1. CIRCULATORY
SYSTEM

2. The Heart
 4 chambers
 Located between the
lungs
 2/3 of heart left of
midline
 Apex points downward
& contacts the
diaphragm
 It lies in the pericardial
cavity

3. The Heart
 It is separated from the other organs by a double-
layered membrane = Pericardium
 The Pericardium is composed of a Fibrous
Pericardium & a Serous Pericardium.
The serous pericardium has 2 parts:
 1. Parietal layer - attached to the back of the fibrous
pericardium
 2. Visceral layer (epicardium) - attached to the heart
muscle
 These two are separated by a fluid filled space =
pericardial cavity.

4. The Heart Wall
 A. Epicardium -
outermost, = Visceral
layer of the serous
pericardium

5. Heart Wall
 B. Myocardium -
middle, = Cardiac
muscle cells (very
thick)

6. The Heart Wall
 C. Endocardium -
innermost, forms
valves, & is continuous
with the endothelium of
the blood vessels that
enter & leave the heart

7. Chambers
 4 chambers
 2 upper: Lt. & Rt. Atrium
 2 lower: Lt. & Rt.
Ventricle

8. Valves
 4 valves
 2 Atrioventricular (AV)
Valves
 Rt. AV valve = tricuspid
 Lt. AV valve = bicuspid,
mitral
 2 semilunar valves: found
at the base of 2 large
vessels leaving the heart
= Pulmonary & Aortic
valves

9. Blood flow

10. Blood Flow
 1. Rt. Atrium: receives
deoxygenated (venous)
blood from 3 vessels;
 A. Superior vena cava -
blood from above the
heart
 B. Inferior vena cava -
blood from below the
heart
 C. Coronary sinus -
blood from the heart
muscle

11. Blood Flow
 2. Blood flows through
Rt. AV valve into Rt.
Ventricle (the flaps of AV
valves are held in place
by Chordae Tendineae
& Papillary Muscles to
prevent back flow)

12. Blood Flow
 3. Rt. Ventricle contracts
& blood exits through
the Pulmonary
Semilunar valve. It
enters the Pulmonary
trunk which divides into
Lt. & Rt. Pulmonary
arteries. Blood goes to
lungs (carbon dioxide
out, oxygen in)

13. Blood Flow cont.
 4. Oxygenated blood
returns from the lungs
through the
Pulmonary veins to
the Lt. Atrium

14. Blood Flow
 5. Blood flows
through the Lt. AV
valve (bicuspid,
mitral) to the Lt.
Ventricle

15. Blood Flow
 6. Lt. Ventricle
contracts & blood exits
through the Aortic
Semilunar valve &
enters Ascending
Aorta.

16. Coronary circulation (Blood flow to Heart
Muscle)
 First vessels off of the
Ascending Aorta = Lt. & Rt.
Coronary Arteries

17. Coronary Circulation cont.
 The blood returns from the
heart muscle via 2 major
veins
 1. Great Cardiac vein:
brings deoxygenated blood
back from the anterior heart
wall
 2. Middle Cardiac vein:
brings deoxygenated blood
back from the posterior
heart wall.
 Both vessels empty into the
Coronary Sinus (a large
vein on back of heart). It
empties into Rt. Atrium

18. Conduction system
 An electrical system. It
determines the rate &
rhythm of the heartbeat
 1. Sinoatrial node (SA node,
pacemaker) - Neurons fire
at 70/80 beats per minute,
causes atria to contract
 2. Atrioventricular node (AV
node) - neurons fire at
40-50 beats per minute;
typically the SA node
overrides it, but if SA node
is not functioning it will
ultimately cause ventricles
to contract at a slower rate.

19. Conduction System
 3. Atrioventricular Bundle
(Bundle of His) - conducts
impulses between ventricles
 4. The AV Bundle divides into
lt & rt Bundle Branches which
go to the ventricles.
 5. Purkinje fibers - deliver
impulses directly to the
myocardium of the ventricles.

20. Blood – connective tissue with fluid
matrix
 A. Fluid = plasma
 B. Blood cells = formed
elements
 1. Red blood cells
(RBC's) =
ERYTHROCYTES
 a. Flattened, biconcave,
anucleated discs
 b. Life span - 120 days
 c. Function: transport
oxygen & carbon dioxide
bound pigmented protein
= hemoglobin

21. Blood cont.
 2. White blood cells
(WBC's) =
LEUKOCYTES
 a.granulocytes
 i. eosinophils
 ii. Basophils
 iii. Neutrophils

22. Blood cont.
 2. White blood cells
(WBC's) =
LEUKOCYTES
 b. Agranulocytes
 i. Monocytes
 ii. Lymphocytes

23. Blood cont.
 3. Thrombocytes =
PLATELETS; not cells.
Cytoplasmic fragments
of megakaryocytes.
Assists in blood clot
formation.

24. Hemopoiesis = Blood Cell formation.
Occurs in red bone marrow.
 A. Erythropoiesis =
RBC formation
 B. Leukopoiesis = WBC
formation
 C. Thrombopoiesis =
platelet formation

25. Blood vessels: blood flow
Blood flows from the heart through
progressively narrowing vessels;
artery ->arteriole -> capillary
And returns through progressively enlarging
vessels;
venules -> vein-> heart

26. Blood vessels
 Structure: arteries and veins
have 3 tunics
 1. Tunica Externa
(adventitia) - Outermost,
loose connective tissue, this
is the thickest layer in veins
 2. Tunica Media - middle,
smooth muscle layer, this is
the thickest layer in arteries
 3. Tunica Intima - innermost
 a. Endothelium - simple
squamous + c.t.
 b. Subendothelial layer - c.t.

27. Arteries (carry blood away from heart)
 Elastic - large amount
of elastin expandable
 Muscular - tunica
media is predominantly
smooth muscle.
 There is an elastic
lamina on each face of
the tunica media

28. Arterioles -
 Smallest, tunica media very thin (<10 layers)

29. Capillaries
 "Functional units" of circulatory system, very
thin-walled, allows for exchange of gases,
nutrients, & waste products.
 Composed of the Tunica Intima only

30. Venules
 Usually lack a tunica media. They have the
other two tunics

31. Veins
 Carry blood to the
heart) All 3 tunics
present. Veins have a
very
 Low pressure, The
blood flow through
them is dependent on:
 A. Contraction of
surrounding musculature
= Skeletal muscle "pump"
 B. One-way valves