Lesson 2: Chemical, Cellular, and Tissue Level of Organization (BIOL 30143)

Lesson 2 Chemical, Cellular and Tissue level of Organization INTRODUCTION In this chapter you will learn how combinations of chemicals form cells, the smallest living units in the human body. We will also look at the chemical events that sustain life, which occur mostly inside cells. Cells are very small. A typical cell is only about 0.1 mm in diameter. As a result, no one could examine the structure of a cell until effective microscopes were invented in the 17th century. In 1665, Robert Hooke inspected thin slices of cork and found that they were made of millions of small, irregular units. In describing what he saw, Hooke used the term cell because the many small, bare spaces reminded him of the rooms, or cells, in a prison or monastery. The Latin term, cella, means a storeroom or chamber. Hooke saw only the outlines of the cells, and not the cells themselves, but he stimulated broad interest in the microscopic world and in cellular life. Moreover, you will learn how a variety of cell types arranged in various combinations form tissues, which are structures with discrete structural and functional properties. Although the human body contains trillions of cells, all of those cells can be categorized as belonging to one of four distinct groups of tissue. Tissues are simply groups of similar cells that perform a common function. The four categories of tissue are epithelial, connective, nervous, and muscular. These four types of tissue exist alone or in combinations to create an amazing array of structures. For example, organs consist of two, three, or even four types of tissue, all working together to fulfill a unique purpose. Tissue is also the connective fabric that holds the body’s structures together; it provides the body with its shape and also gives it the ability to move. 28 LEARNING OBJECTIVES 1. Distinguish between organic compounds and inorganic compounds. 2. Explain how the chemical properties of water make life possible. 3. Discuss the regulation of the cell life cycle. 4. Discuss the relationship between cell division and cancer. 5. Identify the four major types of tissues in the body and describe their roles. 6. Describe how cartilage and bone function as a supporting connective tissue. 7. Describe how injuries affect the tissues of the body; and 8. Describe how aging affects the tissues of the body. A. Chemical Level 1. Inorganic and Organic Compounds The human body is very complex, but it contains relatively few elements (Fig. 12). Just knowing the identity and quantity of each element in the body will not help you understand the body any more than only memorizing the alphabet will help you understand this textbook. Just as 26 letters can be combined to form thousands of different words in this book, only about 26 elements combine to form thousands of different chemical compounds in our bodies. These compounds make up the living cells that form the framework of the body and carry on all its life processes. Learning about the major classes of chemical compounds will help you to understand the structure and function of the human body. We now turn our attention to nutrients and metabolites. Figure 12: Principal Elements in the Human Body Nutrients are the substances from food that are necessary for normal physiological functions. Nutrients include carbohydrates, proteins, fats, vitamins, minerals, and water. Metabolites are substances that are involved in, or a byproduct of, metabolism. We can broadly categorize nutrients and metabolites as either inorganic or organic. Inorganic compounds generally do not contain 29 carbon and hydrogen atoms as their primary structural ingredients. In contrast, carbon and hydrogen always form the basis for organic compounds. The most important inorganic compounds in the body are (1) carbon dioxide, a byproduct of cell metabolism; (2) oxygen, an atmospheric gas required in important metabolic reactions; (3) water, which accounts for most of our body weight; and (4) inorganic acids, bases, and salts—compounds held together partially or completely by ionic bonds. In the next section, we focus on water, its properties, and how those properties establish the conditions necessary for life. Most of the other inorganic molecules and compounds in the body exist in association with water, the primary component of our body fluids. Both carbon dioxide and oxygen, for example, are gas molecules that are transported in body fluids. Also, all the inorganic acids, bases, and salts we will discuss are dissolved in body fluids. Figure 13: Classes of Inorganic and Organic Compounds 2. Physiological Systems Depend on Water Water (H2O) is the most important substance in the body. It makes up to two- thirds of total body weight. A change in the body’s water content can be fatal because virtually all physiological systems will be affected. Although water is 30 familiar to everyone, it has some highly unusual properties. These properties are due to the hydrogen bonding between nearby water molecules. Solubility. A remarkable number of inorganic and organic molecules are soluble, meaning they will dissolve or break up in water. The individual particles become distributed within the water, and the result is a solution—a uniform mixture of two or more substances. Reactivity. In our bodies, chemical reactions take place in water, but water molecules also take part in some reactions. High Heat Capacity. Heat capacity is the quantity of heat required to raise the temperature of a unit mass of a substance 1°C. Water has an unusually high heat capacity. Why? The reason is that water molecules in the liquid state are attracted to one another through hydrogen bonding. Water carries a great deal of heat away with it when it changes from a liquid to a gas. This feature explains the cooling effect of perspiration on the skin. An unusually large amount of heat energy is required to change the temperature of 1 g of water by 1°C. As a result, a large mass of water changes temperature slowly. This property is called thermal inertia. Thermal inertia helps stabilize body temperature because water accounts for up to two-thirds of the weight of the human body. Lubrication. Water is an effective lubricant because there is little friction between water molecules. So, even a thin layer of water between two opposing surfaces will greatly reduce friction between them. (That is why driving on wet roads can be tricky. Your tires may start sliding on a layer of water rather than maintaining contact with the road.) Within joints such as the knee, an aqueous solution prevents friction between the opposing surfaces. Similarly, a small amount of fluid in the body cavities prevents friction between internal organs, such as the heart or lungs, and the body wall. B. Cellular Level The human body contains trillions of cells. All our activities—from running to thinking—result from these combined and coordinated actions of millions or even billions of cells. We can summarize its basic concepts as follows: Cells are the building blocks of all plants and animals. All cells come from the division of preexisting cells. Cells are the smallest units that carry out life’s essential physiological functions. Each cell maintains homeostasis at the cellular level. Homeostasis at the level of the tissue, organ, organ system, and organism reflect the combined and coordinated actions of many cells. 1. Stages of a Cell’s Life Cycle The period between fertilization and physical maturity involves tremendous changes in organization and complexity. At fertilization, a single cell is all there is, but at maturity, your body has about 75 trillion cells. This amazing 31 transformation involves a form of cellular reproduction called cell division. A single cell divides to produce a pair of daughter cells, each half the size of the original. Before dividing, each daughter cell will grow to the size of the original cell. Even when development is complete, cell division continues to be essential to survival. Cells are highly adaptable, but physical wear and tear, toxic chemicals, temperature changes, and other environmental stresses can damage them. And, like individuals, cells age. The life span of a cell varies from hours to decades, depending on the type of cell and the stresses involved. Many cells apparently self-destruct after a certain period of time because specific “suicide genes” in the nucleus are activated. This genetically controlled death of cells is called apoptosis. Researchers have identified several genes involved in the regulation of this process. For example, a gene called bcl-2 produces a regulator protein that appears to prevent apoptosis and to keep a cell alive and functional. If something interferes with the function of this gene, the cell self-destructs. A typical cell does not live nearly as long as a typical person, cell populations must be maintained over time by cell division. For cell division to be successful, the genetic material in the nucleus must be duplicated accurately, and one copy must be distributed to each daughter cell. The duplication of the cell’s genetic material is called DNA replication, and nuclear division is called mitosis. Mitosis occurs during the division of somatic cells. The production of sex cells involves a different process, meiosis 2. Tumors and cancers are characterized by abnormal cell growth and division When the rates of cell division and growth exceed the rate of cell death, a tissue begins to enlarge. A tumor, or neoplasm, is a mass or swelling produced by abnormal cell growth and division. In a benign tumor, the cells usually remain within the epithelium (one