A&p chapt 7: bones

What are bones composed of?

bone tissue, cartilage, dense connective tissue, blood, and nervous tissue.

What are the main functions of bones?

Bones support and protect softer tissues, provide points of attachment for muscles, house blood-producing cells, and store inorganic salts.

What are the characteristics of long bones?

Long and narrow with expanded ends.

What defines short bones?

Cubelike, with length equal to width, and include sesamoid bones embedded in tendons.

Describe flat bones.

Platelike with broad surfaces.

What are irregular bones?

They have a variety of shapes and are often connected to other bones.

What is the epiphysis of a long bone?

The expanded end of a long bone.

What is the diaphysis of a long bone?

The shaft of the bone.

What is the metaphysis?

The widening part between the diaphysis and epiphysis.

What is the function of articular cartilage?

It covers the epiphysis of long bones.

What is the periosteum?

A dense connective tissue that encloses the bone.

What is compact bone?

It forms the wall of the diaphysis and consists of cylindrical units called osteons.

What is spongy bone?

It makes up the epiphyses and consists of branching plates called trabeculae.

What are osteocytes?

Mature bone cells that occupy chambers called lacunae.

How do osteocytes exchange nutrients?

They exchange nutrients and wastes via cell processes within tiny passageways called canaliculi.

What is the extracellular matrix of bone primarily composed of?

It is largely composed of collagen fibers and inorganic salts.

What is intramembranous ossification?

The process of forming flat bones from primitive connective tissue.

What are examples of intramembranous bones?

Examples include: flat bones of the skull, clavicles, sternum, and some facial bones.

What is endochondral ossification?

The process of replacing hyaline cartilage to form most bones of the skeleton.

What are examples of endochondral bones?

Examples include: the femur, humerus, radius, tibia, phalanges, and vertebrae.

What happens to chondrocytes during endochondral ossification?

They enlarge, lacunae grow, the matrix breaks down, and chondrocytes die.

What is the role of osteoblasts in bone development?

Osteoblasts invade the area, deposit bone matrix, and eventually become osteocytes.

What are osteoclasts?

Cells that break down calcified bone matrix.

What is the epiphyseal plate?

The region in a growing long bone where bone grows in length, separating the diaphysis from the epiphysis.

What are the four layers of the epiphyseal plate?

1. Zone of resting cartilage

2. Zone of proliferating cartilage

3. Zone of hypertrophic cartilage

4. Zone of calcified cartilage.

What occurs in the zone of resting cartilage?

It contains resting cells that anchor the epiphyseal plate to the epiphysis.

What happens in the zone of proliferating cartilage?

Rows of young cells undergo mitosis.

What is the function of the zone of hypertrophic cartilage?

Older cells thicken the epiphyseal plate and lengthen the bone; matrix calcifies and chondrocytes die.

What characterizes the zone of calcified cartilage?

It consists of a thin layer of dead cartilage cells and calcified matrix.

What happens after osteoclasts break down the calcified matrix?

Osteoblasts invade and replace cartilage with bone tissue.

When can bone no longer grow in length?

When ossification centers meet and the epiphyseal plate ossifies.

How can bone thicken?

By depositing compact bone on the outside under the periosteum.

What is bone remodeling?

The ongoing process of bone resorption and deposition throughout life.

What is bone resorption?

The removal of bone, primarily by the action of osteoclasts.

What is bone deposition?

The formation of bone, primarily by the action of osteoblasts.

What percentage of the skeleton is replaced each year?

10% - 20%.

How does Vitamin D affect bone health?

It aids in calcium absorption; deficiency can lead to rickets or osteomalacia.

What role does Vitamin A play in bone development?

It regulates osteoblast and osteoclast activity; deficiency can retard bone development.

What is the function of Vitamin C in bone health?

It is essential for collagen synthesis; deficiency results in slender, fragile bones.

How does growth hormone affect bone development?

It stimulates cartilage cell division; insufficiency can lead to pituitary dwarfism.

What effect do sex hormones have on bones?

They promote bone formation and stimulate ossification of epiphyseal plates.

What are the two types of fractures?

Simple (closed) fractures and compound (open) fractures.

What characterizes a simple fracture?

It is protected by uninjured skin or mucous membrane.

What occurs in the first step of fracture repair?

A hematoma, or large blood clot, forms.

What happens during the formation of a cartilaginous callus in fracture repair?

Phagocytes remove debris and fibrocartilage invades the area.

What is the role of osteoblasts in the bony callus stage of fracture repair?

They invade the area and fill the space with hard callus.

What are the major functions of bones?

Provide shape to the body, support body structures, protect body structures, aid body movements, contain tissue that produces blood cells, and store inorganic salts.

How do bones support and protect the body?

Bones provide shape for the head, face, thorax, and limbs; support body weight; and protect vital organs such as the brain, heart, and lungs.

What is hematopoiesis?

Hematopoiesis is the formation of blood cells, which occurs in red bone marrow.

What types of blood cells are produced in red bone marrow?

Red blood cells, white blood cells, and platelets.

What happens to red bone marrow as a person ages?

Some red bone marrow is replaced by yellow bone marrow, which stores fat but does not produce blood cells.

What is the most abundant inorganic salt in bone?

Crystals of hydroxyapatite (calcium phosphate).

What ions are stored in bone besides calcium?

Magnesium ions, sodium ions, potassium ions, and carbonate ions.

What condition results from loss of bone mineralization?

Osteoporosis.

How is blood calcium level regulated?

By parathyroid hormone and calcitonin.

What is a fragility fracture?

A fracture that occurs from less than standing height, indicating low bone density.

What factors contribute to fragility fractures in older adults?

