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Ch. 6 bones

Bone and skeletal tissues

QuestionAnswer
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
Created by: Rootb