Flashcards in Chapter 6- The Blood System Deck (42)
What did arteries do? Overview
Arteries are vessels that convey blood from the heart the tissues of the body
What do arteries do? In depth?
1) the main pumping chamber of the heart are the ventricles - they have thick strong muscles in their walls that pump blood into the arteries
2) artery walls work with the heart to facilitate and control blood flow
What are the two tissues in the walls of arteries that help control blood flow?
Elastic and muscle tissue- contribute to toughness of wall and withstand constantly changing blood pressure
What is each organ supplied with blood by? 2 major examples be
By the arteries
Kidney- renal artery
Liver- hepatic artery
What are the 3 layers that the artery is composed of?
1) tunica external- a tough outer layer of connective tissues
2) tunica media- a thick layer containing smooth muscle and elastic fibres
3) tunica intimidate - a smooth endothelium forming the lining of the artery
What do the muscle and elastic fibres assist in?
Maintaining blood pressure between pump cycles
What is systolic pressure?
Blood entering arteries is at high pressure- peak pressure reached is called systolic pressure- pushes wall of artery outwards, widening lumen and stretching elastic fibres in wall; thus storing potential energy
What happens at the end of each heartbeat?
The pressure in the arteries falls sufficiently for the stretch elastic fibres to squeeze the blood in the lumen - saves energy and prevents mim. Pressure in artery (diastolic pressure)
What is vasoconstriction?
Circular muscles in the wall the artery form a ring so when they contract, the circumference is reduced and the lumen narrowed- increases blood pressure in arteries
What does vasoconstriction do?
Or arterioles Restricts blood flow to part of the that they supply (opposite is vasodilation)
What do capillaries do?
Blood flows through tissues in capillaries with permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary
What are capillaries?
Capillaries are the narrowest blood vessels
What is the main role of capillaries?
To transport blood through almost all tissues in the body
The walls of capillaries are very permeable what does allow?
Allows part of plasma to leak our and form tissue fluid- contains oxygen, glucose etc - fluid flows btween the cells and tissue allowing the cell to absorb useful substances and excrete waste products- then re-enters capillary network
What does veins do?
Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart
Where do veins transport blood from?
From capillary networks - blood is at much lower pressure than it was in arteries so walls are not as thick as arteries - can therefore dilate to become much wider and hold more blood than arteries
What is blood flow in veins assisted by?
Gravity and by pressures exerted on them by other tissues, especially skeletal muscles
What is the one anomaly in veins?
The hepatic portal vein - it does not carry blood back to heart instead it carries blood from the stomach to the intestines to the liver
What do valves in veins do?
Valves in veins and the heart ensure circulation of blood by preventing back-flow
How do valves stop back flow?
1) if blood starts to flow backwards, it gets caught in the flaps of the pocket valve, which fills with blood, blocking the lumen of the vein
2) when blood flows towards the heart, it pushes the flaps to the sides of the vein. The pocket valve therefore opens and blood can flow freely
What do valves ensure?
Blood flows in one direction
What are the lungs used by mammals for gas exchange supplied with blood by?
A separate circulation
Why is there a need for a separate circulation for lungs circulation in animals?
Blood capillaries in lungs cannot withstand high pressures so blood is pumped to them at relatively low pressure- so after passing through lungs blood pressure is low so much return to heart before going to other organs
What are the two types of circulations in humans?
1) pulmonary circulation - to and from lungs
2) the systemic circulation- to all other organs, including heart muscle
Why is it essential that the blood from both separate circulations do not mix?
As pulmonary circulation recjves deoxygenate blood that had returned from the systemic circulation and the systemic circulation recurve so blood that had been oxygenated by the pulmonary circulation
What are the causes of occlusion of coronary arteries
Lipoproteins (LDL) containing fats etc accumulate and phagocytes are attracted by signals from endothelium cells- smooth muscles cells migrate to form a tough cap over the at herons and artery walls budge- narrowing the lumen and impeding blood flow
Consequences of occlusion of coronary arteries
Leads to a lack of oxygen - causes pain, impairs the muscles ability to contract, heart beats faster as it tries to maintain blood circulation which can cause ruptures and then blood clots block arteries
Long term Consequences of occlusion of coronary arteries
1) high blood pressure
2) chronic high blood glucose conc.
What is the heart beat initiated by?
A group of specialised muscle cells in the right atrium called the sinoatrial node