Skin and Bones: Study Guide for the Integumentary and Skeletal Systems

Chapter 5: The Integumentary System

Skin Structure and Function

The skin is the largest organ of the body and serves multiple protective and regulatory functions. It consists of two main layers: the epidermis and the dermis.

• Accomplishments of Skin: The skin protects against mechanical injury, pathogens, and dehydration; regulates temperature; enables sensation; and synthesizes vitamin D.

• Major Types of Skin Cancer:

  • Basal cell carcinoma: Most common, arises from basal cells in the epidermis.

  • Squamous cell carcinoma: Originates from keratinocytes of the stratum spinosum.

  • Melanoma: Most dangerous, arises from melanocytes.

• Burn Severity:

  • First-degree burns: Affect only the epidermis; cause redness and pain.

  • Second-degree burns: Involve epidermis and part of dermis; cause blistering.

  • Third-degree burns: Destroy both epidermis and dermis; may affect deeper tissues; skin appears white, charred, or leathery.

  Serious burns are life-threatening due to fluid loss, infection risk, and temperature regulation failure.

• Rule of Nines: Used to estimate the extent of burns by dividing the body into regions representing 9% (or multiples) of total body surface area.

Example: A burn covering the entire right arm and anterior trunk would be approximately 9% + 18% = 27% of body surface area.

Chapter 6: Bones and Skeletal Tissues

Bone Classification and Structure

Bones are classified by shape and structure, and they perform vital functions such as support, protection, movement, mineral storage, and blood cell formation.

• Four Bone Classes:

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

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

  • Flat bones: Thin, flattened, and usually curved (e.g., sternum, skull).

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

• Seven Important Functions of Bones:

  1. Support

  2. Protection

  3. Movement

  4. Mineral storage (calcium, phosphate)

  5. Blood cell formation (hematopoiesis)

  6. Triglyceride (fat) storage

  7. Hormone production (osteocalcin)

• Gross Anatomy of Long Bone vs. Flat Bone:

  • Long bone: Diaphysis (shaft), epiphyses (ends), medullary cavity, periosteum, endosteum.

  • Flat bone: Thin layers of compact bone surrounding a spongy bone center (diploë), no shaft or epiphyses.

Bone Formation and Growth

Bones develop through two main processes: intramembranous ossification and endochondral ossification. Growth and remodeling are regulated by hormones and mechanical stress.

• Intramembranous Ossification: Bone develops from a fibrous membrane; forms flat bones (e.g., skull, clavicle).

• Endochondral Ossification: Bone forms by replacing hyaline cartilage; forms most bones of the skeleton.

• Bone Growth and Remodeling:

  • Growth occurs at the epiphyseal plate in long bones during childhood and adolescence.

  • Remodeling is a lifelong process involving bone resorption and deposition.

  • Hormones (growth hormone, sex hormones) and physical stress (exercise) regulate bone remodeling.

Example: Weight-bearing exercise stimulates bone formation by increasing osteoblast activity.

Summary Table: Bone Classes and Examples

Bone Class	Shape	Example
Long	Longer than wide	Femur, Humerus
Short	Cube-shaped	Carpals, Tarsals
Flat	Thin, flattened	Sternum, Skull
Irregular	Complex shape	Vertebrae, Pelvis

Key Equations

• Bone Remodeling Equation:

$\text{Bone Mass} = \text{Bone Formation} - \text{Bone Resorption}$

Additional info: Bone remodeling is influenced by mechanical stress (Wolff's Law) and hormonal signals such as parathyroid hormone and calcitonin.