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L2 – Physiology of Blood

BloodDrip

Introduction

  • Blood is a reddish fluid that circulates continuously inside the CVS. by the pumping action of the heart
  • It has many important functions which are essential for life.
  • Sudden loss of more than 30% of the total volume leads to death.

Functions of the blood

1-Transport function:

  • O2 & CO2
  • Nutrients from digestive system to cells.
  • Removal of waste products.
  • Hormones from endocrine glands to cells.
  • Enzymes and vitamins.

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2-Regulatory functions:

  • PH of the blood: it contains buffer system.
  • Body temperature: through heat loss from skin.
  • Regulation of ABP: due to its viscosity

3-Protective function:

  • Gamma globulin which form antibodies for immunity.
  • White blood cell (WBC) phagocytosed microorganism.
  • Clotting factors prevent blood loss.

Composition of blood

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1.Cellular elements: represents about 45% of the total blood volume.

2.Plasma 55%.

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1) PLASMA

  • —Water 90% —
  • Organic substance 9%

-Plasma proteins 7% (albumin, globulin, firinogen)

-Other organic substance 2%

(metabolic products urea creatinine, nutritive substance like Glucose & Amino Acids, Enzymes, hormones,vitamines)    —

  • Inorganic substance 1%

– Na, K, Ca, Cl

-Respiratory gases O2, CO2

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Plasma Protein Functions

  1. Blood coagulation:  fibrinogen & prothrombin.
  2. Blood viscosity: 2 times more than water & maintain diastolic bl. Pressure.
  3. Production of an effective osmotic pressure maintaining body fluid.
  4. Buffering action.
  5. Defense action. Antibodies are gamma globulins
  6. Carrier functions: vitamins, Iron, copper, cholesterol, phospholipids, hormones e.g. Thyroxin, cortisol.
  7. Carriage of CO2.
  8. Regulation of capillary permeability.
  9. Protein metabolism.

2)Cellular Elements

1)RBCs:

  • 5 million/mm3.
  • decrease in No. causes anemia
  • increase causes polythycemia.

2)WBCs:

  • 4000-11000/mm3
  • decrease No. = leukopenia
  • increase No. = leukocytosis.

3)Platelets: (Thrombocytes):

  • 150-400 thousands/mm3 ↓
  • decrease no = Thrombocytopenia
  • increase no = Thrombvocytosis.

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Picture2Blood Cell Development

Red Blood Corpuscle (R.B.C)

-Shape: small circular biconcave disc.

-Diameter: 7.5 micron

-Number:

  • male 5- 5.5 million/mm3
  • female 4.5- 5 million/mm3

-Hb content:

  • male 14-18 gm%
  • female 12-16 gm%
  • newborn 18 gm%
  • children 12 gm%

Picture7Function of RBCs

A-Functions of the membrane:

1-Has large surface area in relation to quantity inside it.

  • Facilitates gas exchange
  • Allow passage through narrow capillaries.
  • In case of hydration the red cell can swell and become more spherical but don’t rupture.

2- Contains different channels for passage of ions to maintain normal ionic composition.

3- Contains protein antigen which are responsible for the specific blood group of the person.

4- Keep the Hb and carbonic anhydrase inside the red cell. If these substances are set free in plasma it will be:

-lost in urine

-ppt in kidney as acid haematin leading to renal failure.

B-Functions of the content

-Hemoglobin (Hb):

  • Carrier of O2 & CO2.
  • Blood viscosity.
  • Acid base balance

White Blood Cells ( W.B.C)

-Number : 4000-11000/mm3.

-Types:

1-Granular:

  • Neutrophils 60%
  • Eosinophil 1-5%
  • Basophil 0.5-1%

2-Non granular:

  • Monocyte 3-8%
  • lymphocyte 20%

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Functions of W.B.C  (Defense mechanism):

  • Neutrophil: phagocytosis.
  • Eosinophil:
  1. defense against parasite.
  2. modulate allergic reaction.
  • Basophil: synthesize and liberates heparin into blood.
  • Lymphocytes: T and B (immunity)

PLATELETS

-Has a role in haemostasis:

  • Release of serotonin which produce vasoconstriction.
  • Formation of platelet plug.

-Plug formation

  1. Platelet adhesion: to the injured area, enhanced by collagen & VonWillebrand factor
  2. Platelet activation: swelling- pseudopodia- stickiness
  3. Platelet disintegration: release of ADP & ThromboxanA2 whish attract more platelets
  4. Platelet aggregation: the process is repeated until a plug is formed.

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