Functions & Composition of Blood

What are the functions of blood?

1. Transport
• O2 and CO2
• Hormones
• Nutrients & waste

2. Maintenance of homeostasis
• Transport of hormones
• Heat regulation- thermoregulation
• Regulation of pH

3. Immunity
• White blood cells
• Antibodies & other mediators

4. Haemostasis
• Blood clotting processes in balance with prevention of blood clotting

What % of body weight does blood constitute?

8%- male (5-6) >female (4-5L)

What is the pH of blood?

7.35-7.45

Osmolarity

measure of total concentration of solute particles

What is the Osmolarity of blood?

285-295 mOsm/L

Viscosity

resistance to flow

Viscosity of blood relative to water

3.5-5.5x thicker than water

Why is blood viscous?

To allow it time to carry out all of its functions

Density/specific gravity of blood

1.05g/ml

What is blood composed of?

•Formed elements
•Plasma constitutes
- White blood cells (leukocytes)
- Red blood cells (erythrocytes)
- platelets

What % do the formed elements make up of the total blood volume?

45%

What % of blood is plasma?

55%

By what mechanism is blood separated in blood samples?

Centrifugation

Centrifugation

Separates components by density using high speed spinning

What is the name for the containers that blood is collected in for Centrifugation?

Vaccutainers

What do vaccutainers contain?

anticoagulant

What is an anticoagulant?

a substance that inhibits blood clotting

Give examples of anticoagulants

EDTA, citrate or heparin

What is the buffy coat?

white blood cells and platelets

What is another name for white blood cells?

leukocytes

Where is the buffy coat located?

It sits above the packed RBC's in centrifuged blood

What is the haematocrit?

The % of a blood sample that is occupied by RBC

What is another name for the haematocrit?

Packed Cell Volume (PCV)

What would cause an decreased haematocrit?

Anaemia, bleeding, menstruation

What increases haematocrit?

Dehydration

What is plasma composed of?

-Water (91 - 93%)
-Plasma proteins (6 - 8%)- 1400 identified
Other constituents
-Nutrients
-Glucose, lipids, amino acids
-Nitrogenous wastes
-Gases
-Electrolytes
-Hormones

Where are most plasma proteins produces?

The liver
Except globulin gamma antibodies which are produced in lymphoid tissue

List the plasma proteins

• Albumin
• Globulins
• Fibrinogens
• Others (<1%) are regulatory proteins including enzymes and hormones

What % of plasma proteins does albumin account for?

60%

What are the functions of Albumin?

• Major contribution to viscosity
• Fluid balance - oncotic pressure
• Carrier for hormones, drugs

What % of plasma proteins does globulin account for?

36%

Name the types of Globulin and their functions?

Alpha, beta
•Transport of lipids, fat soluble vitamins, hormones
Gamma
• Antibodies - produced in lymphoid tissue

What % of plasma proteins does fibrinogen account for?

4%

What is the function of fibrinogen?

blood clotting (Haemostasis)

List the formed elements of blood

• Erythrocytes (red blood cells)
• Leukocytes (white blood cells)
• Thrombocytes (platelets)

How many Erythrocytes are there in blood?

• 4.3 million - 5.9 million/uL (males)
• 3.5 million - 5.5 million/uL (females)

How many leukocytes are in the blood?

4,500 - 11,000/uL

How many thrombocytes are in the blood?

150,000 - 400,000/uL

uL

Microlitre x10^-6- 1 millionth of a litre

What do thrombocytes (platelets) arise from?

Megakaryocytes- fragments of megakaryocytes

What is the diameter of thrombocytes?

1.5 - 3um

Do thrombocytes have a nucleus?

No

Do thrombocytes have mitochondria?

Yes

What is the lifespan of thrombocytes?

10 days

What are the functions of thrombocytes (platelets)?

Intracellular granules hold proteins and other factors
• Prevent blood loss
• Wound healing and maintenance of blood vessel integrity
• Immune functions

Describe the shape of erythrocytes

biconcave discs

Why are they shaped like this?

Structure designed for function- Large surface area for gases to diffuse

What is the diameter and thickness of erythrocytes?

• 6 - 8 mm in diameter
• 2.5 mm thick

Do erythrocytes have a nucleus?

No, they are anucleate

Do erythrocytes have mitochondria?

