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Ch. 6 bones
Bone and skeletal tissues
| Question | Answer |
|---|---|
| 3 types of cartilage in skeletal tissue | 1.Hyaline 2.Elastic 3.Fibrocartilage |
| Hyaline cartilage and skeletal tissue | Found at the end of long joints (ex. ribcage, nose, and trachea); extremely abundant; flexible but firm and sturdy; decreases friction |
| Elastic cartilage and skeletal tissue | More flexible than hyaline due to more elastic fibers and less collagen; able to withstand stretching; found in epiglottis |
| Fibrocartilage and skeletal tissue | Found in vertebral pads and pubic symphasis; compressible due to high tensile strength; a good example is also the meniscus (pad in the knee) lays on top of the tibia and withstands compression from femur |
| Cartilage growth | 1.Appositional growth 2.Interstitial growth |
| Appositional growth | "outside"; most common/abundant growth; Cartilage forming cells (chondroblasts) secrete new matrix on external surface |
| Interstitial growth | "within"; lacunae chondrocytes proliferate/secrete matrix inside cartilage; Very slow type of growth |
| 5 Vital functions of bone | 1.Support- supports organs (structural) 2.Protection- skull, spinal chord, ribcage 3.Movement- levers (muscle attachments) 4.Mineral storage- release and store calcium and phosphate 5.Blood cell formation- hematopoiesis within marrow cavities |
| 2 Regions of skeletal bones | 1.Axial 2.Appendicular |
| Axial skeleton | long axis; skull, vertebral column |
| Appendicular skeleton | upper and lower limbs; girdles; pelvic girdle, leg bones, carpals, ect. |
| 4 Bone shapes | 1.Long bones 2.Short bones 3.Flat bones 4.Irregular bones |
| Long bones | longer than they are wide; ex. femur |
| Short bones | cube-shaped; ex. bones in wrist and ankle; alson bones within tendons like the patella |
| Flat bones | Thin and flattened; usually a bit curved; ex. sternum, skull bones, rib bones |
| Irregular bones | Bones with complicated and abnormal shapes; ex. hip bones, vertebra |
| Bones adapt to form... | landmarks consistent with their use (bulges, depressions, and holes) |
| Landmarks of bone | (bulges, depressions, and holes) Serve as sites of attachment for muscles, ligaments and tendons; form joint surfaces (ball and socket); conduits for blood vessels and nerves (holes) |
| 2 Types of bone | 1.Compact bone 2.Spongy bone |
| Compact bone | usually on outer surface of bones; smooth and solid; formed by collagen that has been mineralized |
| Spongy bone (anatomy) | pours bone found inside bones or in between compact bone; looks like a sponge; never found by itself but will always be incased by compact bone; is made up of "struts" of bone |
| Spongy bone (functions/physiology) | Not soft; struts distribute (or spread out) stress over a surface of compact bone which helps keep the stress off one small area; bone marrow is found within the spongy bone |
| Anatomy of long bones | Head- proximal epiphysis which contains spongy and compact bone, there is also an epiphysis at the opposite end of the bone Shaft- diaphysis which contains only compact bone (2-epiphyses 1-diaphysis) |
| Diaphysis | Hollow/tubular shaft that forms the axis of long bones; composed of compact bone that surrounds medullary cavity; yellow bone marrow (fat) is contained in the medullary cavity |
| Medullary Cavity | Hollow tube in the center of the long bones that houses yellow marrow |
| Epiphyses | Expanded ends of long bones; exterior is compact bone and interior is spongy bone; Joint surface is covered with articular (hyaline) cartilage |
| epiphyseal line | Old (closed) growth plate; Growth plates seal as we age; defines (or divides) epiphyses from diaphysis |
| Articular (hyaline) cartilage in joints | left over from embryo |
| 2 Layers of connective tissue in long bones | 1.Endosteum 2.Periosteum |
| Endosteum | Inside the bone shaft; lines the medullary cavity and surrounds bone marrow; next to bone cells |
| Periosteum | Around the bone; contains perforating (Sharpey's) fibers that connect the tissue to the bone; double-layered protective membrane (outer and inner layer); contains rich supply of nerves and blood vessels |
| Outer layer of periosteum | Dense irregular tissue |
