Formed Elements

Revision - list out formed elements

• erythrocytes

• leukocytes

• thrombocytes

make up 45% of blood

Main features of Erythrocytes

• biconcave shape - allows for a larger surface area to volume ratio, better diffusion

• no nucleus/mitochondria → more space for Hb

• cannot respire aerobically → prevent it from consuming all oxygen

• spectrin and actin give durability to the cell allowing it to squeeze and fold passing through capillaries

• thin

• glycoproteins and lipids determine persons blood type

How is erythrocyte production controlled

• when o2 is low kidneys and liver release erythropoietin

  • stimulates production of rbc in bone marrow

• when there is enough rbc it inhibits erythropoietin

  negative feedback mechanism

Describe the life cycle of an erythrocyte

• lasts 120 days → cell membrane becomes fragile

• haemolysis → cell breaks open and hb is released leaving plasma membrane to be digested by macrophages

• hb is broken down into haeme and globulin

  • haeme: iron is extracted and stored as ferretin

  • ferretin is then converted into bilirubin and biliverdin and excreted w bile

  • globulin is broken down into amino acids

Function of erythrocytes

1. transport o2 to tissues: o2 binds at lungs oxyhaemoglobin unbind at tissues deoxyhaemolgobin.

2. Transport Co2 to lungs:

   • dissolved in solution

   • bound to hb

   • turned into carbonic acid

Leukocytes

• larger then erythrocytes

• multiply during infection

• can move out of capillaries by a crawling ameboid movement

• most common type is neutrophils then lymphocytes

• agranulocytes

• granulocytes

granulocytes

• neutrophils

• basophils

• eosinophils

agranulocytes

• monocytes

• lymphocytes

Neutrophils

• aka phagocytes

• multilobed nucleus

• engulf bacteria

Basophils

• pale bilobed nucleus

• secrete histamine which increase tissue blood flow - dilates blood vessels

• try to kill what is irritating you - good immune response but only for a short period of time

• secrete heparin to get more blood to the affected area - more motility of wbc’s

eosinophils

• stain red by eosin

• prominent bilobed nucleus

• chemicals which disable parasite

• have anti-histamine properties destroy inflammatory chemicals

Lymphocytes

• in lymph and body tissues, not in blood

• large central nucleus

• b lymphocytes

  • originate and mature in the bone marrow

  • humoral immunity meaning they secrete antibodies

• t lymphocytes

  • originate in bone marrow, mature in thymus gland

  • responsible for killing cancer cells

  • activation of phagocytes and antigen specific t lymphocytes

  • co-ordinate other immune cell actions

Monocytes

• bean shaped nucleus

• largest of formed elements

• act as macrophages to digest the pathogens and dead nuetrophils

Thrombocytes

• lack nuclei

• fragments of bone marrow

• irregular in shape

• membrane bound

Function of Thrombocytes

• endothelial damage

• thrombocytes come into contact with exposed collagen

• become activated (change their shape from round to spiney)

• stick to cells and each other forming a plug

• liver releases prothrombin → thrombin (enzyme)

• thrombin converts fibrinogen into fibrin which forms a net trapping platelets and rbc forming a clot