No

How do erythrocytes produce energy?

by anaerobic means- glycolysis

What is the lifespan of red blood cells?

120 days

What are the functions of erythrocytes?

1. Transport of O2
2. Transport of CO2
3. Regulation of pH

Transport of O2 %

• 1% dissolved in plasma
• 99% bound to haemoglobin

Transport of CO2 %

• 10% (or less) dissolved in plasma
• 30% (or less) bound to haemoglobin and plasma proteins- binds to amino terminus of proteins
• 60% (or more) as bicarbonate in the red blood cell

How is blood pH regulated?

Two mechanisms
- bicarbonate system
- haemoglobin

Bicarbonate System steps

1. Cytoplasm contains the enzyme carbonic anhydrase
2. Carbonic anhydrase catalyses the formation of carbonic acid
3. Carbonic acid quickly dissociates into bicarbonate and hydrogen ions

Give reversible equation

CO2 + H20 <> H2CO3 <> HCO3- + H+

How does the Principle of Le Chatalier describe the bicarbonate system?

Where CO2 is high, reaction will go to right, producing H+ ions (decreasing pH)

Haemoglobin in Regulation of Blood pH

1. Most of the H+ produced from carbonic acid binds to haemoglobin
2. The HCO3- can leave the cell to act as a buffer in the plasma
3. HCO3-/Cl- antiporter carries Cl- into the cell and HCO3- out (Chloride shift)

Haemoglobin also binds some CO2 directly

Antiporter

A carrier protein that transports two molecules acrss the plasma membrane in opposite directions.

Symporter

transporter that carries two different ions or small molecules, both in the same direction

How are leukocytes identified on a stained blood smear/

- size
- shape of nucleus
- presence or absence of cytoplasmic granules

List the different types of white blood cells in order of relative abundance in blood (highest to lowest)

Neutrophils
Lymphocytes
Monocytes
Eosinophils
Basophils

Never
Let
Monkeys
Eat
Bananas

What % of WBCs do neutrophils account for?

54-62%

What % of WBCs do lymphocytes account for?

25-33%

What % of WBCs do monocytes account for?

3-7%

What % of WBCs do eosinophils account for?

1-3%

What % of WBCs do basophils account for?

0-1%

What do some leukocytes have?

cytoplasmic granules

What is the function of cytoplasmic granules?

immune defence- contain microbicidal agents such as digestive enzymes

What is another name for granulocytes?

polymorphonuclear leukocytes (PMNs)

Where do polymorphonuclear leukocytes get their name from?

their nuclei are of irregular shape, either bilobed or trilobed

List Polymorphonuclear Leukocytes

- Neutrophils
- Eosinophil (major influence in hypersensitivity and allergic reactions)
- Basophil

Describe neutrophils in terms of size

Large cells

Describe the lifespan of neutrophils

Short lived (2-3 days

Function of neutrophils

Primary function is phagocytosis
• Travel quickly from the blood to the site of infection
• Present in tissue during acute inflammation

Describe staining of eosinophils

Basic granules 'love' red acid dye (eosin)

Describe lifespan of eosinophils

13 days but spend most of this in the tissues

Describe structure of eosinophils

Bilobed in early development but can become
multilobed as they mature
•Lobes may be covered by granules

Function of eosinophils

- Anti parasitic activity
- involved in allergy and inflammation

Describe staining of basophils

Acidic granules 'love' basic blue dye

Describe lifespan of basophils

2-3 days after maturity- very short

Describe structure of basophils

Lobed nuclei

Function of basophils

- Anti-parasitic activity
- Involved in inflammation and allergy

What is another name for agranulocyes?

mononuclear leukocytes

Where do mononuclear leukocytes get their name from?

their nuclei are regular and not lobed

List Mononuclear Leukocytes

- Lymphocytes
- Monocytes (Kidney Shaped)

List the types of lymphocytes

T cells, B cells, and natural killer cells

Describe size and shape of natural killer cells

larger, less regular in shape

Describe size and shape of B lymphocytes, T lymphocytes

Large almost spherical nucleus surrounded by a very
small halo of cytoplasm

Describe shape of monocytes

Regular kidney-shaped nuclei

Describe lifespan of monocytes

Circulate in blood for 1-2 days

What type of agranulocytes can migrate into tissues and differentiates into macrophages?

Monocytes