Blood🎈

Question 1

Red blood cells (erythrocytes)

Answer 1

Carry oxygen
Have a biconcave disc shape to give a larger surface area for absorbing oxygen.
No nucleus - more room to carry oxygen.
Contain haemoglobin
In the lungs, haemoglobin binds to oxygen to become oxyhemoglobin.
In body tissues oxyhemoglobin splits into haemoglobin and oxygen to release oxygen to cells.

Question 2

White blood cells (phagocytes, lymphocytes)

Answer 2

Defend against infection.
Phagocytes- Change shape to engulf unwelcome microorganisms- phagocytosis.
Lymphocytes- Produce antibodies against microorganisms and release antitoxins to neutralise toxins produced by microorganisms.
White blood cells multiply to fight off infection.

Question 3

Platelets

Answer 3

Help blood clot
Small fragments of cells- no nucleus
Stop blood from wound getting out and stop microorganisms getting in.
Lack of these can cause excessive bleeding and bruising.

Question 4

Plasma

Answer 4

Carries: 
Red blood cells
White blood cells
Platelets 
Glucose and amino acids + nutrients 
Carbon dioxide
Urea from liver to kidneys
Hormones
Proteins
Antibodies and antitoxins.

Question 5

Arteries

Answer 5

Walls are strong and elastic to withstand pressure of blood from the heart.
Thick walls compared to hole in the middle (lumen).
Contain thick layers of muscle- strong
Elastic fibres allow them to stretch and spring back.

Question 6

Capillaries

Answer 6

Arteries branch into capillaries.
Tiny
Very narrow to squeeze between cells. So they can carry the blood really close to every cell to exchange substances.
Permeable walls for diffusion.
Supply nutrients and oxygen and take away waste like CO2.
Walls are one cell thick- increases rate of diffusion by decreasing the distance over which it occurs.

Question 7

Veins

Answer 7

Take blood back to the heart.
Capillaries join to form veins.
Walls not as thick as artery walls because lower pressure of blood.
Bigger lumens than arteries to help blood flow.
They have valves to keep blood flowing in right direction.