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Medicine Cardiovascular Basic Science Summary
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CVS BlockBasic Science Summary
Chaandanee Bhayroo
1420214
GEMP 1
,Functional and Clinical Anatomy of the CVS
The Vascular Tree
1. Transport blood to the tissues for O2 exchange
2. Removes waste products
3. Transports hormones and other endocrine products
• Arteries lie deep to the veins
• Run in same fascial sheath as vein and nerve = Neurovascular bundle
• Named according to their anatomical position/ function
• Arterioles regulate BP by controlling the flow to the capillaries
• Veins maintain pressure in capillary beds by holding blood volume
Histology
1) Tunica intima – endothelium, subendothelial CT, smooth muscle, IEL
2) Tunica media – smooth muscle, elastic fibres, collagen fibres, EEL
3) Tunica adventitia – collagen fibres, elastic fibres, vasovasorum
1) Elastic (>1 cm)
a. Stretch during systole and recoil during diastole
b. Aorta + pulmonary +its branches
2) Muscular (2-10 mm)
3) Small (0.1-2 mm)
a. 8-10 layers of smooth muscle
b. Greater cross-sectional area = greater impact on regulating BP
c. Anastomoses between multiple branches = detour channels
4) Arterioles
a. Very thin/absent subendothelial layer
b. 1-2 layers of smooth muscle
5) Metarteriole
a. Microcirculation
b. Precapillary sphincter controls blood flow into
capillaries
c. Thoroughfare channel allows blood to bypass
capillary bed
6) Capillaries (5-10 µm)
, a. Single layer of endothelium on a basement membrane
b. Pericytes secrete vasoactive substances which keep lumen patent,
vasoconstrict/dilate
c. Continuous = endothelial cells and basal lamina. Tight occluding junctions.
Pinocytotic vesicles. Pericytes. Lung, muscle and CNS
d. Fenestrated = continuous basal lamina and fenestrated endothelium covered by a
thin diaphragm. Diffusion. Pericyte. Kidney, intestine, endocrine glands
e. Discontinuous = discontinuous basal lamina with large irregular endothelial
fenestrations. Cells separated from each other. Maximum exchange. Liver, spleen
bone marrow
7) Arteriovenous shunts
a. Direct route between an artery and vein
b. Serve as thermoregulators and erectile response
c. Contraction shunts blood/ relaxation conserves blood
d. Found in skin of fingertips, nose, lips, penis + clitoris
8) Post capillary venule (10-50 µm)
a. Principle site of action of vasoactive agents and oedema formation
b. Endothelial cells
c. Extensive pericytes
d. No TM and TA
9) Muscular venules (50-100 µm)
a. 1-2 layers smooth muscle
b. Some elastic fibres
c. No pericytes
10) Small veins (0.1-1mm)
a. Subendothelial layer contains smooth muscle cells
b. 2-3 layers smooth muscle interspersed with reticular and elastic fibres
11) Medium veins (-10mm)
a. Endothelium form valves -prevents retrograde
movement of blood due to gravity
i. Musculovenous pump
ii. Counter-current heat exchange system
iii. Atriovenous pump
b. Relatively thin media and thick adventitia
12) Large veins (>10mm)
a. Include the SVC, IVC and hepatic portal vein
b. Relatively thin with a few layers of smooth muscle between abundant CT
c. Thick TA with elastic fibres and smooth muscle cells
Atypical blood vessels
1) Coronary arteries
a. Considered medium muscular arteries
b. Thicker
2) Dural venous sinus
a. Broad space representative of venous channels
3) Great saphenous vein
, a. Described as a muscular vein
b. Used for coronary artery bypass graft when internal thoracic not available
4) Central adrenomedullary vein
Lymphatic vessels
• Remove interstitial fluid
• Unidirectional
• Anchored to the tissue via filaments
• Has TI, TM and TA
• Unite into large vessels with valves (thoracic duct and right lymphatic duct)
• Interspersed with lymph nodes
• Drain into internal jugular and subclavian vein
Pericardium = fibrous serous membrane that allows the occlusion of the great vessels during surgery
& to hold and lift for better access
1) Fibrous layer – joins with the central tendon of the diaphragm, adventitia of vessels and
sternal ligaments. Prevents overfilling of the heart.
2) Parietal serous layer – mesothelium that lines fibrous pericardium.
3) Visceral serous layer – forms the epicardium.
Decreases friction
4) Transverse (between aorta and pulmonary trunk
anteriorly and the SVC and pulmonary veins
posteriorly) and oblique (between the left atrium
anteriorly and fibrous pericardium posteriorly)
sinuses
5) Pericardial cavity – between serous layers
Supplied by the pericardiophrenic vessels, phrenic nerve, vagus nerve and sympathetic trunks.
Pericarditis – fibrinous exudate, cardiac tamponade, pericardial effusion, constrictive pericarditis
Heart
Lies obliquely in the middle mediastinum
Layers of the Heart:
1) Endocardium – endothelium + CT + subendocardial layer (nerves, veins, purkinje fibres)
2) Myocardium – cardiac muscle in a complex spiral
3) Epicardium – mesothelium + CT+ subepicardial layer (adipocytes, vessels, nerves)
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