Skeletal Flashcards
Health Science
What is the origin of the word ‘skeleton’?
It comes from the Greek word meaning ‘dried-up body’.
What are the two main functions of the skeleton?
Protecting the body’s internal organs and allowing movement.
Which part of the skeleton provides support for soft organs?
The bones, acting as the internal ‘steel frame’ of the body.
Besides bones, what other components are included in the skeletal system?
- Joints
- Cartilages
- Ligaments
How is the skeleton divided?
- Axial skeleton (longitudinal axis)
- Appendicular skeleton (limbs and girdles)
What does the axial skeleton consist of?
Bones that form the longitudinal axis of the body (e.g., skull, vertebral column, rib cage).
What does the appendicular skeleton consist of?
Bones of the limbs and the girdles that attach them to the axial skeleton.
Name three functions of the skeletal system.
- Support
- Protection
- Allowing movement
What are the four main classifications of bones by shape?
- Long
- Short
- Flat
- Irregular
How does the term ‘bag of bones’ misrepresent the skeleton?
It inaccurately implies fragility and lack of structure, whereas bones are strong and dynamic.
What role do bones play in movement?
They act as levers for muscles, allowing movement of the body and its parts.
How do bones store fat?
Fat is stored in the internal marrow cavities.
What minerals are primarily stored in the bones?
- Calcium
- Phosphorus
Why is it important for a small amount of calcium to remain in ionic form in the blood?
It is necessary for nerve transmission, muscle contraction, and blood clotting.
What is hematopoiesis?
The formation of blood cells, which occurs in the marrow cavities of certain bones.
Approximately how many bones are in the adult human skeleton?
206 bones.
What are the two types of osseous tissue found in bones?
- Compact bone
- Spongy bone
How does compact bone appear compared to spongy bone?
Compact bone is dense, smooth, and homogeneous; spongy bone has an open, spiky appearance.
What characterizes long bones?
They are longer than they are wide, have a shaft with enlarged ends, and are mostly composed of compact bone with spongy bone at the ends.
Which bones in the limbs are typically long bones?
All except the patella (kneecap) and the wrist and ankle bones.
What defines flat bones?
They are thin, flattened, usually curved, and have two layers of compact bone with a layer of spongy bone in between.
Where are most flat bones found?
In the skull, ribs, and sternum.
What are short bones and where are they primarily found?
Short bones are generally cube-shaped with mostly spongy bone and an outer layer of compact bone; they are found in the wrist and ankle.
What are sesamoid bones?
Bones that form within tendons, with the patella being the best-known example.
What are irregular bones?
Bones that do not fit into the long, short, or flat categories, such as the vertebrae.
What is the primary function of the periosteum?
It is a fibrous connective tissue membrane that covers and protects the outer surface of bones.
What are Sharpey’s fibers?
Connective tissue fibers that attach the periosteum firmly to the underlying bone.
What is the diaphysis of a long bone?
The shaft or main midsection of the bone, composed mainly of compact bone.
What are the epiphyses of a long bone?
The expanded ends of a long bone that are filled with spongy bone and covered with articular cartilage.
What covers the epiphyses instead of a periosteum?
Articular cartilage, which is composed of hyaline cartilage.
What is the epiphyseal line?
A remnant of the epiphyseal plate, seen in adult bones after the plate has been replaced by bone.
What is the epiphyseal plate and its function?
A plate of hyaline cartilage in growing bones that allows for lengthwise growth; it is later replaced by bone.
What is the medullary cavity?
The central cavity of a long bone that stores marrow.
What is the endosteum?
A delicate connective tissue lining the inner surface of the bone’s medullary cavity.
What is the difference between red marrow and yellow marrow?
- Red marrow produces blood cells
- Yellow marrow stores adipose tissue and replaces red marrow in long bones as a person ages.
What are bone markings?
Bumps, holes, and ridges on the bone surface that serve as attachment sites for muscles, tendons, ligaments, or passageways for blood vessels and nerves.
What are the two categories of bone markings?
