Cell Histology - Skin, Muscle, Bone Structure & Function

Cell Histology - Skin, Muscle, Bone Structure & Function

Overview

  • Course: Anatomy & Physiology 1 (ANAT 1015) at Loyalist College of Applied Arts & Technology

Review

Planes & Anatomical Terminology

  • Essential for understanding body organization and structure.

Levels of Tissue Organization

  • Types of Tissue: Epithelial, Connective, Muscle

Required Readings

  • Text: Anatomy & Physiology by Openstax College, Rice University

    • Chapters Included:

    • Chapter 4: Sections 4.1 - 4.5

    • Chapter 6: Sections 6.2 - 6.4

Learning Objectives

  • Epithelial, Muscle and Connective Tissues: Identify and describe their roles within the human body.

  • Skeletal Divisions and Bone Functions:

    • Identify the skeletal divisions.

    • Differentiate between compact and spongy bone.

  • Bone Cells: Describe the four types.

  • Bone Types: Classify and identify the structure of long bones.

  • Bone Development: Understand the process of bone formation.

Key Terms

  • Tissue: A group of similar cells that perform a common function.

  • Histology: The biology of tissue.

  • Arthrology: Study of joints, articulations between bones.

  • Osteology: Study of the structure and function of the skeleton and bony structures.

Tissues

  • Function of Tissues: Each tissue has a specialized function that aids in maintaining homeostasis.

  • Cell Arrangement: Tissues may form thin sheets (one cell deep) or large masses (millions of cells).

Epithelial Tissue

  • Definition: Covers and protects body surface, lines cavities, transports substances, and forms glands.

  • Functions:

    • Protection: Shields body from injury and microorganisms.

    • Sensory: Contains sensory cells in skin, nose, eye, and ear.

    • Secretion: Glandular epithelium secretes hormones, mucus, juices, and sweat.

    • Absorption: Allows for nutrient absorption and gas exchange in gut/lungs.

    • Excretion: Facilitates concentration and excretion of waste in urine.

  • Characteristics:

    • Composed of one or more layers of closely arranged cells with minimal extracellular matrix.

    • Forms sheets or glands.

  • Examples of Epithelial Tissue:

    • Outer Layer of Skin: Protects the body.

    • Lining of Tracts: Respiratory, digestive, urinary, and reproductive.

    • Glands: Involved in secretion.

Connective Tissue

  • Definition: Supports, connects and holds body parts together, transports substances, and protects against invasion.

  • Components:

    • Cells

    • Ground substance

    • Protein fibers

  • Functions:

    • Supports other tissues (e.g., muscle sheath, tendons).

    • Protects tissues.

    • Connective tissue is plentiful and varies in type.

  • Types of Connective Tissue:

    • Fibrous: Dense, loose (areolar), adipose, irregular, regular, elastic.

    • Bone: Compact and cancellous (spongy).

    • Cartilage: Hyaline and fibrocartilage.

    • Blood.

Muscle Tissue

  • Properties: Allows for movement; excitable and contractile.

  • Types of Muscle Tissues:

    • Skeletal Muscle:

      • Histology: Long cylindrical fibers, striated, multi-nucleated.

      • Function: Voluntary movement, heat production, organ protection.

      • Location: Attached to bones and entrance points of the body (mouth, anus).

    • Cardiac Muscle:

      • Histology: Short branched fibers, striated, single central nucleus.

      • Function: Pumps blood involuntarily.

      • Location: Heart.

    • Smooth Muscle:

      • Histology: Short, spindle-shaped fibers, non-striated, single nucleus.

      • Function: Involuntarily moves food, controls respiration, regulates blood flow.

      • Location: Walls of major organs and passageways.

Osteology

  • Total Bones in Adult Body: 206.

    • Divided Into:

    • Axial Skeleton: 80 bones

    • Appendicular Skeleton: 126 bones.

  • Functions of Bones:

    • Attachment for muscles.

    • Mechanical basis for movement.

    • Protection of internal organs.

