A and P chapter 6 bones

before 8 weeks of development the fetal skeleton is composed of ?

hyaline cartilage and fibrous membranes

After 8 weeks of development the fetal skeleton is composed of ?

bone

By adulthood what is the human body composed of ?

Bone and Cartilage at the Joints

Skeleton cartilage

• contains no blood vessels

• hugh perecnt of water - give resiliency

• surrounded by the perichondrium (dense irregular tissue) that resists outward expansion

Skeletal cartilage types (3)

•Hyaline – support/flexibility, most abundant

•Elastic – takes repeated bending

•Fibrocartilage – e.g.intervertebral discs

Appositonal

cells of perichondrium secrete matrix; growth from outside edge

Interstitial

lacunae-bound chondroblasts; expanding the cartilage from within

Calcification of cartilage occurs ….?

•During normal bone growth

•During old age

Functions of the bones

§Support - form the framework that supports the body and cradles the soft organs

§Protection - provide a protective case for the brain, spinal cord, and vital organs

§Anchorage- muscle to bone (levers)

§Mineral storage - reservoir for minerals, especially calcium and phosphorus

§Blood cell formation - hematopoiesis occurs within the marrow cavities of bones

§Fat storage – yellow marrow

§Hormone production – osteocalcin

•Regulates insulin release, glucose homeostasis

levels of bone structure

•Gross

•Microscopic

•Chemical

structure of bone

•Bone

•Cartilage

•Nerve

•Fibrous connective

Epithelial and smooth muscle

Gross anatomy of bones : markings

•Bulges, depressions, and holes (Table 6.1) that serve as:

wSites of attachment for muscles, ligaments, and tendons

wJoint surfaces

wPassages for blood vessels and nerves

Gross anatomy of bones: textures

•Compact bone – dense outer layer

•Spongy bone – honeycomb of trabeculae filled with red or yellow bone marrow

Diaphysis

• the tubular shaft of long bones

•Compact bone surrounds the medullary cavity

Medullary cavity

cavity that contains yellow bone marrow

Epiphyses

§ Ends of long bones

•Exterior compact bone, interior spongy bone

•Joint surface is covered with articular (hyaline) cartilage

Epiphyseal line

separates diaphysis and epiphyses

articular cartilage

Joint surface is covering

(made of hyaline cartilage )

Periosteum

outer membrane

• The outer fibrous layer is dense, irregular connective tissue

•Inner osteogenic layer (osteoblasts, osteoclasts)

•Richly supplied with nerve fibers, blood, and lymphatic vessels

•Secured to the bone by perforating fibers (strongest at tendon/ligament attachment)

Endosteum

internal surfaces of bone

tendons

attach bone to muscle

ligaments

attach bone to bone

Location of hematopoietic tissue (Red marrow)

IN INFANTS

•Found in the medullary cavity and all areas of spongy bone

Location of hematopoietic tissue (Red marrow)

IN ADULTS

•Found in the spongy region (diploë) of flat bones, some irregular bones, and the head of the femur and humerus

The chemical composition of the bone

ORGANIC PORTION

§Cells - living

§Osteogenic 

§Osteoblasts

§Osteocytes

§Osteoclasts

§Osteoid (35% by mass) - non living

§Collagen fibers ( between lamella)

§Proteoglycans, glycoproteins

Osteogenic cell

synthesis bone ; stem cell

Osteoblasts

make up the majority of the matrix

• cell responsible for bone growth

• cell that creates bone

Osteocytes

maintain the matrix

• matured bone cells that maintain the mineralized bone matrix

Osteoclasts

break down the matrix

• breaks down the bone for calcium

• bone resorbing cell

what do Collagen fibers, proteoglycans and glycoproteins provide to the bone?

• flexibility

• hydration

*glycoproteins are a polar nature that attaches water and hydrates the bone

Chemical composition of bone

INORGANIC PORTION

§Mineral salts (65% by mass)

§Mainly calcium phosphates

§Responsible for bone hardness and its resistance to compression

Formation of bony skeleton occurs…?

Before birth

Bone growth occurs..?

Until early adulthood

Remodeling and repair of bone occurs…?

