What is the job of the circulatory system?

To carry substances such as oxygen, glucose and waste between the exchange surfaces and every cell of the body.

What is meant by a double circulatory system?

It is one in which the blood passes through the heart twice for each complete circuit of the body.

Why do mammals need a double circulation rather than a single one?

Blood loses pressure as it passes through the lungs, so returning it to the heart lets it be pumped to the body at high pressure and deliver oxygen quickly.

How is the circulatory system linked to the gas exchange system?

Blood picks up oxygen and gives up carbon dioxide at the alveoli in the lungs, then carries the oxygen to the respiring cells.

Describe the order of the vessels blood passes through on its way from the heart to a tissue and back.

It leaves in an artery, passes into smaller arterioles, then through capillaries in the tissue, and returns in a vein.

OCR GCSE Biology A J247

Cell Level Systems

Topic overview Microscopy, and sub-cellular structures DNA structure: polymer, double helix and nucleotides Enzyme action, and investigating enzymes Cellular respiration as an exothermic process Aerobic and anaerobic respiration compared Synthesis and breakdown of carbohydrates, proteins and lipids Photosynthesis: producers and the process Photosynthesis as endothermic, and investigating it Limiting factors in photosynthesis

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Topic overview Cycling materials, and the role of microorganisms The carbon and water cycles, and decomposition Levels of organisation, and abiotic and biotic factors Interdependence, competition and trophic levels Pyramids of biomass and the efficiency of transfer

Genes, Inheritance and Selection

Topic overview Genetic terms, and the genome Genome, environment and mutations Asexual and sexual reproduction compared Haploid, diploid and meiosis Single gene inheritance and Punnett squares Sex determination, multiple genes and Mendel's work Variation within a population, and classification Natural selection and evolution Evidence for evolution, and the work of Darwin and Wallace

Global Challenges

Topic overview Field investigations, and human impact on ecosystems Maintaining biodiversity, monitoring conservation and ecotourism Food security, agricultural and biotechnological solutions Selective breeding and genetic engineering Health, disease, and types of disease Interactions between diseases, and how they spread Reducing the spread of disease, and named examples Physical and chemical plant defences White blood cells, antibodies and platelets Non-specific defences and the immune system Vaccines, medicines and aseptic technique Developing new medicines, and non-communicable disease Treating cardiovascular disease, and lifestyle factors Cancer, and the use of stem cells in medicine Gene technology in medicine, and the human genome

Organism Level Systems

Topic overview The nervous system and coordinated responses The reflex arc The eye and its common defects The structure and function of the brain Hormones and the endocrine glands Hormones in reproduction and the menstrual cycle Methods of contraception Tropisms, auxin and the roles of plant hormones Homeostasis, and the skin in temperature control Insulin and the control of blood glucose Type 1 and type 2 diabetes Osmotic changes in body fluids, and the kidneys Kidney structure and the parts of the tubule

Scaling Up

Topic overview Diffusion, osmosis and active transport Mitosis, the cell cycle and cell differentiation Stem cells in animals and meristems in plants Surface area to volume ratio and exchange surfaces The circulatory system, the heart and blood vessels Red blood cells and plasma Root hair cells, transpiration and translocation Xylem and phloem Factors affecting water uptake, and the potometer

Scaling Up

The circulatory system, the heart and blood vessels

3 things to know
Paper 1

Overview

The job of the circulatory system, the double circulation and its two circuits, its link to gas exchange, the order of arteries, arterioles, capillaries and veins, the four chambers of the heart and the vessels entering and leaving it, the tricuspid, bicuspid and semilunar valves, the thicker left ventricle wall, cardiac muscle, and how arteries, veins and capillaries are adapted to their functions.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Name each ventricle's outflow vessel and its destination, the valves between the atria and ventricles, the valves at the ventricle exits, and what valves do.

Key term

Name the two circuits that make up a mammal's circulation.

Key term

Which vessels carry blood away from the heart and which return it?

Questions from this subtopic

Each one with the model answer underneath.

1
What is the job of the circulatory system?
Model answer
To carry substances such as oxygen, glucose and waste between the exchange surfaces and every cell of the body.
2
What is meant by a double circulatory system?
Model answer
It is one in which the blood passes through the heart twice for each complete circuit of the body.
3
Name the two circuits that make up a mammal's circulation.
Model answer
The circuit to the lungs and back, and the circuit to the rest of the body and back.
4
Why do mammals need a double circulation rather than a single one?
Model answer
Blood loses pressure as it passes through the lungs, so returning it to the heart lets it be pumped to the body at high pressure and deliver oxygen quickly.
5
How is the circulatory system linked to the gas exchange system?
Model answer
Blood picks up oxygen and gives up carbon dioxide at the alveoli in the lungs, then carries the oxygen to the respiring cells.
6
Describe the order of the vessels blood passes through on its way from the heart to a tissue and back.
Model answer
It leaves in an artery, passes into smaller arterioles, then through capillaries in the tissue, and returns in a vein.

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Cell Level Systems

Community Level Systems

Genes, Inheritance and Selection

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AA diet high in sugar and fat leads to obesity.

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