The Heart and General Circulation
rev 6-11
• The heart and blood vessels are collectively
known as the cardiovascular system
• The heart is a hollow muscular organ whose
contractions creates the force and pressure which
moves blood throughout our body
• The heart is a pump
• It secretes hormones that help regulate blood
pressure and the body’s fluid and electrolyte
balance.
1
Lab 9-The Heart and
General Circulation
• Arteries carry blood away from the heart
• Veins carry blood to the heart
• Arteries and veins are connected to each other by
capillaries
• The right side of the heart receives returning
blood that is low in oxygen (deoxygenated)
• Blood moves from the right side of the heart to the
lungs where it becomes oxygenated.
• Blood is returned to the left side of the heart
which circulates it throughout the body
2
Lab 9-The Heart and General Circulation
Anatomy of an Artery, Vein and
Capillary
• Both arteries and veins have an inner layer of
simple, squamous epithelium cells, a middle layer
of smooth muscle, and an outer connective layer.
• Arteries have thicker muscular layers than veins
because they must be able to withstand the high
pressures generated by the heart.
• Veins are thinner walled and have valves to help
keep the blood moving, against gravity, to the
heart.
3
Lab 9-The Heart and
General Circulation
– Vein valves prevent the backflow of blood.
• The smallest arteries are called arterioles; the
smallest veins are called venules. These connect
via capillaries.
• All blood vessels except capillaries have smooth
muscles in their walls.
• Capillaries are a thin layer of squamous cells
which allows for exchange of nutrients, wastes
and gases.
4
Lab 9-The Heart and
General Circulation
• Layers of an artery
– innermost layer is the endothelium
• is a layer of flattened, squamous epithelial cells
which fit so closely together that they create a slick
surface so that blood can flow smoothly.
– middle layer which is primarily smooth
muscle with elastic connective tissue
– outermost layer is a supporting layer of
connective tissue which anchors vessels to
surrounding tissues
5
Lab 9-The Heart and
General Circulation
• Veins
– like the walls of arteries, the walls of veins
consist of 3 layers of tissue.
• Outer 2 layers are much thinner than those of
arteries
• veins have larger diameters than arteries
– the pressure in veins is much lower than that in
arteries which is why their walls are not as
strong as arteries
6
Lab 9-The Heart and
General Circulation
– veins can act as a blood volume reservoir
– the larger diameter of veins allows them to
stretch to accommodate large volumes of blood
at low pressures
– because veins can stretch, it is more difficult for
them to return blood to the heart against the
force of gravity
– people who spend a lot of time on their feet
may get varicose veins because of this
7
Lab 9-The Heart and
General Circulation
• Factors which help veins to return blood to
heart
– contraction of skeletal muscles
• as we move and muscles contract and relax,
they press against veins and help push blood
to the heart
• one way valves in the veins
8
Lab 9-The Heart and
General Circulation
– the work of the skeletal muscles helps the
valves pump blood. This is called a skeletal
muscle pump
– movements associated with breathing also help
pump blood. This is called a respiratory pump
and helps to push blood from the abdomen to
the chest and to the heart.
• when we breathe, there are pressure changes
in the thoracic and abdominal cavities
• during inhalation, abdominal pressure
increases and squeezes abdominal veins
9
• simultaneously, pressure within the thoracic cavity
decreases which dilates the thoracic veins and thus
propels the blood.
The Heart
• External anatomy--heart has blood vessels
attached to it
– the large vessels are the
• aorta which transports blood away from the
heart to the entire body.
• the pulmonary trunk (pulmonary vein and
artery) which transports blood to and from
the lungs.
