Ch.9 Transport of substances in humans Flashcards
How does unicellular and small multicellular organisms exchange materials?
They exchange materials over their body surfaces by means of diffusion. They also rely on diffusion to distribute substances within their bodies.
Why can’t diffusion be carried out to exchange materials in large multicellular organisms?
There are specialized structures to absorb nutrients and exchange respiratory gases. These structures are some distance away from most body cells. Diffusion alone is not sufficient to move substances over long distances. Hence, a transport system is necessary to move substances within the body.
What are the two transport systems in humans?
- the circulatory system, which consists of blood, blood vessels and the heart
- the lymphatic system
How many litres of blood does a human adult have?
5 literes
What does the blood consist?
The blood consists of blood cells suspended in a liquid called plasma.
What are the three main types of blood cells?
- red blood cells
- white blood cells
- blood platelets (cell fragments)
What will happen when blood is spun at high speed in a centrifuge?
When blood is spun at high speed in a centrifuge, the blood cells go to the bottom part of the tube, and the pale yellow layer on top is plasma.
What is plasma?
Plasma is the liquid part of the blood. It is mostly water with a variety of substances dissolved in it.
What are the substances dissolved in plasma?
=plasma proteins
- fibrinogen
- antibodies (produced by =certain white blood cells)
=inorganic ions
=nutrients
=respiratory gases
- oxygen
- carbon dioxide
=urea
=hormones
What’s the importance of the plasma proteins?
- blood clotting (fibrinogen)
- body defence (antibodies)
What’s the impotance of inorganic ions dissolved in plasma?
Regulating blood pH and osmosis
What’s the importance of nutrients dissolved in plasma?
As energy sources or for the synthesis of other biomolecules.
What’s the importance of respiratory gases dissolved in plasma?
oxygen: used in respiration to release energy
carbon dioxide: a waste product of respiration
What’s the importance of urea dissolved in plasma?
A waste produc of protein metabolism
What’s the importance of hormones dissolved in plasma?
Serve as chemical passengers that regulate metabolic processes in the body.
What are the strutural features of red blood cells?
- biconcave disc shape
- red in colour due to the presence of haemoglobin
- have no nucleus
What’s the size of red blood cells?
About 8μm in diameter and 2μm in thickness
What’s the function of red blood cells?
Contain haemoglobin to carry oxygen
What’s the site of production for red blood cells?
Bone marrow
What are the number of red blood cells per mm^3?
4.2 million to 6.2 million
What’s the life span for red blood cells?
~120 days
How’s the destruction of red blood cells?
- In liver and spleen
- haemoglobin is broken down into iron (which is used to produce new red blood cells) and bile pigment (which is excreted in bile)
what’s are the structural features of white blood cells?
- irregular shape
- colourless
- have a nucleus; the shape varies in different types
What are the two main types of white blood cells?
phagocytes
lymphocytes
What sizes are the white blood cells?
Phagocytes:
10 - 20 μm in diameter
lymphocytes
6 - 10 μm in diameter
What is the function of white blood cells?
Are part of the immune system to defend the body against pathogens
(disease-causing organisms)
What’s the site of production for white blood cells?
Produced in bone marrow
(some lymphocytes mature in the bone marrow while some mature in the thymus gland)
What’s the number of white blood cells per mm3?
5000 - 11,000
How’s the destruction of white blood cells?
Some are killed by pathogens; some are egested in the faeces.
What are the structural features of blood platelets?
- very small cell fragments of irregular shape
- colourless
- have no nucleus
How big are blood platelets?
2 - 3 μm in diameter
What’s the function of blood platelets?
Play a role in blood clotting
Where are blood platelets produced?
Bone marrow.
What’s the number of blood platelets per mm3?
150,000 to 500,000
What’s the life span of blood platelets?
A few days
How’s blood platelets destructed?
In liver and spleen
______________ is the transport medium of the circulatory system.
Blood
What are the functions of the blood?
- Transport of substances
- Body defence
- Distribution of heat
What substances does the blood transport?
- oxygen
- carbon dioxide
- nutrients
- urea
- hormones
- antibodies
How is oxygen transported in the blood and used by the body?
