulate oncotic pressure in the vascular system
What as the components of the lymphatic system?
Comprised of:
- lymph
- lymph vessels
- lymph nodes
- lymph organs (spleen, thymus)
- includes lymphoid tissue such as the tonsils
- includes bone marrow
Two age-related changes to the urinary bladder
- urinary retention from prostate enlargement obstructing flow of urine in males
- decreased elasticity (reduced compliance) of bladder wall prevents the bladder from holding as much urine leading to more frequent urination
What is the superior surface and part of the posterior surface of the bladder covered by?
The peritoneum
What does the peritoneum provide?
It provides support and a pathway for blood and lymphatic vessels
What is the micturition reflex?
Describes the mechanism by which urine is expelled from the bladder (emptying the bladder)
- it requires a combination of voluntary and involuntary muscle contractions
• stretch receptors in the bladder wall send signals to the micturition centre in the sacral spinal cord - in early childhood, we learn to initiate and stop the reflex voluntarily
What are the two regions of the kidneys called?
- the cortex
- the medulla
Structure of the cortex
- outer component of the kidney
- renal columns contain blood vessels and fibrous tissue to anchor the cortex
Structure of the medulla
- inner component of the kidney
- contains renal pyramids: these contain microscopic collecting tubules and blood capillaries
- renal pelvis is the funnel shaped area connecting to the ureter
The helium is the entrance for the…
- renal artery
- renal vein
- ureter
- nerves
- lymphatics
Explain the renal blood supply
- oxygenated blood enters each kidney via a renal artery
• the renal arteries are large branches of the additional aorta - deoxygenated blood exits each kidney via a renal vein
What are the three ways urine moves from the kidney to the bladder?
- Peristaltic contractions
- Hydrostatic pressure
- Gravity
What do the ureters carry?
Carey urine from the kidneys to the bladder (primarily by peristalsis, but hydrostatic pressure and gravity also help)
How is urinary back flow from the bladder up the ureters prevented?
- pressure exerted on the ureters as the bladder fills up with urine
- one-way valve between each ureter and bladder
What is the average capacity of urinary bladder?
700-800mls
What are the three layers to the urinary bladder?
- inner mucosa of transitional epithelium - middle smooth muscle coat (detrusor muscle)
- outer adventitia
What is the urethra
The passageway for urine to exit the body
What type of tissues does the urethra have?
- mucous membrane
- muscularis layer (circular smooth muscle)
How long is the urethra?
Approx. 4cm long in women (five times longer in males)
What in the involuntary pathway of micturition? (Stimulus, pathway, effector)
STIMULUS::
- stretch receptor of bladder wall activated by filling of urine
PATHWAY::
- sensory Neurons carry action potential to sacral spinal cord (S2- S4)
- motor nerves carry action potentials from spinal cord to bladder
EFFECTOR::
- detrusor muscle contracts
- internal urethral relaxes
- urination occurs
What is the Voluntary pathway of micturition (stimulus, pathway, effector)
STIMULUS::
- stretch receptors of bladder wall activated by filling of urine
PATHWAY::
- sensory neurons carry action potential to sacral spinal cord (S2-S4) and on to the cerebral cortex to create the urge to urinate
- motor nerves carry action potentials from cerebral cortex and spinal cord to bladder
EFFECTOR::
- detrusor muscle contracts and internal sphincter relaxes BUT External sphincter constricts to consciously prevent urination
- urination is prevented until a conscious decision is made to urinate
- motor impulses continue to increase to detrusor and internal sphincter, and motor impulses decrease to external sphincter
- urination occurs
What is Incontinence?
A lack of voluntary control over micturition (urinating)
What are the different types of inconsistence?
- functional incontinence
- nocturnal enuresis
- post -micturition dribble
- stress-incontinence
- urge incontinence
What is functional incontinence?
Impaired mobility, dexterity and cognition causes a person to become unable to use a toilet
What is nocturnal enuresis?
Involuntary loss of micturition control during sleep
What is post-micturition dribble?
Leakage of urine following voiding (common in older men)
What is stress-incontinence?
- involuntary leakage of urine during exertion, laughing, sneezing
- common in pregnancy, obesity and older men post-prostate surgery
What is urge incontinence?
Involuntary leakage of urine accompanied by or immediately preceding urgency
