Tissue to Organs and Organ Systems

The Human Body: Tissues To Organs and Organ Systems

Learning Outcomes

  • ALO1: Describe how tissues provide the structural and functional basis of organs.

  • ALO2: Discuss the role of tissue types in organ systems.

  • ALO3: Describe the main organ systems in the human body.

  • ALO4: Explain how organs function as organ systems in the body.

  • Outcome: By the end of this lecture, learners will have a comprehensive understanding of the above points.

Tissue Types And Features

  • Recap Quiz:

    1. Loose connective tissue - Areolar connective tissue

    2. Simple columnar epithelium - Small intestines

    3. Membranous epithelium - Stratified squamous (epidermis of skin)

    4. Dense connective tissue - Regular connective tissue (tendon)

    5. Irregular dense connective tissue - Dermis of the skin

    6. Loose (reticular) connective tissue - Lymph nodes

Specialised Connective Tissue

Cartilage

  • Composition:

    • Specialised cells (chondrocytes) in a dense extracellular matrix.

    • Primarily comprises type II collagen mesh, proteoglycans, glycosaminoglycans (e.g., aggrecan, chondroitin sulfate, hyaluronic acid).

    • Highly hydrated, essential for mechanical protection and low friction movement.

Chondrocytes

  • Function:

    • Maintain and produce extracellular matrix.

    • Rarely divide and have low proliferation capacity.

    • Found in lacunae within the matrix.

  • Surroundings:

    • Covered by dense irregular connective tissue (perichondrium): consists of an outer fibrous layer and an inner cellular layer.

    • No direct blood vessels or nerves are present except in the perichondrium.

Types of Cartilage

  1. Hyaline Cartilage

    • Most abundant type; provides flexibility and support, reduces friction in joints.

    • Surrounded by perichondrium except in articular cartilage.

  2. Fibrocartilage

    • Strongest type; chondrocytes within collagen fiber bundles.

    • Lacks perichondrium, typically found in intervertebral discs creating annulus fibrousus.

  3. Elastic Cartilage

    • Contains chondrocytes in a network of elastic fibers.

    • Perichondrium present; provides strength and elasticity.

Specialised Connective Tissue: Bones

  • Composed of:

    • Bone (osseous) tissue, periosteum, endosteum, nerves, blood vessels, and bone marrow.

  • Functions:

    • Produces red and white blood cells, stores minerals, provides structure/support, protects organs, facilitates mobility.

    • Light yet strong, composed mainly of calcified type I collagen matrix.

Bone Structure and Architecture

  1. Compact Bone (Cortical Bone)

    • Forms the hard outer layer of bones surrounded by periosteum (external) and endosteum (internal).

    • Organized in structures called osteons (Haversian systems) around blood supply.

  2. Cancellous Bone (Spongy Bone)

    • Found at the ends of long bones; lacks osteons and features trabeculae (honeycomb structure).

    • Highly vascular and contains red bone marrow for blood cell production.

Bone Formation or Healing

  • Initial Stage: Immature (woven) bone formed as osteoid with irregular collagen I fiber arrangement.

  • Processes of Bone Formation:

    • Endochondral Ossification

    • Intramembranous Ossification

  • Replacement: Woven bone replaced by lamellar bone, characterized by organized collagen sheets (lamellae).

Specialised Connective Tissue: Blood

  • Facilitates body communication, nutrient and oxygen transport, waste removal, immunological functions, coagulation, and temperature regulation.

  • Composition:

    • Red blood cells (RBCs, erythrocytes), white blood cells (WBCs, leukocytes), and platelets circulating in blood plasma (straw yellow fluid).

Connective Tissue Diversity

  • Types include:

    • Dense connective tissue

    • Loose connective tissue

    • Cartilage

    • Adipose tissue

    • Bone

    • Blood

Muscle Tissue

  • Consists of specialized cells that contract upon stimulation.

  • Types of Muscle Tissue:

    1. Skeletal Muscle

      • Voluntary control, multi-nucleated fibers.

      • Visible striations.

    2. Smooth Muscle

      • Involuntary control, spindle-shaped single-nucleated cells, found in various internal organs.

    3. Cardiac Muscle

      • Involuntary control, branched fibers with intercalated discs; one or two nuclei per fiber.

Nervous Tissue

  • Contains specialized cells (neurons) for impulse conduction.

  • Neurons:

    • Transmit impulses between body regions, communicate at synaptic junctions.

  • Neuroglia (Glial Cells): Non-conducting support cells.

  • Components: Dendrites (signal reception transmits to the cell body.), Axons (signal transmission away from the cell body ranges from 1-2mm to a meter ), Schwann Cells (form myelin sheath), Node of Ranvier (increases signal speed).

Types of Neurons

  • Unipolar: Dendrite and axon together

  • Bipolar: Opposite ends for dendrite and axon

  • Multi-polar: Multiple dendrites with a single axon

Organs

  • Tissues combine to form organs, which are discrete structures with specific functions such as digestion, enzyme production, and hormone production.

The Skin as an Organ

  • Layers:

    1. Epidermis

    2. Papillary Dermis

    3. Reticular Dermis

    4. Hypodermis

    5. Muscle

  • Functions:

    • Protects the body, regulates temperature, provides sensory interface.

Organs And Organ Systems

  • No organ operates independently; all are part of cooperative organ systems.

  • Organ systems interact and cooperate with one another.

Organ Systems Overview

  • Integumentary System: Skin, hair, nails; protects and regulates temperature.

  • Skeletal System: Bones, cartilage, ligaments; provides support and protection.

  • Muscular System: Skeletal muscles, cardiac muscle, smooth muscle; enables movement.

  • Nervous System: Brain, spinal cord, nerves; regulates body functions.

  • Endocrine System: Hormone-releasing glands; regulates metabolism.

  • Cardiovascular System: Heart, blood vessels; transports nutrients and waste.

  • Immune/Lymphatic System: Returns tissue fluid to blood; defends against disease.

  • Respiratory System: Lungs; supplies oxygen and removes carbon dioxide.

  • Digestive System: Digestive tract; processes food and wastes.

  • Urinary System: Kidneys; removes metabolic waste and regulates chemistry.

  • Reproductive System: Gonads and structures; responsible for sexual reproduction.

Summary and Learning Outcomes

  • Reiteration of learning outcomes:

    • ALO1: Describe organizational structure of organs.

    • ALO2: Discuss tissue types in organ systems.

    • ALO3: Describe human organ systems.

    • ALO4: Explain organ functionality within systems.