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1. Vascular System
Dr. Sandeep kumar Sharma
PhD medical anatomy
ASMC firozabad uttarpradesh

2. introduction
 Vascular system is a transport system of the body
 Which conveyed to places where they are utilized
and the metabolites are conveyed to appropiate
places from where they are excreted.
 The conveying medium is a liquid tissue ,the
blood which flows in tubular channels called
blood vessels.
 The circulation is maintained by the central
pumping organ called the heart.
 About 5 litres blood is containing in the vascular
system.

3. Component of the vascular system
It is a closed system of tubes made up of the
following parts
Heart
Arteries
Veins
Capillaries
Heart :
• it is a four chambered muscular organ which pumps
blood to various parts of the body
• Each half of the heart has a receiving chamber
called atrium and a pumping chamber called
ventricles.

4. Arteries
• These are distributing channels which carry blood
away from the heart.
• They branch like trees on their way different parts
of the body.
• The large arteries are rich in elastic tissue ,but as
branching progresses there is smooth muscles in
their wall.
• The minute branches which are just visible to the
naked eye are called arterioles.

5. Veins
• These are draining channels which carry blood from
different parts of the body to the heart
• Like rivers ,the veins are formed by tributaries.
• The small veins (venules) join together to form
larger veins which in turn unite to form great vein
called venae cavae.

7. Capillaries
• These are networks of microscopic vessels which
connect arteriols with the venules
• They come in intimate contact with the tissues for a
free exchang of nutrients and metabolites across their
wall between the blood and the tissue fluid.
• Capillaries are replaced by sinusoids in certain organs
like liver and spleen.
• Functionally blood vessels including arteries
A. Distributing vessels including arteries
B. Resistance vessels including arteriols and precapillary
sphincters
C. Exchang vessels including cap., sinusoids, postcapillary
venules.
D. Reservoir vessels including large venules and vein
E. Shunts including various types of anatomosis.

9. Types of circulation of blood
1. Systemic circulation
2. Pulmonary circulation
3. Portal circulation
Systemic circulation:
 From the left atrium the oxygenated blood reaches
the left ventricle which pumps the blood to the
remotest capillaries through the aorta and its
branches.
 At the capillaries nutritive materials and oxygen pass
from the blood to the tissues
 Through them waste products and carbon dioxide
return from the tissues to the blood
 Finally blood is returned to the heart through the
venules ,veins, superior vena cava and inferior vena
cava.

10. Pulmonary circulation
• The right atrium receives the venous blood from
superior vena cava, inferior vena cava and from
coronary sinus and convey it to the right ventricle.
• In turn ,the right ventricle pumps the blood to the
capillary plexus of the lungs via the pulmonary
trunk.
• Here in the carbon dioxide is exchanged for oxygen
• The oxygenated blood reaches the left atrium via
the pulmonary veins.

11. Portal vein (portal circulation)
It is part of systemic circulation which has the
following characteristics
• Blood passes through two sets of capillaries before
draining into a systemic vein
• Vein draining the first capillary network is known as
portal vein which branches like an artery to form a
second set of capillaries of sinusoids e.g hepatic
portal circulation , hypophyseal portal circulation
and renal portal circulation.

14. Classification of blood vessels
Blood vessels are classified as under
• Arteries
• arterioles
• capillaries
• Sinusoid and cavernous tissues
• Venules and veins
Arteries
Characteristic features of arteries
• Arteries are thick walled being uniformly thicker than
accompanying vein except for the arteries within the cranium and
vertebral canal where they are thin.
• Their lumen is thinner than accompanying veins.
• Aretries have no valves.
• An artery is usually accompanied by vein and nerve and three
together form the neurovascular bundle which is surrounded and
supported by a fibroareolar sheath.

17. •
Types of arteries and structure
• Large arteries of elastic type (aorta and pulmonary artery)
• Medium and small arteries of muscular type e.g temporal,
occipital ,radial ,popliteal artery.
• Smallest arteries of muscular type (arterioles)
• The arteries measure between 50-100 micron. They divide
into terminal arterioles with 15-20 microns diameter which
have one or two layers of smooth muscle in their walls.
• Side branches from terminal arterioles are called as met
arterioles which measure about 15-20 microns at their origin
and 5 microns at their termination.
• The terminal narrow end is surrounded by a precapillary
sphincter which regulates the blood flow into the capillary
bed.
• The muscular arterioles are responsible for generating
peripheral resistance and thereby for regulating the diastolic
blood pressure.

18. Microscopically
• All arteries are made up of three coates.
 Inner coat : tunica intima
• It is formed by a layer of flattend endothelial cells which are
supported by subendothelial areolar and fenestrated
internal elastic lamina.
 Middle coat: tunica media
• It is thickest of ll coats and
• Made up of smooth muscle and elastic tissue arranged
circularly
• It is limited externaly by a fenestrated external elastic lamina
 Outer coat: tunica adventitia
• It is thin but strongest of all coats
• It is made up of longitudinally arranged fibres of both
collagen and elastic tissue making it fibroelastic.

