Integumentary, Skeletal, & Muscular Systems | Body Systems Project
Function of the. Skeletal system. 1. Support the body. 2. Protect internal organs. 3 . Provides for movement. 4. Stores mineral reserves. 5. Blood cell formation. The Skeletal System and Interrelationships with the Muscular, Endocrine, systems, not the least of which are the endocrine and integumentary systems. However, its most intimate and mutually beneficial relationship is with the muscular system, (among its other roles) it regulates the carrier system that absorbs calcium. Relation to Muscular System. Skeletal muscles move bones; Tendons connect muscle to bone. Relation to Skeletal System. The integumentary system includes the skin, hair, and nails; It is throughout the entire body; The.
This section provides an introduction to the musculoskeletal and skin systems, including their involvement both in maintenance of good health and their dysfunction in disease. As such, it uses language and concepts not appropriate for middle school students.
Our intention is to give you enough background that you will be able to assess your students' understanding of the topic and be equipped to answer their most common questions. The musculoskeletal and skin systems and their functions are topics that are extremely well suited for middle school students.
As stated in the National Science Education Standards NSEStopics related to human biology are especially relevant to middle school students because students at this point in cognitive development begin to understand the relationship between structure and function. Students can integrate structure-function relationships in the context of human body systems working together.
Figure 1 Looking Good, Feeling Good: In this module, students learn that their bones, muscles, and skin fulfill many roles that enable a person to complete complex voluntary tasks as well as involuntary actions that are essential to health.
The information about the musculoskeletal and skin systems will also help students achieve the content standards related to Life Science, particularly concepts related to the structure and function of living systems.
In addition, this module addresses standards related to Science in Personal and Social Perspectives personal health. The concepts conveyed will also address several of the National Health Education Standards. Misconceptions about the Musculoskeletal and Skin Systems Adolescents, like many adults, have perceptions about their musculoskeletal and skin systems that are likely to be incorrect or incomplete.
Almost every day, people are exposed to material on television or radio or in the newspapers about a new medicine, exercise, treatment, product, or diet that can influence their health. For example, advertisements promote "nutritional supplements" that will build muscle without exercise or dieting.
Adolescents hear, see, or read about many over-the-counter treatments for acne—a condition about which they are especially aware because of their age. Many teenagers will try these products in search of help. Teenagers also receive inaccurate information about acne from peers or family members who believe that acne is caused by eating chocolate or other sweets.
In addition, pharmaceutical companies often advertise prescription medications that are used to prevent disease. Although these medications can be valuable when used correctly, the advertisements do not give a complete picture. Generally, science textbooks for middle school students present limited scientific information on the musculoskeletal and skin systems. As part of the presentation on the major body systems, science textbooks include a diagram of each of these systems with the parts labeled and some cursory information about their functions.
Too often, however, this information becomes a vocabulary exercise without conveying any real understanding of how these systems work or regulate a vast array of physiological processes. Some misconceptions about the musculoskeletal and skin systems are the following: Muscles are only used for voluntary physical actions like walking, running, or throwing. Skeletal muscles are probably most familiar to middle school students even though other types of muscles, cardiac and smooth, are essential for life functions.
The heart muscle is composed of a different type of muscle cell cardiac muscle cells and beats to move blood throughout the body. Smooth muscle cells line blood vessels and the intestinal tract to help move blood or food through those passages.
The tongue is made up of muscle cells that enable us to speak and is also an important part of the digestive system. Your muscles turn to fat if you quit exercising. Misconception 2 is common not only among adolescents but also among adults and reflects a basic misunderstanding of how the body works.
If a person stops exercising, his or her muscle cells may decrease in volume and become smaller. At the same time, a person may increase the volume of fat cells in his or her body. This concurrent change may give the impression that muscle is becoming fat, but this is not the case.
Fat cells are different from muscle cells; muscle cells do not turn into fat. Bones are not living structures. Adolescents may have conflicting ideas about whether bones are living structures, depending upon the context of the situation they are considering. On the one hand, they may believe that bones are just hard things that hold the body up and have muscles attached to them.
On the other hand, teenagers recognize that broken bones heal. Few students have an understanding of how their bones grow during development or recognize that the bone marrow is critical for production of both red and white blood cells.
