INTEGUMENTARY & SKELETAL
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