Anatomy Pre-Reading Material Flashcards
Extra detail
What is the defining feature of the human circulatory system?
Closed double system
How is the circulatory system a closed system?
Blood is contained within the blood vessels (like in all vertebrae)
Substances enter and exit, but the blood tissue doesn’t
How is the circulatory system a double system?
Blood passes through the heart twice in a complete circulation
Blood travels through the pulmonary division to become oxygenated, returns to the heart, then travels through the systemic division to deliver oxygen to the bodily tissues
What are the names of the broad groups of blood vessels involved with the circulatory system?
Arteries, veins, and capillaries
What is the route (via blood vessels) that the blood takes form the heart?
Heart–>Arteries–>Arterioles–>Capillary bed–>Venules–>Veins–>Heart
What is the main role of the arteries?
To carry blood away from the heart
How are arteries well adapted for their job?
Thick walls to withstand the pressure generated by ventricular contraction
Narrow lumen to maintain high blood pressure needed to facilitate blood flow
Elastic muscle fibres in the walls, allowing the arteries to stretch and recoil in response to changing pressure
Smooth muscle to allow the arteries to constrict or dilate to adjust blood flow to an area
What is the name of the smallest arteries?
Arterioles
What is the physiological significance of the capillaries?
Site of exchange between the blood and the surrounding environment
What does the term “capillary bed” refer to?
The meshwork pattern of interconnecting capillaries throughout a tissue
What are some key features of capillaries?
Large surface area to volume ratio
As narrow as possible- only one erythrocyte wide
Very narrow wall (simple squamous epithelium)
Facilitate rapid transport
Bruises are aa result of damage done to capillaries
What is the relation between capillaries and arteries?
Blood travels from arteries to arterioles, and then capillary beds
Arteries can constrict or dilate to reduce or increase the amount of blood travelling into a capillary bed
What are capillary beds typically followed by and what is an exception?
Typically followed by venules (smallest veins)
The glomerulus in the kidney is a key exception, reflecting it different pressure and function (ultrafiltration)
Why are veins important for bloodflow?
Drain blood away from tissues, typically towards the heart but sometimes to a second structure before doing so
What are key features of veins?
Only need a thin wall as blood pressure inside them is so low
Wide lumen to accommodate a large volume of blood (approx. 70% of blood is in the veins)
Why do the veins accumulate a large volume of blood?
Partly due to slow flow of blood, but also acts as a reservoir which can be accessed when demand increases
What is the function of portal veins?
Drain blood from one capillary bed to deliver it to a second set of capillaries elsewhere
What is an example of a portal vein
Largest example is the hepatic portal vein
Drains blood from the intestines to the liver for detoxification of digested substances
What is the path of movement for fluids?
Move from areas of high pressure to areas of lower pressure
Fundamental mechanism controlling blood flow throughout the body
How does ventricular systole (contraction) affect blood flow?
Ventricular systole generates a large amount of pressure, so the blood flows from ventricles into the slightly lower pressure arteries
Why are semilunar valves important during ventricular diastole (relaxing)?
During ventricular diastole the ventricles are under low pressure, so the blood would flow back to them, and the semilunar valves prevent this from occurring
Why does the heart not pump blood through the veins?
pressure decreases further away form the heart, so the blood flows away from it through the arteries
Once it has passed through the capillaries most of the pressure generated by the heart has been lost
What are some of the various ways in which blood flows through the veins?
Skeletal muscle pumps: contractions cause the veins between them to squeeze blood out
Respiratory pump: changing pressure of the thorax during breathing. When breathing in the pressure in the thorax decreases drawing air into the lungs, and so draws blood into the thoracic veins from lower veins
Some veins travel along arteries. Arteries expand/recoil with the changing pressure through the cardiac cycle, and so press on the veins and squeeze the blood out of them
General movement of the body will cause blood in the veins in that area to move through momentum
Gravity can bring blood back to the heart, e.g., blood in the head and the neck will typically drop straight down into the superior vena cava
What is significant regarding the various ways that blood moves through the veins?
They do not necessarily make the blood move towards the heart and could instead cause blood to move backwards. Backwards flow of blood is prevented by one-way valves in the veins. If the blood must move and can’t go backwards, it will go forwards.