Exam 2; A&P review--structure and function of the musculoskeletal system

Briefly describe the process of remodeling.

Bone is continually resorbed and new bone laid down to replace it in a process called remodeling. In phase 1 (activation), a stimulus (e.g., hormone, drug, vitamin, physical stressor) activates the formation of osteoclasts. In phase 2 (resorption), the osteoclasts cause resorption of bone, leaving a resorption cavity. In phase 3 (formation), new bone is laid down by the osteoblasts lining the walls of the resorption cavity.

other bones

Flat bones - Ribs - Scapulae Short bones (cuboidal bones) - Wrist - Ankles Irregular bones - Vertebrae - Mandibles - Facial bones

Osteocytes

Help maintain bone by signaling osteoblasts and osteoclasts

Articular cartilage has (numerous, no) nerves and therefore (will, does not) generate pain when injured.

No; does not

Satellite cells

Repair or regenerate skeletal muscle

long bones

- Diaphysis - Metaphysis - Epiphysis (Epiphyseal plate) - Medullary cavity - Endosteum

skeletal system

- Forms the body - Supports tissues - Permits movement by providing points of attachment for muscles - Site of blood cell formation - Mineral storage

How do the following joints differ from each other: synarthrosis, amphiarthrosis, and diarthrosis?

1.Joints are classified in part, by the degree of movement they permit. A synarthrosis is an immovable joint in which the bones are united by a continuous intervening substance such as cartilage, bone, or fibrous tissue. The sutures in the skull are an example. An amphiarthrosis, a slightly movable joint, is a form of cartilaginous joint in which the bones are connected by fibrocartilage. The symphysis pubis is an amphiarthrosis. A diarthrosis is a freely movable synovial joint such as the knee or shoulder.

1.A nursing student says, "I know about osteoclasts and osteoblasts, but what are osteocytes?" 2.Jason, a 22-year-old soccer player, asks, "If my knee cartilage has no blood supply, how does it get its nourishment?" 3.Jackson, age 37, asks, "What is the difference between striated muscle and skeletal muscle?" 4.A beginning physical therapy student says, "I was so busy memorizing the names of the little tubules that I lost the big picture. Why do muscle fibers need a sarcotubular system?" 5.Mr. Taylor says, "At the gym I hear people talk about building lean body mass. What exactly does that mean?" 6."A lot of athletes I know are taking creatine supplements for their muscles," says Mr. Young. "What do muscles do with creatine?"

1.Osteocytes are osteoblasts that are terminally differentiated; in other words, they are fully mature and no longer build bone. They communicate with both osteoblasts and osteoclasts about when and where to form and resorb bone and have other functions that keep bone functional. 2.The normal fluid in your knee joint, called synovial fluid, supplies nourishment to the cartilage. Synovial fluid is filtered from the blood, so it contains the nourishment your cartilage needs. 3.No difference; those terms refer to the same muscles. The term "striated" refers to the striped pattern that people see when they look at skeletal muscle with a microscope. 4.You ask an important question! Muscles need intracellular calcium to contract, and then they need less calcium so that they can relax. The sarcotubular system releases calcium for muscle contraction and then takes it up and stores the calcium during muscle relaxation. 5.The term "lean body mass" is another way of saying "muscle mass." So they are talking about bulking up their muscles. 6.Muscles take in creatine from the blood. They change some of it into phosphocreatine, which provides energy for muscle contraction. Our bodies normally make creatine, so you already have it in your blood.

1.Name three differences between slow-twitch and fast-twitch muscle fibers. 2.Why is adenosine triphosphate (ATP) used for muscle contraction? 3.Define the differences between tendons and ligaments. 4.Describe significant changes in the musculoskeletal system with aging.

