Download The Cardiovascular System

Transport in Humans
(and other Mammals)
The Circulatory System
1
Cardiovascular System
Consists of Heart, Lungs and Vessels
Systemic
circulation BODY
HEART
LUNGS
Double Circulatory System
Pulmonary
circulation
The Heart
• Weighs approx 300g
• Thick muscular layer (myocardium) made of
Cardiac muscle
• Has it’s own blood supply
– covered in capillaries which get blood from coronary
arteries
• Myogenic- self exciting
– Continuous rhythm (can be altered)
3
• Two upper thin walled chambers – atria
• Two lower thick walled chambers –
ventricles
• Atria collect blood from the body –
attached to veins
• Ventricles send blood to the body –
attached to arteries
4
The Heart
•
•
•
•
Right side – deoxygenated
Left side – oxygenated
Separated by a thick walled septum
Right atrium and ventricle connected by
tricuspid valve
• Left atrium and ventricle connected by bicuspid
(mitral) valve
• Cuspid valves held shut by Chordae Tendinae
• Left ventricle is thicker than the right
5
Vessels of the Heart
•
•
•
•
Pulmonary artery*
Pulmonary vein
Superior and Inferior Vena cava
Aorta*
• *Semi-lunar valves
6
Diagram of the Heart
pg 13
7
Blood Flow Through the Heart
1.
2.
3.
4.
5.
Vena Cava – Superior/Inferior
Right Atrium
Tricuspid Valve
Right ventricle
Pulmonary Artery
LUNGS
8
Blood Flow Through the Heart
6. Pulmonary veins
7. Left Atrium
8. Bicuspid/Mitral/Atrioventricular valve
9. Left Ventricle
10. Aorta
MAJOR ORGANS
9
10
Control of the Heart
• Myogenic-Initiated from inside the heart as
opposed to nervous stimulus outside
• Initial Stimulus originates in the Sinoatrial
node (SA node)
• A pacemaker that determines heart rate
• Wave of excitation across both atria
causes them to contract
11
Control of the Heart
• Atrioventricular node (AV node)
• Sends waves of excitation along Purkinje
Fibres which collectively make up the
Bundle of His. Along septum, radiate
upwards
• Causes ventricles to contract
12
Cardiac cycle
• Systole -contraction of heart
• Diastole -Relaxation/filling of the heart
• Both atria contract at the same time
– Called ………………….
• Both ventricles contract at same time
– Called ………………….
• Relaxation of atria and ventricles
– Called ……………………….
13
Cardiac cycle
• Remind me…. What is it?
14
15
Vessels of the Cardiovascular
System
Arteriole
Artery
Capillary
Vein
Venuole
16
Vessels of the Cardiovascular
System
• Arteries – Arterioles – Capillaries Venuoles - Veins
• Different structures and functions
17
Arteries
•
•
•
•
Carry blood away from the heart
Blood in arteries is under high pressure
Their structure is related to their function
Round in structure with relatively thick
walls composed of three layers
18
Arteries
A. Tunica Intima – Single layer of
endothelial cells
B. Tunica Media – A thick layer containing
elastic fibres and muscle tissues. Closer
to heart more elastic fibres those further
away have more muscle fibre
C. Tunica Externa – Contains collagen
fibres for strength
19
Diagram of an Artery…
volunteer?
20
Blood vessels – the arteries
TUNICA MEDIA
TUNICA EXTERNA
TUNICA INTIMA (
LUMEN
Veins
• Carry blood back to the heart (generally
deoxygenated)
• Blood now flowing slowly, smoothly and under
low pressure (structure related to this function)
• Walls are relatively thin compared with arteries
• Still same three layers but the tunica media
differs in size – relatively narrow with few muscle
fibres and elastic fibres
• Semi Lunar valves present along length
22
Diagram of Veins
23
Blood vessels – the veins
TUNICA MEDIA
TUNICA INTIMA
TUNICA EXTERNA
LUMEN
Capillaries
• Link the arterial and venous blood supplies
• Blood flow is slow, blood pressure is falling and
is non-pulsatile
• Capillaries form vast networks in all tissues and
organs
• Composed of only the Tunica Intima, only a
single layer of endothelial cells, no elastic fibres
and no muscle tissue
25
Capillaries
• Exchange of materials between the blood
and the body takes place in the capillary
bed
26
Diagram of a Capillary
27
Blood vessels – the capillaries
LUMEN
ONE CELL THICK
Time for an exam question
page 13
29
Components of Blood
• Blood is made up of:
– Variety of cells
– Suspended in fluid – Plasma
• All blood cells develop from stem cells in
bone marrow
30
Plasma
•
•
•
•
•
Transports everything.
