Presentation on theme: "Bell Work 1.What is the difference between a vein and an artery? 2.What is blood pressure? 3.What is cardiac output? 4.What is resistance? 5.What does."— Presentation transcript:
Bell Work 1.What is the difference between a vein and an artery? 2.What is blood pressure? 3.What is cardiac output? 4.What is resistance? 5.What does the word constriction mean? 6.What do the prefixes hypo- and hyper- mean?
Blood Vessels, Blood Pressure and Capillary Beds Oh my.
Blood Vessels When it comes to blood, your body is a giant closed system with heart as the pump. To complete this huge circulatory task of delivering blood to all the body parts, the body has several types of blood vessels. Blood is propelled from the heart into large arteries, which gradually branch into smaller arteries. Branching off of arteries are arterioles, which feed capillaries. Capillaries drain into venules, which empty into veins which return the blood to the heart.
Anatomy of Blood Vessels Blood vessels are composed of three layers or tunics – Tunica intima – the inner layer that is composed of endothelium that form a smooth, slick surface. – Tunica media – the bulky middle layer that is composed of mainly smooth muscle and elastic tissue. – Tunica externa – the outer layer that is composed of fibrous connective tissue that supports and protects the vessels
Differences in blood vessels Arteries are thicker, especially in the tunica medula, so it can withstand the forces coming from the heart Veins are thinner due to decrease pressure but larger veins need valves to prevent backflow and muscle activity to help “squeeze” the blood back to the heart Capillaries are usually only one cell thick (just the tunica intima layer) to promote gas and nutrient exchange.
More about capillaries They are intricate branching networks of thin blood vessels at the end of arteries This area is also known as a capillary bed The flow from the arteriole to the venule is known as microcirculation. They are composed of two types of vessels, the vascular shunt (directly connects arteriole and venule) and the true capillaries (exchange vessels, where various materials can flow into and out of the cells and bloodstream.) True capillaries (and thus exchanges) can be “turned off” by the body by using precapillary sphincters
Use page 361 to draw and label the various type of blood vessels.
The four different routes for exchange Direct diffusion – can occur if materials are lipid soluble. In this case they can pass straight through the plasma membrane Vesicle transportation – lipid insoluble materials enter into tiny capsules called vesicles and can to transported in (endocytosis) or out (exocytosis) Limited passage through intercellular clefts (gaps in the plasma membrane) Fenestrated capillaries – an oval pore (opening) known as a fenestra that is covered with a thin permeable membrane
Fluid Movement Fluid movement depends on two pressures Blood Pressure – tends to force fluid outward Osmotic Pressure – tends to draw fluids in As a rule, blood pressure is higher at the arterial end of the capillary bed and osmotic pressure is higher at the veneous end. The result is fluids move out at the beginning of the capillary bed and are reclaimed at the end.
Use page 380 (especially picture b and c) to draw a summary of the different type of capillary transport mechanisms
What is Blood Pressure The pressure the blood exerts against the walls of the blood vessels It is also the force that keeps the blood circulating continuously between heart beats It moves from areas of high pressure to low pressure
Measuring Blood Pressure Systolic Pressure – the pressure in the arteries at the peak of ventricular contraction (top number) Diastolic Pressure – the pressure when the ventricles are relaxing (bottom number)
What effects blood pressure? It is related to – Cardiac output – the amount of blood pumped out of the left ventricle per minute – Peripheral resistance – the amount of friction encountered by the blood as it flows through the blood vessels
What can change these? Neural factors – autonomic nervous system changes that causes vasoconstriction (narrowing of the blood vessels) and increase blood pressure Renal factors that involve the kidneys – the kidneys can alter the blood volume. Less volume means less pressure. Temperature – cold temperature causes vasocontriction while heat causes vasodilation Chemicals Diet
Variations in Blood Pressure Hypotension – low blood pressure, usually a good thing Orthostatic hypotension – results from an aging sympathetic nervous system and its slower reaction times, it causes older individuals to free dizzy or fainting when quickly rising from a reclined or seated position Hypertension – high blood pressure, higher pressures strain the heart and weaken it over time