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PowerPoint® Lecture Slide Presentation by Patty Bostwick-Taylor, Florence-Darlington Technical College

PART A 5

The Skeletal System

The Skeletal System §  Parts of the skeletal system

§  Bones (skeleton)

§  Joints

§  Cartilages

§  Ligaments

§  Two subdivisions of the skeleton

§  Axial skeleton – bones that form the longitudinal axis of the body

§  Appendicular skeleton – bones of the limbs and girdles.

Functions of Bones 1. Support the body

2. Protect soft organs

3. Allow movement due to attached skeletal muscles

4. Store minerals and fats (most important of which are calcium and phosphorous)

5. Blood cell formation (hematopoiesis)

Bones of the Human Body §  The adult skeleton has 206 bones

§  Two basic types of bone tissue

§  Compact bone

§  Dense and looks smooth

§  Homogeneous

§  Spongy bone

§  Small needle-like pieces of bone

§  Many open spaces

Figure 5.2b

Classification of Bones on the Basis of Shape

Figure 5.1

Classification of Bones §  Long bones

§  Typically longer than they are wide

§  Have a shaft with heads at both ends

§  Contain mostly compact bone

§  Example:

§  Femur

§  Humerus

** All the bones of the limbs, except the patella, carpals, and tarsals are long bones

Classification of Bones

Figure 5.1a

Classification of Bones §  Short bones

§  Generally cube-shape

§  Contain mostly spongy bone

§  Example:

§  Carpals

§  Tarsals

Figure 5.1b

Classification of Bones §  Sesamoid Bones (round bones)

§  Special type of short bone

§  Form within tendons

§  Best known example

§  Patella

Classification of Bones §  Flat bones

§  Thin, flattened, and usually curved

§  Two thin layers of compact bone surround a layer of spongy bone

§  Example:

§  Skull

§  Ribs

§  Sternum

Figure 5.1c

Classification of Bones §  Irregular bones

§  Irregular shape

§  Do not fit into other bone classification categories

§  Example:

§  Vertebrae

§  Hip bones

Figure 5.1d

Anatomy of a Long Bone Gross/Macroscopic Anatomy

§  Diaphysis

§  Shaft

§  Composed of compact bone

§  Epiphysis

§  Ends of the bone

§  Composed mostly of spongy bone

Anatomy of a Long Bone

Figure 5.2a

Anatomy of a Long Bone §  Periosteum

§  Outside covering of the diaphysis

§  Fibrous connective tissue membrane

§  Sharpey’s fibers/Perforating fibers

§  Secure periosteum to underlying bone

§  Arteries

§  Supply bone cells with nutrients

Figure 5.2c

Anatomy of a Long Bone §  Articular cartilage (articulate – join w/another bone)

§  Covers the external surface of the epiphyses

§  Made of hyaline cartilage

§  Decreases friction at joint surfaces

Anatomy of a Long Bone §  Epiphyseal plate/Growth plate

§  Flat plate of hyaline cartilage seen in young, growing bone

§  Epiphyseal line

§  Remnant of the epiphyseal plate

§  Seen in adult bones

Figure 5.2a

Anatomy of a Long Bone §  Medullary cavity

§  Cavity inside of the shaft

§  Contains yellow marrow (mostly fat) in adults

§  In infants this area forms blood cells and red marrow is found there

Figure 5.2a

Bone Markings §  Surface features of bones

§  Sites of attachments for muscles, tendons, and ligaments

§  Passages for nerves and blood vessels

§  Categories of bone markings

§  Projections or processes—grow out from the bone surface

§  Depressions or cavities—indentations

Bone Markings

Table 5.1 (1 of 2)

Bone Markings

Table 5.1 (2 of 2)

Microscopic Anatomy of Bone §  Osteon (Haversian system)

§  A unit of bone containing central canal and matrix rings

§  Central (Haversian) canal

§  Opening in the center of an osteon

§  Carries blood vessels and nerves

§  Perforating (Volkman’s) canal

§  Canal perpendicular to the central canal

§  Carries blood vessels and nerves from osteon to osteon

Microscopic Anatomy of Bone

Figure 5.3a

Microscopic Anatomy of Bone §  Lacunae

§  Cavities containing bone cells (osteocytes)

§  Arranged in concentric rings

§  Lamellae

§  Rings around the central canal

§  Sites of lacunae

Figure 5.3b–c

§  Canaliculi

§  Tiny canals

§  Radiate from the central canal to lacunae

§  Form a transport system connecting all bone cells to a nutrient supply

Figure 5.3b

Macro/Micro Labeling Diaphysis

Periosteum Central (Haversian) canal

Epiphyseal plate/line Canaliculus

Epiphysis Lacuna

Compact bone Osteocyte

Spongy bone Perforating (Volkman’s) canal

Medullary cavity Lamella

Yellow/Red bone marrow Osteon (Haversian system)

Articular cartilage

Formation of the Human Skeleton §  In embryos, the skeleton is primarily hyaline

cartilage

§  During development, much of this cartilage is replaced by bone

§  Cartilage remains in isolated areas

§  Bridge of the nose

§  Parts of ribs

§  Joints

Bone Growth (Ossification) §  Epiphyseal plates allow for lengthwise growth of

long bones during childhood

§  New cartilage is continuously formed

§  Older cartilage becomes ossified

§  Cartilage is broken down

§  Enclosed cartilage is digested away, opening up a medullary cavity

§  Bone replaces cartilage through the action of osteoblasts

Bone Growth (Ossification) §  Bones are remodeled and lengthened until growth

§  Bones are remodeled in response to two factors

§  Blood calcium levels

§  Pull of gravity and muscles on the skeleton

§  Bones grow in width (called oppositional growth)

