Chapter 6 - Skeletal System I - Bone Tissue Flashcards
Approximately how many bones are in the human body?
206
Cartilage
embryonic forerunner of most bones and covers many joint surfaces
Ligaments
hold bone to bone at joint
Tendons
attach muscles to bone
Functions of the Skeleton
- Support
- Movement
- Protection
- Blood Formation
- Electrolyte Balance (Ca+ and phosphate)
- Acid-Base Balance
- Detoxification
Osteology
study of bone
Bone is a ____________ tissue with a hard matrix.
connective
Mineralization (calcification)
process of hardening
Other Tissues Present in Bone
- Blood
- Bone Marrow
- Cartilage
- Adipose Tissue
- Nervous Tissue
- Fibrous Connective Tissue
Shapes of Bone
Flat - thin, often curved (e.g. ribs)
Long - rigid levers for movement (e.g. humerus)
Short - glide within joints (e.g. carpals)
Irregular - complex shape (e.g. vertebrae)
Features of Long Bones
- Compact and spongy (cancellous) bone tissue
- Two epiphyses (heads)
- Dyaphysis (shaft)
- Epiphyseal line - remnant of growth plate
- Periosteum covering bone
- Nutrient foramina
- Articular cartilage - smooths joints
Features of Flat Bones
- Spongy bone sandwiched between plates of compact bone
Types of Bone Cells
- Osteogenic (osteoprogenitor) cells
- Osteoblasts
- Osteocytes
- Osteoclasts
Osteogenic (Osteoprogenitor) Cells
- Stem cells
- Found in: endosteum, inner periosteum, central canals
- Give rise to other bone cells
Osteoblasts
bone-forming cells
Osteocytes
- Mature, non-dividing bone cells
- Within a matrix
- Lacunae: cavities that house osteocytes
- Canaliculi: small canals that connect lacunae
Osteoclasts
large, bone-dissolving marcrophages
Bone Matrix
- 1/3 Organic (collagen & large protein-carbohydrate complexes)
- 2/3 Inorganic
- 85% hydroxyapatite (crystallized calcium phosphate salt)
- 10% calcium carbonate (CaCO3)
- 5% other inorganic minerals
Compact Bone
- Osteon = basic unit
- Concentric lamellae
- Lacunae containing osteocytes
- Central (haversian) canal
- Perforating canals
- Circumferential lamellae
Spongy Bone
- Spicules: rods and spines of bone
- Trabeculae: thin plates of bone
- Porous appearance (spaces filled w/ marrow)
- Light weight but strong
Bone Marrow
- Soft tissue located in medullary cavities of long bones, spaces within spongy bone, and large canals within osteons
- Red Marrow (Myeloid Tissue): hemopoietic tissue, both RBCs and WBCs are made here
- Yellow Marrow: mainly fat
Locations of Red Marrow
- Skull
- Vertebrae
- Sternum
- Ribs
- Parts of pelvic girdle
- Proximal heads of humerus and femur
Location of Yellow Marrow
long bones of limbs
Bone Growth: Elongation
- bones grow longer at epiphyseal plates
- plates made of hyaline cartilage, metaphyses
Bone Growth: Widening and Thickening
- appositional growth: growth in diameter and thickness
- intramembranous ossification at surface
- osteoblasts in periosteum deposit matrix
- once matrix hardens, cells become osteocytes
- circumferential lamellae are formed
- osteoclasts widen medullary cavity
Wolff’s Law of Bone
- bone shape is determined by mechanical stress
- bone adapts to withstand stress
- form follows function
Calcium and Phosphate
raw materials for calcified ground substance
Vitamin A
promotes formation of glycosaminoglycans (protein-carbohydrate fibers)
Vitamin C (ascorbic acid)
promotes collagen cross-linking
Vitamin D (calcitriol)
necessary for calcium absorption by small intestine and reduces urinary calcium loss
Calcitonin
- secreted by thyroid gland
- stimulates osteoblasts in children and pregnant women
Growth Hormone
- promotes intestinal absorption of calcium
- stimulates growth plates and bone elongation
Estrogen & Testosterone
- sex steroids
- stimulate long bone growth during adolescence
Parathyroid Hormone (PTH)
- secreted by parathyroid glands
- stimulates bone reabsorption to boost level of calcium in blood
Ageing of Skeletal System
- osteopenia: loss of bone (severe = osteoporosis)
- reabsorption faster than deposition
- After 35 years: osteoblasts less active than osteoclasts
- After 40 years: females lose 8% of bone mass per decade, males lose 3%
- fracture more common, heal slowly
Stress Fracture
caused by abnormal trauma
Pathological Fracture
occurs in bone weakened by a disease such as osteoporosis
Fractures are Classified According to…
- breaking of skin
- direction of fracture
- separation of bone pieces
Treatment of Fractures
- closed reduction: nonsurgical manipulation
- open reduction: surgical setting involving plates, screws, or pins
- cast
- heal in 8-12 weeks
Osteoporosis
- bone lose mass and become subject to pathological fractures
- hip, wrist, vertebrae are especially vulnerable
- postmenopausal white, light-build women at greatest risk
- treatments: bis-phosphonates (destroys osteoclasts) and parathyroid hormone (stimulates osteoblasts)
- prevention: weight-bearing exercise, adequate calcium and protein
Orthopedics
prevention and correction of injuries and disorders of bones, joints, muscle
