Chapter 6- Bones & Bone Tissue Flashcards
The functions of the skeletal system
The functions of the skeletal system
- Support -maintain shape
- Protection- internal organs
- System of levers for movement (muscles “pull” against bone for movement)
- Hematopoiesis -production of blood cells,
- Fat storage-in adults
- Mineral storage- calcium ions & phosphate
- Acid-basic homeostasis
5 Bone Shapes
- Flat Bone: any bone that is broad, flat, & thin
Example: Sternum, Scapula, Cranial, rib - Long Bone: longer than it is wide
Example: humerus, tibia, Ulna, Clavicle, Metatarsal, Femur - Short Bone: about as wide as it is long
Example: carpal, metacarpal,
-Sesamoid Bones: round, flat & found encased within tendon.
Example: patella
- Irregular Bones: any bone that do not fall within any of the pervious categories
Example: sacrum, vertebra
Periosteum
composed of dense irregular collagenous connective tissue that is richly supplied with a lot of blood vessels & nerves
Diaphysis
the shaft of a long bone, marrow cavity
Epiphyses
the end of a long bone
Articular cartilage
the epiphyses (end of long bones) are covered w/ a thin layer of hyaline cartilage, which allow bones to rub together with reduced friction at joints
Marrow (medullary) cavity
the largely hollow interior portion of the diaphysis of a long bone
Compact bone
the hard, dense outer bone, composed of repeating units called osteons; provides weight-bearing strength
Spongy bone(cancellous)
inner, honeycomb-like bone, forms a framework of bony struts that allows it to resist forces in many directions & provides a place for the bone marrow to reside
Endosteum
thin vascular membrane; inner surfaces of spongy bone
Epiphyseal plates (growth plates)
a line of hyaline cartilage from which a long bone grows in length in children & adolescents
Epiphyseal lines
once adulthood is reached; the cartilage is replaced by osseous tissue. Once the epiphyseal plates “close”, the long bone can no longer grow in length
The purpose of red marrow…
responsible for producing blood cells; infants & young children contain mostly red bone marrow b/c their rapid rate of growth requires a constant supply of new blood cells.
- Children: red marrow everywhere
- Adults: Red marrow remains only in the bones of the pelvis, proximal femur, humerus, vertebrae, ribs, sternum, clavicle, & scapulae
The purpose of yellow marrow…
responsible for storing triglycerides; at about age 5 yellow marrow begins to replace some of the red bone marrow. By adulthood, most bone marrow in the body is yellow
General structure of other bone shapes (compact bone and diploe)
“sandwich” made of two thin layers of compact bone and a middle layer of spongy bone housing bone marrow.
-Dipole: the spongy bone in flat bones
Nutrient Arteries
bloods enter the bone via a small hole in the diaphysis
Periosteum
supplies bone with blood vessels & sensory nerve fibers
Components of bone
organic matrix, inorganic matrix, collagen fibers and bone cells (all three)
Organic matrix
ECM ingredients; collagen fibers, proteoglycans, glycoproteins, & bone specific proteins (holds water)
Inorganic Matrix
minerals; mainly calcium phosphate salts (calcium ions, phosphorus, bicarbonate, potassium, magnesium, sodium salts)
Bone cells
three types of cells; osteoblast (builds bone/immmature bone), osteocytes (mature bone), Osteoclast (breakdown bone)
Osteogenic cells
stem cells that make osteoblasts & osteocytes (lacunae)
Macrophages
(immune cell) produce osteoclasts (acid & enzymes)
Ossification
the process of bone formation
-Bone formation begins at about 6 weeks of fetal development
Intramembranous ossification (membrane bone)
(membrane bone) bones build on starting material known as a model that is made of a membrane of embryonic connective tissue
Examples: skull & clavicle (flat bones)
Steps:
- Ossification centers- formation of primary woven between membranes
- Periosteum forms
- Formation of Compact bone plates
- New woven bone matures to spongy bone
Endochondral Ossification (cartilage bone)
(cartilage bone) bones build on a model made of hyaline cartilage; this results in a growth plate
o Examples: all the bones in the body below the head, except the clavicles
o Steps:
1. hyaline cartilage model is formed
2. bone collar & periosteum are formed around the shaft of the model
3. the primary ossification center is formed in the center of the diaphysis
4. the diaphysis is remodeled & the II ossification of epiphyses begins
5. the only cartilage remains at the articular surfaces & at the epiphyseal plate
Appositional Growth
growth in bone width
Interstitial Growth
increase in bone length; inside the tissue
Epiphyseal plate growth
Epiphyeal plate growth:
- Chondrocytes replicate & enlarge (more cells make more matrix)
- Cartilage plate grows, increasing bone length
- Cartilage dies & is replaced by bone
- Epiphyseal plate remains same size, while bone grows
Growth in Bone Length
Growth in Bone Length: structure of the epiphyseal plate
- Zone of reserve cartilage; resting zone (G0)
- Zone of proliferation; actively dividing
- Zone of hypertrophy & maturation; too little oxygen (start to die)
- Zone of calcification; dead chondrocytes
- Zone of ossification; bone cells moved in & made bone
Growth Hormone (GH)
produced by the anterior pituitary, an endocrine gland below the brain. Enhances protein synthesis and cell division. Infancy & childhood
- Increase rate of mitosis, promoting longitudinal growth
- Increases activity of osteogenic cells including their activity in the zone of ossification
- Direct stimulation of osteoblasts in periosteum, triggering appositional growth
Testosterone
male sex hormone
- Increase appositional growth (thinker)& great calcium salt deposits
- Increase rate of mitosis at the epiphyseal plate–>“growth spurts”
- Accelerates the closure of the epiphyseal plates
Estrogen
female sex hormone
- Increases rate of longitudinal bone growth & inhibits osteoclasts–>”growth spurt”
- Increase mitosis & osteogenesis
- Accelerates closure of epiphyseal plates, more potent effect –>women are shorter
Bone Remodeling
the continual process of bone growth & bone loss that takes place within healthy bone. Gives you mature bone.
- Causes: Stress (amount of compression), Tension (stretching force), Pressure (continuous downward force)
- Factors: stress, damage, nutrition, hormones, age
Bone Repair
replacement of primary bone with secondary bone
-Causes: damage
Parathyroid Hormone (PTH)
increases calcium ion level in blood
Calcitonin
produced by the cells of the thyroid gland, located in the anterior neck. Decrease blood calcium ion concentration by stimulating osteoblasts to build bone.
Triggers negative feedback loop when there is an increase in the number of calcium ions