of the four primary tissue types) or a connective tissue capsule. Such a tumor seldom threatens an individual’s life and can usually be surgically removed if its size or position disturbs tissue function. Cells in a malignant tumor no longer respond to normal controls. These cells do not remain confined within the epithelium or a connective tissue capsule but spread into surrounding tissues. The tumor of origin is called the primary tumor (or primary neoplasm), and the spreading process is called invasion. Malignant cells may also travel to distant tissues and organs and establish secondary tumors. This dispersion, called metastasis, is very difficult to control. Cancer is an illness that results from the abnormal proliferation of any of the cells in the body. It is characterized by mutations that disrupt normal cell regulatory controls and produce potentially malignant cells. Normal cells begin the path to 32 becoming malignant when a mutation occurs in a gene involved with cell growth, differentiation, or division. The modified genes are called oncogenes. Agents that cause a mutation (a change in DNA) are called mutagens. Cancer- causing agents, which include many mutagens, are known as carcinogens. Examples of carcinogens include radiation, chemicals, bacteria, and viruses. Some chemical carcinogens, such as alcohol and estrogen, are not directly mutagenic. Instead, they promote cancer by promoting rapid cell divisions, which increase the chances that a mutation will occur. Normal cells become malignant in a multistep process. For example, a mutation may occur in one cell, which is passed on to its daughter cells. One of those cells may undergo another mutation that speeds its rate of cell division. Further growth promoting mutations in one of those cells and its proliferating descendants may produce a primary tumor. The tumor now contains descendants of the original abnormal cell that have been selected for rapid growth. While these tumor cells are ultimately all descended from one abnormal cell, they are not identical to it due to their accumulated mutations. Figure 14: The Development of Cancer Cancer cells do not resemble normal cells. They have a different shape and typically become abnormally larger or smaller. Malignant tumor cells are also less subject to controls limiting adhesion and movement between adjacent cells and extracellular tissues. At first, the growth of the primary tumor distorts the tissue, but the basic tissue organization remains intact. Metastasis begins with invasion as malignant cells “break out” of the primary tumor and invade the surrounding tissue. They may then enter the lymphatic system and accumulate in nearby lymph nodes. When metastasis involves the penetration of blood vessels, the cancer cells circulate throughout the body. C. Tissue Level The human body contains trillions of cells, but only about 200 types of cells. To work efficiently, several different types of cells must coordinate their efforts. Cells working together form tissues—collections of specialized cells and cell products that carry 33 out a limited number of functions. The study of tissues is called histology. Histologists recognize four basic types of tissue: Epithelial tissue covers exposed surfaces, lines internal passageways and chambers, and forms glands. Connective tissue fills internal spaces, provides structural support for other tissues, transports materials within the body, and stores energy. Muscle tissue is specialized for contraction and includes the skeletal muscles of the body, the muscle of the heart, and the muscular walls of hollow organs. Neural tissue carries information from one part of the body to another in the form of electrical impulses. 1. Cartilage and bone provide a strong supporting framework Cartilage and bone are called supporting connective tissues because they provide a strong framework that supports the rest of the body. In these connective tissues, the matrix contains numerous fibers. In bone, it also contains deposits of insoluble calcium salts. 2. The three types of muscle tissue are skeletal, cardiac, and smooth There are three types of muscle tissue: (1) skeletal muscle, which forms the large muscles that produce gross body movements; (2) cardiac muscle, found in the heart, is responsible for circulating the blood; and (3) smooth muscle, found in the walls of visceral organs and a variety of other locations, where it provides elasticity, contractility, and support. 3. Response to Tissue injury Figure 15: Types of Muscle Tissue a. Inflammation Impact, abrasion, distortion, chemical irritation, infection by pathogenic organisms (such as bacteria or viruses), and extreme temperatures (hot 34 or cold) are all stimuli that can produce inflammation. Each of these stimuli kills cells, damages fibers, or injures the tissue in some way. Such changes alter the chemical composition of the interstitial fluid: Damaged cells release prostaglandins, proteins, and potassium ions, and the injury itself may have introduced foreign proteins or pathogens into the body. Damaged connective tissue activates mast cells, which release chemicals that stimulate the inflammatory response. Tissue conditions soon become even more abnormal. Necrosis is the tissue destruction that takes place after cells have been damaged or killed. It begins several hours after the original injury. Lysosomal enzymes cause the damage. Through widespread autolysis, lysosomes release enzymes that first destroy the injured cells and then attack surrounding tissues. The result may be pus, a collection of debris, fluid, dead and dying cells, and necrotic tissue components. An abscess is an accumulation of pus in an enclosed tissue space. b. Regeneration Each organ has a different ability to regenerate after injury. This ability is directly linked to the pattern of tissue organization in the injured organ. Epithelia, connective tissues (except cartilage), and smooth muscle tissue usually regenerate well, but skeletal and cardiac muscle tissues and neural tissues regenerate relatively poorly, if at all. The skin, which is dominated by epithelia and connective tissues, regenerates rapidly and completely after injury. In contrast, damage to the heart is much more serious. The connective tissues of the heart can be repaired, but most damaged cardiac muscle cells are replaced only by fibrous tissue. The permanent replacement of normal tissue by fibrous tissue is called fibrosis. Fibrosis is in muscle and other tissues may occur in response to injury, disease, or aging. 4. Aging and Tissue Structure Tissues change with age, and the speed and effectiveness of tissue repairs decrease. Repair and maintenance activities throughout the body slow down, and the rate of energy consumption in general declines. All these changes reflect various hormonal alterations that take place with age, often coupled with reduced physical activity and a more sedentary lifestyle. These factors combine to alter the structure and chemical composition of many tissues. 35 Link to Video Recording: Topic Website/s Chemical Level of https://www.khanacademy.org/science/biology/chemistry- Organization -of-life/elements-and-atoms/a/matter-elements-atoms- article https://www.youtube.com/watch?v=33s2KiirtKg https://www.youtube.com/watch?v=M_UtFDH879A Cellular Level of https://www.khanacademy.org/science/biology/structure- Organization of-a-cell https://www.youtube.com/watch?v=huEkTHz8imQ https://www.youtube.com/watch?v=s8DQm5rTtmI Tissue Level of https://www.youtube.com/watch?v=O0ZvbPak4ck Organization https://www.youtube.com/watch?v=UYUcbKs02wU Tissue Injuries https://www.youtube.com/watch?v=KvBt2G4yMx4 Activity 2 Name: ______________________________ Score: ________________ Course, Year and Section: _____________ Equivalent: ____________ A. Write True if the statement is correct, if false change the underlined word/s to make the sentence correct. Write your answer on the space provided. 1. Cells are the smallest units that carry out life’s essential physiological functions. ___________ 2. Hydrogen is the most important substance in the body because it makes up to two-thirds of total body weight. ____________ 3. Covid-19 is an illness that results from the abnormal proliferation of any of the cells in the body. ___________ 4. Necrosis is the tissue destruction that takes place after cells have been damaged or killed. ____________ 5. Muscle and bone are called supporting connective tissues because they provide a strong framework that supports the rest of the body. _____________ B. Fill in the Blanks 1. The _________________ muscle, found in the heart, is responsible for circulating the blood. 2. The permanent replacement of normal tissue by fibrous tissue is called __________. 3. __________________is an accumulation of pus in an enclosed tissue space. 36 4. A ___________ is a mass or swelling produced by abnormal cell growth and division. 5. _____________ carries information from one part of the body to another in the form of electrical impulses. 6. Genetically controlled death of cells is called __________________. 7. The study of tissues is called ______________. 8. ______________ is a collection of debris, fluid, dead and dying cells, and necrotic tissue components. 9. __________________ tissue fills internal spaces, provides structural support for other tissues, transports materials within the body, and stores energy. 10. The duplication of the cell’s genetic material is called ______________________. C. Critical Thinking and Application 1. During a lab practical, a student examines a tissue that is composed of densely packed protein fibers that are running parallel and form a cord. There are no striations, but small nuclei are visible. The student identifies the tissue as skeletal muscle. Why is the student’s choice wrong, and what tissue is he probably observing? