Transport in Animals Flashcards
What is the need for transport systems in multicellular animals?
o Size – larger organisms (2+ levels of cells) need a way to supply cells deep inside
o Surface Area to Volume Ratio – small organisms have a large SA:V ratio, but larger organisms have a smaller SA:V ratio, so diffusion alone is inadequate, the diffusion distance is too far/would take too long, to supply substances to cells, deep within the organism
o Metabolic Rate – more metabolically active organisms need more energy from respiration and so, require a constant supply of oxygen and glucose (remove waste)
Describe the features of a single circulatory system.
o Speed of blood flow to the body is reduced – due to lower pressure of blood (passes through capillaries of gills)
o Rate of oxygen and other substances being delivered to respiring cells is limited
o Blood flows once through the heart for each circuit of the body
o Present in fish, who have only two chamber in the heart
o One in which the blood flows through the heart once for each circuit of the body
Describe the features of a double circulatory system.
o Two separate circuits – blood flows through the heart twice (very efficient)
o Present in mammals, including humans
o Heart increases pressure of blood after it picks up oxygen in the lungs
o Systemic circulation (body) carries blood at a higher pressure than pulmonary circulation (lungs)
o Reduced pressure is necessary in the capillaries of lungs to avoid damage
o High blood pressure in the systemic circulation is needed to pump the blood all around the body, fast enough
Describe the features of an open circulatory system.
o Present in insects
o Blood fluid circulates through the body cavity (haemocoel) so tissues and cells are bathed directly in haemolymph (insect blood)
Haemolymph does not carry oxygen or carbon dioxide but hold food and nitrogenous waste
o A long, muscular organ, like a heart, pumps this blood fluid
o Movement, or lack of, can affect the circulation
o Blood pressure is slow and blood flow is slow
Describe the features of a closed circulatory system.
o Blood is held in blood vessels
o Present in mammals and fish
Describe the structure and function of arteries/arterioles and the distribution of different tissues within the vessel walls.
o Relatively small lumen – to maintain blood pressure
o Relatively thick wall – to withstand high pressure of the blood
o Very smooth endothelium on the inner lining – allows blood to flow freely (no friction)
o Large amount of smooth muscle in the tunica media, especially in arterioles/small arteries – contraction of muscle in the arterioles reduces the size of the lumen, diverting blood from one area to another (vasoconstriction)
o Large amount of elastic tissue/collagen in the tunica adventitia, especially in the arteries close to the heart – allows wall to stretch/recoil as high pressure blood pushes through
o Valves are not present – except in the aorta/pulmonary artery (leaving the heart)
Describe the structure and function of veins/venules and the distribution of different tissues within the vessel walls.
o Relatively large lumen – less resistance to blood flow allowing blood at low pressure to move through more easily
o Relatively thin walls
o Very smooth endothelium
o Small amount of elastic tissue/collagen/smooth muscle – low pressure and therefore, there is no need to stretch/recoil, nor divert blood
o Valves are present – prevent backflow and due to low blood pressure
Describe the structure and function of capillaries and the distribution of different tissues within the vessel walls.
o Very narrow lumen, one cell thick – short diffusion distance
o Leaky walls with small spaces between cells and very thin endothelium walls – allow blood plasma and dissolved substances to leave
o No smooth muscle/elastic tissue in wall, nor any valves present
o Form a vast network for vessels – large surface area for exchange
o Permeable to water and dissolved substances
o Gaps between endothelial cells that make up the capillary walls
o Low pressure, slow movement – time for exchange of substances
How is the dissection of a heart carried out?
- Feel the arteries (feel thicker) and veins.
- Cut along the line where the right atrium and coronary artery meet.
- Look at the atria and ventricles - the latter have thicker walls. The left ventricle will be thicker than its right counterpart because it needs to pump blood to the whole body.
How is tissue fluid made?
• Tissue fluid formed because:
o Pressure high at the arterial end ;
o Heart contractions generating hydrostatic pressure ;
o Hydrostatic pressure is greater than oncotic pressure ;
o Capillary wall, is leaky
o Water / plasma passes through & dissolved substances (e.g. glucose, amino acids) ;
o Red blood cells / plasma proteins / some WBC’s cannot get out because they are too large ;
o Net outflow / tissue fluid formed at arterial end ;
• Some fluid returns to capillary as:
o Hydrostatic pressure lower at venous end ;
As tissue fluid spreads out in the capillaries
o Ref. to increased distance from the heart ;
o Ref. to osmotic effect / oncotic pressure ;
o Oncotic pressure caused by soluble plasma proteins (high concentration in blood) which could not leave capillary;
Oncotic pressure gradient encourages movement of water back into the capillaries from the tissue fluid
o Some return of fluid at venous end ;
• Some tissue fluid enters the lymphatic system, which drains excess tissue fluid into lymph vessels and returns it to the blood in the subclavian vein
Tissue fluid
fluid that permeates the spaces between individual cells, is in osmotic contact with blood and lymph, and that serves as a transport of metabolic requirements and waste
What are the components of blood?
- Erythrocytes (too large to pass capillary walls)
- Plasma proteins (too big to leave the capillaries)
- Leukocytes – i.e. phagocytes, neutrophils, lymphocytes
- Platelets
- Hormones
- Water and dissolved solutes
- High hydrostatic pressure
- More negative oncotic pressure
- In blood vessels
- Glucose, amino acids, O2
What are the components of tissue fluid?
- No RBC (too large to pass capillary walls)
- Plasma with dissolved nutrients – i.e. glucose, oxygen
- Some leukocytes, during infection – i.e. neutrophils
- No platelets
- Very few proteins and some hormones
- Water and dissolved solutes
- Low hydrostatic pressure
- Less negative oncotic pressure
- Not in vessels
- Less glucose, amino acids, O2 than blood
What are the components of lymph?
- No RBC (too large to pass capillary walls)
- In the liver, have a particularly high concentration of proteins
- Many lymphocytes
- No platelets
- High concentration of lipids
- Few proteins – only antibodies
- Water and dissolved solutes
- Low hydrostatic pressure
- Less negative oncotic pressure
- In lymph vessels
- Less glucose, amino acids, O2 than tissue fluid
Systole
describes contracting