| Inner layer of periosteum | Osteoclasts and osteoblasts |
| 4 Types of bone cells | 1.Osteogenic cell- stem cell 2.Osteoblast- bone growth, building 3.Osteocyte- maintains bone, repairs 4.Osteoclast- bone-resorbing cells that use enzymes and acid to break down bone cells; breaks down bone |
| Osteons (definition) | The ring looking structures in bone; basic structure of compact bone |
| Osteons are made of... | Concentric layers of mineralized collagen; mineralizing helps make structure harder; |
| Concentric layers are made of... | Collagen fibers that spiral upwards and make each lamellae (ring); the spiraled collagen fibers make a stronger structure |
| Central (Haversian) Canal | In the middle of the osteon; and contains blood vessels (nutrients) and nerve fibers |
| Volkman's canals | Run across bone perpendicular to the central canals and carry blood vessels for nutrients to many different osteons |
| Lacunae | Houses osteocytes and are located between the lamellae (rings) of the osteon |
| Short, irregular, and flat bones have... | Spongy and compact bone |
| Connective tissues in short, irregular, and flat bones | Thin plates of periosteum cover compact bone on the outside; endosteum covers spongy bone on the inside |
| Hematopoietic tissue | "Red marrow"; this is where red blood cells, white blood cells, and platelets are made |
| Red marrow (hematopoietic tissue) in infants | When born all bone marrow is red; found in medullary cavity of diaphysis and all areas of spongy bone; Most turns yellow at puberty; most of the red blood cells that will remain throughout your life are made in the red marrow when your an infant |
| Red marrow (hematopoietic tissue) in adults | trabeculae (a network of fine spicules) of flat bones; head of femur and humerus ONLY (not in any other long bones or in the bottom epiphyses of the femur or humerus); only about half of the marrow in adults is red marrow |
| Inorganic chemical composition of bone | Hydroxyapatites or mineral salts- 65% of bone by mass; many calcium phosphates; responsible for bone hardness and its resistance to compression |
| Ossification (osteogenisis) | "Making of bone"; embryo- formation of bony skeleton; until adulthood- bone growth; adult- bone remodeling |
| Embryo bone development (2 types) | 1.Membrane bone 2.Endochondral bone |
| Membrane bone (embryo bone development) | intramembranous ossification; making of bone between membranes; forms flat bones; replacement of connective tissue membrane sheets with bone |
| Definition of endochondral bone (embryo bone development) | Endochondral ossification; REPLACES cartilage with bone does not TURN cartilage into bone; This process forms long bones |
| Step 1 of Endochondral bone (embryo bone development) | A hyaline cartilage model is formed and will continue to grow and look more like a bone while actual bone is being formed; The model has a "bony collar" on either side of the model |
| Step 2 of Endochondral bone (embryo bone development) | The chondroblasts become chondrocytes and a pH change initiates calcification of the cartilage; cartilage model continues to grow |
| Step 3 of Endochondral bone (embryo bone development) | Nutrient artery penetrates middle diaphysis or through the bony collar and osteoblasts form and deposit spongy bone; as more bone is being made the bone gets closer and closer to each diaphysis |
| Step 4 of Endochondral bone (embryo bone development) | While osteoclasts break down spongy bone to form the marrow cavity the osteoblasts replace spongy bone with compact bone in the diaphysis; meanwhile the epiphyses are penetrated with a nutrient artery and being for form spongy bone (starts in center) |
| Step 5 of Endochondral bone (embryo bone development) | Left over hyaline cartilage between the diaphysis and epiphyses is turned into the epiphyseal plate or growth plate and continues bone growth; cartilage left outside epiphyses is turned into articular cartilage in joints |
| Epiphyseal plate functions | growth occurs along this line adjacent to the bone shaft; the growth occurs in the diaphysis not the epiphyses |
| Epiphyseal zones | 1.Growth zone 2.Hypertonic zone 3.Calcification zone 4.Ossification zone |
