Chapter 6

1 “List and describe the functions of bones”

Bones form the skeleton, which provides the structure of the body, and are made of connective tissue (OpenSTAX, 2018). As part of the skeletal system, bones support the body, facilitate movement, protect internal organs, and produce blood cells (OpenSTAX, 2018). Bones are hard and rigid; they allow the muscles to attach to them, which provides the overall structure of the body. At the joints, bones and cartilage connect, muscle tissue contracts to allow movement. The skull, spine, ribs, pelvis, and several other key structures protect internal organs, as well as tendons and other supporting structures. Red marrow inside the bones perform hematopoiesis, which is the formation of red blood cells for the body (OpenSTAX, 2018).

2 “Describe the classes of bones”

There are 206 bones in the adult human body, each of those bones falls into one of five classes based on their shape (OpenSTAX, 2018). The five classes of bones are long bones, short bones, flat bones, irregular bones, and sesamoid bones.

Long bones are longer than they are wide and function as levers because they move when muscles contract (OpenSTAX, 2018). The bones found in the arms, legs, fingers, and toes are all long bones.

Short bones are generally cube-shaped and provide support for other structures (OpenSTAX, 2018). The only short bones in the human body are the carpals and tarsals.

Flat bones are typically thin and often curved, they often function as connection points for other structures (OpenSTAX, 2018). The cranial bones, the scapulae, sternum, and ribs are all classified as flat bones.

Irregular bones do not fall into any other classifications and serve a variety of functions throughout the body. The vertebrae and facial bones have unique shapes that are dissimilar to any other bones in the body and fall into the irregular classification (OpenSTAX, 2018).

Sesamoid bones are shaped like sesame seeds and protect tendons from compressive force (OpenSTAX, 2018). The patellae is a sesamoid bone found in all humans, but other sesamoid bones in the hands and feet are unique and vary from person to person (OpenSTAX, 2018).

3 “Discuss the process of bone formation and development”

During early embryonic development, fibrous membranes and hyaline cartilage make up the bones of the skeleton (OpenSTAX, 2018). As gestation progresses, the skeleton ossifies into hard bones. There are two processes in which bones are formed, intramembranous ossification and endochondral ossification, but both result in the same end material. Immature bones in children are able to grow, allowing them to grow taller as they get older. Epiphyseal plates, often referred to as growth plates, allow for the formation of new bone, which allows for bones to grow in size (OpenSTAX, 2018). The growth plates in mature bones are ossified, preventing continued growth.

4 “Explain how bone repairs itself after a fracture”

When a bone is fractured, it must be placed in the correct anatomical position or the healing process will fuse the bone fragments together incorrectly (OpenSTAX, 2018). When bones are able to be set into a natural position without the use of surgery, the procedure is called closed reduction (OpenSTAX, 2018). If the fracture requires surgery to set it back into place, the procedure is known as open reduction (OpenSTAX, 2018). The healing process begins with a hematoma surrounding the fracture, then new blood vessels connect to one another between the fractured pieces, then bony callous forms around the new growth (OpenSTAX, 2018). The bony callous will solidify and strengthen, resulting in a healed fracture.

5 “Discuss the effect of exercise, nutrition, and hormones on bone tissue”

Like other organ systems in the human body, the skeletal system is dependent on other bodily processes. Exercise, or mechanical stress, is required to keep bones hard. Without mechanical stress, bones weaken and can even lose mass. Certain nutrients, such as Calcium and Vitamin D, are critical to the health of bones (OpenSTAX, 2018). The skeletal system is an important organ system that provides blood cells to the rest of the body, that output requires nutrients. Hormones play a critical role in bone strength and density. Sex hormones in children are what drive bones to grow and strengthen.

6 “Describe how an imbalance of calcium can affect bone tissue”

An imbalance of calcium is known as either hypocalcemia, low levels of calcium, or hypercalcemia, high levels of calcium, and can impact nearly every aspect of life (OpenSTAX, 2018). An imbalance is often a symptom of a larger problem, such as a hormone imbalance, and can make bones brittle or function poorly. Hypocalcemia can result in poor blood coagulation, heart arrhythmia, and other symptoms. Hypercalcemia can result in lethargy, sluggish reflexes, and confusion (OpenSTAX, 2018).

Chapter 7

1 “Describe the functions of the skeletal system and define its two major subdivisions”

The skeletal system consists of bones, cartilage, and ligaments, and forms the internal framework of the body (OpenSTAX, 2018). The skeleton provides the framework of the body and protects internal organs. The skull, ribs, spine, pelvis, and other bones protect soft tissues from harm. The skeletal system is divided into two major subdivisions, the axial and appendicular.

