2. Overview of Cadiovascular System
• It is the transport system of the body.
• Components:
– heart
– Arteries
– Veins
– capillaries
3. Heart
• Simply , the heart is a transport-system
pump.
• Located in the mediastinum.
• The base is superior and the apex inferior
• Well protected
4.
5. Coverings
• Enclosed by a double-walled sac called the
pericardium
• Superficial part is the fibrous pericardium
(dense connective tissue)
• Deep part is the serous pericardium
– Connected to the fibrous pericardium is the
parietal layer
– The visceral layer forms the external surface of
the heart itself
– Between is the pericardial cavity filled with serous
fluid
6. Heart wall layers
• Epicardium is the visceral layer of the serous pericardium
• Myocardium is the thick muscle layer
• Endocardium is the inside of the heart (squamous epithelium and
areolar tissue)
7. Chambers & external anatomy
• Superior are the two atria (sing. atrium)
• Inferior are the two ventricles
• Atrioventricular sulcus inbetween the atria
and ventricles.
• Interventricular sulcus in between the
ventricles.
8.
9.
10. Atria
• Receiving chambers of blood.
• Auricles are small protruding appendages
• Separated by the inter-atrial septum
• Posterior wall is smooth
• (Right) inter-atrial septum houses the fossa
ovalis
• Right atrium receives blood from the inferior
and superior vena cava
• Left atrium receives blood from the four
pulmonary veins( two right and two left).
11.
12. Ventricles
• Pumping chambers of blood.
• Left ventricle empties into the aorta.
• Right ventricle empties into pulmonary
trunk which leads to pulmonary arteries.
• Compare thickness of ventricles to atria
and right to left ventricle
13.
14.
15. Heart valves
• Atrio-ventricular (AV) valves separate
atria/ventricles
• Right valve is the tricuspid, left is the mitral
(bicuspid)
• Collagen cords called chordae tendineae
attach cusps to papillary muscles.
• Ventricles separated from major vessels
by aortic & pulmonary semilunar valves.
16.
17.
18.
19. Blood flow
Venacava
Right atrium
Tricuspid Valve
Right
Ventricle
Pulmonary
Valve
Pulmonary
Trunk/
Arteries
Lungs
Pulmonary
veins
Left atrium
Mitral
Valve
Left
Ventricle
Aortic
Valve
Ascending Aorta
21. The blood vessels
• The cardiovascular system has three
types of blood vessels:
– Arteries (and arterioles) – carry blood away
from the heart
– Capillaries – where nutrient and gas
exchange occur
– Veins (and venules) – carry blood toward the
heart.
23. The Arteries
• Arteries and arterioles take blood away from the heart.
• They are thick walled than veins
• The lumen is smaller than the accompanying veins.
• They have no valves.
• An artery is accompnied by vein(s) and nerve(s). They
are together called neurovascular bundle.
• Types:
• The large arteries: elastic in nature. Example aorta and its main
branches , pulmonary arteries.
• Medium and small arteries of muscular type: temporal, occipital, radial,
popliteal etc
• Smallest arteries of muscular type (arterioles) : Arterioles can constrict
or dilate, changing blood pressure.
24. The arteries: microscopic structure
– All arteries are made up of
three coats:
• Tunica intima: the inner
coat ,formed by a layer of
flat endothelial cells
supported by
subendothelial areolar
tissue and internal elastic
lamina.
• Tunica media: middle
coat, thickest layer and
made up of circular muscle
and elastic tissue.
Externally it has external
elastic lamina.
• Tunica adventitia: thin but
strongest of all coats,
made up of both elastic
and collagen tissue
25. The arteries: blood supply and nerve
supply
• Blood supply:
– The larger arteries of more than 1 mm are supplied with blood
vessels.
– The nutrient vessels are called vasa vasorum, supply tunica
adventitia and outer part of tunica media.
– The rest, i.e., intima and inner part of media is nourished directly
by diffusion from the luminal blood.
• Nerve supply:
– The nerve are called nervi vascularis. They are mostly non-
myelinated sympathetic fibres and vasoconstrictor in nature.
– Few fibres are myelinated and they are sensory to the outer and
inner coats of arteries.
– Vasodilation innervation is restricted to: skeletal muscle vessels:
cholinergic sympathetic nerves, exocrine gland vessels etc
26. Veins
• They are thin walled than arteries.
