Biology - Transport in Humans Flashcards
What are the functions of blood?
- Transport oxygen and other nutrients around
the body - Protective function against disease-causing
organisms - Distribution of heat in the body
What are the components of blood?
Plasma (55%), red blood cells (erythrocyte), white blood cells (leucocyte), platelets
What is plasma and its functions?
- yellowish liquid
- contains mainly water and substances such as glucose,
salts, proteins, amino acids, fats, vitamins, hormones and urea - contains red and white blood cells
- carries blood cells and nutrients (from small intestines) to rest of body, as well as excretory products (from organs) and hormones (from endocrine glands)
What are red blood cells and their functions?
- circular, biconcave in shape; no nucleus; containing hemoglobin; flexible
- transport oxygen from lungs to rest of body
- biconcave shape increases SA:V –> increases rate of absorption and release of oxygen
- no nucleus –> more space for storage of hemoglobin (combines reversibly with oxygen)
- 90-120 days lifespan
- destroyed in spleen –> Hemoglobin released, brought to the liver and broken down
What are white blood cells and their functions?
- irregular in shape, contains a nucleus
- can change its shape and squeeze into thin blood capillaries
- produced in bone marrow, lifespan of a few days
- two main types: lymphocytes and phagocytes
What are lymphocytes and their functions?
- rounded, large round nucleus, small amount of non-granular cytoplasm
- produce antibodies that recognise and destroy foreign particles and disease-causing bacteria and viruses
- clumps together bacteria for phagocytosis and neutralises the toxins produced by them
What are phagocytes and their functions?
- lobed nucleus and granular cytoplasm
- performs phagocytosis where it engulfs (ingests and digests) and destroys foreign particles such as bacteria
What are platelets and their functions?
- not true cells, just fragments of them
- produced in the bone marrow.
- lifespan of about 6 days.
- blood clotting mechanism; converts fibrinogen to fibrin threads which entangle with red blood cells to form blood clot that seals wound
What are the parts of the circulatory system?
heart, blood vessels, arteries, arterioles, blood capillaries, venules, veins
What are arteries and their characteristics?
- carry oxygenated (except pulmonary artery) blood away from heart at high pressure
- wall has a thick layer of smooth muscle, muscle contractions to maintain blood pressure
- wall has a thick layer of connective tissue (collagen and elastic fibers) to prevent bursting
- wall has large amount of elastic fibers, blood flow is not continuous, occurs in pulses with the contractions of the heart
- elastic fibers allow the artery to stretch (for large amounts of blood), provides elastic recoil helping to push the blood
- elastic layer is thicker nearer the heart
What are capillaries and their characteristics?
Arteries (branch into) –> arterioles –> capillaries found between cells of almost all tissues
- only region where the exchange of materials occurs between blood and the tissue fluid surrounding the cells
- single layer of flattened cells as wall (endothelium) with numerous pores for quick diffusion between lumen and surrounding tissue fluid
- blood cells, most plasma proteins are too large –> remain in capillary
- capillary network of numerous branches for larger surface area, which lowers blood pressure
- slower blood flow for more time for exchange of materials
Capillaries (merge to) –> venules –> veins
What are veins and their characteristics?
- carry deoxygenated (except pulmonary veins) blood at low pressure towards the heart
- wall has thin layer of smooth muscle, few elastic fibers, thinness allows vessel to be squeezed during muscle contraction
- many veins situated between large skeletal muscles
- lumen is much wider relative to the overall diameter of the vein, accommodate large volume
- valves present to prevent backflow, folds of the inner walls, shaped like half-moons, called semi-lunar valves
- wider lumen compared to overall diameter
What are the types of circulation?
double circulation: blood passes through the heart twice in every cycle of flow through the body in mammals and consists of:
pulmonary circulation:
- flow of blood between heart and lungs
- pulmonary arteries carry deoxygenated blood from heart to lungs
- pulmonary veins return oxygenated blood to heart
systemic circulation:
- flow between the heart and other parts of body
- oxygenated blood transported by arteries from left side of heart to rest of body (except lungs)
- veins carry blood from body back to right side of heart
What are the parts of the heart?
4 chambers - Right and left atria, right and left ventricle
- Pulmonary artery
- Pulmonary veins
- Aortic valve
- Bicuspid valve
- Septum
- Superior vena cava
- Pulmonary valve
- Tricuspid valve
- Inferior vena cava
What is the structure of the atria?
- Two upper chambers
- Thinner walls than ventricles since they only force blood into the ventricles –> does not require high pressure
