Ch. 11&12 Write Up

Chapter 11 & 12 Review

Chapter 11 Review
11.1 Overview of the Skeletal System:
Skeletal system is the biological system providing support in living organisms. Skin, muscle and bones allow movement. Skin - pliable covering. Muscles do actual moving. Bones give anchor to move against. The skeleton functions not only as the support for the body but also in haematopoiesis, the manufacture of blood cells that takes place in bone marrow. This is why people who have cancer of the bone marrow almost always die. It is also necessary for protection of vital organs and is needed by the muscles for movement. Skeletal system - the hard structure (bones and cartilages) that provides a frame for the body of an animal. System - a group of physiologically or anatomically related organs or parts; "the body has a system of organs for digestion."Musculoskeletal system - the system of muscles and tendons and ligaments and bones and joints and associated tissues that move the body and maintain its form. Skeletal structure - any structure created by the skeleton of an organism. Endoskeleton - the internal skeleton; bony and cartilaginous structure (especially of vertebrates). Exoskeleton - the exterior protective or supporting structure or shell of many animals (especially invertebrates) including bony or horny parts such as nails or scales or hoofs.

11.2 Bone Growth, Remodeling, & Repair:
Growth takes place at the epiphyseal growth plate of long bones by a finely balanced cycle of cartilage growth, matrix formation and calcification of cartilage that acts as a scaffold for bone formation. This sequence of cellular events constitutes endochondral ossification. Another feature of bone growth is a process of modeling, where bone is being continuously resorbed and replaced by new bone. Modeling is most active during childhood and adolescence, and enables long bones to increase in diameter, to change shape and develop a marrow cavity. Modeling continues throughout adult life with bone restoration equally balanced by bone formation in a healthy skeleton, although in the adult the process is referred to as remodeling. An individual's skeletal growth rate and adult limb bone length have an important genetic determinant, but are influenced by many factors including circulating hormones, nutritional intake, mechanical influences and disease. Growth disturbances result when there is disruption of the normal cellular activity of growth plate chondrocytes and/or the cells of bone. Bone remodeling is a dynamic, lifelong process in which old bone is removed from the skeleton and new bone is added. It consists of two distinct stages – resorption and formation – that involve the activity of special cells called osteoclasts and osteoblasts. Usually, the removal and formation of bone are in balance and maintain skeletal strength and integrity.

11.3 Bones of Axial System:
A multi-axial bone fixation implant includes an elongated member, one or more bone anchor assemblies, and stabilizer members which are fitted within the elongated member. A bone bolt having cancellous threads on one end and machine threads at the opposing end and an enlarged portion between these sections is also provided. The bone bolt is anchored into a bone via the cancellous thread end. The machine threaded end passes through an opening of the elongated member and the stabilizer, and is engaged by a coupled washer and nut. The washer includes an undercut within its oblong aperture, and the nut includes a projecting sleeve. The sleeve is inserted into the washer aperture and expanded, so that the undercut retains the sleeve within the washer without impairing the rotatability or translatability of the nut and washer with respect to each other. When locked by the nut and washer atop the elongated member, the enlarged portion of the bolt is forced against an inside wall of the stabilizer, which is in turn locked against the elongated member. Accordingly, the elongated member is fixed with respect to the bone anchor at one of an infinite number of multi-axial angles. The bones of the Axial System are: The bones of the skull, the bones of the Thorax, &The bones of the Vertebral Column.

11.4 Bones of the Appendicular Skeleton
The appendicular skeleton consists of the girdles and the skeleton of the limbs. The upper (anterior) limbs are attached to the pectoral (shoulder) girdle and the lower (posterior) limbs are attached to the pelvic (hip) girdle. The Pectoral (Shoulder) Girdle. The Pectoral girdle consists of two shoulder blades (scapulae) and two collar bones (clavicles). These bones articulate with one another, allowing some degree of movement. Shoulder Blades (Scapulae) The shoulder blade is a flat triangular bone which stretches from the shoulder to the vertebral column at the back. On the back side it has a bony ridge for the attachment of the muscles. The bony ridge forms a prominent projection, the acromion, above the shoulder joint. Beneath the collar bone and just on the inside of the shoulder joint, is another bony projection of the shoulder blade, the coracoids process, which also serves for the attachment of muscles. The upper outer corner of the shoulder blade ends in the glenoid cavity into which fits the head of the upper arm bone, forming a ball and socket joint. Collar Bones (Clavicles) each collar bone is rod-shaped and roughly S-shaped. It lies horizontally and articulates with the upper end of the breastbone, right in the middle and front, just above the first rib. The lateral end articulates with the acromium. Collar bones serve as a support for the shoulder blades in front and keep the shoulder blades back so that the arms can hang freely at the sides of the body. They prevent the pectoral girdles from getting out of joint easily and ample movement of the shoulders.

