What are six functions of the musculoskeletal system?

Support, Movement, Protection of vital organs, Mineral storage, Metabolism, Hematopoiesis

The site of origin is _____.

Fixed

The site of insertion is _______.

Working

Muscles attach to bone by _______.

Tendons

Bones attach to each other by _______.

Ligaments

The skeletal system is _____ of body weight.

20%

Axial skeleton offers ______.

Support

Appendicular skeleton promotes ________.

Movement

What is bone?

Specialized connective tissue

What cells are embedded in bone’s calcified extracellular matrix?

osteocytes, osteoblasts, osteoclasts

What three components make up bone?

protein fibers, ground substance, inorganic components

What kind of protein fibers are found in bone?

elastin, Type I collagen

What type of ground substances are found in bone? What is their purpose?

Glycosaminoglycans (GAGs) —> chondroitin sulfate

Proteoglycans

Adhesive glycoproteins —> osteocalcin, osteonectin, fibronectin

aid in hydrating and adhesion

these are organic components

What type of inorganic components are found in bone? What is their purpose?

Calcium hydroxyapatite (mainly) provides the hard component

How is the inorganic component integrated in bone?

It is “glued” into the organic component via adhesive glycoproteins.

Types of bones.

long

short

flat

irregular

sesamoid

Describe long bone.

length is greater than width

they act as levers that move when muscles contract

example: femur, humerus, phalanges

Describe short bone.

length is roughly equal to the width which is roughly equal to the thickness.

provide stability/support with some motion

example: carpals and tarsals

Describe flat bone.

thin and often curved; point of muscle attachment; protect vital organs

example: culvarium, scapulae, sternum, ribs

in pediatric patients, this is where most red marrow is found. decreases with age.

describe irregular bone.

complex shape that does not fit another classification.

example: vertebrae, mandible, maxilla, ossicles, hyoid

describe sesamoid bone.

round bone that forms in tendons

example: patella - the QT extends over the PT via PL from femur to tibia

What are the two types of tissue in bone?

compact

spongy

What. are the sections of a long bone?

epiphysis - end. contains spongy bone with red marrow

diaphysis - shaft - contains yellow marrow, walls are compact bone

metaphysis

~ physis is the growth plate that is mostly cartilage that calcifies as the child grows. it becomes fixed and calcified. this area helps endocrinologists determine bone age

What are the three layers of a flat bone?

Spongy/trabecular with empty areas called trabeculae

covered by compact bone on either side

Which bone cells work together for bone turnover and remodeling?

Osteoblasts - synthesize bone matrix

Osteoclasts - dissolve bone matrix

What is the function of osteocytes?

Control local calcium and phosphate levels

Responsible for maintenance and nutrition of the bone

Osteoblasts derive from _____.

Pre-osteoblasts/Osteoprogenitor cells

T/F: Osteoblasts divide.

False. Osteoblasts do not divide. They are responsible for synthesizing bone matrix. As they lay down bone, they become trapped and develop into osteocytes within the bone tissue.

T/F: Osteoclasts derive from pre-osteoblast cells/osteoprogenitor cells.

False - osteoclasts derive from unique macrophages known as hematopoietic stem cells that secrete H+ and proteases.

Which bone cell has cytoplasmic projections that extend through caniculi to communicate with one another to determine bone status?

Osteocytes

What is the inner lining of bones, that contains cells that build, repair, and remodel bones throughout life?

Endosteum

What is the outer double-layered membrane covering bones, where the outer layer is _____ connective tissue and the inner layer is _____ (similar in function to endosteum)?

Periosteum

Fibrous

Cellular

T/F: Osteoblasts and osteoclasts are found in the endosteum and periosteum layers.

True

T/F: The endosteum surrounds the yellow marrow on the inner surface of bone.

True

Which bone is dense and strong, and makes up the outer cortex of all bones?

Cortical/Compact bone

Which bone type is a highly organized arrangement of tightly packed osteons?

Cortical/Compact Bone

What is another term for osteons?

Haversian System

The central canal in the center of osteon contains _______, ________, _______.

Blood vessels

Nerves

Lymphatics

The osteons are surrounded by concentric rings, known as ______, of matrix.

Lamellae

Spaces, also known as ______, between adjacent lamellae contain which cell type?

Lacunae

Osteocytes

The bone tissue that is lighter and less dense than compact bone and is soft and flexible is known as ________.

Cancellous/Trabecular/Spongy Bone

Trabecular bone consists of spikes of matrix in a lattice like pattern called ______, with spaces in between.

Trabeculae

What is the benefit of trabeculae being lined by endosteum?

it is easily remodeled

Where is red bone marrow found?

In the spaces between trabeculae

What are the three types of joints?

fibrous

cartilaginous

synovial

Define a joint.

site where two or more bones come together.

How are joints classified?

They are classified according to tissues that lie between the bones

Which joint type is freely movable and why?

Synovial - because the bones are not in direct contact with one another. a joint containing synovial fluid is between them.

Are cartilaginous joints movable?

No to little movement is possible at the level of the individual joint.

What type of cartilage is often found in cartilaginous joints?

Hyaline cartilage

Are fibrous joints movable?

No, they should not move. examples are sutures between skull bones.

The contractile proteins ____ and ______ interact to cause movements.

actin

myosin

What are the striations in cardiac and skeletal muscle?

Myofilaments of actin and myosin

In skeletal muscle, many ________ form long chains of ______, which are hte primary organelles of a single muscle cell.

sarcomeres

myofibrils

Groups of ____ + other organelles form the muscle fiber/cell.

myofibrils

Muscle fiber is covered in ______ (cell membrane).

sarcolemma

Groups of muscle fibers are called _______ and are covered in ________.

fascicles

perimysium - a connective tissue

groups of _____ are wrapped in _____ to form the muscle.

fascicles

epimysium - the connective tissue on top of all fascicles to keep them together and keep the muscle from bursting.

Where is the endomysium found?

in between all muscle fibers

Connective tissues of skeletal muscle fibers merges with ____ to attach to bone.

tendons

Muscle fibers are covered in ______.

Sarcolemma

Which muscle cell structure stores, releases, and retrieves Ca ++?

Sarcoplasmic reticulum - the Smooth endoplasmic reticulum of the muscle cell

What is the functional unit of a myofibril?

sarcomere

How are sarcomeres arranged?

Highly organized arrangement of myofilaments (actin and myosin)

T/F: Sarcomeres are the smallest functional unit of a skeletal muscle cell.

True

T/F: The A band of the sarcomere is the portion that creates the stiration appearance.

True

Which is the thick band and which is the thin band: actin/myosin.

thick - myosin

thin - actin

What components are responsible for the contractile properties of the muscle cells?

Actin

Myosin

T/F: Contraction shortens the sarcomere and the fibers.

False - contraction shortens the sarcomere but the fibers only move.

_______ maintain their length by sliding past each other, which causes ______ to shorten.

Myofilaments

Myofibrils