8 - Transport in animals Flashcards
1
Q
why do multicellular organisms need a transport system?
A
- diffusion alone is too slow to meet the organism’s needs.
- relatively high metabolic demand and rate.
- small SA:V ratio, diffusion distance increases ad surface area for diffusion becomes relatively smaller..
- SA:V ratio gets smaller as organisms get bigger.
- waste products of metabolism need to be removed.
- molecules like hormones and enzymes may be produced at one place but needed in another place.
2
Q
common features of circulatory systems?
A
- they have a liquid transport medium (blood) that circulates around the system.
- vessels that carry the liquid transport medium.
- pumping mechanism to move the liquid transport medium around the system
3
Q
open circulatory system
A
- few vessels to contain the blood. Blood isn’t contained in blood vessels all the time.
- blood is pumped from heart straight to body cavity of the animal.
- blood comes into direct contact with tissues/cells.
- blood returns to heart through an open-ended vessel.
- amount of blood flowing to a particular tissue cannot be controlled.
found in:
- invertebrates
- most insects
- molluscs
- in insects, open circulatory system transports nutrients and nitrogenous waste products.
- oxygen is transported by the tracheal system.
4
Q
closed circulatory system
A
- blood is enclosed inside blood vessels.
- blood does not come into direct contact with tissues/cells.
- substances leave and enter body cells by diffusing through walls of blood vessels.
- heart pumps blood around body and blood returns directly to the heart through blood vessels.
- amount of blood flowing to a particular tissue can be controlled - by widening or narrowing blood vessels.
- single closed circulatory systems:
fish
double closed circulatory systems:
mammals
5
Q
single closed circulatory system
A
fish
annelid worms
- blood flows through heart once for each complete circulation of the body.
in fish, heart pumps blood to gills, then rest of body, then returns to heart in a single circuit.
6
Q
double closed circulatory system
A
mammals
- blood flows through heart twice for each complete circulation of the body.
- blood is pumped from heart to lungs (oxygen collected, CO2 unloaded)
- blood is pumped from heart to rest of body and returns to the heart.
7
Q
elastin fibres
A
- composed of elastin
- can stretch and recoil
- provides vessel walls with flexibility
8
Q
smooth muscle
A
- contracts or relaxes to change the size of the lumen.
- contracts: constricts the blood vessel (lumen decreases in size).
- relaxes: dilates the blood vessel (lumen increases in size).
9
Q
collagen
A
- provides structural support to maintain shape and volume of vessels.
10
Q
Arteries and arterioles
A
- arteries carry blood from heart to tissues in the body.
- oxygenated blood (but pulmonary artery carries deoxygenated blood from heart to lungs).
- elastic fibres for stretching and recoiling of artery helps to maintain high pressure.
- folded endothelium allows artery to expand. Helps to maintain pressure.
- smooth endothelium reduces resistance of blood flow.
Arterioles:
- less elastic fibres in walls: little pulse surge.
- more smooth muscles: arterioles contract/dilate to control flow of blood to individual organs.
11
Q
Why is aorta biggest, has most elastin fibres, and collagen?
A
- connecting directly to the heart, pressure is greatest here.
- lots of elastic fibres to maintain the very high pressure, to ensure that the blood is pumped to all areas of the body.
- lots of collagen to prevent bursting (due to very high pressure).
12
Q
What is the trend of the different tissues in arteries with increasing distance from heart?
A
as distance from heart increases:
- amount of elastin decreases
- amount of smooth muscle increases and then decreases, but with there being more smooth muscle in arteriole than aorta.
- amount of collagen decreases dramatically but then increases slightly.
13
Q
capillaries
A
- microscopic blood vessels
- links arterioles with venules.
- tiny lumen, red blood cells travel in single file.
- substances are exchanged with tissues and blood through capillary walls.
- 1 cell thick endothelium (short diffusion distance)
how are they adapted to their role:
- lots of them, provides a very large surface area for diffusion of substances.
- total cross sectional area of capillaries is greater than arterioles, so blood slows down when entering capillaries. Provides time for diffusion of substances.
- 1 cell thick endothelium. Short diffusion distance.
14
Q
Veins and venules
A
- veins carry blood from body cells to heart.
- deoxygenated blood (but pulmonary vein carries oxygenated blood from lungs to heart)
- deoxygenated blood from capillaries, then venules, then larger veins, then inferior vena cava (lower body) and superior vena cava (head and upper body).
- no pulse (surge lost from passing through narrow capillaries).
- large blood reservoir (60% of blood volume at any one time)
- low blood pressure: has valves to prevent backflow of blood
- lots of collagen
- little elastic fibres
- wide lumen
- smooth endothelium: reduces resistance of blood flow.
venules:
- link capillaries with veins.
- thin walls, little smooth muscle.
- several venules join to form vein.
15
Q
How is the deoxygenated blood in the veins moved back to the heart (low pressure)?
A
- one way valves at intervals prevent backflow of blood.
- many bigger veins run along active muscles such as arms and legs. When they contract, veins are squeezed, forcing blood towards heart. When they relax, valves help to prevent backflow.
- Breathing movements and changes in pressure move blood in veins of chest and abdomen towards heart.
16
Q
What is the trend of the different tissues in veins with increasing distance from heart?
A
As distance from heart increases:
- amount of elastin decreases with no elastin in venules
- amount of smooth muscle decreases with no smooth muscle in venules.
- amount of collagen decreases slightly.
17
Q
What is blood composed of?
A
55% plasma
45% erythrocytes, leucocytes, platelets
18
Q
Functions of blood?
A
- transport oxygen and CO2 to and from cells.
- transport digested food from small intestine.
- transport hormones
- transport platelets to wounds
- transport cells and antibodies in immune response.
19
Q
What is tissue fluid?
A
- composed of plasma leaked through gaps in capillary walls.
- fluid that surrounds cells of tissues.
- consists of no plasma proteins, very few white blood cells, no red blood cells, water, dissolved solutes.
- responsible for exchange (cells take up oxygen and nutrients from tissue fluid and release metabolic waste CO2 into tissue fluid).
Why are red blood cells and most plasma proteins not in tissue fluid?
- they are too large to fit through the gaps in the capillary walls.
20
Q
How is tissue fluid formed?
A
- arterial end (start) has a high hydrostatic pressure.
- oncotic pressure (plasma proteins remain in capillaries.) stays the same.
- hydrostatic pressure is greater than oncotic pressure.
- plasma is forced out of the capillary through gaps in the walls and forms tissue fluid.
- venous end (end) now has a lower hydrostatic pressure than the oncotic pressure
- oncotic pressure stays the same.
- water potential is lower is lower in capillary.
- moves moves back into capillaries by osmosis raising the hydrostatic pressure.
21
Q
What is lymph? How is it formed?
A
- not all tissue fluid returns to the capillaries.
- 10% of tissue fluid drain into blind-ended lymph vessels, and is known as lymph
- contains less oxygen and fewer nutrients than tissue fluid and plasma.
- fatty acids (from small intestine).
- white blood cells
- water
- dissolved solutes.
- antibodies
Lymph drains back into capillaries as blood plasma via lymph vessels.
22
Q
What are lymph nodes?
A
- Along the lymph vessels, there are lymph nodes.
- they produce lymphocytes
- lymph nodes filter bacteria and foreign matter from the lymph (fluid). They are digested by phagocytes in the nodes.