The axial skeleton provides the upright frame of the body and includes the head, neck, chest, and back (OpenSTAX, 2018). The protection of the brain, spinal cord, lungs, and other soft tissues in the cranial and thoracic regions are all the responsibility of the axial skeleton. The appendicular skeleton contains more bones than the axial skeleton and makes up the long bones in the limbs, as well as the much smaller bones in the hands and feet.

2 “Identify the bones and bony structures of the skull, the cranial suture lines, the cranial fossae, and the openings in the skull”

The skull is comprised of the braincase, which is comprised of several fused bones, the upper and lower jaws, nose, orbits, and other structures (OpenSTAX, 2018). The cranial sutures are the places where bones create an immobile joint between adjacent bones; they contain dense connective tissue that keeps them together and strengthens the braincase. The cranial fossae are the three spaces on the interior of the skull that conform to the shape of the brain; they further serve to allow blood vessels and cranial nerves into the skull (OpenSTAX, 2018). The exterior structures of the skull that comprise the aesthetics of a head are generally the frontal and parietal bones, orbits, zygomatic bones, maxilla, mandible and the mental protuberance, nasal bone, and teeth. The mouth, orbits, and nasal opening are the three primary openings to the skull. The below image is the anterior view of the skull to illustrate:

https://cnx.org/resources/2b992922f28d116ef649105fc6d93b2880df5084/704_Skull-01.jpg

3 “Discuss the vertebral column and regional variations in its bony components and curvatures”

The vertebral column protects the spinal cord from the upper neck to the pelvis and is often referred to as the spine or spinal column. The vertebral column is comprised of individual vertebra, each of which is separated by an intervertebral disc (OpenSTAX, 2018). The following is an illustration of the vertebrae separated by an intervertebral disc, all of which are surround the spinal cord:

https://cnx.org/resources/4b8ca232c0ac2d22d1ba1be3b8ce86ea2975f5ea/716_Intervertebral_Disk.jpg

The vertebral column consists of 33 vertebrae, which is eventually reduced to 24 as the bones fuse as they mature (OpenSTAX, 2018). The vertebrae are divided into five separate regions, the cervical vertebrae, the thoracic vertebrae, the lower back, the sacral vertebrae, and the coccygeal vertebrae (OpenSTAX, 2018). Each region has different structures and roles; the lower back region, for instance, bears a great deal of vertical weight, so the individual vertebrae are wide and squat in comparison to the other regions.

4 “Describe the components of the thoracic cage”

The thoracic cage is often known as the rib cage and provides safety to internal organs and other soft tissues (OpenSTAX, 2018). The thoracic cage consists of 12 pairs of ribs, as well as their costal cartilage, and the sternum (OpenSTAX, 2018). The cartilage allows the ribs the flexibility to move as the lungs inflate and deflate. The ribs connect to each of the thoracic vertebrae to the posterior and to the sternum to the anterior, only the top seven of 12 ribs connect to the sternum with costal cartilage (OpenSTAX, 2018). The top seven ribs are referred to as true ribs, they connect to both the thoracic vertebrae and the sternum (OpenSTAX, 2018). The lungs and heart are both protected by the thoracic cage, as well as other soft tissues.

5 “Discuss the embryonic development of the axial skeleton”

Embryonic development refers to the development that occurs while an embryo is in utero. The axial skeleton refers to the bones of the head, neck, back, and chest. The axial skeleton begins to develop early in embryonic development (OpenSTAX, 2018). The brain and spinal cord begin to develop first, beginning with a rod-like structure known as a notochord (OpenSTAX, 2018). As the brain and spinal cord develop, other structures begin to develop that eventually become fibrous connective tissue, cartilage, and some bones of the body (OpenSTAX, 2018). The skull does not completely form in utero. During birth, a newborn’s skull adjusts to move through the birth canal. In the weeks and months following birth, the cranial plates begin to fuse.

Chapter 8

1 “Discuss the bones of the pectoral and pelvic girdles, and describe how these unite the limbs with the axial skeleton”

The pectoral girdle refers to the bones that attach the upper limbs to the axial skeleton, also known as the shoulder girdle, and is comprised of the scapula and clavicle (OpenSTAX, 2018). The pelvic girdle, also known as the hip girdle, is formed by a single bone, the coxal bone, and is the point at which the femurs attach to the torso (OpenSTAX, 2018). The pectoral and pelvic girdles allow the limbs to attach the torso and for them to actuate or move in their socket.