- Projections (or processes)
- Depressions (or cavities)
What is a projection on a bone?
A raised area that serves as an attachment point for muscles or ligaments (all terms beginning with T are projections).
What is a depression on a bone?
An indentation or cavity that often serves as a passageway for blood vessels or nerves (most terms beginning with F, except ‘facet,’ are depressions).
What are trabeculae?
Small, needlelike pieces of bone that form the network in spongy bone.
What is an osteon (or Haversian system)?
The structural and functional unit of compact bone, consisting of concentric lamellae arranged around a central canal.
What runs through the center of an osteon?
A central (Haversian) canal that carries blood vessels and nerves.
What are lacunae in bone tissue?
Tiny cavities within the bone matrix where osteocytes (mature bone cells) reside.
What are lamellae?
Concentric rings of bone matrix in compact bone.
What are canaliculi?
Tiny canals that radiate from the central canals to connect lacunae, facilitating nutrient and waste exchange between bone cells.
What is the function of Volkmann’s canals?
They are perforating canals that connect central canals and allow blood vessels and nerves to pass between them.
How do calcium salts and collagen fibers contribute to bone properties?
- Calcium salts give bones hardness (resistance to compression)
- Collagen fibers provide flexibility and tensile strength.
What is ossification?
The process of bone formation from cartilage or fibrous membranes.
During embryonic development, what is the primary tissue forming the skeleton?
Hyaline cartilage.
What cells are responsible for building bone matrix?
Osteoblasts.
In bone formation, what is the ‘bone collar’?
A layer of bone matrix that forms around the hyaline cartilage model during early ossification.
What process replaces the cartilage model in the fetus with bone?
Endochondral ossification.
What happens to the center of the cartilage model during bone development?
It is digested away, forming a medullary cavity.
By birth, what regions still retain cartilage in a developing bone?
- The articular cartilages
- The epiphyseal plates
How do long bones grow in length?
Through the continuous formation of new cartilage at the epiphyseal plate and its replacement by bone.
What is appositional growth?
The process by which bones widen in diameter as new bone is added to the periosteum and removed from the endosteum.
Which cells add bone matrix to the outside of the diaphysis during appositional growth?
Osteoblasts in the periosteum.
Which cells remove bone from the inner surface to enlarge the medullary cavity?
Osteoclasts in the endosteum.
What hormones are most important in controlling bone growth?
- Growth hormone
- Sex hormones during puberty
Is bone a static or dynamic tissue?
Bone is dynamic and constantly remodeled throughout life.
What are the two main factors that stimulate bone remodeling?
- Changes in the blood calcium ion level
- Mechanical stresses from gravity and muscle pull
What hormone is released when blood calcium levels drop?
Parathyroid hormone (PTH).
What effect does parathyroid hormone (PTH) have on bones?
It activates osteoclasts to break down bone matrix, releasing calcium into the blood.
How is excess calcium in the blood managed by bones?
Osteoblasts deposit the excess calcium into the bone matrix as hard calcium salts.
How does bone remodeling help maintain proper bone proportions?
It adjusts the bone structure in response to growth, weight gain, and mechanical stresses.
What happens to the bones of physically inactive or bedridden individuals?
They tend to lose mass and atrophy due to reduced mechanical stress.
What is the role of osteocytes in bone tissue?
They are mature bone cells that maintain the bone matrix and communicate via canaliculi.
What happens to osteoblasts once they become trapped in the matrix they secreted?
They become osteocytes.
What is rickets?
A childhood disease characterized by softened, weakened bones due to inadequate calcification.
What are common causes of rickets?
- A lack of dietary calcium
- Vitamin D deficiency
Why is vitamin D important for bone health?
It is needed to absorb calcium into the bloodstream.
What typical bone deformity is seen in children with rickets?
Bowed legs in weight-bearing bones.
What is a bone fracture?
A break or crack in the bone.
What distinguishes a closed (simple) fracture from an open (compound) fracture?
In a closed fracture, the bone breaks cleanly without piercing the skin; in an open fracture, the broken ends penetrate the skin.
