Module 3- Transport in animals Flashcards
What can the direction of blood flow be controlled by?
Contracting the arterioles to restrict blood flow and relaxing to allow blood flow
What are venules?
-small blood vessels that collect blood coming out of capillaries
-blood flows from the vast network of capillaries into a network of fewer but larger venules and will eventually flow into veins.
What is the diameter range of a venule?
7 micrometers to 1 mm
What is the role of the artery and describe its features
-transport blood away from the heart into the organs
-artery walls have thick layers of muscle which maintain a high pressure so blood can be pumped around the body
-elastic fibres in the artery walls allow the arteries to stretch
-the endothelium is folded which also allows the arteries to stretch
What is the role and structure of veins?
-veins transport blood back to the heart
-the lumen is wider than the arteries which allows blood to flow at a low pressure
-there is a thin muscle wall and elastic tissue
-valves are located throughout the veins to ensure that blood flows towards the heart
What is the role and structure of capillaries?
-capillary walls (endothelium) are only one cell thick, this means that the diffusion distances are very short allowing for efficient gas exchange
-they pass very close to the body cells
-form networks (capillary beds) around body cells which create a large surface area
What is the structure and function of tissue fluids?
-transport substances via the tissue fluids
–combination of oxygen, water and nutrients
-surrounds cells in the body
-substances in the tissue fluid can diffuse or be transported into cells
What is pressure filtration?
where substances move into the tissue fluid from the capillaries
How is a high pressure gradient maintained?
-high volume of blood being forced through narrow capillaries creates high hydrostatic pressure in the capillaries at the entrance of the capillary bed
-this causes a high pressure gradient between inside the capillaries and outside
What causes a decrease in pressure in capillaries?
-movement of fluid out of the capillaries causes the hydrostatic pressure inside the capillaries to decrease
-so capillary bed pressure is lower at the entrance than at the exit
What is the water potential gradient?
-when fluid moves out of the capillaries, plasma proteins remain inside the capillaries
-the plasma protein concentration inside the capillaries increases and the water potential decreases
-a water potential gradient is established and water diffuses via osmosis back into the capillaries from the tissue fluid
-oncotic pressure pulls water back into the capillaries and is created by the increased plasma protein concentration.
-it is the opposite to hydrostatic pressure which forces pressure out of the capillaries.
What is the lymphatic system?
-excess tissue fluid flows into the lymphatic system
-it recycles the excess tissue fluid into the blood stream
Describe the flow of blood in the human body starting from deoxygenated blood flowing into the right atrium
1)deoxygenated blood flows into the right atrium from the body through the vena cava
2)when the walls of the right atrium contract, deoxygenated blood flows into the right ventricle
3)the atrioventricular valves prevent blood flowing back into the atria from the ventricles
4)the walls of the right ventricle contract and blood is pumped out of the pulmonary artery to the lungs
5)the semi lunar valves prevent blood flowing back into the ventricle from the pulmonary artery
6)oxygenated blood flows into the left atrium from the lungs through the pulmonary vein
7)when the walls of the left atrium contract oxygenated blood flows into the left ventricle (walls are a lot thicker than the right)
8)when the left ventricle contracts blood is pumped out of the heart through the aorta to the rest of the body.