11.5 Articulations:
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally. Joints are mainly classified structurally and functionally. Structural classification is determined by how the bones connect to each other, while functional classification is determined by the degree of movement between the articulating bones. In practice, there is significant overlap between the two types of classifications. Terms ending in the suffix -sis are singular and refer to just one joint, while -ses is the suffix for pluralization.

Chapter 12
12.1 Overview of Muscular System:

The human body contains more than 650 individual muscles which are attached to the skeleton, which provides the pulling power for us to move around. The main job of the muscular system is to provide movement for the body. The muscular system consist of three different types of muscle tissues: skeletal, cardiac, smooth. Each of these different tissues has the ability to contract, which then allows body movements and functions. There are two types of muscles in the system and they are the involuntary muscles, and the voluntary muscles. The muscle in which we are allow to control by ourselves are called the voluntary muscles and the ones we can? Controls are the involuntary muscles. The heart, or the cardiac muscle, is an example of involuntary muscle. (http://library.thinkquest.org/10348/find/content/muscular.html)
12.2 Skeletal Muscle Fiber Contraction:

Skeletal muscle is a type of striated muscle, usually attached to the skeleton. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction. They generally contract voluntarily (via somatic nerve stimulation), although they can contract involuntarily through reflexes. The whole muscle is wrapped in a special type of connective tissue, epimysium. Calcium ions bind to troponin, exposing myosin binding sites.
12.3 Whole Muscle Contraction:

When we think of a muscle contracting normally, we tend to think of the muscle shortening as it generates force. While it's true that this is a way of muscle contracting, there are many different ways that a muscle can generate force. When a muscle is activated and required to lift a load which is less than the maximum tetanic tension it can generate, the muscle begins to shorten. Contractions that permit the muscle to shorten are referred to as concentric contractions. An example of a concentric contraction in the raising of a weight during a bicep curl.
In concentric contractions, the force generated by the muscle is always less than the muscle's maximum (Po). As the load the muscle is required to lift decreases, contraction velocity increases. This occurs until the muscle finally reaches its maximum contraction velocity, Vmax. By performing a series of constant velocity shortening contractions, a force-velocity relationship can be determined.
During normal activity, muscles are often active while they are lengthening. Classic examples of this are walking, when the quadriceps (knee extensors) are active just after heel strike while the knee flexes, or setting an object down gently (the arm flexors must be active to control the fall of the object).
As the load on the muscle increases, it finally reaches a point where the external force on the muscle is greater than the force that the muscle can generate. Thus even though the muscle may be fully activated, it is forced to lengthen due to the high external load. This is referred to as an eccentric contraction (please remember that contraction in this context does not necessarily imply shortening). There are two main features to note regarding eccentric contractions. First, the absolute tensions achieved are very high relative to the muscle's maximum tetanic tension generating capacity (you can set down a much heavier object than you can lift). Second, the absolute tension is relatively independent of lengthening velocity. This suggests that skeletal muscles are very resistant to lengthening. The basic mechanics of eccentric contractions are still a source of debate since the cross-bridge theory that so nicely describes concentric contractions is not as successful in describing eccentric contractions.
A third type of muscle contraction, isometric contraction, is one in which the muscle is activated, but instead of being allowed to lengthen or shorten, it is held at a constant length. An example of an isometric contraction would be carrying an object in front of you. The weight of the object would be pulling downward, but your hands and arms would be opposing the motion with equal force going upwards. Since your arms are neither raising nor lowering, your biceps will be isometrically contracting.
12.4 Muscular Disorder:

These include spasms and injuries, as well as diseases such as muscular dystrophy and myasthenia gravis.

12.5 Homeostasis:
The property of either an open system or a closed system, especially a living organism, that regulates its internal environment so as to maintain a stable, constant condition. Multiple dynamic equilibrium adjustments and regulation mechanisms make homeostasis possible. The concept was created by Claude Bernard, often considered as the father of physiology, and published in 1865.