1. Cardiovascular system
overview
Presented 2011 / 2012 by: Dr Magdi El Sersi
Assistant Prof of Medical Physiology
Basic Medical Sciences Department
Ext. 7243
E mail:
melsersi@sharjah.ac.ae

2. •Feel free to make notes, but don’t
try and copy everything I show and
say – you won’t have time. I would
rather prefer that you just listen.
•If you have a question please catch
my attention – I am more than happy Profile
to stop; or you can pass by my office
at M27-Room 123. Silent
•The recommended course
textbooks cover my lectures well.
•If you need a copy of this
presentation, then you can get it
from the blackboard.

4. MAIN FUNCTIONS OF THE
CIRCULATORY SYSTEM
• Transport and distribute essential substances
to the tissues.
• Remove metabolic byproducts.
• Adjustment of oxygen and nutrient supply
in different physiologic states.
• Regulation of body temperature.

5. The system has two major
divisions:
v A pulmonary circuit :
which carried blood to the
lungs for gas exchange and
returns it to the heart.
v A systemic circuit :
which supplies blood to
every organ of the body.

6. The right
side of the
heart serves
the The left side
pulmonary serves the
circuit systemic
circuit.

7. The heart is enclosed in a
double-walled sac called the
pericardium.
The outer wall,
called the parietal
pericardium
(pericardial sac).
has a tough, superficial fibrous layer of dense
irregular connective tissue and a deep, thin
serous layer.
The serous layer turns inward at the base of the
heart and forms the visceral pericardium (epicardium)
covering the heart surface .

8. The pericardium
The pericardial sac is anchored by ligaments to the
diaphragm below and the sternum anterior to it.
Between the parietal and visceral membranes
is a space called the pericardial cavity . It
contains 5 to 30 mL of pericardial fluid.

9. The pericardial fluid Pathophysiology : Pericardial
lubricates the membranes disease manifest itself by the
and allows the heart to accumulation of fluid in the
beat almost without pericardial space (pericardial
friction. effusion) and /or inflammation
of the pericardium (pericarditis).
The pericardial cavity can fill with up to
2 litters of serous fluid
(hydropericardium ) or blood
(hemopericardium) that prevent
normal diastolic filling and thereby
reduces cardiac output.

10. COLLECTING
PUMP TUBULES
THE MAIN CIRCUIT
DISTRIBUTING THIN
TUBULES VESSELS

11. There are 3 primary blood vessel
types:
1. Arteries : which carry blood
away from the heart.
2. Veins : which carry blood
towards the heart.
3. Capillaries : tiny blood
vessels that function in the
exchange of gases, nutrients,
and wastes between the blood
and the interstitial fluid.

12. The walls of both arteries and veins have 3
layers that surround the lumen:
1. Tunica externa
Outermost layer. Made primarily of loose
connective tissue. Anchors the blood
vessel to the surrounding tissue.
2. Tunica Media
Consists primarily of smooth muscle and
is responsible for vasoconstriction and
vasodilatation. Usually the thickest layer
in arteries.
3. Tunica Interna (Endothelium) Acts as a
selectively permeable barrier to blood
solutes.
Secretes vasoconstrictors and
vasodilators.
Provides a smooth surface that repels
blood cells and platelets.

13. They are constructed to withstand
surges of blood pressure associated with
ventricular systole.
•They're more muscular than veins and appear
relatively round in tissue sections.
• They retain their round shape even when empty.
There are 3 basic categories of arteries

14. Conducting (or Elastic) Arteries
Distributing (or Muscular) Arteries
Arterioles

15. 1. Conducting (or Elastic) Arteries
The largest
Examples include the aorta, pulmonary arteries,
and the common carotid arteries.

16. Their tunica media contains a
great deal of elastic tissue.
The elastic tissue allows for
expansion during ventricular
systole and recoil during
ventricular diastole.
This helps create continuous
flow from a discontinuous
pump.

17. Conducting arteries expand during ventricular systole to
receive blood, and recoil during diastole:
*Their expansion takes some of the pressure off the blood so that
smaller arteries downstream are subjected to less systolic stress .
•* Their recoil between heart beats prevents t he blood
pressure from dropping too low while the heart is relaxing
and refilling.
Lessen the fluctuations in blood pressure

18. 2. Distributing (or Muscular) Arteries
 Smaller branches ,distribute blood to individual organs.
They have 25-40 layers of smooth muscle cells
constituting about three quarters of the wall thickness.
Examples include the brachial, femoral, and splenic arteries

19. 3. Arterioles
•Smallest of the three.
• They are heavily innervated .
• The primary points at which the body controls the
relative amounts of blood directed to specific organs.

20. Linking the arterioles
to the capillaries are
short vessels known
as metarterioles.
Part of their wall surrounded
by smooth muscle
These muscle cells form precapillary sphincters which
encircle the entrance to a capillary bed.

21. These sphincters regulate how much blood will flow
through particular capillary beds.

22. Arterial sense organs:
Certain major arteries above
the heart have sensory
structures in their walls that
monitor blood pressure and
chemistry.
They transmit information to
the brain stem that is used to
regulate the heart beat,
vasomotion and respiration.

