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60 Cards in this Set

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Functions of the Skeletal System and Bone Tissue
1. Support
2. Protection
3. Assistance in Movement
4. Mineral Homeostasis (calcium and phosphorous released into blood)
5. Blood Cell Production (red bone marrow)
6. Triglyceride storage (yellow bone marrow) - potential chemical energy reserve
Diaphysis
Bone's shaft or body
Epiphyses
Distal and proximal ends of the bone
Metaphyses
Regions in mature bone where diaphysis joins the epiphyses

Includes the epiphyseal plate and epiphyseal line
Epiphyseal Plate
Layer of hyaline cartilage in growing bone that allows diaphysis to grow in length
Epiphyseal Line
Hyaline cartilage of epiphyseal line replaced by bone

In mature bone
Articular Cartilage
Thin layer of hyaline cartilage covering the part of the epiphysis where bone forms joint

Decreases friction in joints
Periosteum
Layer of dense irregular connective tissue that covers the entire bone except articulating surfaces
Functions of Periosteum
1. Allows bone growth in diameter
2. Nourishes
3. Proects
4. Assists in fracture repair
5. Provides attachment points for ligaments and tendons
Medullary Cavity
Cavity inside diaphysis (a.k.a. marrow cavity)

Contains red marrow in children, yellow marrow in adults
Endosteum
Thin layer of connective tissue and bone-forming cells lining the medullary cavity
Calcification
Occurs in bone tissue extracellular matrix

Hydroxyapatite and other mineral salts form crystals in presence of collagen fibers
--Bone hardness from mineral salts
--Bone flexibility from collagen fibers
Osteogenic Cells
Bone tissue stem cells that develop into osteoblasts

Found along inner periosteum, in the endosteum, and bony canals with blood vessels
Osteoblasts
Bone-building cells that form the bone matrix and then become osteocytes
Osteocytes
Mature bone cells that maintain bone tissue

Maintain daily metabolism; exchange of nutrients and wastes
Osteoclasts
Large, multinucleated cells derived from numerous monocytes (type of white blood cell) that are responsible for resorption of bone

-located in endosteum
Resorption
Breakdown of bone extracellular matrix

Bone is constantly broken down and rebuilt
Compact Bone Tissue
Dense, solid-looking bone that forms superficial part of bones

80% of all bones in body
Osteons (Haversian Systems)
Basic units of functional bone; columns of bone tissue arranged parallel to long axis of bone
Perforating Canals
House blood vessels, lymphatic vessels, and nerves that run between the periosteum and central canal

Run perpendicular to bone surfaces
Central Canal
Runs parallel to bone surface, surrounded by concentric lamellae
Concentric Lamellae
Ring-like arrangement of bony matrix
Lacunae
Openings between concentric lamellae that house osteocytes
Canaliculi
Tiny canal through which osteocyte extensions from different lacunae connect to each other and to the central canal

Filled with extracellular fluid
Interstitial Lamellae
Remnants of broken down osteons located in the spaces between osteons
Circumferential Lamellae
Located just deep to the periosteum and encircling the medullary cavity
Spongy Bone
Makes up mose of short, flat, and irregular bones; also in epiphyses and around medullary cavity
Functions of Spongy Bone
1. Reduces weight of skeleton
2. Able to withstand stresses applied from many directions
3. Protect and support red marro (site of hemopoiesis)
Trabeculae
Thin beams of bone that make up spongy bone; contain lacunae with osteocytes and canaliculi, but NO OSTEONS
Arteries
Take blood to tissue; delivers nutrients, ions, and oxygen
Veins
Carry blood away the tissues; removes waste products and carbondioxide
Periostal Arteries
Supplies periosteum and superficial part of diaphysis
Nutrient Arteries
Supplies deeper parts of diaphysis and medullary cavity
Metaphyseal Arteries
Supply red bone marrow and metaphyses
Epiphyseal Arteries
Supply epiphyses
"Template" Skeleton
Embryonic skeleton

Consists of connective tissue membranes and hyaline cartilage
Ossification
or
Osteogenesis
The process by which bone forms
Intramembranous Ossification
Forms flat bones of skull and mandible; also hardens "soft spots" of fetal skull

1.Osteocytes form and matrix calcifies with arrival of minerals
2. Trabeculae develop and form spongy
3. Periosteum develops and compact bone replaces spongy bone at the surface
Endochondrial Ossification
Replacement of cartilage by bone; forms most bones in body

1. Starts with development of cartilage model from mesenchymal cells
2. Growth of cartilage model in length and width
3. Cartilage model becomes ossified resulting in epiphyses, diaphysis, and medullary cavity
Factors Affecting Bone Growth
1. Bone growth depends on adequate supply of minerals and vitamins
2. Bone growth depends on presence of hormones (growth hormones, thyroid hormones, and insulin)
3. Bone growth depends on presence of sex steroids (stimulate osteoblast activity)
Bone Remodeling
Bone is continuously broken down and renewed to allow bone to adjust to new stresses and to heal
Fracture
Any break in bone
Open (Compound) Fracture
Broken bone protrudes through skin
Closed (Simple) Fracture
Broken bone does not protrude through skin
Comminuted Fracture
Broken bone splinters and produces fragments
Greenstick Fracture
Shaft is not completely broken due to incomplete ossification
Impacted Fracture
One broken end is forcefully driven inside the other broken end
Pott's Fracture
At ankles, both tibia and fibula are involved
Colles' Fracture
Distal end of radius is displaced posteriorly
Stress Fractures
Minute tears in bone tissue due to repeated, strenuous activity
Repair of Bone Fractures
1. Formation of fracture hematoma
2. Formation of fibrocartilaginous callus
3. Formation of bony callus
4. Bone Remodeling
Bone's Role in Calcium Homeostasis
Stored calcium in bones may be liberated as needed to maintain calcium levels in blood, not health of skeleton
Cutaneous Membrane
Skin; covers the external surface of body; largest organ
Epidermis
Superficial part of skin; composed of keratinized stratified squamous epithelium
Dermis
Deep layer of skin; contains connective tissue
Hypodermis (Subcutaneous Layer)
Not technically part of skin; deep to dermis; anchors dermis to underlying tissues and organs; fat storage and large blood vessels
Keratinocytes
90% of skin cells; produce keratin
Melanocytes
8% of cells; produce melanin
Keratin
Tough, fibrous protein
Melanin
Absorbs UV; protects keratinocytes by transferring melanin to them