20. Large artery /elastic artery
key – TM Tunica media
TA Tunica adventitia
A Elastic fibre

21. Medium size artery/muscular artery
key: TM Tunica media,TA Tunica adventitia,A Internal elastic lamina,
B Smooth muscles fibre,C Few elastic fibre

23. Blood supply of arteries :
• Large arteries (of more than 1 mm in diameter ) are
supplied with blood vessels .
• These nutrient vessels are called vasa-vasorum
which form a dense capillary network in the tunica
adventitia.
• They supply adventitia and outer part of tunica
media.
• The rest of vessel wall (intima + inner part of tunica
media) is nourished directly by diffusion from the
luminal blood.
• Fenestrations in the elastic laminae facilitate the
diffusion.

25. Nerve supply of artery:
• The nerves supplying an artery are called nervi
vascularis
• These nerves are mostly non myelinated
sympathetic fibers which are vasoconstrictor in
function
• A few fibers are myelinated, and are believed to be
sensory to the outer and Inner coats of the arteries.

27. Capillaries :
• Capillaries (capillus=Hair) are network of microscopic
endothelial tubes interposed between metarteriol and
venules.
• The true capillaries (without any smooth muscles cell)
begin after a transition zone of 50-100 microns beyond
the precapillary sphincters.
• The capillaries are replaced by cavernous (dilated )
space in the sex organs, splenic pulp and placenta.
Size:
• The average diameter of a capillary is 6-8 microns, just
sufficient to permit the red blood cells to pass through
in “single file”.
• But the size varies from organ to organ.
• It is smallest in the brain and intestine , and is largest
(20 microns) in the skin and bone marrow.

28. Types of capillaries and structure:
• The capillaries are classified as continuous and
fenestrated according to the type of junctions
between the endothelial cells.
Continuous capillaries are found in the skin
,connective tissue skeletal and smooth muscles
,lung and brain. They allow passage of small
molecules across their walls (up to 10 micrometer
size).
Fenestrated capillaries are found in the renal
glomeruli,intestinal mucosa,endocrine glands and
pancreas. They allow passage across their walls of
larger molecules (up to 20 -100 mm size).

29. The capillary wall is composed of:
 A single layer of endothelial cells.
 A basal lamina of glycoprotein which surrounds the
endothelial cells and splits at places to enclose
pericapillary cells called pericytes, and
 A pericapillary layer of connective tissue cells and
fibers.
 The capillary bed and post capillary venules form an
enormous area for the exchange of nutrients ,gases,
metabolites and water, between the blood and
interstitial fluid.
 Capillaries also allow migration of leukocytes out of
the vessels.
Sinusoids replace cpillaries in certain organs ,like liver ,
spleen, bone marrow , suprarenal glands, parathyroid
glands,carotid body, etc.

31. Characteristics: (sinosoids)
• Sinusoids are large irregular vascular spaces which
are closely surrounded by the parenchyma of the
organ.
• They differ from capillaries in the following
respects:
• Their lumen is wider (upto 30 microns) and irregular
• Their walls are thinner and may be incomplete. they
are lined by endothelium in which the phagocytic
cells(macrophages) are often distributed. the
advential support is absent, and basal lamina
replaced by a thin layer of reticular fibers.
• They may connect arteriols with venule
(spleen,bone marrow) or venule with venule(liver).

32. Cavernous tissues :
• These are blood filled spaces lined by endothelium
and surrounded by trabeculae. The latter contain
smooth muscles fibers. The arterioles and venules
directly open into these spaces.
• The cavernous tissues are present in the erectile
tissues of the penis or clitoris and in the nasal
mucous membrane.

33. Veins :
Characteristic features :
 Veins are thin walled ,being thinner than the arteries.
 Their lumen is larger than that of the accompanying arteries.
 Veins have valves which maintain the unidirectional flow of blood,
even against Gravity. Since the venous pressure is low (7 mm Hg)
the valves are of utmost value in the venous return . However the
valves are absent (a) in vein of less than 2mm diameter (b) in
venae cavae (c) in the hepatic ,renal uterine ovarian (not
testicular) cerebral , spinal, pulmonary and umbilical veins.
 The muscular and elastic tissue content of the venous wall is much
less than that of arteries.
 Large vein have dead space around them for their dilatation during
increased venous return. The dead space commonly contains the
regional lymph nodes.

