2.1. Blood & Cardiovascular System

Question 1

Describe the clotting cascade (Haemostasis)

Answer 1

• Vasoconstriction occurs, reflexive contraction that causes a decrease in blood flow to the area
• Platelets aggregate near injury site and form a plug
• Circulating prothrombin is converted to thrombin, which promotes the formation of insoluble fibrin from fibrinogen
• Fibrin adheres to the plug to form an insoluble clot

Question 2

What is physiological anaemia of pregnancy?

Answer 2

Plasma volume increases more quickly than red blood cell mass, this causes haemodilution and therefore a decrease in haemoglobin concentration

Question 3

What are other causes of anaemia in pregnancy?

Answer 3

• Sickle cell trait
• Thalassaemia
• Sickle cell anaemia
• Inheritable disease

Question 4

What are the signs/symptoms and risk of sickle cell anaemia?

Answer 4

• Pain crises-> sickle cells block blood flow in tiny blood vessels and causes oedema of peripheries
• Delayed growth
• Infections-> spleen damage
• Anaemia-> life span of sickle cells is shorter so there are fewer RBCs in body
• Vision problems-> blood vessels in eyes can become plugged with sickle cells which damages retina

Question 5

Which blood group is the universal recipient?

Answer 5

AB

Question 6

Which blood group is the universal donor?

Answer 6

O

Question 7

Describe the pump system of the heart

Answer 7

Blood from the right side of heart enters the pulmonary circulation to the capillaries surrounding the alveoli of the lungs where the blood is oxygenated.
This oxygenated blood returns to the left side of the heart in the pulmonary veins.
Oxygenated blood is then pumped from the left side of the heart around the body, and then back to the right side of the heart. This is known as the systemic circulation.

Question 8

Arteries:

• Direction of blood flow
• Oxygen concentration
• Pressure
• Key structural features
• Valves?

Answer 8

• Away from heart
• Oxygenated (except pulmonary artery)
• High
• Elastic; thick outer walls
• No valves

Question 9

Veins:

• Direction of blood flow
• Oxygen concentration
• Pressure
• Key structural features
• Valves?

Answer 9

• Towards heart
• Deoxygenated (except pulmonary vein)
• Low
• Elastic; thin outer walls
• Valves

Question 10

Capillaries:

• Oxygen concentration
• Key structural features
• Valves?

Answer 10

• Oxygen diffuses into capillaries at lungs and out to body cells
• One cell thick- allows rapid diffusion

Question 11

Stroke volume

Answer 11

Volume of blood pumped from the left ventricle per beat

Question 12

Heart rate

Answer 12

Number of times the heart beats per minute

Question 13

Cardiac output

Answer 13

Amount of blood the heart pumps through the circulatory system in 1 min

Question 14

Blood pressure

Answer 14

The force exerted on the wall of a blood vessel by the blood

Question 15

What does blood pressure depend on?

Answer 15

• Cardiac output

- Peripheral vascular resistance

Question 16

Systolic blood pressure

Answer 16

Pressure in the vessels as the left ventricle expels blood into the aorta.

Question 17

Diastolic blood pressure

Answer 17

When the aortic valve closes

Question 18

What are the 5 ways in which blood pressure is controlled?

Answer 18

1. Diameters of vessels- altered by relaxation or constriction of smooth muscle
2. Baroreceptors- maintain BP sitting to standing, slows heart rate
3. Blood carried hormones- eg. adrenaline
4. Endothelial cells
5. Kidney- anti-diuretic hormone, renin-angiotensin balance

Question 19

What is supine hypotension syndrome?

Why does it occur?

Answer 19

The gravid uterus compresses the aorta and vena cava, thus obstructing the flow of blood circulation.
Hypotension and bradycardia are signs, this happens when a woman lies on her back after 28wks.
Compression is relieved by tilting woman on her LEFT side.

Question 20

Pregnancy is a ……….. state, with reduced……… activity

Answer 20

pro-coagulant

fibrinolytic (slower breakdown of clots)

Question 21

How much does blood plasma volume increase by?

Answer 21

40-50%

Question 22

What happens to the heart?

Answer 22

It enlarges and moves upwards and laterally

Question 23

What happens to cardiac output and why?

Answer 23

Increases by 30-50%

To accommodate increased blood volume circulating

Question 24

How much does RBC mass increase by?

Answer 24

20-30%

Question 25

The increase in plasma volume is greater than RBC mass, what does this result in?....

Answer 25

Haemodilution and an apparent decrease in haemoglobin concentration

Question 26

How much does heart rate increase by?

Answer 26

10-20%

Question 27

How much does stroke volume increase by?

Answer 27

10%

Question 28

How much does peripheral resistance decrease by?

Answer 28

35%

Question 29

What are 2 functions of pregnancy-induced hypervolemia?

Answer 29

1. Increased blood volume facilitates maternal and fetal exchange of respiratory gases, nutrients, metabolites 2. The impact of maternal blood loss at birth is reduced

Question 30

Blood volume increases by.....% | why?

Answer 30

20-50% | flows to uterus, skin, breasts, kidneys

Question 31

When would you treat a woman for anaemia in 1st trimester?

Answer 31

Hb < 100g/L

Question 32

When would you treat a woman for anaemia in 2nd/3rd trimester?

Answer 32

Hb < 100g/L

Question 33

What could be causes of low blood pressure?

Answer 33

- Infection - Dehydration - Anaemia - Heart condition - Malnutrition