Circulation

Topics: Heart, Blood, Blood vessel Pages: 10 (521 words) Published: September 22, 2013
Circulatory Systems





Transport
Diffusion
Circulatory system
As organisms increase in complexity diffusion
becomes inefficient
– Gases
– Components of immune systems
– Sugars, salts,
– Removal of metabolic waste

1

Characteristics of a blood vascular system

• A blood
circulatory
system consists
of the following:
• Two types
– Open →
Arthropods
– Closed →
Vertebrates
• Pump
• Vessels
• Circulatory fluid

2

Circulatory system - Open
• Insects and some molluscs
• Blood pumped by heart →
blood spaces
• Sinuses
• Blood in direct contact with
tissues
• Returns to heart via open veins
• No control

3

Circulation in vertebrates

4

Double circulation
• Blood moves through heart 2x during a circuit
– Lungs
– Body
– Low pressure from lungs,

• Birds
• Warm blooded creatures
• High metabolic rate
– Requires good oxygen supply → aerobic respiration


5

Human cardiovascular system
• Human cardiovascular system blood flows
• Muscular heart → arteries → smaller
aterioles → arterioles → capillaries
– take blood to the tissues
• Capillaries → venules → veins
• Transport blood from tissues → return the
blood to heart.

6

Organs parallel not sequential

7

The Heart

8

The structure of blood vessels
Tunica
externa

Endothelium

Endothelium

• Tunica externa
– Collagen fibres
– outermost layer → forms a connective tissue sheath
– stabilise & anchor the vessel → blending of connective tissue fibres into adjacent tissue.

9

The structure of blood vessels
Tunica
externa

Endothelium

Endothelium

• Tunica media
– Smooth muscle, connective tissue +elastic fibres
– stimulated by sympathetic nerve fibres
– very thick in arteries.
10

Veins

• Veins carry blood from
capillaries to the heart.
– pulmonary veins,
– Venules
– Pressure in veins low
– muscular contractions
– valves

11

Varicose veins

12

Capillaries
• Capillaries
– Join arterioles to venules
– Capillary wall v. thin → 1 cell layer thick.
– Nutrients, wastes, gases & hormones exchanged

13

Artery

Vein

Capillary

Transports blood →
heart

Blood towards
heart

Links artery to vein

Tunica media →
Tunica media thin,
No tunica media
thick elastic smooth few muscle fibres
muscle
No semi lunar
Semi lunar valves No semi lunar valves
valves
Blood flow rapid

Blood flow slow

Oxygenated blood
except pulmonary
artery

Deoxygenated
blood except
pulmonary

Mixed
14

The coronary circulation
• Branched aorta beyond the aortic
valve (within heart)
– Two openings → right and left
coronary arteries
– Pass onto surface
– network of capillaries →
penetrate every portion of the
heart.
• Capillaries → coronary veins →
right atrium.

15

The Cardiac cycle













Events of 1 heartbeat
70 beats/min at rest
5 L/min
Contraction – systole
Relaxation – diastole
Atrial diastole
– Fills with blood
– Ventricles relaxed
Atrial systole
– Atria contract
Ventricular systole
– 0.1 -0.2 sec after AS
– Lub
– Dub
Mygogenic stimulation
Specialised nerve cells
– Sino atrial node

16

Myogenic control of heartbeat
• Mygogenic stimulation
• Specialised nerve cells
– Sino atrial node
– Atrioventricular node
• Ventricular septum
– Bundle of His
– Purkyne bundles
– Purkinje fibres

17

Myogenic control of heart
• SA node depolarised
– Atrial diastole
– Action potential
• AV bundle depolarised
– 0.15 s
– Bundle of His
– Purkyne bundle
– Ventriclular diastole
• Absolute refractory period
• Relative refractory period
18

Blood

19

Red blood cells
• Circular, biconcave
• 7-8 µm









5 000 000/mm3
Flexible
Haemoglobin
No nucleus
Anaerobic respiration
Carbonic anhydrase
2-10 million/sec destroyed
3 month lifespan

20

White blood cells - Granulocytes
• Multiple nuclear lobes
• Neutrophils (phagocytes)...
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