5400025
Description
Flashcards by Jonathan Cash, updated more than 1 year ago
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Created by Jonathan Cash
over 8 years ago
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| Question | Answer |
| Gender Water % Solute & Solvent | Men are 60% water. Women 50% water Solution = Solute + solvent Solvent is water, Solute is the substances dissolved in it |
| Intracellular Fluid (ICF) % Made of Location | 65% of water is inside cells (ICF) Cytosol The amount of water inside cells varies Much is in muscle cells but almost none in fat |
| Extracellular Fluid (ECF) % 2 compartments and % Internal and external link | 35% of body water is outside cells (ECF) Divided into 2 compartments: Interstitial (extra-vascular or tissue fluid) Intra-vascular (plasma) Of the 35% ECF, 23-28% is interstitial and 7-10% is in plasma Intra-vascular links the internal and external environments |
| Extracellular Fluid (ECF) Changes Movement Gained and Lost | 1/6 ECF changes daily 2500mL day enters the ECF 2.5L day is gained & 2.5L lost It moves into the circulation -> blood capillary tissues -> blood capillary -> exits out of the body |
| Fluid Movement Forces moving between ECF and ICF Intravascular and Interstitial | One force moves water between ECF and ICF: - Osmotic pressure Two forces move water between intravascular and interstitial: - Hydrostatic pressure creating filtration pressure - Osmotic pressure - Hydrostatic pressure creates interstitial fluid from plasma |
| Hydrostatic pressure | Force exerted by fluid pressing against a wall. Creating filtration pressure. Created by blood pressure. The capillary wall is leaky, so fluid is forced out. |
| Capillaries = site of filtration | - Narrow - wide enough for one red blood cell. - Leaky - Flow is slow - Beds be flooded or bypassed - Destination of transported substances |
| Filtration | - Hydrostatic pressure will force water with solutes through capillary walls. - If the water moves through a membrane, the solutes may or may not be able to move through also. - Blood cells, platelets & most proteins are too large to leave the blood vessel. - Solutes move by diffusion. |
| Capillary bed Consist of | - Vascular shunt and - True capillaries = the actual exchange vessels |
| Vascular Shunt | Sphincters closes (sympathetic stimulation) Blood flows straight through metarteriole thoroughfare channel and bypasses true capillaries 'shunting' blood away from this area of tissue |
| Structure of capillaries | - A single layer of endothelial cells (squamous) on a basement membrane. - The basement membrane creates a mechanical barrier. - Pericytes embedded in the membrane regulate flow and permeability. Structure determines permeability & type: 1. continuous 2. fenestrated 3. sinusoidal. |
| The capillary wall is crossed by; | Clefts Fenestrations (Pores) Vesicles |
| Structure of capillaries – Continuous capillaries | - the most common type. - very smooth. - cells are joined by tight junctions. - Gaps between the cells = clefts for exchange of substances between blood, interstitial fluid. |
| Continuous capillaries & the Blood Brain Barrier | - The least leaky capillaries - Brain capillaries have been modified to protect the brain (blood brain barrier) - They have continuous tight junctions and ion pumps that ensure that these capillaries are very selective. - Give the brain protection from some substances in the blood. - The hypothalamus and vomiting centre of the medulla do not have a blood brain barrier. |
| Blood brain barrier Able to pass | O2, CO2 Glucose Essential amino acids Some electrolytes Lipid based substances Alcohol, nicotine, anaesthetics |
| Blood brain barrier unable to pass | Metabolic wastes Proteins Toxins Most drugs small non essential amino acids potassium ions. |
| Structure of capillaries - Fenestrated capillaries | - Endothelial cells joined by tight junctions - cells contain pores - very permeable - allow active filtration or re-absorption - located in small intestine, endocrine organs and kidneys. |
| Fenestrated capillaries | = choroid plexuses in the brain ventricles to make CSF. |
| Structure of capillaries - Sinusoidal capillaries | Most leaky large, irregular shaped lumen slow blood flow located in red bone marrow, liver, spleen. allow easy movement of substances |