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ ____________________________ 2. While in a chemistry lab, Jim accidentally spills a small amount of a caustic (burning) chemical on his arm. What changes in the characteristics of the skin would you expect to observe, and what would cause these changes? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ ____________________ _______________________________________________________________ _______________________________________________________________ ________ 37 3. One of the factors to which lie detectors respond is an increase in electrical skin conductance due to the presence of moisture. Explain the physiological basis for the use of this indicator. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ ________________________________ 4. Many people change the natural appearance of their hair, either by coloring it or by altering the degree of curl in it. Which layers of the hair do you suppose are affected by the chemicals added during these procedures? Why are the effects of the procedures not permanent? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ ________________________________ 5. Two patients are brought to the emergency room. One has cut his finger with a knife; the other has stepped on a nail. Which wound has a greater chance of becoming infected? Why? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ ________________________________ 38 VALUES INTEGRATION Values integration in anatomy and physiology education emphasizes the importance of connecting ethical considerations, core physiological concepts, and interdisciplinary knowledge. This approach enhances student understanding and application of complex biological systems. Ethical Integration in Physiology Integrating ethics into physiology curricula is crucial for developing responsible healthcare professionals. A workshop in Karnataka highlighted the relevance of this integration, although challenges such as institutional support and student engagement were noted. Core Concepts of Integration The Australian study identified 'Integration' as a core concept in physiology, emphasizing the interconnectedness of cells, tissues, and organ systems. This concept is essential for students to grasp the hierarchical organization of life, which should be taught in advanced semesters to facilitate deeper understanding. Interdisciplinary Teaching Approaches Combining anatomy, physiology, histology, and embryology fosters a holistic learning experience. A team-taught approach for the female reproductive system exemplifies how integrated content can enhance student comprehension. Additionally, cognitive integration strategies that link basic and clinical sciences can improve diagnostic performance in learners. 39 UNIT II THE MUSCULOSKELETAL SYSTEM Lesson 3 Skeletal System INTRODUCTION This chapter will give you a wider perspective on the functions and importance of skeletal system by examining the mechanisms involved with the growth, remodeling, and repair of the skeleton. The bones of the skeleton are more than just racks from which muscles hang. They have a variety of vital functions. In addition to supporting the weight of the body, bones work with muscles to maintain body position and to produce controlled, precise movements. Without the skeleton to pull against, contracting muscle fibers could not make us sit, stand, walk, or run. The skeleton may appear to be nothing more than a dry, nonliving framework for the body, but it is far from it. The 206 bones in the adult human body are actually dynamic living tissue. Bone constantly breaks down and rebuilds itself, not just during the growth phases of childhood, but throughout the life span. Bone is filled with blood vessels, nerves, and living cells; in addition, its interaction with other body systems is necessary not only for movement, but also for life itself. LEARNING OBJECTIVES 1. Describe the primary functions of the skeletal system. 2. Classify bones according to shape and internal organization, giving examples of each type, and explain the functional significance of each of the major types of bone markings. 3. Identify the cell types in bone and list their major functions. 4. Compare the structures and functions of compact bone and spongy bone. 40 5. Discuss the effects of exercise, hormones, and nutrition on bone development and on the skeletal system. 6. Describe the types of fractures and explain how fractures heal. Summarize the effects of the aging process on the skeletal system. 7. Identify the bones of the axial and appendicular skeleton, and specify their functions; and 8. Identify the bones of the upper and lower limbs, their functions, and their superficial features. A. Primary Functions Your skeletal system includes the bones of the skeleton and, the cartilages, ligaments, and other connective tissues that stabilize or interconnect the bones. This system has five primary functions: a. Support. The skeletal system provides structural support for the entire body. Individual bones or groups of bones provide a framework for the attachment of soft tissues and organs. b. Storage of Minerals and Lipids. Minerals are inorganic ions that contribute to the osmotic concentration of body fluids. Minerals also take part in various physiological processes, and several are important as enzyme cofactors. Calcium is the most abundant mineral in the human body. The calcium salts of bone are a valuable mineral reserve that maintains normal concentrations of calcium and phosphate ions in body fluids. In addition, the bones of the skeleton store energy as lipids in areas filled with yellow bone marrow. c. Blood Cell Production. Red blood cells, white blood cells, and other blood elements are produced in red bone marrow, which fills the internal cavities of many bones. We will describe blood cell formation when we examine the cardiovascular and lymphatic systems. d. Protection. Skeletal structures surround many soft tissues and organs. The ribs protect the heart and lungs, the skull encloses the brain, the vertebrae shield the spinal cord, and the pelvis cradles digestive and reproductive organs. e. Leverage. Many bones function as levers that can change the magnitude and direction of the forces generated by skeletal muscles. The movements produced range from the precise motion of a fingertip to changes in the position of the entire body. 41 B. Bone Shapes Figure 16: Bone Shapes C. Bone Markings The surfaces of each bone in your body have characteristic features. Elevations or projections form where tendons and ligaments attach, and where adjacent bones articulate (that is, at joints). Depressions, grooves, and tunnels in bone are sites where blood vessels or nerves lie alongside or penetrate the bone. Detailed examination of these bone markings, or surface features, can yield an abundance of anatomical information. For example, anthropologists, criminologists, and pathologists can often determine the size, age, sex, and general appearance of an individual on the basis of incomplete skeletal remains. 42 Figure 17: Bone Markings 43 D. Bone Structure Figure 18 introduces the anatomy of the femur, the long bone of the thigh. This representative long bone has an extended tubular shaft, or diaphysis. At each end is an expanded area known as the epiphysis. The diaphysis is connected to each epiphysis at a narrow zone known as the metaphysis. The wall of the diaphysis consists of a layer of compact bone. Compact bone, or dense bone, is relatively solid. It forms a sturdy protective layer that surrounds a central space called the medullary cavity (medulla, innermost part), or marrow cavity. Figure 18: The structure of femur in longitudinal section E. Bone Cells Bone contains four types of cells: osteocytes, osteoblasts, osteogenic cells, and osteoclasts. a. Osteocytes are mature bone cells that make up most of the cell population. Osteoblasts (produce new bone matrix in a process called ossification, or osteogenesis. b. Osteoblasts make and release the proteins and other organic components of the matrix. c. Bone contains small numbers of mesenchymal cells called osteogenic cells or osteoprogenitor cells. These squamous stem cells divide to produce daughter cells that differentiate into osteoblasts. d. Osteoclasts are cells that absorb and remove bone matrix. They are large cells with 50 or more nuclei. 44 Figure 19: Bone Cells F. Compact Bones and Spongy Bones Compact bone functions to protect, support, and resist stress. It is thickest where stresses arrive from a limited range of directions. Spongy bone provides some support and stores marrow. Spongy bone is found where bones are not heavily stressed or where stresses arrive from many directions. The trabeculae are oriented along stress lines and extensively cross-braced. G. Bone Development The growth of the skeleton determines the size and proportions of your body. The bony skeleton begins to form about six weeks after fertilization, when the embryo is approximately 12 mm (0.5 in.) long. (At this stage, the existing skeletal elements are made of cartilage.) During subsequent development, the bones undergo a tremendous increase in size. Bone growth continues through adolescence, and portions of the skeleton generally do not stop growing until about age 25. Ossification or osteogenesis refers specifically to the formation of bone. H. Bone Fracture Despite its mineral strength, bone can crack or even break if subjected to extreme loads, sudden impacts, or stresses from unusual directions. The damage is called a fracture. Most fractures heal even after severe damage, if the blood supply and the cellular components of the endosteum and periosteum survive. 