21 - Blood – physiology and functions. Composition and volume of the circulation blood – regulation. Plasma – composition and regulation. Haematocrit. Blood reservoirs

sections

function of blood

blood volume

blood resevoirs

what is hematocrit

cause for low haematocrit

cause of high haematocrit

blood regulation

plasm

important proteins in plasms

function of blood

1. regulates body temp

2. protection- has leuckocytes, platelets for clots- prevent blood loss

3. used for internal organs

4. transport O2 with haemoglobin and nutrients are transported in blood, remove waste CO2----remove waste

5. nutritive- carries glucose, electrolytes, vitamins, amino acids regulation of

6. homeostasis of ions and water

blood volume

blood volume is determined by the amount of water and sodium ingested

Blood contains intracellular and extracellular fluid.

• 45% erythrocytes 55% is plasma

• 6-8% volume in the body

• 5-6L in body

blood resevoirs

• spleen

• liver

• skin- veins in adipose tissue under the skin

• vein- biggest blood reservoir

• the heart and the lungs are not part of the reservoir system, but can be considered blood reservoirs.

do men or women have more RBC

Males have more RBC because they have more testosterone- increases erythropoiesis

what is hematocrit

• relationship between volume of erythrocytes and total volume of blood

  • measures the fraction of the blood that is made up of RBCs.

  • Males- 0.4-0.5

  • F- 0.35-0.45

  • Normal results for children vary, but in general are:

    • Newborn: 45 to 61%

    • • Infant: 32 to 42%

cause for low haematocrit (low RBC count)

• Haemorrhage

• Dehydration

• diarrhea/vomiting

• Tumor in the hypothalamus

• ADH - Alcohol inhibits ADH production

• coffee, tea increase urine output

cause of high haematocrit (high RBC count)

• Abnormal increase in red blood cells

• Low blood oxygen levels (hypoxia)

• Scarring or thickening of the lungs

• Bone marrow disease that causes abnormal increase in RBCs

blood regulation

• The body releases hormones to correct the blood volume:

  • ADH (antidiuretic hormone): Increases water reabsorption in kidneys.

  • Aldosterone: Increases sodium (and water) retention.

  • ANP (atrial natriuretic peptide): Promotes salt and water excretion when blood volume is too high.

• Kidney Response:
  Kidneys adjust the amount of water and salts reabsorbed or excreted in urine. This helps either conserve or eliminate fluids.

• Thirst Mechanism:
  When blood volume is low, the brain triggers thirst so you drink more water to restore volume.

• Vasoconstriction or Vasodilation:
  Blood vessels can narrow (vasoconstriction) to maintain pressure if blood volume is low, or widen (vasodilation) if volume is high.

plasma

• Plasma is the largest component of blood, making up 55%.

• High percentage of water

• transport medium for blood cells, dissolved nutrients, plasma proteins, etc.

• Removes waste from the body.

• maintain blood pressure

• regulates body temperature.

important proteins in plasms

• Albumin-60%

• clotting (coagulation) factors

• immunoglobulins

• fibrinogen

• prothrombin