BODY FUNCTIONS & LIFE PROCESS
Body Functions
Body functions are the physiological or psychological functions of body systems. The body's functions are ultimately its cells' functions. Survival is the body's most important business. Survival depends on the body's maintaining or restoring homeostasis, a state of relative constancy, of its internal environment.
Homeostasis depends on the body's ceaselessly carrying on many activities. Its major activities or functions are responding to changes in the body's environment, exchanging materials between the environment and cells, metabolizing foods, and integrating all of the body's diverse activities.
Life Process
All living organisms have certain characteristics that distinguish them from non-living forms. The basic processes of life include organization, metabolism, responsiveness, movements, and reproduction. In humans, who represent the most complex form of life, there are additional requirements such as growth, differentiation, respiration, digestion, and excretion. All of these processes are interrelated. No part of the body, from the smallest cell to a complete body system, works in isolation. All function together, in fine-tuned balance, for the well being of the individual and to maintain life.
Yoga means union
The goal of life is harmony. For all living organisms to have to function together as one, each individual functioning for the well being of all. Nothing is separate, everything is connected.
Body functions are the physiological or psychological functions of body systems. The body's functions are ultimately its cells' functions. Survival is the body's most important business. Survival depends on the body's maintaining or restoring homeostasis, a state of relative constancy, of its internal environment.
Homeostasis depends on the body's ceaselessly carrying on many activities. Its major activities or functions are responding to changes in the body's environment, exchanging materials between the environment and cells, metabolizing foods, and integrating all of the body's diverse activities.
Life Process
All living organisms have certain characteristics that distinguish them from non-living forms. The basic processes of life include organization, metabolism, responsiveness, movements, and reproduction. In humans, who represent the most complex form of life, there are additional requirements such as growth, differentiation, respiration, digestion, and excretion. All of these processes are interrelated. No part of the body, from the smallest cell to a complete body system, works in isolation. All function together, in fine-tuned balance, for the well being of the individual and to maintain life.
Yoga means union
The goal of life is harmony. For all living organisms to have to function together as one, each individual functioning for the well being of all. Nothing is separate, everything is connected.
Planes of the Body
Coronal Plane (Frontal Plane) - A vertical plane running from side to side; divides the body or any of its parts into anterior and posterior portions.
Sagittal Plane (Lateral Plane) - A vertical plane running from front to back; divides the body or any of its parts into right and left sides.
Axial Plane (Transverse Plane) - A horizontal plane; divides the body or any of its parts into upper and lower parts.
Median plane - Sagittal plane through the midline of the body; divides the body or any of its parts into right and left halves.
Sagittal Plane (Lateral Plane) - A vertical plane running from front to back; divides the body or any of its parts into right and left sides.
Axial Plane (Transverse Plane) - A horizontal plane; divides the body or any of its parts into upper and lower parts.
Median plane - Sagittal plane through the midline of the body; divides the body or any of its parts into right and left halves.
Directional Terms
Directional terms describe the positions of structures relative to other structures or locations in the body.
Supine - face up
Prone - face down
Superior or cranial - toward the head end of the body; upper (example, the hand is part of the superior extremity).
Inferior or caudal - away from the head; lower (example, the foot is part of the inferior extremity).
Anterior or ventral - front (example, the kneecap is located on the anterior side of the leg).
Posterior or dorsal - back (example, the shoulder blades are located on the posterior side of the body).
Medial - toward the midline of the body (example, the middle toe is located at the medial side of the foot).
Lateral - away from the midline of the body (example, the little toe is located at the lateral side of the foot).
Proximal - toward or nearest the trunk or the point of origin of a part (example, the proximal end of the femur joins with the pelvic bone).
Distal - away from or farthest from the trunk or the point or origin of a part (example, the hand is located at the distal end of the forearm).
Prone - face down
Superior or cranial - toward the head end of the body; upper (example, the hand is part of the superior extremity).
Inferior or caudal - away from the head; lower (example, the foot is part of the inferior extremity).
Anterior or ventral - front (example, the kneecap is located on the anterior side of the leg).
Posterior or dorsal - back (example, the shoulder blades are located on the posterior side of the body).
Medial - toward the midline of the body (example, the middle toe is located at the medial side of the foot).
Lateral - away from the midline of the body (example, the little toe is located at the lateral side of the foot).
Proximal - toward or nearest the trunk or the point of origin of a part (example, the proximal end of the femur joins with the pelvic bone).
Distal - away from or farthest from the trunk or the point or origin of a part (example, the hand is located at the distal end of the forearm).
