7 - INTRODUCTION TO THE CARDIOVASCULAR SYSTEM AND BLOOD TYPING

Question 1

LOCATION OF THE HEART

Answer 1

• In the mediastinum with the lungs
• Level of the 2nd rib
• Roughly central, but with the base pointing towards the right and the apex towards the left

Question 2

HEART COVERINGS: PERICARDIUM

Answer 2

The heart sits in a “bag”: pericardium
• Lubrication
• Mechanical protections = protects it and allows it to move smoothly
Pericardium has 3 main layers:
• Fibrous pericardium
• Serous pericardium
• Epicardium

Question 3

Pericarditis

Answer 3

problems with the pericardium, which impact the movement and function of the heart.

Question 4

pericardium formation

Question 5

heart wall

Answer 5

3 muscular layers to provide the contractile properties of the heart
Epicardium
Myocardium (muscle layer)
Endocardium (lines the inside)

Question 6

4 CHAMBERS AND 4 VALVES

Answer 6

left atrium
right atrium
Left Ventricle
Right ventricle
Pulmonary valve
Aortic valve
Bicuspid valce
Tricuspid valve

Question 7

HEART VALVES: ATRIOVENTRICULAR VALVES

Answer 7

Valves open and close in response to pressure changes as the heart relaxes and contracts.
Atrioventricular valves: prevent back flow from Ventricles to Aorta
Chordae tendinae stop valves acting like a swing door
Tricuspid on R, bicuspid on L (Mitral)

Question 8

Semilunar valves

Answer 8

base of arteries: prevent back flow from arteries to ventricles
Aortic and pulmonic valves
• Release of contraction closes valves = Prevents blood running back to refill the ventricles
• Tricuspid

Question 9

Problems with the valves

Answer 9

Incompetent valves - Valves (leaflets) do not fully close so there is regurgitant flow
• Valvular stenosis - stiffened valves caused by repeated infection, congenital disease or calcium deposits. Opening is narrowed so insufficient blood gets through.

Question 10

STRUCTURE: ARTERIES AND VEINS

Answer 10

Same basic structure in both types of vessel, but the proportion may vary.
3 layers-
• Tunica adventitia/externa: supportive outer.
Nerves and blood vessels
• Tunica media: muscular middle, affects resistance to blood flow (ie involved in control of blood pressure)
• Tunica intima: endothelial, inner, layer creates a smooth surface and involved in communication

Question 11

TUNICA MEDIA

Answer 11

Smooth muscle, helps move blood along the arteries
• Vasoconstriction of smooth muscle decreases lumen size
Vasodilation of smooth muscle increases lumen size

Question 12

Importance of lumen size?

Answer 12

Lumen size affects blood flow rate and hence blood pressure.
Changes in radius affect resistance of the blood vessel inversely by 4. ie increase radius by ¼ gives a 16 fold decrease in resistance.
Affects single vessel, not whole system.
Small lumen size = increased blood pressure

Question 13

ARTERIAL SYSTEM, elastic to absorb large eflux of blood from heart, even distribution of blood

Answer 13

Large arteries, small arteries, arterioles, capillaries

Question 14

Large arteries

Answer 14

More muscular walls push blood along to organs.
Distribution role.
Renal, carotid, mesenteric.
Don’t affect BP.
Elastic to absorb high volume and pressure from heart

Question 15

Small arteries

Answer 15

Distribution and resistance. 
Highly innervated. 
Regulate arterial Pressures. 
Receptors for circulating hormones and locally produced signals ie K+
and NO

Question 16

Arterioles

Answer 16

smaller
when constricted, blood flow to organs can be bypassed.
Resistance vessels.
Same as small arteries

Question 17

Capillaries

Answer 17

small and thin to allow for exchange of materials.
Exchange vessels.
No smooth muscle.
High exchange
• Blood flow in capillaries= Blood flow entering aorta.
• Velocity is 0.05 cms/s compared to 50cms in aorta

Question 18

TYPES OF CAPILLARIES

Answer 18

Continuous Capillaries
Fenestrated Capillaries
Sinusoid Capillaries

Question 19

Continuous Capillaries

Answer 19

Most common
• Continuous. Gaps only between endothelial cells (tight junctions)
• CNS, lungs, muscle tissue, skin

Question 20

Fenestrated Capillaries

Answer 20

• Pores of 70-100nm in the capillary wall, transport of large substances
• Choroid plexus, kidneys, endocrine glands, villi and ciliary processes of the eye

Question 21

Sinusoid Capillaries

Answer 21

• Wider gaps in the vessel walls (Lets blood cells through)

* Bone marrow, endocrine glands, placenta

Question 22

VENOUS SYSTEM

Answer 22

Veins + venules

Question 23

Veins

Answer 23

• Under less pressure
• Less smooth muscle (less resistance)
• Stretchy (high capacitance vessels)
• Larger veins have valves to prevent blood flowing backwards.

