B3.2 Transport in Organisms
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Which of the following adaptations of capillaries directly facilitates rapid exchange of materials by diffusion?

  • Narrow lumen allowing single file red blood cell passage.
  • Large surface area due to branching.
  • Thick walls composed of multiple cell layers.
  • Thin walls that are typically one cell thick. (correct)

Arteries are characterized by thin walls and wide lumens compared to veins.

False (B)

Describe how the smooth muscle in artery walls helps maintain blood pressure.

Smooth muscle in artery walls can contract to adjust the diameter of the vessel, helping to regulate and maintain blood pressure between heartbeats.

The outer wall of an artery contains __________, which strengthens the artery to withstand high blood pressure.

<p>collagen</p> Signup and view all the answers

Match the blood vessel type with its structural adaptation:

<p>Artery = Thick walls to withstand high blood pressure Vein = Wide lumen to facilitate blood return to the heart Capillary = Thin walls for efficient diffusion</p> Signup and view all the answers

What is the primary function of capillaries in the circulatory system?

<p>To exchange materials between the blood and cells. (A)</p> Signup and view all the answers

How does the narrow lumen of a capillary aid in its function?

<p>It forces red blood cells to pass in single file, maximizing oxygen release. (B)</p> Signup and view all the answers

What structural feature of arteries enables them to maintain blood pressure between heartbeats?

<p>Both C and D. (D)</p> Signup and view all the answers

Which structural feature of arteries is most crucial for maintaining high blood pressure?

<p>Narrow lumen (C)</p> Signup and view all the answers

Arteries rely on valves to prevent the backflow of blood, ensuring unidirectional flow away from the heart.

<p>False (B)</p> Signup and view all the answers

Explain how the elastic fibres in the artery wall contribute to maintaining blood flow during the cardiac cycle.

<p>Elastic fibers allow arteries to stretch during systole and recoil during diastole, maintaining continuous blood flow.</p> Signup and view all the answers

To measure the pulse rate manually, one can use their fingertips to feel the pulse at the radial artery in the _____ or the carotid artery in the _____.

<p>wrist, neck</p> Signup and view all the answers

What is the primary adaptation of veins that facilitates the return of blood to the heart against gravity?

<p>Valves preventing backflow (B)</p> Signup and view all the answers

Skeletal muscle contraction aids in venous return by compressing veins, but this mechanism is ineffective without the presence of valves.

<p>True (A)</p> Signup and view all the answers

How does the structure of a vein's wall facilitate its compression by skeletal muscles, and why is this important?

<p>Vein walls are thin, allowing easy compression by skeletal muscles, which aids in moving blood back to the heart.</p> Signup and view all the answers

Match the blood vessel structures with their corresponding functions.

<p>Artery - Elastic Fibres = Stretching and recoil to maintain blood flow Vein - Valves = Preventing backflow of blood Artery - Narrow Lumen = Maintaining high blood pressure Vein - Thin Walls = Compression by skeletal muscles</p> Signup and view all the answers

Which statement accurately contrasts arteries and veins?

<p>Arteries carry blood away from the heart under high pressure with narrow lumens, whereas veins return blood to the heart with wider lumens and valves to prevent backflow. (D)</p> Signup and view all the answers

Atherosclerosis exclusively affects veins due to their lower blood pressure compared to arteries.

<p>False (B)</p> Signup and view all the answers

How does the accumulation of plaque in coronary arteries potentially lead to a myocardial infarction (heart attack)?

<p>Plaque buildup can occlude (block) the coronary arteries, restricting blood flow to the heart muscle; prolonged restriction can cause tissue death leading to a heart attack.</p> Signup and view all the answers

The process of atherosclerosis begins with damage to the inner lining of an artery, which attracts __________ that consume cholesterol and form plaque.

<p>macrophages</p> Signup and view all the answers

Match each factor with whether it is a controllable or uncontrollable risk factor for atherosclerosis:

<p>Genetics = Uncontrollable Age = Uncontrollable Gender = Uncontrollable High blood pressure = Controllable</p> Signup and view all the answers

How do macrophages contribute to the progression of atherosclerosis following initial damage to the arterial wall?

<p>By releasing growth factors that stimulate the development of fibrous tissue and consuming cholesterol to form plaque. (C)</p> Signup and view all the answers

The primary danger of plaque buildup in arteries is solely the gradual narrowing of the vessel, and not the risk of sudden blood clot formation.

<p>False (B)</p> Signup and view all the answers

Which of the following is a direct consequence of the occlusion of coronary arteries?

<p>Potential death of heart tissue due to lack of oxygen. (B)</p> Signup and view all the answers

Flashcards

Capillaries

Small blood vessels connecting arteries to veins. They facilitate material exchange between blood and cells.

Capillary Adaptations

Large surface area, narrow lumen (one RBC at a time), thin walls (one cell thick) for rapid diffusion.

Artery vs. Vein (Walls/Lumen)

Compared to veins, arteries have thicker walls and a narrower lumen.

Artery Function

Transports blood away from the heart, withstands high blood pressure with thick walls and collagen.

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Artery Adaptations

Thick walls to handle pressure, collagen for strength, smooth muscle to maintain pressure between beats.

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Artery structure

Blood vessel with relatively thick wall and a narrow lumen

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Vein structure

Blood vessel with relatively thin wall and wide lumen

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Artery wall adaptation.

Withstand the high pressure of blood pumped directly from the heart.

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Arteries

Vessels that carry blood away from the heart; walls contain elastic fibers for stretching and recoil.