Body Cavaties
The cavities, or spaces, of the body contain the internal organs, or viscera. The two main cavities are called the ventral and dorsal cavities. The ventral is the larger cavity and is subdivided into two parts (thoracic and abdominopelvic cavities) by the diaphragm, a dome-shaped respiratory muscle.
THE SKELETAL SYSTEM
Humans are vertebrates, animals having a vertabral column or backbone. They rely on a sturdy internal frame that is centered on a prominent spine. The human skeletal system consists of bones, cartilage, ligaments and tendons and accounts for about 20 percent of the body weight.
The living bones in our bodies use oxygen and give off waste products in metabolism. They contain active tissues that consume nutrients, require a blood supply and change shape or remodel in response to variations in mechanical stress.
Bones provide a rigid framework, known as the skeleton, that support the body against the pull of gravity. The large bones of the lower limbs support the trunk when standing.
The skeleton also protects the soft body parts. The fused bones of the cranium surround the brain to make it less vulnerable to injury. Vertebrae surround and protect the spinal cord and bones of the rib cage help protect the heart and lungs of the thorax.
Bones work together with muscles as simple mechanical lever systems to produce body movement.
The living bones in our bodies use oxygen and give off waste products in metabolism. They contain active tissues that consume nutrients, require a blood supply and change shape or remodel in response to variations in mechanical stress.
Bones provide a rigid framework, known as the skeleton, that support the body against the pull of gravity. The large bones of the lower limbs support the trunk when standing.
The skeleton also protects the soft body parts. The fused bones of the cranium surround the brain to make it less vulnerable to injury. Vertebrae surround and protect the spinal cord and bones of the rib cage help protect the heart and lungs of the thorax.
Bones work together with muscles as simple mechanical lever systems to produce body movement.
Joints
Joints are places where bones come together and where limbs are attached. Joints allow the skeleton to move and provide stability.
There are 3 types of joints:
Fibrous joints join bones that don't have a cabvity between the bones, for example the skull. Cartilaginous joints are connected by cartilage and don't have a joint cavity such as the pubic bone. Synovial joints move freely.
The end of the bones are covered by the synovial membrane which secretes synovial fluid to keep the bones lubricated, it is produced on demand by movement. If a joint does not move, it will lock up like a rusty door hinge. Muscles can shorten, pulling bones tight. If ligaments and joint capsules are not pliable, flexibility is lost. Synovial fluid also contains cells that rid the joint cavity of cellular debris and bacteria.
Three types of barriers exist to prevent movement in the joints:
Anatomic barriers are structural.
Phsysiologic barriers are where the nerves and senses feel where the end of the range of motion is to keep the joint at its optimum function.
Pathologic barrier is when the nerves and senses limit joint function and stiffness and pain manifest.
In yoga the idea is to safely take the joints to their threshold, to the end-feel where it is possible to feel that a little more movement is possible, then after a few breaths to move into that space.
That is why it is important not to take the stretch too far, there may be a barrier that the body is not yet ready to let go of and if force is tried then injury may result.
Joint movement also contributes to the lymphatic and venous circulation and tendons, ligaments and joint capsules are warmed. Mechanical movement of joints keeps tissues pliable.
There are 3 types of joints:
Fibrous joints join bones that don't have a cabvity between the bones, for example the skull. Cartilaginous joints are connected by cartilage and don't have a joint cavity such as the pubic bone. Synovial joints move freely.
The end of the bones are covered by the synovial membrane which secretes synovial fluid to keep the bones lubricated, it is produced on demand by movement. If a joint does not move, it will lock up like a rusty door hinge. Muscles can shorten, pulling bones tight. If ligaments and joint capsules are not pliable, flexibility is lost. Synovial fluid also contains cells that rid the joint cavity of cellular debris and bacteria.
Three types of barriers exist to prevent movement in the joints:
Anatomic barriers are structural.
Phsysiologic barriers are where the nerves and senses feel where the end of the range of motion is to keep the joint at its optimum function.
Pathologic barrier is when the nerves and senses limit joint function and stiffness and pain manifest.
In yoga the idea is to safely take the joints to their threshold, to the end-feel where it is possible to feel that a little more movement is possible, then after a few breaths to move into that space.
That is why it is important not to take the stretch too far, there may be a barrier that the body is not yet ready to let go of and if force is tried then injury may result.
