A&P Unit 5 pt. 2

Anatomy of a long bone

- Periosteum - Perforating (Sharpey's) Fibers - Arteries - Articular Cartilage - Epiphyseal Plate - Epiphyseal Line - Marrow (Medullary) Cavity

osteoprogenitor (osteogenic) cells

Mesenchymal stem cells that divide to produce osteoblasts Located in: Endosteum - lines the medullary cavity and passageway for blood vessels found in the matrix of compact bone The inner cellular layer of periosteum Important in fracture repair

axial vs appendicular skeleton

axial: on the midline; vertebrae, ribs, skull appendicular: all the bones of the limbs

vitamins involved in bone health

Vitamins A, D, K, and C

stages in the healing of a bone fracture

1. Hematoma forms 2. Fibrocartilaginous callus forms 3. Bony callus formation 4. Bone remodeling

Osteoporosis

A condition in which the body's bones become weak and break easily.

Periosteum

A dense fibrous connective tissue covering the surface of bones (except at their extremities) and serving as an attachment for tendons and muscles.

ground substance of bone

A small volume of liquid surrounding insoluble crystals of calcium salts

perforating canals

Perpendicular to the central canal Carry blood vessels into bone and marrow

bone marrow

Red bone marrow forms some blood cells. Yellow bone marrow stores fat.

hyaline cartilage

The most abundant cartilage type in the body; provides firm support with some flexibility; it is found on the ends of long bones, ribs, and nose

flat bones

These bones are thin, flat, and curved. They form the ribs, breastbone, and skull.

Fibrocartilage

cartilage that contains fibrous bundles of collagen, such as that of the intervertebral disks in the spinal cord.

elastic cartilage

cartilage with abundant elastic fibers; more flexible than hyaline cartilage

epiphyseal plate

cartilaginous area at the ends of long bones where lengthwise growth takes place in the immature skeleton

interstitial vs appositional growth

from inside the cartiladge mitosis of chondrocytes outside edge of the cartiladge mitosis of stem cells

osteon

i. Central canal: at center of osteon; carries blood vessels and nerves ii. Concentric lamellae: rings of bone around the central canal iii. Osteocytes: Housed in lacunae between concentric lamellae iv. Canaliculi: Tiny, interconnecting channels within bone that extend between lacunae; allows osteocytes to connect & communicate

Osteoclasts are

i. Fixed macrophages ii. Dissolve bone matrix (Osteolysis)

Osteocytes

i. Mature bone cells ii. In lacunae, Connected by canaliculi iii. Low metabolic rate; monitor bone stress

short bones

i. Roughly cube-shaped ii. Carpals and tarsals

irregular bones

i. Various shapes, do not fit into other categories ii. Prominent surfaces iii. Ex. Vertebrae

zone of epiphyseal plate

i. Zone of resting cartilage: Farthest from medullary cavity and nearest epiphysis; small chondrocytes in hyaline cartilage ii. Zone of proliferating cartilage: Larger chondrocytes undergoing rapid mitotic cell division; aligned like stacks of coins iii. Zone of hypertrophic cartilage: Chondrocytes cease dividing and become enlarged iv. . Zone of calcified cartilage: Deposited minerals kill the chondrocytes and make matrix opaque v. Zone of ossification: Walls between lacunae break down, forming channels that become invaded with capillaries and osteoprogenitor cells

long bones

i. longer than wide - a shaft plus ends ii. Have a marrow cavity iii. Ex: femur, humerus

ligaments vs tendons

ligaments connect bone to bone and tendons connect muscle to bone

circumferential lamellae

located deep to periosteum and superficial to endosteum and extend around entire circumference of the diaphysis and resist twisting of long bone

Ossification (osteogenesis)

process of bone tissue formation

interstitial lamellae

remains of old osteons that broke down as bone grew and remodeled itself

Osteoblasts

specialized bone cells that build new bone tissue

Calcification

the secretion of extracellular matrix stops, and the cells, now called osteocytes, lie in lacunae and extend their narrow cytoplasmic processes into canaliculi that radiate in all directions; within a few days, calcium and other mineral salts are deposited and the extracellular matrix hardens or calcifies

ground substance

unstructured material that fills the space between the cells and contains the fibers

Why does bone need blood supply and nerves?

· Bone is highly vascularized · Four major sets of blood vessels: i. Nutrient artery and vein: Supply the diaphysis of a long bone; usually just one nutrient artery and vein per bone ii. Metaphyseal arteries and veins: Supply the diaphyseal side of the epiphyseal plate iii. Epiphyseal arteries and veins: Supply the epiphyses iv. Periosteal arteries and veins: Supply blood to the external circumferential lamellae and superficial osteons · Nerves accompany blood vessels through the nutrient foramen

compact vs spongy bone

· Compact bone - dense, solid outer layer of bone · External surfaces of long and flat bones · Spongy (cancellous) bone - internal network of boneàhoneycomb of trabeculae · Internal surface of bones

I. What are the components and functions of the skeletal system?

· Components : i. Bones of the skeleton ii. Cartilages iii. Ligaments iv. Other connective tissues that stabilize and connect · Functions : i. Support - provides hard framework ii. Movement - skeletal muscles use bones as levers iii. Protection of underlying organs iv. Mineral storage - reservoir for important minerals v. Blood-cell formation - bone contains red marrow vi. Triglyceride (energy) storage in bone cavities

development of bone

· Endochondral ossification i. Begins with hyaline cartilage model ii. Produces majority of bones in the body · Steps i. The fetal hyaline cartilage model develops ii. Cartilage calcifies, and a periosteal bone collar forms iii. The primary ossification center forms in the diaphysis iv. Secondary ossification centers form in the epiphyses v. Bone replaces cartilage, except the articular cartilage and epiphyseal plates vi. Epiphyseal plates ossify and form epiphyseal lines

Endosteum vs. Periosteum

· Endosteum i. Covers most internal surfaces of bones ii. Contains osteoprogenitor cells, osteoblasts, and osteocalsts · Periosteum i. Dense irregular connective tissue ii. Covers external surfaces of bones (except articular cartilage) iii. Anchored by perforating fibers embedded in the bone matrix iv. Acts as anchor for blood vessels and nerves v. Contains osteoprogenitor cells and osteoblasts

Hormones and Bone Growth

· Hormones alter the rates of osteoblast and osteoclast activity · Hormones also regulate calcium levels in the blood i. Bones are a strorage reservoir for calcium phosphate

exercise and bone tissue

· Mechanical stress stimulates increase in bone density by increased osteoblast activity · Bones of athletes become thicker and stronger as the result of repetitive and stressful exercise · Bones lose mass with age, but this can be slowed or reversed with weight bearing exercise

function of cartilage

· Supporting soft tissues · i.e. the airways in respiratory system & auricle of ear · Gliding surface at articulations · Smooth surfaces where bones meet · Precursor model for bone growth