| Hydrostatic pressure pushes fluid through capillary walls to make | - Synovial fluid - aqueous humor of the eye - Interstitial fluid (tissue fluid) - CSF - Serous fluid |
| hydrostatic pressure | - The HP in the tissue fluid (HPif) is almost zero mmHg - HPc is 35 mmHg at arteriolar end of a capillary and - HPc reduces to 17 mmHg at venule end of a capillary - HPc is pushing fluid along and OUT of the leaky capillaries |
| Osmosis | - Always movement of Water - Water will move from one side of a semi permeable membrane to the other side when: 1.There is a difference in solute concentration on two sides of a semi permeable membrane 2. And the solutes cant move through that membrane |
| Osmosis; definitions | - Movement of water from hypotonic to hypertonic - Water moves from area of high water to an area of low water - Water moves from area of low solute to high solute Through a semi-permeable membrane |
| Tonicity Isotonic Hypertonic Hypotonic | A way of comparing the concentration 2 solutions Isotonic: the same concentration - No osmosis occurs - Isotonic saline = normal saline = 0.9% NaCl & is isotonic with ECF Hypertonic: solution has a higher concentration of solutes Hypotonic: Solution has a lower solute concentration |
| Osmotic pressure | - Osmotic gradients are created when there is a difference in solute concentration. - Electrolytes are solutes important at the cell - But osmotic gradients can be caused by other substances such as glucose or proteins - Oncotic pressure is osmotic pressure created by proteins and is important at the capillary |
| Osmotic pressure cont. Definition | Definition: Pressure required to stop movement of pure water through a semipermeable membrane into a solution Or The greater the concentration difference, the greater the osmotic pressure |
| How hydrostatic & osmotic pressures cause fluids to shift Blood Interstitial | - blood hydrostatic pressure pushes fluid out - blood osmotic pressure pulls fluid in - interstitial fluid hydrostatic pressure pushes fluid in - interstitial fluid osmotic pressure pulls fluid out |
| ECF Fluid movement summary | - Hydrostatic pressure in capillaries is created by the heart (BP) & the weight of fluid - It forces fluid out of capillaries - Capillary osmotic pressure is created by the plasma proteins - It sucks fluid back into capillaries - 85% fluid that leaves capillaries gets sucked back - Any fluid not sucked back into the capillaries enters the lymphatic system |
| How hydrostatic & osmotic pressures cause fluids to shift | - 20L/day fluid pushed out of capillaries by HPc - How does this fluid get inside the cells? - ECF & ICF are osmotically equal - If they are not, osmosis moves the fluid in or out of cells - Hydrostatic pressure has no effect on the cell. |
| Adding & loosing water | - The amount of water and osmolality of any one compartment, affects the others. - Adding water to a compartment lowers the concentration & thus the osmotic pressure - Removing water from a compartment increases the concentration & thus the osmotic pressure |
| Total body water | - Is monitored by osmoreceptors - In the hypothalamus - If water level drops → osmolarity increase. Feedback mechanisms restore levels to normal - Water level may drop due to dehydration, bleeding, sweating, vomiting & diarrhoea, evaporation from respiratory surfaces, - Osmolarity may increase because water level drops or salt intake increases |
| 1L of water moves into all compartments | All fluid compartments increase in volume in proportion Normal ICF 65%; ECF 35%; Intra vascular = 7% & interstitial = 28%. 65% into cells = 650 mL divided amongst 10 000 trillion cells 35% as EFC = 350mL 70mL into plasma (Volume excess) & 280 mL into interstitial space (edema) All fluid compartments will decrease concentration |
| 1L of water moves into all compartments Symptoms | Brain cells can swell & impaired headaches, nausea, convulsions, coma & death Blood volume increases, BP increases, ANP released, renin suppressed, Hypothalamus trigger ADH & thirst suppression. |
| Homeostatic fluid control | - ICF: Cells will swell or shrink as fluid shifts in or out from interstitial compartment - ECF: Increase or decreased blood volume regulated by hormonal controls. - Decreased volume: ADH, thirst & if accompanied by reduced BP, Renin - Increased volume: ANP - Increased tonicity: same as decreased volume - Decreased tonicity: Aldosterone |
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