What’s the Question? Come up with some questions where the key words below are the answers: Open circulatory system Blood vessels Body cavity Ostia Low pressure Tissue fluid Lumen Endothelium Elastic fibres Smooth muscle Collagen fibres High pressure
Regular exercise and a balanced diet are needed to keep the body healthy. Too little food leads to a person being underweight and prone to certain types of illness, while too much food and not enough exercise leads to a person being overweight and other types of ill health.NutrientsA mixture of different types of food in the correct amounts is needed to maintain health.The main food groups are carbohydrates, fats and proteins.This table summarises some typical sources of these nutrients and why our bodies need them.The main food groupsFood group Found in Needed by our bodies for:Carbohydratespotato, banana, pastapotatoes, pasta, bread, bananas, sugar and rice a source of energy for life processesFatscheesecheese, butter, margarine and oils a source of energy for life processes: fats are also needed to make cell membranes and to insulate our bodiesProteinsmeatmeat, fish, eggs and cheese growth and repair - building cellsMineral ions and vitamins are also important in a healthy diet. They are needed in small amounts for healthy functioning of the body.Imbalanced dietsAn imbalanced diet causes a person to become malnourished. For example:too little food may lead to a person being underweighttoo much food may lead to a person being overweight.A poor diet may also lead to deficiency diseases. For example, too little vitamin D in the diet can lead to rickets, which affects the proper growth of the skeleton. Type 2 diabetes is also a problem related to poor diet. Note that you do not need to know how the nutrients work or the effects of any particular deficiency in the diet for your exam.Regular exercise and a balanced diet are needed to keep the body healthy. Too little food leads to a person being underweight and prone to certain types of illness, while too much food and not enough exercise leads to a person being overweight and other types of ill health.NutrientsA mixture of different types of food in the correct amounts is needed to maintain health.The main food groups are carbohydrates, fats and proteins.This table summarises some typical sources of these nutrients and why our bodies need them.The main food groupsFood group Found in Needed by our bodies for:Carbohydratespotato, banana, pastapotatoes, pasta, bread, bananas, sugar and rice a source of energy for life processesFatscheesecheese, butter, margarine and oils a source of energy for life processes: fats are also needed to make cell membranes and to insulate our bodiesProteinsmeatmeat, fish, eggs and cheese growth and repair - building cellsMineral ions and vitamins are also important in a healthy diet. They are needed in small amounts for healthy functioning of the body.Imbalanced dietsAn imbalanced diet causes a person to become malnourished. For example:too little food may lead to a person being underweighttoo much food may lead to a person being overweight.A poor diet may also lead to deficiency diseases. For example, too little vitamin D in the diet can lead to rickets, which affects the proper growth of the skeleton. Type 2 diabetes is also a problem related to poor diet. Note that you do not need to know how the nutrients work or the effects of any particular deficiency in the diet for your exam.
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Whats the Question?Come up with some questions where the key
words below are the answers:Open circulatory systemBlood
vesselsBody cavityOstiaLow pressureTissue
fluidLumenEndotheliumElastic fibresSmooth muscleCollagen fibresHigh
pressure
Blood, Tissue Fluid and Lymph
By the end of the lesson you will be able to: Explain the
differences between blood, tissue fluid and lymph. (E)Describe how
tissue fluid is formed from plasma. (C)Explain how effective blood
pressure determines the direction of fluid movement. (A)
Key definitionBlood is the liquid held in our arteries, veins
& heart. Tissue fluid bathes the cells of individual
tissuesLymph is held within the lymphatic system
Blood composition
Plasma -55%RBC-40%WBC-5%
Tissue fluidBathes the cells of a tissue (hence the
name!)Similar to blood (plasma) but without the cells or plasma
proteins.Its job is to transport oxygen and nutrients to the cells
from the blood and carbon dioxide and other wastes back to the
blood from the cells.
Artery linked to a vein by acapillary bed
How is tissue fluid formed?Blood flows into a capillary in an
organThe blood is under high pressure at the arteriole end of the
capillary bedThis is hydrostatic pressureThis tends to push the
blood fluid out of the capillaries through tiny gaps in the wallThe
fluid consists of plasma with dissolved oxygen and nutrientsRBC
& WBC are too large to be pushed out-as are plasma
proteinsExchange of gases and nutrients takes place across plasma
membranes by diffusion or facilitated diffusion
Artery linked to a vein by acapillary bed
A single capillary showing the relative hydrostatic and osmotic
(water potential) forcesTherefore fluid pushed out of
capillaryEffective HP = 4.3 1.1 = 3.2kPaEffective SP = -3.3 (-1.3)=
-2kPaEffective blood pressure = 3.2 2 = 1.2kPaArteriole End Worked
Example
How does fluid return to the blood?The hydrostatic pressure of
the blood is not the only force acting on the fluid. The fluid
itself has some hydrostatic pressure.This tends to push the fluid
BACK into the capillaries.Both the blood and tissue fluid contain
solutes giving them a negative water potential.The water potential
of the tissue fluid is less negative than that of the
blood.Therefore water moves back into the blood from the fluid by
OSMOSIS.
Now calculate the effective blood pressure and direction of flow
for the venous end: Venous End Values (kPa): In capillary: HP = 1.6
SP = -3.3 In tissue fluid: HP = 1.1 SP = -1.3
A single capillary showing the relative hydrostatic and osmotic
(water potential) forcesTherefore fluid pushed into the
capillaryEffective HP = 1.6 1.1 = 0.5kPaEffective SP = -3.3 (-1.3)=
-2kPaEffective blood pressure = 0.5 2 = -1.5kPaVenous End Worked
Example
Formation of lymphNot all tissue fluid is returned to the blood
capillariesExcess fluid drains into the lymphatic systemEventually
the lymph rejoins the bloodIt is similar in composition but with
less oxygen and fewer nutrients, and fatty material that has been
absorbed from the intestinesLymph contains lymphocytes which are
produced at lymph nodes and which filter bacteria from the
fluidThis is part of our immune system which protects against
infection