Joint movement also contributes to the lymphatic and venous circulation and tendons, ligaments and joint capsules are warmed. Mechanical movement of joints keeps tissues pliable.
https://youtu.be/0cYal_hitz4 copy and paste this link for a YouTube video explaining the joints
Bursa is a closed sac-like structure found close to joint cavities, similar to the synovial lining. The bursa lubricates and area between skin, tendons, ligaments or other structures and bones where friction would otherwise develop. When you overuse or injure a joint, a nearby bursa can become irritated or inflamed. The bursa fills with excess fluid, causing significant pain and restricting movement. This is called bursitis, rest is a good cure.
Ligaments join bone to bone. Ligaments help to stabilise the joints.
Tendons join muscle to bone.
Cartilage is a firm tissue but is softer and much more flexible than bone. Cartilage is a connective tissue found in many areas of the body including: Joints between bones e.g. the elbows, knees and ankles; ends of the ribs; between the vertebrae in the spine; ears and nose; bronchial tubes or airways.
Ligaments, tendons and cartilage do not have a supply of blood so they take a long time to heal. Nutrients diffuse through the tissue.
Ligaments join bone to bone. Ligaments help to stabilise the joints.
Tendons join muscle to bone.
Cartilage is a firm tissue but is softer and much more flexible than bone. Cartilage is a connective tissue found in many areas of the body including: Joints between bones e.g. the elbows, knees and ankles; ends of the ribs; between the vertebrae in the spine; ears and nose; bronchial tubes or airways.
Ligaments, tendons and cartilage do not have a supply of blood so they take a long time to heal. Nutrients diffuse through the tissue.
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Types of movements made possible by Synovial Joints
Flexion - reduces the angle of a joint
Extension - increases the angle of a joint
Abduction - movement away from the midline
Adduction - movement towardsthe midline
Pronation - Turning the palm downwards
Supination - Turning the palm upwards
Eversion - turning the soul of the foot outwards
Inversion - turning the soul of the foot inwards
Plantar flexion - Movement of the plantar surface of the the sole of the foot downward (plant your toes into the ground)
Dorsiflextion _ Movement of the top or dorsal surface of the foot toward the shin ( pull your foot back)
Rotation - rolling to the side Internal rotation - towards the mid-line
External ration - away from the mid-line
Protraction - thrusting a part of the body forward
Retraction - pulling a part of the body backwards
Elevation - Raising a part of the body
Depression - Lowering a part of the body
Circumduction - Making a cone; the ability to move the limb in a circular motion
Opposition - Placing one part of the body opposite another, as in placing the tip of the thumb opposite the tips of the fingers
Extension - increases the angle of a joint
Abduction - movement away from the midline
Adduction - movement towardsthe midline
Pronation - Turning the palm downwards
Supination - Turning the palm upwards
Eversion - turning the soul of the foot outwards
Inversion - turning the soul of the foot inwards
Plantar flexion - Movement of the plantar surface of the the sole of the foot downward (plant your toes into the ground)
Dorsiflextion _ Movement of the top or dorsal surface of the foot toward the shin ( pull your foot back)
Rotation - rolling to the side Internal rotation - towards the mid-line
External ration - away from the mid-line
Protraction - thrusting a part of the body forward
Retraction - pulling a part of the body backwards
Elevation - Raising a part of the body
Depression - Lowering a part of the body
Circumduction - Making a cone; the ability to move the limb in a circular motion
Opposition - Placing one part of the body opposite another, as in placing the tip of the thumb opposite the tips of the fingers
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THE ENDOCRINE SYSTEM
The endocrine system, along with the nervous system, functions in the regulation of body activities.
The nervous system acts through electrical impulses and neurotransmitters to cause muscle contraction and glandular secretion. The effect is of short duration, measured in seconds, and localized.
The endocrine system acts through chemical messengers called hormones that influence growth, development, and metabolic activities. The action of the endocrine system is measured in minutes, hours, or weeks and is more generalized than the action of the nervous system.
There are two major categories of glands in the body - exocrine and endocrine.
Exocrine Glands
Exocrine glands have ducts that carry their secretory product to a surface. These glands include the sweat, sebaceous, and mammary glands and, the glands that secrete digestive enzymes.
Endocrine Glands
The endocrine glands do not have ducts to carry their product to a surface. They are called ductless glands. The word endocrine is derived from the Greek terms "endo," meaning within, and "krine," meaning to separate or secrete. The secretory products of endocrine glands are called hormones and are secreted directly into the blood and then carried throughout the body where they influence only those cells that have receptor sites for that hormone.
