5. THE CIRCULATORY SYSTEM
I.THE CIRCULATORY SYSTEM IS AN
INTERNAL TRANSPORT SYSTEM WITH 3
COMPONENTS:
BLOOD IS A FLUID TISSUE COMPOSED OF
WATER, SOLUTES AND CELLS.

6. B. THE HEART IS A MUSCULAR PUMP THAT
GENERATES PRESSURE TO KEEP THE
BLOOD FLOWING.
C. BLOOD VESSELS ARE TUBES THROUGH
WHICH BLOOD IS TRANSPORTED.

7. II. BLOOD:
A. FUNCTIONS OF THE BLOOD:
CARRIES OXYGEN AND NUTRIENTS TO
CELLS.
2. CARRIES WASTES AND SECRETIONS
AWAY FROM CELLS.

8. 3. CONTAINS PHAGOCYTIC CELLS THAT
FIGHT INFECTION.
4. HELPS STABILIZE INTERNAL PH.
5. EQUALIZES BODY TEMPERATURE.

9. B. BLOOD COMPONENTS:
PLASMA- MOSTLY WATER, SOME
PROTEINS, TRANSPORT LIPIDS, VITAMINS,
IONS, GLUCOSE, HORMONES AND
DISSOLVED GASES.

10. 2. ERYTHROCYTES (RED BLOOD CELLS =
RBC’S) – BICONCAVE CELLS THAT CON-
TAIN HEMOGLOBIN THAT BINDS WITH
OXYGEN. NO NUCLEI, DEVELOP IN BONE
MARROW, LAST ~120 DAYS.

11. 3. LEUKOCYTES – (WHITE BLOOD CELLS)
a. LEUKOCYTES REMOVE DEAD OR WORN-
OUT CELLS AND PROTECT AGAINST
INVADING MICROBES.
b. THEY ARE DERIVED FROM STEM CELLS
IN THE BONE MARROW.
-THERE ARE 5 TYPES OF LEUKOCYTES:

12. 1.MONOCYTES AND NEUTROPHILS ARE
PHAGOCYTES – THEY DIGEST PATHOGENS.
2. BASOPHILS AND EOSINOPHILS ARE IN-
VOLVED IN INFLAMMATORY RESPONSE.
3. LYMPHOCTYES –FIGHT OFF INFECTION,
MAJOR COMPONENT OF IMMUNITY.

13. 4. PLATELETS- FRAGMENTS OF CELLS PRODUCED IN THE BONE MARROW, NO
NUCLEUS, NEEDED FOR BLOOD CLOTTING.
Plasma 55%
Constituent
Major functions
Cellular elements 45%
Water
Solvent for
carrying other
substances
Cell type
Number
Functions
per µL (mm3) of blood
Erythrocytes
(red blood cells)
Ions (blood electrolytes)
5–6 million
Transport oxygen
and help transport
carbon dioxide
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Osmotic balance,
pH buffering, and
regulation of
membrane
permeability
Separated
blood
elements
Leukocytes
(white blood cells)
Defense and
immunity
5,000–10,000
Plasma proteins
Albumin
Osmotic balance,
pH buffering
Lymphocyte
Fibrinogen
Clotting
Basophil
Immunoglobulins
(antibodies)
Defense
Eosinophil
Substances transported by blood
Neutrophil
Monocyte
Nutrients (such as glucose, fatty acids,
vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones
Platelets
250,000–
400,000
Blood clotting

14. III. CIRCULATION:
BLOOD IS TRANSPORTED FROM THE
RIGHT SIDE OF THE HEART TO THE LUNGS
IN THE PULMONARY CIRCUIT; THE BLOOD
IS RETURNED TO THE LEFT SIDE OF THE
HEART, FROM WHICH IT IS PUMPED TO
THE REST OF THE BODY.
B. BLOOD TRAVEL FOLLOWS THIS ROUTE:
HEART  ARTERIES ARTERIOLES 
CAPILLARIES  VENULES  VEINS 
HEART.

16. C. THE HUMAN HEART:
THE HEART IS A DURABLE PUMP MADE
OF MOSTLY CARDIAC MUSCLE. IT IS
ENCLOSED IN A TOUGH, FIBROUS SAC
CALLED THE PERICARDIUM. THE HEART’S
CHAMBERS ARE LINED WITH CONNECTIVE
TISSUE AND ENDOTHELIUM.
2. EACH HALF OF THE HEART HAS AN
ATRIUM (RECEIVING) AND VENTRICLE
(PUMPING) CHAMBER.

17. 3. THE CARDIAC CYCLE:
-CONSISTS OF A SEQUENCE OF CON-
TRACTIONS (SYSTOLE) AND RELAXATIONS
(DIASTOLE).
-AS THE ATRIA FILL, THE VENTRICLES ARE
RELAXED. THE ATRIA FILL SIMULTANEOUSLY.

18. -PRESSURE OF THE BLOOD FORCES THE
ATRIOVENTRICULAR VALVES TO OPEN AND
THE VENTRICLES TO FILL.
THE VENTRICLES CONTRACT, THE
ATRIOVENTRICULAR VALVES CLOSE AND
BLOOD FLOWS THROUGH THE SEMILUNAR
VALVES.