2 “Describe the bones of the upper limb, including the bones of the arm, forearm, wrist, and hand”

The arm, forearm, wrist, and hand all comprise the upper limb (OpenSTAX, 2018).

The arm is comprised of only the humerus, which is the long bone of the upper arm. The head of the humerus enters the glenoid cavity of the scapula, which allows the arm to move (OpenSTAX, 2018).

The forearm is comprised of the radius and ulna, which run parallel from the humerus to the wrist. The radius is on the lateral, thumb, side and the ulna is the medial bone (OpenSTAX, 2018).

There are eight carpal bones that comprise the wrist (OpenSTAX, 2018). The carpal bones form the base of the hand and are arranged in two rows. The distal row contains the trapezium, trapezoid, capitate, and hamate. The proximal row contains the scaphoid, lanate, triquetrum, and pisiform.

The hand contains five elongated metacarpal bones, the bones are between the wrist and the fingers (OpenSTAX, 2018). The metacarpals are attached to the fingers, also known as phalanges. The phalanges are comprised of the proximal, middle, and distal bones – the thumbs do not have middle bones.

3 “Identify the features of the pelvis and explain how these differ between the adult male and female pelvis”

The pelvis is comprised of four bones, the left and right hip bones, the sacrum, and the coccyx (OpenSTAX, 2018). The pelvis primarily supports the weight of the upper body and serves as an attachment point for the upper and lower body. The female pelvis has evolved for childbirth and is broader than the male pelvis. Males are larger than females, so the bones are thicker and heavier. The pelvic inlet for women is rounder and the subpubic region is wider than in males.

4 “Describe the bones of the lower limb, including the bones of the thigh, leg, ankle, and foot”

The lower limbs are divided into three regions, the thigh, the leg, and the foot (OpenSTAX, 2018). The thigh is between the hip and the knee joint and consists of the femur. The femur is the longest bone of the body and comprises more than one quarter of a person’s height (OpenSTAX, 2018). The joint where the leg and thigh meet is known as the patella, tendons run across the joint and are used to actuate the leg. The leg consists of the bones between the knee and the ankle joint. The leg bones are the tibia and fibula, the tibia is the anterior bone and the fibula is dorsal. At the distal end of the leg is the ankle and foot. The foot and ankle are at the base of the leg and contain more than 30 bones.

5 “Describe the embryonic formation and growth of the limb bones”

Limb bones begin to form during embryonic formation. The bones begin as an embryonic tissue known as mesenchyme and can differentiate into bone and muscle tissue (OpenSTAX, 2018). In addition to the limbs, the tissue also forms the pectoral and pelvic girdles. In the early stages of limb development, the upper and lower limbs begin as limb buds. The early limb buds are a core of mesenchyme covered by a layer of ectoderm (OpenSTAX, 2018). Later in development, at about the sixth week, the distal portion of the limb bud becomes paddle-shaped and will later become the feet and hands.

Chapter 9

1 “Discuss both functional and structural classifications for body joints”

Joints are connections where adjacent bones are joined and articulate or move around. The structural classifications of joints refer to whether the bones are connected by fibrous connective tissue or if there is a fluid-filled joint cavity connecting them (OpenSTAX, 2018). Functional classifications refer to the range of motion for a joint, from immobile to highly mobile (OpenSTAX, 2018).

Structural classifications are divided into fibrous joints, cartilaginous joints, and synovial joints. Fibrous joints are held together by fibrous connective tissue. Cartilaginous joints are held together by a type of cartilage. In synovial joints, bones are not actually in contact but are connected through a fluid-filled joint cavity that provides lubrication. Most joints in the body are synovial joints (OpenSTAX, 2018).

Functional classifications are used to define whether a joint is immobile, slightly moveable, or freely moveable. Some joints are held together so tightly by fibrous connective tissue; they are functionally immobile. On the other end of the spectrum, all synovial joints are classified as freely moveable.

2 “Describe the characteristic features for fibrous, cartilaginous, and synovial joints and give examples of each”

Fibrous joints are held together tightly by fibrous connective tissue. Examples often include joints between bones that protect organs. The pelvis, cranial sutures on the skull, and the sternum are all classified as fibrous joints because the joints effectively fuse the bones together.

Cartilaginous joints are held together by one of two types of cartilage (OpenSTAX, 2018). The spaces between vertebrae are filled with a cartilage tissue that is semi-flexible, allowing some mobility along the spine without compromising the spinal cord.

