The circulatory system - Blood

Bill Nye  J-5do9M J-5do9M

Blood  An average human adult has about 5L of blood moving through their circulatory system.  Blood can be called a connective tissue because it links al the cells and organs in the body.  Blood consists of a fluid part and a solid part.  Fluid portion is called plasma and consists of water plus dissolved gases, proteins, sugars, vitamins, minerals and waste products.

Blood  The solid (or formed) portion is made up of red blood cells, white blood cells, and platelets.  The cells and platelets are made in the bone marrow inside the bones.  Formed portion = 44% red blood cells 1% white blood cells and platelets.  Plasma = 55%

Plasma and its function  Clear yellowish fluid composed of  About 92% water  7% dissolved blood proteins  1% other organic substances and inorganic ions (sodium, potassium, chloride, and bicarbonate)  Maintains fluid balance in cells and in spaces between cells  Helps maintain slightly alkaline pH  Helps with blood clotting and in nerve and muscle function.

Red Blood Cells and Their Functions  Another name for them is: erythrocytes  Make up about 44% of the total volume of blood.  Specialized for oxygen transport.  Oxygen-carrying capacity of blood is dependent on number of RBC preset and the amount of hemoglobin that each cell contains.  Disk shaped with no nucleus and packed with about 280 million hemoglobin proteins.

White Blood Cells and Their Function  Also called Leukocytes  Part of the body’s response to infection  Makes up about 1% of the total blood volume, but this can more than double when the body is fighting infection.  Colorless and have a nucleus

Types of White Blood Cells  Phagocytes – Engulf and destroy pathogens  Neutrophils – Most abundant and found in tissues and blood.  Eosinophils – Found in mucous lining of digestive and respiratory tracts.

Types of White Blood Cells  Basophils – Assist immunity by secreting substances that attract phagocytes to destroy pathogens  Lymphocytes – Produce antibodies that incapacitate pathogens allowing them to be easily destroyed.  Monocytes – Become macrophages which destroy bacteria.

Platelets and Their Functions  Membrane-bound fragments of cells that form when larger cells in the bone marrow break apart.  Do not contain nuclei and break down within 7-10 days.  Play a key role in blood clotting.

Blood Clotting Process  When a blood vessel is broken due to injury, it releases chemicals that attract platelets.  Platelets rupture releasing chemicals that combine with other chemicals in plasma to produce enzyme thromboplastin.  Thromboplastin reacts with prothombin (protein from liver) to produce enzyme thrombin. (in presence of calcium ions).  Thrombin reacts with fibrinogen (plasma protein) to produce fibrin.  Fibrin is an insoluble protein that forms fibrous mesh over the site of injury. Mesh prevents loss of blood cells and eventually solidifies to form a clot.  3:40

Functions of blood  1. Transport  2. Temperature Regulation

1. Transport  Blood absorbs nutrients in the digestive system.  Blood transports and removes waste products of cellular processes.  Blood carries excess amounts of mineral ions and other waste products to the kidneys for processing and excretion.

2. Temperature Regulating  Balancing of heat from the body with the production of heat by metabolic processes.  Mammals can control heat loss by changing amount of blood flowing near the body surface.  Vessels in the skin can expand to carry more blood or constrict to carry less.

2. Temperature Regulating  Vasodilation – When core of body becomes hot, vessels will widen increasing blood flow.  Vasoconstriction – When body needs to conserve heat, blood vessels will constrict reducing blood near the surface.  These processes may be triggered by change in blood pressure or increased metabolic activity, or in response to substances (alcohol causes vasodilation)

Monitoring the Human Circulatory System

Heartbeat  The normal heart sound is a repeated double beat often described as ‘lub-DUB’  The first sound is made as the atrioventrical valves close and blood is pumped from the atria to the ventricles.  The second sound is made when the semi-lunar valves close wen blood is pumped from the ventricles to the arteries.

Heartbeat  Variations in the heartbeat indicate possible problems.  Heart murmurs are produced when blood doesn’t flow smoothly in the heart because a valve or artery narrows or closes creating a backflow of blood.

Blood Pressure  The pressure exerted against the vessel walls when blood passes through the vessel.  Blood pressure is related to the heartbeat. When ventricles contract and force blood into the pulmonary arteries and aorta, pressure increases in those vessels and then reduces after the blood passes..

Blood Pressure  Systolic Pressure – The maximum pressure during ventricular contraction.  Diastolic Pressure – The lowest pressure before the ventricles contract.  Blood Pressure Measure – Systolic over diastolic. Average BP of healthy young person is below 120/80

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Homework  # 4,12,14 page 488  #6,7,9, 14 page 493