Physiology Chapter 2: Blood Functions and Characteristics

Study Notes

Blood is a liquid connective tissue circulating through blood vessels, pumped by the heart.
Functions:
- Transportation:
  - Transports nutrients (amino acids, lipids, glucose), hormones, and oxygen to cells.
  - Transports wastes and carbon dioxide away from cells.
- Regulation:
  - pH buffering (7.35-7.45): Role of hydrogen and bicarbonate ions.
  - Body temperature regulation (water and vasodilation of surface vessels).
- Protection:
  - Clot formation: Minimizes blood loss when a vessel is damaged.
  - Protection against foreign substances (antibodies and white blood cells).

Blood volume:
- Males: 5-6 liters
- Females: 4-5 liters
- Varies based on size and gender of individual.
Color:
- Red, with arterial blood being brighter (higher oxygen content) and venous blood being darker (lower oxygen content).
pH:
- Arterial blood (7.35-7.45)
- Venous blood (7.32-7.42)

Cellular portion (formed elements):
- Lower portion in a blood sample tube (buffy coat + red blood cells).
Fluid portion (plasma):
- Upper portion in a blood sample tube -The average adult has a blood volume of roughly 5 liters. -The blood plasma volume totals of 2.7-3.0 liters in an average human.

Plasma (Fluid portion):
- Water (91-92%): Transport medium for materials carried in the blood.
- Proteins (6-8%): Maintain blood volume and blood pressure.
  - Albumin (60%): Transport protein, steroid hormones, & maintains blood volume & pressure.
  - Globulins (35%): Transport hydrophobic lipids, fat-soluble vitamins, ions and hormones; Gamma is antibodies for immunity.
  - Fibrinogen (4%): Coagulation protein.
  - Regulatory proteins (<1%): Enzymes, proenzymes and hormones.
Other solutes (1-2%): Electrolytes, organic nutrients (ATP production, growth, maintenance of cells), organic wastes (urea, creatinine, bilirubin), dissolved gases (O2, CO2).

Number: 4.6-6.2 million/mm³ in men, 4.5-5.1 million/mm³ in women.
Shape: Flat, bi-concave discs lacking a nucleus and mitochondria.
Size: 7.5 µm in diameter and 2.5 µm thick.
Derived from precursors in bone marrow
Importance of shape: Provides increased surface area for diffusion of O2 and CO2.
Functions:
- Transporting hemoglobin, which carries oxygen from lungs to tissues.
- Contains carbonic anhydrase, catalysing the reversible reaction between carbon dioxide and water, creating carbonic acid (H2CO3).
- Hemoglobin is responsible for most of the blood's acid-base buffering power.
Life span: 70-150 days.
Degradation: Macrophages in the liver and spleen phagocytose damaged RBCs; hemoglobin is broken down into heme and globin; heme breaks down to iron (recycled), biliverdin, and bilirubin (excreted in bile).

Areas producing RBCs:
- Yolk sac (early embryonic life)
- Liver, spleen, lymph nodes (mid-gestation)
- Bone marrow (later gestation and throughout life).

Decreased tissue oxygenation is the most important regulator of red blood cell production.
Other factors include low oxygen concentration, high altitude, lung diseases, and heart failure.
Erythropoietin (EPO) is secreted by the kidney in response to low oxygen levels, stimulating erythropoiesis (RBC production) in bone marrow.

Mobile units of the immune system, destroying old/abnormal cells and attacking infections like bacteria and viruses.
Phagocytosis and antibody formation are common mechanisms.
Types & functions:
- Neutrophils, monocytes, eosinophils, basophils, lymphocytes (B & T cells). - Function in innate and adaptive immunity.
Lifespan: 13–20 days.
Location of production: Partially in bone marrow, partially in lymph tissue.

Cellular fragments (lack nuclei) from megakaryocytes in bone marrow.
Irregularly shaped.
Critical for hemostasis (stopping bleeding and maintaining vascular integrity).
Release factors to stimulate the coagulation cascade, producing fibrin to form a clot.
Average lifespan: 7-14 days.

Plasma is the liquid part of whole blood containing clotting factors.
Serum is plasma without clotting factors, obtained after blood clotting in tubes without anticoagulants.

Mucous membrane color (pink=well-oxygenated, blue=poorly oxygenated).
Capillary refill time (CRT) (normal <2 seconds; delayed CRT indicates perfusion issues).