Human Anatomy Chapter 6 Flashcards
Skeletal system is made of
Skeletal bones, cartilage, ligaments, connective tissue to stabilize the skeleton
Bones as alive consists of several tissues, huge supply of blood
Function of the skeletal system
Support: provides the framework for the attachment of other organs
Storage: Calcium ions 98% in bones, phosphate ions
Blood cell production: bone marrow produces erythrocytes, leukocytes, and platelets
Leverage: muscle pull on bones to produce movement
Protection: ribs protect heart, skull protects brain, vertebrae protects spinal cord, pelvic bone protects reproductive organs
Osseous tissue
Supporting connective tissue,
Matrix of bone consists of: calcium phosphate converted to hydroxyapatite crystals-resist compression
Calcium phosphate makes up 2/3 of bone mass
Collagen fibers
Makeup 1/3 of bone matrix
Contribute to the tensile strength of bones
Collagen and hydroxyapatite make bone tissue strong
Bone cells
Contribute only 2 percent of the bone mass
Osteocytes
Mature bone cells
Maintain protein and mineral content of the matrix
Cause the release of calcium ions from bone to blood
Sit in depressions called lacunae
Matrix layer associated with osteocytes is lamella
Small channels extending from the osteocytes to the bone capillaries are called canaliculi
Osteoblasts
Immature bone cells
Found in the inner and outer surfaces of bones
Produce osteoid involved in making the matrix
Osteoblasts are involved in making new bones called osteogenesis
Osteoprogenitor cells
Bone stem cells
Found on the innermost layer of the periosteum and inner lining of the endosteum
Differentiate to form new osteoblasts
Involved in repair of bones after a break
Osteoclasts
Multinucleated cells
Secrete acids, release of stored calcium ions and phosphate ions into the blood called osteolysis
Compact bone
Dense bone
Compact bones are dense and solid
Forms the walls of bone
Spongy bone
Trabecular or cancellous bone
Open network of plates
Surrounds the medullary cavity
Medullary cavity consists of bone marrow
Compact bone (structure)
Consists of osteons, central canal (haversian canal), canaliculi (channels), osteocytes (inside lacunae), lacunae, lamellae: concentric, interstitial, circumferential, perforating canals
Spongy bone (structure)
Arranged in branching plates called trabeculae
Trabecular forms an open network
Creates the lightweight nature of bones
Compact bone (functional)
Conducts stress from one end of the long bone to the other, generates strength
Weak strength when stress from sides
Osteon arrangement parallel to bone axis
Spongy bone (functional)
Trabeculae creates strength to deal with side stress, oriented along the stress lines
Extensive cross-branching
Supports yellow marrow in shaft of bone
Supports red marrow in the epiphysis of the bone
Epiphysis
Ends of the long bones
Consists of red marrow
Diaphysis
Shaft of the long bones
The medullary cavity of the diaphysis consists of yellow marrow
Shaft breaks, a fracture will occur
Metaphysis
Narrow growth zone between the epiphysis and the diaphysis
Periosteum
Outer surface of the bone: consists of a fibrous layer and an osteogenic layer
Isolates and protects the bone from surrounding tissue
Provides a route and a place for attachment for circulatory and nervous supply
Actively participates in bone growth and repair
Attaches the bone to the connective tissue network of the deep fascia via perforating fibers
Endosteum
Inner surface of bone
Lines the medullary cavity
Consists of osteoprogenitor cells
Actively involved in repair and growth
Ossification
Fibrous tissue and cartilage cells will be replaced by bone cells
Hyaline cartilage
Up to eight weeks of development
Intramembranous ossification
Bone formed from fibrous tissue
Involved in the development of clavicle, mandible, skull, and face
Mesenchymal cells differentiate to form osteoblasts
Osteoblasts begin secreting a matrix: osteoblasts trapped in matrix, differentiate and form osteocytes, more osteoblasts produced and move outward
Blood vessels are trapped by the formation of spicules
Endochondral ossification
Bone formed from cartilage tissue
Involved in the development of limbs, vertebrae, and hips
Chondrocytes near the center of the diaphysis increase in size
Blood vessels begin to grow around the cartilage
The perichondrial cells begin to form the periosteum: a thin layer of compact bone forms
Cartilage cells die and are replaced by osteoblasts: osteoblasts begin to form spongy bone, primary ossification center
Cartilage in the metaphysics region is invaded by osteoblasts
An increase in bone length and diameter begins
Osteoblasts begin to migrate to the epiphysis: secondary ossification center
Osteoblast begin to replace cartilage with bone
Results in pushing epiphysis away from diaphysis resulting in longer bones
Osteogenesis
The process of bone formation
Calcification
The deposition of calcium ions into the bone tissue
Epiphyseal closure
Area of cartilage in the metaphysis (forms the epiphyseal line)
Cartilage near the diaphysis is converted to bone
At the ends of the bones is a layer of cartilage (articular cartilage)
Appositional growth
Inner layer of the periosteum differentiates to form osteoblasts and adds bone matrix to the surface
Forms circumferential lamellae to the outer surface
Osteons form
Bone continues to enlarge in diameter
Four major sets of blood vessels
Nutrient vessels (nutrient artery and nutrient vein)
Metaphyseal vessels
Epiphyseal vessels
Periosteal vessels
Nutrient vessels
Enter the diaphysis and branch towards the epiphysis: enter through the nutrient foramen of the bone, sensory nerves enter the bone through the nutrient foramen along with the nutrient artery
Penetrate the shaft and enter the medullary cavity: divide into ascending and descending branches to go towards the epiphysis regions, vessels branch to form perforating vessels
Metaphyseal vessels
Supply nutrients to the diaphyseal edge of the epiphysis
Epiphyseal vessels
Supply nutrients to the cavities of the epiphysis
Periosteal vessels
Supply nutrients to the superficial osteons
Minerals
Calcium ions/phosphate ions/magnesium ions/citrate/carbonate ions/sodium ions, factors regulating bone growth, bones need a constant supply of minerals via a good diet
Vitamins
A and C, factors regulating bone growth
Vitamin A stimulates osteoblasts
Vitamin C is necessary for collagen formation and osteoblast differentiation
Calcitriol
Cholecalciferol (vitamin D3), factors regulating bone growth
Made in the kidneys from cholecalciferol (D3)
Vitamin D3 is made in the skin via UV radiation and diet
Necessary for absorption of calcium ions and phosphate ions
Hormones
Parathyroid hormone/calcitonin/growth hormone/thyroxine, factor regulating bone growth
Parathyroid gland releases parathyroid hormone: stimulates osteoclasts, stimulates osteoblasts, increases circulating calcium levels by aiding calcium ion absorption from small intestines and reducing calcium ion loss from kidneys
Thyroid gland releases calcitonin: inhibits osteoclasts, decrease circulating levels of calcium, increase rate of calcium ions loss in urine and removing calcium from blood and adding it to bone
Thyroid gland release thyroxine: maintains normal activity in epiphyseal region for growth
Pituitary gland releases growth hormone: maintains normal activity in the epiphyseal region for growth
Sex hormones
Estrogen/testosterone, factor regulating bone growth
Estrogen and testosterone stimulate osteoblast activity: osteoblast activity produces bone faster than epiphyseal cartilage expansion
Ultimately the epiphyseal cartilage narrows and bone growth ceases