What is reduction in the context of fracture treatment?
The realignment of the broken bone ends.
How is a closed reduction performed?
By manually coaxing the bone ends back into position.
What is an open reduction?
A surgical procedure to realign and secure the bone ends using pins or wires.
What follows reduction in fracture treatment?
Immobilization using a cast or traction to allow the healing process to begin.
Approximately how long does it take for a simple fracture to heal?
6 to 8 weeks, although larger bones and older individuals may require more time.
What is a hematoma in the context of a bone fracture?
A blood-filled swelling or bruise that forms at the site of a fracture due to ruptured blood vessels.
What is the fibrocartilage callus?
The mass of repair tissue formed at a fracture site as new capillaries and connective tissue cells invade the clot.
What is the function of the fibrocartilage callus in fracture healing?
To ‘splint’ the broken bone ends together, closing the gap.
What happens after the formation of the fibrocartilage callus?
It is gradually replaced by a bony callus made of spongy bone.
What is the final phase in the healing of a bone fracture?
Bone remodeling, which refines the bony callus into a strong, permanent patch.
How does bone remodeling respond to mechanical stress during healing?
It adjusts the shape and thickness of the bone in response to muscle pull and gravity.
Which cells are responsible for bone destruction during remodeling?
Osteoclasts.
Which cells are responsible for bone formation during remodeling?
Osteoblasts.
What is the significance of the network of canaliculi in compact bone?
They allow communication and nutrient exchange between osteocytes, ensuring that bone cells are nourished despite the hardness of the matrix.
How do the central canals contribute to bone health?
They run lengthwise through compact bone, carrying blood vessels and nerves that nourish the bone.
Why do bones heal quickly despite their hard matrix?
Because of the extensive network of canaliculi, central canals, and Volkmann’s canals that ensure efficient nutrient supply and waste removal.
What gives bone its resistance to compression?
Calcium salts deposited in the bone matrix.
What provides bone with flexibility and tensile strength?
The organic matrix, especially collagen fibers.
What is the role of hormones in bone remodeling?
They regulate the deposition and removal of bone matrix, thereby managing blood calcium levels and adapting bone to mechanical stress.
How does the process of bone remodeling help maintain overall skeletal strength?
By continuously reshaping and reinforcing bone in response to stress and changes in body size.
What is the primary structural unit of compact bone?
The osteon (Haversian system).
What structural change occurs in the bones of children as they mature?
Red marrow in long bones is gradually replaced by yellow marrow.
What is the clinical significance of the epiphyseal plate in growing individuals?
It is the site where new cartilage is produced for lengthwise bone growth and is later replaced by bone.
What role do osteoclasts and osteoblasts play during bone growth?
- Osteoblasts add new bone to the outside (periosteum)
- Osteoclasts remove bone from the inside (endosteum) to widen the bone.
How does the body regulate calcium levels between the blood and bone?
Through the actions of PTH (which mobilizes calcium from bone) and osteoblasts (which deposit calcium into bone).
Why is the skeletal system considered a dynamic organ system?
Because bones continuously undergo processes of formation, growth, remodeling, and repair in response to physiological needs and external stresses.
What is a comminuted fracture?
Bone breaks into three or more fragments.
Who is most likely to experience a comminuted fracture?
Older people, whose bones are more brittle.
What is a compression fracture?
Bone is crushed.
In what type of bones do compression fractures commonly occur?
Porous bones, such as osteoporotic bones in older people.
What is a depressed fracture?
Broken bone portion is pressed inward.
Where are depressed fractures most commonly found?
Skull fractures.
What is an impacted fracture?
Broken bone ends are forced into each other.
When do impacted fractures commonly occur?
When someone tries to break a fall with outstretched arms.
What is a spiral fracture?
Ragged break occurs when excessive twisting forces are applied to a bone.
In what scenario is a spiral fracture most common?
Sports injuries.
What is a greenstick fracture?
Bone breaks incompletely, similar to how a green twig breaks.
Who is most likely to have a greenstick fracture?
Children, whose bones are more flexible than adults.