Mechanism of Hormones
Hormones are carried by the blood throughout the entire body, yet they affect only certain cells. The specific cells that respond to a given hormone have receptor sites for that hormone. This is sort of a lock-and-key mechanism. If the key fits the lock, then the door will open. If a hormone fits the receptor site, then there will be an effect. If a hormone and a receptor site do not match, then there is no reaction.
Hormones bring about their characteristic effects on target cells by modifying cellular activity.Hormones are very potent substances, which means that very small amounts of a hormone may have profound effects on metabolic processes. Because of their potency, hormone secretion must be regulated within very narrow limits in order to maintain homeostasis in the body.
The endocrine system is made up of the endocrine glands that secrete hormones. Although there are eight major endocrine glands scattered throughout the body, they are still considered to be one system because they have similar functions, similar mechanisms of influence, and many important interrelationships.
Notice also the similarity of the placement of the glands with the chakras.
The nervous system acts through electrical impulses and neurotransmitters to cause muscle contraction and glandular secretion. The effect is of short duration, measured in seconds, and localized.
The endocrine system acts through chemical messengers called hormones that influence growth, development, and metabolic activities. The action of the endocrine system is measured in minutes, hours, or weeks and is more generalized than the action of the nervous system.
There are two major categories of glands in the body - exocrine and endocrine.
Exocrine Glands
Exocrine glands have ducts that carry their secretory product to a surface. These glands include the sweat, sebaceous, and mammary glands and, the glands that secrete digestive enzymes.
Endocrine Glands
The endocrine glands do not have ducts to carry their product to a surface. They are called ductless glands. The word endocrine is derived from the Greek terms "endo," meaning within, and "krine," meaning to separate or secrete. The secretory products of endocrine glands are called hormones and are secreted directly into the blood and then carried throughout the body where they influence only those cells that have receptor sites for that hormone.
Mechanism of Hormones
Hormones are carried by the blood throughout the entire body, yet they affect only certain cells. The specific cells that respond to a given hormone have receptor sites for that hormone. This is sort of a lock-and-key mechanism. If the key fits the lock, then the door will open. If a hormone fits the receptor site, then there will be an effect. If a hormone and a receptor site do not match, then there is no reaction.
Hormones bring about their characteristic effects on target cells by modifying cellular activity.Hormones are very potent substances, which means that very small amounts of a hormone may have profound effects on metabolic processes. Because of their potency, hormone secretion must be regulated within very narrow limits in order to maintain homeostasis in the body.
The endocrine system is made up of the endocrine glands that secrete hormones. Although there are eight major endocrine glands scattered throughout the body, they are still considered to be one system because they have similar functions, similar mechanisms of influence, and many important interrelationships.
Notice also the similarity of the placement of the glands with the chakras.
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THE CARDIOVASCULAR SYSTEM
The cardiovascular system is sometimes called the blood-vascular, or simply the circulatory, system. It consists of the heart, which is a muscular pumping device, and a closed system of vessels called arteries, veins, and capillaries. As the name implies, blood contained in the circulatory system is pumped by the heart around a closed circle or circuit of vessels as it passes again and again through the various "circulations" of the body.
The vital role of the cardiovascular system in maintaining homeostasis depends on the continuous and controlled movement of blood through the thousands of miles of capillaries that permeate every tissue and reach every cell in the body. It is in the microscopic capillaries that blood performs its ultimate transport function. Nutrients and other essential materials pass from capillary blood into fluids surrounding the cells as waste products are removed.
Numerous control mechanisms help to regulate and integrate the diverse functions and component parts of the cardiovascular system in order to supply blood to specific body areas according to need. These mechanisms ensure a constant internal environment surrounding each body cell regardless of differing demands for nutrients or production of waste products.
The vital role of the cardiovascular system in maintaining homeostasis depends on the continuous and controlled movement of blood through the thousands of miles of capillaries that permeate every tissue and reach every cell in the body. It is in the microscopic capillaries that blood performs its ultimate transport function. Nutrients and other essential materials pass from capillary blood into fluids surrounding the cells as waste products are removed.
Numerous control mechanisms help to regulate and integrate the diverse functions and component parts of the cardiovascular system in order to supply blood to specific body areas according to need. These mechanisms ensure a constant internal environment surrounding each body cell regardless of differing demands for nutrients or production of waste products.
THE LYMPHATIC SYSTEM
The lymphatic system has three primary functions.
First of all, Lymph capillaries pick up excess fluid and proteins and returns them to the venous blood so that swelling does not occur due to excess fluid. After the fluid enters the lymph capillaries, it is called lymph.
