Bone composition

–relatively dense connective bone tissue

–appears white, smooth, and solid

–80% of bone mass

Compact bone (dense or cortical bone)

–located internal to compact bone

–appears porous

–20% of bone mass

Spongy bone (cancellous or trabecular bone)

External surface composed of compact bone

Interior composed of spongy bone

also called diploë in flat skull bones

Lack a medullary cavity

Short, flat, and irregular bones

What is spongey bone called in the skull?

diploë

Functions of the skeletal system

supporting framework

It interacts with all other organ systems

The skeletal system is composed of dynamic living tissues

continually rebuilds and remodels itself

Bones of the skeleton

Cartilage

Ligaments

Other connective tissues

What are the primary components of the skeletal system?

Semi-rigid connective tissue

More flexible than bone

Cartilage

What are the types of cartilage?

Hyaline cartilage

Fibrocartilage

cartilage within growth plates

model for formation of most bones

Hyaline cartilage

weight-bearing cartilage that withstands compression

Fibrocartilage

Anchor bone to bone

Ligaments

Anchor muscle to bone

Tendons

Greater in length than width

Have elongated, cylindrical shaft (diaphysis)

Most common bone shape

Found in upper and lower limbs

e.g., arm, forearm, fingers, thigh, leg, toes

Vary in size

Long bones

What are some examples of long bones?

Femur

Tibia

Fibula

Humerus

Ulna

Radius

Metarsals (5 long bones in foot)

Metacarpals (5 long bones in hand)

Length nearly equal to width

Short bones

What are some examples of short bones?

carpal bones (wrist bones)

sesamoid bones, bones along tendons of muscles

patella (kneecap), largest sesamoid bone

What are the bones along tendons of muscles called?

sesamoid bones

What is the largest sesamoid bone?

patella (kneecap)

Flat, thin surfaces, may be slightly curved

Provide surfaces for muscle attachment

Protect underlying soft tissues

Form:

the roof of the skull

the scapulae

the sternum

the ribs

Have elaborate shapes

E.g., vertebrae, ossa coxae (hip bones)

E.g., several bones in the skull (ethmoid, sphenoid)

Flat bones

What do flat bones form?

roof of the skull

scapulae

sternum

ribs

What are the 2 types of bone marrow?

Yellow and red

–Hemopoietic (blood cell forming)

–Contains reticular connective tissue, immature blood cells, and fat

–In children,

•located in the spongy bone and medullary cavity of long bones

-In adults,

located in portions of axial skeleton

located in proximal epiphyses of humerus and femur

e.g., skull, vertebrae, ribs, sternum, ossa coxae

condition with reduced erythrocytes (red blood cells

Red bone marrow (myeloid tissue)

–Product of red bone marrow degeneration

–Fatty substance

–May convert back to red bone marrow

•may occur during severe anemia

•facilitates the production of additional erythrocytes

Yellow bone marrow

Yellow bone marrow can _____ back to red bone marrow

convert

When can yellow bone marrow occur?

During severe anemia

In Children where is red bone marrow located?

In the spongy bone and medullary cavity of long bones

In adults where is red bone marrow located?

In portions of axial skeleton

proximal epiphyses of humerus and femur

e.g., skull, vertebrae, ribs, sternum, ossa coxae

condition with reduced erythrocytes (red blood cells

What is the yellow line pointing to?

Red bone marrow

What is the yellow line pointing to?

Yellow bone marrow

Compact bone is composed of

osteons

–Small cylindrical structures

–Also known as Haversian systems

–Basic functional and structural unit of mature compact bone

–Oriented parallel to bone diaphysis

osteons

What are the Components of osteons?

Central canal

Osteocytes

Concentric lamellae

Canaliculi

Perforating canals (Volkmann canals)

cylindrical channel

lies at center of osteon and runs parallel to it

blood vessels and nerves traveling here

Central canal

What is inside the Central canal?

blood vessels and nerves

mature bone cells

found in small spaces between concentric lamellae (lacunae)

maintain bone matrix

Osteocytes

rings of bone connective tissue

surround the central canal

contain collagen fibers

oriented at an angle 90 degrees from previous and next lamellae

give bone part of its strength and resilience

Concentric lamellae

rings of bone

may run immediately internal to bone periosteum (external circumferential lamellae)

may run internal to the endosteum (internal circumferential lamellae)

run the entire circumference of bone

Circumferential lamellae

Internal to bone periosteum is called?

external circumferential lamellae

internal to the endosteum is called?

internal circumferential lamellae

may be components of compact bone between osteons

may be partially resorbed osteons

look like a “bite” taken out of them

Interstitial lamellae

tiny interconnecting channels within bone connective tissue

extend from each lacuna

travel through lamellae

connect to other lacunae and central canal

house osteocyte projections permitting intercellular contact

allow travel of nutrients, minerals, gases, and wastes between blood vessels and osteocytes

Canaliculi

Spongy Bone

open lattice of narrow rods and plates of bones

bone marrow filling spaces between

form a meshwork of crisscrossing bars

provide great resistance to stresses

Trabeculae

composed of bone matrix

osteocytes resting between lamellae

canaliculi radiating from lacunae

Parallel lamellae

What are the 2 aspects/ categories of Spongey bone?

Trabeculae and Parallel lamellae

What is the yellow line pointing to?

lacuna (with osteocyte)

What is the yellow line pointing to?

Osteon

What is the yellow line pointing to?

Central Canal

What is the yellow line pointing to?

Concentric lamellae

What is the yellow line pointing to?

Cuniculi

what is this?

Compact Bone

what is this?

Compact Bone