Chapter 4: skeletal system and joint actions

these five functions compete with one another. Here are two examples:

- For bones to be strong, they must also be relatively heavy. But that makes movement more challenging, since lighter bones would be easier to transport. - Bones need to be solid to provide protection, and to be solid they need calcium. But when calcium is pulled from bone for the benefit of the muscles or nervous system, bones can become weaker, which reduces their ability to protect the aforementioned organs.

Classifications of Synovial Joints: Synovial joints permit movement and are categorized by the type of movement they allow:

1. Ball-and-socket joint: Also known as an enarthrodial joint, this joint allows a wide range of movement in many directions. Examples are the shoulder and hip joints. 2. Saddle joint: The sellar or saddle joints are like ball-and-socket joints but cannot rotate. The thumbs are the only sellar joints in the human body. 3. Hinge joint: The hinge or ginglymus joints include the elbows, ankles, and knee joints. They allow a wide range of movement in one plane. 4. Gliding joint: The arthrodial or gliding joints of the body include the tarsometatarsal joints of the foot. In these joints, two flat bones press against each other. 5. Pivot joint: Trochoidal or pivot joints rotate around a long axis. The radioulnar joint of the forearm is a pivot joint. 6. Condyloid joint: Also known as an ellipsoid joint, these joints move through two planes of motion. Rotation is not allowed in these joints. The radiocarpal joint of the wrist is one.

The framework of the body includes:

206 bones, along with associated cartilage and joints. Bones can be thought of as a relatively lifeless tissue, but this is not the case. The skeleton is a living organ system that can grow, repair, and remodel.

The human body has

360 joints, and 16 are emphasized as the most problematic for active individuals.

Ligaments are:

70 percent water, with the remaining 30 percent made up of dense, fibrous collagenous tissue. The strength of a ligament is primarily derived from type I collagen fibers, the type that resists strain. Ligaments also possess some elastin, an important elastic protein found in all connective tissues. Elastin allows those tissues to regain their original shape after being stretched.

Important information about the axial skeleton and the appendicular skeleton on page

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Important information about the bone shape classification on page

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Important information about the types of bones on page

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Important information about the veterbral (spine) column on page

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Important information about epiphyseal lines of the femur on page

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Important information about the layers of a long bone on page

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Important information about bony protrusions on page

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Important information about the types of cartilage on page

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Important information about ligaments of the right knee joint on page

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Important information about joint capsules on page

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Important information about the skeletal system and joint actions on (table 4.2) page

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Important information about the classifications of synovial joints on page

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Meniscus

A form of fibrocartilage present in the knee, wrist, acromioclavicular, sternoclavicular, and tempporomandibular joints

Articulate carilage

A form of hyaline cartilage located on the joint surface of bones

Organ system

A group of organs and tissues working together to preform specific functions

Creep

A harmless temporary deformation of connective tissue

Epiphyseal line

A line of cartilage near the end of mature long bones

Tear

A partial or complete separation of tissues due to a stretch vetoed its structural capacity

Laxity

A permanent deformation of connective tissue caused by excessive stretching

X-ray

A photographic or digital image of the internal composition of bones and other har tissues

Computed tomography (CT) scan

A sophiscated type of x-ray that creates images of bone, blood vessels, and soft tissues across multiple layers

Wolff's law

A theory developed by German surgeon Julius Wolff, which states that bone will adapt to the loads placed upon it

Stress fracture

A thin bone crack due to an accumulation of micro damage

Synovial membrane

A thin layer of connective tissue beneath the joint capsule that makes a lubricating fluid

Joint capsule

A thin, strong layer of connective tissues that contain synovial fluid in freely moving joints

Hyaline cartilage

A transparent cartilage found on most joint surfaces and in the respiratory tract which contains no nerves or blood vessels

Ddepesotion

Adding new bone with osteoblast

Bones rely on three different cell types during remodeling.

After bone is damaged, osteoclasts chew up the impaired bone tissue (resorption). Osteoclasts are also responsible for the loss of bone when a person is inactive due to injury or disease. Next, if there's a stimulus for growth, osteoblasts lay down new bone (deposition). Finally, these osteoblasts transform into osteocytes, or mature bone cells.

