Tissues

A. Epithelial Tissue

Epithelial tissue covers body surfaces, lines cavities, and forms glands. It is classified based on cell shape and number of layers.

• Shapes: Squamous (flat), cuboidal (cube-shaped), columnar (tall and column-like).

• Number of Layers: Simple (one layer), stratified (multiple layers), pseudostratified (appears layered but is not).

• Location: Found on body surfaces (skin), lining of digestive tract, respiratory tract, and glands.

B. Connective Tissue

Connective tissue supports, binds, and protects other tissues and organs. It has diverse forms and functions.

• Blood: Fluid connective tissue that transports nutrients, gases, and wastes.

• Bone: Rigid tissue providing structural support and protection.

• Dense Regular Connective Tissue: Collagen fibers aligned in parallel (e.g., tendons, ligaments).

• Dense Irregular Connective Tissue: Collagen fibers in various directions (e.g., dermis of skin).

• Cartilage: Semi-rigid tissue for support and flexibility.

  • Hyaline: Most common; found in nose, trachea, ends of long bones.

  • Elastic: Flexible; found in ear and epiglottis.

  • Fibrocartilage: Strongest; found in intervertebral discs, pubic symphysis.

  • Location: Joints, respiratory tract, ear.

• Adipose: Stores fat for energy, insulation, and protection.

• Reticular: Forms supportive framework in lymphoid organs.

• Areolar: Loose connective tissue; binds skin to underlying organs.

• Resident Cells: Fibroblasts, adipocytes, macrophages, mast cells.

C. Muscular Tissue

Muscular tissue is responsible for movement and force generation.

• Skeletal Muscle: Voluntary, striated, attached to bones.

• Cardiac Muscle: Involuntary, striated, found in heart.

• Smooth Muscle: Involuntary, non-striated, found in walls of hollow organs.

• Location: Skeletal (bones), cardiac (heart), smooth (digestive tract, blood vessels).

D. Nervous Tissue

Nervous tissue transmits electrical impulses and processes information. It consists of neurons and supporting glial cells.

E. Membranes

Body membranes are sheets of tissue that cover or line body surfaces.

• Visceral Membranes: Cover organs.

• Parietal Membranes: Line body cavities.

• Cutaneous Membrane: The skin; protects the body surface.

F. Tissue Repair

Tissue repair involves regeneration (replacement with same cell type) or fibrosis (replacement with scar tissue).

Integumentary System

A. Layers of the Skin

The skin consists of two main layers: epidermis and dermis.

• Epidermis: Outer layer, composed of stratified squamous epithelium.

  • Stratum Corneum: Outermost, dead keratinized cells.

  • Stratum Basale: Deepest, mitotically active layer.

  • No Blood Vessels: Epidermis is avascular; nutrients diffuse from dermis.

• Dermis: Connective tissue layer beneath epidermis.

  • Papillary Layer: Superficial, loose connective tissue, forms dermal papillae.

  • Reticular Layer: Deeper, dense irregular connective tissue.

B. Skin Color and Accessory Structures

• Melanin: Pigment produced by melanocytes; determines skin color.

• Other Factors: Hemoglobin (redness), carotene (yellow-orange), and pathological conditions can affect skin color.

• Accessory Structures:

  • Hair: Produced by hair follicles; arrector pili muscle causes hair to stand.

  • Glands: Sebaceous (oil), sweat (eccrine and apocrine), and ceruminous (earwax) glands.

Bone Physiology

A. Types of Bone Tissue

• Spongy Bone: Porous, contains trabeculae; found at ends of long bones and inside flat bones.

• Compact Bone: Dense, forms outer layer of bones; provides strength.

B. Bone Structure

• Diaphysis: Shaft of a long bone.

• Epiphyses: Ends of a long bone.

• Diploë: Spongy bone in flat bones (e.g., skull).

• Osteon: Structural unit of compact bone; consists of concentric lamellae around a central canal.

C. Bone Formation (Ossification)

• Intramembranous Ossification: Bone develops from mesenchymal tissue; forms flat bones (e.g., skull, clavicle).

• Endochondral Ossification: Bone replaces hyaline cartilage; forms most bones of the body.

• Basic Steps: Cartilage model forms → cartilage calcifies → blood vessels invade → bone tissue replaces cartilage.

D. Bone Cell Types and Functions

• Osteoblasts: Build new bone matrix.

• Osteocytes: Mature bone cells, maintain bone tissue.

• Osteoclasts: Break down bone matrix.

E. Bone Remodeling and Growth

• Hormones: Parathyroid hormone (PTH), calcitonin, growth hormone, and sex hormones regulate bone growth and remodeling.

• Appositional Growth: Increase in bone diameter by adding new bone to the surface.

Skeletal System Basics

A. Function of the Skeleton

• Support for the body

• Protection of internal organs

• Movement (leverage for muscles)

• Mineral storage (calcium, phosphate)

• Blood cell production (hematopoiesis in red marrow)

B. Axial vs. Appendicular Skeleton

• Axial Skeleton: Skull, vertebral column, rib cage; supports and protects central axis of body.

• Appendicular Skeleton: Limbs and girdles (shoulder and pelvic); enables movement.

C. Vertebral Column Styles

• Cervical: 7 vertebrae in the neck.

• Thoracic: 12 vertebrae in the upper back.

• Lumbar: 5 vertebrae in the lower back.

• Sacrum and Coccyx: Fused vertebrae at the base of the spine.

D. Skull Bones

• Major Bones: Frontal, parietal, temporal, occipital, sphenoid, ethmoid.

• Facial Bones: Maxilla, mandible, zygomatic, nasal, etc.

E. Baby Skull Differences

• Fontanelles: Soft spots between cranial bones in infants, allow for growth and passage through birth canal.

• Bone Fusion: Bones fuse as child grows, forming sutures.

Additional info: Where the original notes were brief or listed only keywords, academic context and definitions have been added for clarity and completeness.