Bone remodeling occurs throughout life, but with age, osteoclasts remove more bone tissue than osteoblasts deposit, leading to osteopenia or osteoporosis.

What is the estimated prevalence of bone loss conditions in people over 50?

About half of people over 50 have a bone loss condition.

What lifestyle changes can help prevent fragility fractures?

Engage in 30 minutes of weight-bearing exercise daily, get enough calcium and vitamin D, and avoid smoking.

How many bones are in the adult human skeleton?

About 206 bones.

What are sutural bones?

Extra bones that can occur in the sutures between major skull bones.

What are sesamoid bones?

Small bones that can occur in tendons and help reduce friction.

What are the two main divisions of the skeleton?

Axial skeleton (80 bones) and appendicular skeleton (126 bones).

What bones are included in the axial skeleton?

Skull, middle ear bones, hyoid bone, vertebral column, and thoracic cage.

What bones are included in the appendicular skeleton?

Pectoral girdle, upper limbs, pelvic girdle, and lower limbs.

How many bones compose the skull?

The skull is composed of 22 bones.

What is the composition of the skull?

The skull consists of the cranium (8 bones) and the facial skeleton (14 bones).

What is unique about the mandible compared to other skull bones?

The mandible is the only skull bone that is not interlocked along sutures.

What do the orbits of the eyes contain?

Both cranial and facial bones.

Where are paranasal sinuses located?

In both cranial and facial bones.

What are the main components of the cranium?

The cranium consists of the frontal bone, parietal bones, occipital bone, temporal bones, sphenoid bone, and ethmoid bone.

What is the function of the frontal bone?

The frontal bone forms the forehead, roof of the nasal cavity, roofs of the orbits, and contains the frontal sinuses.

What are the parietal bones responsible for?

The parietal bones form the sides and roof of the cranium and are connected by the sagittal and coronal sutures.

What structures are associated with the occipital bone?

The occipital bone forms the back of the skull and base of the cranium, containing the foramen magnum and occipital condyles.

What features are found on the temporal bones?

The temporal bones form the sides and base of the cranium, containing the external acoustic meatus, mandibular fossa, mastoid process, and styloid process.

What is the role of the sphenoid bone?

The sphenoid bone forms the base of the cranium and sides of the skull, containing the sella turcica and sphenoid sinuses.

What is the ethmoid bone's significance?

The ethmoid bone is located in front of the sphenoid and forms the roof and walls of the nasal cavity, floor of the cranium, and wall of the orbits.

What are the major sutures of the cranium?

The major sutures include the coronal, sagittal, squamous, and lambdoid sutures.

What are the maxillae and their functions?

The maxillae form the upper jaw, anterior roof of the mouth, floors of the orbits, and sides and floors of the nasal cavity.

What do the palatine bones contribute to?

The palatine bones are L-shaped and form the posterior section of the hard palate and the floor and lateral walls of the nasal cavity.

What is the function of the zygomatic bones?

The zygomatic bones form the prominences of the cheeks and contribute to the lateral walls and floors of the orbits.

What is the vomer bone's location and purpose?

The vomer bone is located along the midline of the nasal cavity and forms the inferior portion of the nasal septum.

What is the structure and function of the mandible?

The mandible is the lower jawbone, characterized by a horseshoe-shaped body and features such as the ramus, condyle, and foramen.

What are fontanels in an infant's skull?

Fontanels are fibrous membranes that connect cranial bones where intramembranous ossification is incomplete.

What is the composition of the vertebral column?

The vertebral column consists of 33 separate bones in infants and 26 in adults, including cervical, thoracic, lumbar, sacral, and coccygeal vertebrae.

What are the four curvatures of the vertebral column?

The four curvatures are cervical curvature (secondary), thoracic curvature (primary), lumbar curvature (secondary), and sacral curvature (primary).

What are the components of a typical vertebra?

A typical vertebra includes the body, pedicles, laminae, spinous process, transverse processes, vertebral foramen, and facets.

What distinguishes cervical vertebrae from other vertebrae?

Cervical vertebrae are the smallest, have transverse foramina, and bifid spinous processes (C2-C6), with C1 (Atlas) supporting the head and C2 (Axis) allowing rotation.

What are the characteristics of thoracic vertebrae?

Thoracic vertebrae are larger than cervical vertebrae, articulate with ribs, and have long, pointed spinous processes.

What defines lumbar vertebrae?

Lumbar vertebrae are characterized by large bodies, thick short spinous processes, and are weight-bearing.

What is the structure and function of the sacrum?

The sacrum is a triangular structure at the base of the vertebral column, usually consisting of 5 fused vertebrae, forming the posterior wall of the pelvic cavity.

What is the coccyx?

The coccyx, or tailbone, is usually composed of 4 fused vertebrae that fuse between the ages of 25 and 30.

What are common disorders of the vertebral column?

Common disorders include herniated discs, kyphosis, scoliosis, lordosis, and compression fractures.

What does the thoracic cage consist of?

The thoracic cage includes the ribs, thoracic vertebrae, sternum, and costal cartilages that attach the ribs to the sternum.

What is the primary function of the rib cage?

Supports the pectoral girdle and upper limbs, protects thoracic and upper abdominal viscera, and plays a role in breathing.

How many pairs of ribs do humans have?

12 pairs of ribs.

What are the two types of false ribs?

Vertebrochondral ribs (upper 3 pairs) and floating ribs (lower 2 pairs).

What is the structure of a rib?

A rib consists of a shaft (main portion), head (posterior end articulating with vertebrae), tubercle (articulates with vertebra), and costal cartilage (hyaline cartilage connecting rib to sternum).

What are the three parts of the sternum?

Manubrium, body, and xiphoid process.

What is the pectoral girdle composed of?

2 clavicles and 2 scapulae.