Synovial joints

Also known as diathrosis. They join bones with a fibrous joint capsule that is continuous with the periosteum of the joined bones, constitute the outer boundary of a synovial cavity, and surround the bones' articulating surfaces

Varus

An abnormal joint movement away from the midline of the body, which can result in bowlegs at the knee joints

Valgus

An abnormal joint movement toward the midline of the body which can result in knock knees at the knee joint

Fibrocartilage

An elastic and tough tissue that contains type 1 and type 2 collagen

Bony protrusion

An eminence on the surface of bones that increase strength and contact area for the muscle attachments

COMMON BONE MARKINGS

Angles: sharp bony angulations that may serve as bony or soft tissue attachments but often are used for precise anatomical description. Examples include the superior, inferior, and acromial angles of the scapula. Body: usually refers to the largest, most prominent segment of bone. Examples include the shaft of long bones like the femur and humerus. Condyle: refers to a large prominence that often provides structural support to the overlying hyaline cartilage. It bears the brunt of the force exerted from the joint. An example is the knee joint (hinge joint). Crest: a raised or prominent part of the edge of a bone. Crests are often the sites where connective tissue attaches muscle to bone. The iliac crest is found on the ilium. Diaphysis: refers to the main part or the shaft of a long bone. Long bones, including the femur, humerus, and tibia, all have a shaft. Epicondyle: a prominence that sits atop a condyle. The epicondyle attaches muscle and connective tissue to bone, providing support to this musculoskeletal system. Examples include the femoral medial and lateral epicondyles. Epiphysis: the articulating segment of a bone, usually at the proximal and distal poles of the bone. It usually has a larger diameter than the shaft (diaphysis). The epiphysis is critical for the growth of bone because it sits adjacent to the physeal line, also known as the growth plate. Facet: a smooth, flat surface that forms a joint with another flat bone or another facet, together forming a gliding joint. Examples can be seen in the facet joints of the vertebrae, which allow for flexion and extension of the spine. Fissure: an open slit in a bone that usually houses nerves and blood vessels. Examples include superior and inferior orbital fissure. Foramen: a hole through which nerves and blood vessels pass. Examples include supraorbital foramen, infraorbital foramen, and mental foramen on the cranium. Fossa: a shallow depression in the bone surface. Here it may receive another articulating bone or act to support brain structures. Examples include trochlear fossa and posterior, middle, and anterior cranial fossa. Groove: a furrow in the bone surface that runs along the length of a vessel or nerve, providing space to avoid compression by adjacent muscle or external forces. Examples include a radial groove and the groove for the transverse sinus. Head: a rounded, prominent extension of bone that forms part of a joint. It is separated from the shaft of the bone by the neck. The head is usually covered in hyaline cartilage inside a synovial capsule, as it is the main articulating surface with the adjacent bone, together forming a ball-and-socket joint. Margin: the edge of any flat bone. It can be used to accurately define a bone's borders. For example, the edge of the temporal bone articulating with the occipital bone is called the occipital margin of the temporal bone. And vice versa, the edge of the occipital bone articulating with the temporal bone is called the temporal margin of the occipital bone. Meatus: a tubelike channel that extends within the bone that may provide passage and protection to nerves, vessels, and even sound. Examples include external acoustic meatus and internal auditory meatus. Neck: the segment between the head and the shaft of a bone. It is often demarcated from the head by the presence of the physeal line in pediatric patients and the physeal scar (physeal line remnant) in adults. It is often separated into the surgical neck and anatomical neck. The anatomical neck, which may represent the old epiphyseal plate, is often demarcated by its attachment to capsular ligaments. The surgical neck is often more distal and is demarcated by the site on the neck that is most commonly fractured. For example, in the humerus, the anatomical neck runs obliquely from the greater tuberosity to just inferior to the humeral head. The surgical neck runs horizontally and a few centimeters distal to the humeral tuberosities. Notch: a depression in a bone that often, but not always, provides stabilization to an adjacent articulating bone. The articulating bone will slide into and out of the notch, guiding the range of motion of the joint. Examples include the trochlear notch on the ulna, radial notch of the ulna, suprasternal notch, and the mandibular notch. Ramus: the curved part of a bone that gives structural support to the rest of the bone. Examples include the superior and inferior pubic ramus and ramus of the mandible. Sinus: a cavity within any organ or tissue. Examples include paranasal sinuses and dural venous sinuses. Spinous process: a raised, sharp elevation of bone where muscles and connective tissue attach. It is different than a normal process in that a spinous process is more pronounced. Trochanter: a large prominence on the side of the bone. Some of the largest muscle groups and most dense connective tissues attach to the trochanter. The most notable examples are the greater and lesser trochanters of the femur. Tuberosity: a moderate prominence where muscles and connective tissues attach. Its function is similar to that of a trochanter. Examples include the tibial tuberosity, deltoid tuberosity, and ischial tuberosity. Tubercle: a small, rounded prominence where connective tissues attach. Examples include the greater and lesser tubercle of the humerus.