10
Lab 9-The Heart and
General Circulation
– The superior and inferior vena cava which
return blood to the right atrium
• the 4 chambers of the heart are the
– 2 atria: the right atrium and the left atrium
– 2 ventricles: the right and left ventricles
• blood enters the heart through the right atrium,
flows through an atrioventricular valve into the
right ventricle
11
12
Lab 9-The Heart and
General Circulation
• From the right ventricle, to a pulmonary valve to
the pulmonary artery to the lungs
• oxygenated blood returns to the heart through the
pulmonary vein
• and enters the left atrium
• flows through another atrioventricular valve to the
left ventricle
• then through another valve to the aorta to the
entire body
13
Lab 9-The Heart and
General Circulation
• the heart muscle has its own supply of blood
vessels: coronary arteries and coronary veins (see
pictures on page 119 of lab manual)
• All of the chambers of the heart fill at the same
time
• note that the pulmonary circulation has the oxygen
level of the arteries and veins reversed
14
Lab 9-The Heart and
General Circulation
– the heart pumps 2 “circuits” at the same time-• the right ventricle to the pulmonary trunk
• and the left ventricle to the entire body
– the outer wall of the left ventricle is thicker
than the right ventricle
• this ventricle does more work than any other
chamber--it must overcome the pressure of
the aorta in order to pump blood into it
15
REMINDER
• Look at the bulleted lists on lab manual pages 120
and 121
– you will need to know where these items are
located for the lab test
• Use the models and charts to help you locate
these; don’t try to find them in the fetal pig
16
Lab 9-The Heart and
General Circulation
In general, blood vessels are named for the body
cavity which they pass through
• The aorta modifies its name as it enters different
body areas
– aortic arch as it leaves heart
– thoracic aorta: where aorta straightens out
– abdominal aorta: when aorta goes through the
diaphragm
– after this, the aorta splits to go into each leg; it
now becomes the femoral artery
17
Lab 9-The Heart and General Circulation
• Main arterial branches of the aorta (see page 126)
– brachiocephalic (first branch off aorta) artery
– carotid artery
– subclavian (underneath clavicle) artery
– renal artery (kidney)
– external/internal iliac (ileum=hip bones) arteries
– femoral artery
18
Lab 9-The Heart and
General Circulation
• Major veins(see page 127)
– superior vena cava
– inferior vena cava (is the major vein in thoracic,
pelvic, and abdominal cavities)
– jugular vein
19
REMINDER
• Pathway of circulation; you need to know this
– follow instructions on page 121
• Do the sounds of the heart and the heart rate
activities (page 121)
20
Lab 9-The Heart and
General Circulation
Functional Anatomy
• Contraction of the heart muscle is called systole
– during systole, blood is pumped out of, or
ejected from, the heart into the circulatory
system
• Relaxation of the heart muscle is called diastole
– during diastole, the heart fills with blood
21
Lab 9-The Heart and General Circulation
• Blood Pressure
– When blood pressure is taken,
• the higher number is the systolic pressure
• the lower number is the diastolic pressure
• You will be taking each other’s blood pressure
with an automatic blood pressure cuff
• wrap the cuff snugly around your partner’s arm(with
the velcro side facing you, not your partner)
• the cuff is placed around the upper part of the arm
so the bottom edge rests immediately above the
elbow
22
Lab 9-The Heart and General Circulation
REMINDER page 1 of 3:
1. Use the sheep heart and the models to view
internal anatomy. Learn all the heart structures on
the models. Remember to label figure 13.5 to
include the heart chambers--atria and ventricles.
2. Locate all blood vessels from the bulleted lists on
pages 120-121 on the models. Use the figures on
lab manual pages 124-125 to help you.
3. See the instructions on page 121 for the pathway
of circulation and follow this activity.
23
REMINDER page 2 of 3:
4. Do the sounds of the heart and the heart rate
activities
5. Perform the blood pressure activities on pages
124-125.
6. We will also begin dissecting the fetal pig today.
Remember that everyone needs to participate in
the dissection.
a. Tie long hair back so it doesn’t mix with the
inside of the pig when you bend down to look
at it.
24
REMINDER page 2 of 3:
7. You need to locate the following endocrine
glands: thyroid, thymus, and pancreas (see
diagram on page 104 of the lab manual).
a) DO NOT locate the adrenal glands; they are
very hard to find.
b) Remember to use Table 11.1 to help you learn
about these glands, their hormones and the
function of these hormones.
25