    • Framework support.

    • Storage of calcium and phosphorus salts.

    • Production of blood cells.

Bone Structure

  • Types of Bone:

    • Compact Bone: Dense outer layer, protection, and strength.

    • Spongy Bone: Less dense, contains trabeculae filled with marrow.

  • Trabecular Structure:

    • Contains interconnecting spaces.

    • Trabeculae Function: Support and protect red marrow; their lightweight design aids in movement.

Microscopic Bone Structure

Compact Bone (Cortical Bone)

  • Basic Unit: OSTEONS.

  • Components of Osteon:

    • Central Canal: Houses blood vessels and nerves.

    • Lamellae: Cylindrical calcified matrix layers.

    • Lacunae: Fluid-filled spaces that house bone cells.

    • Canaliculi: Canals radiating from lacunae.

Spongy Bone (Cancellous/Trabecular)

  • Characteristics:

    • Lattice-like network of thin bony columns (trabeculae).

    • Contains red marrow for blood cell production.

    • Found in epiphyses of long bones, short, flat, and irregular bones.

Bone Cells

Types of Bone Cells:

  • Osteogenic Cells:

    • Unspecialized stem cells derived from mesenchyme.

    • Only bone cells that divide and become osteoblasts.

  • Osteoblasts:

    • Bone-building cells synthesizing collagen and initiating calcification.

    • Encapsulate themselves in matrix and become osteocytes.

  • Osteocytes:

    • Mature bone cells; maintain metabolism, exchange nutrients and wastes in lacunae.

  • Osteoclasts:

    • Large cells involved in the breakdown and remodeling of bone tissue.

    • Responsible for normal bone growth through resorption.

Structure of Bone

  • Long Bones: Greater length than width, consisting of:

    • Diaphysis: Shaft.

    • Epiphysis: Ends of the bone (proximal and distal).

    • Metaphysis: Junction of diaphysis and epiphysis.

    • Epiphyseal Plate: Allows growth in length before closure becomes epiphyseal line.

  • Additional Structures:

    • Articular Cartilage: Covers epiphysis; facilitates movement at joints.

    • Periosteum: Dense irregular connective tissue covering bone not covered by cartilage.

    • Medullary Cavity: Space within diaphysis containing yellow marrow.

    • Endosteum: Thin membrane lining medullary cavity.

    • Nutrient Artery: Supplies blood to bone, entering via nutrient foramen.

Bone Development

  • Ossification: Development and formation of bone.

    • Primary Ossification Center: Forms before birth.

    • Secondary Ossification Center: Develops after birth at ends of long bones.

    • Epiphyseal Plate: Visible in children and allows for lengthwise growth; replaced by epiphyseal line after maturity (around 21 years).

Classification of Bones

  • Long Bones: (e.g., Femur, Humerus, Phalanges) provide support.

  • Short Bones: (e.g., Carpal/Tarsal bones) vary in shape.

  • Flat Bones: (e.g., Cranium, Sternum, Scapula) offer protection and muscle attachment.

  • Irregular Bones: (e.g., Vertebrae, Pelvis) attach muscles, tendons, ligaments; form joints.

  • Sesamoid Bones: Small oval bones within tendons (e.g., Patella).

Knowledge Check

  • Diagram of a long bone with labels:

    • Diaphysis - RED

    • Proximal Epiphysis - BLUE

    • Distal Epiphysis - ORANGE

    • Proximal Metaphysis - YELLOW

    • Distal Epiphysis - GREEN

Key Takeaways

  • Function of Tissues: Epithelial, connective, muscle tissues are essential.

  • Skeletal Structure: Division into axial and appendicular skeleton.

  • Bone Composition: Protective compact bone, spongy red marrow.

  • Bone Cells: Role of osteogenic cells, osteoblasts, osteocytes, osteoclasts in bone health.

  • Bone Formation: Primary and secondary ossification processes.

  • Bone Classification: Bones categorized by shape, structural labels for long bones.

Questions?