23. The sensory receptors are of three kinds
1. Carotid sinuses. These are
baroreceptors (pressure sensors) that
respond to changes in blood pressure.
* Thin tunica media
* An abundance of glossopharyngeal
nerve fibers in the tunica externa.
A rise in blood pressure stretches the
thin media and stimulates the nerve
fibers which transmits signals to the
The carotid sinuses vasomotor and cardiac centers of the
are located in the brainstem, which responds by lowering
wall of the internal the heart rate and dilating the blood
carotid artery vessels, thereby lowering the blood
pressure.

24. 2. Carotid bodies: located near the
branch of the common carotid
arteries.
They are chemoreceptors
that monitor changes in
blood composition.
They primarily transmit
signals to the brainstem
respiratory centers, which
adjust breathing to stabilize
the blood pH and its CO2 and
O2 levels

25. 3. Aortic bodies: These are one
to three chemoreceptors
located in the aortic
arch
They are structurally similar to
the carotid bodies and have
the same function.

26. Capillaries
There are approximately 1 billion of them in the human body.
Capillaries are organized into groups of 10-100 in capillary beds
There are 3 separate types of capillaries:
1. Continuous Capillaries
2. Fenestrated Capillaries
3. Sinusoidal Capillaries

27. 1. Continuous Capillaries Most common.
Abundant in skin and muscle.
Endothelial cells are joined by tight junctions.
but contain intercellular clefts through which small molecules
(e.g., glucose, but not albumin) can pass.
Cerebral capillaries lack these clefts and have far more
numerous tight junctions forming the blood brain barrier which
helps protect the delicate brain tissue from blood-borne toxins
and pathogens.

28. Some continues capillaries
exhibit cells called pericytes
that lie external to the
endothelium
Pericytes are contractile,
have elongated tendrils that
wrap around the capillary
It thought that they contract and regulate blood flow
through the capillaries.
They also can differentiate into endothelial and smooth
muscle cells and thus contribute to vessel growth and
repair.

29. 2. Fenestrated capillaries
These pores allow for
the rapid passage of
molecules, even
proteins , through the
capillary wall.
Found in sites of active
Similar to absorption (small intestine),
continuous secretion (endocrine
capillaries but organs) and capillary
some of the filtration (kidneys).
endothelial cells
has filtration pores
fenestrations.

30. 3. Sinusoidal Capillaries
Highly modified, extremely
leaky, fenestrated capillaries
Contain irregularly shaped lumen and large intercellular clefts
Found in sites where large stuff needs to
exit/enter the bloodstream.
Such sites include bone marrow (for
passage of nascent blood cells), lymphoid
organs (for easy entry/exit by WBCs) and
the liver (for large plasma proteins, e.g.,
albumin).

31. In the liver and the spleen , the
endothelium is intimately
associated with macrophages.
In these locations the sinusoids
are twisty and tortuous,
conformed to the shape of the
surrounding tissue. . The
twistiness makes blood flow
extra slowly which gives time
for splenic and hepatic
macrophages to monitor and
assess its contents.

32. Just by looking at this image, can you identify the
different capillary types?

33. Veins
The capacitance vessels of the cardiovascular system
because :
They are relatively thin-walled and flaccid.
Expand easily to accommodate an
increased volume of blood.
At rest, about 54% of
the blood is found in
the systemic veins as
compared with only
11% in the systemic
arteries

34. Being distant from the ventricles of the heart,
they are subjected to relatively low blood
pressure.
In large arteries, blood pressure averages 90 to
100 mm Hg (millimeters of mercury) and
surges to 120 mm Hg during systole, whereas
in veins it averages about 10 mm Hg.
Considering the relatively low pressure in
the veins.
how blood is forced through them to get back to the
heart????

35. It's a combination of 3 separate things:
1.Skeletal Muscle Pump .
2. Respiratory Pump .
3. Venous Valves

36. It's a combination of 3 separate
things:
1.Skeletal Muscle Pump .
2. Respiratory Pump .
3. Venous Valves
1. Skeletal Muscle
Pump :- the
contraction/relaxation
cycles of skeletal
muscles squeeze the
veins forcing the
contained blood
towards the heart.

37. 2. Respiratory Pump : as we inhale,
our thoracic cavity expands while
our abdominal cavity compresses.
pressure within veins of the
thoracic cavity drops.
Meanwhile, pressure in the
abdominal veins increases.
This combination results in
increased blood flow towards that
heart.

38. 3. Venous Valves: - one-way
valves (similar to the
semilunars of the heart) made
of flaps of endothelium are
found in medium veins
(mostly in the legs and the
arms) where they help prevent
backflow.

39. Pathophysiology: varicose
veins:
In people who stand for long
periods, blood tends to pool in the
lower limbs and stretch the veins.
This is especially true of superficial
veins, which are not surrounded by
supportive tissue.
Stretching pulls the cusps of the
venous valves farther apart until the
valves become incompetent to
prevent the backflow of blood

40. As the veins become further
distended, their walls grow
weak and they develop into
varicose veins with irregular
dilations and twisted pathways.