Diarthrosis joints are freely moveable and are mostly made up of synovial joints. The appendicular skeleton is where most diarthrosis joints are found, providing highly mobile movements. Examples include the hip and shoulder joints, which are further classified as multiaxial.

3 “Define and identify the different body movements”

Movements are contractions or relaxation of muscles resulting in movement of bones at each joint. There are several types of movement, and they are often characterized by how they vary from the anatomical position.

Flexion and extension refer to movements within the sagittal plane. Forward and backward movement of limbs, such as kicking back and forth or shaking the head “yes” would be movements within the sagittal plane.

Adduction and abduction movements occur along the coronal plane. Movement along the coronal plane would include raising the arm to the side and back.

Circumduction is a circular movement of a region of the body, traversing the sagittal and coronal plane. While stationary, moving the feet or hands in a circular motion would be an example of circumduction.

Rotation is a twisting movement within the vertebral column, at a pivot joint, or a ball-and-socket joint, such as the shoulder or hip (OpenSTAX, 2018). Twisting the head, hips, or shoulders would be an example of rotation.

Supination and pronation are movements of the forearm (OpenSTAX, 2018). The movement is achieved by, from the anatomical position, the hand is rotated back and forth.

Dorsal and plantar flexion are the movements of the ankle. The movement is achieved when the foot points up and down.

Inversion and eversion are the movements of the feet. When the foot turns inward toward the midline or outward, the movement is achieved.

Protraction and retraction occurs in the jaw and shoulder. The movement is achieved when the joint is moved forward or back from the natural position. Depression and elevation also occur in the jaw and shoulder; they refer to up and down movements. Excursion is the side-to-side movement of the lower jaw. Superior and interior rotation occurs in the glenoid cavity of the shoulder, they refer to up and down rotations along the coronal plane.

Opposition refers to the movement of the thumb. The movement occurs when the tip of the thumb touches another finger.

4 “Discuss the structure of specific body joints and the movements allowed by each”

The knee, elbow, and ankle are all synovial and hinge joints. Hinge joints allow flexion and extension movements on the sagittal plane from the anatomical position. Kicking or raising the hand to the shoulder are examples of the movement.

The hip and shoulder are ball-and-socket joints. Ball-and-socket joints allow movement along all axes. The joint allows movement in any direction along the coronal or sagittal plane from the anatomical position.

5 “Explain the development of body joints”

Joints begin to form in conjunction with associated bones while in embryonic development. The same tissue that begins the creation of bones and associated tissues, mesenchyme, begins the creation of the joints for the body. Until the developing bones grow enough to be close, the gaps are known as fontanelles. Over time, connective tissue will begin to bind the bones together.

Chapter 10

1 “Explain the organization of muscle tissue”

Muscle tissue is organized into three types: skeletal muscle, cardiac muscle, and smooth muscle (OpenSTAX, 2018). All three types of muscle exhibit many key characteristics, such as their excitability in response to stimuli. As the name implies, skeletal muscle is attached to bones and is the most noticeable to outside observers. Smooth muscle is involuntary, it is used to perform routine functions without need for involvement of the individual. Cardiac muscle is also involuntary and comprises the heart.

2 “Describe the function and structure of skeletal, cardiac muscle, and smooth muscle”

Skeletal muscle contracts and relaxes to cause movement. Skeletal muscles contract and adjust constantly to maintain a balanced and upright posture (OpenSTAX, 2018). Skeletal muscle tissue also creates heat when contracting, burning ATP and contributing to homeostasis. Skeletal muscles are a compilation of several other tissues such as muscle fibers, multiple layers of connective tissue, blood vessels, and nerves.

Cardiac muscle is only found in the heart and has unique properties compared to the other types of tissues. The muscle contracts in a highly coordinated rhythm to allow blood to pump through from one ventricle to the next until the leaves the heart. The heart is responsive to the autonomic nerve system (ANS), as well as some hormonal signals, to regulate blood pressure (OpenSTAX, 2018).

Smooth muscle makes up the walls of hollow organs such as the stomach, intestines, uterus, and bladder (OpenSTAX, 2018). The muscle contracts involuntarily to perform a variety of functions like changing the size of the lens of the eye and making hair stand up when it’s cold (OpenSTAX, 2018).

3 “Explain how muscles work with tendons to move the body”

Skeletal muscles work with tendons to move the bones of the body. The muscles attach to the bones directly through the tendons allowing contractions to pull on bones to achieve movement.