45 Figure 20: Bone Fractures I. Axial Skeleton The axial skeleton forms the longitudinal axis of the body. The axial skeleton has 80 bones, about 40 percent of the bones in the human body: The skull (8 cranial bones and 14 facial bones). Bones associated with the skull (6 auditory ossicles and the hyoid bone). The vertebral column (24 vertebrae, the sacrum, and the coccyx). The thoracic cage (the sternum and 24 ribs). The axial skeleton provides a framework that supports and protects the brain, the spinal cord, and the thoracic and abdominal organs. It also provides an extensive surface area for the attachment of muscles that (1) adjust the positions of the head, neck, and trunk; (2) perform respiratory movements; and (3) stabilize or position parts of the appendicular skeleton, which supports the limbs. 46 Figure 21: Axial Skeleton 47 1. Cranial and Facial Subdivisions of the Skull 48 Figure 22: Cranial and Facial Subdivisions of the Skull 2. Vertebral Columns The adult vertebral column, or spine, consists of 26 bones: the vertebrae (24), the sacrum (1), and the coccyx (1), or tailbone. The vertebrae provide a column of support, bearing the weight of the head, neck, and trunk and ultimately transferring the weight to the appendicular skeleton of the lower limbs. The vertebrae also protect the spinal cord and help maintain an upright body position, as when we sit or stand. The total length of the vertebral column of an adult averages 71 cm (28 in.). 49 Figure 23: The Vertebral Column 3. Kyphosis, Lordosis, and Scoliosis The vertebral column must move, balance, and support the trunk and head. Conditions or events that damage the bones, muscles, and/or nerves can result in distorted shapes and impaired function. In kyphosis, the normal thoracic curvature becomes exaggerated posteriorly, producing a “round-back” appearance. This condition can be caused by (1) osteoporosis with compression fractures affecting the anterior portions of vertebral bodies, (2) chronic contractions in muscles that insert on the vertebrae, or (3) abnormal vertebral growth. In lordosis, or “swayback,” both the abdomen and buttocks protrude abnormally. The cause is an anterior exaggeration of the lumbar curvature. This may occur during pregnancy or result from abdominal obesity or weakness in the muscles of the abdominal wall. Scoliosis is an abnormal lateral curvature of the spine in one or more of the movable vertebrae. Scoliosis is the most common distortion of the spinal curvature. 50 Figure 24: Vertebral Column Abnormal Conditions 4. Thoracic Cage Figure 25: Thoracic or Rib Cage J. Appendicular Skeleton The appendicular skeleton includes the bones of the limbs and the supporting bone (pectoral and pelvic) girdles that connect them to the trunk). To appreciate the role 51 of the appendicular skeleton in your life, make a mental list of all the things you have done with your arms or legs today. Standing, walking, writing, turning pages, eating, dressing, shaking hands, and texting—the list quickly becomes unwieldy. Your axial skeleton protects and supports internal organs and takes part in vital functions, such as breathing. But your appendicular skeleton lets you manipulate objects and move from place to place. Figure 26: Appendicular Skeleton 1. Clavicle and Scapula The clavicles are S-shaped bones that originate at the superior, lateral border of the manubrium of the sternum, lateral to the jugular notch. From the pyramid-shaped 52 sternal end, each clavicle curves laterally and posteriorly for about half its length. It then forms a smooth posterior curve to articulate with a process of the scapula, the acromion. The flat, acromial end of the clavicle is broader than the sternal end Figure 27: Right Clavicle The anterior surface of the body of each scapula forms a broad triangle. The three sides of the triangle are the superior border; the medial border, or vertebral border; and the lateral border, or axillary border (axilla, armpit). Muscles that position the scapula attach along these edges. The corners of the triangle are called the superior angle, the inferior angle, and the lateral angle. 53 Figure 28: Right Scapula 2. Humerus, Radius and Ulna The arm, or brachium, contains only one bone, the humerus, which extends from the scapula to the elbow. At the proximal end of the humerus, the round head articulates with the scapula. At the proximal end of the humerus, the round head articulates with the scapula. The prominent greater tubercle is a rounded projection on the lateral surface of the epiphysis, near the margin of the humeral head. The greater tubercle establishes the lateral contour of the shoulder. You can verify its position by feeling for a bump located a few centimeters from 54 the tip of the acromion. The lesser tubercle is a smaller projection that lies on the anterior, medial surface of the epiphysis, separated from the greater tubercle by the intertubercular groove, or intertubercular sulcus Figure 29: Right Humerus The radius is the lateral bone of the forearm). The disc shaped radial head, or head of the radius, articulates with the capitulum of the humerus. During flexion, the radial head swings into the radial fossa of the humerus. A narrow neck extends from the radial head to the radial tuberosity. This tuberosity marks the attachment site of the biceps brachii muscle, a large muscle on the anterior surface of the arm. The ulna and radius are parallel bones that support the forearm or antebrachium. In the anatomical position, the ulna lies medial to the radius. The olecranon, the superior end of the ulna, is the point of the elbow. On the anterior surface of the proximal epiphysis, the trochlear notch of the ulna articulates with the trochlea of the humerus at the elbow joint. shows the trochlear notch of the ulna in a lateral view. Figure 30: Right Radius and Ulna 3. Carpal Bones The carpus, or wrist, contains eight carpal bones. These bones form two rows, one with four proximal carpal bones and the other with four distal carpal bones. 55 Each hand has 14 finger bones, or phalanges. The first finger, known as the pollex, or thumb, has two phalanges (proximal and distal). Each of the other four fingers has three phalanges (proximal, middle, and distal). Figure 31: Bones of the Right Wrist and Hand 4. Pelvic Girdle The pelvic girdle consists of the paired hip bones, also called the coxal bones or pelvic bones. Each hip bone forms by the fusion of three bones: an ilium, an ischium, and a pubis. 56 Figure 32: Right Hip Bone. The Right and Left Hip Bones make up the pelvic girdle.and right hip bones make up the pelvic girdle. Male Female 5. Figure Femur and 33: Pelvis Patella difference between Male and Female right hip bones make up the pelvic girdle. The femur is the longest and heaviest bone in the body. It articulates with the hip bone at the hip joint and with the tibia of the leg at the knee joint while 57 patella is a large sesamoid bone that forms within the tendon of the quadriceps femoris, a group of muscles that extend (straighten) the knee. Figure 34: Right Femur right hip bones make up the pelvic girdle. Figure 35: Right Patella right hip bones make up the pelvic girdle. 58 6. Tibia and Fibula The tibia, or shinbone, is the large medial bone of the leg. The medial and lateral condyles of the femur articulate with the medial and lateral tibial condyles at the proximal end of the tibia. The slender fibula parallels the lateral border of the tibia. The head of the fibula articulates with the tibia. Figure 36: Right Tibia and Fibulat hip bones make up the pelvic girdle. 7. Tarsal Bones The ankle, or tarsus, consists of seven tarsal bones. The large talus transmits the weight of the body from the tibia toward the toes. The calcaneus, or heel bone, is the largest of the tarsal bones. When you stand normally, most of your weight is transmitted from the tibia, to the talus, to the calcaneus, and then to the ground. The posterior portion of the calcaneus is a rough, knob-shaped projection. This is the attachment site for the calcaneal tendon (Achilles tendon), which arises at the calf muscles. 59 The metatarsal bones are five long bones that form the distal portion of the foot, or metatarsus. The phalanges, or toe bones, have the same anatomical organization as the fingers. The toes contain 14 phalanges. The hallux, or great toe, has two phalanges (proximal and distal). The other four toes have three phalanges apiece (proximal, middle, and distal). Figure 37: Bones of the Ankle and Foot bones make up the pelvic girdle. Link to Video Recording: Topic Website/s https://www.youtube.com/watch?v=f-FF7Qigd3U https://www.innerbody.com/image/skelfov.html https://www.healthline.com/human-body- Skeletal System maps/skeletal-system#conditions https://www.khanacademy.org/science/high- school-biology/hs-human-body-systems/hs-the- 60 musculoskeletal-system/v/skeletal-structure-and- function Axial Skeleton https://www.youtube.com/watch?v=KyMCmIpKuCA Appendicular Skeleton https://www.youtube.com/watch?v=eZ4TydXGy9k https://www.youtube.com/watch?v=TVsm06jzpmo https://courses.lumenlearning.com/boundless- ap/chapter/diseases-and-disorders-of-the-skeletal- Diseases of the Skeletal system/ System https://www.khanacademy.org/test- prep/mcat/biological-sciences-practice/biological- sciences-practice-tut/e/disorders-of-the-skeletal- system-and-bone-remodeling- Activity 3 Name: ______________________________ Score: ________________ Course, Year and Section: _____________ Equivalent: ____________ A. Identification. Write your answer on the space provided. 