Bone Composition and Fractures

What are the main components of the skeletal system?

bones, cartilage, ligaments, and other connective tissues

What are bones?

the primary organs of the skeletal system that form the rigid framework of the body

What are the main functions of bones?

protection, support, movement, blood cell production, and storage of minerals and energy

What are the two types of bone tissue?

compact and spongy bon

What is compact bone?

dense and solid, makes up 80% of bone mass

What is spongy bone?

porous and lightweight, makes up 20% of bone mass, founnd inside compact bone

What is cartilage?

semirigid connective tissue

How is cartilage different from bone?

more flexible than bone

What are the types of cartilage?

hyaline cartilage and fibrocartilage

What are the functions of hyaline cartilage?

attaches ribs to sternum, covers bone ends, found in growth plates, and acts as a model for bone formation

What are the functions of fibrocartilage?

weight-bearing and resists compression;found in intervertebral discs, pubic symphysis, and menisci of the knees

What are the main functions of bones?

support and protection, movement(levers),hemopoises-production of blood cells in red bone marrow, storage-calcium and phosphate for body functions

What are the four classifications of bones by shape?

long bones, short bones, flat bones, irregular bone

What is the shape of long bones?

longer than wide( e.g., femur, humerus)

What is the shape of short bones?

nearly equal in length and width (e.g., carpals, tarsals)

What is the shape of flat bones?

thin, flat, slightly curved (e.g., cranial bones)

What is the shape of irregular bones?

complex shapes (e.g., vertebrae)

What are the main regions of a long bone?

diaphysis, medullary cavity, epiphysis, articular cartilage, metaphysis

Describe diaphysis

shaft;provides leverage and support; mostly compact bone

Describe medullary cavity

hollow space inside the diaphysis containing bone marrow

Describe epiphysis

ends of the bone(proximal and distal);outer compact bone, inner spongy bone

describe articular cartilage

smooth hyaline cartilage covering joint surfaces

describe metaphysis

between diaphysis and epiphysis; contains the epiphyseal plate(growth plate)

What is the epiphyseal plate, and why is it important?

its a thi layer of hyaline cartilage that allows lengthwise growth in bones, in adults it becomes the epiphyseal line, fractures here in children can affect growth

What are the covering and linings of bone?

periosteum and endosteum

What is the periosteum?

outer covering of bone

What is the endosteum?

inner lining of medullary cavity

Where is red bone marrow found?

in spongy bone and medullary cavities in children; in axial skeleton in adult

What does Red bone marrow do?

produces blood cells(hemopoietic)

What does yellow bone marrow do, and where is it found?

fatty tissue formed from red marrow degeneration; stores fat and can revert to red marrow during severe anemia

What is a bone marrow transplant, and why is it needed?

used when bone marrow is destroyed by disease, radiation, or chemotherapy; healthyy marrow cells are injected into the recipient and migrate to bone tissue; donor and recipient must be genetic matches to prevent immune rejection

What are the four types of bone cells?

osteoprogenitor cells, osteoblasts, osteocytes, osteoclasts

What is the function of osteoprogenitor cells?

stem cells that produce osteoblasts

What is the function of osteoblasts?

build new bone and secrete osteoid

What is the function of osteocytes?

mature cells that maintain bone and detect stress

What is the function of osteoclasts?

break down and resorb bone tissue

What is an osteon?

the basic structural unit of compact bone

What is the function of a osteon?

provides strength and allows nutrient transport through canals

What are the parts of an osteon?

central canal(haversian canal), lamellae, lacunae, canalicula

What is the function of central canal(haversion canal)?

contains blood vessels and nerves

What is the function of Lamellae?

concentric rings of bone around the central canal

What is the function of lacunae?

small spaces holding osteocytes

What is the function of canaliculi?

tiny channels connecting lacunae for communication and nutrient transport

What are perforating canals(Volkmann’s Canals)?

canals that run perpendicular to central canals and connect different osteon

What is the structure and purpose of spongy bone?

made of trabeculae, which are thin rods and plates forming a lattice; bone marrow fills spaces between trabeculae; helps resists stress from many directions while keeping bones lightweight

What are the two types of cartilage growth?

interstitial growth and appositional growth

What is interstitial and appositional growth?

interstitial=growth in length(inside cartilage); appositional=growth in width(outside edge)

What is ossification(osteogenesis)?

the process of bone formation and development from embryonic tissue; begins around 8-12 weeks of embryonic development and continues into adolescence

What are the two types of ossification?

intramembranous and endochondral ossification

Describe intramembranous ossification

bone forms within a membrane; forms skull bones, facial bones, mandible, and middle of clavicle

Describe Endochondral ossification

bone forms from a hyaline cartilage model; produces most bones of the skeleton(limbs, pelvis, vertebrae, ends of clavicle)

What are the steps of long bone development(endochondral ossification)?