Oxygen is transported from the lungs to body cells where it is used in respiration. Most oxygen is carried by haemoglobin in red blood cells, and some is dissolved in plasma.
How is carbon dioxide transported in the blood and used by the body?
Carbon dioxide is transported from body cells to the lungs for removal. Most carbon dioxide is transported in plasma as hydrogencarbonate ions.
How are nutrients transported in the blood?
Nutrients atr transported in plasma from the small intestine to the liver, and then to other parts of the body.
What is urea and how is urea transported in the blood?
Urea is a waste product formed from the breakdown of excess amino acids in the liver. It is transported in plasma to the kidneys, and is excreted in urine.
How are hormones transported in the blood?
Hormones are secreted by endocrine glands into the bloodstream. They are transported in plasma to their target organs to carry out their functions.
How are antibodies transported in the blood?
Antibodies produced by lymphoytes are transported in plasma for body defence.
How does blood protects the body against diseases?
- blood clotting
( blood platelets play a role in blood clotting; formation of blood clots at wounds prevents entry of pathogens and further loss of blood.) - phagocytosis
( phagocytes engulf and digest invading pathogens) - production of antibodies
( lymphocytes produce antibodies which destroy pathogens or neutralize the toxins produced by pathogens)
How does blood help with distribution of heat?
Blood absorbs heat from metabolically active organs, such as liver and muscles, and destributes it throughout the body. This helps maintain a constant body temperature.
What are the three main types of blood vessels?
Arteries
- carry blood away from the heart
Veins
- carry blood towards the heart
Capillaries
- the smallest blood vessels, connect the arteris and the veins
What is the arrange of blood vessels?
aorta (largest artery in the body) -> smaller arteries -> arterioles -> capillaries -> venules -> veins -> venae cavae (singular: vena cava)
What is the function of arteries?
To transport blood from the heart to body tissues.
Why is the pressure of the blood in arteries high?
Because of the pumping action of the heart.
The blood in the arteries is oxygenated, except for the ___________________________ ( and the umbilical artery of an unborn baby.) Most arteries are located deep in the body.
pulmonary artery
How are the arteries structurally adapted to their function in transport?
- artery have very thick walls.
-> withstand the high pressure of the blood - the walls of arteries contain large number of elastic fibre
-> allows the walls to stretch when the heart contracts to pump blood into arteries and recoil when the heart relaxes. This helps- maintain blood pressure and
- ensures a continuous blood flow.
- the walls of arteries have a thick muscle layer. These muscles can contract and relax to change the diameter of the vessels.
-> regulate the blood flow to certain organs or tissues
What’s the function of veins?
To transport blood back to the heart.
Why is the blood pressure in veins much lower than that in arteries?
The blood pressure in veins is much lower than that in arteries because the blood has passed through the arterioles, capillaries and venules.
The blood in most veins is deoxygenated, except for the ______________________ ( and the umbilical vein). Veins are located closer to the body surface when compared to arteries.
pulmonary vein
How are veins structurally adapted to their function in transport?
- the walls of veins are thinner, less muscular and contain fewer elastic fibres than those of arteries
- veins have a larger lumen than arteries. The large lumen reduces resistance so that blood can continue to flow in the veins at low pressure.
- valves are present to preven tthe backflow of blood. This helps ensure that blood flows in one direction only
What is the blood flow in the veins aided by?
The contraction of skeletal muscles adjacent to the veins.
When these skeletal muscles contract, the veins are squeezed and the blood inside is forced toward the heart.
What are capillaries?
Capillaries are the smallest of all blood vessels in the body. They receive blood from arterioles and form networks called capillary beds, which are found in almost all tissues of the body. They are the site for the exchange of materials between the blood and body cells.
How are capillaries structurally adapted to their function?
- The walls of capillaries are differentially permeable
-> some substances are small enough to pass through them.
(red blood cells and plasma proteins are too large to pass through) - their walls are one-cell thick.
-> This provides a short diffusion distance for the exchange of materials. - the highly branched networks of capillaries provide a large surface area for the rapid exchange of materials. In most tissues, the capillary network is so dense that each cell of the tissue is in close contact with a capillary.
