CY systems - circulatory

Question 1

Blood vascular system

Answer 1

Blood travels away from the heart in arteries
Returns to heart in veins
Arteries and veins connected by capillaries

Question 2

What are the 2 parts to the blood vascular system?

Answer 2

Systemic circulation:
- delivers blood rich in oxygen from left side to most of body tissues
Returns blood low in oxygen to right side of the heart
High pressure system
Extensive network formed
Pulmonary circulation:
- delivers blood low in oxygen from right side of heart to the lungs
- returns blood rich in oxygen to left side of heart
Low pressure system

Question 3

Name the 3 layers of blood vessels

Answer 3

Tunica intima (endothelium)
Tunica media (muscle layer)
Tunica externa/adventia (connective tissue

Question 4

Name the vessels in the CV system

Answer 4

Arteries:
- elastic
- muscular
- arterioles
Microcirculaton:
- capillaries (continuous and fenestrated )
- venules
Veins

Question 5

What do arteries have that veins do not?

Answer 5

Have a thicker wall
Smaller lumen
Maintains their shape
More resilient
Don't contain valves, veins contain many

Question 6

Describe arteries

Answer 6

1. Elastic
   eg. aorta, brachiocephalic, common carotid
   - withstand changes in pressure
   - ensure continuous blood flow
   - thick tunica media, many elastic fibres
2. Muscular
   - most named arteries
   - distribute blood to muscles and organs
   - lots of smooth muscle in tunica media
   - thick tunica externa
3. Arterioles
   - vasoconstriction and vasodilation

Question 7

Describe capillaries

Answer 7

Site of gas exchange/nutrient/waste exchange
- thin walled = endothelial and basement membrane layer
- types:
> continuous
> fenestrated (pores, found in kidneys)
> sinusoids (large gaps, found in liver)
Capillary beds:
- supplied by single met arteriole, contains 1000s of capillaries
- met arterioles connect arterioles and venules
- pre-capillary sphincters control blood flow to capillary beds

Question 8

Arteriovenous anastomoses

Answer 8

Form direct communication between arteriole and venules

- dilated blood bypasses the capillary bed and flows directly to venous circulation eg. temperature control

Question 9

Venules

Answer 9

Collect blood from capillary beds and deliver to small veins

Question 10

Veins

Answer 10

Low pressure system
Thin walled
Easily distensible

Question 11

Lymphatic system functions

Answer 11

Involved in the body’s defence mechanisms
Drainage of interstitial fluid

1. At arteriole end, high pressure caused by contraction of the heart forces fluid to move out and into the interstitial space
2. Lower pressure at the venous end causes fluid to be reabsorbed back into the capillary, however not all fluid is reabsorbed
3. Interstitial fluid forms lymph, and enters the lymphatic system, where it is returned into the blood stream at the subclavian vein in the neck
   pathway is:
   lymph capillaries, lymph vessels, lymph nodes, lymph trunks, thoracic duct and drained to left subclavian veins, or right lymphatic duct and drained to right subclavian vein
   + if fluid stays in interstitial space = oedema +

Question 12

Position of the heart

Answer 12

Protected by the ribs and  body of the sternum
2/3 lie to the left of midline
between 2nd and 5th ribs
Apex projects anteriorly to the left 
The great vessels arise from the base

Question 13

Pericardium

Answer 13

Consists of:
Fibrous pericardium
- inelastic sac of dense connective tissue that wraps around the heart
- prevents overfilling
Serous pericardium
- two layers - parietal and visceral - separated by pericardial cavity which contains serous fluid
- prevents friction

Question 14

Describe the layers of the heart wall

Answer 14

3 layers

• Endocardium: inner layer - endothelium
• Myocardium: middle layer - cardiac muscle
• Epicardium: outer layer - visceral pericardium

Question 15

Organisation of the heart

Answer 15

RIGHT SIDE - from systemic circulation so low in oxygen
> Superior and inferior vena cava 
> Right atrium
> Tricuspid valve
> Right ventricle
> Pulmonary semilunar valve
> Pulmonary trunk and arteries
TO THE LUNGS
LEFT SIDE - from lungs so blood rich in oxygen 
> pulmonary veins
> left atrium
> bicuspid valve
> left ventricle
> aortic semilunar valve
> aorta

Question 16

Heart valves

Answer 16

AV Valves -
- opened by blood flowing from atria to ventricles
- anchored by chordae tendinae to papillary muscles, prevent eversion of valves during ventricular contraction
- prevent backflow of blood into atria
Semilunar valves -
- opened by blood being pushed out of ventricles
- no chordae tendinae

Question 17

Coronary circulation

Answer 17

Blood delivered to myocardium during ventricular relaxation 
Left coronary artery -
- anterior interventricular
- circumflex
Right coronary artery - 
- marginal artery
- posterior interventricular 
Most cardiac veins drain into coronary sinus which empties into right atrium

Question 18

What are the properties of the cardiac muscle?

Answer 18

• forms a branching network of cells
• cells are interconnected by intercalated discs which contain gap junctions
• gap junctions allow ion transport between cells which promotes coordinated contraction
• cardiac cells act as a functional syncitium
• cardiac muscle is autorhythmic

Question 19

The conducting system

Answer 19

Coordinates heart contraction
Consists of non-contractile cells that initiate electrical impulses:
1. SA node spontaneously reaches threshold
2. Impulse spreads throughout the atria
3. Passes through remainder of heart via the cardiac conductive system
4. SA node sets rhythm – the pacemaker
5. Rate is modified by ANS

Question 20

Describe an ECG

Answer 20

Records the spread of electrical activity through the heart muscle
P wave = depolarisation of atria
QRS complex = depolarisation of ventricles
T wave = repolarisation of ventricles

Question 21

Describe the different between adult circulation and foetal circulation

Answer 21

Oxygen and nutrients received from placenta via umbilical vein need to bypass non-functional lungs
Foetal has 3 circulatory short cuts:
1. Ductus venosus connects umbilical vein to inferior vena cava
2. Foramen ovale connects right and left atria
3. Ductus arteriosus connects pulmonary artery to arch of aorta

Question 22

Changes at birth

Answer 22

Lungs expand therefore resistance falls in pulmonary circuit = decreased pressure in pulmonary trunk
Ductus arteriosus closes = decreased pressure in pulmonary trunk
Umbilical vessels close = increased pressure in aorta