Circulatory
System
A general tour
Exchange of materials

Animal cells exchange material across their cell
membrane
 Fuel
for energy
 Nutrients
 Oxygen
 Waste (urea, CO2)

If you are a 1-cell
organism, this is easy!
 Diffusion

If you are multicellular, it becomes more difficult
Overcoming limitations of diffusion


Diffusion is not adequate for moving material
across more than 1-cell barrier
So … set up a “highway”
CO2
CO2
system to
NH3
NH3
aa
CO2
transport materials!
NH3
O2
CH
aa
CO2
CHO
CO2
O2
NH3
aa
CHO
CH
O2
aa
NH3
CO2
NH3
CO2
NH3
NH3
CO2
CH
CO2
NH3
CO2
aa
O2
CHO
CO2
aa
In circulation …

What needs to be transported?
 Nutrients

& fuels
From digestive system
 Respiratory

O2 & CO2 from & to gas exchange systems: lungs/gills
 Intracellular

Water, salts, nitrogenous wastes (urea)
 Protective
agents
Immune defenses


waste
Waste products from cells


gases
White blood cells & antibodies
Blood clotting agents
 Regulatory
molecules
 hormones
Circulatory systems

All animals have:
 Circulatory
fluid = “blood”
 Tubes = blood vessels
 Muscular pump = heart
open
hemolymph
closed
blood
Vertebrate cardiovascular system

Chambered heart
 Atria
= receive blood
 Ventricles = pump out blood

Blood vessels
 Arteries
= carry blood
away from heart

Arterioles
 Veins
= return blood to
heart

Venules
 Capillaries
= thin wall,
exchange/diffusion with cells

Capillary beds = networks of capillaries
Blood vessels
arteries
arterioles
capillaries
venules
veins
Arteries: built for high pressure pump

Thick walls
 Provide
strength for high pressure pumping
of blood (80-120 mm Hg)

Narrow diameter/lumen

Elasticity
 Elastic
recoil helps
maintain blood pressure
even when heart relaxes




Middle layer = elastin
Outer layer = collagen
No valves
No exchange with
cells
Veins: built for low pressure flow


Thinner walls
Wider diameter/lumen
 Blood
travels back to heart at low velocity &
pressure
 Lower pressure (<10 mm Hg)

Distant from heart



Blood must flow by skeletal muscle
contractions when we move
Squeeze blood through veins
Valves
 In
larger veins, one-way valves
allow blood to flow only toward
the heart

No exchange with cells
Capillaries: built for exchange

Very thin walls

Lack 2 outer walls
 Only endothelium


Enhances exchange across capillary
Diffusion
 Exchange


occurs between blood & cells
No valves
Some capillaries have pores

Fenestrations
 Allows plasma & certain other
cells/molecules to “leak” into
tissue
Controlling blood flow to tissues

Blood flow in capillaries controlled by precapillary sphincters
 Supply
varies as blood is needed
 After a meal, blood supply to digestive tract increases
 During strenuous exercise, blood is diverted from
digestive tract to skeletal muscles

Capillaries in brain, heart, kidneys & liver usually
filled to capacity
Why?
sphincters open
sphincters closed
Exchange across capillary walls
Fluid & solutes flows
out of capillaries to
tissues due to blood
pressure

Lymphatic
capillary
Interstitial fluid flows
back into capillaries
due to osmosis
 plasma proteins  osmotic
pressure in capillary
“bulk flow”
BP > OP
BP < OP
Interstitial
fluid
What about
edema?
Blood
flow
85% fluid returns
to capillaries
Capillary
Arteriole
15% fluid returns
via lymph
Venule
Lymphatic system

Parallel circulatory system

Transports white blood cells


Defends against infection
Collects interstitial fluid & returns to
blood


Maintains volume & protein concentration
of blood
Drains into circulatory system near
junction of vena cava & right atrium
Lymphatic system
Production & transport of WBCs
Traps foreign invaders
lymph vessels
(intertwined amongst blood vessels)
lymph node
Mammalian
circulation
systemic
pulmonary
systemic
What do blue vs. red areas represent?
Mammalian heart
to neck & head
& arms
Arteries that
supply blood
specifically to the
heart
Coronary arteries
Coronary arteries
bypass surgery
Heart valves

4 valves in the heart

Flaps of connective tissue
 Prevent backflow

Atrioventricular (AV) valves

Between atrium & ventricle
 Keeps blood from flowing back into
atria when ventricles contract
 Tricuspid & bicuspid/mitral valves

Semilunar valves

Between ventricle & artery
 Prevents backflow from arteries into ventricles while they
are relaxing
 Aortic & pulmonary valves
Pulmonary Artery
Aorta
Pulmonary Vein
Vena Cava
Right Atrium
Left Atrium
Pulmonary
valve
Aortic valve
Mitral valve
Tricuspid
valve
Right
Ventricle
Left Ventricle
Septum
Our circulatory system is a double circulatory system.
Lungs
the right side of
the left side of
the system
the system
deals with
deals with
oxygenated
deoxygenated
blood.
blood.
Body cells
pulmonary artery
pulmonary vein
lungs
head & arms
aorta
main vein
Right
Left
liver
digestive system
kidneys
legs
What about blood?

There are 4 main components to blood:
 Erythrocytes

Red blood cells

Oxygen transport
 Leukocytes

White blood cells


Non-specific immunity
Lymphocytes

Specific immunity
 Platelets

Blood clotting
 Plasma

Fluid medium
Red blood cells
a biconcave disc that is
round and flat without a
nucleus
contain hemoglobin, a
molecule specially designed
to hold oxygen and carry it
to cells that need it.
can change shape to an
amazing extent, without
breaking, as it squeezes
single file through the
capillaries.
White blood cells
there are many different types and
all contain a big nucleus.
the two main ones are the
lymphocytes and the macrophages.
macrophages ‘eat’ and digest microorganisms .
some lymphocytes fight disease by making antibodies to destroy
invaders by dissolving them.
other lymphocytes make antitoxins to break down poisons.
Platelets
Platelets are bits of cell
broken off larger cells.
Platelets produce
tiny fibrinogen
fibres to form a net.
This net traps other
blood cells to form a
blood clot.
Blood clotting
Damaged cells release
chemical signals called
clotting factors
Clotting factors
convert prothrombin
(zymogen) into
thrombin
Thrombin converts
fibrinogen into fibrin
Stops blood flow & helps prevent
pathogens from entering
Clotting factors
cause platelets to
become sticky,
resulting in a clot at
the injury site
Plasma

Also contains:
 Carbon
A strawcoloured
liquid that
carries the
cells and the
platelets
which help
blood clot.
dioxide
 Glucose
 Amino acids
 Proteins
 Minerals
 Vitamins
 Antibodies
 Hormones
 Waste (like
urea)
 Heat
Atherosclerosis

Hardening & narrowing of the arteries
 Due
to deposit of plaque
 High blood pressure damages artery wall

Causes chronic inflammation
 Accumulation
of lipids, cholesterol, debris & calcium
 Fatty deposits (atheromas) reduce diameter of lumen
(stenosis) and elasticity of the artery
 May lead to the formation of
clots & blockages in the artery
 Major cause of heart attacks,
strokes, and peripheral
vascular disease
Atherosclerosis

Risk factors for coronary heart disease
 Lack
of exercise
 Diet
 Obesity
 Genetics
 Gender

Males at greater risk due to low estrogen levels
 Smoking
Nicotine causes vasoconstriction
 Increases blood pressure

 Age
Bloody well ask
some questions, already!