Ch.5: The Skeletal System Flashcards
What are the parts of the skeletal system?
- Bones (skeleton)
- Joints
- Cartilages
- Ligaments
What are the two subdivisions of the skeleton?
- Axial skeleton
* Appendicular skeleton
What are the functions of bones?
• Support the body
• Protect soft organs
*Skull and vertebrae protect brain and spinal cord
*Rib cage protects thoracic cavity organs
• Attached skeletal muscles allow movement
• Store minerals and fats
*Calcium and phosphorus
*Fat in the internal marrow cavity
• Blood cell formation (hematopoiesis)
The adult skeleton has how many bones?
206
What are the two basic types of osseous (bone) tissue?
• Compact bone *Dense, smooth, and homogeneous • Spongy bone *Small needlelike pieces of bone *Many open spaces
Bones are classified on the basis of shape into which four groups?
- Long
- Flat
- Short
- Irregular
What are the properties of long bones?
• Typically longer than they are wide
• Shaft with enlarged ends
• Contain mostly compact bone; spongy bone at ends
• All of the bones of the limbs (except wrist, ankle, and kneecap bones) are long bones
• Examples:
*Femur
*Humerus
What are the properties of flat bones?
• Thin, flattened, and usually curved • Two thin layers of compact bone sandwich a layer of spongy bone between them • Examples: *Most bones of the skull *Ribs *Sternum
What are the properties of short bones?
• Generally cube-shaped
• Contain mostly spongy bone with an outer layer of compact bone
• Sesamoid bones are a type of short bone that form within tendons (patella)
• Examples:
*Carpals (wrist bones)
*Tarsals (ankle bones)
What are the properties of irregular bones?
• Irregular shape • Do not fit into other bone classification categories • Examples: *Vertebrae *Hip bones
Concept Link 1
As we learn about the structure and organization of bones, remember the levels of structural organization (Figure 1.1, p. 3). Bones are organs, so they contain not only osseous tissue but also other connective tissues: fibrous tissue, cartilage, adipose tissue, and blood.
What is the diaphysis (shaft) in the anatomy of a long bone?
- Makes up most of bone’s length
* Composed of compact bone
What is the periosteum in the anatomy of a long bone?
- Outside covering of the diaphysis
- Fibrous connective tissue membrane
- Perforating (Sharpey’s) fibers secure periosteum to underlying bone
What is the epiphysis (ends) in the anatomy of a long bone?
• Composed mostly of spongy bone enclosed by thin layer of compact bone
What is the articular cartilage in the anatomy of a long bone?
- Covers the external surface of the epiphyses
- Made of hyaline cartilage
- Decreases friction at joint surfaces
What is the epiphyseal line in the anatomy of a long bone?
- Remnant of the epiphyseal plate
* Seen in adult bones
What is the epiphyseal plate in the anatomy of a long bone?
- Flat plate of hyaline cartilage seen in young, growing bone
- Causes lengthwise growth of a long bone
What is the endosteum in the anatomy of a long bone?
- Lines the inner surface of the shaft
* Made of connective tissue
What is the medullary cavity in the anatomy of a long bone?
- Cavity inside the shaft
- Contains yellow marrow (mostly fat) in adults
- Contains red marrow for blood cell formation in infants until age 6 or 7
What are bone markings?
- Sites of attachments for muscles, tendons, and ligaments
* Passages for nerves and blood vessels
What are the categories of bone markings?
• Projections or processes—grow out from the bone surface
*Terms often begin with “T”
• Depressions or cavities—indentations
*Terms often begin with “F”
What is the microscopic anatomy of spongy bone?
- Composed of small, needlelike pieces of bone called trabeculae and open spaces
- Open spaces are filled by marrow, blood vessels, and nerves
What is the microscopic anatomy of compact bone?
- Osteocytes
- Lacunae
- Lamellae
- Central (Haversian) canal
- Osteon (Haversian system)
- Canaliculi
- Perforating (Volkmann’s) canal
What are osteocytes?
Mature bone cells situated in bone matrix
What are lacunae?
Cavities in bone matrix that house osteocytes
What are lamellae?
Concentric circles of lacunae situated around the central (Haversian) canal
What is a central (Haversian) canal?
- Opening in the center of an osteon (Haversian system)
- Runs lengthwise through bone
- Carries blood vessels and nerves
What is an osteon (Haversian system)?
- A unit of bone containing central canal and matrix rings
* Structural and functional unit of compact bone
What are canaliculi?
- Tiny canals
- Radiate from the central canal to lacunae
- Form a transport system connecting all bone cells to a nutrient supply
What is a perforating (Volkmann’s) canal?
- Canal perpendicular to the central canal
* Carries blood vessels and nerves
Bone is relatively lightweight and resists:
Tension and other forces
Organic parts (collagen fibers) of the bone make bone flexible and have great:
Tensile strength
Calcium salts deposited in the bone make bone hard to:
Resist compression
What is ossification?
- The process of bone formation
* Occurs on hyaline cartilage models or fibrous membranes
What are the two major phases of ossification in long bones?
- Osteoblasts (bone-forming cells) cover hyaline cartilage model with bone matrix
- In a fetus, the enclosed cartilage is digested away, opening up a medullary cavity
By birth, most cartilage is converted to bone except for which two regions in a long bone?
- Articular cartilages
- Epiphyseal plates
• New cartilage is formed continuously on the external face of these two cartilages
• Old cartilage is broken down and replaced by bony matrix
What is appositional growth?
- Bones grow in width
- Osteoblasts in the periosteum add bone matrix to the outside of the diaphysis
- Osteoclasts in the endosteum remove bone from the inner surface of the diaphysis
- Bone growth is controlled by hormones, such as growth hormone and sex hormones
Bones are remodeled throughout life in response to which two factors?
- Calcium ion level in the blood determines when bone matrix is to be broken down or formed
- Pull of gravity and muscles on the skeleton determines where bone matrix is to be broken down or formed
What is involved in calcium ion regulation?
- Parathyroid hormone (PTH)
* Hypercalcemia (high blood calcium levels) prompts calcium storage to bones by osteoblasts
What is the function of parathyroid hormone (PTH)?
- Released when calcium ion levels in blood are low
- Activates osteoclasts (bone-destroying cells)
- Osteoclasts break down bone and release calcium ions into the blood
What is a fracture?
A break in a bone
What are the types of bone fractures?
- Closed (simple) fracture
* Open (compound) fracture
Closed (simple) fracture
A break that does not penetrate the skin
Open (compound) fracture
A broken bone that penetrates through the skin