Cardiovascular and Circulatory Systems Flashcards
Circulatory System
CV System + Lymphatic System
Function
- Distribution of gases and other molecules
- Chemical signalling
- Mediate information and host defence responses
CV System - 3 main components
Arterial System - Arteries carry blood away from heart
Heart - pump of system
Venous System - Veins carry blood towards heart
Pulmonary Circulation
Lungs oxygenate the blood
RV to the Lungs via the pulmonary arteries and back to LA via the pulmonary veins
Systemic Circulation
LV to the rest of the body via the aorta and branches
Heart
Muscular double pump
- Systole (contraction)
- Diastole (relaxation)
Vena cavae (x2) –> RA –> RV –> Pulmonary Arteries –> Lungs –> Pulmonary Veins (x4) –> LA –> LV –> Aorta –> Rest of Body
Walls of Heart
Epicardium (external) - outermost serous pericardium
Myocardium (middle) - muscular layer
Endocardium (internal) - continuous with basal membrane of blood vessels connecting with heart
Heart Chambers
Right Atrium
RIght Ventricle
Left Atrium
Left Ventricle
Great Vessels
Superior and Inferior Vena cava
Pulmonary Trunk
Aorta
Pulmonary veins
Valves
Atrioventricular (2/3 cusps)
- Left = Mitral
- Right = Tricuspid
Semilunar
- Aortic (LV)
- Pulmonary (RV)
Conduction System of Heart
- Electrical impulse starts spontaneously at SA node (causing both atria to contract)
- Travels to Atrioventricular Node at atrioventricular septum
- Travels down right and left bundles in Bundles of His
- Spreads out to myocardium through conducting fibres (causing both ventricles to contract)
Blood Vessels
Arteries –> Arterioles –> Capillaries –> Venules –> Veins
3 layers:
- Tunica intima (internal) - endothelium
- Tunica media (middle) - smooth muscle and elastic fibres
- Tunica adventitia (external) - connective tissue
Arteries
Often part of a neurovascular bundle - artery/vein/nerve
High pressure (80-100mmHg)
Deeper than veins
Round lumen, pulsatile, carry oxygenated blood
Give rise to arterioles
Bifurcate or trifurcate
Supply a territory
Common or Trunk - divide again
Arterioles
Smooth muscle in arterioles can contract to narrow lumen
Vasodilation - relaxation of SM and widening lumen –> Increase Blood flow
Vasoconstriction - contraction of SM to reduce blood flow
Sympathetic Tone
- Background low level of contraction of SM
- Due to tonic (continuous) conduction of action potentials to arterioles by sympathetic nerves
- Arteriolar SM contraction can help to reduce blood loss following injury
Anastomoses
Direct connections between small arteries and small veins, with no capillary section between them
E.g. Circle of Willis is an arterial anastomosis of the brain (may prevent strokes)
End Arteries and Infarction
End artery –> only arterial blood supply to a given area
Untreated occlusion of end artery –> infarction
Infarction - irreversible cell death due to hypoxia caused by loss of arterial blood supply
Aorta
Oxygen-rich arterial blood enters aorta first
Receives blood at high BP during systole
Its elastic walls expand under this pressure
Elastic recoil maintains peripheral flow during diastole
Aorta has many branches which supply body
4 parts of aorta
- Ascending aorta
- Arch of Aorta
- Descending aorta
- Abdominal aorta
Branches of Arch of Aorta
Brachiocephalic trunk
Left common carotid artery
Left subclavian artery
Upper Limb Blood Supply
Left Subclavian artery
Left Axillary artery
Left Brachial artery
Left Radial artery
Left Ulnar artery
Branches to supply abdominal organs
Common Iliac arteries (L&R)
Internal Iliac artery
External Iliac artery
Peripheral Pulses
Carotid
Brachial
Radial
Femoral
Popliteal
Dorsalis pedis
Veins
Often run in a neuromuscular junction
De-oxygenated blood
Low pressure and non-pulsatile
Drain blood away from territory
Have tributaries
Thin walled which collapse when empty
Valves
Venous return
Venous blood flow assisted by:
- Venous valves
- Skeletal muscles
- Venae comitantes (arterial pulsation pushes venous blood along)
2 Sets of Veins
Superficial Veins - smaller and run in superficial fascia
Deep Veins - larger and run deep to deep fascia and in cavities
Two main venous systems
Portal Venous system - drains venous blood from GI tract and associated organs to portal vein
Systemic Venous system - drains venous blood from all other organs and tissues into superior or inferior vena cava
Capillaries
Extnesive vascular networks
Lined with single layer of endothelial cells
Allow only one RBC through at a time
Allow exchange of gases, metabolites and waste products
Excess fluid from capillary squeezed out into lymph capillary where it get transports back to large veins in neck
Lymphatic Circulation
Lymphatic capillaries collect tissue fluid
Called lymph once in lymphatic capillaries
Lymphatic carry lymph through lymph nodes
Eventually lymph is returned to large veins n root of neck
Right lymphatic drains lymph into right venous angle
Thoracic duct drains lymph into left venous angle
Lymph nodes
Normal –> cannot usually be palpated
Infection/Cancer –> usually enlarge and can be palpated