The second function of the lymphatic system is the absorption of fats and fat-soluble vitamins from the digestive system and the subsequent transport of these substances to the venous circulation.
The third and probably most well known function of the lymphatic system is defense against invading microorganisms and disease. Lymph nodes and other lymphatic organs filter the lymph to remove microorganisms and other foreign particles. Lymphatic organs contain lymphocytes that destroy invading organisms.
First of all, Lymph capillaries pick up excess fluid and proteins and returns them to the venous blood so that swelling does not occur due to excess fluid. After the fluid enters the lymph capillaries, it is called lymph.
The second function of the lymphatic system is the absorption of fats and fat-soluble vitamins from the digestive system and the subsequent transport of these substances to the venous circulation.
The third and probably most well known function of the lymphatic system is defense against invading microorganisms and disease. Lymph nodes and other lymphatic organs filter the lymph to remove microorganisms and other foreign particles. Lymphatic organs contain lymphocytes that destroy invading organisms.
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THE RESPIRATORY SYSTEM
When the respiratory system is mentioned, people generally think of breathing, but breathing is only one of the activities of the respiratory system. The body cells need a continuous supply of oxygen for the metabolic processes that are necessary to maintain life. The respiratory system works with the circulatory system to provide this oxygen and to remove the waste products of metabolism. It also helps to regulate pH of the blood.
Respiration is the sequence of events that results in the exchange of oxygen and carbon dioxide between the atmosphere and the body cells. Every 3 to 5 seconds, nerve impulses stimulate the breathing process, or ventilation, which moves air through a series of passages into and out of the lungs. After this, there is an exchange of gases between the lungs and the blood. This is called external respiration. The blood transports the gases to and from the tissue cells. The exchange of gases between the blood and tissue cells is internal respiration. Finally, the cells utilize the oxygen for their specific activities: this is called cellular metabolism, or cellular respiration. Together, these activities constitute respiration.
Respiration is the sequence of events that results in the exchange of oxygen and carbon dioxide between the atmosphere and the body cells. Every 3 to 5 seconds, nerve impulses stimulate the breathing process, or ventilation, which moves air through a series of passages into and out of the lungs. After this, there is an exchange of gases between the lungs and the blood. This is called external respiration. The blood transports the gases to and from the tissue cells. The exchange of gases between the blood and tissue cells is internal respiration. Finally, the cells utilize the oxygen for their specific activities: this is called cellular metabolism, or cellular respiration. Together, these activities constitute respiration.
THE DIGESTIVE SYSTEM
The digestive system includes the digestive tract and its accessory organs, which process food into molecules that can be absorbed and utilized by the cells of the body. Food is broken down, bit by bit, until the molecules are small enough to be absorbed and the waste products are eliminated. The digestive tract, also called the alimentary canal or gastrointestinal (GI) tract, consists of a long continuous tube that extends from the mouth to the anus. It includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The tongue and teeth are accessory structures located in the mouth. The salivary glands, liver, gallbladder, and pancreas are major accessory organs that have a role in digestion. These organs secrete fluids into the digestive tract.
Food undergoes three types of processes in the body:
The digestive system prepares nutrients for utilization by body cells through six activities, or functions.
Ingestion: The first activity of the digestive system is to take in food through the mouth. This process, called ingestion, has to take place before anything else can happen.
Mechanical Digestion: The large pieces of food that are ingested have to be broken into smaller particles that can be acted upon by various enzymes. This is mechanical digestion, which begins in the mouth with chewing or mastication and continues with churning and mixing actions in the stomach.
Chemical Digestion: The complex molecules of carbohydrates, proteins, and fats are transformed by chemical digestion into smaller molecules that can be absorbed and utilized by the cells. Chemical digestion, through a process called hydrolysis, uses water and digestive enzymes to break down the complex molecules. Digestive enzymes speed up the hydrolysis process, which is otherwise very slow.
Movements: After ingestion and mastication, the food particles move from the mouth into the pharynx, then into the esophagus. This movement is deglutition, or swallowing. Mixing movements occur in the stomach as a result of smooth muscle contraction. These repetitive contractions usually occur in small segments of the digestive tract and mix the food particles with enzymes and other fluids. The movements that propel the food particles through the digestive tract are called peristalsis. These are rhythmic waves of contractions that move the food particles through the various regions in which mechanical and chemical digestion takes place.
Absorption: The simple molecules that result from chemical digestion pass through cell membranes of the lining in the small intestine into the blood or lymph capillaries. This process is called absorption.