4 “Describe how muscles contract and relax”

A muscle contraction occurs when a muscle fiber becomes thicker and shorter, often putting pressure on the tendons and bones resulting in actuation. Muscles contract when electrical signals are applied to the tissue through motor neurons. When the signal stops, the muscle relaxes. When the stimulation of the muscle ceases and the muscle relaxes, the tendons and bones return to their resting position.

5 “Define the process of muscle metabolism”

Muscles require energy to contract, but not all muscles require the same amount of energy to perform their function. Muscles require energy in the form of ATP, oxygen, and other nutrients to perform. When that energy is consumed, it produces what is known as metabolic waste.

6 “Explain how the nervous system controls muscle tension”

The nervous system controls muscle tension by carefully applying electrical impulses as needed to perform a function. Each muscle fiber is innervated by only one motor neuron, the group of fibers are controlled by another motor neuron known as a motor unit (OpenSTAX, 2018). Small motor units control fine movement such as those in the eye while larger motor units control simpler movements such as those in the knee (OpenSTAX, 2018). When a stimulus is applied, the muscle fibers contract rapidly followed by a much slower relaxation.

7 “Relate the connections between exercise and muscle performance”

Muscle performance can be improved or lessened by the frequency and intensity of exercise. With age or simply lack of exercise, muscles can atrophy. Certain disorders, such as Muscular Dystrophy, can result in muscle atrophy early in life and prevent hypertrophy, or muscle growth. The metabolism of muscles can also be improved through exercise. Muscle metabolism is the amount of exertion and energy needed to perform a function – when muscles are trained to do a specific task, the energy cost goes down and efficiency improves.

8 “Explain the development and regeneration of muscle tissue”

Muscle begins to develop early during the embryonic development. The number of muscle cells are fixed during development, but satellite cells can facilitate protein synthesis required for muscle growth and development. The satellite cells are able to regenerate, but their primary purpose is to repair living tissue. Smooth muscle, unlike skeletal and cardiac muscles, can regenerate by use of pericyte, a type of stem cell found in small blood vessels. With very few exceptions, cardiac muscle is unable to repair, and will instead be replaced with scar tissue in the event that tissue death occurs.

Chapter 11

1 “Describe the actions and roles of agonists and antagonists”

The principle muscle in a movement, such as the bicep in actuating the forearm, is known as the agonist (OpenSTAX, 2018). The muscle opposite of the principle movement, such as the triceps extending the forearm from the upper arm, is known as the antagonist (OpenSTAX, 2018). When the bicep contracts, the triceps perform the opposite to allow the forearm to actuate. The triceps contract while the biceps relax when the forearm extends.

2 “Explain the structure and organization of muscle fascicles and their role in generating force”

A bundled group of muscle fibers are known as fascicles. Those bundled groups are covered by a layer connective tissue called perimysium (OpenSTAX, 2018). Most skeletal muscles have fascicles that are arranged parallel to the long axis of the muscle. The way the fascicles are arranged impacts the amount of force that can be applied and the range of motion.

3 “Explain the criteria used to name skeletal muscles”

The names of skeletal muscles often use Latin or Greek words with one or more roots to explain what and where it is on the body. In short, the word tells the reader where the muscle is and the roots are modifiers that explain exactly which part of the muscle group. An example of this would be the pectoral muscles. The word “pectoral” refers to the breast, “major” or “minor” further refines the term to tell the reader whether it is the larger or smaller muscle group.

4 “Identify the skeletal muscles and their actions on the skeleton and soft tissues of the body”

Skeletal muscles actuate the parts of the body to allow movement. Skeletal muscles connect to bones through tendons and other tissues to allow movement. The skeletal muscles, along with bones, also function to protect some internal organs. The chest and stomach, in particular, are protected by skeletal muscles by serving as both a barrier and as tissue holding the bones of the chest and spine together.

5 “Identify the origins and insertions of skeletal muscles and the prime movements”

The moveable end of a muscle attached to a bone is called the insertion. For example, where the bicep attaches to the forearm would be referred to as the insertion. The fixed end of a muscle is called the origin. And example of an origin would be where the bicep attaches to the shoulder. When the bicep contracts, the insertion point actuates the forearm while leaving the origin with almost no movement. When the bicep relaxes, the origin remains nearly fixed while the insertion extends allow the forearm to extend.

References

OpenSTAX. (2018, April 9). Anatomy & Physiology. OpenSTAX CNX. Retrieved from http://cnx.org/contents/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@9.1