INTEGUMENTARY & SKELETAL

Integumentary System (CH 6)

• Layers of the skin

  • Epidermis - surface of skin 

    • Stratum corneum - consists of up to 30 layers of dead, scaly,, keratinized cells, forms durable surface 

    • Stratum lucidum (THICK SKIN ONLY) - densely packed keratinocytes 

    • Stratum granulosum - three to five layers of keratinocytes - more in thick skin than thin

    • Stratum spinosum - several layers of keratinocytes, thickest stratum

    • Stratum basale - single layer of cuboidal to low columnar stem cells and keratinocytes resting on the basement membrane - stem cells

  • Dermis - connective tissue layer 

    • Papillary layer - areolar tissue in and near the dermal papillae, allows for mobility of leukocytes and other defenses against organisms introduced through breaks in the epidermis 

      • Blood vessels 

      • Upward waves - dermal papillae - cause fingerprints, handprints 

    • Reticular layer - deeper and ticker 

      • Dense irregular tissue 

      • Stretch marks 

  • Hypodermis - more areolar and adipose tissue (not considered real layer of skin)

• Pigments of skin and hair 

  • Melanin - produced by melanocytes and accumulates in the keratinocytes of the stratum basale and stratum spinosum 

    • Eumelanin - brownish black 

    • Pheomelanin - reddish, yellow

    • Hemoglobin - red 

    • Carotene - yellow 

• Structure of hair and follicle 

  • Hair divisible into 3 parts: 

    • Bulb - where hair growth originates 

      • Grows around bud of vascular connective tissue called the dermal papilla, sole source of nutrition 

      • Immediately above is the hair matrix, hair’s growth center 

    • Root - remainder of hair within follicle 

    • Shaft - portion above skin surface 

  • Hair into 3 parts:

    • Medulla - core of loosely arranged cells and air spaces - most prominent in thick hair 

    • Cortex - most of bulk of hair, consists of several layers of keratinized cells 

    • Cuticle - multiple layers of very thin, scaly cells that overlap each other like roof shingles 

• Types of skin cancer 

  • Basal cell carcinoma - most common type and least deadly

    • Seldom metastasis, rises from cells of stratum basale and eventually invades the dermis 

    • First appears as small, shiny bump

  • Squamous cell carcinoma

    • Arises from keratinocytes of stratum spinosum

    • Lesions commonly appear 

  • Melanoma - least common, most deadly

    • Arises from melanocytes

• Burns

  • First degree - epidermis

    • marked by redness, slight edema, and pain

    • heal in a few days 

  • Second degree - epidermis and part of the dermis

    • Partial thickness burns 

    • Tan, white

    • Blistered and very painful 

    • May take weeks to months to heal and may leave scars 

  • Third degree - epidermis, all of dermis, and deeper tissue 

    • No dermis remains,so skin can only regenerate from edges of the wound

    • Often require skin grafts 

• Nails

  • Nail plate - hard part of nail 

  • Free edge - part hanging off of nail 

  • Nail root - extends proximally under the overlying skin 

  • Nail fold - surrounding skin rises a bit above the nail

  • Nail groove - separates from margin of nail plate and nail fold 

  • hyponychium - epidermis under nail bed

  • Nail matrix - stratum basale thickens into growth zone 

  • Lunule - white crescent 

  • Cuticle - narrow zone of dead skin 

Skeletal System

• Structure

  • Outer shell consists of compact bone 

  • Outer shell encases marrow cavity, contains bone marrow (also called medullary cavity)

  • Spongy bone found at the ends of the bone of its central space 

  • Long bone

    • Diaphysis - shaft, provides leverage 

    • Epiphysis - expanded head at each end, strengthen the joint, adds surface area for attachment of tendons and ligaments 

  • Periosteum - sheath that covers the bone 

  • Endosteum - thin layer of reticular connective tissue that lines the internal marrow cavity 

  • Children and adolescents have an epiphyseal plate of  hyaline cartilage separates the marrow spaces of epiphysis and diaphysis

    • Appears as narrow line at end of long bone 

    • Zone where bones grow in length

  • Adults don’t have an epiphyseal plate bc their bones don’t grow any more, however they do have an epiphyseal line to mark where the plate used to be 

• Types 

  • Short - kind of looks like a square (ie patella)

  • Long - length longer than width (ie femur)

  • Irregular - random shape (ie vertebrae and ear bones)

  • Spongy bone - calcified and hard, has many spaces filled with marrow 

  • Bone marrow - soft tissue that occupies marrow cavity of a long bone 

    • Child - red bone marrow - produces RBC

    • Adults - yellow bone marrow - no longer produces blood, although in the event of tsever or chronic anemia, it can transform back into red marrow and resume its hematopoietic function 

• Cell types 

  • Osteogenic - stem cells

  • Osteoblast -bone forming cells 

  • Osteocytes - former osteoblasts become trapped in the matrix they deposited, reside in tiny cavities called lacunae 

    • reabsorbs  bone matrix and others depositi it, contribute to homeostatic maintenance of both bone density and blood concentrations of calcium and phosphate ions 

  • Osteoclasts - bone dissolving cells on the bone surfaces, deveo from the same bone marrow stem cells that give rise to the blood cells 

• Bone development 

  • Intramembranous ossification 

    • Mesenchymal cells line up along blood vessels, become osteoblasts, and secrete soft collagenous osteoid tissue 

    • Calcium phosphate and other minerals crystallize on the collagen fibers of the osteoid tissue and harden the matrix 

    • Forging process continues, becomes perisoterijm 

    • Blood vessels crowd the area, creating red bone marrow

  • Endochondral ossification

    • Mesenchymal cells differentiate into chondrocytes

    • Cartilage model of future bony skeleton and the perichondrium form

    • Capillaries prevent cartilage Perichondrium transforms into periosteum. Periosteal collar develops. Primary ossification center develops

    • Cartilage and chondrocytes continue to grow at ends of the bone

    • Secondary ossification centers develop

    • Cartilage remains at epiphyseal (growth) plate and at joint surface as articular cartilage