The Heart and
Circulatory
System
• Our circulation is
a “double loop”.
• Blood must pass
through the
heart twice in
order to
complete the
circuit.
THE HEART
• The APEX of the heart is where the APICAL
•
•
HEARTBEAT can be heart. It is in the 5th
intercostal space, about 4” (10 cm) to the left,
midclavicular.
The superior left corner is deep to costal
cartilage #2, 1” to the left of midsternum.
The inferior right corner is 1” to the right of
midsternal, deep to costal cartilage #6.
• The final placement of the heart would
require an axis placed:
1. Tilted to the left
2. Tilted anteriorly
3. Rotated so the anterior side is to the left.
Heart Chambers
• Anatomically, the heart has 4 chambers.
• Functionally, the heart has 2 chambers or
pump circuits.
• The top chambers are ATRIA (singular-
atrium).
• The bottom chambers are VENTRICLES.
• The walls of the atrium are much thinner
compared with the ventricles.
• Topograhically, there is a small flap of
tissue called the AURICLE.
• Connected to the chambers are large
vessels: vena cavae, pulmonary arteries
or trunk, pulmonary veins, and the aorta.
Sheep Heart – Anterior View
1. Right Auricle
2. Right Ventricle
Brachiocephalic Artery
3.
(Oxygenated)
4. Aortic Arch (Oxygenated)
Pulmonary Artery
5.
(Deoxygenated)
6. Left Auricle
7. Interventricular Sulcus
8. Left Ventricle
Brachiocephalic Artery
1.
(Oxygenated)
Aortic Arch
2.
(Oxygenated)
Openings for
3. Pulmonary Veins
(Oxygenated)
Opening for Inferior
4. Vena Cava
(Deoxygenated)
5. Left Ventricle
Opening for Superior
6. Vena Cava
(Deoxygenated)
• If we look at the heart from the anterior
side, we the right side of the heart.
• Blood returns to the heart (right atrium)
via the SUPERIOR and INFERIOR VENA
CAVAE and CORONARY SINUS.
• From the right atrium
•
it is pumped into the
RIGHT VENTRICLE.
It must pass through
the TRICUSPID VALVE
(which has 3 cusps)
which is a
ATRIOVENTRICULAR
VALVE.
• From the right ventricle, the blood then
passes through the PULMONARY
SEMILUNAR VALVE and into the
PULMONARY TRUNK.
• The pulmonary trunk carries blood to the
lungs for re-oxygenation in the alveoli.
• All the valves are made of connective
tissue and function to prevent backflow of
blood.
• Problems with the valves cause a disorder
called PROLAPSE or MURMUR.
• Blood returns to the LEFT
•
•
ATRIUM via the
PULMONARY VEINS.
There are 2 pulmonary
veins from each lung.
The blood next passes
through the BISCUPID (2
cusps) or MITRAL VALVE
on its way to the LEFT
VENTRICLE.
• From the left ventricle, blood passes through the
AORTIC SEMILUNAR VALVE into the AORTA.
• To remember that the TRICUSPID VALVE comes
before the BICUSPID VALVE, remember the
saying:
“Try before you buy”
VALVES
• The valves open passively during
ventricular relaxation.
• They close passively during ventricular
contraction.
• The CHORDAE TENDINEAE connect the
edge of the AV valve to the PAPILLARY
MUSCLE.
Chordae
• These muscles prevent the valves from
being forced closed in reverse.
• The chords contract when the papillary
muscles pull on them.
• The papillary muscles DO NOT cause the
valves to open or close.
• The SEMILUNAR VALVES are found
between the ventricles and the large
arteries leaving the ventricles.
• They are TRICUSPID in structure. Heart
sounds are caused by the closing of these
valves.
The Semilunar Valves
1
2
3
• SUMMARY:
4 chambers
4 valves
4 vessels
ARTERIES=carry blood AWAY from the heart.
VEINS = carry blood TOWARD the heart.
9. Right Atrium
10. Right Ventricle
11. Left Atrium
12. Left Ventricle
13. Papillary Muscles
14. Chordae Tendineae
15. Tricuspid Valve
16. Mitral Valve
17. Pulmonary Valve
1. Right Coronary
2. Left Anterior
Descending
3. Left Circumflex
4. Superior Vena Cava
5. Inferior Vena Cava
6. Aorta
7. Pulmonary Artery
8. Pulmonary Vein
CIRCULATION
• The importance of circulation is the movement
•
•
of materials into and out of the cells.