Even maintenance of bone structure is a dynamic process; the action of specialized cells called osteoblasts to form new bone is counterbalanced by other cells, osteoclasts, which break down bone through resorption.
As people age, bone resorption predominates over bone formation. Diseases like osteoporosis or arthritis affect only old people, so teenagers do not need to be concerned about them. Although osteoporosis, a disease in which bone density decreases, affects older individuals, scientists now realize that it is important for young people to take care of their bones because this can influence the onset of osteoporosis in later life. Acne is caused by eating chocolate or greasy foods.
The exact cause of acne is not known. This incomplete understanding has allowed many myths about the causes of acne to become widespread. There is little evidence that diet causes or affects the course of acne.
Rather, acne is caused by a number of interacting factors. One important factor is the increase in male hormones androgens that accompanies puberty in both boys and girls. Nearly 85 percent of adolescents and young adults develop acne. Since acne seems to run in families, it is thought to have a genetic component as well. Although the causes of acne are unclear, several factors have been shown to exacerbate the disorder.
These include changing hormone levels in females as before their menstrual periodsfriction caused by rubbing the skin, irritants such as pollution, squeezing of the lesions, and vigorous scrubbing of the skin. Body piercings and tattoos are completely safe. Body modifications involve breaking the skin, and consequently, carry a risk of infection. People with tattoos are nine times more likely to be infected with the hepatitis C virus than are people without tattoos.
There are health risks associated with body piercings and tattoos. Anyone considering undergoing these procedures should first research them, be aware of the health risks, find a provider who performs the procedure correctly, and use proper follow-up care.
Characteristics of Living and Nonliving Systems It should be simple to distinguish between living and nonliving systems. After all, even children know that a rock is nonliving and a spider is a living creature. However, defining life is not a trivial task. Life has been defined in many ways for many different purposes, and there is no single definition that works for everyone. The Characteristics of Living Systems table lists some characteristics that are commonly found in definitions of living systems.
Characteristics of Living Systems Composed of one or more cells Function according to a genetic blueprint Obtain and generate energy that is, have a metabolism Interact with their environment These characteristics were derived with the following in mind: Some objects that are clearly nonliving are derived from once-living systems, however.
A lump of coal is largely made up of material from plants that lived millions of years ago.
The ability to reproduce is often identified as a characteristic of living systems. This characteristic is not listed separately because bone, muscle, and skin are living systems, but they do not reproduce themselves. The cells of bone reproduce and carry out activities such as making protein and depositing mineral that allow bone to grow, repair, and remodel itself.
Bone cells do not reproduce and make new bones. In the Characteristics of Living Systems table, reproduction falls under the characteristic "function according to a genetic blueprint. As with the amoeba, we can classify a human as living. Indeed, close examination of the human body reveals that it is composed of living cells, cells that were once living, and nonliving substances produced by living cells.
These distinctions become important as we investigate the structures and functions of bone, muscle, and skin.
Characteristics of Bone, Muscle, and Skin Human development is a complex process that begins with a fertilized egg cell and eventually gives rise to an adult human composed of over trillion cells. Cells with the same function may group together in specific ways to form a colony of cells called a tissue. An adult human makes use of over different tissues.
As the number of cells in the developing human increases, the fate of the individual cells becomes evermore restricted. This process by which a cell becomes committed to a specific function is called differentiation. Just as the human body has different organs that carry out specific functions, the human cell has different organelles that have specialized functions. All human cells share certain characteristics. They possess a plasma membrane that separates their inside contents from the outside environment, enclose their genetic material inside a membrane-bound organelle called a nucleus, generate usable energy within organelles called mitochondria, and synthesize proteins using ribosomes.
Despite these similarities, differentiation produces cells that differ in significant ways from one another. The shapes of different cells relate to their functions within the body. For example, nerve cells have many long branches that enable them to communicate with each other and with other cells. Even the presence or absence of a critical organelle, such as the nucleus, can vary by cell type.
A mature red blood cell has no nucleus, while a mature skeletal muscle cell has many nuclei derived from cells that have fused together.
We shall learn in the following sections how the cells of the musculoskeletal and skin systems have characteristic shapes that relate to their functions and how they combine to form specialized tissues. Bone Bones serve many important functions. They allow us to do things we take for granted, such as stand and sit, walk and run.