1. The only one bone that extends from the scapula to the elbow. _________________ 2. Total number of finger bones, or phalanges of right and left hand. _______________ 3. The S-shaped bone that originates at the superior, lateral border of the manubrium of the sternum, lateral to the jugular notch. ___________________ 4. Parallel bones that support the forearm or antebrachium. _____________________ 5. The largest of the tarsal bones. ______________________ 6. The normal thoracic curvature becomes exaggerated posteriorly, producing a “round-back” appearance. _____________________ 7. These bone shapes are boxlike in appearance. _______________________ 8. The longest and heaviest bone in the body. _______________________ 9. Cells that absorb and remove bone matrix. ______________________ 10. A primary curve that accommodates the thoracic organs. _____________________ 11. Total number of adult human bones. ____________________ 61 12. Five long bones that form the distal portion of the foot, or metatarsus. ____________ 13. Total ribs of the human body. __________________ 14. Total number of appendicular skeletons. _____________________ 15. It includes the bones of the limbs and the supporting bone (pectoral and pelvic) girdles that connect them to the trunk). ____________________ 16. Abnormal lateral curvature of the spine in one or more of the movable vertebrae and the most common distortion of the spinal curvature. __________________ 17. Total number of thoracic vertebrae. __________________ 18. Bone that protects the head especially the brain from injury. _________________ 19. Formation of bones. ________________________ 20. It functions to protect, support, and resist stress. It is thickest where stresses arrive from a limited range of directions. _______________________ 21. Mature bone cells that make up most of the cell population. __________________ 22. It provides some support, stores marrow and found where bones are not heavily stressed or where stresses arrive from many directions. ___________________ 23. The inferior part of the vertebral column known as tail bone. ________________ 24. An anterior exaggeration of the lumbar curvature that may occur during pregnancy or result from abdominal obesity or weakness in the muscles of the abdominal wall. _____________________ 25. A large sesamoid bone that forms within the tendon of the quadriceps femoris. _____________________ B. Skeleton Mastery. Using the whole space below, draw a skeleton and label at least 100 bone parts. 62 C. Critical Thinking and Application 1. Why would a person suffering from osteoporosis be more likely to suffer a hip fracture than a broken shoulder? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ ____________________________________ 2. Archaeologists find the pelvis of a primitive human and are able to identify the sex, the relative age, and some physical characteristics of the individual. How is this possible from only the pelvis? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ ____________________________________ 3. Mary is in her last month of pregnancy and is suffering from lower back pains. Since she is carrying excess weight in front of her, she wonders why her back hurts. How do you explain to her scientifically the situation? _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ ___________________________________________________ 63 Lesson 4 Joints and Body Movements INTRODUCTION In this chapter we consider the ways bones interact wherever they interconnect. In the last chapter, you learned the individual bones of the skeleton. These bones provide strength, support, and protection for softer tissues of the body. However, your daily life demands more of the skeleton—it must also facilitate and adapt to body movements. Think of your activities in a typical day: You breathe, talk, walk, sit, stand, and change positions countless times. In each case, your skeleton is directly involved. Movements can occur only at joints, or articulations, where two bones meet, because the bones of the skeleton are inflexible. The characteristic structure of a joint determines the type and amount of movement that may take place. Each joint reflects a compromise between the need for strength and the need for mobility. In this chapter we compare the relationships between articular form and function. We consider several examples that range from relatively immobile but very strong joints (the intervertebral joints) to a highly mobile but relatively weak joint (the shoulder). LEARNING OBJECTIVES 1. Contrast the major categories of joints and explain the relationship between structure and function for each category. 2. Describe the basic structure of a synovial joint and describe common synovial joint accessory structures and their functions. 3. Describe how the anatomical and functional properties of synovial joints permit movements of the skeleton. Describe the joints between the vertebrae of the vertebral column. 4. Describe the structure and function of the shoulder joint and the elbow joint. 5. Describe the structure and function of the hip joint and the knee joint. 6. Describe the effects of aging on joints, and discuss the most common age-related clinical problems for joints; and 7. Explain the functional relationships between the skeletal system and other body systems. A. Joints We use two classification methods to categorize joints. The first is the one we will use in this chapter. It is a functional scheme because it is based on the amount of movement possible, a property known as the range of motion (ROM). Each functional 64 group is further subdivided primarily on the basis of the anatomical structure of the joint a. An immovable joint is a synarthrosis. A synarthrosis can be fibrous or cartilaginous, depending on the nature of the connection. Over time, the two bones may fuse. b. A slightly movable joint is an amphiarthrosis. An amphiarthrosis is either fibrous or cartilaginous, depending on the nature of the connection between the opposing bones. c. A freely movable joint is a diarthrosis, or synovial joint. Diarthroses are subdivided according to the movement permitted. The second classification scheme relies solely on the anatomy of the joint, without regard to the degree of movement permitted. Using this framework, we classify joints as fibrous, cartilaginous, bony, or synovial. Bony joints form when fibrous or cartilaginous joints ossify. The ossification may be normal or abnormal, and may occur at various times in life. The two classification schemes are loosely correlated. We see many anatomical patterns among immovable or slightly movable joints, but there is only one type of freely movable joint—synovial joints. All synovial joints are diarthroses. We will use the functional classification rather than the anatomical one because our primary interest is how joints work. 65 Figure 38: Functional and Structural Classification of Jointsones make up the pelvic girdle. 1. Synovial Joints Synovial joints are freely movable and classified as diarthroses. A two-layered joint capsule, also called an articular capsule, surrounds the synovial joint. Under normal conditions, the bony surfaces at a synovial joint cannot contact one another, because special articular cartilage covers the articulating surfaces. Figure 39: Structure of a synovial jointones make up the pelvic girdle. 66 2. Synovial Fluid, Ligaments, Tendons and Bursae Synovial fluid is a clear, viscous solution with the consistency of egg yolk or heavy molasses. Synovial fluid resembles interstitial fluid, but contains proteoglycans with a high concentration of hyaluronan (hyaluronic acid) secreted by fibroblasts of the synovial membrane. The capsule that surrounds the entire joint is continuous with the periostea of the articulating bones. Accessory ligaments support, strengthen, and reinforce synovial joints. Capsular ligaments, or intrinsic ligaments, are localized thickenings of the joint capsule. Extrinsic ligaments are separate from the joint capsule. These ligaments may be located either inside or outside the joint capsule, and are called intracapsular or extracapsular ligaments, respectively. Tendons are not part of the joint itself, but tendons passing across or around a joint may limit the joint’s range of motion and provide mechanical support for it. For example, tendons associated with the muscles of the arm help brace the shoulder joint. Bursae are small, thin, fluid filled pockets in connective tissue. They contain synovial fluid and are lined by a synovial membrane. Bursae may be connected to the joint cavity or separate from it. They form where a tendon or ligament rubs against other tissues. 3. Types of Movements at Synovial Joints Gliding Movement In gliding, two opposing surfaces slide past one another. Gliding occurs between the surfaces of articulating carpal bones, between tarsal bones, and between the clavicles and the sternum. The movement can occur in almost any direction, but the amount of movement is slight, and rotation is generally prevented by the capsule and associated ligaments. 67 Figure 40: Classification of Synovial Jointsup the pelvic girdle. Angular Movement Examples of angular movement include flexion, extension, abduction, adduction, and circumduction. Descriptions of these movements are based on reference to an individual in the anatomical position. Flexion and Extension. Flexion is movement in the anterior–posterior plane that decreases the angle between articulating bones. Extension occurs in the same plane, but it increases the angle between articulating bones Abduction and Adduction. Abduction is movement away from the longitudinal axis of the body in the frontal plane. For example, swinging 68 the upper limb to the side is abduction of the limb. Moving it back to the anatomical position is adduction. Adduction of the wrist moves the heel of the hand and fingers toward the body, whereas abduction moves them farther away. Circumduction. Recall the special type of angular movement, circumduction, from our model. Moving your arm in a loop is circumduction, as when you draw a large circle on a whiteboard. Your hand moves in a circle, but your arm does not rotate. Figure 41: Angular Movements make up the pelvic girdle. 