Skin is the largest organ in the body.

Thick skin - palmar and plantar

Thin skin - eyelids

Main function of skin - synthesize vitamin D

Epidermis - keratinized stratified squamous

Dermis - dense fibrous irregular (collagen)

Hypodermis - adipose and areolar tissue

Epidermal cell types - keratinocytes, melanocytes, Langerhans cells

Keratinocytes - tough keratin (90% of cells)

Melanocytes - skin color; filter UV rays

Langerhans Cells - skin immunity

Stratum Corneum - most superficial; desmosomes

Hyperkeratosis - callous’

Stratum Lucidum - absent in thin skin; ELEIDEN (soft gel; makes fingertips puffy)

Stratum Granulosum - degeneration; keratinization begins

Stratum Spinosum - rich in RNA

Stratum Basale - mitosis

Stratum Germinativum - growth

Regeneration of epidermis takes 35 days; process can be sped up by scraping

Blisters - destruction of epidermal desmosomes

Dermis - thicker than the epidermis

Main functions of dermis - hair follicles, sweat glands, sebaceous glands, and blood vessels

Layers of dermis - Papillary and Reticular

Papillary - fingerprints; GRIPPING

Reticular - goosebump layer/muscle

Fibroblast - build fiber

Keloid - thickened scar

Most common skin cancer is malignant melanoma

UV radiation - damages DNA → mitotic division → cancer

Skin color - melanocytes; tyrosinase converts into melanin

Pale skin - constriction of blood vessels

Blush skin - dilation of blood vessels

Cyanosis - bluish skin

Vitiligo - pigmentation missing in patches

Surface film - residue from sweat glands; blocks toxins/antibacterial

Langer lines - surgery lines

Hypothalamus - regulates body temperature

Heat produced by the metabolism of food (calories)

Lanugo hair - covers fetus but sheds before birth; common in premature babies

Hair grows about 1/2 inch per month

Germinal matrix - growth point for hair and nails

Lunula - white at the base of nail

Sweat gland - sudiferous gland

Eccrine - sweat glands

Apocrine - smell & bacteria glands

Bacteria - strep, staph, impetigo, boils

Virus - warts

Fungal - tinea

Tinea pedis - athletes foot

Tinea corporis - ringworm

Tinea cruris - jock itch

Articulations - joints

Long bone - femur and humerus

Short bone - phalanges

Flat bone - cranium, sternum, scapula

Irregular - vertebrae, pelvis

Seismoid - patella

Diaphysis - shaft of long bone

Epiphysis - ends of long bone (bone marrow)

Endosteum - lining of medullary cavity

Epiphyseal plate - growth plate

Articular cartilage - hyaline at joints

Periosteum - covers the long bone

Medullary cavity - hollow space in diaphysis

Compact bone - osteons (haversian canals) - run lengthwise to deliver and remove

Lamella - concentric, calcified layers

Lacunae - fluid and osteocytes

Canaliculi - ultra small canals connecting lacunae to haversian, blood and lymph

Volkmann’s canal - transverse to exterior surface

Cancellous bone - areas of increased strength (epiphysis)

Osteocyte - mature bone cells

Osteoblast - build bone

Osteoclasts - break down bone

Osteogenic cells - stem cells

Bone marrow - myeloid tissue; RBC production

Bones store 98% of body’s calcium

Osteoblast remove calcium from blood to build bone

Osteoclast release calcium into blood

Calcium is needed for skeletal and cardiac muscle contraction, nerve impulses, and blood clotting

Osteogenesis - creation of bone

Intramembranous ossification - form bones from membranes

Appositional growth - layering of osseous tissue to outer surface

Endochondral - bone forms from cartilage