They do this in concert with muscles, which attach to bones via tendons. Our bones provide structural support for the body and help determine our shape. Bones also protect internal organs the skull protects the brain, and the ribs protect the heart and lungsand the bone marrow produces red blood cells and the white blood cells of the immune system.
Bones are lightweight yet very strong, static in appearance yet very dynamic. How does the structure of bones determine how they function in the body? Our skeletal system serves as a storage depot for calcium and other physiologically important ions. Bones have a unique structure The human skeleton has bones of different sizes and shapes. Bones such as those in the arms and legs are called long bones. Others, such as those in the skull, are called flat bones. Other categories include the short bones for instance, the carpel bones of wrist and the irregular bones for instance, vertebrae.
In general, adult human bones are composed of about 70 percent minerals and 30 percent organic matter. The remainder of the organic matter consists of a gelatinous medium called ground substance, which contains extracellular fluid and specialized proteins called proteoglycans. How these organic and inorganic materials are put together to form the strong unit we call bone is discussed in section 4.
Looking at a cross section of a long bone, one sees an inner cavity surrounded by an outer fibrous matrix. The inner cavity contains bone marrow, which consists of fatty tissue and cells that give rise to the red and white blood cells that circulate in the body. The bone matrix contains hydroxyapatite and calcium salts deposited in a network of collagen fibers.
On the outside of the bone is a fibrous layer called the periosteum Figure 3. Figure 3 Cross section of a bone. A closer look reveals more details. There are two forms of bone—compact hard bone, the solid, hard outside part of bone that is optimized to handle compressive and bending forces, and spongy cancellous bone, which is found inside the compact bone and near the ends of the bone.
Blood vessels are also present and allow nutrients to be brought to bone cells and waste products to be carried away. Blood vessels and nerves pass through narrow openings, or canals, that run parallel to the surface and along the long axis of the bone. Bone contains three specialized cell types The name of each begins with osteo, since this is the Greek word for bone.
Osteoblasts are cells that form new bone. They are found on the surface of new bone and they have a single nucleus Figure 4. They are derived from stem cells in the bone marrow. Osteoblasts produce collagen found in bone and the proteoglycans found in ground substance. They are rich in alkaline phosphatase, a phosphate-splitting enzyme required for bone mineralization, a process that osteoblasts control.
When osteoblasts have completed making new bone, the cells take on a flattened appearance and line the surface of the bone. Now in a more mature, less active state, the cells are called bone-lining cells. They still serve important functions, however. For instance, bone-lining cells respond to specific hormones and produce proteins that activate another type of bone cell called the osteoclast. Figure 4 An osteoclast, osteoblasts, and osteocytes across the bottom.
Osteoclasts are large, multinucleated cells that are capable of movement.The Skeletal System: Crash Course A&P #19
They are formed by the fusion of mononuclear cells derived from stem cells in the bone marrow. Unlike osteoblasts, osteoclasts lie in depressions where their function is to dissolve resorb bone and help shape it Figure 4. They begin by attacking the mineral portion of bone and then they degrade the bone proteins. Osteocytes are cells that reside inside bone. They are derived from osteoblasts as new bone is being formed and then become surrounded by the new bone.
However, rather than being isolated, osteocytes communicate through long branches that connect these cells to one another. These cells regulate the response of bone to its mechanical environment. Bone formation involves an organic matrix To understand how bone is formed and why its properties confer such strength, imagine that you have steel rods and cement that you will use to construct a wall or a bridge. Pouring cement around steel rods placed in a suitable frame produces a material reinforced concrete that is stronger and more capable of withstanding movement than either steel rods or cement alone.
Bone has a similar organization. The steel rods are chains of collagen, which confer resiliency, and the cement is hydroxyapatite, which confers strength. Bone formation begins with synthesis of the organic matrix by osteoblasts.
The matrix can be likened to a protein scaffolding. Next, through a mechanism not yet understood, osteoblasts deposit mineral crystals in the spaces between the protein scaffolding. The mineral consists primarily of calcium and phosphorus. Finally, osteoclasts work with osteocytes to shape or remodel the bone by breaking down the proteins and resorbing the minerals.