1.Type 1 or red fibers are oxidative and have a small diameter and slow contraction speed. Type 2 or white fibers are oxidative glycolic and have a large diameter and fast contraction speed. 2.ATP is a high-energy phosphate that provides the energy for binding of actin and myosin during muscle contration and for transporting calcium from the sarcoplasmic reticulum to the myofibrils. ATP also fuels protein synthesis, which provides muscle constituents. 3.Tendons attach muscle to bone at a site called an enthesis. Ligaments attach bone to bone, helping to form joints as well as stabilizing them against excessive movement. 4.Aging is accompanied by changes in bone, joints, and muscles. Aging is associated with bone loss, which leads to osteoporosis and fractures, particularly in women. White blood cell production by the stem cells of the bone marrow decreases, predisposing the elderly to acute and chronic illnesses. With aging, cartilage of joints becomes more rigid and fragile, and changes in muscles and ligaments decrease range of motion of joints. In addition, there is a loss in skeletal muscle mass and muscle strength with aging.

1.In utero, (myotubes, myoblasts) fuse with each other to become (myotubes, myoblasts), which eventually develop into muscle fibers. 2.In muscle, the greater the innervation ratio of a particular organ, the greater its (speed of contraction, endurance); higher innervation ratios (prevent fatigue, provide precision of movement), and lower innervation ratios (prevent fatigue, provide precision of movement). 3.A muscle contracts more forcefully by (causing each motor unit to contract more forcefully, recruiting more muscle units). 4.With an isotonic contraction, the muscle maintains a constant (length, tension) as it contracts; with an isometric contraction, the muscle maintains a constant (length, tension) as (length, tension) increases.

1.myoblasts, myotubes 2.Endurance, prevent fatugue, provide precision of movement 3.Recruiting more muscle units 4.Tension, length, tension

A.Calcium ions bind to troponin, causing a structural change that opens active sites on actin filaments B.Myosin hydrolyzes ATP, and actin-myosin cross-bridges form, causing actin filaments to slide toward myosin filaments, thus shortening the sarcomere C.Ryanodine receptors open, and calcium ions flow into the cytoplasm D.An active transport process moves calcium back into the sarcoplasmic reticulum E.Action potential in motor nerve reaches the neuromuscular junction F.Muscle fiber action potential spreads along the sarcolemma G.Cross-bridging stops, sarcomeres lengthen H.Troponin moves back to its previous position, which closes the actin active sites

A.Action potential in motor nerve reaches the neuromuscular junction B.Muscle fiber action potential spreads along the sarcolemma C.Ryanodine receptors open, and calcium ions flow into the cytoplasm D.Calcium ions bind to troponin, causing a structural change that opens active sites on actin filaments E.Myosin hydrolyzes ATP, and actin-myosin cross-bridges form, causing actin filaments to slide toward myosin filaments, thus shortening the sarcomere F.An active transport process moves calcium back into the sarcoplasmic reticulum G.Troponin moves back to its previous position, which closes the actin active sites H.Cross-bridging stops, sarcomeres lengthen

Name the different types of bone cells.

Bones contains three types of cells: osteoblasts, osteoclasts, and osteocytes.

Mesenchymal stem cells

Can differentiate into multiple cell types, including bone, cartilage, and fat cells

What type of bone are the metatarsals? A.Long B.Flat C.Short D.Irregular

Correct Answer: 1 Metatarsals are long bones, they are longer than they are wide. The ankle bones in the foot are considered short (cuboidal) bones. Flat bones, such as the scapulae, have two plates of compact bone parallel to each other. Irregular bones have various shapes, and include vertebrae, mandibles, and other facial bones.

Bone formation requires collagen synthesis, fiber formation, and mineralization. The majority of the mineral content in the body is an analog of which naturally occurring mineral? A.Periosteum B.Procallus C.Calcium phosphate D.Hydroxyapatite

Correct Answer: D Hydroxyapatite is incorporated into collagen fibers for bone mineralization. Periosteum is a double-layered connective tissue that covers bones. Procallus is granulation tissue produced by fibroblasts, capillary buds, and osteoblasts in wounds. Calcium phosphate is distributed throughout the bone matrix but is not the largest mineral found in bone.

1.Isaac is a 32-year-old healthy adult. Describe how he maintains bone integrity. 2.Using the connective structure classification system for joints, compare the movement ability of joints in the human body. 3.David is a marathon runner. He is very interested in muscle physiology and he asks you to explain muscle contraction. What would you tell him?

