Key Terms and Concepts in Anatomy & Physiology: Tissues, Skin, and Skeletal System

Tissues and Cellular Structures

Connective Tissue

Connective tissue is one of the four basic types of tissue in the body, providing support, binding, and protection for organs.

• Adipose tissue: Specialized for fat storage and insulation.

• Areolar CT: Loose connective tissue that holds organs in place and attaches epithelial tissue to underlying tissues.

• Basement membrane: Thin, fibrous extracellular matrix separating epithelium from underlying tissue.

• Cartilage: Flexible connective tissue found in joints, ear, nose, and respiratory tract.

• Elastic cartilage: Cartilage with abundant elastic fibers, providing flexibility (e.g., external ear).

• Fibrocartilage: Cartilage with dense collagen fibers, found in intervertebral discs.

• Ground substance: Amorphous material in which connective tissue cells and fibers are embedded.

• Hyaline cartilage: Most common type, found in nose, trachea, and at the ends of long bones.

• Mesenchyme: Embryonic connective tissue from which all connective tissues develop.

• Reticular CT: Connective tissue with a network of reticular fibers, supporting lymphoid organs.

Muscle and Nervous Tissue

Muscle tissue is responsible for movement, while nervous tissue transmits electrical signals throughout the body.

• Muscle tissue: Includes skeletal, cardiac, and smooth muscle types.

• Nervous tissue: Composed of neurons and neuroglia, responsible for communication and control.

Epithelial Tissue

Epithelial tissue covers body surfaces, lines cavities, and forms glands.

• Simple epithelium: Single layer of cells, specialized for absorption and filtration.

• Stratified epithelium: Multiple layers, providing protection (e.g., skin).

• Transitional epithelium: Specialized for stretching, found in the urinary bladder.

• Pseudostratified ciliated epithelium: Appears layered but is a single layer with cilia, found in respiratory tract.

Integumentary System (Skin)

Layers and Structures of the Skin

The skin is the largest organ, consisting of multiple layers and specialized structures.

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

• Dermis: Middle layer, containing connective tissue, blood vessels, and nerves.

• Hypodermis: Subcutaneous layer, primarily adipose tissue.

• Papillary layer: Upper dermal layer with finger-like projections (dermal papillae).

• Reticular layer: Deeper dermal layer with dense irregular connective tissue.

Skin Appendages and Glands

• Hair follicle: Structure from which hair grows.

• Sebaceous glands: Produce sebum (oil) to lubricate skin and hair.

• Sudoriferous glands: Sweat glands, including eccrine (all over body) and apocrine (armpits, groin).

• Nail matrix: Region where nail growth occurs.

Skin Conditions and Healing

• Burns: Classified by degree (1st, 2nd, 3rd) based on depth and severity.

• Decubitus ulcer: Pressure sore caused by prolonged pressure on the skin.

• Basal cell carcinoma: Most common type of skin cancer, arising from basal cells.

• Melanoma: Dangerous skin cancer originating from melanocytes.

Skeletal System

Bone Structure and Types

Bones provide support, protection, and enable movement. They are classified by shape and structure.

• Compact bone: Dense outer layer providing strength.

• Spongy bone: Porous inner layer containing red marrow.

• Long bone: Longer than wide (e.g., femur, humerus).

• Short bone: Cube-shaped (e.g., carpals, tarsals).

• Flat bone: Thin and broad (e.g., skull, ribs).

• Irregular bone: Complex shapes (e.g., vertebrae).

Bone Cells and Growth

• Osteoblasts: Cells that build new bone.

• Osteoclasts: Cells that break down bone tissue.

• Osteocytes: Mature bone cells maintaining bone matrix.

• Endochondral ossification: Process by which bone forms from cartilage (most bones).

• Intramembranous ossification: Bone develops directly from mesenchyme (e.g., skull bones).

Bone Markings and Features

• Foramen: Opening in bone for nerves and blood vessels.

• Fossa: Shallow depression in bone.

• Condyle: Rounded articular projection.

• Process: Prominent projection on a bone.

Fractures and Healing

• Simple fracture: Bone breaks cleanly without piercing skin.

• Compound fracture: Bone breaks and pierces the skin.

• Comminuted fracture: Bone shatters into multiple pieces.

Additional Key Terms and Concepts

• Collagen: Main structural protein in connective tissues.

• Keratin: Protein in skin, hair, and nails providing strength and waterproofing.

• Melanin: Pigment produced by melanocytes, responsible for skin color.

• Fibroblasts: Cells that produce collagen and other fibers.

• Macrophages: Immune cells that engulf pathogens and debris.

• Lymphocytes: White blood cells involved in immune response.

Sample Table: Types of Cartilage

Type	Main Features	Location
Hyaline Cartilage	Most common, smooth matrix, few fibers	Nose, trachea, ends of long bones
Elastic Cartilage	Flexible, contains elastic fibers	External ear, epiglottis
Fibrocartilage	Dense collagen fibers, tough	Intervertebral discs, pubic symphysis

Sample Equation: Bone Growth Rate

The rate of bone growth can be expressed as:

$\text{Rate} = k[\text{Osteoblast Activity}]$

Additional info: This equation is a simplified representation; actual bone growth depends on multiple factors including hormones, nutrition, and mechanical stress.