1. Fetal hyaline cartilage model develops

2. cartilage calcifies;periosteal bone collar forms

3. primary ossification center develops in the diaphysis

4. secondary ossification centers form in the epiphyses

5. Bone replaces cartilage(except at articular cartilage and growth plates)

6. Growth plates ossify and form epiphyseal lines

What is bone remodeling, and why is it important?

ongoing replacement of old bone tissue with new bone tissue;.about 20% of the skeleton is replaced yearly;depends on osteoblasts, osteocytes, and osteoclasts;influenced by hormones and mechanical stress(exercise and weight-bearing

Which hormones influence bone growth and remondeling?

growth hormone, thyroid hormone, sex hormones(estrogen and testosterone)

What does growth hormone stimulate?

cartilage growth in growth plates

What does the thyroid hormone do?

maintains normal bone growth

What do sex hormones do?

increase bone growth during puberty and cause growth plates closure

What are the effects of aging on bones?

1. decreased tensile strength-less protein made by osteoblasts→bones brittle

2. Loss of calcium and minerals:bones thinner and weaker→osteopenia and osteoporosi

What is osteopenia?

natural, age-related bone loss beginning at ages 35-40;osteoblast activity decreasees;osteoclast activity stays the same;common in vertebrae, jaw bones, and epiphyses;women lose more mass per decade than men

What is osteoporosis?

severe bone loss that compromises function and increases fracture risk;common in postmenopausal women due to decreased hormones; linked to aging, menopause, smoking, and caucasian race

What are the common fracture sites in osteoporosis?

wrist, hip, and vertebral column

How can osteoporosis be prevented?

healthy diet and regular physical activity during youth

How can osteoporosis be treated?

slow bone loss and stimulate new bone growth with medications

What are the three main types of bone fractures?

stress fracture, simple(closed) fracture, compound(open) fracture

Describe stress fracture

thin crack from overuse or increased activity

Describe simple(closed) fracture

bone breaks but doesn’t pierce the skin

Describe compound(open) fracture

bone pierces through the skin

What is the first step in bone fracture healing?

the formation of a hematoma, or blood clot, at the fracture site due to torn blood vessels

What happens during the formation of the fibrocartilaginous(soft) callus?

an internal callus forms inside the fracture, new blood vessels grow, and an external callus develops around the break to stabilize it

What forms after the soft callus stage?

a bony(hard) callus made of spongy bone trabeculae replaces the soft callus

What is the final stage of bone healing?

bone remodeling, where the new bone is reshapes and the fracture is fully healed

After a fracture heals, what remains at the site of injury?

the bone is slightly thicker at the healed area where the break occuured

What factors affect bone healing time?

the location, type of fracture, age, activity level, and bone quality of the person

What is calcification in bone repair?

the process where calcium and other minerals are deposited in the healing bone, making it hard and strong again

What is the difference between an open and closed fracture?

an open(compound) fracture breaks through the skin, while a closed(simple) fracture does not

What is the difference between a complete and incomplete fracture?

a complete fracture goes all the way through the bone, while an incomplete fracture only cracks partway through

What is a transverse fracture?

a break straight across the bone at a right angle, often caused by a sharp blow or repeated stress like running

What is a spiral fracture?

a fracture caused by a twisting force, wrapping around the bone-also called a torsion fracture

What is an oblique fracture?

a break that occurs at an angle across the bone

What is a comminuted fracture?

a fracture where the bone breaks into several fragments

What is a greenstick fracture and who gets it most often?

an incomplete fracture where the bone bends and cracks, common in children because their bones are more flexible

What is a stress fracture?

a hairline crack caused by overuse or repetitive motion, common in athletes

What is an impacted(buckle) fracture?

when the ends of the bone are pushed into each other, often from compression

What is an avulsion fracture?

when a piece of bone is pulled off by a tendon or ligament

What is a fissure fracture?

a crack in the bone that doesn’t go all the way through

What is the difference between displaced and non-displaced fractures?

displaced fractures have bone ends out of alignment; non-displaced fractures remain properly aligned

Which bones are most likely to break?

the ribs, wrist, fingers, toes, and collarbone

Why are leg bones less likely to break?

they are stronger because they must support body weight and absorb impact while walking or jumping

What factors determine how a fracture is treated?

the location, type, age of the person, activity level, and bone quality

What are non-surgical treatments for fractures?

casts, splints, or buddy taping(using a nearby finger or toe as a splint)

What are the two types of surgical treatments for fractures?

external fixation and internal fixation

What is external fixation?

metal rods or pins outside the body to hold the bone

What is internal fixation?

metal plates, rods, or screws inside the body to stabilize the bone

Why can’t casts be used on some parts of the body?

some areas, like moving joints, cannot be immobilized by casts. Fingers and toes are often using buddy taping instead.

What is the periosteum?

the periosteum is the outermost tissue layer covering a bone. it protects the bone, supplies it with blood vessels and nerves, and helps in bone growth and repair

What are the two layers of the periosteum?

outer layer=made of dense irregular connecive tissue containing blood vessels and nerves

inner layer=contains osteogenic cells that can be osteoblasts(bone builders) and osteoclasts(bone breakers)

What do perforating fibers do?

are collagen fibers that anchor the periosteum tightly to the bone’s surface

What are osteoblasts and what is their function?

are bone-building cells that secrete bone extracellular matrix(ECM), which harden to form new bone

What are osteoclasts and what is their function?

osteoclasts are large cells that break down bone tissue by releasing enzymes that digest the bone’s ECM

What is osseous tissue and where is it found?

osseous tissue(bone tissue) is found deep to the periosteum. It is made of hardened ECM and different bone cells, giving bone its strength and structure