T2 240 know this STUDY GUIDE

Functions of the Skin

• Protection

  • Acts as a barrier against pathogens, UV radiation, and harmful chemicals.

• Sensation

  • Contains sensory receptors for touch, temperature, and pain.

• Thermoregulation

  • Regulates body temperature through sweating and blood vessel dilation/constriction.

• Excretion

  • Removes waste products through sweat.

• Vitamin D Synthesis

  • Produces vitamin D when exposed to sunlight.

• Water Resistance

  • Prevents excessive water loss.

Types of Skin Glands and Their Secretions

• Sebaceous (Oil) Glands

  • Secrete sebum to lubricate and protect skin and hair.

• Eccrine Sweat Glands

  • Secrete watery sweat for cooling the body.

• Apocrine Sweat Glands

  • Found in armpits and groin; secrete milky sweat activated by stress.

Changes in Sweat Gland Function with Age

• Infants/Young Children

  • Immature sweat glands; less effective at regulating temperature.

• Adolescents

  • Apocrine glands become active during puberty.

• Elderly

  • Reduced sweat gland function; less effective cooling and drier skin.

Major Layers of Skin

1. Epidermis

   • Outermost layer containing:

     • Keratinocytes: Produce keratin for waterproofing.

     • Melanocytes: Produce melanin for pigmentation.

     • Langerhans Cells: Immune system defense.

2. Dermis

   • Middle layer containing:

     • Blood vessels, nerves, hair follicles, sebaceous glands, and sweat glands.

3. Hypodermis (Subcutaneous Layer)

   • Deepest layer containing:

     • Fat cells for insulation and shock absorption.

Life Cycle of an Epidermis Cell

• Stratum Basale

  • Cells divide and begin keratinization.

• Stratum Spinosum

  • Cells mature and develop keratin.

• Stratum Granulosum

  • Keratinocytes die and fill with keratin.

• Stratum Corneum

  • Dead cells are shed off the surface.

Roles of Keratin and Melanin

• Keratin

  • Provides strength, waterproofing, and protection.

• Melanin

  • Protects against UV radiation and gives skin color.

Key Structures in the Skin

• Melanocytes

  • Produce melanin.

• Langerhans Cells

  • Immune defense in the epidermis.

• Keratinocytes

  • Form the protective outer layer.

• Arrector Pili

  • Muscles that cause hair to stand on end.

• Stretch Marks

  • Result from overstretched skin fibers.

Bone Structure and Function

Parts and Layers of Bone

• Periosteum

  • Outer fibrous layer that nourishes bone.

• Compact Bone

  • Dense outer layer that provides strength.

• Spongy Bone

  • Porous inner layer that reduces bone weight.

• Medullary Cavity

  • Contains bone marrow for blood cell production.

• Epiphysis

  • End of the bone containing spongy bone.

• Diaphysis

  • Shaft of the bone containing compact bone.

Bone Remodeling and Calcium Regulation

• Osteoclasts

  • Break down bone to release calcium.

• Osteoblasts

  • Build new bone.

• Parathyroid Hormone (PTH)

  • Increases blood calcium by stimulating osteoclasts.

• Calcitonin

  • Decreases blood calcium by promoting calcium storage in bones.

Types of Bone Cells

• Chondrocytes

  • Produce cartilage.

• Osteocytes

  • Mature bone cells that maintain bone.

• Osteoblasts

  • Build bone.

• Osteoclasts

  • Break down bone.

Functions of Bone

• Support

• Protection

• Movement

• Blood Cell Production

• Mineral Storage

Comparison of Compact vs. Spongy Bone

• Compact Bone

  • Dense and strong; found in the outer layer of bones.

• Spongy Bone

  • Lighter and porous; found at bone ends.

Axial and Appendicular Skeleton

Axial Skeleton Bones

• Skull

• Vertebral column

• Ribs

• Sternum

Appendicular Skeleton Bones

• Shoulder girdle

• Pelvic girdle

• Arms

• Legs

Upper and Lower Extremities

• Upper Extremities Bones:

  • Humerus, radius, ulna, carpals, metacarpals, and phalanges.

• Lower Extremities Bones:

  • Femur, tibia, fibula, tarsals, metatarsals, and phalanges.

Bone Orientation in Anatomical Position

• Lateral Bones:

  • Radius, fibula, scapula.

• Medial Bones:

  • Ulna, tibia, sternum.

Joint Movement Terminology

• Flexion

  • Decreasing the angle between joints.

• Extension

  • Increasing the angle between joints.

• Abduction

  • Moving away from the body midline.

• Adduction

  • Moving toward the body midline.

• Rotation

  • Circular motion around an axis.

• Circumduction

  • Cone-shaped circular movement.

• Inversion

  • Turning the sole inward.

• Eversion

  • Turning the sole outward.

• Pronation

  • Palm down.

• Supination

  • Palm up.

• Plantar Flexion

  • Pointing toes downward.

• Dorsal Flexion

  • Lifting toes upward.

Joints Structure and Movements

• Ball-and-Socket Joint

  • Shoulder and hip; allows rotation and circumduction.

• Hinge Joint

  • Elbow and knee; allows flexion and extension.

• Pivot Joint

  • Neck; allows rotation.

Spinal Abnormalities and Curvatures

• Kyphosis

  • Excessive outward curve of the thoracic spine.

• Lordosis

  • Excessive inward curve of the lumbar spine.

• Scoliosis

  • Abnormal lateral curve.

• Primary Curvatures

  • Thoracic and sacral; present at birth.

• Secondary Curvatures

  • Cervical and lumbar; develop later.

Epiphyseal Plate

• Growth plate located at the ends of long bones, responsible for lengthwise growth.

Terminology Related to Bone Structure

• Condyle

  • Rounded projection for joint articulation.

• Spine

  • Sharp, pointed projection.

• Articulation

  • Joint where bones meet.

• Meatus

  • Canal-like passageway.

• Foramen

  • Opening for nerves and blood vessels.

• Fossa

  • Shallow depression.

• Ramus

  • Arm-like projection.

• Sinus

  • Air-filled cavity.

• Tuberosity

  • Large rounded projection.

• Process

  • Any bony projection.

Frequently Broken Bones

• Distal radius (common in adults)

• Clavicle (common in children)

Opposing Joint Movements

• Flexion ↔ Extension

• Abduction ↔ Adduction

• Pronation ↔ Supination

• Inversion ↔ Eversion

• Plantar Flexion ↔ Dorsal Flexion