• Lumen is larger than that of accompanying arteries.
• Veins have valves which maintain the unidirectional flow
of blood, even against the gravity. However, the valves
are absent:
– In the veins less than 2mm
– Venacava
– Hepatic, renal, cerebral, pulmonary, umbilical veins
• The muscular and elastic tissue content of the venous
wall is much less than arteries.
• They act as a reservoir of blood.
27. Vein: microscopy
• The same three coats as arteries, but the coats are ill-
defined, and the muscle and elastic tissue contents is
poor.
• Internal elastic lamina in the intima is absent.
• In tunica media, the amount of collagen fibres is more
than elastic and muscle fibres.
• The adventitia is thickest and best developed and
contains collagen, elastic as well as muscle fibres.
• Blood and nerve supply:
– Vasa vasorum, may penetrate upto the intima
– Nerve supply same like arteries but fewer in number.
28. Factors helping in venous return
• Overflow from capillaries, pushed from behind by the
arteries
• Negative intrathoracic pressure sucks the blood into the
heart from all over the body
• Gravity helps venous return in the upper part of the body
• Arterial pulsations press on the veins intermittently and
drive the blood towards the heart
• Venous valves prevent any back flow of the blood
• Muscular contractions press on the veins and cause
venous return. The calf muscles (soleus) is also known
as the peripheral heart for this reason.
29.
30. The Capillaries
• Capillaries: have single layer of endothelial cells with a basal lamina
and a pericapillary layer of connective tissue cells and fibres.
• They allow exchange of gases and nutrients with tissue fluid.
• Types:
– Continuous capillaries: found in the skin, connective tissue,
skeletal, smooth muscles, lung and brain. Small molecules upto
10 mm size can be passed across their walls.
– Fenestrated capillaries: in renal glomeruli, intestinal mucosa,
endocrine glands and pancreas. Larger molecules upto 20-100
mm size can be passed across their walls.
• Capillary beds are present in all regions of the body but not all
capillary beds are open at the same time.
• Contraction of a sphincter muscle closes off a bed and blood can
flow through an arteriovenous shunt that bypasses the capillary bed.
31. Sinusoids
• Sinusoids replace capillaries in certain organs, like liver,
spleen, bone marrow, suprarenal glands, parathyroid
glands etc.
• They are large, irregular, vascular spaces which are
closely surrounded by the parenchyma of the organ.
• The lumen is wider than capillaries (upto 30 microns)
and irregular(capillaries about 6-8 microns)
• Walls are thinner and may be incomplete. Lined by
endothelium in which macrophages are often present.
• Basal lamina is replaced by a thin layer of reticular
fibres.
• They may connect arteriole with venule (spleen, bone
marrow) or venule with venule (liver).
33. Anastomosis and end arteries
• Precapillary or postcapillary communication between the
neighbouring vessels
• Circulation through the anastomosis is called collateral circulation.
• Types:
– Arterial: palmar arch, plantar arch, circle of Willis etc
– Venous: dorsal venous arch of hands and foot
– Arteriovenous anastomosis(shunt): when the organ is active
these shunts are closed and blood circulates through the
capillaries, however when the organ is at rest, the blood
bypasses the capillary bed and is shunted back through the
anastomosis.
– Examples: mucous membrane of nose, erectile tissue of sexual
organ, the tongue etc
• End arteries: arteries which do not anastomose with their
neighbours eg: central artery of retina, splenic artey, renal artery etc
– Importance: if occlusion occurs, death of the tissue results.
34. Types of circulation
• Systemic circulation
• Pulmonary circulation
• Portal circulation: it is a part of systemic circulation in
which:
– The blood passes through two sets of capillaries
before draining into a systemic vein
– The vein draining first capillary network is known as
portal vein which branches like an artery to form the
second set of capillaries or sinusoids.
– Examples: hepatic and hypophyseal portal
circulations.
35. Systemic and pulmonary circulation
• Right side of heart
contributes to
pulmonary circuit
• Left side contributes
to systemic circuit
38. Applied anatomy
• Blood pressure: systolic and diastolic, pulse
pressure
• Hemorrhage: result of rupture of blood vessels.
Venous bleeding causes oozing of blood and
arterial bleeding causes spurting of blood.
• Thrombosis and embolism
• Arteriosclerosis: arteries become stiff in old
ages.
• Arteritis and phlebitis
