FHSC 203 - Human Body Tissues

Overview of Tissues

• Tissues are groups of cells sharing a common structure and function.
• Four primary tissue types: Epithelial, Muscle, Connective, and Nervous.

Epithelial Tissue

• Composed of tightly packed cells forming layers, with high regeneration rates.
• Two major types:
  • Glandular epithelium: Found in exocrine and endocrine glands, secretes fluids.
  • Lining epithelium: Forms skin outer layers and lines internal organs.
• Features of epithelial tissue include:
  • Apical surface (outer), Basal surface (inner).
  • Microvilli for absorption; Cilia for movement of materials.
  • Supported by underlying connective tissue, forming the basement membrane.
  • Avascular (lacking blood vessels) but innervated.

Classification of Epithelia

• Classified by cell shape:
  • Squamous (flat)
  • Cuboidal (height equals width)
  • Columnar (tall)
• Classified by arrangement:
  • Simple (single cell layer for absorption)
  • Stratified (multiple layers for protection, e.g., skin, mouth).

Types of Epithelial Membranes

• Cutaneous membrane: Skin; keratinized stratified squamous epithelium.
• Mucous membranes: Line cavities opening to outside (e.g., respiratory tract).
• Serous membranes: Line closed cavities (e.g., peritoneum, pleura, pericardium) and secrete serous fluid.

Glandular Epithelium

• Consists of one or more cells producing secretions.
• Classified by:
  • Site of secretion:
    • Endocrine: Ductless, secrete hormones into circulation.
    • Exocrine: Secrete through ducts to body's surfaces (e.g., sweat glands).
  • Number of cells:
    • Unicellular: e.g., goblet cells.
    • Multicellular: usually with ducts.

Tissue Repair Process

• Inflammation: Release of inflammatory chemicals, dilation of blood vessels, clotting, and phagocytosis of debris.
• Organization: Blood clot replaced by granulation tissue, and epithelium begins to regenerate.
• Regeneration and fibrosis: Maturation of fibrous tissue, thickening of the epithelium, finalizing with the formation of scar tissue.

Types of Muscle Tissue

• Composes approximately 60% of body mass, and categorized as:
  • Cardiac muscle: Found in the heart, involuntary control.
  • Skeletal muscle: Attached to bones, voluntary control.
  • Smooth muscle: Lines blood vessels and organs, involuntary.

Nervous Tissue

• Comprises the Central Nervous System (CNS) and Peripheral Nervous System (PNS).
• Functions in signal transmission and physiological responses.
• Contains:
  • Neurons: Conduct electrical impulses.
  • Neuroglia: Supportive cells assisting neurons.

Blood Composition

• Blood is a specialized tissue made of plasma and cellular elements.
• Average volume is 5-6 L in males, 4-5 L in females, comprising about 8% of body weight.
• pH ranges from 7.35 to 7.45, typically at a temperature of 38°C.

Functions of Blood

• Distribution: Transports oxygen, nutrients, hormones, and waste.
• Regulation: Maintains temperature, pH balance, and fluid volume.
• Protection: Initiates clot formation to prevent blood loss and combats infection through white blood cells and antibodies.

Plasma

• Comprises about 55% of blood volume; mostly water (95%).
• Dissolves various solutes, including proteins, nutrients, electrolytes, and gases.

Cellular Elements of Blood

• Red Blood Cells (RBCs): Biconcave discs with a mean diameter of about 7.5µm; primarily responsible for oxygen transport.
• Production occurs during various stages of embryonic and postnatal development, primarily in the bone marrow.

Hematopoiesis and Erythropoiesis

• Hematopoiesis: Blood cell formation involves hemocytoblasts and happens in the red bone marrow.
• Erythropoiesis: Production of RBCs through several developmental stages until mature erythrocytes are formed.

Connective Tissue

• Contains specialized cells (e.g., fibroblasts) and a matrix consisting of ground substance and fibers.
• Cartilage types include hyaline, elastic, and fibrocartilage, all maintaining unique hydration and resilience properties.