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Pulse

The rhythmic throbbing felt in arteries due to heartbeats.

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Pulse Rate

The number of heartbeats (pulses) per unit of time, often measured in beats per minute (BPM).

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Oximeters

Devices used to measure pulse rate, often by shining light through the skin.

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Veins

Vessels that return blood to the heart; have valves to prevent backflow.

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Vein Valves

Found in veins, they prevent blood from flowing backward, ensuring it moves toward the heart.

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Vein Wall Flexibility

A characteristic of vein walls, allowing compression by skeletal muscles to aid blood flow.

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Lumen

The hollow space inside a blood vessel through which blood flows.

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Artery Lumen

Arteries have narrower lumens (inside space) to maintain high pressure.

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Vein Lumen

Veins have wider lumens to facilitate easier blood flow back to the heart.

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Atherosclerosis

Hardening and narrowing of arteries caused by plaque buildup.

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Coronary Artery Occlusion

Blockage of coronary arteries, often due to atherosclerosis.

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Plaque Formation

Macrophages consume cholesterol, forming plaque and fibrous tissue, potentially blocking the artery.

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Study Notes

  • B3.2 Transport covers theme: Form and Function, and falls under Level of Organisation: Organisms

Capillaries

  • Capillaries connect arteries to veins
  • The capillaries' major function is to exchange materials between the blood and cells

Adaptations of Capillaries

  • Large surface area is achieved via capillaries, these are highly branched with narrow diameters
  • The narrow lumen allows one red blood cell to pass through at a time
  • Thin walls allow for rapid exchange of materials by diffusion, averaging one cell thick

Arteries vs Veins: Micrograph

  • Arteries have a relatively thick wall and a narrow lumen
  • Veins have a relatively thin wall and wide lumen
  • A, in the image is an artery, due to the thicker wall and relatively narrow lumen
  • B, in the image is a vein, due to the much thinner wall, and a relatively wider lumen

Arteries

  • Arteries transport blood away from the heart
  • Arteries are adapted to withstand and maintain high blood pressure
  • Arteries have a thick wall to withstand high blood pressure
  • Collagen in the outer wall strengthens the artery to withstand high blood pressure
  • Smooth muscle in the artery can contract to maintain blood pressure
  • Elastic fibres in the artery wall allow the arteries to stretch and recoil as pressure changes
  • Recoil helps keep the blood moving in the artery
  • The narrow lumen helps maintain high blood pressure
  • The lumen is lined with smooth endothelial cells, to reduce friction as blood flows

Measuring Pulse Rate

  • The pulse is detectable because of the heart's beating
  • Using fingertips, a pulse can be felt at the radial artery in the wrist or the carotid artery in the neck
  • Pulse rate can also be determined using smart watches and oximeters by counting the number of beats per unit of time

Veins Adaptation

  • Veins adaptations for the return of blood to the heart include valves to prevent backflow
  • Veins also have flexible walls which allow it to be compressed by muscle action

Veins

  • Veins return blood to the heart
  • Blood returning to the heart is moving slowly, and is not under high pressure.
  • Veins are adapted to return blood to the heart
  • Veins have a thin wall, for compression by skeletal muscles, which moves blood back to the heart
  • Veins have a wide lumen, to carry a large volume of blood
  • Valves in veins prevent the backflow of blood

Arteries and Veins: Comparison

  • Both arteries and veins have three layers of tissue in their walls
  • Arteries have a thick outer wall compared to vein outer wall
  • The artery lumen is small relative to a vein
  • Arteries have a thick layer of muscles and elastic fibres, veins have a thin layer of muscle and elastic fibres
  • Arteries: Narrow lumen, maintaining high pressure
  • Veins: Wide lumen
  • Arteries: Thick walls
  • Veins: Thin walls
  • Arteries: blood flows away from the heart
  • Veins: blood flows back to the heart
  • Arteries have no valves
  • Veins have valves to prevent backflow of blood

Atherosclerosis

  • Atherosclerosis is the hardening and narrowing of the arteries due to the build of cholesterol, triglycerides and other substances on artery walls

Occlusion of Coronary Arteries

  • Coronary arteries branch off of the main artery, the aorta, and supply the heart with oxygen and nutrients
  • Coronary arteries can be occluded (blocked) due to atherosclerosis
  • Occlusion of the coronary arteries can lead to the death of heart tissue, and heart attacks

Causes of Atherosclerosis

  • The inner lining of an artery is damaged, due to high blood pressure
  • Macrophages (a type of white blood cell) are attracted to sites of damage within the arteries
  • Macrophages release growth factors which stimulate the development of fibrous tissue
  • Macrophages consume cholesterol and begin to form a plaque
  • Plaque continues to grow and blocks the artery
  • The plaque can break away from the artery and cause a blood clot

Risk Factors of Atherosclerosis

  • List risk factors associated with atherosclerosis
  • Genetics: increased risk associated with several genes
  • Age: arteries of older people are more likely to be damaged
  • Gender: males are more likely to develop atherosclerosis
  • Obesity: increases blood pressure and damages artery walls
  • Physical inactivity: can lead to obesity.
  • Smoking: increases blood pressure
  • Diet high in fats and cholesterol

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B3.2 Transport - OCR First Exams 2025 PDF

Description

This lesson covers the transport of blood in organisms, including the structure and function of capillaries, arteries, and veins. It delves into the adaptations of capillaries for efficient material exchange and compares the structural differences between arteries and veins as seen under a microscope.

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