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CBIO 2200: Skeletal System
Ostology |
study of bone |
Osseous Tissue |
Bone tissue
connective tissue in which the matrix is hardened by the depostition of calcium phosphate and other minerals |
Make-up of Bone |
osseous tissue
blood
bone marrow
cartilage
adipose tissue
nervous tissue
fibrous connective tissue |
Living Skeleton |
support for soft tissues
contains nerves and blood vessels that provide nutrition |
Components of the Skeletal System |
Cartilage
ligaments
tendons
bone |
Cartilage |
covers many joint surfaces in the mature skeleton
hyaline of epiphyses
between vertebrae to absorb shock |
Ligaments |
hold bone to bone |
Tendons |
hold muscle to bone |
Functions of Skeletal System |
support
protection
movement
electrolyte balance
acid-base balance
blood formation |
Flat-Shape Bone |
tend to be curved, wide, thin (skull)
enclose and protect soft organs and provide broad surfaces for muscle attachment
cranial bones, ribs, sternum, scapula, hip bones |
Long Bone |
longer than wide, act as levels to produce body movement
femur, ulna, radius, humerus, metacarpals and phalanges, tibia, fibula, metatarsals |
Compact Bone |
Dense white osseous tissue that composes the outer shell of the bone
Composes 3/4 of bone weight in body |
Diaphysis |
Shaft of bone
provides leverage |
Epiphyses |
Head end of each bone
Enlarged to strengthen joint and provide extra surface area for attachment of muscles |
Songy (cancellous) Bone |
Ends of bone in more central space
Loosely organized form of osseous tissue
Composes 1/4 of bone weight in body
trabeculae arranged along bone's lines of stress |
Periosteum |
external sheath that covers bone that has an outer fibrous layer of collagen and an inner osteogenic layer of bone-formming cells |
Endosteum |
Thin layer of reticular connective tissue with cells that dissolve osseous tissue and others that deposit it found on the internal surface of the bone |
Epiphyseal Plate |
growth plate
Area of hyaline cartilage that separates the marrow spaces of the epiphysis and diaphysis in children and adolescents
Lines mark where the plate used to be in adults |
Short Bone |
Equal in length and width with limited motion
Glide across one another
carpal, tarsal |
Irregular Bones |
elaboratly-shaped bones that do not fit into other categories
sphenoid, vertebrae, ethmoid
|
Medullary Cavity |
marrow cavity, contains bone marrow |
Articular Cartilage |
Layer of hyaline cartilage found at joint surface
Enables joint to move far more easily |
Nutrient Foramina |
Blood vessels and nerves supply exit and enter through this
Tiny openings in periosteum |
Perforating Fibers |
collagen fibers that penetrate the bone matrix |
Dipole |
Spongy layer in cranium that can absorb impact of blow to the skull |
Osteogenic Cells |
Bone stem cells (osteoprogenitor)
Found in endosteum and inner layer of periosteum
Arise from undifferentiated embryonic mesenchymal cells
Multiply continually
Lay down matrix |
Osteoblasts |
Nonmitotic cells
Lay down bone matrix
Bone forming cells
Synthesize soft organic matter of the bone matrix
Stress and fractures stimulate osteogenic cells to produce more
Secrete osteocalcin |
Osteoclasts |
Bone matrix eating cells found on the surface of the bone
Hematopoetic origin
Formed by the fusion of several stem cells
ruffled border increases surface area and efficiency of bone reabsorption |
Osteocytes |
Osteoblasts that got stuck in matrix
Lacunae communicate through cancliculi
Connected by gap junction so they can pass nutrients and chemical signals to each otehr and pass their metabolic wastes to the nearest blood vessels for disposal
reabsorb matrix
deposit matrix
strain sensors: help regulate adjustments to bone shape and density in adaption to stress |
Bone Marrow |
General term for soft tissue that occupies the marrow cavity of a long bone |
Red Marrow (myeloid tissue) |
Hemopoietic tissue (tissue that produces blood cells)
Fills nearly every bone in a child
Limited to skull, vertebrae, ribs, sternum, part of the pelvic girldle and the proximal heads of the humerus and femur in an adult |
Yellow Marrow |
Found in adults
Fat cells replace healthy red cells
Bone marrow responds to metabolic needs. Process can be reverted if needed by body
No longer produces blood cells, can transform back into red marrow in the event of sever or chronic anemia |
Intramembraneous Ossification |
Replacement of embryonic CT with bone
condensation of mesenchyme into soft sheet permeated with blood capillaries. Start connecting to form a network of soft sheets called trabeculae
Deposition of osteoid tissue by osteoblasts on mesenchymal surface. Entrapment of first osteocyte; formation of periosteum
Honeycomb of bony trabeculae formed by continued mineral deposition; creation of spongy bone. MArrow cavity starting to form
Surface bone filled in by bone deposition, converting spongy bone to compact bone. Persistence of spongy bone in the middle layer
Formation takes place at numerous sites simultaneously
produces flat bones of skull, scapula, ribs, and clavicle |
Endochonical Ossification |
Replacement of cartilage with bone
Bone develops from preexisting model composed of hyaline cartilage
early cartilage model (precursor)
Formation of primary ossification center, bone collar and periosteum
Vascular invasion, formation of primary marrow cavity and appearance of secondary ossification center. Osteoblasts deposit osteod tissue and form a temporary network of trabeculae. Osteoclasts dissolve calcified cartilage and enlarge the marrow cavity of the diaphysis.
