SECTION B TRANSPORT SYSTEM Flashcards
What two factors affects the absorption and transport of substances?
Unicellular
Multicellular
- The surface area to volume ratio
- The limitations of simple diffusion
Unicellular organisms like amoeba are very small and have a large surface area to volume ratio. Diffusion through their body surface is adequate to take in their requirement example oxygen and remove their waste example carbon dioxide. No part of their body is far from its surface and substances can move these short distances by diffusion. They do not need a transport system to carry substances around their bodies.
Multicellular organisms have a small surface area to volume ratio. Diffusion through their body surface is not adequate to supply all their body cells with their requirements and remove their waste. Most of their body is too far from its surface for substances to move through it by diffusion. These organisms have developed transport systems to carry useful substances from specialized organs to absorb them example lungs and ileum to body cells and to carry waste substances from body cells to specialized organs that excrete them example the kidneys. Transport systems carry useful substances (oxygen, water, glucose, amino acids, vitamins, minerals, hormones, antibodies, plasma proteins and heat) in animals and manufactured food, water and mineral salts in plants. Transport systems also carry waste substances like carbon dioxide and nitrogenous waste like urea in animals.
What 3 are the circulatory system?
- Blood which serves as a medium to transport substances around the body.
- Blood vessels - tubes through which blood flows to and from all parts of the body.
- The heart pumps blood through the blood vessels.
What 3 types of cells make blood?
- rbc
- wbc
- platelets
These cells are suspended in plasma. Cells make up 45% by volume and plasma make up 55%.
What is plasma?
A yellowish fluid composed of 90% water and 10% dissolved substances which consists of products of digestion (glucose, amino acids, vitamins, minerals), wate products (carbon dioxise as the hydrogen carbonate ion HCO3- and urea), hormones (insulin, thyroxine) and plasma proteins (fibrinogen, albumen and antibodies).
Function
- Transporting products of digestion from the ileum to the liver and the body cells.
- Transporting carbon dioxide as the HCO3- ion from the body cells to the lungs.
- Transporting urea from the liver to the kidneys.
- Transporting hormones from endocrine glands to target organs.
- Transporting heat from the liver and muscles to all parts of the body.
Blood groups?
Classified based on chemical present on the surface of red blood cells known as antigens.
Two grouping systems
- The ABO system which divides blood into four groups
- group A
- group B
- group AB
- group O - The rhesus system which divides blood into two groups = rhesus positive and rhesus negative.
Blood?
The blood defends the body against diseases caused by pathogens (bacteria, viruses).
Clot formation?
When the skin is cut platelets on exposure to air release an enzyme called thromboplastin. Thromboplastin with the help of calcium ions and vitamin K in the blood starts a series of chemical reactions that change the soluble plasma protein called fibrinogen into insoluble fibrin. Fibrin forms a network of fibres across the cut that traps blood cells and form a clot. The clot prevents further blood loss and pathogens from entering.
Phagocytes?
Phagocytes continuously leave the blood by squeezing between the cells of the capillary walls into tissues where they engulf and digest pathogens especially bacteria by phagocytosis. If tissues become infected by large numbers of pathogens either in a cut or wound or inside the body the inflammatory response is triggered. Blood vessels supplying the site of infection dilate and blood flow to the area increases. The response makes the are swollen and red and brings more phagocytes to the area and increases the permeability of the capillary walls. The phagocytes easily squeeze out of the capillaries into the tissues where they engulf and digest the pathogens.
Natural immunity?
Immunity is the temporary or permanent resistance to a disease. Natural immunity results from a person having been exposed to a pathogenic disease caused by a virs or bacterium. Lymphocytes bring about this immunity by producing proteins called antibodies in response to the presence of foreign substances (antigens) in the body. Antigens include chemicals mainly proteins found in the walls or coats of pathogens or toxins produced in pathogens. Antigens are specific to the type of pathogen and are foreign to all other organisms. When a pathogen enters the body lymphocytes make specific antibodies in response to the pathogen’s specific antigen. These antibodies can cause the pathogen to clump together so that the phagocytes can engulf them or cause the pathogens to disintegrate or neutralize the toxins produced by the pathogens; antibodies that do this are called antitoxins. Production of antibodies takes time and the pathogen produces symptoms of disease before being destroyed or having its toxins neutralized. Once the person recovers the antibodies gradually disappear from the blood and some lymphocytes develop into lymphocyte memory cells that remember the specific antigen. When the pathogen enters the body again these memory lymphocytes recognize the antigen, multiply and quickly produce large quantities of the specific antibody. The pathogen is destroyed or its toxins neutralized before symptoms of the disease develop. The person has become immune to the disease. Immunity may last a short time example against the common cold to a lifetime example chicken pox is rarely caught twice. A baby gains important immunity by receiving antibodies that pass across the placenta before birth or from breast milk during breast feeding. Since the baby’s lymphocytes have not been involved in producing the antibodies and the antibodies gradually disappear from the blood, immunity lasts only a short time.
Artificial immunity?