Question 24

Venules

Answer 24

• 8-100µm in diameter, more porous than arterioles.
• Capillaries drain into venules
• Continued loss of BP, almost 0 by the time it gets to the vena cava

Question 25

WHICH VESSELS CARRY BLOOD IN A BODY AT REST?

Answer 25

his differs between the upright and supne position

Question 26

UPRIGHT Blood distribution at rest

Answer 26

* Vein = 65% * Arteries = 13% * Arterioles = 2% * Capillaries = 5% * Central blood volume = 15%

Question 27

SUPINE blood distribution at rest

Answer 27

``` • Vein = 54% • Arteries = 10% Arterioles = 1% • Capillaries = 5% • Central volume = 30% * 12% in heart * 18% in lung In the supine position there is : 1. Less blood in peripheral veins 2. More blood in central volume ```

Question 28

CIRCULATION AND THE HEART

Answer 28

Blood flows through and around the heart . When it exits it can be split into three distribution systems: 1. Pulmonary Circulation (RHS) 2. Systemic Circulation (LHS) 3. Coronary Circulation (from aorta)

Question 29

RHS: PULMONARY CIRCULATION

Answer 29

* Positioned towards back of the heart. * Crescent shaped * Blood in through Venae cavae * Back out through pulmonary artery

Question 30

LHS: SYSTEMIC CIRCULATION

Answer 30

* At front and apex * More circular (thicker walls) * In through pulmonary veins * Out through Aorta to aortic arch

Question 31

CORONARY CIRCULATION

Answer 31

* L and R Coronary arteries from the base of the aorta. Shut during contraction * Coronary arteries branch to supply the heart * Arteries supply the capillaries for gas and nutrient transfer before draining into the veins

Question 32

BLOOD GROUPS

Answer 32

43 blood groups • Most common are the ABO group and the Rhesus +/-groups • The ABO group gives us 4 key groups; A, AB, B and O. Adding Rhesus status to this gives 8 main groups. • Two antigens and two antibodies are responsible for the ABO types • Discovered by Karl Landsteiner in 1901 (University of Vienna) who tried to understand why blood transfusions sometimes caused death but at other times saved a patient

Question 33

ABO BLOOD TYPES: ANTIGENS AND ANTIBODIES

Answer 33

Red Blood Cells have different surface molecules (Antigens). The A/B antigens are sugars. Blood plasma will have Antibodies to the surface molecules that your RBCs do not have. When a blood transfusion occurs with the wrong blood type, the antibodies bind to the RBCs expressing the different antigen. This causes clumping of the RBCs and antibodies (agglutination) and causes severe problems (thrombosis).

Question 34

Blood transfusions

Answer 34

* Knowing blood type before transfusion avoids problems. * Agglutination reactions are performed to determine blood type * Type A: will agglutinate Blood type B so cannot receive blood from Type or type AB

Question 35

UNIVERSAL DONORS AND RECEIVERS

Answer 35

Individuals with type O blood do not have A or B antigens = universal donor (will not agglutinate) • Make antibodies to A and B, cannot receive blood from any other blood type Individuals with type AB blood have A and B antigens = universal receivers for transfusions • do not make any A or B antibodies, their blood can only be given to AB recipients

Question 36

BLOOD GROUP INHERITANCE

Answer 36

* 3 alleles for human blood type: IA, IB, and I * Both A and B alleles are dominant over O * People who are type O have OO genotypes - they inherited a recessive O allele from both parents * A and B alleles are codominant, so if A is inherited from one parent and B from the other, the phenotype is AB

Question 37

ABO INCOMPATIBILITY IN BABIES

Answer 37

Common and generally mild condition in babies • Can occur during pregnancy if mother and baby’s blood types are incompatible • RBCs are broken down causing jaundice, anaemia, and death if severe • Mother’s antibodies linger after birth and destroy RBC of baby, causing an increase in bilirubin. • Babies with high levels of bilirubin may need phototherapy (oxidises bilirubin and facilitates its removal by the liver) or a blood transfusion • More severe outcome with Rhesus incompatibility (haemolytic disease)