AQA · A-Level · Biology

    Course version: 7402 · Version from Sept 2016

    The structure of arteries, arterioles and veins in relation to their…

    Full specification wording

    Mass transport in animals: The structure of arteries, arterioles and veins in relation to their function.

    All three vessel types share an inner endothelium, a middle layer of smooth muscle and elastic tissue, and an outer collagen coat, but the proportions differ with function.

    Checked against the AQA 7402 specification (opens in a new tab) on .

    • Point 11 of 14
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    All three vessel types share an inner endothelium, a middle layer of smooth muscle and elastic tissue, and an outer collagen coat, but the proportions differ with function. Arteries carry blood at high pressure away from the heart, so they have thick walls with much elastic tissue: it stretches as blood is forced in during ventricular systole and recoils during diastole, smoothing flow into a continuous stream and maintaining pressure between beats. A narrow lumen relative to wall thickness keeps pressure high. Arterioles have proportionally more smooth muscle, which contracts to narrow the lumen, controlling blood distribution between organs by vasoconstriction and vasodilation. Veins carry blood at low pressure back to the heart, so they have a wide lumen, a thin wall with little elastic tissue and less smooth muscle, and valves that prevent backflow.

    What earns the marks

    • A thick artery wall containing elastic tissue enabling the vessel to withstand and maintain high pressure.
    • Elastic recoil of the artery wall smoothing out the pulse and maintaining flow during diastole.
    • Smooth muscle in arterioles contracting to narrow the lumen and redirect blood flow.
    • A vein having a wide lumen and valves to prevent backflow of low pressure blood.
    • A vein having a thin wall with little elastic tissue because the blood it carries is at low pressure.

    Common mistakes and how to put them right

    • Writing thick muscular walls for arteries when the mark is for elastic tissue and pressure.

    • Saying veins have valves because blood moves slowly, without mentioning backflow or low pressure.

    • Confusing the lumen with the wall, so a vein is described as having a narrow lumen.

    • Claiming arteries contain valves, or that arterioles contain no muscle.

    • Listing a structure with no function attached, which scores nothing in an in relation to their function question.

    Exam tips

    • Write every point as structure, then because, then function, in one sentence.
    • Use the word lumen, and say relative to the wall thickness when you compare vessels.
    • Remember it is the arterioles, not the arteries, that control the distribution of blood between organs.

    Try the lesson

    The start of the Mass transport in animals: The structure of arteries, arterioles and veins in relation to their function. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which structural feature of an artery is directly responsible for withstanding the high pressure of blood leaving the heart?

    Listen

    All three vessel types share an inner endothelium, a middle layer of smooth muscle and elastic tissue, and an outer collagen coat, but the proportions differ with function. Arteries carry blood at high pressure away from the heart, so they have thick walls with much elastic tissue: it stretches as blood is forced in during ventricular systole and recoils during diastole, smoothing flow into a continuous stream and maintaining pressure between beats. A narrow lumen relative to wall thickness keeps pressure high. Arterioles have proportionally more smooth muscle, which contracts to narrow the lumen, controlling blood distribution between organs by vasoconstriction and vasodilation. Veins carry blood at low pressure back to the heart, so they have a wide lumen, a thin wall with little elastic tissue and less smooth muscle, and valves that prevent backflow. A strong answer earns marks for these points. a thick artery wall containing elastic tissue enabling the vessel to withstand and maintain high pressure. elastic recoil of the artery wall smoothing out the pulse and maintaining flow during diastole. smooth muscle in arterioles contracting to narrow the lumen and redirect blood flow. a vein having a wide lumen and valves to prevent backflow of low pressure blood. Exam tip: Write every point as structure, then because, then function, in one sentence.

    See it

    A top-down flowchart with three branches. The first branch starts at a node labelled Artery: thick wall, much elastic tissue, which leads to Stretches during ventricular systole, then to Recoils during diastole, then to Smooths flow into a continuous stream and maintains pressure between beats. A second node from the artery, Narrow lumen relative to wall thickness keeps pressure high, sits alongside. The second branch starts at Arteriole: proportionally more smooth muscle, leading to Smooth muscle contracts to narrow the lumen, then to Controls blood distribution between organs by vasoconstriction and vasodilation. The third branch starts at Vein: wide lumen, thin wall, little elastic tissue, less smooth muscle, leading to Valves prevent backflow of low pressure blood.
    How the differing proportions of elastic tissue, smooth muscle and lumen width in arteries, arterioles and veins relate to their functions.

    Key words

    Say what each word means before you turn the card.

    elastic recoil

    Try answering aloud or in your head before turning the card.

    high and low pressure vessels

    Try answering aloud or in your head before turning the card.

    lumen diameter

    Try answering aloud or in your head before turning the card.

    smooth muscle and vasoconstriction

    Try answering aloud or in your head before turning the card.

    See every definition
    elastic recoil
    The elastic tissue in an artery wall stretches as blood is forced in during ventricular systole and recoils during diastole, smoothing flow into a continuous stream and maintaining pressure between beats.
    high and low pressure vessels
    Arteries carry blood at high pressure away from the heart, while veins carry blood at low pressure back to the heart.
    lumen diameter
    A narrow lumen relative to wall thickness keeps pressure high, whereas a vein has a wide lumen.
    smooth muscle and vasoconstriction
    Arterioles have proportionally more smooth muscle, which contracts to narrow the lumen, controlling blood distribution between organs by vasoconstriction and vasodilation.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart with three branches. The first branch starts at a node labelled Artery: thick wall, much elastic tissue, which leads to Stretches during ventricular systole, then to Recoils during diastole, then to Smooths flow into a continuous stream and maintains pressure between beats. A second node from the artery, Narrow lumen relative to wall thickness keeps pressure high, sits alongside. The second branch starts at Arteriole: proportionally more smooth muscle, leading to Smooth muscle contracts to narrow the lumen, then to Controls blood distribution between organs by vasoconstriction and vasodilation. The third branch starts at Vein: wide lumen, thin wall, little elastic tissue, less smooth muscle, leading to Valves prevent backflow of low pressure blood.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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