Long Bone Formation and Growth

Figure 5.4a

Bone starting to replace cartilage

Epiphyseal plate cartilage

Articular cartilage

Spongy bone

In a child In a fetus In an embryo

New bone forming

Growth in bone width

Growth in bone length

New bone forming

Blood vessels

Hyaline cartilage

New center of bone growth

Medullary cavity

Bone collar Hyaline cartilage model

Figure 5.4a, step 1

In an embryo

Figure 5.4a, step 2

In a fetus In an embryo

Blood vessels

Hyaline cartilage

Medullary cavity

Figure 5.4a, step 3

Articular cartilage

Spongy bone

In a child In a fetus In an embryo

New bone forming

Growth in bone width

New bone forming

Blood vessels

Hyaline cartilage

Medullary cavity

Figure 5.4b

Types of Bone Cells §  Osteocytes—mature bone cells

§  Osteoblasts—bone-forming cells

§  Osteoclasts—bone-destroying cells

§  Break down bone matrix for remodeling and release of calcium in response to parathyroid hormone

§  Bone remodeling is performed by both osteoblasts and osteoclasts

**HOMEOSTATIC IMBALANCE**

- Rickets - a disease in children in which bones fail to calcify

- bones soften and show bowing

- due to a lack of calcium or vitamin D

Bone Fractures §  Fracture—break in a bone §  Types of bone fractures

§  Closed (simple) fracture—break that does not penetrate the skin

§  Open (compound) fracture—broken bone penetrates through the skin

§  Bone fractures are treated by §  reduction – realignment of bone ends, and §  immobilization – by cast or traction

common types of fractures: 1.  Comminuted - bone breaks into many fragments

2.  Compression - bone is crushed

3.  Depressed - broken bone portion is pushed inward

4.  Impacted - broken bone ends are forced into each other

5.  Spiral - ragged break occurs when excessive twisting forces are applied to a bone

6. Greenstick - bone breaks incompletely, like a green twig breaks

Common Types of Fractures

Table 5.2

Repair of Bone Fractures §  Hematoma (blood-filled swelling) is formed

§  Break is splinted by fibrocartilage to form a callus

§  Fibrocartilage callus is replaced by a bony callus

§  Bony callus is remodeled to form a permanent patch (bone remodeling)

Stages in the Healing of a Bone Fracture

Figure 5.5

Hematoma External callus

Bony callus of spongy bone

Healed fracture

New blood vessels

Internal callus (fibrous tissue and cartilage)

Spongy bone trabecula

Hematoma formation

Fibrocartilage callus formation

Bony callus formation

Bone remodeling

Figure 5.5, step 1

Hematoma

Hematoma formation

Figure 5.5, step 2

New blood vessels

Hematoma formation

Figure 5.5, step 3

New blood vessels

Hematoma formation

Figure 5.5, step 4

Healed fracture

New blood vessels

Hematoma formation

Bone remodeling

II. Joints - joints are also called articulations

-  2 functions are to join bones together securely but also give the rigid skeleton mobility

A. Functional Classification of Joints:

1. Synarthroses - immovable joints

2. Amphiarthroses - slightly movable joints

3. Diarthroses - freely movable joints

B.  Structural Classification of Joints:

1. Fibrous joints - bones are united by fibrous/dense connective tissue

- examples – sutures of the skull

2.  Cartilaginous joints- bone ends are connected by cartilage

- examples: pubic symphysis of the pelvis (amphiarthrotic)

- intervertebral joints of the spinal column

- joints between the first ribs and the sternum (synarthrotic)

3.  Synovial joints

- articulating bone ends are separated by a joint cavity containing synovial fluid

- synovial joints account for all joints in the limbs

C. Types of Synovial Joints Based on Shape 1.  Plane joint

- articular surfaces are flat

- only short slipping & gliding movements are allowed

- examples: intercarpal and intertarsal joints

2.  Hinge joint

- cylindrical end fits into trough-shaped end of another bone

- examples: elbow joint, knee joint, and joints between the phalanges of the fingers

3.  Pivot joint

- rounded end of one bone fits into sleeve or ring of bone

- examples: proximal radioulnar joint and the first two vertebrae – atlas and axis

4.  Condyloid joint

- egg-shaped articular surface of one bone fits into oval concavity of another bone

- examples: metacarpophalangeal joints/knuckles

5.  Saddle joint

- each articular surface has both concave & convex surfaces

- examples: carpometacarpal joints in the thumb

6.  Ball-and-Socket joint

- spherical head of one bone fits into a round socket in another

- examples: shoulders and hips

**HOMEOSTATIC IMBALANCES** 1.  Bursitis - inflammation of the bursae or synovial

membranes

2.  Sprain- when the ligaments or tendons reinforcing a joint are damaged by excessive stretching or are torn away from the bone – poorly vascular

**HOMEOSTATIC IMBALANCES** 3.  Arthritis - inflammation of the joints/pain, stiffness, and

swelling of the joint

- most widespread progressive disease in the US

4.  Osteoarthritis - chronic degenerative condition typically affecting the aged

- over the years, the cartilage softens, frays, and eventually breaks down

- most common in the fingers, cervical & lumber joints of the spine, and the large weight-bearing joints of the lower limbs (knees & hips)

**HOMEOSTATIC IMBALANCES** 5.  Rheumatoid Arthritis - chronic inflammatory disorder

- affected joints are in the fingers, wrists, ankles, and feet in a symmetrical manner

- RA is an autoimmune disorder - a disorder in which the body's immune system attempts to destroy its own tissues

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