69 Rotational Movement Rotation of the head may involve left rotation or right rotation. Limb rotation by reference to the longitudinal axis of the trunk. During medial rotation, also known as internal rotation or inward rotation, the anterior surface of a limb turns toward the long axis of the trunk. The reverse movement is called lateral rotation, external rotation, or outward rotation. The proximal joint between the radius and the ulna permits rotation of the radial head. As the shaft of the radius rotates, the distal epiphysis of the radius rolls across the anterior surface of the ulna. This movement, called pronation, turns the wrist and hand from palm facing front to palm facing back. The opposing movement, in which the palm is turned anteriorly, is supination. The forearm is supinated in the anatomical position. Figure 42: Rotational Movements make up the pelvic girdle. Special Movements Inversion is a twisting movement of the foot that turns the sole inward, elevating the medial edge of the sole. The opposite movement is called eversion. Dorsiflexion is flexion at the ankle joint and elevation of the sole, as when you dig in your heel. Plantar flexion, the opposite movement, extends the ankle joint and elevates the heel, as when you stand on tiptoe. However, 70 it is also acceptable (and simpler) to use “flexion and extension at the ankle,” rather than “dorsiflexion and plantar flexion.” Opposition is movement of the thumb toward the surface of the palm or the pads of other fingers. Opposition enables you to grasp and hold objects between your thumb and palm. Reposition is the movement that returns the thumb and fingers from opposition. Protraction is moving a body part anteriorly in the horizontal plane. Retraction is the reverse movement. You protract your jaw when you put your chin forward, and you retract your jaw when you return it to its normal position. Elevation and depression take place when a structure moves in a superior or an inferior direction, respectively. You depress your mandible when you open your mouth, and you elevate your mandible as you close your mouth. Another familiar elevation takes place when you shrug your shoulders. Lateral flexion occurs when your vertebral column bends to the side. This movement is most pronounced in the cervical and thoracic regions. Figure 43: Special Movements make up the pelvic girdle. 71 B. Shoulder and Elbow 1. The Shoulder Joint The shoulder joint, or glenohumeral joint, permits the greatest range of motion of any joint. It is also the most frequently dislocated joint, demonstrating the principle that stability must be sacrificed to obtain mobility. The shoulder is a ball-and socket diarthrosis formed by the articulation of the head of Figure 44: Shoulder Jointmake up the pelvic girdle. the humerus with the glenoid cavity of the scapula 2. The Elbow Joint The elbow joint is a complex hinge joint that involves the humerus, radius, and ulna. The largest and strongest articulation at the elbow is the humeroulnar joint, where the trochlea of the humerus articulates with the trochlear notch of the ulna. This joint works like a door hinge, with physical limitations imposed on the range of motion. The elbow joint is extremely stable because (1) the bony surfaces of the humerus and ulna interlock, (2) a single, thick articular capsule surrounds both the humeroulnar and proximal radioulnar joints, and (3) strong ligaments reinforce the articular capsule. Figure 45: Elbow Jointmake up the pelvic girdle. 72 3. Hip and Knee Joint The hip joint is a sturdy ball-and-socket diarthrosis that permits flexion, extension, adduction, abduction, circumduction, and rotation. Figure 46: Right Hip Jointmake up the pelvic girdle. The knee joint functions as a hinge, but the joint is far more complex than the elbow or even the ankle. The rounded condyles of the femur roll across the superior surface of the tibia, so the points of contact are constantly changing. The joint permits flexion, extension, and very limited rotation. 73 Figure 47: Right Knee Jointmake up the pelvic girdle. 4. Joints of the Appendicular Skeleton Figure 48: Joints of the Appendicular Skeletonmake up the pelvic girdle. 74 Link to Video Recording: Topic Website/s https://www.visiblebody.com/learn/skeleton/joints- and-ligaments https://www.khanacademy.org/science/high-school- Joints of the Human Body biology/hs-human-body-systems/hs-the- musculoskeletal-system/v/ligaments-tendons-and- joints https://www.youtube.com/watch?v=bfiUnhAHt8Q https://www.youtube.com/watch?v=nAAnhJKDZ7g https://www.youtube.com/watch?v=8hqyQIyenxA Types of Movements of https://www.youtube.com/watch?v=aRaLjN2cTYo Synovial Joints https://www.youtube.com/watch?v=X5RUFXZZBH4 https://www.youtube.com/watch?v=69u4kDl7OBc https://www.youtube.com/watch?v=SZ1CK7xn0V0 https://www.youtube.com/watch?v=EB5zxdAQGzU Diseases and Injuries of the https://www.khanacademy.org/science/health-and- Joints medicine/muscular-skeletal-diseases Activity 4 Name: ______________________________ Score: ________________ Course, Year and Section: _____________ Equivalent: ____________ A. Matching Type. Match Column A with Column B. Write the letter of your answer on the space provided. ______1. glenohumeral joint a. retraction ______2. moving your arm in a loop b. immovable joint ______3. opposite of inversion c. knee joint ______4. amphiarthrosis d. synovial joint ______5. condylar joints e. plantar flexion ______6. capsular ligaments f. synovial fluid ______7. synarthrosis g. circumduction ______8. diarthrosis h. shoulder joint ______9. opposite of protraction i. plane joints 75 ______10. opposite of extension j. ellipsoidal joints ______11. gliding joints k. slightly movable joint ______12. clear and viscous solution l. intrinsic ligaments ______13. opposite of dorsiflexion m. biaxial ______14. movements in two planes n. depression ______15. opposite of elevation o. flexion p. eversion B. Enumeration. List down all the correct answers. 1. Five movements of the radius/carpal bones a. _____________________ b. _____________________ c. _____________________ d. _____________________ e. _____________________ 2. Five movements of the hip bone/femur a. _____________________ b. _____________________ c. _____________________ d. _____________________ e. _____________________ 3. Four movements of tibia and fibula with talus a. _____________________ b. _____________________ c. _____________________ d. _____________________ 4. Movement of phalanx a. _____________________ C. Critical Thinking and Application 1. While playing tennis, Marco “turns his ankle.” He experiences swelling and pain. After being examined, he is told that he has no ruptured ligaments and that the structure of the ankle is not affected. On the basis of the signs and symptoms and the examination results, what happened to Marco’s ankle? __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ 76 2. When playing a contact sport, which injury would you expect to occur more frequently, a dislocated shoulder or a dislocated hip? Why? __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ ________________________ __________________________________________________________________ __________________________________________________________________ ________ 77 Lesson 5 Muscular System INTRODUCTION In this chapter we describe the gross anatomy of the muscular system and consider functional relationships between muscles and bones of the body. Most skeletal muscle fibers contract at similar rates and shorten to the same degree, but variations in microscopic and macroscopic organization can dramatically affect the power, range, and speed of movement produced when muscles contract. In addition, this chapter will also discuss muscle tissue, one of the four primary tissue types, with particular attention to skeletal muscle tissue. We examine the histological and physiological characteristics of skeletal muscle cells and relate those features to the functions of the entire tissue. We also give an overview of the differences among skeletal, cardiac, and smooth muscle tissues. LEARNING OBJECTIVES 1. Specify the functions of skeletal muscle tissue. 2. Describe the organization of muscle at the tissue level. 3. Identify the structural and functional differences between skeletal muscle fibers and cardiac muscle cells. 4. Identify the structural and functional differences between skeletal muscle fibers and smooth muscle cells and discuss the roles of smooth muscle tissue in systems throughout the body. 5. Describe the classes of levers and explain how they make muscles more efficient. Predict the actions of a muscle based on its origin and insertion and explain how muscles interact to produce or oppose movements. 6. Explain how the name of a muscle can helps identify its location, appearance, or function. 7. Identify the principal axial muscles of the body, plus their origins, insertions, actions, and innervation. 78 8. Identify the principal appendicular muscles of the body, plus their origins, insertions, actions, and innervation, and compare the major functional differences between the upper and lower limbs. 