Circulatory Flashcards
As animal body plans evolved to further complexity, what happened with the circulatory system?
A need developed for a circulatory system that could transport materials such as nutrients, oxygen, and waste products throughout the body.
What is the circulatory system of the simplest multicellular animals and what is an example of one?
Almost all cells are in contact with the external environment, meaning that there is almost no need to transport materials internally. Cells got their nutrients from the surrounding water and expelled waste directly back from where it came. Example: cnidarian
Describe the circulatory system of an annelid.
Simple closed circuit of blood vessels with five small hearts, which are pulsating vessels
Describe the circulatory system of insects and other arthropods
Open circulatory system; basically bathes internal organs in blood all of the time. It consists of one dorsal vessel that pulsates, which keeps the blood moving.
Describe the circulatory system of vertebrates
Vertebrates have evolved an intricate closed circulatory system that consists of a heart and three principal types of blood vessels: arteries, capillaries, and veins
What are arteries?
Blood vessels that carry blood away from the heart. They have thick but elastic walls, allowing them to dilate or contract (which controls blood pressure). Arterial blood pressure is usually high because it was recently pumped from the heart.
Describe the blood in arteries
Usually oxygen rich because it is being pumped out to the body to provide oxygen and other nutrients to the cells.
Why are the pulmonary arteries special?
They carry blood that isn’t oxygen rich because they carry blood to the lungs to pick up oxygen but haven’t gotten there yet.
What can’t arteries do?
They can’t service each cell in the body because they are too large. So, as arteries get farther and farther from the heart, they branch into smaller and smaller vessels, which eventually branch into capillaries. Capillaries later merge into larger and larger vessels, eventually becoming veins.
What can capillaries do?
Because the walls of capillaries can be as thin as one cell thick, they easily allow nutrients, waste products, oxygen, and carbon dioxide to diffuse between blood and surrounding tissues.
What can veins do?
They carry blood toward the heart. They contain unidirectional valves to ensure that the blood in veins flows toward the heart.
Describe blood in veins
It isn’t pushed by the pumping of the heart, meaning that the blood pressure and forward momentum is lower than in arteries. It is pushed by the contractions of the skeletal muscles. Venous blood has already provided nutrients to cells, so it is deoxygenated (blue).
Describe the pulmonary veins - why are they special?
They carry blood to the heart from the lungs, meaning that they just picked up oxygen and carry bright red blood.
As vertebrates have evolved, what happened?
They have developed increasingly efficient circulatory systems
Describe the circulatory system in fish
One closed loop: blood is pumped from the heart to the gill capillaries, where oxygen is picked up from the surrounding water. The blood then continues on to the body tissues, and the vessels eventually become capillaries again to allow for nutrient and gas exchange in the tissues. Then the deoxygenated blood is returned to the heart and pumped to the gills
Why is the fish circulatory system inefficient
Because the blood loses a lot of momentum in the gill capillaries. After leaving the gill capillaries, it travels slowly and with a lower pressure, affecting the delivery of oxygen to the body tissues
Which animals have solved this problem and how did they do so?
Amphibians, reptiles, birds, and mammals solved the problem. They solved it by evolving two circuits within the c.system: pulmonary circuit and systemic circuit. After the blood is pumped from the heart to the lungs to be oxygenated, it is returned to the heart before it is pumped out to the rest of the body.
Why are amphibian and reptile hearts inefficient
Because they make no distinction between oxygenated and deoxygenated blood. Their hearts have two chambers: one chamber that receives blood from lungs and one that pumps blood back out. This means that oxyrich and oxypoor blood mix as oxyrich blood returns from lungs and oxypoor blood returns from systemic circuit. The blood pumped to the body never has as much oxy as it could
Describe the avian and mammalian heart
Four chambered. It has two halves, one for oxyrich and one for oxypoor blood. Each half has an atrium and a ventricle. Path of oxypoor blood: r atrium, r ventricle, pulmonary artery, lungs (+oxy -co2) where it becomes oxyrich, pulmonary veins, l atrium, l ventricle, aorta, arteries + arterioles + capillaries. Provides oxy, picks up co2, goes into veins. (Is deoxygenated) then flows through superior and inferior vena cavas into r atrium.
What are the atria and ventricles separated by
One way atrioventricular valves
What is the atrium
The chamber where blood returns to the heart