Elimination: The food molecules that cannot be digested or absorbed need to be eliminated from the body. The removal of indigestible wastes through the anus, in the form of feces, is defecation or elimination.
Food undergoes three types of processes in the body:
- Digestion
- Absorption
- Elimination
The digestive system prepares nutrients for utilization by body cells through six activities, or functions.
Ingestion: The first activity of the digestive system is to take in food through the mouth. This process, called ingestion, has to take place before anything else can happen.
Mechanical Digestion: The large pieces of food that are ingested have to be broken into smaller particles that can be acted upon by various enzymes. This is mechanical digestion, which begins in the mouth with chewing or mastication and continues with churning and mixing actions in the stomach.
Chemical Digestion: The complex molecules of carbohydrates, proteins, and fats are transformed by chemical digestion into smaller molecules that can be absorbed and utilized by the cells. Chemical digestion, through a process called hydrolysis, uses water and digestive enzymes to break down the complex molecules. Digestive enzymes speed up the hydrolysis process, which is otherwise very slow.
Movements: After ingestion and mastication, the food particles move from the mouth into the pharynx, then into the esophagus. This movement is deglutition, or swallowing. Mixing movements occur in the stomach as a result of smooth muscle contraction. These repetitive contractions usually occur in small segments of the digestive tract and mix the food particles with enzymes and other fluids. The movements that propel the food particles through the digestive tract are called peristalsis. These are rhythmic waves of contractions that move the food particles through the various regions in which mechanical and chemical digestion takes place.
Absorption: The simple molecules that result from chemical digestion pass through cell membranes of the lining in the small intestine into the blood or lymph capillaries. This process is called absorption.
Elimination: The food molecules that cannot be digested or absorbed need to be eliminated from the body. The removal of indigestible wastes through the anus, in the form of feces, is defecation or elimination.
THE MUSCULAR SYSTEM
The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Muscles, attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction.
The integrated action of joints, bones, and skeletal muscles produces movements and respiration.
In addition to movement, muscle contraction also fulfills some other important functions in the body, such as posture, joint stability, and heat production. Posture, such as sitting and standing, is maintained as a result of muscle contraction. The skeletal muscles are continually making fine adjustments that hold the body in stationary positions. The tendons of many muscles extend over joints and in this way contribute to joint stability.
This is particularly evident in the knee and shoulder joints, where muscle tendons are a major factor in stabilizing the joint.
Heat production, to maintain body temperature, is an important by-product of muscle metabolism. Nearly 85 percent of the heat produced in the body is the result of muscle contraction.
The integrated action of joints, bones, and skeletal muscles produces movements and respiration.
In addition to movement, muscle contraction also fulfills some other important functions in the body, such as posture, joint stability, and heat production. Posture, such as sitting and standing, is maintained as a result of muscle contraction. The skeletal muscles are continually making fine adjustments that hold the body in stationary positions. The tendons of many muscles extend over joints and in this way contribute to joint stability.
This is particularly evident in the knee and shoulder joints, where muscle tendons are a major factor in stabilizing the joint.
Heat production, to maintain body temperature, is an important by-product of muscle metabolism. Nearly 85 percent of the heat produced in the body is the result of muscle contraction.
STRUCTURE OF SKELETAL MUSCLE
A whole skeletal muscle is considered an organ of the muscular system. Each organ or muscle consists of skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue.
Skeletal muscles vary considerably in size, shape, and arrangement of fibers. They range from extremely tiny strands such as the stapedium muscle of the middle ear to large masses such as the muscles of the thigh. Some skeletal muscles are broad in shape and some narrow. In some muscles the fibers are parallel to the long axis of the muscle; in some they converge to a narrow attachment; and in some they are oblique.
Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal muscle may be made up of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering. Each muscle is surrounded by a connective tissue sheath called the epimysium. Fascia, connective tissue outside the epimysium, surrounds and separates the muscles. Portions of the epimysium project inward to divide the muscle into compartments. Each compartment contains a bundle of muscle fibers. Each bundle of muscle fiber is called a fasciculus and is surrounded by a layer of connective tissue called the perimysium. Within the fasciculus, each individual muscle cell, called a muscle fiber, is surrounded by connective tissue called the endomysium.
Skeletal muscle cells (fibers), like other body cells, are soft and fragile. The connective tissue covering furnish support and protection for the delicate cells and allow them to withstand the forces of contraction. The coverings also provide pathways for the passage of blood vessels and nerves.
