within 60 minutes of time frame.Once logged in to the school site to write the quiz the clocks ticks.It covers 5 chapters. I provide here the literature for your reference.
HUMAN ANATOMY & PHYSIOLOGY Copyright W iley, 2020 171 Bone tissue is a complex and dynamic living tissue. It continually engages in a process called bone remodeling—the building of new bone tissue and breaking down of old bone tissue. In the early days of space exploration, young, healthy men in prime physical shape returned from their space flights only to alarm their physicians. Physical examinations of the astronauts revealed that they had lost up to 20% of their total bone density during their extended stay in space. The zero-gravity (weightless) environment of space, coupled with the fact that the astronauts traveled in small capsules that greatly limited their movement for extended periods of time, placed minimal strain on their bones. In contrast, athletes subject their bones to great forces, which place significant strain on the bone tissue. Accomplished athletes show an increase in overall bone density. How is bone capable of changing in response to the diff erent mechanical demands placed on it? Why do high activity levels that strain bone tissue greatly improve bone health? This chapter surveys the various components of bones to help you understand how bones form, how they age, and how exercise aff ects their density and strength. Q Did you ever wonder why more females than males are affected by osteoporosis? The Skeletal System: Bone Tissue Bone Tissue and Homeostasis CHAPTER 6 Bone tissue is continuously growing, remodeling, and repairing itself. It contributes to homeostasis of the body by providing support and protection, producing blood cells, and storing minerals and triglycerides. c06TheSkeletalSystemBoneTissue.indd Page 171 9/5/16 8:23 PM user /208/WB01989/9781119287759/ch06/text_s 168 Copyright W iley, 2020 172 CHAPTER 6 The Skeletal System: Bone Tissue 3. Which bones contain red bone marrow? 4. How do red bone marrow and yellow bone marrow diff er in composition and function? 6.2 Structure of Bone OBJECTIVE • Describe the structure and functions of each part of a long bone. We will now examine the structure of bone at the macroscopic level. Macroscopic bone structure may be analyzed by considering the parts of a long bone, such as the humerus (the arm bone) shown in Figure 6.1a. A long bone is one that has greater length than width. A typical long bone consists of the following parts: 1. The diaphysis (dī-AF-i-sis = growing between) is the bone’s shaft or body—the long, cylindrical, main portion of the bone. 2. The epiphyses (e-PIF-i-sēz = growing over; singular is epiphysis) are the proximal and distal ends of the bone. 3. The metaphyses (me-TAF-i-sēz; meta- = between; singular is metaphysis) are the regions between the diaphysis and the epi- physes. In a growing bone, each metaphysis contains an epiphy- seal (growth) plate (ep′-i-FIZ-ē-al), 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. 4. The 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. 5. The periosteum (per-ē-OS-tē-um; peri- = around) is a tough con- nective 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 tis- sue and an inner osteogenic layer that consists of cells. Some of the cells enable bone to grow in thickness, but not in length. The perios- teum 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 per- forating fibers or Sharpey’s fibers, thick bundles of collagen that extend from the periosteum into the bone extracellular matrix. 6. The medullary cavity (MED-ul-er-ē; medulla- = marrow, pith), or 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’ tubu- lar design provides maximum strength with minimum weight. 6.1 Functions of Bone and the Skeletal System OBJECTIVE • Describe the six main functions of the skeletal system. A bone is an organ made up of several diff erent tissues working together: bone (osseous) tissue, cartilage, dense connective tissue, epithelium, adipose tissue, and nervous tissue. The entire framework of bones and their cartilages constitute the skeletal system. The study of bone structure and the treatment of bone disorders is referred to as osteology (os-tē-OL-o-jē; osteo- = bone; -logy = study of). The skeletal system performs several basic functions: 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 marrow produces red blood cells, white blood cells, and platelets, a process called hemopoiesis (hēm-ō-poy-ē-sis; hemo- = blood; -poiesis = making). 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 adi- pose cells, which store triglycerides. The stored triglycerides are a potential chemical energy reserve. Checkpoint 1. How does the skeletal system function in support, protection, movement, and storage of minerals? 2. Describe the role of bones in blood cell production. c06TheSkeletalSystemBoneTissue.indd Page 172 9/5/16 8:23 PM user /208/WB01989/9781119287759/ch06/text_s 169 johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Underline johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Highlight johnup Underline johnup Underline johnup Highlight Copyright W iley, 2020 6.2 Structure of Bone 173 FIGURE 6.1 Parts of a long bone. The spongy bone tissue of the epiphyses and metaphyses contains red bone marrow, and the medullary cavity of the diaphysis contains yellow bone marrow (in adults). (b) Partially sectioned humerus (a) Partially sectioned humerus (arm bone) Epiphyseal line Proximal epiphysis Medullary cavity in diaphysis Proximal epiphysis Metaphysis Diaphysis Metaphysis Distal epiphysis Articular cartilage Epiphyseal line Spongy bone (contains red bone marrow) Red bone marrow Endosteum (lines medullary cavity) Compact bone Periosteum Medullary cavity (contains yellow bone marrow in adults) Articular cartilage Nutrient artery Humerus Spongy bone Compact bone Metaphysis A long bone is covered by articular cartilage at the articular surfaces of its proximal and distal epiphyses and by periosteum around all other parts of the bone. Q What is the functional significance of the periosteum? 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). c06TheSkeletalSystemBoneTissue.indd Page 173 9/5/16 8:23 PM user /208/WB01989/9781119287759/ch06/text_s 170 Copyright W iley, 2020 174 CHAPTER 6 The Skeletal System: Bone Tissue 7. The endosteum (end-OS-tē-um; endo- = within) is a thin mem- brane that lines the medullary cavity. It contains a single layer of bone-forming cells and a small amount of connective tissue. Checkpoint 5. Diagram the parts of a long bone, and list the functions of each part. 6.3 Histology of Bone Tissue OBJECTIVES • Explain why bone tissue is classified as a connective tissue. • Describe the cellular composition of bone tissue and the functions of each type of cell. • Compare the structural and functional diff erences between compact and spongy bone tissue. We will now examine the structure of bone at the microscopic level. Like other connective tissues, bone, or osseous tissue (OS-ē-us), con- tains an abundant extracellular matrix that surrounds widely sepa- rated cells. The extracellular matrix is about 15% water, 30% collagen fibers, and 55% crystallized mineral salts. The most abundant mineral - salt is calcium phosphate [Ca3(PO4)2]. It combines with another min- eral salt, calcium hydroxide [Ca(OH)2], to form crystals of hydroxyapa- tite [Ca10(PO4)6(OH)2] (hī-drok-sē-AP-a-tīt). As the crystals form, they combine with still other mineral salts, such as calcium carbonate (CaCO3), and ions such as magnesium, fluoride, potassium, and sul- fate. As these mineral salts are deposited in the framework formed by the collagen fibers of the extracellular matrix, they crystallize and the