Ugrás a tartalomhoz Lépj a menübe
 


04 A vér és a keringési rendszer

2014.04.09

 

Circulatory system
 
Problem of size
          Amoeba: can get oxygen by diffusion (large surface area compared to its volume)
          Flatworm: flat body, easy diffusion for oxygen, but not always for food!
          Larger animals: need circulatory system!
 
Blood
It carries:
          Respiratory gases
          Decomposition products
          Other substances (e. g. hormones)
          Total volume: 5-5.5 l
Components:
          Blood plasma (55%)
          Blood cells (45%)
Blood plasma
          Water (90%)
          Salts
          Glucose (2%) 5.5 mmol/l
          Proteins: albumin (regulates the osmotic pressure), globulins (immune proteins, blood group proteins), fibrinogen (blood clotting)
Red blood cells
          Number: 5 million/mm3
          Shape: biconcave disc (doughnuts)
          Carrying of O2, CO2
          No nucleus (more room for O2)
          Producing: red bone marrow
          Life time: 120 days
          Decomposition: spleen and liver
Platelets
Small cells without nucleus
They can stick to rough surfaces (endothel)
They start the blood clotting
          Blood clot: fibrin fibres (form a mesh), + red blood cells, platelets (trapped)
          It blocks the cut
White blood cells
They protect the body from disease-causing organisms
They have nucleus
Move with pseudopodia (like amoeba)
Main types:
          Lymphocytes (nyiroksejtek): antibody production
          Neutrophiles (falósejtek): phagocytic cells
 
Blood problems
Haemophilia (bleeding): blood does not coagulate
Anaemia: red blood cells can not carry enough oxygen (not enough red blood cell, haemoglobin)
          Sickle cell anaemia: point mutation (haemoglobin structure changes)
          Leukaemia: „blood cancer” (number of white blood cells increases, bone marrow transplantation can help)
 
Blood vessels
Arteries
          Lead blood from the heart to the tissues
          Thick muscle layer
          Strong elastic wall
          Blood pressure is high in them
Capillaries
          In tissues
          Squamous inner lining (thin)
          Muscles only in special places (capillar sources)
          Change of substances across the wall by diffusion
Veins:
          Lead blood from tissues to the heart
          Thin muscle layer
          Enlargeable
          Low blood pressure
          Valves
 
Heart
Right and left atrium
Right and left ventricle
Valves: prevent blood flowing back
          Tricuspidal and bicuspidal valve: between atrium and ventricle
          Semilunar valves: in pulmonary artery and aorta
Control of the heartbeat
Heartbeat is automatic
Sino-atrial node: gives electrical impulses („pacemaker”)
Atrio-ventricular node, bundle of His, Purkinje-fibres: impulse spreads out - Heart muscle contract (without brain command)
Heart in action
          The atria contract and relax
          Diastole: relaxing period of the chambers, blood flows in
          Systole: heart muscles contract
          First the atria contract: blood flows into the ventricles
          After it ventricles contract: blood flows into the arteries
          Valves: prevent flowing back
The heart’s blood supply and problems
Coronary vessels: supply the heart muscles with oxygen and glucose
Coronary heart attack: coronary artery is blocked, it can not carry oxygen to the muscles
Embolism, thrombosis: any solid particle (cholesterol, blood clot) blocks the vessel
Angina:
          Coronary artery is partly blocked: causes chest pain when the heart works harder (physical activity, stress). It is a warning!
Heart attack:
          Total blockage of the coronary artery
          Causes severe pain in the chest
          Affected muscle is damaged
          Cardiac arrest: heart stops suddenly (you have a few minutes to restart!)
          Double circulation
          Left side: oxygenated blood to the body
          Right side: deoxygenated blood to the lungs
 
Double circulation
Small/pulmonary circuit:
          Right ventricle
          Pulmonary artery
          Lungs (gas exchange in capillaries)
          Pulmonary vein
          Left atrium
Large/body circuit
          Left ventricle
          Aorta and arteries
          Body (gas exchange in capillaries)
          Vena cava
          Right atrium
 
Problems of the circulatory system
          High blood pressure (normal: 120/80 Hgmm)
          Low blood pressure
          Shock: circulatory system collapses (Danger!)
          Varicose veis: vein is enlarged, valve can not stop flowing back of the blood
          Thrombosis: A clot closes the vessel
          Arteriosclerosis (érelmeszesedés): deposit narrows the blood vessel
 
Tissue fluid
Formation of tissue fluid: some of the plasma passes out into tissues (reason: relatively high blood pressure in capillaries)
Tissue fluid: blood plasma without proteins
At the end of capillary network: blood pressure decreases, 90% of tissue fluid goes back to the capillaries
 
Lymph System
Gathers the tissue fluid ---- lymph (in lymph system)
          Capillaries (valves)
          Lymph vessels (similar to veins)
          Lymph nodes (role in immunity)
          Thoracic duct
          Lymphoid organs: tonsils, thymus gland, spleen, appendix
 
Immunity
Natural:
          Passive („anyai”): embryo and baby get all antibodies from mother’s body across placenta and breast milk
          Active („szerzett”): infection stimulates our immune system
Artifical:
          Active: injection of killed infectious agents
          Passive: injection of pre-formed antibodies as a serum
          Immune Response
          Antigen: substance that can produce immune response (proteins on a cell or virus)
          Antibody: is produced by the immune system, reacts with the antigen and makes it harmless (immunoglobulins)
Cell-regulated Immunity
T-lymphocytes and macrophages (white blood cells)
They are developed in red bone marrow, but they are activated in thymus gland
Destroy the antigen by attaching to them
Memory cells: multiply very fast in case of new invasion (immune system can react immediately)
Antibody-regulated immunity
B-lymphocytes: developed in red bone marrow, but activated in lymphoid organs and lymph glands near the gut
They produce antibodies (immunoglobulins), which destroy antigens
AB0 blood groups
Antigens on the membrane of the blood cell
Antibodies in the blood plasma
Agglutination: antibodies eliminate the foreign antigens
Blood transfusion: recipient needs red blood cells, so donor’s red blood cells must survive.
RH blood groups
RH factor (was discovered in Rhesus monkeys): an antigen on the red blood cell membrane (85% of the population has got it)
RH+: RH antigen exists
RH-: RH antigen is absent
If an RH- pregnant bears an RH+ child: during birth immune response occurs, next RH+ foetus vill be killed
 
Health of immunity
Allergy: immune system overreacts harmless substances
Consequences:
          Hay-fever
          Asthma
          Anaphylactic shock: oversensitivity, circulatory system can be collapsed (mortal danger!)
Acquired immune deficiency syndrome (AIDS):
          Is caused by the human immunodeficiency virus (HIV)
          Virus is transmitted by blood, semen, vaginal secretions
          Transmission factors: sexual contact, infected blood or needles
          T-lymphocites are blocked
          Patient dies in pneumonia, cancer or other diseases