Learning outcomes:
describe the composition of the blood: red blood cells, white blood cells, platelets and plasma
understand the role of plasma in the transport of carbon dioxide, digested food, urea, hormones and heat energy
explain how adaptations of red blood cells, including shape, structure and the presence of haemoglobin, make them suitable for the transport of oxygen
describe how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen - b
understand that vaccination results in the manufacture of memory cells, which enable future antibody production to the pathogen to occur sooner, faster and in greater quantity
understand that platelets are involved in blood clotting, which prevents blood loss and the entry of micro-organisms
describe the structure of the heart and how it functions - b - c
explain how the heart rate changes during exercise and under the influence of adrenaline
describe the structure of arteries, veins and capillaries and understand their roles - b
understand the general structure of the circulation system to include the blood vessels to and from the heart, the lungs, the liver and the kidneys.
Blood consists of 4 main parts;

Plasma – mostly water used for transporting things around the body (i.e. CO2 glucose, amino acids, other products of digestion, urea, hormones and heat energy.

Red Blood Cells – adapted to carry O2 around the body. O2 attaches to haemoglobin protein, which the RBCs are filled with.
Other adaptations of RBCs include;
- Smooth edges
- Biconcave shape (increases surface area and allows folding)
- Made in huge quantities
- No nucleus (so more room for haemoglobin)

Platelets – help clot the blood. This stops blood loss and also prevents microorganisms entering the body.

White Blood Cells – are part of the immune system. There are two main types; macrophages and lymphocytes.

Macrophages (sometimes called Phagoctyes)
Travel in the blood. They detect foreign bodies (i.e. foreign cells, toxins, cells infected with virus and cancerous cells) and engulf and destroy them. Engulfing and destroying is called phagoctyosis

Lymphoctyes stay in the lymph system (you don’t need to know what this is). They make antibody proteins in large numbers. Antibody proteins travel in the blood and stick to foreign objects. This helps because;

1. Foreign objects are stuck to each other, stopping them spreading
2. Macrophages can engulf many foreign objects at the same time, speeding up the killing process

Extension (not technically on syllabus, but not sure…)
Plasma carries CO2 around the body. How?

CO2 + H2O à HCO3- + H+

The CO2 reacts with water molecules to produce the Hydrogen Carbonate ion. In the lungs the reaction reverses to produce CO2 again. CO2 is, therefore, carried as an aqueous ion in the blood plasma.

The Human Heart:

You need to know;

1. the names of the 4 chambers of the heart
2. the names of the 2 arteries and 2 veins attached to the heart
3. The names of the two sets of valves in the heart

Contraction in the heart:

Remember, the atria contract first. The L & R atria contract at the same time. The ventricles contract second. The L & R Ventricles contract at the same time.

1. Blood enters the atria
2. Both atria start to contract, pushing the blood into the ventricles through the open cuspid valves
3. When the ventricles are full they begin to contract
4. The cuspid valves shut to stop backflow
5. Blood is forced out of the heart into the circulatory system through the open semi-lunar valves
6. When the ventricles finish contracting the S-L valves shut, stopping backflow.

Blood has to pass through the heart twice to complete a full circuit of the body (takes about 10 - 20sec). This is called a double circulation.

During exercise adrenaline is released from the adrenal glands. Adrenaline has two effects of the heart;

1. Makes it beat faster
2. Makes each beat harder

The combined effect is to massively increase the volume of blood pumped by the heart per minute.

Extension (summarizes point above mathematically )
Cardiac Output = Heart Rate x Stroke Volume
CO = Volume of blood pumped per minute
HR = No of beats per minute
SV = Volume of blood ejected per beat
Adrenaline increases both HR & SV, therefore, increasing CO lots


Arteries carry high pressure blood away from the heart.

Key Points:
1. Thick muscle layer to withstand high pressure blood
2. Elastic tissue allows artery to stretch when blood is forced into it
3. Protective collagen layer
4. Round shape
5. Relatively small lumen

Vein: Veins carry low pressure blood towards the heart.

Key Points:
1. Thin muscle layer (low pressure blood)
2. Valve to stop backflow
3. Protective collagen layer
4. Not a round shape (wall not thick enough to hold shape)
5. Large lumen (decreases effect of friction)
Artery, Vein and Capillary:
hb - cardio - arteries and veins.gif

Capillaries are adapted for exchange – they are not connected directly to the heart.

Key Points:

1. Walls are one cell thick (cells are called endothelial cells)
2. Lumen is the same width as one RBC (therefore more of RBC in contact with wall, therefore smaller diffusion distance)
3. No muscle or elastic tissue
4. Tiny (compare the scales and remind yourself what a чm is)

Something extra you’re supposed to know:

The vessel taking blood to the kidneys is the renal artery
The vessel taking blood away from the kidneys is the renal vein
The vessel taking blood to the liver is the hepatic portal vein
The vessel taking blood away from the liver is the hepatic vein

Hepatic Portal Vein? The blood that goes to the liver comes directly from the gut, not from the heart, therefore, it’s not an artery but a portal vein.

Why does this happen? It makes sense to send all blood from the gut directly to the liver because if there are any poisons in what you’ve eaten they get broken down by the liver before going around the body. Cunning, eh?