19. IN THE “LUB, DUB” HEART SOUND, THE
“LUB” COMES FROM THE CLOSING OF THE
ATRIOVENTRICULAR VALVES AND THE
“DUB” FROM THE CLOSING OF THE
SEMILUNAR VALVES.

20. Pulmonary artery
Aorta
Anterior
vena cava
Pulmonary
artery
Right
atrium
Left
atrium
Pulmonary
veins
Pulmonary
veins
Semilunar
valve
Semilunar
valve
Atrioventricular
valve
Atrioventricular
valve
Posterior
vena cava
Right
ventricle
Left
ventricle

22. 4. EXCITATION FOR A HEARTBEAT IS
INITIATED BY THE SINOATRIAL (SA) NODE,
(ALSO CALLED THE PACEMAKER). THE
ATRIA CONTRACT FORCING THE BLOOD
INTO THE VENTRICLES. NEXT,
THE ELECTRICAL SIGNAL PASSES TO THE
ATRIOVENTRICULAR (AV) NODE.

23. -THE BUNDLES OF HIS AND PURKINJE
FIBERS CONDUCT SIGNALS TO THE
APEX (BOTTOM OR POINT) OF THE
HEART. THE VENTRICLES CONTRACT.

24. SA NODE
AV NODE

25. IV. THE CIRCULATION:
A. BOTH ARTERIES AND VEINS
HAVE THREE LAYERS OF TISSUE:
ENDOTHELIUM, SMOOTH MUSCLE AND
AREOLAR TISSUE
B. ARTERIES CONDUCT BLOOD AWAY FROM
THE HEART. THEY HAVE ELASTIC AND
MUSCULAR WALLS.

26. Endothelium
Smooth
muscle
Connective
tissue
Capillary
100 µm
Basement
membrane
Valve
Artery
Arteriole
Venule
Vein

27. C. ARTERIES ARE TESTED WHEN TESTING BLOOD PRESSURE. NORMAL SYSTOLIC
PRESSURE IS 120 MM HG AND NORMAL
DIASTOLIC IS 80 M HG. MEASURED WITH A
SPHYGMOMANOMETER 
Blood pressure
reading: 120/70
Pressure
in cuff
above 120
Pressure
in cuff
below 120
Pressure
in cuff
below 70
Rubber cuff
inflated
with air
120
120 70
Sounds
audible in
stethoscope
Sounds
stop
Artery
Artery
closed

28. D. ARTERIES BRANCH INTO ARTERIOLES.
THEIR WIDTH IS MANAGED BY HORMONES
& NERVES.
E. CAPILLARIES – THE MOST NARROW
BLOOD VESSELS - THESE ARE DIFFUSION
ZONES FOR EXCHANGES BETWEEN THE
BLOOD AND THE INTERSTITIAL FLUID.

29. -ERYTHROCYTES TRAVEL SINGLE-FILE
THROUGH CAPILLARIES.
F. CAPILLARIES MERGE INTO VENULES AND
THEN VEINS.
G. VEINS HAVE VALVES TO PREVENT
BACKFLOW.

30. CONTRACTING SKELETAL MUSCLES
SQUEEZE THE VEINS. THIS SQUEEZING HELPS
THE BLOOD TO MOVE UPWARDS AGAINST
GRAVITY.

31. H. BLOOD PRESSURE IS MONITORED BY
THE MEDULLA OBLONGATA. IF BLOOD
PRESSURE INCREASES, THE ARTERIOLES
RELAX = VASODIALATION. IF BLOOD
PRESSURE DECREASES, THEN VASOCON-
STRICTION OCCURS.

32. -Blood pressure is also affected by hormones
such as aldosterone.
-Blood pressure is greatly influenced by
the sympathetic nervous system – activated
in flight or fight situations. Conversely, the
parasympathetic nervous system tends
to decrease blood pressure.

34. I. BLOOD CLOTTING-
SPASMS OF SMOOTH MUSCLE STOPS
BLOOD FLOW TEMPORARILY.
2. PLATELETS STIMULATED BY
THROMBIN CLUMP TO MAKE A PLUG.
3. A FIBRIN MESH FORMS WITH THE
PLATELETS. THE BLOOD COAGULATES
TO MAKE A CLOT.

35. A BLOOD CLOT

36. TYPE A HAS A MARKERS, TYPE B HAS B MARKERS, AB HAS BOTH A AND B
J. BLOOD TYPES
TYPE A HAS A MARKERS, TYPE B HAS
B MARKERS, AB HAS BOTH A AND B
MARKERS AND O HAS NO MARKERS.
2. TYPE O IS THE UNIVERSAL DONOR AND
AB IS THE UNIVERSAL RECEIVER.
Blood Type A B AB O
Antigens A B A and B None
Antibodies in Plasma Anti-B Anti-A None Both Anti-A and Anti-B

37. 3. RH IS ANOTHER MARKER ON THE
BLOOD CELLS. RH+ MEANS YOU HAVE THE
MARKER AND RH- MEANS YOU DO NOT.