Blood as a delivery system

Introduction to Blood as a Delivery and Removal System

  • Blood serves two primary roles:

    • Delivery System: Transports oxygen and nutrients to cells.

    • Removal System: Eliminates waste products from cells.

  • The learning objectives include:

    • Understanding major circulatory systems.

    • Transportation of substances into, throughout, and out of the body.

    • Familiarization with key terms and a glossary.

    • Understanding gas exchange during internal and external respiration.

Overview of Circulatory Systems

  • Major Circulatory Systems:

    • Systemic Circulation

    • Pulmonary Circulation

  • Important Blood Vessels:

    • Aorta (large vessel)

    • Inferior and Superior Vena Cava

  • Oxygenated vs. Deoxygenated Blood:

    • Oxygenated blood is represented as red; deoxygenated (less oxygen) is represented as blue.

    • Note: Deoxygenated blood still contains some oxygen, along with other nutrients and gases.

Transportation of Substances

  • Substances moved by the cardiovascular system:

    • Oxygen from the lungs to all body cells.

    • Nutrients and water from the intestinal tract to body cells.

  • The significance of oxygen:

    • Essential for cell survival; lack of oxygen can lead to irreversible damage in brain cells.

    • Baroreceptors and chemoreceptors help regulate blood flow to the brain to prevent unconsciousness.

Mechanism of Gas Exchange

  • Efficient exchange of oxygen into the bloodstream through pulmonary circulation.

  • Mechanism of diffusion across a one-cell thick epithelial tissue (alveolar epithelium).

    • The concentration gradient facilitates gas exchange:

      • PO2 in alveoli: ~100 mm Hg

      • PCO2 in alveoli: ~70 mm Hg

  • Diffusion Process:

    • Oxygen moves into blood; CO2 moves out due to this gradient.

    • In systemic circulation, cell PO2 < 40 mm Hg; cell PCO2 > 46 mm Hg.

  • Importance of thin alveolar epithelium for gas exchange efficiency:

    • Thicker epithelium (e.g., fluid accumulation) slows gas exchange efficiency.

Oxygen Transportation

  • Oxygen transportation details:

    • 2% dissolved in plasma; 98% transported by hemoglobin in red blood cells.

Nutrient Absorption and Digestion

  • Nutrients and fluid absorption primarily occurs in the gastrointestinal tract:

    • Extensive absorption takes place in the small intestine; minor absorption occurs in the stomach.

  • Key Types of Digestion:

    • Chemical Digestion: Enzymatic breakdown of food (e.g., salivary amylase, hydrochloric acid).

    • Mechanical Digestion: Physical breakdown (e.g., chewing, muscular contractions in the stomach).

  • Breakdown of macronutrients:

    • Carbohydrates to monosaccharides (e.g., glucose, fructose, galactose).

    • Proteins to amino acids, dipeptides, tripeptides.

    • Fats (triglycerides) to fatty acids, glycerol, monoglycerides.

Absorption Mechanisms

  • Small intestine anatomy aids absorption:

    • Circular folds and microvilli increase surface area for digestion and absorption.

    • Absorption details:

      • Carbohydrates (monosaccharides) via facilitated diffusion.

      • Proteins (amino acids, dipeptides, tripeptides) via diffusion.

      • Fats (short-chain fatty acids) via simple diffusion; larger molecules enter lacteals of the lymphatic system.

Water Absorption

  • Water enters the body primarily through osmosis influenced by electrolytes and salt balance.

  • Absorption in the gastrointestinal tract:

    • Predominantly in the small intestine, with some absorption in the large intestine (10% of total).

  • Water averages outflows and inputs:

    • A very small amount is lost through feces.

Liver Functions in Transportation

  • The liver serves crucial roles:

    • Filtration and cleaning of blood from the digestive tract.

    • Storage and modification of nutrients and wastes.

    • Excretion of waste products via bile or the kidneys (for water-soluble products).

    • Central concepts of liver function include:

      • Metabolizing substances (e.g., drugs) into usable forms.

      • The hepatic portal vein transports nutrients from the gastrointestinal tract to the liver.

Circulation of Immune Cells and Proteins

  • Transportation of immune cells and proteins is critical:

    • Leukocytes (white blood cells) travel in blood and can leave circulation through diapedesis to combat tissue damage.

    • Proteins in blood maintain oncotic pressure, assisting fluid retention.

    • Hormones exist in the bloodstream (water-soluble) and interstitial fluid (lipid-soluble must bind to carriers).

Waste Products and Metabolic Exchange

  • Metabolic waste generated from cellular activities must be expelled:

    • Waste excretion pathways include kidneys (urine), skin (sweat), gastrointestinal tract (feces), and lungs (exhalation).

    • Types of metabolic wastes include salts, nitrogenous wastes (urea, uric acid, creatinine), bile, and lactic acid.

Summary of Key Concepts

  • Major Circulatory Systems: systemic vs. pulmonary circulation.

  • Mechanism and significance of gas exchange during internal vs. external respiration.

  • Nutrient absorption and transportation pathways covered, stressing the role of liver metabolism.

  • Understanding the complete cycle of nutrient usage, waste generation, and removal in the body.