-> This also reduces the diffusion distance. - the lumen is so small that red blood cells must squeeze through. This brings them in close contact with the capillary walls,
-> reducing the distance for oxygen to diffuse from red blood cells to the body tissues. - blood flows slowly in capillary beds because they have a very large cross-sectional area.
-> this allows more time for the exchange of materials
Where is the heart located?
It lies in the thoracic cavity between the lungs, protected by the rib cage. Surrounding the heart is a touch protective sac called the pericardium.
What muscle is the heart made up of?
Cardiac muscle
What’s so special about cardiac muscle?
It can contract rhythmically without fatigue.
How does the cardiac muscle function?
The cardiac muscle receives oxygen and nutrients from the coronary arteries, which branch off from the aorta. Carbon dioxide and other metabolic wastes are carried away through the coronary veins. oth coronary arteries and coronary veins run along the surface of the heart.
What’s the purpose of septum?
Prevents mixing of oxygenated and deoxygenated blood.
How does the right atrium function?
The right atrium receives deoxygenated blood from all parts of the body (except the lungs) through the venae cavae. The superior vena cava brings blood from the upperparts of the body, while the inferior vena cava brings blood from the lowers parts of the body. The right atrium then pumps the blood into the right ventricle.
How does the left atrium function?
The left atrium receives oxygenated blood from the lungs through pulmonary veins. It then pumps the blood into the left ventricle.
Why are the walls of ventricles thicker than the atria?
The walls of the ventricles are thicker than the atria since the ventricles allows it to pump blood out of the heart at a higher pressure.
How does the right ventricle function?
The right ventricle receives deoxygenated blood from the right atrium. It pumps blood to the lungs through the pulmonary arteries.
How does the left ventricle function?
The left ventricle receives oxygenated blood from the left atrium. It pumps the blood to all parts of the body (except the lungs) through the aorta.
Why does the left ventricle has a thicker and move muscular wall than the right ventricle?
It is because the left ventricle allows it to generate a greater force to pump blood throughout the body.
What’s the purpose of the heart valves?
The presence of valves in the heart prevents the backflow of blood. This ensures blood flows through the heart in one direction only.
How does the bicuspid and tricuspid valves function?
The bicuspid and tricuspid valves are closed by the high pressure of blood in each ventricle when the ventricles contract. This prevents the backflow of blood into the atria.
What’s the purpose of heart tendons?
The two heart valves are attached to the inner walls of the ventricles by heart tendons. These tough cord-like tendons prevent the valves from turning inside out (into the atria) when the ventricles contract.
What’s the function of semilunar valves?
Semilunar valves are pocket-shaped structures found at the base of the aorta and the pulmonary artery. When the ventricles relax, these valves close to prevent the backflow of blood into the ventricles.
The right side of the heart pumps blood to the lungs, and he blood returns to the heart through the _____________________________.
pulmonary circulation
The left side of the heart pumps blood to all parts of the body (except the lungs), and the blood returns to the heart through ___________________________-.
systemic circulation
Since the blood flows through the heart twice to circulate the whole body, this type of blood circulation is called _____________________________-.
double circulation
Describe the process of pulmonary circulation.
- the right atrium contracts to pump deoxygenated blood into the right ventricle
- the right ventricle contracts to pump the the blood into the pulmonary arteries, which carry blood to the lungs
- when the blood reaches the lungs, gas exchange takes place – oxygen diffuses into the blood, while carbon dioxide diffuses out. The blood becomes oxygenated.
- the oxygenated blood flows to the left atrium of the heart through the pulmonary veins
Describe the process of systemic circulation.
- the left atrium contracts to pump the oxygenated blood into the left ventricle.
- the left ventricle contracts to pump blood into the aorta. The blood then flows through the arteries to all parts of the body (except the lungs).
- when the blood reaches the capillary beds of the tissues or organs, exchange of materials takes place – oxygen and nutrients diffuse from the blood to body cells, while carbon dioxide and other metabolic wastes diffuse in the opposite direction. The blood becomes deoxygenated.
- the deoxygenated blood flows through the venules, the veins, the venae cavae, and finally to the right atrium of the heart.