Blood cells.
Digested foods
(glucose).
Waste.
Hormones
•
•
90% water, 10% solutes
3 Proteins:
– Globulins, Albumins and Fibrinogen
immune
clotting
31
Red Blood cells
• Erythrocytes
• Red Blood cells carry
oxygen around the
body in haemoglobin.
• They have no nucleus
thus leaving more
space for oxygen
32
White blood cells
• Leucocytes
• Fight against disease.
• Destroys bacteria by
using antibodies.
• Fights toxins by using
antitoxins.
• Kills foreign microbes
by consuming them.
33
White blood cells cont.
• WBC’s divided into 2 groups:
– GRANULOCYTES
– AGRANULOCYTES
• Granulocytes have granules in cytoplasm &
multilobed nucleus. 3 types:
– Neutrophils
– Eosinophils
– Basophils
• Agranuloycytes are NOT granular or lobed
– Monocytes
– lymphocytes
34
Platelets
• Thrombocytes
• Platelets are tiny
fragments in the
body that help blood
clot at wounds.
35
Transport of gases
• Oxygen combines with Haemoglobin:
Haemoglobin + oxygen  oxyhaemoglobin
• Reversible so O2 is available to body
tissues.
• Each g of haemoglobin can combine with
1.34cm3 of oxygen.
• See WJEC (oxygen dissociation)
36
Oxygen Dissociation Curves
• Concentration of gases are measured
in partial pressures
• As haemoglobin is exposed to
increasing ppO2, haemoglobin
takes it up until saturated
• Each haemoglobin can take up
___ molecules O2
37
Oxygen Dissociation Curves
• Curve shape depends on number
of factors:
– pp CO2
– Temp
– pH
• Increasing ppCO2 shifts curve
right, Bohr Effect
due to decrease in affinity of
haemoglobin to O2
• Means oxyhaemoglobin releases
more O2 as CO2 rises ie when
cells are respiring more
38
Fetal Haemoglobin
• Haemoglobin F has a higher affinity for
oxygen than adult haemoglobin
• Means it is able to gain oxygen from
mothers haemoglobin
39
Myoglobin
• Myoglobin is a pigment found in muscle and
hearts of mammals
• Combines reversibly with Oxygen
• Takes up oxygen more readily than
haemoglobin
• Blood reaching muscle transfers O2 to
myoglobin acting as a temp store
• Myoglobin gives up its O2 when ppO2 drops to
very low value, eg after exercise
40
CO2
• See WJEC (transport of gases)
• CO2 produced in respiration diffuses into blood
and into RBCs
• In RBCs the CO2 combines with H2O to form
carbonic acid (H2CO3) – enzyme carbonic
anhydrase
• Carbonic acid then dissociates to
hydrogencarbonate ions
CO2 + H2O  H2CO3 
H+
+ HCO3
41
CO2
• Hydrogencarbonate ions diffuse into
plasma in exchange for Cl- ions
• CO2 reacts with haemoglobin and other
proteins to form carbamino compounds
• CO2 can be transported in blood 3 ways:
– Hydrogencarbonate ions
– Carbamino compounds
– Simple solution, dissolved in plasma
42
Tissue Fluid
• Fluid that leaks out of
capillaries is called tissue fluid
• It fills spaces between body
cells
• It contains:
–
–
–
–
–
Water
Glucose
Amino acids
Fatty acids
Glycerol
mineral ions
vitamins
Dissolved gases
43
• Blood pressure at arteriole end of capillaries (5.3kPa) forces
water out
•
• This hydrostatic pressure must be greater than the osmotic
pressure drawing water in.
• Plasma Proteins stay in capillaries (so low ψ) and the
hydrostatic pressure keeps dropping as the blood passes
through the capillary beds.
44
45
• At venular end, pressure has dropped to
less than that of the osmotic effect of the
proteins (1.3kPa)
• Water drawn back in to capillaries
(99% of it anyway)
• Excess fluid and some waste products like
urea enter lymph system and are returned
via that pathway.
46