Cells require O2 and need to get rid of CO2.
This is accomplished by two processes: BULK
FLOW and DIFFUSION.
Bulk Flow
• Bulk flow is the movement of blood over
significant distances in a short period of
time. Accomplished by pressure
gradients.
• Blood moves from areas of high pressure
to areas of low pressure.
• We establish pressure gradients by using:
1.
2.
3.
4.
heart
gravity
skeletal muscle
smooth muscle
Diffusion
• Diffusion is the random movement of
molecules with net movement from areas
of high concentration to areas of low
concentration.
• It is only effective over short distances.
• It only happens in capillaries.
• This can happen because capillaries are
blood vessels that are only one cell thick.
• Capillaries are the FUNCTIONAL UNIT of
circulation with the cells.
• The circulatory system is a CLOSED
SYSTEM with three main components:
1. heart (bulk flow)
2. vessels (direct flow)
3. blood (used for transport)
Path of Circulation
Heart -> arteries ->
arterioles ->
capillaries ->
venules -> veins ->
heart
• Arterioles are small arteries and have a
lumen diameter of about 0.5 mm. Their
anatomy is the same as arteries.
Anatomy of an Artery
Tunica Media –
middle smooth
muscular layer –
thick in arteries,
thin in veins
Tunica
Aventitia or
Tunica
Externa contain CT and
Vaso Vasorum
Fibrous
tissue layer
Tunica Intimainner lining –
endothelia and
CT
Lumen
• Recall that the arteries have a muscular pump to
•
•
help blood get to the needed body parts.
Veins do not have this pump.
Skeletal muscle contractions help move the
blood upward toward the heart. Also, veins
have VALVES which prevent backflow of blood
(gravity)
• When blood cannot travel back toward the
heart, it can accumulate in the veins. This
causes a dilation of the vein, or VARICOSE
VEINS.
In Review
VEINS
ARTERIES
1. Toward heart CARRY BLOOD Away from heart
2.
3.
4.
2-3 cells thick MUSCULAR LAYER 40 cells thick
Semilunar Valves VALVES
No valves
Decreased
OXYGEN LEVELS
Increased
Categories of Circulation
1. Pulmonary CirculationBlood from right ventricle goes through
the pulmonary trunk to lungs and back
to left atrium.
•
There is much lower hydrostatic
pressure than in the systemic circulation.
• 2. Systemic Circulation
The second major circulatory loop. Blood
leaves the left ventricle and is pumped
throughout the body. It ends up in the right
atrium.
This loop includes blood supply to the GI tract
to help with nutrient absroption.
Collateral Circulation
• Allows blood to flow around a blockage.
• Arterioles meet head on in an
ANASTOMOSIS.
• Anastomoses serve as a natural bypass.
Portal Circulation
• Veins from pancreas, spleen, small
intestine, and stomach empty into the
portal vein in the liver.
• After excess glucose is removed and
detoxification occurs, blood enters the
hepatic portal vein to be returned to the
vena cava and the general circulation.
Fetal Circulation
- needed because the fetal lung is not functional.
Fetal oxygen source is the PLACENTA.
- blood from mother and fetus do not mix,
but rather is in 2 adjacent capillary beds.
- permeable materials can pass through the
adjacent capillary beds causing the fetus to be
exposed to whatever is in the mother’s
bloodstream.
Blood flows from the placenta to the fetus via on
UMBILICAL VEIN.
- The UV has the most oxygen rich blood for
the fetus.
- This vein branches with one part going to
the FETAL LIVER and the other going to the
INFERIOR VENA CAVAE (DUCTUS VENOSIS).
- Blood then enters the right atrium. Blood so
far is MIXED (both oxygenated and
deoxygenated).
• This blood is then combined with
deoxygenated blood from the coronary
sinus and superior vena cavae.
• There is a hole (foramen) between the
atria. This is called the FORAMEN OVALE.
• There is also a linkage between the
pulmonary artery and the aorta. This is
called the DUCTUS ARTERIOSUS.
• The UMBILICAL ARTERIES branch from
the INTERNAL ILIAC ARTERIES found in
the pelvis. The ILA’s are branches of the
COMMON ILIAC ARTERIES which are the
terminal branches of the aorta.
Coronary Circulation
- heart has a separate circulation.
- these coronary vessels are the ones treated
in “bypass” surgery.
- CORONARY SULCUS or ATRIOVENTRICULAR
GROOVE
- INTERVENTRICULAR SULCUS.