Commonly, the epimysium, perimysium, and endomysium extend beyond the fleshy part of the muscle, the belly or gaster, to form a thick ropelike tendon or a broad, flat sheet-like aponeurosis. The tendon and aponeurosis form indirect attachments from muscles to the periosteum of bones or to the connective tissue of other muscles. Typically a muscle spans a joint and is attached to bones by tendons at both ends. One of the bones remains relatively fixed or stable while the other end moves as a result of muscle contraction.
Skeletal muscles have an abundant supply of blood vessels and nerves. This is directly related to the primary function of skeletal muscle, contraction. Before a skeletal muscle fiber can contract, it has to receive an impulse from a nerve cell. Generally, an artery and at least one vein accompany each nerve that penetrates the epimysium of a skeletal muscle. Branches of the nerve and blood vessels follow the connective tissue components of the muscle of a nerve cell and with one or more minute blood vessels called capillaries.
Skeletal muscles vary considerably in size, shape, and arrangement of fibers. They range from extremely tiny strands such as the stapedium muscle of the middle ear to large masses such as the muscles of the thigh. Some skeletal muscles are broad in shape and some narrow. In some muscles the fibers are parallel to the long axis of the muscle; in some they converge to a narrow attachment; and in some they are oblique.
Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal muscle may be made up of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering. Each muscle is surrounded by a connective tissue sheath called the epimysium. Fascia, connective tissue outside the epimysium, surrounds and separates the muscles. Portions of the epimysium project inward to divide the muscle into compartments. Each compartment contains a bundle of muscle fibers. Each bundle of muscle fiber is called a fasciculus and is surrounded by a layer of connective tissue called the perimysium. Within the fasciculus, each individual muscle cell, called a muscle fiber, is surrounded by connective tissue called the endomysium.
Skeletal muscle cells (fibers), like other body cells, are soft and fragile. The connective tissue covering furnish support and protection for the delicate cells and allow them to withstand the forces of contraction. The coverings also provide pathways for the passage of blood vessels and nerves.
Commonly, the epimysium, perimysium, and endomysium extend beyond the fleshy part of the muscle, the belly or gaster, to form a thick ropelike tendon or a broad, flat sheet-like aponeurosis. The tendon and aponeurosis form indirect attachments from muscles to the periosteum of bones or to the connective tissue of other muscles. Typically a muscle spans a joint and is attached to bones by tendons at both ends. One of the bones remains relatively fixed or stable while the other end moves as a result of muscle contraction.
Skeletal muscles have an abundant supply of blood vessels and nerves. This is directly related to the primary function of skeletal muscle, contraction. Before a skeletal muscle fiber can contract, it has to receive an impulse from a nerve cell. Generally, an artery and at least one vein accompany each nerve that penetrates the epimysium of a skeletal muscle. Branches of the nerve and blood vessels follow the connective tissue components of the muscle of a nerve cell and with one or more minute blood vessels called capillaries.
MUSCLE GROUPS
There are more than 600 muscles in the body, which together account for about 40 percent of a person's weight.
Most skeletal muscles have names that describe some feature of the muscle. Often several criteria are combined into one name. Associating the muscle's characteristics with its name will help you learn and remember them. The following are some terms relating to muscle features that are used in naming muscles.
Most skeletal muscles have names that describe some feature of the muscle. Often several criteria are combined into one name. Associating the muscle's characteristics with its name will help you learn and remember them. The following are some terms relating to muscle features that are used in naming muscles.
- Size: vastus (huge); maximus (large); longus (long); minimus (small); brevis (short).
- Shape: deltoid (triangular); rhomboid (like a rhombus with equal and parallel sides); latissimus (wide); teres (round); trapezius (like a trapezoid, a four-sided figure with two sides parallel).
- Direction of fibers: rectus (straight); transverse (across); oblique (diagonally); orbicularis (circular).
- Location: pectoralis (chest); gluteus (buttock or rump); brachii (arm); supra- (above); infra- (below); sub- (under or beneath); lateralis (lateral).
- Number of origins: biceps (two heads); triceps (three heads); quadriceps (four heads).
- Origin and insertion: sternocleidomastoideus (origin on the sternum and clavicle, insertion on the mastoid process); brachioradialis (origin on the brachium or arm, insertion on the radius).
- Action: abductor (to abduct a structure); adductor (to adduct a structure); flexor (to flex a structure); extensor (to extend a structure); levator (to lift or elevate a structure); masseter (a chewer).