Osteoporosis

Bone disease characterized by a loss in bone mass and density

Osteoarthritis

Bone on bone contact that results in joint pain and stiffness from a loss of articular cartilage

Bone structure

Bones are rich with blood vessels, cells, and nerves that allow them to perform all functions. The periosteum and endosteum are connective tissues that cover long bones. They contain the cells responsible for growth, repair, and remodeling. The periosteum covers the outside of bones, while the endosteum covers the inner lining of bones and the medullary cavity.

Appendicular skeleton

Bones of the upper and lower extremities - The remaining 126 bones of the upper and lower extremities form the appendicular skeleton

Osteoblasts

Cells responsible for bone deposition

Medullary cavity

Central cavity of the bone shaft where marrow is stored.

The location of a ligament can be extrinsic, intrinsic, or capsular with respect to the joints. The knee joint can serve as an example, given it contains all three types of ligaments.

Extrinsic ligament: This type of ligament is located on the outside of the joint. An example is the lateral collateral ligament (LCL), which resists varus stress. Intrinsic ligament: The anterior cruciate (ACL) and posterior cruciate (PCL) ligaments are situated inside the knee joint to resist anterior and posterior movement of the tibia, respectively. Capsular ligament: The medial collateral ligament (MCL) is a capsular ligament, so called because it's continuous with the joint capsule. It resists valgus stress at the knee by keeping the joint approximated.

The largest bone in the body is the

Femur For males it is approximately 18.9 inches long and .92 inches in diameter

Did you know 2:

Ligaments are normally very taut around a joint. However, some people are born with atypically loose ligaments, which allow the joints to move through a greater range of motion. Even though it might seem advantageous to have extreme flexibility—what is sometimes called double jointed—loose ligaments make people more susceptible to joint dislocations and osteoarthritis.

Osteocytes

Mature bone cells that maintain a a bones matrix

Axial skeleton

The bones of the skull, vertebral column, sternum, rib cage, and sacrum - composed of 80 bones from the skull, vertebral column, rib cage, sternum, and sacrum

Spinous process

The bony protrusion on the posterior surface of a vertebra where muscles and ligaments attach

Transverse porcess

The bony protrusion on the right and left side of a vertebra where muscles and ligaments attach

The skeletal system serves many roles required for optimum health, movement, and protection. There are five primary functions of the skeletal system:

Movement: Bones come together to form joints that allow motion. Structure and support: The skeleton provides the structure and support needed for movement. This structure separates humans from amoebas or jellyfish. Protection: Without the skeleton, such essential organs as the brain, spinal cord, heart, and lungs would have no protection. Calcium storehouse: Calcium and other minerals are stored within bone. Blood cell production: Marrow within bone produces blood.

Nociceptors

Pain sensitive nerve endings

Spongy bone

Porous, light inner layer of bone tissue

Reabsorption

Removing bone with osteoclasts

The smallest bone in the body is the

Stapes - located in the ear - its approximately 3x 2.5 millimeters

Ossification

The hardening process of bones during development

Facet joints

The joints between two adjacent vertebrae that guide and restrict movement of the vertebral column - the facet joints are arranged throughout the spine to guide flexion and extension and to limit rotation, especially in the lower portion of the vertebral column.

Epiphyseal plate

The location of bone growth near the end of immature bones

Periosteum

The outer covering of bone where osteoblast are located

Remodeling

When a bone changes shape by either increasing or decreasing its diameter

Did you know 1:

You've probably heard that weight training will stunt a child's growth. It is unclear where this hypothesis came from, but it's pervasive in society. All forms of exercise, from running to lifting weights to lifting heavy objects, enhances a child's development by strengthening the skeleton and muscles. "There's absolutely no evidence that weight training will stunt a child's growth," says George Salem, PhD, associate professor at the University of Southern California's Division of Biokinesiology and Physical Therapy. "When you see short athletes in gymnastics or weight training, it's due to genetics." In other words, the young athletes that grew taller didn't make the cut.

