Valves and Vessels Flashcards
What is the function of the valves?
Ensure blood flows in the correct direction by opening to allow blood through and closing to prevent back flow.
Describe the structure of the AV valves.
- Consist of fibrous ‘cusps’; the left valve has two and the right has three (2 in a dog).
- Have chordae tendinae which attach the free edges of the cusps to the papillary muscles in the walls of the ventricle.
- There is also a fibrous ring surrounding the valve; the annulus fibrosus.
What is the role of the AV chordae?
Prevent the cusps from
everting into the atrium during ventricular systole.
Describe the structure of the semilunar valves.
- Made up of 3 seminar shaped cusps which meet tightly in the middle due to thickening of the contact areas.
- Supported by annulus fibrosis.
What is another role of the annulus fibrosis (besides fibrous skeleton)?
Serves as an electrical insulation between atria and ventricles.
What causes the valves to open and close?
Changes in pressure
Define regurgitation.
Blood flowing in the wrong direction.
What are stenotic valves?
Narrowed - blood unable to pass through as easily.
What type of arteries are found near the heart and give an example.
Large elastic arteries e.g. aorta.
Where are muscular arteries found and how are they composed?
Large amount of smooth muscle; found further from the heart than elastic arteries.
Describe the structure of arterioles.
Thinner layer of smooth muscle; no significant elastic.
Describe the function of elastic arteries.
Act as pressure reservoirs to maintain continuous blood flow during diastole.
Describe the function of muscular arteries.
Regulate blood flow to specific organs by constricting or dilating (vasoconstriction/vasodilation).
Describe the function of arterioles.
Control peripheral resistance and regulate blood flow into capillary beds.
Describe the structure and function of venues.
Some smooth muscle in their walls and act as a blood reservoir.
Describe the structure of veins.
- Walls contain smooth muscle and some elastic fibres, but thinner than their satellite artery.
- Valves
Describe the function of veins and valves in veins.
- Take blood back to the heart.
- Prevent the back flow of blood.
Why is blood flow in the capillaries much slower?
Gives time and surface area for the
rapid exchange of substances between the blood and ISF.
Explain the three basic layers make up arteries and veins.
- Tunica intima - internal layer with an endothelial lining.
- Tunica media - middle layer which contains varying amounts of smooth muscle and elastic tissue.
- External tunic adventitia - layer of connective tissue.
Describe the junctions in the capillaries.
- Gap junctions - between overlapped ends of endothelial cells and allow movement of water soluble molecules.
- Tight junctions - form a continuous seal.
What are the main branches of the aortic arch in domestic mammals?
- Brachiocephalic trunk: divides into subclavian arteries and common carotid arteries.
- Left subclavian artery: Independent in some species (e.g., dogs and cats).
What is the function of the azygous vein?
Drains blood from the thoracic wall and dorsal body into the cranial vena cava (in ruminants and dogs).
What structures drain into the cranial vena cava?
- Jugular veins
- Subclavian veins
- Brachiocephalic veins
What structures drain into the caudal vena cava?
- Hepatic veins (from the liver)
- Renal veins (from the kidneys)
- Iliac veins
