Chapter 6 Flashcards
Bone
An organ made up of several different tissues working together: bone (osseous) tissue, cartilage, dense connective tissue, epithelium, adipose tissue, and nervous tissue.
Skeletal system
The entire framework of bones and their cartilages.
What are the six basic functions of the skeletal system?
- Support
- Protection
- Assistance in movement
- Mineral homeostasis
- Blood cell production
- Triglyceride storage
Support
The skeleton serves as the structural framework for the body by supporting soft tissues and providing attachment points for the tendons of most skeletal muscles.
Protection
The skeleton protects the most important internal organs from injury. Eg. Cranial bones protect the brain, and the rib cage protects the heart and lungs.
Assistance in movement
Most skeletal muscles attach to bones; when they contract, they pull on bones to produce movement.
Mineral homeostasis (storage and release)
Bone tissue makes up about 18% of the weight of the human body. It stores several minerals, especially calcium and phosphorus, which contribute to the strength of bone. Bone tissue stores about 99% of the body’s calcium. On demand, bone releases minerals into the blood to maintain critical mineral balances (homeostasis) and to distribute the minerals to other parts of the body.
Blood cell production
Within certain bones, a connective tissue called red bone marrow produces red blood cells, white blood cells, and platelets, a process called hematopoiesis.
Triglyceride storage
Yellow bone marrow consists mainly of adipose cells, which store triglycerides. The stored triglycerides are a potential chemical energy reserve.
Long bone
A bone that has greater length than width.
What seven parts does a typical long bone consist of?
- Diaphysis
- Epiphyses
- Metaphysis
- Articular cartilage
- Periosteum
- Medullary cavity
- Endosteum
Diaphysis
Is the bone’s shaft or body – the long, cylindrical, main portion of the bone.
Epiphyses
Are the proximal and distal ends of the bone.
Metaphyses
The regions between the diaphysis and the epiphyses. In a growing bone, each metaphysis contains an epiphyseal (growth) plate. When a bone ceases to grow in length, each metaphysis contains a epiphyseal line.
Epiphyseal (growth) plate
A layer of hyaline cartilage that allows the diaphysis of the bone to grow in length; each metaphysis contains them.
Epiphyseal line
The resulting bone structure when the bone ceases to grow in length at about ages 14-24; replaces the cartilage in the epiphyseal plate.
Articular cartilage
Is a thin layer of hyaline cartilage covering the part of the epiphysis where the bone forms an articulation (joint) with another bone. Articular cartilage reduces friction and absorbs shock at freely movable joints. Because articular cartilage lacks a perichondrium and lacks blood vessels, repair of damage is limited.
Periosteum
Is a tough connective tissue sheath and its associated blood supply that surrounds the bone surface wherever it is not covered by articular cartilage; the periosteum also protects the bone, assists in fracture repair, helps nourish bone tissue, and serves as an attachment point for ligaments and tendons.
The periosteum is composed of an ______ of dense irregular connective tissue and an ______ that consists of cells. Some of the cells enable bone to grow in ______, but not in ______.
Outer fibrous layer; inner osteogenic layer; thickness; length
Perforating fibers (Sharpey’s fibers)
Thick bundles of collagen that extend from the periosteum into the bone extracellular matrix, and attach the periosteum to underlying bone.
Medullary cavity
AKA marrow cavity; is a hollow, cylindrical space within the diaphysis that contains fatty yellow bone marrow and numerous blood vessels in adults; this cavity minimizes the weight of the bone by reducing the dense bony material where it is least needed. The long bones’ tubular design provides maximum strength with minimum weight.
Endosteum
Is a thin membrane that lines the medullary cavity.
Why is bone tissue classified as a connective tissue?
Like other connective tissue, bone, or osseous tissue, contains an abundant extracellular matrix that surrounds widely separated cells. The extracellular matrix is ~15% water, ~30% collagen fibers, and ~55% crystallized mineral salts.
Hydroxyapatite
Crystals formed when calcium phosphate combines with calcium hydroxide.
Calcification
When mineral salts are deposited in the framework formed by the collagen fibers of the extracellular matrix, they crystallize, and the tissue hardens.
What are the four types of cells present in bone tissue?
- Osteoprogenitor cells
- Osteoblasts
- Osteocytes
- Osteoclasts
Osteoprogenitor cells
Osteoprogenitor cells are found along the inner portion of the periosteum, in the endosteum, and in the canals within bone that contain blood vessels; develop into an osteoblast; only cells that undergo cell division.
Osteoblasts
Form bone extracellular matrix.
Osteocytes
Maintain bone tissue.
Osteoclasts
Main function is bone resorption (the breakdown of bone extracellular matrix).
Compact bone tissue
Contains few spaces and is the strongest form of bone tissue; is found beneath the periosteum of all bones and makes up the bulk of the diaphysis of long bones; provides protection and support and resists the stresses produced by weight and movement.
Osteons
AKA haversian systems: repeating structural units that compact bone tissue is composed of. Osteons in compact bone tissue are aligned in the same direction and are parallel to the length of the diaphysis (as a result, the shaft of a long bone resists bending or fracturing even when considerable force is applied from either end).
Osteonic canal
AKA haversian or central canal; surrounded by concentric lamellae; holds nerves and blood vessels.
Concentric lamellae
Resemble growth rings on a tree; circular plates of mineralized extracellular matrix of increasing diameter, surrounding the osteonic canal. These tubelike units of bone generally form a series of parallel cylinders that, in long bones, tend to run parallel to the long axis of the bone.
Lacunae
Small spaces between the concentric lamellae; contain osteocytes
Canaliculi
Small canals that extend from the lacunae, that connect to other lacunae in the osteonic canal. Allow for intracellular communication and a passageway for the delivery of nutrients to the osteocytes.
Interstitial lamellae
Areas between neighboring osteons; have lacunae with osteocytes and canaliculi; are small fragments of older osteons that have been partially destroyed during bone rebuilding or growth.
Interosteonic canals
AKA Volkmann’s or perforating canals; blood vessels and nerves from the periosteum that penetrate the compact bone tissues; the vessels and nerves of the interosteonic canals connect with those of medullary cavity, periosteum, and osteonic canals.