35. Structure of veins:
 Veins are made up of usual three coats which are found in the
arteries. But the coats are ill defined, and the muscle and
elastic tissue contents is poor.
 A proper internal elastic lamina in the intima is absent.
 In the weak and poorly developed tunica media ,amount of
collagen fibers is more than the elastic and muscles fibers.
 The adventetia is thickest and best developed it contain the
collagen elastic as well as muscles fibers.
 The smooth muscles altogether absent in the:
Vein of maternal part of placenta
cranial venous sinuses and pial vein
Retinal vein
Vein of cancellous bone
Venous spaces of the corpora cavernosa and corpus
spongiosum

37. Large vein
key : TI Tunica intima, TM Tunica media TA Tunica adventitia A endothelium B
Smooth muscle fibers C Longitudinally arranged smooth muscles fibre

38. Blood and nerve supply of vein:
• The larger vein like the arteries are supplied with
nutrient vessels called vasa vasorum. But in the
veins, the vessels may penetrate up to the intima
,probably because of the low venous pressure and
low oxygen tension.
• Nerves are also distributed to the vein in the same
manner as to the artery but in fewer in the number.

40. Factors Helping in Venous Return
• Overflow from the capillaries , pushed from behind from the
arteries.
• Negative intra thoracic 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 venae comitantes
intermittently and drive the venous blood towards the heart.
• Venous valves prevent any regurgitation (backflow)
of the luminal blood.
• Muscular contractions press on the veins and form a very
effective mechanism of venous return. the calf muscles
(soleus) for this reason are known as the peripheral heart.
Thus ,the muscle pumps are important factors in the venous
return.

41. Anastomosis of blood vessels
Definition
 A precapillary or post capillary communication between the neighboring
vessels is called anastomosis.
 Circulation through the anastomosis is called collateral circulation.
TYPES
 Arterial anastomosis is the communication between the arteries or
branches of arteries.
 It may be actual or potential
• in actual arterial anastomosis the arteries meet end to end . For example
,palmar arches ,plantar arch ,circle of willis ,intestinal arcades around the
stomach ,labial branches of facial arteries ,and the uterine and ovarian
arteries.
• In potential arterial anastomosis the communication takes place between
the terminal arterioles.
-Such communications can dilate only gradualy for collateral circulation
-There fore on sudden occlusion of main artery ,the anastomosis may fail to
compensate the loss.
-The example are seen in the coronary arteries ,around the limb joints ,the
cortical branches of cerebral arteries, etc.

43. • Venous anastomosis is the communication between the veins or
tributaries of veins.For example dorsal venous arches of the hand
and foot.
• Arteriovenous anastomosis(shunt) is communiction between
artery and a vein. It serves the function of phasic activity of the
oragan.when the oragan is active these shunts are closed and the
blood circulates through the capillaries.
However ,when the organ is at rest the blood bypasses the
capillary bed and is shunted back through the arterivenous
anastomosis.
The shunt vessels may bestraight or coiled possesses the thick
muscular coat ,and is under the influence of sympathetic system.
Shunts of simple structure are found in the skin of nose
,lips,external ear, mucous membrane of nose and alimentry canal.
Specialized arteriovenous anastomosis are found in the skin of
digital pads and nail beds.
They form a number of small units called glomera.
Anatomosis contd…

47. End-arteries
Definition :
Arteries which do not anastomose with their neighbours
arteries are called end artries for example,
• Central artery of retina is the best example of an
absolute end artery.
• Central branch of cerebral arteries and vasa recta of
mesentric arteries,arteries of spleen ,kidney,lungs and
metaphyses of long bones.
Importance
Occlusion of an end-artery causes serious nutritional
disturbences resulting in death of the tissue supplied by
it. For example ,occlusion of central artery of retina
results in permanent blindness.

49. Applied anatomy of cardiovascular system
• The blood pressure is the arterial pressure exerted by
the blood on the arterial wall.
• The maximum pressure during ventricular systole is
called systolic pressure;the minimum pressure during
ventricular diastole is called diastolic pressure.
• The systolic prssure is generated by the force of
contraction of the heart.
• The diastolic pressure chiefly due to arteriolar
tone(peripheral resistance)
• The heart has pump the blood against the diastolic
pressure which is a direct load on the heart.
• The difference between systolicand diastolic pressure
is called puls pressure

50. Applied anatomy of cardiovascular system
• Hemorrhage (bleeding) is the obvious result of rupture of the blood vessels
 Venous hemorrhage causes oozing of blood ; arterial hemorrhage causes
spurting of blood
• Vascular catatrophies are of three type;
 Thrombosis
 Embolism
 Hemorrhage
 All of them result in a loss of blood supply to the area of distribution of the
vessel involved , unless it is compensated by collateral circulation.
 Arteriosclerosis occurs in old age due to which arteries become stiff.
• Thid causes a variable reduction in the blood supply to the tissues and a rise
in systolic pressure.
• Arteritis and phlebitis inflammation of an artery is known as arteritis , and
inflammation of avein as phlebitis.
 Angeion is a greek work meaning a vessel (blood vessel or lumph vessel).
 Its word derivatives are angiology, angiography, hemangioma, and
thromboangitis obliterance.