ANATOMY & PHYSIOLOGY – UNIT I
CHAPTER 4: BLOOD
(For General Nursing & Midwifery – GNM 1st Year)
These notes on blood – composition, functions and clotting are prepared specially for GNM 1st year nursing students, covering all important topics as per the anatomy and physiology syllabus.
INTRODUCTION
Blood is a vital fluid of the human body. It plays an important role in transportation, protection, regulation, and healing. For nurses, knowledge of blood is essential because many clinical procedures such as blood transfusion, IV therapy, anemia management, and emergency care are directly related to blood.
DEFINITION OF BLOOD
Blood is a specialized connective tissue that circulates in the blood vessels and performs various vital functions necessary for life.
a) COMPOSITION AND FORMATION OF BLOOD
COMPOSITION OF BLOOD
Blood is composed of two main parts:
- Plasma
- Formed elements
1. PLASMA
Plasma is the liquid part of blood and forms about 55% of total blood volume.
Composition of Plasma
- Water (about 90%)
- Plasma proteins
- Albumin
- Globulin
- Fibrinogen
- Electrolytes
- Nutrients
- Hormones
- Waste products
Functions of Plasma
- Helps in transport of nutrients and hormones
- Maintains blood volume
- Helps in blood clotting (fibrinogen)
- Maintains osmotic pressure
2. FORMED ELEMENTS
Formed elements make up about 45% of blood and include:
- Red Blood Cells (RBCs)
- White Blood Cells (WBCs)
- Platelets
RED BLOOD CELLS (RBCs)
- Also called erythrocytes
- Contain hemoglobin
- Life span: 120 days
Functions of RBCs:
- Transport oxygen from lungs to tissues
- Transport carbon dioxide from tissues to lungs
WHITE BLOOD CELLS (WBCs)
- Also called leukocytes
- Protect the body from infection
- Life span: varies from hours to days
Functions of WBCs:
- Defense against infection
- Immunity
- Destroy foreign bodies
PLATELETS
- Also called thrombocytes
- Help in blood clotting
- Life span: 7–10 days
FORMATION OF BLOOD (HAEMOPOIESIS)
Haemopoiesis is the process of formation of blood cells.
- Occurs mainly in red bone marrow
- All blood cells are formed from stem cells
Sites of blood formation:
- Bone marrow (main site)
- Liver and spleen (during fetal life)
b) FUNCTIONS OF BLOOD
Blood performs three major groups of functions:
1. TRANSPORT FUNCTIONS
- Transport of oxygen and carbon dioxide
- Transport of nutrients
- Transport of hormones
- Transport of waste products
2. PROTECTIVE FUNCTIONS
- Protection against infection (WBCs)
- Immunity
- Blood clotting prevents blood loss
3. REGULATORY FUNCTIONS
- Regulation of body temperature
- Maintenance of acid–base balance
- Maintenance of fluid balance
c) BLOOD CLOTTING, BLOOD GROUPING AND CROSS MATCHING
BLOOD CLOTTING
Blood clotting is the process by which blood changes from a liquid to a solid state to stop bleeding.
Importance of Blood Clotting:
- Prevents excessive blood loss
- Helps in wound healing
BLOOD GROUPING
Blood grouping is done based on the presence or absence of antigens on RBCs.
ABO Blood Group System
- Group A
- Group B
- Group AB
- Group O
Rh Factor
- Rh positive
- Rh negative
CROSS MATCHING
Cross matching is a test done before blood transfusion to ensure compatibility between donor and recipient blood.
Importance of Cross Matching:
- Prevents transfusion reactions
- Ensures safe blood transfusion
d) BLOOD PRODUCTS AND THEIR USES
BLOOD PRODUCTS
Blood can be separated into different components known as blood products.
Common Blood Products
- Packed Red Blood Cells (PRBCs)
- Plasma
- Platelet concentrate
- Fresh frozen plasma (FFP)
USES OF BLOOD PRODUCTS
- PRBCs – used in anemia and blood loss
- Plasma – used in clotting disorders
- Platelets – used in bleeding disorders
- FFP – used in liver disease and massive bleeding
IMPORTANCE OF BLOOD IN NURSING PRACTICE
- Helps in safe blood transfusion
- Helps in managing anemia and shock
- Essential for emergency care
- Important for monitoring patient condition
KEY POINTS FOR EXAM
- Blood is a connective tissue
- Plasma forms 55% of blood
- RBC life span is 120 days
- Platelets help in clotting
- Cross matching is essential before transfusion
FINAL NOTE FOR STUDENTS
Blood-related questions are very common in exams. Focus on definitions, functions, and components. Write answers in clear headings and points to score well.