What is this ??? Use question grid to think of some questions When? Where? Which? Who? Why? How? Is Did Can Would Will Might

Essentially ….. But longitudinal section not a cross section

Learning Outcomes Identify the structure of the capillary (extra material for arteries and veins) Compare and contrast vasodilation and constriction Identify what the tissue fluid is made up of Explain how it is made and the return to the bloodstream

Four parts in arteries and veins: central lumen blood flows through here much smaller in arteries tunica intema (inner layer) made of endothelium cells, lines the lumen and reduces friction as the blood flows through the vessel   tunica media (middle layer) middle layer of smooth muscle cells, collagen and elastic fibres much more strong and thick in arteries, allowing them to stretch and recoil to accommodate the surge of blood after each contraction of the heart (creates the pulse)

Four parts in arteries and veins: tunica media (middle layer) middle layer of smooth muscle cells, collagen and elastic fibres much more strong and thick in arteries, allowing them to stretch and recoil to accommodate the surge of blood after each contraction of the heart (creates the pulse) smooth muscle can contract or relax, causing vasoconstriction or vasodilation to control blood flow.   tunica externa (outer layer) outer layer consisting of collagen fibres and some elastin fibres.

Vasoconstriction and vasodilation Change due to demands on the body Smooth muscle in artery can contract or relax, causing vasoconstriction or vasodilation to control blood flow. For example if you are doing exercise your muscles will be using up more oxygen – a greater blood supply will be able to meet this demand by ARTERIOLES becoming DILATED. But same volume of blood – so they need to become constricted somewhere else ..... The intestines Hence the rule “don’t go swimming straight after eating a meal – wait 2 hours!”

Capillaries Steady flow of blood by time reaches small arteries/arterioles and capillaries Substances exchanged in capillaries between cells and blood

Capillary Beds Networks of capillaries very dense, so close that every living cell is located close to a capillary This closeness and numerous capillaries are also important in terms of the exchange of materials between blood and cells. So what is exactly in the blood? What is it made up of?

Blood ..... 3 main parts ; red blood cells (carry O2 and some CO2), white blood cells (next unit we will study unit 4, fights foreign bodies) and plasma including platelets (needed for clotting). Plasma is a yellow watery substance that is mainly made up of water and contains many dissolved substances such as glucose, amino acids, respiratory gases (mainly CO2) plasma proteins and useful ions (electrolytes).

Under Pressure .... Blood is at high pressure arriving from the arterioles to the capillaries. This pressure difference causes much of the plasma in the blood to be forced through thin walls – and is called tissue fluid – process called PRESSURE FILTRATION What do you think will be in the tissue fluid?

Same except very exception of plasma proteins Pressure Filtration Blood Plasma Tissue Fluid (interstitial) Dissolved gases Glucose Amino acids Useful Ions Hormones Plasma proteins (fibrinogen / albumin etc.) Dissolved gases Glucose Amino acids Useful Ions Hormones Plasma proteins (fibrinogen / albumin etc.) Same except very exception of plasma proteins

Diffusion High concentration to a low concentration Soluble food molecules (glucose/amino acids), dissolved oxygen and useful ions diffuse down a concentration gradient into nearby cells. The cells diffuse out carbon dioxide, metabolic waste substances (such as urea) into the tissue fluid ready for excretion (MRS GREN)

Osmosis ..... Tissue fluid has a high water concentration (no proteins) Blood plasma has a low water concentration (mainly proteins) Thus by osmosis; much of the tissue fluid returns. Some of the tissue fluid does not ....

Tissue Fluid Excess Excess tissue fluid is absorbed by thin walled lymphatic vessels which are found in connective tissue. When the tissue fluid enters the lymphatic vessel it is termed “lymph”

Lymphatic System No pump like the heart – so movement in vessels by surrounding muscles contracting in breathing/moving causing compression in these vessels. Vessels join into 2 lymphatic ducts which enter vein in arm.

Lymphatic System Blind ended tubes (closed at one end) Valves prevent backflow of lymph in larger vessels Specialised part of the cardiovascular system mainly as made from blood fluid and returns to the bloodstream.

Demonstrate – when things go wrong! Odema – tissue fluid accumulates in in the space between cells and blood vessels. Causes swelling 3 main causes ; malnutrition, blood pressure and parasites

High blood pressure Think about how this will system will be affected .... More arrows into tissue fluid, so more being made than drained away by lymphatic system so acculumates

Osmosis due to proteins Malnutrition Dietary deficiency can cause insufficient protein being taken in by the body Think about pressure filtration and what a lack of plasma proteins could cause ..... Pressure from heart Little/ no fluid returned, lymph not cope with extra, so gathers in abdomen, kwashiorkor Pressure from heart Osmosis due to proteins

Parasites - Elephantiasis Parasitic worm enters lymph system – when they mature they block lymph vessels, especially the leg lymph vessels. So what does that mean for excess fluid? Build up in neighbouring tissue Excessive growth of infected area

Loop Da Loop

Review – Test Your Knowledge Give two structural difference between an artery and a vein Give one functional difference between an artery and a vein What is tissue fluid? Name a substance that passes from body cells into tissue fluid Briefly describe two methods by which tissue fluid returns to the bloodstream Briefly describe the means by which lymph in a lymph vessel is forced along the lymphatic system What structures prevent backflow of lymph? Which structures enable lymph to return to the blood circulatory system?

Review – Test Your Knowledge ANSWERS Thin muscular walls in vein, thick muscular walls in artery, valves in veins, not arteries. Veins towards heart, arteries away from heart (not deoxygenated due to pulmonary) Liquid from pressure filtration in capillary, mainly made of plasma dissolved molecules/gases – NOT proteins Carbon dioxide, urea Back to blood capillary via osmosis (protein causes concentration difference) or absorbed into thin walled lymphatic vessels, into lymph, which joins at ducts to bloodstream Periodic pressure when surrounding muscles are contracting causes lymph to be pushed along vessel Valves Two lymphatic ducts

Tissue Fluid

Tissue Fluid What is the role of tissue fluid? It is the fluid which allows the exchange of substances between the blood and cells What substances are found in tissue fluid? glucose, amino acids, fatty acids, salts and oxygen = all delivered to the cells. carbon dioxide and other waste substances = removed from the cells.

Hydrostatic pressure

Hydrostatic Pressure As the capillaries are narrower than the arterioles, a pressure builds up which forces tissue fluid out of the blood plasma = hydrostatic pressure. This pressure is resisted by: Pressure of the tissue fluid on the capillaries (from the outside) The lower water potential of the blood (caused by plasma proteins – too large to leave the blood) Overall, pressure pushes tissue fluid and small molecules out of the capillary, leaving cells and large proteins behind = ultrafiltration.