Circulation Flashcards
What are the two types of circulatory systems?
The open circulatory system and the closed circulatory system.
What is an open circulatory system?
- It consists of a fluid called hemolymph (interstitial fluid)
- Hemolymph is pumped into body cavities known as sinuses.
- Arthropods and most mollusks have this system
What is a closed circulatory system?
- Blood moves in vessels
- Annelids and all vertebrates have a closed circulatory system
- High blood pressures are seen which allow for more effective O2 and nutrient delivery to body cells.
What are the three types of vessels?
- Arteries, veins, and capillaries are the three main types of vessels.
Describe arteries
- They are under high pressure and they are rich in O2. - - They carry blood away from the heart.
- They are strong and elastic with 3 distinct layers with thick walls.
- They get progressively smaller and make way to arterioles. These convey blood to capillaries and also have three layers
Why is resistance the highest in arterioles? Why is this significant?
There is the biggest drop in diameter from arteries to arterioles. The drop in diameter increases the surface area blood must travel against, increasing resistance. Capillaries also have a small diameter, but they are more numerous, therefore there is less resistance overall.
Due to their high resistance, arterioles are the perfect place for the body to control blood flow and blood pressure by vasoconstriction or vasodilation of the arterioles.
What are the three layers of arteries?
- An outer layer (tunica adventitia) of connective tissue with collagen fibers.
- A middle layer (tunica media) of circularly arranged smooth muscle and elastic fibers.
- An inner layer (tunica intima) (endothelium), consisting of a specialized simple squamous epithelium, often called the endothelium, that lines all blood vessels and the endocardium of the heart.
- The basement membrane, a subendothelial layer composed of connective tissue, supports the endothelium and resides between the endothelium and the tunica media
Describe capillaries
- They are distributed throughout all body tissues
- Smallest blood vessels
- Single layer of squamous epithelium
- Speed of blood is the slowest
- The thin walls allow for easy substance exchange (O2 and nutrients) through diffusion mostly.
- Largest cross sectional area of any part of the circulatory system. (There are so many capillaries, that despite their very small size, all of their cross sections added up is larger than any other part of the circulatory system. This is also why the blood speed is so slow, as cross section size is inversely proportional to blood flow speed. )
- Capillaries converge into a venule, which then converge into veins.
Describe Veins
- There is very little blood pressure remaining by the time the blood gets to the veins, due to the slow down of the blood from the capillaries.
- Veins are high in CO2 concentration generally
- They also have three layers, but they are thinner and have less smooth muscle and less elasticity than arteries.
- Many veins have valves
- Due to the low blood pressure, valves are needed to prevent the backflow of blood while muscle contractions push the blood along the veins toward the heart.
Describe how capillaries filter liquid and nutrients out of capillaries and then back in.
When blood first enters the arterial end of the capillary there is a high blood pressure. The blood pressure pushes liquid into the interstitial space through the thin layer of squamous cells lining the lumen of the capillaries. This is called filtration. As the blood moves toward the venous end of the capillaries, the blood pressure moves to essentially nothing. The osmotic pressure of the blood proteins brings liquid back into the blood before it moves into the veins. The osmotic pressure doesn’t bring all of the liquid back into the cell through reabsorption. Any additional liquid not brought back in, is pumped through unidirectional lymphatic vessels with valves to prevent backflow. These lymphatic vessels eventually dump their lymph into the subclavian veins.
How many chambers do each of the following organisms’ hearts contain?
Mammals Birds Reptiles Amphibians Fish
NB: Must know for the DAT
- Mammals: 4
- Birds: 4
- Reptiles: Most have 3. Crocodiles and Alligators have 4 though
- Amphibians: 3
- Fish: 2
Atria
Upper Chamber
Ventricle
Lower Chamber
Superior Vena Cava
Brings blood low in O2 to right atria from upper body.
Cave Venue for RADEO show
RADEO - Right Atrium Deoxygenated
Inferior Vena Cava
Brings blood low in O2 to right atria from lower body
Cave Venue for RADEO show
RADEO - Right Atrium Deoxygenated