| Growth zone | near epiphyses; in this zone cartilage cells undergo mitosis and duplicate; above hypertonic zone |
| Hypertonic zone | Zone where cartilage cells enlarge and prepare to die; above calcification zone |
| Calcification zone | Zone where cartilage cells die and calcify; above ossification zone |
| Ossification zone | Zone where new bone is made from calcified cartilage cells; end of diaphysis |
| How epiphyseal plates close | The cycle of bone growth at these plates is continuous; eventually (at puberty) the cartilage cells slow down replication while the osteoblasts continue at the same rate until cartilage is replaced by bone and only a thin epiphyseal line remains. |
| Hormonal control and growth | Growth hormone- stimulates growth; thyroid hormone modulates activity; these hormones work together in that they regulate each other to maintain homeostasis |
| Overview of bone growth | Most growth stops during adolescence and early adulthood; nose and lower jaw continue to grow throughout life; Osteoclasts and osteoblasts continue throughout life reshaping and remodeling bones (bone deposition and resorption) to fit our lifestyles |
| Bone turnover | We turnover about 5-7% of bone mass per week |
| Bone deposit | laying down bone and calcifying it; done by the osteoblasts and results in new bone formation; usually occurs after injury for additional bone strength |
| Vitamins and bones (bone deposit) | Vitamin C- used in collagen synthesis; a deficit will cause scurvy Vitamin D- calcium absorption Vitamin A- balances bone deposit and absorption |
| Minerals and bones (bone deposit) | Calcium, phosphorus, and magnesium |
| Bone resorption | Break down of bone matrix; done by osteoclasts; done to raise blood calcium levels or remove necrotic debris |
| Lysosomal enzymes and bone (bone resorption) | digest the organic matrix of bone |
| Acids and bone (bone resorption) | convert Ca2+ salts |
| Bone remodeling is regulated by: | hormonal regulation and mechanical stress |
| Hormonal regulation of bone remodeling | regulate blood calcium levels and homeostasis tightly by a negative feedback loop; the hormones used are calcitonin and parathyroid |
| Calcitonin & parathyroid hormones (bone remodeling) | Calcitonin- secreted by thyroid gland and stimulates osteoblasts and suppresses parathyroid gland Parathyroid hormone- secreted by parathyroid, stimulates osteoclasts and suppresses thyroid gland |
| Mechanical stress and bone remodeling | Ex. femur -Standing causes stress on the femur; to cope the medial side will compress and lateral side will stretch (tensile forces); lateral side contains more collagen while the medial side contains more mineral; bone adapts to the stress put on it |
| Bone homeostatic imbalances (bone disease) | 1.Osteomalacia 2.Osteoporosis 3.Pagets disease |
| Osteomalacia | "soft bone"; inadequate mineralization but plenty of collagen; pain when weighted; called rickets in children; causes bow legs and deformities to pelvis, skull, and ribcage; nutrition- Vitamin D |
| Osteoporosis | Bone resorption is greater than deposit but matrix composition is normal; occurs in spongy bone, femur, neck/spine; hormone replacement therapy can help; height loss due to minor fractures in the spine; most common in women (post menopause) |
| Pagets disease | Excessive bone formation and breakdown; abnormal ratio of spongy bone to compact bone; poor mineralization of new bone; may be viral in origin |
| Bone heals... | similar to embryonic ossification; 5 steps |
| Step 1 of bone healing | Hematoma (clot) forms; injured cells die; swelling, pain, and inflammation; this occurs shortly after break |
| Step 2 of bone healing | White blood cells come to get rid of foreign materials and get rid of dead white blood cells |
| Step 3 of bone healing | Fibrocartilage callus; soft callus (granulation); capillaries form; fibroblasts, chondroblasts, and osteoblasts are not present; occurs 2-4 days after break |
| Step 4 of bone healing | bony callus; spongy bone forms; connects ends of broken bone |
| Step 5 of bone healing | Bone remodeling; begins with bony callus formation; then formation of the medullary cavity; then lastly formation of compact bone |
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