Isaac is a 32-year-old healthy adult. Describe how he maintains bone integrity. Answer: The internal structure of bone is maintained by remodeling, a three-phase process in which existing bone is resorbed and new bone is laid down to replace it. Remodeling is carried out by clusters of bone cells termed basic multicellular units. The basic multicellular units are made up of bone precursor cells that differentiate into osteoclasts and osteoblasts. Precursor cells are located on the free surfaces of bones and along the vascular channels, especially the marrow cavities. In phase 1, activation of the remodeling cycle, a stimulus activates the bone cell precursors in a localized area of bone to form osteoclasts. In phase 2, resorption, the osteoclasts form a cone, which gradually resorbs bone, leaving behind an elongated cavity, a resorption cavity. The resorption cavity in compact bone follows the longitudinal axis of the haversian system, whereas the resorption cavity in spongy bone parallels the surface of the trabeculae. During phase 3, formation, new bone, termed secondary bone, is laid down by osteoblasts lining the walls of the resorption cavity. Successive layers in compact bone are laid down until the resorption cavity is reduced to a narrow haversian canal around a blood vessel. New trabeculae are formed in spongy bone. The entire process of remodeling takes about 3 to 6 months.

Osteoblasts

Lay down new bone

Osteoblasts differentiate into osteocytes

Osteoblasts differentiate into osteocytes

Osteoclasts receive information regarding where to begin resorption

Osteoblasts lay down layers of bone

What are the major cells involved in bone resorption?

Osteoclasts function primarily to resorb or remove bone during processes of growth and repair.

Osteoblasts lay down layers of bone

Osteoclasts receive information regarding where to begin resorption

Stimulus causes osteocyte apoptosis

Osteoclasts secrete hydrochloric acid and cathepsin K to create resorption cavity

bone remodeling and repair

Repairs microscopic injuries and maintains bone integrity Bone repair phases: - Inflammation/hematoma formation - Procallus formation - Callus formation - Callus replacement - Remodeling Three phases of remodeling - Activation of the remodeling cycle - Resorption - Formation of new bone

muscle mechanics

Repetitive discharge uAllows the muscle to activate the number of motor units needed to generate the desired force Physiologic tetanus uIncreased strength, speed and duration of stimulation causes contractions to reach a critical frequency

Osteoclasts

Resorb bone

elements of bone tissue

Rigid connective tissue Constituents: - Cells - Fibers - Ground substance - Calcium

Chondrocytes

Secrete collagen and other components of cartilage

Synoviocytes

Secrete hyaluronate into joint fluid

cancellous

Spongy bone is also called (compact, cancellous) bone.

Osteoclasts secrete hydrochloric acid and cathepsin K to create resorption cavity

Stimulus causes osteocyte apoptosis

Name at least two characteristics of each of the joints in the previous question that either facilitate or hinder movement.

The following characteristics are among those that affect mobility of joints: (1) The type of tissue connecting the bones of the joint, such as cartilage, ligament, dense fibrous tissue, membrane, or bone For instance, ligaments are sligtly stretchable and allow more movement than bone connecting the adult skull sutures, which does not allow any motion. (2) The type of bony structure of the joint. For instance, the spheroid structure of the shoulder allows circular motion; the hinge joints of the knee and elbow allow only flexion and extension.

Name three functions of articular cartilage.

The functions of articular cartilage are to cover the end of the bone in the joint, reduce friction in the joint, and to distribute the forces of weight bearing.

cancaliculi; lacunae

The small channels that connect the osteocytes in bone are called (lacunae, calaniculi); the spaces in which the osteocytes reside in bone are called the (lacunae, canaliculi).

What are the stages of bone wound healing?

The stages of bone wound healing are as follows: hematoma formation, procallus formation, callus formation, replacement by basic multicellular units of the callus with lamellar or trabecular bone, and remodeling of the periosteal and endosteal surface of the bone to the size and shape of the bone before the injury.