As adults

Intramembranous ossification

*Hardening of tissue

§bone develops from a fibrous membrane(perichondrium ) formed from mesenchyme

•All flat bones of the skull, clavicles

(outside —— in)

Endochondral ossification

*hardening of bone tissue

§bone forms by replacing hyaline cartilage

Majority of bone formation

(inside —— out)

§Growth in length of long bones

•Elongation occurs at the epiphyseal plate, bone grows toward diaphysis

•Epiphyseal plates are eventually replaced by bone tissue once growth in length has stopped (~18 in females, ~21 males)

Epiphyseal plates

• where cartilage cell divides, and is replaced by bone

§Growth in thickness throughout life

Appositional growth (outside —- inside)

• cells lining inner periosteum

Hormonal control

•Growth hormone, thyroid hormone

•Steroid hormones (sex hormones during adolescence)

Bone Remodeling (change in shape and density)

§consists of both deposit and resorption of bone tissue.

•Occurs during growth and throughout life

•Controls on remodeling

wCa+ levels in blood

wMechanical and gravitational forces

Blood Ca levels are regulated calcitonin and parathyroid hormone (PTH)

Bone fractures are classified by:

•The position of the bone ends after fracture

•The completeness of the break

•The orientation of the break to the long v.s short axis

•Whether or not the bones ends penetrate the skin

Nondisplaced bone fracture

bone ends retain their normal position.

Displaced bone fracture

§bone ends are out of normal alignment

Complete fracture

broken all the way through.

*Referring to a break

Incomplete fracture

not broken all the way through

*Referring to a break

Linear fracture

parallel to the long axis of the bone

• looks like when you are cutting sub-bread

Transverse fracture

along transverse plane

• can cause an infection and infect the red blood cells (which is more dangerous because infection can spread to whole body)

Compound( open) fracture

§bone ends penetrate the skin

simple ( close) fracture

bone ends do not penetrate the skin

Comminuted fracture

bone is broken into 3 or more pieces.

• commonly found in old people who have brittle bone.

• long and short bones are mostly affected

Compression fracture

bone is crushed

• vertebral and knee bone are mostly affected

epiphyseal fracture

• only happens in long bone

• when epiphysis separates from the diaphysis along the epiphyseal plate

spiral fracture

ragged break that occurs when excessive twisting forces are applied to the bone

Depressed fracture

• broken broke portion is pressed inward

• typical fracture for the skull

Greenstick fracture

bone breaks incompletely.

one side of the shaft breaks, while the other side bends

• commonly occurs in children because of the amount of water in their bones.

Closed reduction

•Broken ends are manipulated back into place without surgery

Open reduction

•Fragments are exposed by surgery and fixed in place with hardware

Stages in healing of a bone

1) hematoma forms

2) fibrocartilaginous callous forms

3) bony callus forms

4) bone remodeling occurs

Osteoporosis

•Group of diseases in which bone reabsorption outpaces bone deposit

•Spongy bone of the spine is most vulnerable

•Occurs most often in postmenopausal women

•Bones become so fragile that sneezing or stepping off a curb can cause fractures

osteomalacia

• mostly affects adults

• •Bones are inadequately mineralized causing softened, weakened bones

  •Main symptom is pain when weight is put on the affected bone

  •Caused by insufficient calcium in the diet, or by vitamin D deficiency

Rickets

is osteomalacia but in children

•Bones of children are inadequately mineralized causing softened, weakened bones

•Bowed legs and deformities of the pelvis, skull, and rib cage are common

•Caused by insufficient calcium in the diet, or by vitamin D deficiency

Paget’s disease

§Excessive bone formation and breakdown: uncontrolled remodeling

§Pagetic bone  = excessively high ratio of spongy to compact bone is formed

•Weaker than normal bone

§Osteoclast activity wanes, but osteoblast activity continues to work

§Often affects the spine, pelvis, femur, and skull

§Unknown cause (possibly viral)

§Treatment includes bisphosphonate drugs and calcitonin

Osteosarcoma

homeostatic imbalance

• uncontrolled growth of malignant tissue

• primarily in children and young adults

Gorham-Stout Syndrome (Vanishing Bone DO)

Progressive bone loss (osteolysis)

Commonly affected areas: ribs, spine, pelvis, skull, collarbone (clavicle), and jaw

Symptoms: pain and swelling, disfigurement and functional disability of affected areas. Severity varies.

Cause unknown