Ch 7: Skeletal System Flashcards
What are the functions are skeletal system?
support; protection; blood cell production; storage; and motion
Examples of bone tissue
- spongy bone/. cancellous bone
2. compact bone
spongy bone
network of bony shafts or trabeculae, surrounded by bone marrow
compact bone
highly organized; composed of repeating osteons; composed of a central Haversian Canal (passage of blood vessels); lamellae (rings of matrix); lacunae (small holes in matrix where bone cells are located); osteocytes (bone cells); and canaliculi (cytoplasmic extensions of osteocytes, which travel from cell to cell and transport nutrients and wastes)
structure of a limb bone
2 epiphyses (broad ends; contain spongy bone); 1 diaphysis (shaft; compact bone on outer part, and spongy bone lines the marrow cavity)
periosteum
covers outer surface of bone; isolates bone from surrounding soft tissue; passage of blood vessels and nerves; growth and repair; becomes continuous with tendons
endosteum
lines marrow cavity; active during bone growth; contains giant osteoclasts, which are multinucleated (50), and eat the bone matrix to attack invaders, remove damaged cells, and release calcium
bone development
- intramembranous ossification
2. endochondral ossification
intramembranous ossification
occurs in flat, short, and irregular bones, known as dermal bones; osteoblasts form from C.T.; roof of jaw; clavicle; mandible
intramembranous mechanism
a) Condensation of mesenchyme into soft sheet permeated with blood capillaries
b) Deposition of osteoid tissue by osteoblasts on mesenchymal surface; entrapment of first osteocytes; formation of periosteum
c) Honeycomb of bony trabeculae formed by continued mineral deposition; creation of spongy bone
d) Surface bone filled in by bone deposition, converting spongy bone to compact bone; persistence of spongy bone in the middle layer
endochondral ossification
occurs in limb bones; osteoblasts form from cartilage; metaphysic region (metaphysis ) in limb bone, which is between epiphysis and diaphysis; known as growth plate, or epiphyseal plate; as mitosis occurs, limb bone lengthens; process ends around age 16 to 18 years
endochonral mechanism
a) Mesenchyme develops into a body of hyaline cartilage, covered with a fibrous perichondrium; the perichondrium produces chondrocytes and the cartilage model grows in thickness
b) The perichondrium stops producing chondrocytes and begins producing osteoblasts; formation of bony collar around middle of cartilage; perichondrium converts into periosteum; formation of the Primary Ossification Center (area of chondrocyte enlargement in diaphysis)
c) Blood vessels penetrate the bony collar and invade the primary ossification center; formation of primary marrow cavity; formation of Secondary Ossification Center
d) Formation of secondary marrow cavity in the epiphyses
zones in metaphysis
- zone of reserve cartilage
- zone of cell proliferation
- zone of cell hypertrophy
- zone of calcification
- zone of bone deposition
zone of reserve cartilage
farthest from Marrow Cavity; consists of typical Hyaline Cartilage
zone of cell proliferation
chondrocytes multiply and arrange themselves into longitudinal columns of flattened lacunae
zone of cell hypertrophy
chondrocytes cease to divide and begin to hypertrophy (enlarge)
zone of calcification
minerals are deposited in the matrix and calcify the cartilage
zone of bone deposition
chondrocytes die; osteoblasts form and begin to lay down bone matrix; closest to marrow cavity
what are other factors that affect bone development
growth hormone (pituitary) and thyroxine (thyroid) target growth plate; vitamin D (absorbs calcium) and calcium are needed for health of bone tissue
calcitonin
thyroid hormone; released when blood calcium levels are elevated; functions to lower blood calcium levels; a) inhibits osteoclasts; b) decreases intestinal absorption of calcium; and c) increases calcium loss at the kidneys
parathormone
parathyroid hormone; released when blood calcium levels are decreased; functions to raise blood calcium levels; a) stimulates osteoclasts; b) increases intestinal absorption of calcium; and c) decreases calcium loss at the kidneys
types of fractures
- compound (open)
- simple (closed)
- complete
- incomplete
- comminuted
- greenstick
- pathological
compound (open) fracture
skin broken
simple (closed) fracture
skin is not broken
complete fracture
bone broken all the way through; completely
incomplete fracture
bone is not broken all the way through; partial
comminuted fracture
bone shatters; fragmented
greenstick fracture
common in children; bone broken on one side and bent on the other side
pathological fracture
bone fractures due to disease
rickets (child)/ osteomalacia (adult)
both due to vitamin D deficiency; bones become weak and softening of bone; in rickets can have bowing of the femurs; bone can fracture easily in both
osteomyelitis
rare today; serious bacterial or fungal infection; can affect bone and bone marrow
osteoporosis
severe reduction in bone mass; possible causes include, hyperparathyroidism; hypothyroidism; vitamin C deficiency; decrease in estrogen (menopause); prolonged bed rest; heredity; and vitamin D and calcium deficiencies; can lessen effects with exercise, calcium and vitamin D supplements, and estrogen if female