Bone formation is not a strictly linear process, however. Bones are constantly being formed, broken down, and re-formed. Bone is a very dynamic, continually changing tissue. Osteoblasts, osteoclasts, and osteocytes function to maintain a balance between bone deposition and bone resorption that allows bones to grow, repair themselves, and remain strong. The activity of osteoblasts and osteoclasts is influenced by a number of factors.
Vitamin D helps the intestine absorb calcium from foods into the bloodstream after digestion. It is also important in regulating phosphate in the body see also section 5. Parathyroid hormone activates the osteoclasts, thereby increasing the rate of bone breakdown. Other factors that regulate the dynamic balance between bone deposition and bone breakdown include growth factors and hormones. Importantly, exercise is an important factor in normal bone growth and development.
Also, the composition of bone mineral is not fixed.
Other ions, if present, can be incorporated into new or remodeled bone. Fluoride, for example, can be incorporated into bone mineral to form fluorapatite, which is harder, less soluble, and more resistant to resorption than is hydroxyapatite.
Bones grow as we grow This is no surprise. In fact, more bone is formed during the first 20 to 30 years of life than is resorbed, resulting in an increase in bone mass. However, contrary to what some might think, long bones do not grow or elongate from the middle, a region called the diaphysis. Rather, the bones grow from their ends, regions called the epiphyses singular is epiphysis.
Cartilage is a connective tissue specialized to handle mechanical stress without becoming distorted permanently. It is found in areas where shock-absorbing properties are needed or where smooth movement between bones that is, at a joint is required.
As bones grow, additional cartilage is deposited at the epiphyseal, or growth, plate. This cartilage is the framework on which bone matrix is deposited. Bone growth continues as long as the growth plates are able to produce chondrocytes cartilage-producing cells.
The growth plate determines the length and shape of the mature bone and is the weakest part of the growing skeleton. The growth plate can be injured fractured during an acute incident, such as a fall, or from overuse, such as during intense sports training.
At the end of puberty, high levels of estrogen or testosterone cause the chondrocytes to die, and they are replaced by bone. It is during late adolescence that humans achieve their peak bone mass. Adequate calcium intake during teen years, when bone formation is very active, is an important factor in preventing excessive bone resorption later in life. Muscle Muscle is the most abundant tissue in most animals. In vertebrates, such as humans, there are different types of muscle, and each has a unique cellular structure and function.
Skeletal muscle enables us to walk, run, lift, or do other physical movements. It enables people to maintain their body posture. Skeletal muscle is also referred to as striated muscle because the arrangement of muscle fibers has a striped striated appearance when viewed under a microscope.
Smooth muscle is found in the walls of the stomach and intestines, the urinary bladder, the bronchi of the lungs, and the arterial blood vessels. It functions to propel substances along their tracts within the body. Smooth muscle lacks striations and is composed of cells that are spindle shaped.
A third type of muscle, cardiac muscle, makes up the heart and pumps blood throughout the body. As the name implies, skeletal muscle is intimately associated with the skeletal system, and for this reason, this module focuses on skeletal muscle and does not discuss cardiac and smooth muscle.
Unless otherwise noted, the term muscle refers to skeletal muscle from this point on. During human development, the differentiation of the muscle system is essentially complete just 8 weeks after fertilization.
The first cells committed to form muscle in the developing embryo are called myoblasts. Some myoblasts divide rapidly, while others migrate to areas where muscle tissue needs to form, such as the developing limb buds. Once myoblasts arrive at their needed location, they stop cell division and begin to fuse together with adjoining myoblasts. The results of this cell fusion create a larger cell with many nuclei that share the same cytoplasm.
These multinucleated cells continue to differentiate into a myotube, which is the basic structural cell of muscle tissue. The most essential feature of muscle cells is their ability to generate force by contracting, or shortening—a function unlike that of other types of cells.
In skeletal muscle, numerous myotubes bundle together to form a muscle. Within each myotube are thin and thick filaments. Under the microscope, the regular arrangement of these filaments accounts for the alternating light and dark bands seen in the tissue.
The functional unit of the muscle is called the sarcomere. Each sarcomere has a dark Z line at each end. By examining the structure of the sarcomere, we can begin to appreciate how a muscle cell is able to contract and exert force on the skeletal system. When researchers observed muscle contraction under the microscope, they noticed that the sarcomere shortened, that is, the Z lines moved closer together.