MUSCLES OF THE TRUNK
The muscles of the trunk include those that move the vertebral column, the muscles that form the thoracic and abdominal walls, and those that cover the pelvic outlet.
The erector spinae group of muscles on each side of the vertebral column is a large muscle mass that extends from the sacrum to the skull. These muscles are primarily responsible for extending the vertebral column to maintain erect posture. The deep back muscles occupy the space between the spinous and transverse processes of adjacent vertebrae.
The muscles of the thoracic wall are involved primarily in the process of breathing. The intercostal muscles are located in spaces between the ribs. They contract during forced expiration. External intercostal muscles contract to elevate the ribs during the inspiration phase of breathing. The diaphragm is a dome-shaped muscle that forms a partition between the thorax and the abdomen. It has three openings in it for structures that have to pass from the thorax to the abdomen.
The abdomen, unlike the thorax and pelvis, has no bony reinforcements or protection. The wall consists entirely of four muscle pairs, arranged in layers, and the fascia that envelops them. The abdominal wall muscles are identified in the illustration above.
The pelvic outlet is formed by two muscular sheets and their associated fascia.
The erector spinae group of muscles on each side of the vertebral column is a large muscle mass that extends from the sacrum to the skull. These muscles are primarily responsible for extending the vertebral column to maintain erect posture. The deep back muscles occupy the space between the spinous and transverse processes of adjacent vertebrae.
The muscles of the thoracic wall are involved primarily in the process of breathing. The intercostal muscles are located in spaces between the ribs. They contract during forced expiration. External intercostal muscles contract to elevate the ribs during the inspiration phase of breathing. The diaphragm is a dome-shaped muscle that forms a partition between the thorax and the abdomen. It has three openings in it for structures that have to pass from the thorax to the abdomen.
The abdomen, unlike the thorax and pelvis, has no bony reinforcements or protection. The wall consists entirely of four muscle pairs, arranged in layers, and the fascia that envelops them. The abdominal wall muscles are identified in the illustration above.
The pelvic outlet is formed by two muscular sheets and their associated fascia.
MUSCLES OF THE UPPER EXTREMITY
The muscles of the upper extremity include those that attach the scapula to the thorax and generally move the scapula, those that attach the humerus to the scapula and generally move the arm, and those that are located in the arm or forearm that move the forearm, wrist, and hand. The illustration below shows some of the muscles of the upper extremity.
Muscles that move the shoulder and arm include the trapezius and serratus anterior. The pectoralis major, latissimus dorsi, deltoid, and rotator cuff muscles connect to the humerus and move the arm.
The muscles that move the forearm are located along the humerus, which include the triceps brachii, biceps brachii, brachialis, and brachioradialis. The 20 or more muscles that cause most wrist, hand, and finger movements are located along the forearm.
Muscles that move the shoulder and arm include the trapezius and serratus anterior. The pectoralis major, latissimus dorsi, deltoid, and rotator cuff muscles connect to the humerus and move the arm.
The muscles that move the forearm are located along the humerus, which include the triceps brachii, biceps brachii, brachialis, and brachioradialis. The 20 or more muscles that cause most wrist, hand, and finger movements are located along the forearm.
MUSCLES OF THE LOWER EXTREMITY
The muscles that move the thigh have their origins on some part of the pelvic girdle and their insertions on the femur. The largest muscle mass belongs to the posterior group, the gluteal muscles, which, as a group, adduct the thigh. The iliopsoas, an anterior muscle, flexes the thigh. The muscles in the medial compartment adduct the thigh. The illustration below shows some of the muscles of the lower extremity.
Muscles that move the leg are located in the thigh region. The quadriceps femoris muscle group straightens the leg at the knee. The hamstrings are antagonists to the quadriceps femoris muscle group, which are used to flex the leg at the knee.
The muscles located in the leg that move the ankle and foot are divided into anterior, posterior, and lateral compartments. The tibialis anterior, which dorsiflexes the foot, is antagonistic to the gastrocnemius and soleus muscles, which plantar flex the foot.
Muscles that move the leg are located in the thigh region. The quadriceps femoris muscle group straightens the leg at the knee. The hamstrings are antagonists to the quadriceps femoris muscle group, which are used to flex the leg at the knee.
The muscles located in the leg that move the ankle and foot are divided into anterior, posterior, and lateral compartments. The tibialis anterior, which dorsiflexes the foot, is antagonistic to the gastrocnemius and soleus muscles, which plantar flex the foot.
Citation to https://training.seer.cancer.gov/ 9/02/2018