- The coronary arteries and veins are located
within these grooves.
Coronary
Circulation
• Each blood cell must pass through the
heart twice in order to complete a full
circulatory circuit.
Lymphatics (in general)
• The lymphatic system is a system that collects and
•
•
•
recycles fluids that have leaked from the circulation. It
is also involved in fighting infections.
It is made of a series of LYMPH VESSELS and tiny beanshaped NODES.
Lymph tissue is located in various parts of the body
including; thymus, tonsils, spleen, and bone marrow.
The lymph tissue is eventually drained into the vena
cava to go into the right atrium.
What is carried in the blood?
• Respiratory gasses (oxygen and CO2)
• Nutrients
• Hormones
• Defense cells/Immune cells
• Repair cells
It also regulates body temperature by
carrying warmth from the center of the
body to the periphery.
Blood Anatomy
• Blood is composed of
two parts.
1. FORMED
ELEMENTS
- cellular component
2. PLASMA
- liquid component
Centrifuge
• Machine which spins tubes of blood to
separate the components.
Plasma
WBC’s
RBC’s
BUFFY COAT
Plasma
• A straw-colored, sticky fluid.
• Contains over 100 different kinds of molecules.
• Contains three proteins:
a. Albumin – important in keeping osmotic
pressure constant. Also important in wound
healing.
b. Globulins – important for antibody
production and transport of other molecules.
c. Fibrinogen – important for blood clotting
Formed Elements
• These are the “blood cells”
1. Erythrocytes
a. RBC’s
b. Carry oxygen
c. No nuclei or organelles
d. % of blood volume that contain
erythrocytes is known as the
HEMATOCRIT.
e. cytoplasm is filled with HEMOGLOBIN.
f. Hemoglobin is the oxygen carrying protein.
g. Pick up oxygen in the lung capillaries and release
carbon dioxide.
h. Spherical shaped
i. When the shaped changes, individual cells have
difficulty entering and traveling through the capillary
lumen.
j. Efficient oxygen transporters as they do not use any
of the oxygen they transport. This is because they do
not have organelles (mitochondria). The erythrocytes
must get their energy through anaerobic means.
k. Live for 120 days. Therefore, it is
easy to use them for clinical testing. For
example, glucose binds to the RBC. The
more glucose that is bound to the RBC,
the higher the patients average blood
sugar levels. HbA1C is a measurement of
how much sugar is bound to the RBC. If
this test is performed every 120 days,
physicians can determine the range of
blood sugar control.
LEUKOCYTES
•
•
•
•
White Blood Cells (WBC)
Crucial to the bodies defense against disease.
Have all the organelles and nuclei of a true cell.
Leukocytes perform their function outside the circulatory
system. They function in the connective tissue (where
infections usually occur).
• When a leukocyte senses an infection, it moves out of
the circulation by squeezing out between the endothelial
cells which line the blood vessels. This is known as
DIAPEDESIS.
• Once outside the circulation, the WBC’s use amoeboid
motion to find the offending organism.
5 Types of Leukocytes
Granulocytes
1. Neutrophils – most abundant
- lobuated nuclei
- “Polymorphonuclear
Leukocytes” (PMN’s)
- “Polys” or “Segs”
- phagocytize and
destroy bacteria.
2. Eosinophils
-
rarely found
nuclei with only 2 lobes
stain red with acidic dye “Eosin”
fight parasites and parasitic diseases
3. Basophils
- rarest of all WBC’s
- nuclei stain dark with basic stain
- secrete histamine to mediate allergic
reactions.
• Agranulocytes
1. Lymphocytes
- most important cell in the immune system
- function in the connective tissue, not the
bloodstream
- important for fighting infection
- substances that cause a reaction from a
lymphocyte is called an ANTIGEN.
- 2 types of lymphocytes: T-cells (kill organisms
directly)
B-cells (become mast
cells
2. Monocytes
- become macrophages which ingest a
wide variety of foreign debris
CLINICAL CORELLATION
A complete blood count (CBC)
- Quantifies the various cell types found in
the blood.
- A DIFFERENTIAL identifies the percentage
of each type of leukocyte.
Platelets
• Known as THROMBOCYTES
• Function to plug small tears in the walls of the
•
•
•
blood vessels to limit bleeding.
Adhere to exposed collagen at the edges of a
tear.
Release THROMBOPLASTIN, a molecule that
initates clotting.
Platelets adhere only to damaged blood vessels.
When a clot develops or persists in an intact
blood vessel, a THROMBUS results.