S13) Cardiovascular System Flashcards
What are the functions of the cardiovascular system?
- Circulate and transport nutrients, hormones, O2 and CO2
- Fight disease
- Maintain homeostasis (temperature & pH)
What are the components of the cardiovascular system?
- Heart
- Blood
- Blood vessels
What is pulmonary circulation?
Pulmonary circulation is a “loop” through the lungs where blood is oxygenated
What is systematic circulation?
Systemic circulation is a “loop” through the rest of the body to provide oxygenated blood and receive deoxygenated blood
An average adult has 5.0 litres of circulating blood.
Explain the distribution of this blood in the human body
- 3.25 litres ⇒ veins
- 1.0 litre ⇒ heart and lungs
- 0.5 litres ⇒ peripheral arteries
- 0.25 litres ⇒ capillaries
What is collateral circulation?
Collateral circulation is the alternate circulation around a blocked artery or vein via another path, such as nearby minor vessels
What is an end artery?
An end artery is a terminal artery supplying all or most of the blood to a body part without significant collateral circulation
What happens when end arteries are occluded?
Why does this happen?
- If occluded, there is insufficient blood supply to the dependent tissue
- End arteries undergo progressive branching without the development of channels connecting with other arteries
Identify some examples of end arteries
- Coronary arteries
- Splenic artery
- Cerebral arteries
- Renal arteries
What happens during systole?
In systole, the left ventricle contraction causes the blood pressure in the aorta to rise to approx. 120 mm Hg (systolic pressure) and the walls of the aorta expand
What happens during diastole?
In diastole, the aortic semilunar valve closes and the walls of the aorta recoil, causing pressure to drop to 80 mmHg (diastolic pressure), moving blood towards the heart and smaller vessels
What are the three layers of arteries and veins?
- Tunica intima
- Tunica media
- Tunica adventitia/externa
What do smooth muscle cells do in blood vessel walls?
Produce elastin, collagen and matrix
What is an aneurysm?
An aneurysm is a dilatation of a blood vessel
Why are most abdominal aortic aneurysms infrarenal?
- The mechanical tension in the abdominal aortic wall is higher than in the thoracic aortic wall
- The diameter decreases from the root to the aortic bifurcation
- The infrarenal aorta contains a less elastin
Describe the properties of the tunica intima of muscular arteries
- Endothelium
- Subendothelial layer
- Thick internal elastic lamina
Describe the features of the tunica media of muscular arteries
- Many layers of smooth muscle cells
- Cells are connected by gap junctions for coordinated contraction
- Prominent external elastic lamina
Describe the features of the tunica adventitia of muscular arteries
- Thin layers of fibroelastic connective tissue
- Contains vasa vasorum, lymphatic vessels and nerve fibres
What are arterioles?
Arterioles are arteries with a diameter of less than 0.1 mm
Describe the wall of arterioles
- Tunica intima: endothelial cells and subendothelial connective tissue
- Tunica media: 1 layer of smooth muscle cells
- Tunica adventitia: layers of fibroblasts
What are metarterioles?
Metarterioles are arteries that supply blood to capillary beds
What are precapillary sphincters?
Precapillary sphincters are individual muscle cells that each encircle the endothelium of a capillary arising from the metarteriole
What do precapillary sphincters do?
- Each smooth muscle cell is believed to function as a precapillary sphincter
- They contract to control blood flow into the capillary bed (regulators)
What do lymphatic capillaries do?
Lymphatic capillaries drain way excess extracellular fluid, returning it to the blood at the junctions of the internal jugular and subclavian veins
