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Circulatory System
Chapter 37

Why do we need one?
◦ Diffusion is too slow for large multicellular
organisms. They need a transport system.

The heart, blood and vessels make up the
human circulatory system.
Circulatory System
Four-chambered double-pump.
 Left side pumps oxygen rich blood to the
body.
 Right side pumps oxygen poor blood to
the lungs.

Heart
Made of cardiac muscle.
 Pacemaker initiates beat.
 Valves keep blow flowing forward.

◦ Lub-dup sound when they close.

The septum divides the heart into right
and left sides.
The Heart
Circulatory Pathways

Arteries – carry blood away from the
heart.
◦ Thick, elastic walls. Pulse.
◦ Aorta is largest blood vessel in the body.

Veins – carry blood back to the heart.
◦ Thinner walls and less elastic.
◦ Veins have valves.

Capillaries - exchange of materials.
◦ Walls are one cell thick.
◦ Every cell touches a capillary.
Blood Vessels
Section
37-1
Vein
Artery
Endothelium
Arteriole
Capillary
Venule
Connective
tissue
Connectiv
e tissue
Smooth
muscle
Smooth
muscle
Endothelium
Endothelium
Valve





Fluid tissue that bathes all
cells of the body.
Carries nutrients and
oxygen to the cells and
wastes and carbon dioxide
away from the cells.
Helps regulate body
temperature.
Some components help
fight disease.
Composed of plasma and
cells.
Blood
Liquid part.
 Mostly water.
 Carries dissolved
carbon dioxide,
nutrients, wastes,
hormones,
antibodies, vitamins,
salts and various
proteins.

Plasma

Red blood cells
(erythrocytes)
◦ Carry oxygen; most
numerous; no nuclei

White blood cells
(leukocytes)
◦ Fight disease; less
numerous; multinucleate

Platelets
(thrombocytes)
◦ Clot the blood
Blood Cells
Figure 37-10 Blood Clotting
Section
37-2
Break in Capillary
Wall
Blood vessels injured.
Clumping of Platelets
Clot Forms
Platelets clump at the
site and release
thromboplastin.
Thromboplastin converts
prothrombin into
thrombin..
Thrombin converts
fibrinogen into fibrin,
which causes a clot. The
clot prevents further loss
of blood..
Network of vessels that return fluid back
to the blood.
 Lymph nodes filter bacteria and microbes
from the fluid.
 The thymus gland in the neck matures T
lymphocytes.
 The spleen removes damaged blood cells
from circulation.

Lymphatic System
Section
37-2
Superior
vena cava
Thymus
Heart
Thoracic
duct
Spleen
Lymph
nodes
Lymph
vessels
The Respiratory System
Chapter 37
Cellular respiration – the release of
energy stored in food. Takes place in
mitochondria.
 Breathing – exchange of gases.

Respiration
Basic function is to exchange oxygen for
carbon dioxide.
 Pathway of airflow:

◦
◦
◦
◦
◦
◦
◦
Nose
Pharynx
Larynx
Trachea
Bronchi
Bronchioles
Alveoli
Human Respiratory System
Figure 37-13 The Respiratory System
Section
37-3
Line the entire respiratory passageway.
 Filters and moistens air.

Cilia and Mucus

Oxygen and carbon dioxide exchange
places by diffusion in both the lungs and
the body cells.
Gas Exchange
Figure 37-14 Gas Exchange in the Lungs
Section
37-3
Alveoli
Bronchiole
Capillary
Active phase – chest muscles and
diaphragm contract; chest cavity
increases in size; air rushes in.
 Passive phase – muscles relax; chest
cavity decreases in size; air is forced out.

Breathing
Figure 37-15 The Mechanics of Breathing
Section
37-3
Air
exhale
d
Air
inhale
d
Rib cage
lowers
Rib cage
rises
Diaphragm
Diaphragm
Inhalation
Exhalation
Figure 37-15 The Mechanics of Breathing
Section
37-3
Air
exhale
d
Air
inhale
d
Rib cage
lowers
Rib cage
rises
Diaphragm
Diaphragm
Inhalation
Exhalation