Ch. 5 - Skeletal System Flashcards
Growth of Cartilage
Appositional growth, interstitial growth
Appositional growth (of cartilage)
growth at apical surface
- starts in perichondrium
- mesenchymal cells at periphery form inner layer of perichondrium (stem cells in top of cartilage)
- chondrogenic cells aggregate and become chondroblasts
- chondroblasts secrete matrix=forces cells apart (forms lacunae)
- chondrocytes become enclosed in matrix (more matrix thickens cartilage)
Interstitial growth (of cartilage)
growth within cartilage
- chondrocytes divide within lacunae (mature cells can divide deep within cartilage and add more matrix)
- daughter cells secrete matrix
- cells move apart, expanding cartilage from within
Osseous Tissue (parts)
Anatomy of a long bone:
- Diaphysis- shaft
- Epiphysis- ends of a long bone (area forms a joint)
- Metaphysis- growth plate region
- Articular Cartilage- over joint surfaces (acts as friction/shock absorber) *usually hyaline
- Medullary Cavity- marrow cavity
General Facts of Osseous Tissue
has supportive CT
- contains specialized cells
- has solid extracellular matrix (made of protein fibers and ground substance with Ca salts. small amount is water)
Bone Histology
Cells: about 2% of bone mass
osteogenic, osteoblast, osteocytes, osteoclasts
osteoprogenitor
undifferentiated, mesenchymal cells (can become any other bone cell)
-mitotic (can divide and repair), become osteoblasts
play role in fracture repair
*found in innermost layer of periosteum and the endosteum lining the medullary cavity
osteoblasts
cannot divide
- secrete osteoid that helps build matrix (helps repair and make bone stronger)
- found on outer surfaces of bone
osteocytes
mature cells in lacunae
- most common
- don’t divide
- maintain Ca and phosphate balance
- nourish bone
- find in osteons in bone matrix
osteoclasts
large, multinucleated
- involved in osteolysis (breaking down bone)
- eat own bone if body is calcium deficient
bone matrix
98% of bone mass inorganic materials: (no carbon) -hydroxyapatite -Ca salts (brittle salts) -ions=Na, K, Mg organic: (carbon) -collagen (flexible/strong) -glycoproteins -proteoglycans -osteoid area of bone
Types of bones
compact-dense bone arranged in osteons
spongy-some matrix but not as dense
Compact bone: organization
osteon
- lamellae
- osteocytes in lacunae
- canaliculi
- central osteonic canal (BV’s)
perforating canals (compact bone)
Blood vessels deeper in bone tissue that connect osteonic canals to other osteonic canals
interstitial lamellae (compact bone)
between osteons
-areas of matrix that do not have blood vessels or central osteonic canals anymore *old osteons
outer circumferential lamellae (compact bone)
anchors periosteum to bone (ring of matrix between osteons and osteoid)
Spongy Bone
-no osteons
have trabeculae:
-branching networks of bone tissue
-supported by reticular CT and have osteoblasts, osteocytes, and osteoclasts. No central canal because blood supply present
-spaces filled with red marrow (blood development)
-in ends of long bones and inside flat bones
-lightens weight of bone
-can grow and change shape and direction in order to provide support
Bone Membranes
periosteum, endosteum
Periosteum
anchors bone (CT that surrounds bone)
- contains osetoprogenitor cells that become osteoblasts
absent: - at site of bone attachment
- anywhere there is articular cartilage
- tendons/muscles/ligament site
layers: outer fibrous layer (produce collagen fibers)
inner osteogenic layer that grows new bone cells and maintenance
Bone Marrow
- yellow marrow (energy storage)
- reticular network filled with adipose CT *mostly adipose/high adipose concentration
- in medullary cavity of long bones - red marrow
- areolar CT (produces blood cells and gets its red color from hemoglobin)
located: medullary cavities of infants and spongy bone in adults
Osteogenesis
bone development
ossification
replacing CT with bone
types:
1. intramembranous- mesenchymal cells to spongy bone
2. endochondral- hyaline cartilage to spongy bone
Intramembranous Ossification (General)
- starts at 8 weeks in embryo development
- usually finished by week 15
forms: cranial, facial, dentary, clavicle, sesmoid bones (embedded in tendon)
Intramembranous Ossification (Process)
- mesenchymal cells in CT differentiate into osteoblasts.
- These osteoblasts begin making the osteoid bone matrix
- Some osteoblasts become isolated and become osteocytes (cells of inner periosteum form compact bone). Bone matrix surrounds BV’s.
- Spongy bone is created on the inner portion where the bone matrix surrounded BV’s and the result is spongy bone covered in a thin layer of compact bone (BV’s in spongy bone important for waste transfer in these early developmental stages)
* forms ribs/scapula/pelvis/skull