Key Terms and Concepts in Anatomy & Physiology: Integumentary and Skeletal Systems

Integumentary System

Overview of the Integumentary System

The integumentary system is composed of the skin and its associated structures, including hair, nails, and glands. It serves as the body's first line of defense and plays a vital role in protection, sensation, thermoregulation, and synthesis of vitamin D.

• Skin: The largest organ of the body, consisting of the epidermis and dermis.

• Accessory structures: Includes hair, nails, sebaceous (oil) glands, and sweat glands.

• Functions: Protection, temperature regulation, excretion, sensation, and vitamin D production.

Skin Structure

• Epidermis: The outermost layer of skin, composed mainly of keratinized stratified squamous epithelium.

• Dermis: The deeper layer of skin, containing connective tissue, blood vessels, nerves, hair follicles, and glands.

• Hypodermis (subcutaneous layer): Lies beneath the dermis, primarily composed of adipose tissue and areolar connective tissue.

Cells of the Epidermis

• Keratinocytes: Produce keratin, a protein that provides strength and waterproofing.

• Melanocytes: Produce melanin, the pigment responsible for skin color.

• Langerhans cells: Immune cells involved in defense against pathogens.

• Merkel cells: Sensory receptors for touch.

Skin Glands

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

• Sudoriferous (sweat) glands: Include eccrine glands (thermoregulation) and apocrine glands (associated with hair follicles in specific regions).

• Ceruminous glands: Produce earwax in the external ear canal.

Hair and Nails

• Hair follicle: The structure from which hair grows.

• Hair shaft: The visible part of the hair above the skin surface.

• Nail matrix: The region of the nail bed responsible for nail growth.

• Nail plate: The hard, keratinized portion of the nail.

Skin Disorders and Injuries

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

• Decubitus ulcer: Also known as a pressure sore or bedsore, caused by prolonged pressure on the skin.

• Basal cell carcinoma: The most common type of skin cancer, arising from basal cells in the epidermis.

• Melanoma: A dangerous form of skin cancer originating from melanocytes.

Connective Tissue

Types of Connective Tissue

Connective tissue supports, binds, and protects other tissues and organs. It is classified based on its composition and function.

• Loose connective tissue: Includes areolar, adipose, and reticular tissues.

• Dense connective tissue: Includes dense regular, dense irregular, and elastic tissues.

• Cartilage: Hyaline, elastic, and fibrocartilage.

• Bone: Compact and spongy bone.

• Blood: A fluid connective tissue.

Components of Connective Tissue

• Cells: Fibroblasts, adipocytes, chondrocytes, osteocytes, and others.

• Fibers: Collagen (strength), elastic (flexibility), and reticular (support).

• Ground substance: The non-cellular material in which the cells and fibers are embedded.

Skeletal System

Overview of the Skeletal System

The skeletal system provides structural support, protection for internal organs, facilitates movement, stores minerals, and houses bone marrow for blood cell production.

• Bone types: Long, short, flat, irregular, and sesamoid bones.

• Major functions: Support, protection, movement, mineral storage, blood cell formation (hematopoiesis).

Bone Structure

• Compact bone: Dense outer layer providing strength.

• Spongy bone: Lighter, porous inner layer containing red bone marrow.

• Periosteum: The outer fibrous covering of bone.

• Endosteum: The lining of the medullary cavity.

• Epiphyseal plate: The growth plate in long bones.

Bone Cells

• Osteoblasts: Bone-forming cells.

• Osteocytes: Mature bone cells maintaining bone tissue.

• Osteoclasts: Bone-resorbing cells.

Bone Formation and Growth

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

• Endochondral ossification: Bone forms by replacing hyaline cartilage (e.g., long bones).

Bone Fractures

• Simple (closed) fracture: Bone breaks but does not penetrate the skin.

• Compound (open) fracture: Bone breaks and pierces the skin.

• Greenstick fracture: Incomplete fracture, common in children.

• Comminuted fracture: Bone shatters into multiple pieces.

Bone Markings

• Foramen: A hole through which blood vessels or nerves pass.

• Fossa: A shallow depression in bone.

• Process: A projection or bump on a bone.

• Tuberosity: A large, rounded projection.

Selected Key Terms Table

The following table summarizes some of the key terms and their definitions relevant to the integumentary and skeletal systems:

Term	Definition
Adipose	Connective tissue specialized for fat storage.
Basement membrane	Thin layer of extracellular matrix separating epithelium from underlying tissue.
Collagen	Main structural protein in connective tissues, providing strength and flexibility.
Osteoblast	Cell responsible for bone formation.
Osteoclast	Cell that breaks down bone tissue.
Osteocyte	Mature bone cell that maintains bone tissue.
Epiphyseal plate	Growth plate in long bones where new bone is produced during childhood and adolescence.
Hyaline cartilage	Most common type of cartilage, found on articular surfaces of bones.
Melanin	Pigment produced by melanocytes, responsible for skin color.
Keratin	Fibrous protein that provides strength and waterproofing to skin, hair, and nails.

Additional info:

• Some terms (e.g., "apocrine glands", "eccrine glands", "osteon", "lamellae") are included based on standard Anatomy & Physiology curricula, as the original list is a glossary of key terms for exam preparation.

• Definitions and explanations have been expanded for clarity and completeness.