A&P - bone tissue

Osteology

the study of bone

What is the living skeleton composed of?

dynamic tissues, cells, and nerves and blood vessels

What are the functions of the skeleton?

1. support

limb bones and vertebrae support body

2. protection

brain and spinal cord

3. movement

limb movements

4. electrolyte balance

calcium and phosphate levels

5. acid-base balance

buffers blood pH

6. blood formation

What is normal blood pH?

7.35-7.45

What is the difference between bone and osseous tissue?

bone is composed of many tissues and bone marrow

osseous tissue is composed cells and living substance

Calcification

hardening process of bone

What are the bones according to shape?

• flat bones

sheet like and protect soft organs

• long bones

shaft like that produce movement

• short bones

rounded bones

• irregular bones

elaborate shapes

Sesamoid

bone embedded within a tendon

ex. all produced from stress except for patellar

Osteogenic cells

• stem cells

• highly active

function: divide to produce differentiated cells

Osteoblasts

• immature cells

• secrete hormone osteocalcin

function: bone forming cell that helps produce and build up matrix

Osteocytes

• former osteoblasts

• trapped in lacunae

function: build up bone with use of hormones

Osteoclasts

• multi-nucleated

• microvilli extensions

• ruffle border

function: reabsorb or dissolve bone

Canaliculi

little channels that connect lacunae

Organic matter

part of matrix

synthesized by osteoblasts

composed of collagen and protein complexes

function: gives resistance and bendability to bone

Inorganic matter

part of matrix

composed of calcium hydroxyapatite and other minerals

function: gives strength to bones

What is the ratio of organic to inorganic matter?

1/3 organic

2/3 inorganic

Compact bone

contains

• osteons

• dense

• central canals

• lamellae

ex. very solid

Spongy bone

contains

• spicules

• trabeculae

• bone marrow

What is the function of spongy bone?

provides strength with minimal weight

Flat bone

consists of two layers plate of compact bone sandwiching a middle layer of spongy bone (diploe)

ex. houses bone marrow

What are the components of long bones? (review)

• diaphysis

• epiphysis

• articular cartilage

• nutrient foramina

• periosteum

• endosteum

Diaphysis

long shaft of bone

Epiphysis

enlarged ends of bone

Medullary cavity

space in the diaphysis containing bone marrow

Articular cartilage

layer of hyaline cartilage covering joint surfaces

Bone marrow

a soft connective tissue that produces blood cells

Periosteum

external sheath covering most of bone

Red marrow

active bone marrow

located in every bone of child and trunk of adults (skull, ribs, sternum, vertebrae, heads of femur and humerus)

function: produces blood cells

Yellow marrow

inactive bone marrow

located in medullary cavity of long bones

infiltrates with fat and does not produce blood cells

Ossification

the formation of bone

Epiphyseal plate vs. line

plate is a growth zone in children allowing bone to lengthen

line is a scar in adults marking where plate used to be

What are the two methods by which bone develops?

• intramembranous

converts membranes to bones and produces flat bones of the skull

• endochondral

lengthens bones from hyaline cartilage and produces long bones

What are the zones of metaphysis (bone elongation)?

1. resting cartilage

typical histology

2. cell proliferation

division of chondrocytes

3. hypertrophy

cells eat and increase in size

4. calcification

lacunae lack cells

calcium deposits

5. bone deposition

accomplished by osteoblasts

Interstitial growth

growth from within

ex. cartilage growth by epiphyseal plate

Appositional growth

occurs at bone surface

ex. adding layers for thickness

Wolff’s law

states the form of bones is determined by mechanical stressors

ex. accomplished through osteoblasts and osteoclasts

What three things are responsible for the remodeling of bone?

• stress

• hormones

• diet

Mineral deposition

process in which calcium and other minerals are taken from blood and deposited in bone

ex. build up bone

Mineral resorption

process of dissolving bone and releasing minerals into the blood by osteoclasts

ex. dissolves bone

What is the normal concentration of calcium within the blood?

9.2-10.4 mg/dl

What three hormones regulate calcium homeostasis?

• calcitriol

• calcitonin

• parathyroid hormone

Hypocalcemia

deficient calcium within the blood

caused by vitamin D deficiency

ex. muscle spasms

Hypercalcemia

excessive calcium levels within the blood

rarely occurs

ex. flacidity or excessive relaxation of muscles

True or false, a mature bone remains a metabolically active one?

true

What maintains the homeostasis of minerals?

mineral deposition and resorption