Bone at birth, with enlarged primary marrow cavity and appearance of secondary marrowcavity in epiphyses.
Bone of child with epiphyseal plate at distal end. Plate persists through childhood and adolescence and serves as a growth zone for bone elongation
Cartilage (plate) separates first and second marrow cavity. Lasts until 20-25 years of age "growth plate"
Adult bone with a single marrow cavity and close epiphyseal plate. Primary and secondary marrow cavities unite into a single cavity so bone can no longer grow in length. |
Zones of Metaphysis |
zone of reverse cartilage
zone of cell proliferation
zone of cell hypertrophy
zone of calcificaiton
zone of bone deposition |
Zone of Reverse cartilage |
consist of typical hyaline cartilage that shows no sign of transforming yet |
Zone of Cell Proliferation |
chondrocytes multiply and arrange themselves into longitudinal columns of flattened lacunae |
Zone of Cell Hypertrophy |
Stopped dividing. Increasing by size. Walls of matrix between lacunae become very thin |
Zone of Calcification |
chondrocytes calcify (add minerals, hardens). DEposits are only temorary support for the cartilage. |
Zone of Bone Deposition |
walls of lacunae fall away- osteoblasts take over. Zone of spongy bone created at the end of the marrow cavity facing the metaphysis. |
Appositional Growth |
Bones increase in width throughout life
Deposition of new bone at the surface
limited amount of growth can occur in bone due to space
similar to intramembraneous ossification |
Orderly Bone Remodeling |
balance between bone deposition and reabsorbtion
disruptions in this balance can lead to done deformities |
Paget's Disease |
Osteitis Deformans
Deformation of bone
Too much bone deposition or absorption or both.
Bone is thickening with small marrow cavity or vice versa.
Weak bones due to increased rate of turnover
Can cause bowed legs |
Osteogenesis Imperfecta |
Brittle Bones
Autosomal dominant disorder of type 1 collagen
lack of type 1 collagen or the production of defective type 1 collagen
necessary ossification does not occur
Leads to brittle bones that fracture easily
can be limbs or axial bones |
Osteoporosis |
Thining of bone tissue and loss of bone density over time
seems to have a greater effect on spongy bone (because of increased metabolic activity)
space between the trabeculae becomes larger
Common risk factors include: corticoid steroids, bedridden people, chronic kidney disease, vitamin D deficiency |
Achondroplastic Dwarfism |
long bones have stopped growing
limbs do not grow, the stay small
forehead is prominent (in proportion to head and limbs)
Torso is normal size
caused by spontaneous mutation in chromosome (two normal people can have a dwarf child. I fa parent already had chromosomal mutation, increased chance of child being a dwarf) |
Pituitary Dwarfism |
no distortion of body proportions
person has shorter, smaller stature
lack or decrease in growth hormones |
Mineral Deposition |
A crystallization process in which calcium, phosphate, and other ions are taken from the blood plasma and deposited in bone tissue, mainly as crystals of hydroxipatite. Deposition begins in fetal ossification and continues through life. |
Abnormal Calcification (Ectopic Ossification) |
Bone-like material in random places
i.e. plaque in the arteries, calulus (a calcified mass in a soft organ) in the lungs |
Mineral Reabsorption |
process of dissolving bone by releasing minerals into the blood making them available for other uses |
Hypocalcemia |
Calcium deficiency.
Causes excessive excitability of the nervous system and can lead to muscle tremors, spasm, or tetany (inability of the muscle to relax), heart arrhythmia |
Hypercalcemia |
Blood calcium excess is rare
Causes nerve and muscle cells to be less excitable than usual
Can cause depression, emotional disturbances, muscle weakness, sluggish reflexes and cardiac arrest |
Calcium homeostasis is regulated by ____, ____, and ____ |
Calcitrol
Parathyroid
Calcitonin |
Orthopedics |
Study of bone disorders |
Stress Fracture |
Break caused by abnormal trauma to a bone |
Pathological Fracture |
break in a bone weakened by some other disease |
Nondisplaced Bone Fracture |
Separated but still in correct orientation |
Displaced Bone Fracture |
Break in bone, no longer in normal position |
Comminuted Bone Fracture |
Broken in several places in several pieces |
Greenstick Bone Fracture |
Break on one side of the bone while other side remains intact |
Buckle Fracture |
Cortex has buckled on both sides of the bone |
Healing Process of Bone |
Formation of hematoma and granulation tissue
Formation of a soft callus
Conversion to a hard callus. Takes 4-6 weeks. Important to have bone immobilized to prevent reinjury
Bone remodeling can take 8-12 weeks or even up to 6 months for multiple fractures. Depends on the location and type |