What are the advantages of a double circulation?
- the pulmonary circulation is seperated from the systemic circulation so that only oxygenated blood is carried to body tissues
- blood pressure in the mulmonary circulation and the systemic circulation are different. Strong contraction of the left ventricle creates high blood pressure to move blood quickly through the systemic circulation to all parts of the body, while a weaker contraction of the right ventricle protects the delicate capillaries in the lungs from damage by high pressure.
What is tissue fluid?
Water liquid that fills the small spaces in between body cells. It provides a relatively stable environment for the cells, and serves as the medium across which exchange of materials between the blood and body cells takes place.
How is tissue fluid formed?
Tissue fluid is formed from blood in a capillary bd. At the arterial end of the capillary bed, the hydrostatic pressure of the blood is higher than the tissue fluid. Some components of the plasma are forced out through the differentially permeable capillary walls to become tissue fluid.
Does tissue fluid contain plasma proteins?
No. Tissue fluid has a composition similar to that of plasma, but it has no plasma proteins, as these molecules are too large to pass through the walls of capillaries. Red blood cells and blood platelets also remain in the blood due to their large sizes. However, some types of white blood cells (e.g. phagocytes) can squeeze through the capillary walls and enter the tissue fluid.
How are materials exchanged between the blood and body cells?
Body cells constantly take up oxygen and nutrients from the surrounding tissue fluid for respiration and other metabolic processes. This creates concentration gradeitns for oxygen and nutrients between the tissue fluid and the blood in the nearby capillaires. Hence, these substances will diffuse from blood into tissue fluid.
Body cells produce carbon dioxide and other metabolic wastes. These wastes diffuse into the surrounding tissue fluid, and then into the blood inside the capillaires.
How does tissue fluid return to the blood?
At the venous end of the capillary bed, due to the retention of plasmsa proteins in blood and a low hydrostatic pressue of the blood, the tissue fluid has a higher water poential than that of the blood. Hence, water is drawn from the tissue fluid into the capillaries by osmosis.
About 90% of the tissue fluid returns to the blood at the venous end. The remining 10% drains into lymph capillaries, which are part of the lymphatic system.
What are the components of the lymphatic system?
It consists of a fluid called lymph, a network of lymph vessels, lymph nodes and various organs.
Lymph has almost the same composition as the tissue fluid. Lymph is also similar to blood. Except it has….?
- no red blood cells, blood platelets or plasma proteins
- less oygen and nutrients as these substances have been absorbed by body cells
- more carbon dioxide and wastes that have been released from the body cells
- more lipids and fat soluble vitamins that have been absorbed from the small intestine
What are lymph capillaires?
Lymph capillaries are tiny, blind-ended vessels which are found in almost all tissues of the body. The walls of lymph capillaries are thin, composed of only a single layer of cell.s Tissue fluid can pass through the spaces between these cells into the lymph capillaries.
How does lymph vessels function?
The lymph capillaries from different body parts join to form lymph vessels, which is then joined to form larger vessels. These lymph vessels join two large veins at the base of the neck, where the lymph returns to the circulatory system.
The lymph flows slowly in the lymph vessels, driven by the contraction of skeletal muscles adjacent to the lymph vessels. When the skeletal muscles contract, they press against the lymph vessels, pushing the lymph along. There are valves in the lymph vessels like those in the veins. They prevent the backflow of lymph and ensure that the lymph flows only towards the heart.
What are lymph nodes?
At intervals along the lymph vessels are small swellings called lymph nodes. White blood cells are stored in the lymph nodes. When lymph flows through the lymph nodes, the pathogens in the lymph will be destroyed by the white blood cells. In this way, lymph is filtered by the lymph nodes before returning to the blood stream.
What are the functions of the lymphatic system?
- the lymph vessels collect excess tissue fluid, and return it to the blood circulation
- in the small intestine, lipids and fat-soluble vitamins are absorbed by lacteals (lymph capillaires) in the villi. These food substances are transported by lymph to the blood circulation.
- it plays an important role in body defence. For example, the lymph nodes act as filters to remove pathogens before lymph returns to the blood circulation.
