Chapter 7 skeletal system

Muscle fibers generally only have one motor end plate, but motor neurons innervate many different muscle fibers in a group. Choose the statement that correctly explains how this affects muscle contraction.

A signal traveling through one motor neuron can potentially make multiple fibers in a group contract, generating more force.

Which disorder is characterized by enlarged hands, feet, and jaw and is caused by excess growth hormone secretion in adulthood

Acromegaly

Which statement describes the mechanism of muscle contraction?

Actin filaments slide along myosin filaments.

After bones have formed via intramembranous or endochondral ossification, what happens to the bone?

Bone is continually remodeled by osteoclasts and osteoblasts.

There are 2 major glands that play a role in bone homeostasis. Thyroid glands secrete ___, while parathyroid glands secrete

Calcitonin which works with osteoblasts; PTH which works osteoclasts

During the process of endochondral ossification a primary ossification center appears in the

Diaphysis

Why are athletes typically able to exercise longer before developing muscle fatigue than non-athletes?

Due to training, athletes have a better blood supply and more mitochondria in their muscles than do non-athletes.

A band of cartilage that allows for the growth in length of an endochondral bone is called

Epiphyseal plate

The term ossification refers to

Formation of bone

How do intramembranous bones form?

From sheetlike layers of unspecialized connective tissue

process of healing a fracture

Hematoma formation, fibrocartilage formation, bony callus formation, bone remodeling by osteoclasts

Endochondral bones are formed from models made of

Hyaline cartilage

Endochondral bones develop from what masses of what tissue

Hyaline cartilage

Which of the following is not a step in endochondral bone formation

Hyaline cartilage changes to adipose tissue.

Endochondral ossification in order

Hyaline cartilage model forms, cartilage tissue breaks down, osteoblasts form spongy and compartment bone, osteoblasts become osteocytes

What is the process by which a bone grows in length

Increased activity within the epiphyseal plate

Bones that develop with sheets of connective tissue are called

Intramembranous bones

Flat bones in the skull develop through a process called

Intramembranous ossification

The process of bone formation from membrane like layers of connective tissue is called

Intramembranous ossification

The process of bone formation from membrane like layers of connective tissues is called

Intramembranous ossification

Which of the following does not describe the functions of the skeletal system

It generates the movements of the limbs.

Indicate the statements that are true about intramembranous ossification

It occurs between flat sheets of CT, and skull bones are formed via intramembranous ossification

What happens when the epiphyseal plate is ossified?

Lengthening of the bone is no longer possible.

How long does a bone grow in width?

Osteoblasts deposit new bone under the periosteum of the diaphysis

Cells that are responsible for the breakdown of the calcified extracellular matrix in bone

Osteoclasts

When osteoblasts completely surround themselves with the extracellular matrix, they become cells callled

Osteocytes

Glands that secrete hormones that affect bone growth and development

Pituitary, thyroid, parathyroid

What is the function of osteoblasts

Production of bone

Regions of the epiphyses, where cartilage slowly breaks down and spongy bone form in all directions called

Secondary ossification

How does the integumentary system interact with the skeletal system

The integumentary system functions in the activation of vitamin D.

Certain natural plant poisons and animal venoms contain substances that inhibit the function of acetylcholinesterase. If a person is poisoned by one of these substances, which of the following will be the cause of their symptoms?

Their muscles won't be able to contract because acetylcholine will be attacked and degraded immediately after release from the neuron.

What roles do sex hormones play in bone growth?

They stimulate closure of the epiphyseal plate and therefore stop long bone growth. They stimulate growth at the epiphyseal plate and therefore long bone growth.

Hormone that stimulates osteoblasts at the epiphyseal plate?

Thyroxine

What is the action of the thyroid hormone thyroxine on the skeletal system

To stimulate replacement of cartilage with bone in the epiphyseal plate.

What is the role of Vitamin D bone development?