Acquired immunity by vaccination and is used to control the spread of communicable diseases (diseases that pass from person to person). A vaccine may contain live pathogens that have been weakened (attenuated) examples measles, mumps and rubella vaccines, pathogens that have been killed examples cholera, influenza and polio vaccines, toxins from the pathogen that have been made harmless examples diphtheria and tetanus vaccines, fragments of the pathogen example influenza vaccine and the specific antigens (proteins) from the coat of the pathogen produced by genetic engineering examples hepatitis B vaccine. Vaccines do not cause the disease but lymphocytes still make antibodies in response to the specific antigens that are present in the vaccine. Lymphocyte memory cells are also produced so that an immune response is set up whenever the pathogen enters the body. Artificial immunity may last a short time example against cholera to a lifetime example against tuberculosis.
What are the 3 types of blood vessels?
arteries
capillaries
veins
Arteries carry blood away from the heart. On entering an organ an artery branches into smaller arteries called arterioles which then branch into a network of capillaries that run throughout the organ. Capillaries then join into small veins called venules which join to form a single vein that leads back from the organ towards the heart.
The heart?
The pumping action of the heart maintains a constant circulation of blood around the body. The walls of the heart are composed of cardiac muscle which has its own inherent rhythm and does not get tired. The heart is divided into four chambers. The two on the right contain deoxygenated blood and are completely separated from the two on the left which contain oxygenated blood by the septum. The top two chambers called atria have thin walls and they collect blood entering the heart. The bottom two chambers called ventricles have thick walls and they pump blood out of the heart. Valves are present between each atrium and ventricle and in the pulmonary artery and aorta as they leave the ventricles to ensure that blood flows through the heart in one direction.
Cardiac Cycle?
The atria and ventricles at the two sides of the heart contract and relax together. During one cardiac cycle or heart beat the atria and ventricles relax together (diastole), the semi-lunar valves close, the atria fill up with blood from the anterior and posterior vena cavae and pulmonary vein and the blood flows into the ventricles. The atria contract together (atrial systole) forcing any remaining blood into the ventricles. The ventricles contract together (ventricular systole), the tricuspid and bicuspid valves close and blood is forced into the pulmonary artery and aorta. The heart beats on average 75 times per minute. The rate is maintained by a group of specialized cardiac muscle cells in the right atrium called the pacemaker and can be modified by nerve impulses example the rate increases with exercise.
Circulation?
During one complete circulation around the body the blood flows through the heart twice therefore humans have double circulation. In the pulmonary circulation blood travels from the right ventricle through the pulmonary artery to the lungs to pick up oxygen and lose carbon dioxide (it becomes oxygenated). It then travels back via the pulmonary vein to the left atrium. In the systemic body circulation the blood travels from the left ventricle through the aorta to the body where it gives up oxygen to the body cells and picks up carbon dioxide (it becomes deoxygenated). It then travels back via the anterior or posterior vena cava to the right atrium. A double circulation is necessary because blood loses pressure when it passes through the lungs so it goes back to the heart to be given enough pressure to reach body organs to supply them with oxygen. As it loses pressure passing through organs the blood goes back to the heart again to be given enough pressure to reach the lungs to get rid of waste carbon dioxide and picks up more oxygen.
Transport in plants?
Substances are transported around plants by vascular tissue composed of xylem and phloem tissues. Xylem tissue composed of xylem vessels transports water and mineral salts. Phloem tissue is composed oh phloem sieve tubes and companion cells transports soluble food materials. Vascular tissue runs throughout roots, stems and leaves.
Movement of Water
Xylem vessels transport water from roots to leaves for use in photosynthesis. Xylem vessels are long, narrow and hollow tubes that are non-living and are formed from columns of elongated cells. The contents of the cells die, the cross walls between adjacent cells in each column breakdown and the cellulose walls of the vessels become thickened with lignin in rings, spirals or net-like pattern. Being long, narrow and hollow with no cross walls water can flow continuously through xylem vessels. The lignin is tough and strong so xylem vessels also help support the plant. Wood is almost entirely composed of lignified xylem vessels. Water moves through a flowering plant by a combination of root pressure, transpiration and capillarity.
Control of loss of Water by Stomata
Stomata found mainly in the lower surface of leaves control water loss from leaves. Stomata open when the guard cells are turgid which results in rapid transpiration and almost close when the guard cells are flaccid resulting in slow transpiration.
If the supply of water in the soil is low plant cells become flaccid so stomata almost close. This reduces water loss by transpiration and conserves water. A plant will wilt when it loses more water in transpiration than its roots can take up.
Movement of Organic Food
Phloem sieve tubes transport organic food mainly sucrose and some amino acids from leaves to all other parts of the plant. These are long and narrow tubes that are formed from columns of elongated cells. The cross walls between adjacent cells in each column become perforated by small holes to form sieve plates. Each cell is called a sieve tube element and it contains living cytoplasm but no nucleus. The cytoplasm of adjacent sieve tube elements is connected through the holes. Each sieve tube element has a companion cell next to it that contains a nucleus. The nucleus controls the functioning of both cells. The movement of organic food through phloem sieve tubes is called translocation.
Translocation
Mineral salts are absorbed by roots in the form of ions. The ions are dissolved in the water in the soil and are absorbed by the root hairs against a concentration gradient by active transport. The ions then move through the cortex cells and into the xylem vessels dissolved in the moving water and are carried throughout the plant dissolved in the water in the xylem vessels.
