Study Guide: Skin Model, Rule of Nines, and Bones/Bone Parts

Skin Model

Overview of the Skin

The skin is the largest organ of the human body and serves as a protective barrier. It is composed of multiple layers, each with distinct functions.

• Epidermis: The outermost layer, primarily made of keratinized stratified squamous epithelium. Provides waterproofing and protection.

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

• Hypodermis (Subcutaneous Layer): The deepest layer, consisting mainly of adipose tissue for insulation and energy storage.

Key Functions:

• Protection against pathogens, chemicals, and physical injury

• Regulation of body temperature

• Sensation (touch, pain, temperature)

• Vitamin D synthesis

Example: The skin model in laboratory settings typically highlights the layers, glands (sebaceous and sweat), hair follicles, and sensory receptors.

Rule of Nines

Assessment of Burn Surface Area

The Rule of Nines is a clinical tool used to estimate the total body surface area (TBSA) affected by burns in adults. The body is divided into regions, each representing approximately 9% (or multiples thereof) of the total body surface area.

• Head and Neck: 9%

• Each Upper Limb: 9% (total 18%)

• Each Lower Limb: 18% (total 36%)

• Anterior Trunk: 18%

• Posterior Trunk: 18%

• Perineum (Genital Area): 1%

Formula:

$\text{Total Burn Surface Area (TBSA)} = \sum \text{(Percentage of each affected region)}$

Example: If a patient has burns on the entire left arm and anterior trunk, the TBSA affected is 9% (arm) + 18% (anterior trunk) = 27%.

Bones and Bone Parts

Overview of the Human Skeleton

The human skeleton consists of 206 bones in the adult body, providing structure, protection, and facilitating movement. Students are often required to identify major bones and their parts.

• Axial Skeleton: Includes the skull, vertebral column, and thoracic cage (ribs and sternum).

• Appendicular Skeleton: Includes the bones of the limbs, pectoral girdle, and pelvic girdle.

Key Bone Parts to Study:

• Skull: Frontal bone, parietal bone, occipital bone, temporal bone, mandible, maxilla, zygomatic bone, etc.

• Vertebral Column: Cervical, thoracic, lumbar vertebrae, sacrum, coccyx

• Thoracic Cage: Sternum, ribs

• Upper Limb: Humerus, radius, ulna, carpals, metacarpals, phalanges

• Lower Limb: Femur, tibia, fibula, tarsals, metatarsals, phalanges

• Pelvic Girdle: Ilium, ischium, pubis

Example: The humerus is the bone of the upper arm, articulating proximally with the scapula at the shoulder and distally with the radius and ulna at the elbow.

Additional info: Students are advised to study a comprehensive list of 150 bones/bone parts, as provided in their lab manual, and to utilize physical models for hands-on learning.

Sample Table: Major Bones and Their Classification

Bone	Location	Classification
Femur	Thigh	Long bone
Parietal	Skull	Flat bone
Vertebra	Spine	Irregular bone
Carpal	Wrist	Short bone

Additional info: Classification of bones is based on shape: long, short, flat, and irregular.