9. Identify age-related changes of the muscular system; and 10. Explain the functional relationship between the muscular system and other body systems and explain the role of exercise in producing various responses in other body systems. A. Primary Functions The muscular system performs six critical functions for the human body. It produces skeletal movement, helps maintain posture and body position, supports soft tissues, guards body entrances and exits, helps maintain body temperature, and stores nutrients. B. Skeletal Muscles Muscle tissue consists chiefly of muscle cells that are highly specialized for contraction. Our bodies contain three types of muscle tissue: (1) skeletal muscle, (2) cardiac muscle, and (3) smooth muscle. Skeletal muscles are organs composed mainly of skeletal muscle tissue, but they also contain connective tissues, nerves, and blood vessels. Each cell in skeletal muscle tissue is a single muscle fiber. Skeletal muscles attach directly or indirectly to bones. Figure 49: Organization of Skeletal Musclesmake up the pelvic girdle. 79 1. Layers of Muscle Connective Tissues Each muscle has three layers of connective tissue: (1) an epimysium, (2) a perimysium, and (3) an endomysium. The epimysium is a dense layer of collagen fibers that surrounds the entire muscle. It separates the muscle from nearby tissues and organs. The epimysium is connected to the deep fascia, a dense connective tissue layer. The perimysium divides the skeletal muscle into a series of compartments. Each compartment contains a bundle of muscle fibers called a fascicle. In addition to collagen and elastic fibers, the perimysium contains blood vessels and nerves that supply the muscle fibers within the fascicles. Each fascicle receives branches of these blood vessels and nerves. Within a fascicle, the delicate connective tissue of the endomysium surrounds the individual skeletal muscle cells, called muscle fibers, and loosely interconnects adjacent muscle fibers. This flexible, elastic connective tissue layer contains (1) capillary networks that supply blood to the muscle fibers; (2) myosatellite cells, stem cells that help repair damaged muscle tissue; and (3) nerve fibers that control the muscle. All these structures are in direct contact with the individual muscle fibers. C. The nervous system communicates with skeletal muscles at the neuromuscular junction Skeletal muscle fibers begin contraction with the release of their internal stores of calcium ions. That release is under the control of the nervous system. Communication between a neuron and another cell occurs at a synapse. When the other cell is a skeletal muscle fiber, the synapse is known as a neuromuscular junction (NMJ), or myoneural junction. The NMJ is made up of an axon terminal (synaptic terminal) of a neuron, a specialized region of the sarcolemma called the motor end plate, and, in between, a narrow space called the synaptic cleft. Motor neurons of the central nervous system (brain and spinal cord) carry instructions in the form of action potentials to skeletal muscle fibers. 80 Figure 50: Steps Involved in Skeletal Muscle Contraction and Relaxation. 81 D. Muscle Contractions 1. Isotonic and Isometric Contractions We can classify muscle contractions as isotonic or isometric on the basis of their pattern of tension production. Isotonic Contractions. In an isotonic contraction, tension increases and the skeletal muscle’s length changes. Lifting an object off a desk, walking, and running involve isotonic contractions. There are two types of isotonic contractions: concentric and eccentric. In a concentric contraction, the muscle tension exceeds the load and the muscle shortens. In an eccentric contraction, the peak tension developed is less than the load, and the muscle elongates due to the contraction of another muscle or the pull of gravity Isometric Contractions. In an isometric contraction (metric, measure), the muscle does not change length, and the tension produced never exceeds the load. Examples of isometric contractions include carrying a bag of groceries and holding our heads up. Many of the reflexive muscle contractions that keep your body upright when you stand or sit involve isometric contractions of muscles that oppose the force of gravity. 2. Adenosine Triphosphate (ATP) provides energy for muscle contraction Adenosine triphosphate, also known as ATP, is a molecule that carries energy within cells. It is the main energy currency of the cell, and it is an end product of the processes of photophosphorylation (adding a phosphate group to a molecule using energy from light), cellular respiration, and fermentation. A single muscle fiber may contain 15 billion thick filaments. When that muscle fiber is actively contracting, each thick filament breaks down around 2500 ATP molecules per second. Even a small skeletal muscle contains thousands of muscle fibers, so the ATP demands of a contracting skeletal muscle are enormous. In practical terms, the demand for ATP in a contracting muscle fiber is so high that it would be impossible to have all the necessary energy available as ATP before the contraction begins. Instead, a resting muscle fiber contains only enough ATP and other high-energy compounds to sustain a contraction until additional ATP can be generated. Throughout the rest of the contraction, the muscle fiber will generate ATP at roughly the same rate as it is used. 82 E. Classification of Skeletal Muscles 1. Parallel muscle – the fascicles are parallel to the long axis of the muscle. Most of the skeletal muscles in the body are parallel muscles. 2. Convergent muscle – muscle fascicles extending over a broad area come together, or converge, on a common attachment site. 3. Pennate muscle – the fascicles form a common angle with the tendon. Because the muscle fibers pull at an angle, contracting pennate muscles do not move their tendons as far as parallel muscles do. 4. Circular muscle, or sphincter – the fascicles are concentrically arranged around an opening. When the muscle contracts, the diameter of the opening becomes smaller. Figure 51: Muscle Type Based on Pattern of Fascicle Organization F. Classes of Levers Skeletal muscles do not work in isolation. For muscles attached to the skeleton, the nature and site of the connection determine the force, speed, and range of the movement. Attaching the muscle to a lever can modify the force, speed, or direction of movement produced by muscle contraction. A lever is a rigid structure—such as a board, a crowbar, or a bone—that moves on a fixed point called the fulcrum. A lever moves when pressure called an applied force 83 is sufficient to overcome any load that would otherwise oppose or prevent such movement. In the body, each bone is a lever and each joint is a fulcrum. Muscles provide the applied force. The load can vary from the weight of an object held in the hand to the weight of a limb or the weight of the entire body, depending on the situation. The important thing about levers is that they can change (1) the direction of an applied force, (2) the distance and speed of movement produced by an applied force, and (3) the effective strength of an applied force. Figure 52: he Three Classes of Levers There are three classes of levers. We find examples of each in the human body. A pry bar or crowbar is an example of a first-class lever. In such a lever, the fulcrum (F) lies between the applied force (AF) and the load (L). The body has few first-class levers. In a second-class lever, the load lies between the applied force and the fulcrum. A familiar example is a loaded wheelbarrow. The weight is the load, and the upward lift on the handle is the applied force. 84 In a third-class lever, such as a catapult, the applied force is between the load and the fulcrum. Third-class levers are the most common levers in the body. The effect is the reverse of that for a second-class lever: Speed and distance traveled are increased at the expense of effective force. G. Origin, Insertion and Actions of Muscles The place where the fixed end attaches to a bone, cartilage, or connective tissue is called the origin of the muscle. The site where the movable end attaches to another structure is called the insertion of the muscle. The origin is typically proximal to the insertion. When a muscle contracts, it produces a specific action, or movement. We describe muscles as follows, based on their functions: An agonist, or prime mover, is a muscle whose contraction is mostly responsible for producing a particular movement. The biceps brachii muscle is an agonist that produces flexion at the elbow. An antagonist is a muscle whose action opposes that of a particular agonist. The triceps brachii muscle is an agonist that extends the elbow. For this reason, it is an antagonist of the biceps brachii muscle. Likewise, the biceps brachii is an antagonist of the triceps brachii. Agonists and antagonists are functional opposites. If one produces flexion, the other produces extension. When an agonist contracts to produce a particular movement, the corresponding antagonist is stretched, but it usually does not relax completely. Instead, it contracts eccentrically, with just enough tension to control the speed of the movement and ensure its smoothness. When a synergist contracts, it helps a larger agonist work efficiently. Synergists may provide additional pull near the insertion or may stabilize the point of origin. A fixator is a synergist that assists an agonist by preventing movement at another joint, thereby stabilizing the origin of the agonist. H. How Muscles Are Named The name of a muscle may include descriptive information about its location in the body, origin and insertion, fascicle organization, position, structural characteristics, and action. 