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Monday, 6 November 2017

Introduction to the Cardiovascular System
Learning Objectives
• Classify the different types of blood vessel
• Trace the flow of blood through the heart
• Classify and briefly describe the different circulatory circuits: systemic,
pulmonary and hepatic portal
• Locate the great vessels
• Briefly explain the lymphatic circulation

Structure of blood vessels

Inner: Tunica Intima


Basement membrane


Endothelium - simple squamous


Endothelial function - vasoactive/minimises friction






Tunica Media

Circular smooth muscle

Collagen & elastic fibres

Vaso-constriction/dilation


Outer: Tunica Adventitia


CT elastin and collagen


Protects, strengthens, anchors


Vasa vasorum (blood vessels of the blood vessels, vessels take blood from
lumen to the wall)


Elastic/conducting artery

These arteries have the main function to take blood away from the heart, so they
have a large tunica media and a large amount of elastin they have their own blood
supply (vasa vasorum)

e
...
aorta


Muscular/distributing artery

These arteries take blood to the specific areas of the body, and have a large tunica
media with internal elastic lamina and external elastic lamina
...


e
...
renal artery


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Monday, 6 November 2017

Arterioles

They have a narrow lumen and a large amount of smooth muscle


Capillaries

These are simple endothelial tubes that are specialised for exchange of nutrients
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Veins

Venues and veins have a larger lumen and thinner walls than corresponding arteries
...



Musculovenous pump

Veins in the lower limb are often positioned in between muscles
...



Blood flow through heart

Deoxygenated blood enters heart in right atrium through superior and inferior vena
cava
...
Leaves heart via pulmonary trunk and pulmonary
arteries
...
Blood goes into left ventricle
...



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Monday, 6 November 2017

Great vessels

At the arch of the aorta there are 3 arteries which aim upwards to provide blood to
the structures above the heart
...

Left common carotid artery

Supplies blood to head and neck on left side
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Veins are more symmetrical and they join at the superior vena cava to return blood
to the heart
...
In the arm, it becomes the brachial artery
...
In the hand, they split into 2 palmar arches and digital branches
...

Veins however have 2 networks (deep and superficial)
...
The basilic (medial) and cephalic (lateral) veins are
superficial
...
In the thorax the thoracic aorta
branches off to give many intercostal arteries
...


The abdominal aorta mainly supplies the gut, and there are 3 unpaired arteries that
come off the anterior aspect of the aorta
...


The 3 unpaired arteries to the gut are the coeliac trunk (blood to foregut: pancreas,
spleen, liver, stomach), the superior mesenteric artery (midgut: duodenum to
transverse colon) and the inferior mesenteric artery (hindgut: descending colon,
sigmoid colon, rectum)
...
This second split occurs around L4/L5
...
The external arteries are further away and supply blood to the lower limb
...
Below the knee it
forms the anterior and posterior tibial arteries
...
Like the
upper limb, there are the veins alongside with the same
name, and it also has superficial and deep veins too
...

There is a tendency for the great saphenous vein to
become varicose, created by gravity causing blood to
pool and go against valve action in the leg
...


Oxygenated blood goes from the aorta to the coeliac trunk to the stomach
...
The liver stores and releases glucose as needed, and it also clear the blood of
drugs and other harmful substances
...


The splenic vein, superior mesenteric vein (midgut) and the inferior mesenteric vein
(hindgut) make up the hepatic portal vein
...
Therefore fluid is forced out
...
However more
fluid leaves the arteriole end than returns in the venous end, so there is a net loss of
fluid from capillaries and a net increase in fluid surrounding the capillary bed
...
Around
capillaries there are lymphatic vessels that drain this excess fluid
...
They are one way endothelial tubes from
the capillaries to the veins of the body
...
Lymphatic capillaries
drain to lymphatic vessels which drain to lymph nodes
...
This
system of drain is leading up to the drainage of the entire trunk in the body
...
The right lymphatic trunk is the
upper right quarter of the body and the thoracic duct drains the rest of the body
...



Lymphoedema

This is swelling of tissues due to faults in the lymphatic system
...


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