week 5 quiz

functions of canaliculi

Radiating in all directions from the lacunae are tiny canaliculi, which are filled with extracellular fluid. Inside the canaliculi are slender fingerlike processes of osteocytes. Neighboring osteocytes communicate via gap junction. The canaliculi connect lacunae with one another and with the central canals, forming an intricate, miniature system of interconnected canals throughout the bone. This system provides many routes for nutrients and oxygen to reach the osteocytes and for the removal of wastes.

medullary cavity

-It contains a single layer of bone‐forming cells and a small amount of connective tissue.

list and describe steps of bone repair in order

1. Reactive phase. This phase is an early inflammatory phase. Blood vessels crossing the fracture line are broken. As blood leaks from the torn ends of the vessels, a mass of blood (usually clotted) forms around the site of the fracture. This mass of blood, called a fracture hematoma, usually forms 6 to 8 hours after the injury. Because the circulation of blood stops at the site where the fracture hematoma forms, nearby bone cells die. Swelling and inflammation occur in response to dead bonecells, producing additional cellular debris. Phagocytes (neutrophils and macrophages) and osteoclasts begin to remove the dead or damaged tissue in and around the fracture hematoma. This stage may last up to several weeks. 2a- Reparative phase: Fibrocartilaginous callus formation. The reparative phase is characterized by two events: the formation of a fibrocartilaginous callus, and a bony callus to bridge the gap between the broken ends of the bones. Blood vessels grow into the fracture hematoma and phagocytes begin to clean up dead bone cells. Fibroblasts from the periosteum invade the fracture site and produce collagen fibers. In addition, cells from the periosteum develop into chondroblasts and begin to produce fibrocartilage in this region. These events lead to the development of a fibrocartilaginous (soft) callus, a mass of repair tissue consisting of collagen fibers and cartilage that bridges the broken ends of the bone. Formation of the fibrocartilaginous callus takes about 3 weeks. 2b-Reparative phase: Bony callus formation. In areas closer to well‐vascularized healthy bone tissue, osteoprogenitor cells develop into osteoblasts, which begin to produce spongy bone trabeculae. The trabeculae join living and dead portions of the original bonefragments. In time, the fibrocartilage is converted to spongy bone, and the callus is then referred to as a bony (hard) callus. The bony callus lasts about 3 to 4 months. 3-Bone remodeling phase. The final phase of fracture repair is bone remodeling of the callus. Dead portions of the original fragments of broken bone are gradually resorbed by osteoclasts. Compact bone replaces spongy bone around the periphery of the fracture. Sometimes, the repair process is so thorough that the fracture line is undetectable, even in a radiograph (x‐ray). However, a thickened area on the surface of the bone remains as evidence of a healed fracture.

Identify all functions of the skeletal system and describe them.

1.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. 2.Protection: The skeleton protects the most important internal organs from injury. For example, cranial bones protect the brain, and the rib cage protects the heart and lungs. 3.Assistance in movement: Most skeletal muscles attach to bones; when they contract, they pull on bones to produce movement. This function is discussed in detail in Chapter 10. 4.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. 5.Blood cell production: Within certain bones, a connective tissue called red bone marrowproduces red blood cells, white blood cells, and platelets, a process called hemopoiesis. Red bone marrow consists of developing blood cells, adipocytes, fibroblasts, and macrophages within a network of reticular fibers. It is present in developing bones of the fetus and in some adult bones, such as the hip (pelvic) bones, ribs, sternum (breastbone), vertebrae (backbones), skull, and ends of the bones of the humerus (arm bone) and femur (thigh bone). In a newborn, all bone marrow is red and is involved in hemopoiesis. With increasing age, much of the bone marrow changes from red to yellow. Blood cell production is considered in detail in Section 19.2. 6.Triglyceride storage: Yellow bone marrow consists mainly of adipose cells, which store triglycerides. The stored triglycerides are a potential chemical energy reserve. (Functions of Bone Tissue 1.Supports soft tissue and provides attachment for skeletal muscles. 2.Protects internal organs. 3.Assists in movement, along with skeletal muscles. 4.Stores and releases minerals. 5.Contains red bone marrow, which produces blood cells. 6.Contains yellow bone marrow, which stores triglycerides (fats).

osteoclasts

A large, multinuclear cell that resorbs (destroys) bone matrix. (break down boneclasts means break(weird macrophage)found in the endosteumlining the periosteum) are huge cells derived from the fusion of as many as 50 monocytes (a type of white blood cell) and are concentrated in the endosteum. On the side of the cell that faces the bone surface, the osteoclast's plasma membrane is deeply folded into a ruffled border. Here the cell releases powerful lysosomal enzymes and acids that digest the protein and mineral components of the underlying extracellular bone matrix. This breakdown of bone extracellular matrix, termed bone resorption (rē‐SORP‐shun), is part of the normal development, maintenance, and repair of bone. (Note: The ending ‐clast means that the cell breaks down extracellular matrix.) As you will see later, in response to certain hormones, osteoclasts help regulate blood calcium level. They are also target cells for drug therapy used to treat osteoporosis.

symphysis

A type of joint that has grown together forming a very stable connection. - a place where 2 bones are closely joined

identify where osteons of bone tissue are found.

