Chapter 7: Bone Tissues

What is the skeletal system?

Body's framework

Parts: Bones, Ligaments, Cartilage, Tendons

Bones

Primary Organs

Ligaments

Holds bones together at joints

Cartilage

Forerunner for most bones, covers joint surfaces

Tendons

Attach muscles to bones (movement.)

Osteology

Study of Bone

Skeletal System Functions

Support, Protection, Movement, Electrolyte Balance, Acid-Base Balance, Blood Formation, Hormone Secretion

The body is supported by ___

Limb bones and vertebrae

Teeth are supported by ____

Jaw Bones

Skeletal System Protection

Protects brain, spinal cord, heart, lungs

Skeletal System Movement

Muscle action -> limb movements and breathing.

Sketetal System Electrolyte Balance

Stores and releases calcium and phosphate ions.

Skeletal System Acid-Base Balance

Buffers blood by altering phosphate and carbonate salt levels.

Skeletal System Blood Formation

Red bone marrow is the primary producer of blood cells

Skeletal System Hormone Secretion

Osteocalcin: Affects insulin action

Bone as a Tissue (Osseous)

Connective, has matrix -> hardened by calcium phosphate

Mineralization

Hardening of Bone

Bone as an Organ

Has Tissues : Bone Adipose, Nervous, Fibrous CT,

Other Components: Marrow, Cartilage

Long Bones

Longer than they are wide (movement)

Examples of Long Bones

femur, humerus

Flat Bones

Thin, curved plates (protection for soft organs)

Examples of Flat Bones

Parietal skull, ribs, sternum

Flat Bone Structure

Sandwich of spongy bone (diploe) between compact bone

Short Bones

Equal in width and height

Examples of Short Bones

Wrist, ankle

Irregular Bones

Don't fit other categories

Examples of Irregular Bones

Vertebrae

Compact (Cortical) Bone

Dense outer shell, encloses marrow cavity (strength)

The skeleton is _____ compact bone by weight

Three-fourths

Spongy (Cancellous) Bone

Loosely organized osseous tissue

Diaphysis

Shaft, provides leverage

Epiphysis

Enlarged end, strengthens joints, anchors ligaments and tendons

Epiphyseal Line

Childhood growth zone

Articular Cartilage

Layer of hyaline cartilage covers joint surface (movement)

Nutrient Foramina

Minute holes on bone surface, allows blood vessels to penetrate

Endosteum

Reticular connective tissue, lines internal bone

Periosteum

External sheath, covers most bone

Osteogenic Cells

Stem cells, gives rise to osteoblast

Osteoblasts

Bone-forming cells (osteogenesis)

Osteocytes

Former Osteoblasts, trapped in matrix

Lacunae

Tiny cavities where osteocytes live

Canaliculi

Channels that connect lacunae

Osteoclasts

Bone-destroying cells (osteolysis)

Matrix

Composite material, Organic and Inorganic matter

Organic Matter

1/3 dry weight, collagen

Inorganic Matter

2/3 dry weight, calcium

Compact Bone

Matrix surrounds central (haversian) canal, runs longitudinally

Circumferential Lamellae

Outer and inner surfaces of the bone

Interstitial Lamellae

Fills irregular regions between osteons

What is spongy bone made of?

A lattice of spicules and trabeculae

How does spongy bone align?

It aligns with lines of stress

What fills the spaces in spongy bone?

Red bone marrow

Red Bone Marrow (Myeloid Tissue)

Hematopoietic -> makes blood cells

Yellow Bone Marrow

Fatty marrow (adults), can transform to red (anemia)

Ossification

Formation of bone

Intramembranous Ossification

Produces flat bones of skull and clavicle -> lifelong thickening and remodeling of long bones

Endochondral Ossification

Transforming hyaline cartilage into bone.

Which bones are made from endochondral ossification?

Limbs, vertebrae

Bone Elongation

Growth in height

Epiphyseal Plate

Growth Zone

Metaphysis

Cartilage replacement zone

Interstitial Growth

Cartilage growth from within

Epiphyseal Line

Site of og epipyseal plate

Achondroplastic Dwarfism

Long bones stop growing in childhood (normal torso, short limbs)

Pituitary Dwarfism

Lack of growth hormone (short with normal proportions)

Appositional Growth

Growth in thickness, deposition of new tissue at bone surface

Wolff's Law of Bone

Bone architecture determined by mechanical stresses placed on it

Mineralization (Mineral Deposition)

Ions taken from blood and deposited, (osteoblasts)

Mineral Resorption (Dissolving bone)

(Osteoclasts), Hydrochloric acid dissolves minerals, which are released into blood

Hypocalcemia

Calcium deficiency, excessive excitability

Hypercalcemia

Calcium excess, less excitability

Calcitriol

Forms vitamin D

Why do we need calcitriol?

Low calcitriol results in soft bones

Children (rickets)

Osteomalacia (adults)

Calcitonin

Lowers blood calcium concentration

Osteoclast Inhibition

Reduces bone resorption active in children

Osteoblast Stimulation

Deposit calcium into bone

Parathyroid Hormone (PTH)

Secreted by parathyroid glands, reponds to low calcium

Phosphate Homeostasis

500-800 g

Orthopedics

Branch of medicine for prevention and correction of disorders in bones, joints, and muscles

Stress Fracture

Abnormal trauma to bone

Pathological Fracture

Bone weakened by disease

Hematoma Formation

Blood clot -> granulation tissue

Soft Callus Formation

deposition of collagen and fibrocartilage converts granulation tissue to soft callus

Hart Callus Formation

Osteoblasts deposit a bony collar, unite broken pieces while ossification occurs

Bone Remodeling

Small bone fragments removed by osteoclasts, osteoblasts deposit spongy bone, converts into compact bone

Closed Reduction

Bone manipulated to normal position without surgery.

Open Reduction

Surgery (plates, screws, pins)

Osteopenia

Decline in bone density

Osteoporosis

Severe loss of bone density

Electrical Stimulation

Use for fractures that take long to heal, suppresses effects of parathyroid hormone.