Vitamin D increases calcium absorption in the small intestine and thus helps maintain the calcium concentrations necessary to build the bone matrix

In order to break down bone osteoclasts secrete ___ to dissolve the inorganic components of calcified bone matrix and use their ___ to digest the organic components

acid and lysosomal enzymes

The ___ secretes___, which promotes Na+ and water retention

adrenal cortex; aldosterone

A bone thickens

as compact bone is deposited beneath the periosteum of the diaphysis.

What are fascicles?

bundles of muscle fibers

As endochondral ossification begins, where does bone tissue first begin to replace hyaline cartilage?

center of diaphysis

With a(n) ___ fracture, the skin remains intact. With a(n) ___ fracture, the skin is damaged and the bone is exposed with an increased risk of infection

closed, open

Although about 90% of the protein found in bone is ___ other proteins exist in bone, such as __

collagen and osteocalcin

Bones that develop from masses of hyaline cartilage are called

endochondral bones

most bones of the body are

endochondral bones

Growth hormone stimulates cell division at the

epiphyseal plate

What is the name of the structure located between the primary and secondary ossification centers?

epiphyseal plate

Secondary ossification centers appear in the

epiphyses

The hormone ___ has a stronger effect than ___ on the epiphyseal plate, causing it to close more quickly. This explains the discrepancy in height between male and female adults

estrogen and testosterone

The clinical term for a broken bone is

fracture

Excess growth hormone in childhood causes

gigantism

Which hormone stimulates growth at the epiphyseal plate?

growth hormone

What helps control the opposing processes of resorption and deposition of the bone matrix?

hormones

Which is a factor that directly influences bone development, growth, and repair

hormones

Endochondral bones develop from masses of what tissue?

hyaline cartilage

In endochondral ossification, as masses of ___ cartilage breaks down, ___ deposit bone in spaces created

hyaline; osteoblasts

Osteoclasts secrete acid to dissolve the ___ components of bone and use lysosomal enzymes to digest the ___ components of bone

inorganic and organic

Flat bones, such as bones of the skull, that develop from sheetlike layers of connective tissue, are called ______.

intramembranous bones

During strenuous exercise, when muscles are not being supplied with enough oxygen, a shift in metabolism results in the breakdown of pyruvic acid to lactic acid. What is this change in metabolism called?

lactic acid threshold

Which of the statements following accurately describes osteoblasts?

mesenchymal cells that have differentiated into bone-forming cells

The formation of bone is called

ossification

Cells that deposit and form new bone during osteogenesis are called

osteoblasts

Which of the following bone cells would have the greatest number of lysosomes?

osteoclasts

3 proteins found in bone

osteonectin, osteocalcin, collagen

A disorder of the bones that is similar to osteoporosis, only milder, is ______.

osteopenia

Which hormone stimulates osteoclast activity

parathyroid hormone

intramembranous ossification

process by which bone forms directly from mesenchymal tissue

endochondral ossification

process in which bone forms by replacing hyaline cartilage

Red bone marrow functions in the formation of

red blood cells, white blood cells, platelets

The total mass of bone tissue in a healthy adult skeleton

remains nearly constant

In skeletal muscle fibers, what is the source of the calcium ions that are released into the sarcoplasm to bind with troponin, resulting in contraction?

sarcoplasmic reticulum

During endochondral ossification in the epiphyses, a ___ ossification center forms, and ___ bone is formed in all directions from this location

secondary; spongy

In a closed bone fracture, the ___ is unbroken. In a compound fracture, it is broken

skin

What are examples of bones that form through intramembranous ossification?

sternum mandible (jaw bone) flat bones of the skull

What is the function of creatine phosphate?

supplies energy for the synthesis of ATP

In order for a long bone to grow width (thickness), new bone is deposited ____ while the bone is eroded ____

under the periosteum; in the medullary cavity

UV radiation striking skin is a step in activating ____, which then plays a role in absorption and availability of ___ for use in forming the bone matrix

vitamin D and calcium

At what age are nearly all bones completely ossified?

25 years old

How many distinct layers form an epiphyseal plate?

4 layers

Vitamin __ is necessary for osteoblast activity and vitamin __ is necessary for collagen synthesis

A and C