The Role of Blood in Forensics and Biology

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Questions and Answers

What is the correct method for storing samples of blood?

Seal in a plastic bag and expose to sunlight.

Freeze the samples immediately.

Package in an envelope and store dry and cool. (correct)

Store in a warm environment to prevent degradation.

What is the first step in collecting a water sample?

Collect water with a clean pipette or syringe. (correct)

Mix the water with another chemical first.

Use a plastic syringe to inject air.

Pour the water directly into an envelope.

When dealing with dry blood, how should one prepare the swab for collection?

Soak the swab in hot water before use.

Cut the swab to expose more surface area.

Leave the swab dry to avoid contamination.

Moisten a swab with sterile/distilled water. (correct)

What is a critical question when assessing the nature of a blood stain?

Does the stain contain blood or another substance? Signup and view all the answers

In case of a blood sample suspected to be human, what additional investigation must be performed?

Identify if the blood is that of the victim, the accused, or others. Signup and view all the answers

What can the presence of blood at a crime scene indicate about the victim's status?

The victim may have survived the initial attack. Signup and view all the answers

Which type of blood is bright red and indicates oxygenation?

Arterial Blood Signup and view all the answers

How does blood contribute to the regulation of body temperature?

By circulating between body regions to equilibrate temperature. Signup and view all the answers

Which characteristic distinguishes venous blood from arterial blood?

Venous blood appears dark red due to increased carbon dioxide levels. Signup and view all the answers

What indicates that a crime may have been committed only a few hours to days prior?

Brownish blood with clots. Signup and view all the answers

What is one of the primary functions of blood?

To regulate internal body temperature. Signup and view all the answers

What is indicated by the color and consistency changes in blood at a crime scene?

The length of time since the blood was shed. Signup and view all the answers

What can lead to metabolic acidosis and potentially affect blood pH levels?

Excess carbon dioxide accumulation. Signup and view all the answers

What is the viscosity of blood compared to water?

4-5 times more viscous than water Signup and view all the answers

What is the specific gravity of blood?

1.065 Signup and view all the answers

What is the normal pH range of blood?

7.35 - 7.45 Signup and view all the answers

Which type of blood cell is primarily responsible for oxygen transport?

Red Blood Cells Signup and view all the answers

What is the normal range for white blood cells in mm3?

5,000 - 10,000 Signup and view all the answers

What is the function of platelets in the blood?

Blood coagulation Signup and view all the answers

What is the liquid portion of blood called?

Plasma Signup and view all the answers

Which of the following is NOT a component of the formed elements in blood?

Nutrients Signup and view all the answers

Study Notes

Importance of Blood Study

Blood can be used as evidence in legal cases.
Blood analysis can help determine disputed parentage in custody cases.
Blood can be used for DNA typing instead of buccal swabs.
Blood can help determine the time of death and how long the victim survived the attack.
- A pool of blood indicates the victim may have been alive after the attack.
- No pool of blood suggests immediate death.
Blood spatter analysis can determine the direction of escape for the victim or assailant.
- Circular blood spatter indicates dripping blood.
- Angled blood spatter indicates blood being projected.

Nature of Blood

Blood is the largest circulating tissue in the body.
It has a fluid-like consistency due to its vital substances.
It contains blood cells, nutrients, and electrolytes.
It circulates within the cardiovascular system.
- Transports oxygen, nutrients, and waste products.

Functions of Blood

Transportation:
- Gases (oxygen and carbon dioxide)
- Nutrients
- Waste products
Temperature Regulation
pH Regulation:
- Maintains a slightly alkaline pH (7.35-7.45).
- Metabolic acidosis can cause disease, such as arthritis.
Medication Transport:
- Delivers medicine to affected parts of the body.

Kinds of Blood

Arterial Blood (Capillary Blood):
- Bright red in color due to oxygen transport.
- Oxygenated blood.
Venous Blood:
- Increased amount of CO2.
- Dark red in color.
- Non-oxygenated blood.

Characteristics of Blood

Color:
- Bright red (arterial blood)
- Dark red (venous blood)
Volume: 70% of total body weight.
- 80-85 mL/kg body weight.
Viscosity:
- Resistance of blood to flow.
- Thick and sticky.
- 4-5 times more viscous than water.
Specific Gravity:
- Blood = 1.065 due to cellular elements.
- Water = 1.000.
pH Reaction:
- Slightly alkaline (pH = 7.35-7.45).
- Lower than 7 is acidic.
- Higher than 7 is basic (alkaline).

Composition of Blood

A. Formed Elements (35%)*
Red Blood Cells (Erythrocytes):
- Number: 5,000,000 RBCs/mm3.
- Shape: Biconcave disc.
- Hemoglobin (Hb):
  - Coloring matter of blood.
  - Pigment found in the cytoplasm of RBCs.
  - Carries and transports oxygen.
White Blood Cells (Leukocytes):
- Number: 5,000-10,000/mm3.
- Soldiers of the Body.
  - Agranulocytes:
    - Monocytes
    - Lymphocytes
  - Granulocytes:
    - Eosinophils
    - Neutrophils
    - Basophils
Platelets (Thrombocytes):
- Number: 150,000-350,000/mm3.
- Function: Blood coagulation (blood clotting).
B. Liquid Portion (65% of total blood volume)*
Plasma: Straw liquid portion of the blood.
Serum: Straw-yellowish liquid when blood is allowed to clot
- Used for testing such as drug analysis.

Collection, Preservation, Packing, and Transportation of Blood Specimens

Blood on Removable Materials:
- Remove the whole object.
- Pack in a paper bag or envelope, keep dry and cool.
Pools of Blood:
- Collect samples by swabbing from various locations.
- Pack in an envelope, store dry and cool.
Blood in Water:
- Collect water with a clean pipette or syringe.
- Pour into a clean, dry test tube or vacuum tube with a purple cork.
Dry Blood:
- Moisten a swab with sterile/distilled water.
- Rub the swab on the stain until it becomes brown/red or absorbs all the blood.
- Pack in a swab wrapper or folded paper, store dry and cool.

### Problems in the Study of Blood

Locating Blood:
- Determining where to search for blood.
Specimen Collection:
- Proper preservation and transportation of blood specimens.
Blood Stain Identification:
- Determining if the stain is blood.
Blood Source Identification:
- Determining if the blood is human or animal.
Blood Origin Identification:
- Determining if the blood came from the victim, accused, or other persons.

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Description

Explore the critical functions and importance of blood in both forensic science and biological contexts. This quiz will cover how blood serves as evidence in legal situations, its composition, and its vital roles within the human body. Test your knowledge on blood analysis and its implications in various scenarios.