Human Blood
“Blood is a connective tissue that circulates throughout the body and transports oxygen, nutrients, and waste.”
Introduction
Blood is a fluid connective tissue that plays a vital role in transportation, protection, and regulation in the human body. It consists of plasma and blood cells.
Composition of Blood
- Plasma: The liquid part (~55% of blood), composed mainly of water, proteins, glucose, and ions.
- Blood Cells:
- Red Blood Cells (RBCs): Carry oxygen using hemoglobin. Lifespan ~120 days.
- White Blood Cells (WBCs): Fight infection. Types include lymphocytes, monocytes, etc.
- Platelets: Help in blood clotting.
Functions of Blood
- Transports oxygen and carbon dioxide
- Delivers nutrients and hormones
- Removes waste products
- Regulates body temperature and pH
- Fights infections via WBCs
- Clots wounds through platelets
Blood Groups
- Classified into A, B, AB, and O groups based on the presence of antigens on RBCs.
- Rh factor: Positive or negative depending on the presence of Rh antigen.
- Universal Donor: O negative
- Universal Recipient: AB positive
Important Points
- Hemoglobin is an iron-containing pigment in RBCs.
- WBC count increases during infection.
- Platelet deficiency can lead to excessive bleeding.
- Average human has 4.5–6 liters of blood.