Osteoclasts

cells responsible for bone resorption

The vertebral (spinal) column, within the axial skeleton, consists of five different regions:

cervical, thoracic, lumbar, sacrum, and coccyx. These five regions are made up of 33 vertebrae. From that total, 24 of the vertebrae can move independently, while the other 9 are fused (5 within the sacrum and 4 within the coccyx).

the head of the femur contains two primary protrusions:

greater trochanter and lesser trochanter. A trochanter, or protrusion, is the site of muscle and ligament attachment. The increased anatomical area serves two purposes: 1. to strengthen the bone in that region and 2. to provide a greater contact surface for the muscles and ligaments to attach.

Bone receives its blood from three different sources:

periosteal vessels, nutrient arteries, and epiphyseal vessels. These three vessels ensure that blood is available to all areas of the bone, from the innermost spongy bone to the outer compact bone.

Ligaments are also responsible for the following:

• Attaching bone to bone • Passively stabilizing and guiding a joint • Resisting excess movement at a joint • Allowing the brain to sense the position of the joint in space (covered in Unit 4)

Bone consists of two different materials: the compact outer layer and the spongy inner portion.

• Compact (cortical) bone: This hard outer layer of dense tissue is strong, solid, and resistant to bending. Approximately 80 percent of a person's skeletal mass comes from compact bone. • Spongy (trabecular or cancellous) bone: This light, porous material forms a latticework of bony structures called trabeculae. Osteoporosis is primarily due to the weakening of spongy bone, but compact bone thins as well.

The following provides an explanation of the three types of cartilage:

• Hyaline cartilage: This deformable but elastic type of cartilage is the most widespread. It's located in the nose, trachea, larynx, bronchi, and the ends of ribs, as well as at the ends of bones in the form of articular cartilage. • Fibrocartilage: This tough tissue is located in the intervertebral discs and at the insertions of tendons and ligaments. It also forms the lateral or medial meniscus in the knee. • Elastic cartilage: As the name implies, this is the most pliable form of cartilage. It gives shape to the external ear, the auditory tube of the middle ear, and the epiglottis.

Trabeculae

Functional units of spongy bone

Compact bone

Hard dense outer layer of bone tissue

Elastin

Highly elastic protein found in connective tissues that allows it to return to its original shape after being stretched

Based on their shape, bones are classified in 5 ways:

1. Long bones: Hard, dense bones that provide strength, structure, and mobility. A long bone has a shaft and two ends. They are longer than they are wide with a cylinder shape. 2. Flat bones: Protect the internal organs and provide a large surface area for muscles to attach. They are somewhat flat and thin but may be curved, as in the ribs. 3. Short bones: Their primary function is to provide support and stability with little to no movement. In the body, they are typically cube shaped. 4. Sesamoid bones: A small independent bone or bony nodule developed in a tendon where it passes over an angular structure, typically in the hands and feet. They reinforce and protect tendons from stress and wear and tear. 5. Irregular bones: Because of their peculiar form, they cannot be grouped as long, short, flat, or sesamoid bones. They help protect vital organs. They have complex shapes, like the vertebrae.

Fibrous joints

Connected by dense connective tissue consisting mainly of collagen. Fibrous joints are called "fixed" or "immovable" joints because they do not move

Cartilaginous joints

Connected entirely by cartilage. They allow more movement between bones than a fibrous joint but less than synovial joints

ligament

Connective tissue that connects bones

Endosteum

Connective tissue that covers the inside of bone and the medullary cavity

Joint classification: there are three classifications of joints in the human body:

Fibrous joints are connected by dense connective tissue made of collagen. There are three types of fibrous joints: • Synarthrodial joints are found in the skull. During birth, sutures are flexible to allow the fetus to pass through the birth canal. However, they become more rigid as the child grows. • Syndesmoses are found between the long bones. These are only slightly movable. • Gomphosis joints attach teeth to the sockets of the maxilla and mandible. Cartilaginous joints are joined by either fibrocartilage or hyaline cartilage. These are slightly movable. Cartilaginous joints are divided into primary and secondary joints. Epiphyseal (growth) plates are primary. Secondary cartilaginous joints include the manubriosternal joint, intervertebral discs, and the symphysis pubis. Synovial joints are the most movable joints. Bones are separated by a synovial cavity made of dense, irregular connective tissue.

Elastic cartilage

Flexible cartilage present in the outer ear and inner ear, and epiglottis

Osteons (haversian systems)

Functional units of compact bone