1. Location in the Body Regional terms are most common as modifiers that help identify individual muscles. In a few cases, a muscle is such a prominent feature of a body region 85 that a name referring to the region alone will identify it. Examples include the temporalis muscle of the head and the brachialis muscle of the arm. 2. Origin and Insertion Many muscle names include terms for body places that tell you the specific origin and insertion of each muscle. In such cases, the first part of the name indicates the origin, the second part the insertion. The genioglossus muscle, for example, originates at the chin (geneion) and inserts in the tongue (glossus). 3. Fascicle Organization A muscle name may refer to the orientation of the muscle fascicles within a particular skeletal muscle. Rectus means “straight,” and rectus muscles are parallel muscles whose fibers run along the long axis of the body. For example, the rectus abdominis muscle is located on the abdomen, and the rectus femoris muscle on the thigh. 4. Position Muscles visible at the body surface are often called externus or superficialis. Deeper muscles are termed internus or profundus. Superficial muscles that position or stabilize an organ are called extrinsic. Muscles located entirely within an organ are intrinsic. 5. Structural Characteristics Some muscles are named after distinctive structural features. The biceps brachii muscle, for example, is named after its origin. It has two tendons of origin. Similarly, the triceps brachii muscle has three, and the quadriceps group has four. Shape is sometimes an important clue to the name of a muscle. For example, the trapezius, deltoid, rhomboid, and orbicularis) muscles look like a trapezoid, a triangle, a rhomboid, and a circle, respectively. 6. Action Many muscles are named flexor, extensor, pronator, abductor, and so on. These are such common actions that the names almost always include other clues as to the appearance or location of the muscle. For example, the extensor carpi radialis longus muscle is a long muscle along the radial (lateral) border of the forearm. When it contracts, its primary function is extension at the carpus (wrist). 86 Figure 53: Muscle Terminology I. Axial and Appendicular Muscles The separation of the skeletal system into axial and appendicular divisions serves as a useful guideline for subdividing the muscular system as well: The axial muscles arise on the axial skeleton. This category includes approximately 60 percent of the skeletal muscles in the body. They position the head and spinal column and also move the rib cage, assisting in the movements that make breathing possible. They do not play a role in movement or support of either the pectoral or pelvic girdle or the limbs. The appendicular muscles stabilize or move components of the appendicular skeleton. These muscles include the remaining 40 percent of all skeletal muscles. 87 Figure 54: Anterior View of Major Skeletal Muscles 88 Figure 55: Posterior View of Major Skeletal Muscles 89 1. Axial muscles are muscles of the head and neck, vertebral column, trunk, and pelvic floor a. Muscle of Facial Expression Figure 56: Muscles of Facial Expression 90 b. Muscles of the Vertebral Column Figure 57: Muscles of the Vertebral Column c. Muscles of the Extrinsic Eyes, Mastication, Tongue, Pharynx, Anterior Neck, Diaphragm and Pelvic Floor (See media support at the end of this chapter) 91 2. Appendicular Muscles are muscles of the shoulders, upper limbs, pelvis, and lower limbs a. Appendicular Muscles of the Trunk Figure 58: Anterior Overview of the Appendicular Muscles of the Trunk 92 Figure 59: Posterior Overview of the Appendicular Muscles of the Trunk b. Muscles that move the arm The muscles that move the arm are easiest to remember when they are grouped by their actions at the shoulder joint. The deltoid muscle is the major abductor, but the supraspinatus muscle assists at the start of this movement. The subscapularis and teres major muscles produce medial rotation at the shoulder, whereas the infraspinatus and the teres minor muscles produce lateral rotation. All these muscles originate on the scapula. 93 94 Figure 60: Muscles that Move the Arm c. Muscles that move the hand and fingers 95 Figure 61: Muscles that Move Hands and Fingers d. Muscles that move the leg 96 Figure 62: Muscles that Move the Leg e. Muscles that position pectoral girdle (See media support at the end of this chapter) f. Muscles that move the thigh, foot and toes (See media support at the end of this chapter) J. Effects of Aging on the Muscular System 1. Skeletal Muscle Fibers Become Smaller in Diameter. 2. Skeletal Muscles Become Less Elastic. Aging skeletal muscles develop increasing amounts of fibrous connective tissue, a process called fibrosis. Fibrosis makes the muscle less flexible, and the collagen fibers can restrict movement and circulation. 3. Tolerance for Exercise Decreases. A lower tolerance for exercise comes in part from tiring quickly and in part from reduced Thermoregulation, Individuals over age 65 cannot eliminate the heat their muscles generate during contraction as effectively as younger people can. For this reason, they are subject to overheating. 4. The Ability to Recover from Muscular Injuries Decreases. The number of satellite cells steadily decreases with age, and the amount of fibrous tissue increases. As 97 a result, when an injury occurs, repair capabilities are limited. Scar tissue formation is the usual result. Regular exercise helps control body weight, strengthens bones, and generally improves the quality of life at all ages. Extremely demanding exercise is not as important as regular exercise. In fact, extreme exercise in the elderly can damage tendons, bones, and joints. K. Exercises Produces Response in Multiple Body Systems To operate at maximum efficiency, the muscular system must be supported by many other systems. The changes that take place during exercise provide a good example of such interaction. As noted earlier, active muscles consume oxygen and generate carbon dioxide and heat. The immediate effects of exercise on various body systems include the following: Cardiovascular System: Blood vessels in active muscles and the skin dilate, and heart rate increases. These adjustments speed up oxygen and nutrient delivery to and carbon dioxide removal from the muscle. They also bring heat to the skin for radiation into the environment. Respiratory System: Respiratory rate and depth of respiration increase. Air moves into and out of the lungs more quickly, keeping pace with the increased rate of blood flow through the lungs. Integumentary System: Blood vessels dilate and sweat gland secretion increases. This combination increases evaporation at the skin surface and removes the excess heat generated by muscular activity. Nervous and Endocrine Systems: The responses of other systems are directed and coordinated through neural and endocrine (hormonal) adjustments in heart rate, respiratory rate, sweat gland activity, and mobilization of stored nutrient reserves. Even when the body is at rest, the muscular system has extensive interactions with other systems. 98 Link to Video Recording: Topic Website/s https://courses.lumenlearning.com/suny-ap1/ https://www.youtube.com/watch?v=rMcg9YzNSEs Muscular System https://www.youtube.com/watch?v=Qb9E3jH_PXQ https://www.innerbody.com/image/musfov.html https://www.khanacademy.org/science/high- school-biology/hs-human-body-systems/hs-the- musculoskeletal-system/v/anatomy-of-a-muscle- cell-1 Axial Muscles https://www.youtube.com/watch?v=jFTPG9LQ7Ps https://www.youtube.com/watch?v=V7NybM7QeXY https://www.youtube.com/watch?v=0eoqijtV2AI Appendicular Muscles https://www.youtube.com/watch?v=LK51apYOdtc https://www.youtube.com/watch?v=usBihmnYsCw https://www.youtube.com/watch?v=qmtVccTL98k https://www.youtube.com/watch?v=0qksc4kqSjM https://www.youtube.com/watch?v=-o7MZyXL2eY Diseases and Injuries of the Muscular System https://www.youtube.com/watch?v=rPxo2q1IJSM https://www.youtube.com/watch?v=EkdllXH5AME https://www.youtube.com/watch?v=MPqjFEhEBB4 99 Activity 5 Name: ______________________________ Score: ________________ Course, Year and Section: _____________ Equivalent: ____________ A. Supply the missing information. Write your answer on the space provided. Muscle Origin Insertion Action 1.______________________ Medial surface of tibia near Flexion at Knee; flexion and Sartorius tibial tuberosity lateral rotation at hip By extensor tendon to lateral Posterior surface of proximal Extensor Digiti Minimi epicondyle of humerus and phalanx of little finger (5) 2._______________________ from intermuscular septa Coracobrachialis Coracoid process 3. _____________________ Adduction and flexion at shoul Supraspinatus Supraspinous fossa of Greater tubercle of humerus 4. ______________________ scapula Spinous processes of inferior Spinalis Thocacis thoracic and superior lumbar 5. _____________________ Extends vertebral column vertebrae Zygomaticus Major 6. _____________________ Angle of mouth Retracts and elevates corner of mouth Passes medially to reach the Extension, adduction, and Teres Major 7. _____________________ medial lip of intertubercular medial rotation at shoulder groove of humerus Inferior portion of ligamentum Spinous process of axis Spinalis Cervicis nuchae and spinous process 8. ______________________ of C7 Mentalis Incisive fossa of mandible 9. _____________________ Elevates and protrudes lower

Lesson 2: Chemical, Cellular, and Tissue Level of Organization (BIOL 30143)

Document Details

Tags

Related

Summary

Full Transcript

Upgrade to continue