This observation suggested that muscle contraction proceeds by having thin and thick filaments slide past each other, shortening the sarcomere. This process is described by the sliding-filament model of muscle contraction Figure 5. According to this model, the lengths of the thin and thick filaments do not change.
Rather, the extent to which they overlap changes. As the amount of overlap between the thin and thick filaments increases, the length of the sarcomere decreases.
Thin filaments are made of a protein called actin, and thick filaments are made of a protein called myosin. The myosin molecule has a long "tail" region with a protruding "head" at one end. The myosin head provides the energy needed to move the filaments past each other by breaking down the high-energy molecule ATP into ADP and inorganic phosphate. Figure 5 The sliding-filament model of muscle contraction. Muscle contraction is controlled by the nervous system.
Nerves that interact with a muscle cell release a neurotransmitter, known as acetylcholine. This triggers electrical changes within the muscle cell that lead to the release of calcium ions from the sarcoplasmic reticulum a specialized form of the endoplasmic reticulum. The calcium ions release an inhibitory mechanism and allow the actin and myosin filaments to slide past each other.
The muscle fibers themselves are not all identical. They can be classified as slow-twitch fibers or fast-twitch fibers. At Thanksgiving dinner, we refer to these different types of turkey muscle as dark meat and light meat.
The dark meat is composed of muscle that has a large proportion of slow-twitch fibers. The slow-twitch fibers are made of muscle cells that have more mitochondria and therefore more red-colored cytochromes than cells from fast-twitch fibers.
Slow-twitch fibers have less sarcoplasmic reticulum as compared with fast-twitch fibers. Slow-twitch fibers contract at a rate about five times longer than fast-twitch fibers. Fast-twitch fibers are specialized for generating rapid, forceful contractions for short-term activities such as jumping or sprinting over a period of a few seconds to about a minute. Some of our muscles, such as those controlling eye movements, are made almost exclusively from fast-twitch fibers.
Slow-twitch fibers are specialized for prolonged activity over a period of minutes or hours. The soleus muscle in the lower leg is made up of slow-twitch fibers. Most of our muscles are composed of a mixture of slow-twitch and fast-twitch fibers, and this mix varies among individuals. The ratio of slow-twitch to fast-twitch fibers for a given muscle is largely genetically determined, though some studies have shown that rigorous training can alter the ratio.
This means that in order to move a limb either up and down or back and forth, a pair of muscles must be involved. Indeed, skeletal muscles work in antagonistic pairs. For example, when a person bends his or her arm, the biceps contract shorten and the triceps relax lengthen.
When the arm straightens, the biceps relax and the triceps contract. Contraction is called the concentric phase, whereas the relaxation of the muscle is the eccentric phase. In general, most people think of muscles generating force only as they contract and get shorter.
The nervous system regulates the speed at which food moves through the digestive tract. Endocrine System The endocrine system secretes hormones into blood and other body fluids. These chemicals are important for metabolism, growth, water and mineral balance, and the response to stress. Pineal body, pituitary gland, hypothalamus, thyroid, parathyroid, heart, adrenal gland, kidney, pancreas, stomach, intestines, ovary Hormones provide feedback to the brain to affect neural processing. Reproductive hormones affect the development of the nervous system.
The hypothalamus controls the pituitary gland and other endocrine glands. Lymphatic System The lymphatic system protects the body from infection. Adenoid, tonsils, thymus, lymph nodes, spleen The brain can stimulate defense mechanisms against infection. Respiratory System The respiratory system supplies oxygen to the blood and removes carbon dioxide. Lungs, larynx, pharynx, trachea, bronchi The brain monitors respiratory volume and blood gas levels.
The brain regulates respiratory rate. Digestive System The digestive system stores and digests foods, transfers nutrients to the body, eliminates waste and absorbs water.
Stomach, esophagus, salivary glands, liver, gallbladder, pancreas, intestines Digestive processes provide the building blocks for some neurotransmitters. The autonomic nervous system controls the tone of the digestive tract. The brain controls drinking and feeding behavior.
The brain controls muscles for eating and elimination. The digestive system sends sensory information to the brain. Reproductive System The reproductive system is responsible for producing new life. Testes, vas deferens, prostate gland, ovary, fallopian tubes, uterus, cervix Reproductive hormones affect brain development and sexual behavior. The brain controls mating behavior.