Compact bone tissue is made of cylindrical osteons that are aligned such that they travel the length of the bone.

describe what type of cartilage is found in the epiphyseal plate and where is it found?

Formation of articular cartilage and the epiphyseal (growth) plate. The hyaline cartilage that covers the epiphyses becomes the articular cartilage. Prior to adulthood, hyaline cartilage remains between the diaphysis and epiphysis as the epiphyseal (growth) plate, the region responsible for the lengthwise growth of long bones that you will learn about next.

list/describe all the minerals that are needed for bone matrix development

Large amounts of calcium and phosphorus are needed while bones are growing, as are smaller amounts of magnesium, fluoride, and manganese. These minerals are also necessary during bone remodeling.

red bone marrow

Within certain bones, a connective tissue called red bone marrowproduces red blood cells, white blood cells, and platelets, a process called hemopoiesis. Red bone marrow consists of developing blood cells, adipocytes, fibroblasts, and macrophages within a network of reticular fibers.

osteoblast

are bone‐building cells. They synthesize and secrete collagen fibers and other organic components needed to build the extracellular matrix of bone tissue, and they initiate calcification (described shortly). As osteoblasts surround themselves with extracellular matrix, they become trapped in their secretions and become osteocytes. (Cell formed from an osteogenic cell that participates in bone formation by secreting some organic components and inorganic salts.) (Bone building cells grow boneBlasts means grow found in the endosteum lining the periosteum eventually continues on as osteocyte once it surrounds itself in matrix trap)

Epiphysis

are the proximal and distal ends of the bone.

epiphysis

are the proximal and distal ends of the bones.

Metaphysis (long bone)

are the regions between the diaphysis and the epiphyses. In a growing bone, each metaphysis contains an epiphyseal (growth) plate, a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length (described later in the chapter). When a bone ceases to grow in length at about ages 14-24, the cartilage in the epiphyseal plate is replaced by bone; the resulting bony structure is known as the epiphyseal line.

yellow bone marrow

consists mainly of adipose cells, which store triglycerides. The stored triglycerides are a potential chemical energy reserve.

compact bone

contains few spaces and is the strongest form of bone tissue. It is found beneath the periosteum of all bones and makes up the bulk of the diaphyses of long bones. Compact bone tissue provides protection and support and resists the stresses produced by weight and movement.

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.

Endosteum

is a thin membrane that lines the medullary cavity. It contains a single layer of bone‐forming cells and a small amount of connective tissue.

Have an understanding of the bones that form by endochondral ossification and the bones that form by intramembraneous ossification

endochondral ossification: The replacement of cartilage by bone is called endochondralossification. Although most bones of the body are formed in this way, the process is best observed in a long bone. is the process by which growing cartilage is systematically replaced by bone to form the growing skeleton intramembraneous ossification: Intramembranous ossification is the simpler of the two methods of bone formation. The flat bones of the skull, most of the facial bones, mandible (lower jawbone), and the medial part of the clavicle (collar bone) are formed in this way. Also, the "soft spots" that help the fetal skull pass through the birth canal later harden as they undergo intramembranous ossification

epiphyseal plate

epiphyseal (growth) plate, a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length (described later in the chapter). When a bone ceases to grow in length at about ages 14-24, the cartilage in the epiphyseal plate is replaced by bone; the resulting bony structure is known as the epiphyseal line.

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. It is composed of an outer fibrous layer of dense irregular connective tissue and an inner osteogenic layer that consists of cells. Some of the cells enable bone to grow in thickness, but not in length. 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 attached to the underlying bone by perforating fibers or Sharpey's fibers, thick bundles of collagen that extend from the periosteum into the bone extracellular matrix.

Diaphysis

is the bone's shaft or body—the long, cylindrical, main portion of the bone.

Diaphysis (shaft)

is the bone's shaft or body—the long, cylindrical, main portion of the bone.

describe the effect of the parathyroid hormone directly on the bones.

parathyroidhormone, calcitriol (the active form of vitamin D), and calcitonin are other hormones that can affect bone remodeling. -Secreted by the parathyroid glands; promotes bone resorption by osteoclasts; enhances recovery of calcium ions from urine; promotes formation of the active form of vitamin D (calcitriol).

spongy bone

spongy bone tissue, also referred to as trabecular or cancellous bone tissue, does not contain osteons. Spongy bone tissue is always located in the interior of a bone, protected by a covering of compact bone. It consists of lamellae that are arranged in an irregular pattern of thin columns called trabeculae. -Spongy bone tissue makes up most of the interior bone tissue of short, flat, sesamoid, and irregularly shaped bones. - Spongy bone tissue is different from compact bone tissue in two respects. First, spongy bonetissue is light, which reduces the overall weight of a bone. This reduction in weight allows the bone to move more readily when pulled by a skeletal muscle. Second, the trabeculae of spongybone tissue support and protect the red bone marrow. Spongy bone in the hip bones, ribs, sternum (breastbone), vertebrae, and the proximal ends of the humerus and femur is the only site where red bone marrow is store